The Life of a Storm

The timeline begins at the bottom of the page. Most recent observations will be added to the top of the page. The forecast post is linked here http://mdtropics.blogspot.com/2016/01/jan-22-23-storm-thread.html

January 23 2016:

12:00AM

The storm is really getting going now. Don;t know if the returns south of us is sleet , snow, or a mix. But whatever it is, it's very very heavy. Lightning has been detected in Richmond in that blob so thundersnow here we go!

January 22 2016:

9:00 AM

Snow is making its way into Richmond. The storm has really grown in size overnight. Looking good

12:00AM

The storm is really ramping up now. Classic snowstorm look.

January 21 2016: 

 6:00PM

 Radar is lighting up across the southeastern US as the developing storm strengthens and taps into tgropical moisture from the gulf and beyond.

Energy from the Pacific storm has spawned a new low in Texas. This low will become the primary low that gives us the front end thump. The Surface low is located in the white mass of moisture (thunderstorms) the swirl behind the sfc low is the upper level low.

January 19th, 2015: 
This little storm crashed into the coast.

Jan 22-23 Storm

Jan 22 2016 9:00AM Update
 Storm is coming. It's go-time. Storm evolution has not changed much: around 2 feet of snow will fall. Snow may come in a little earlier, like 1 or 2PM. Also, they did mention the chance of a dry-slot impacting us, cutting down on totals a bit. But we gotta live on the edge if we want to have a chance at jackpotting. Basically, people just to the west of the dry-slot will jackpot. Thundersnow is also possible. It's gonna be fun

Jan 22 2016 1:15 AM Update
On the most important Euro run of the year, it "s**ts the bed". The Euro got stuck at 12 hrs into the run. No graphics, only text outputs with missing data. Well I guess we can toss that run. 2+ feet of snow it is then.

CMWF Deterministic FORECAST FOR: DCA LAT= 38.85 LON= -77.03 ELE= 16

00Z JAN22
2 M 850 SFC SFC 700 6 HR 500 1000
TMP TMP PRS RHU RHU QPF HGT 500
© © (MB) (PCT) (PCT) (IN) (DM) THK
FRI 00Z 22-JAN -2.3 -7.7 1027 51 16 553 532
FRI 06Z 22-JAN -3.6 -7.1 1027 52 17 0.00 554 533
FRI 12Z 22-JAN -3.6 -6.2 1027 54 33 0.00 555 535
FRI 18Z 22-JAN ___ ___ ____ __ __ ____ ___ ___
SAT 00Z 23-JAN -4.0 -6.6 1019 86 99 ____ 551 536
SAT 06Z 23-JAN -3.8 -3.9 1010 87 100 0.52 546 539
SAT 12Z 23-JAN -3.4 -5.1 1002 82 94 0.71 538 536
SAT 18Z 23-JAN -3.3 -5.9 1003 81 71 0.18 536 534
SUN 00Z 24-JAN -2.6 -7.0 1009 80 98 0.23 537 530
SUN 06Z 24-JAN -3.4 -5.1 1013 69 81 0.05 543 533

Jan 22, 2016 12:00AM Update:
I have a post to track the storm and it's progress. ths page will be used to post the forecast/nowcast.
http://mdtropics.blogspot.com/2016/01/the-life-of-storm.html

Jan 21 2016 11:00PM Update
The NWS increased snow totals and wind. 24-30" of snow, and sustained winds of 25-35mph  with gusts up to 55. This is no longer a "fun" storm. This  is an life threatening and historic event.

On the more interesting the most recent models have gone absolutely bonkers on the snowfall predictions tonight.

First up was the 4K hires NAM, which jackpotted western VA and northern MD with 30"+.  This run was initially discounted due to its anomalously high precip amounts (a very NAM thing to do) The running joke is to take the NAM output and divide by 2 to get the actual result. Not true either, but the NAM does have a wet bias.

Then the RGEM (Canadian hires short term model). It has historically done pretty good forecasting mesoscale structures during winter storms. It sets up the deform band directly over DC, crushing us with upwards of 40" of snow, with a couple inches still to come. The main thing is that the low positions were very realistic-off the coast of Ocean city, that it is a hi-res model that is able to resolve mesoscale banding better than the global models like the GFS, and the fact that it has done well for the past few winters. The totals are just unrealistically high.

Then came the GFS, global model, with lower resolution. Imagine the surprise when it also dropped upwards of 36" across the DC area, similar to the RGEM. Holy smokes. The solution would probably have been immediately thrown out if RGEM didn't have the solution it has. The GFS probably are overdoing convective banding. The high totals may be more isolated, but the fact that the RGEM has it too gives one pause.

We shall see soon. Waiting on the Euro to either seal the deal, or break it.

Jan 21 2016 12:41 PM Update
We are in the home stretch. Our storm is forming in the gulf coast states and the models are locked in on around 2 feet of snow for the region. The NWS has gone ahead an upgraded the watches to warnings as well as increasing snowfall forecasts.We are under a blizzard warning from Friday 3PM through the Saturday night. If you haven't finished preparing, please do so today.

Orange is the blizzard warning

.BLIZZARD WARNING IN EFFECT FROM 3 PM FRIDAY TO 6 AM EST
SUNDAY...

THE NATIONAL WEATHER SERVICE IN BALTIMORE MD/WASHINGTON HAS
ISSUED A BLIZZARD WARNING...WHICH IS IN EFFECT FROM 3 PM FRIDAY
TO 6 AM EST SUNDAY. THE BLIZZARD WATCH IS NO LONGER IN EFFECT.

* HAZARD TYPES...HEAVY SNOW AND WIND WITH BLOWING AND DRIFTING
  SNOW FRIDAY AFTERNOON THROUGH SATURDAY NIGHT. SLEET MAY MIX WITH
  THE SNOW FRIDAY NIGHT INTO SATURDAY MORNING EAST OF INTERSTATE
  95 BEFORE CHANGING BACK TO ALL SNOW BY SATURDAY AFTERNOON.

* ACCUMULATIONS...SNOW ACCUMULATION OF 18 TO 24 INCHES IN THE
  EASTERN SUBURBS OF WASHINGTON DC...AND 24 TO 30 INCHES IN THE
  WESTERN SUBURBS. THE CITY OF WASHINGTON DC IS EXPECTED TO
  RECEIVE AROUND 24 INCHES.

* TIMING...HEAVY SNOW WILL DEVELOP LATE FRIDAY AFTERNOON AND
  CONTINUE THROUGH SATURDAY NIGHT. CONDITIONS ARE EXPECTED TO
  DETERIORATE FRIDAY AFTERNOON WITH THE HEAVIEST SNOW...STRONGEST
  WINDS...AND POTENTIAL LIFE THREATENING CONDITIONS EXPECTED
  FRIDAY NIGHT THROUGH SATURDAY.

* IMPACTS...HEAVY SNOW AND BLOWING SNOW WILL CAUSE DANGEROUS
  CONDITIONS AND WILL BE A THREAT TO LIFE AND PROPERTY. TRAVEL
  IS EXPECTED TO BE SEVERELY LIMITED IF NOT IMPOSSIBLE DURING
  THE HEIGHT OF THE STORM FRIDAY NIGHT AND SATURDAY. VISIBILITY
  WILL BE REDUCED TO NEAR ZERO AT TIMES IN WHITEOUT CONDITIONS.

* WINDS...NORTHEAST 25 TO 35 MPH WITH GUSTS UP TO 50
  MPH...BECOMING NORTH SATURDAY.

* TEMPERATURES...MID TO UPPER 20S.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A BLIZZARD WARNING MEANS SEVERE WINTER WEATHER CONDITIONS ARE
EXPECTED OR OCCURRING. FALLING AND BLOWING SNOW WITH STRONG WINDS
AND POOR VISIBILITIES ARE LIKELY. THIS WILL LEAD TO WHITEOUT
CONDITIONS...MAKING TRAVEL EXTREMELY DANGEROUS. DO NOT TRAVEL. IF
YOU MUST TRAVEL...HAVE A WINTER SURVIVAL KIT WITH YOU. IF YOU GET
STRANDED...STAY WITH YOUR VEHICLE. PREPARE FOR THE POSSIBILITY OF
POWER OUTAGES DURING SNOWY AND COLD CONDITIONS.

Jan 20 2016 10:30 PM Update
Sorry about the delay. Went out with family for groceries, got stuck in the surprise clipper snow. Probably a Two Hour Delay tomorrow. Perhaps even a day off, seeing that the beltway is jammed from US 29 (Blair) all the way to the VA State Line (American Legion bridge). Anyway, appetizer done and onto the main course.

Precipitation Timing
An upper level low/trough will strengthen rapidly as it approaches the east coast, digging south and slowing down in forward motion. It will also spawn a surface low in northern Louisiana, which will track into Tennessee. Warm, moist, air aloft will supply the front end dump of snow.

Snow should begin Friday afternoon, around 3PM. Thus, an early release for the Middle and elementary schoolers would be needed (Makeup Exam Day of High Schoolers). Maybe the county will give us the day off to prepare for the impending storm. Initially, snowfall rates will be light to moderate through the evening. After 7-8PM, snowfall rates will pick up to as high as 2"/hr or higher as the front end thump comes through.

The primary low will then dissipate and the warm air advection supplying moisture for the front end thump will shut off. A coastal low will develop near the SC/NC border before tracking NNE. As this storm gets going (hopefully bombing out), and the upper level low strengthens and almost stalls, a deformation band will set up west of the storm. depending on the exact track of the surface low, there may be a period when we mix to sleet, freezing rain, or even plain rain. However, the thinking at the moment is that we remain as snow throughout the storm. The exact location has yet to be determined; it will probably shift throughout the storm. However, where this band sets up the longest will be where the highest totals will be. snowfall rates could possibly exceed 3-4"/hr at times.

Snowfall rates will wane Saturday evening  as the storm pulls away. Flurries could hang around until Sunday morning. The storm should last between 30-40 hours.

Both parts of the storm will be very dynamic, due to the strength of the upper level low supplying intense areas of lift (rapidly raising air in the atmosphere). Thus, the snowfall rates will be amazingly high. To put this event into perspective, snow is considered heavy when it falls at a rate >1"/hr. There is potential for people to see quadruple that rate. However, not everyone will cash in since where one area has high rates of lift, other areas will have subsidence, resulting in distinct, possibly slow moving bands. In the higher bands, lightning is possible. This will likely be a historic and memorable storm for the DC area.

Preciptation Amounts
This storm will be laden with Gulf moisture carried by the Nino enhanced subtropical jet. Models are in good agreement with liquid equivalent amounts across the region around 2 inches, meaning that widespread snow totals of 18-22 inches will be expected, with some areas getting more where banding sets up. Snow totals will likely be higher in the traditionally favored spots N and W of the city proper.

We can expect the front end to bring us 10-14" of the final total. The rest will likely depend on the deform band. Get lucky? You get a ban to sit over you for a few hours and dump a foot or more. 10 miles away from this band? You could get light/moderate snow for a few hours. Isolated totals as much as 30 inches and as low as 16 will be possible.

Winds
We have a blizzard watch up for the immediate DC area for sustained winds of 20-30 mph and gusts to 40-50mph. The closer to the bay you get, the higher the impact the winds have. Winds will increase Saturday as the coastal storm strengthens, causing blowing and drifting, which will impede snow removal. Plows may be called off the roads at the height of the storm. Whiteout conditions are possible at times.The high winds may also result in power outages.

Jan 20 2016 10:30AM Update
The NWS went ahead with a Blizzard Watch. Time to prepare yourselves.

DCZ001-MDZ004>006-011-013-014-016>018-503>508-VAZ052>057-505-506-
202315-
/O.NEW.KLWX.BZ.A.0001.160122T1700Z-160124T1100Z/
DISTRICT OF COLUMBIA-FREDERICK MD-CARROLL-NORTHERN BALTIMORE-
SOUTHERN BALTIMORE-PRINCE GEORGES-ANNE ARUNDEL-CHARLES-ST. MARYS-
CALVERT-NORTHWEST MONTGOMERY-CENTRAL AND SOUTHEAST MONTGOMERY-
NORTHWEST HOWARD-CENTRAL AND SOUTHEAST HOWARD-NORTHWEST HARFORD-
SOUTHEAST HARFORD-PRINCE WILLIAM/MANASSAS/MANASSAS PARK-FAIRFAX-
ARLINGTON/FALLS CHURCH/ALEXANDRIA-STAFFORD-SPOTSYLVANIA-
KING GEORGE-WESTERN LOUDOUN-EASTERN LOUDOUN-
1013 AM EST WED JAN 20 2016

...BLIZZARD WATCH IN EFFECT FROM FRIDAY AFTERNOON THROUGH LATE
SATURDAY NIGHT...

THE NATIONAL WEATHER SERVICE IN BALTIMORE MD/WASHINGTON HAS
ISSUED A BLIZZARD WATCH...WHICH IS IN EFFECT FROM FRIDAY
AFTERNOON THROUGH LATE SATURDAY NIGHT.

* HAZARD TYPES...HEAVY SNOW AND WIND. A WINTRY MIX IS POSSIBLE
FRIDAY NIGHT INTO SATURDAY MORNING EAST OF INTERSTATE
95...BEFORE CHANGING BACK TO ALL SNOW ON SATURDAY.

* ACCUMULATIONS...POTENTIAL FOR A FOOT OR MORE OF SNOW.

* TIMING...FRIDAY AFTERNOON THROUGH SATURDAY NIGHT. CONDITIONS ARE
EXPECTED TO DETERIORATE FRIDAY AFTERNOON WITH THE HEAVIEST
SNOW...STRONGEST WINDS...AND POTENTIAL LIFE THREATENING CONDITIONS
EXPECTED FRIDAY NIGHT THROUGH SATURDAY NIGHT.

* IMPACTS...HEAVY SNOW AND BLOWING SNOW WILL CAUSE DANGEROUS
CONDITIONS AND WILL BE A THREAT TO LIFE AND PROPERTY. TRAVEL IS
EXPECTED TO BE SEVERELY LIMITED IF NOT IMPOSSIBLE DURING THE
HEIGHT OF THE STORM FRIDAY NIGHT AND SATURDAY. VISIBILITY WILL
BE REDUCED TO NEAR ZERO AT TIMES IN WHITEOUT CONDITIONS.

* WINDS...NORTHEAST 10 TO 15 MPH FRIDAY. NORTHEAST WINDS WILL
INCREASE TO 20 TO 30 MPH WITH GUSTS TO 40 MPH FRIDAY
NIGHT...THEN SHIFT NORTH SATURDAY THROUGH SATURDAY NIGHT.

* TEMPERATURES...MID TO UPPER 20S MOST LOCATIONS. UPPER 20S TO
LOWER 30S ACROSS SOUTHERN MARYLAND.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

USE THIS ADVANCE NOTICE TO PLAN AHEAD! ADJUST TRAVEL PLANS...AND
PLANNED ACTIVITIES. STOCK UP ON NECESSITIES. MAKE PLANS FOR
ELDERLY FAMILY AND THOSE MOST AT RISK. PREPARE FOR THE POSSIBILITY OF
POWER OUTAGES DURING SNOWY AND COLD CONDITIONS. USE THIS TIME TO
MINIMIZE IMPACT ON YOU...YOUR FAMILY...AND YOUR COMMUNITY.

&&

$


Jan 20 2016 9:00 AM Update
There will be two phases of the storm, the front end thump, and the coastal low. The front end thump is now in the range of some short range model forecasts and thus, there is higher confidence in that part of the forecast.Snow totals look to total around 10-14 inches if not more before precip shuts off for a bit as the coastal low takes over.

The coastal low is forecast to form in about 4 days and is more tricky. The track still shifts run to run but it seems that we are going to get slammed by the backside of the storm. The speed and direction at which the low moves will determine how much we get on the backside. Winds will increase as the coastal low strengthens, causing blowing and drifting.

Storm totals can be expected around 2 feet of snow, with a slight possibility of up to 3 feet in traditionally favored spots north and west of DC. This will be a storm to be remembered.  The NWS mentioned that it will likely begin issuing watches around noon today.

Jan 20 2016 2:00AM Update
The Euro came out. Sort of a funky solution; it transfers the low much more south and rides it up the coast but the snow... The snow... It's amazing. The deform band absolutely clobbers us. Onset would be later than the GFS by 6 hours, later afternoon and the storm lasts until Sunday morning. We will look ahead to the next model runs in the morning.

Jan 20 2016 1:00AM Update
 The WPC threw out the 12Z Euro's southern solution in favor of the 18z GFS and 12z Euro Ensembles, which is similar the GFS ensembles.

IN FACT...THE ECMWF IS
SO FAR FROM ITS OWN ENSEMBLE MEAN AND THE DETERMINISTIC CONSENSUS
IN 4 DISTINCT AREAS BEGINNING SATURDAY THAT IT WAS NOT USED AT ALL
IN THE BLENDING PROCESS. INSTEAD...ABOUT 40 PERCENT OF THE 18Z GFS
WAS BLENDED WITH ABOUT 30 PERCENT EACH 18Z GEFS MEAN/12Z ECMWF
ENSEMBLE MEAN. 

That being said, the most recent model runs (0z) have come in further south-ish, at least in the beginning. The Euro is running now so we shall see if this is a trend or not.

Original Text
We're officially in the medium range. A Major East Coast Snowstorm (MECS) is set to impact the area Friday through Saturday. For 3 days out, there is remarkable agreement between models and their ensembles and between models. However, there are still some differences between models and run to run. Most of the differences are minor but there are just a few that are enough to give pause. The main conflict seems to be the difference between the GFS and the ECMWF models.
 
Tl;DR First: The GFS and the Euro have differences that need to be resolved. The GFS basically sets the jackpot over the DC area while the Euro goes south. No temperature issues this run. Kocin the snow lord is  on board for a MECS. All is going well. Have a look at NWS Friday-Sat Night forecast

Setup:
The GFS and the Euro and all the other models generally agree low tracks through the next 2.5 days, down the Inter-mountain West into NE Texas. The GFS is perhaps slightly faster but there isn't much difference. But when the storm approaches the region on Friday, the forecast diverges.

12z GFS vs Euro 7AM Friday Morning. Look at the center of the black-lined circles. Not a lot of difference

Basically, the GFS is 50-100 miles north with the surface low and around 100 miles north with the upper level low.  This sends the primary low into Tennessee and brings a heavy front end thump of snow, beginning in the morning. The Euro, on the other hand keeps the lows (sfc and UL) weaker, keeping it further south, which means that we don't get the front end thump. Precip doesn't start until late afternoon.

GFS and Euro hr 96, The coastal transfer is taking place. Notice how the center of the Euro low is 100-150 miles to the south of the GFS low.

 Since the Euro starts off farther south with the primary, the coastal is also farther south. Basically, after the transfer, the Euro is identical to the GFS. It just has the precip max farther south, leaving us on the north edge. The storms bombs off the coast. While the storm bombs, the area to the WNW will get the heaviest snows so the south shift on the Euro shifts precip south.

GFS and Euro @120 hrs (5 days) The storm is going out to sea and the GFS is still noticeably north.

Snowfall Amounts:
The CIPS analog mean snowfall gives us at least 12 inches. How the CIPS works is it compares to forecast scenario of the GFS to historical setups. It takes the snowfalls that resulted from the top 15 matches (analogs) and averages them. Therefore, it is reasonable to think that 12 inches of snow is likely, if not more. This would put us firmly into MECS amounts.

CIPS Analog  centered around hour 96

Raw GFS and Euro outputs give us around 2" of liquid equivalent precipitation. Snow ratios will vary depending on conditions in the snow growth area aloft. Surface temperatures will remain below freezing for the duration of the event. The question is whether upper level temperatures will remain below freezing. It looks like a crippling hit. Also, look at who made the forecast...

The48 hr precip forecast jackpots our area.

Updates will come as information flows through. The previous post is linked below, as well as the model post, which may not be as far fetched as thought. It may do you well to prepare for a long duration storm, i.e. getting supplies, batteries, flash lights, maybe a snow blower. Also, keep reading and pay attention to the National Weather Service. With a bombing low, many interesting things can happen. Watches could be issued as early as tomorrow.

LWX NWS page
http://www.weather.gov/lwx/
Previous post
http://mdtropics.blogspot.com/2016/01/finals-week-and-jan-22-24-possible-storm.html
Models Post
http://mdtropics.blogspot.com/2016/01/jan-22-24-model-page.html

Jan 22-24 Model Page

People who view the contents of this post may experience strong emotions such as but not limited to: euphoria, happiness, giddiness, loss, despair, anger, and sadness. This is a page on model guidance; THIS IS NOT A FORECAST. This page is intended to be entertainment, NOT A FORECAST. Please do not spread the following images in any way without including this disclaimer. Please be aware that the following model outputs are for guidance only and are at range. They will not be accurate. READ AT YOUR OWN RISK

So without further ado, let's begin the march of the clown maps.

018Z Jan 19 2016 Cycle: 

NAM
Gives us 16-18" of a front end dump before mixing issues due to an amped up storm-something the NAM is well known for doing. It's also not supposed to be used beyond 3 days (72hrs). Precip doesn't start until 72 hrs.

DGEX
AKA the NAM continued, is only useful for clown maps.

GFS
This run is honest;y a relief. The 12 Euro moved the storm south, leaving us on the northern edge of the storm. We were previously on the southern edge. The GFS has been remarkably consistent with bullseyeing the region and decided to keep doing that this run. It also sets up an deformation zone on the backside that dumps a lot of snow. Good run.

GEFS
Well it dropped south, but that puts us in the bullseye. Around 2 feet on the means. Min snow amount for DC is 6 inches. Maximum amounts are obscene. All I can say is that it'd be a pain to shovel.

12Z Jan 19 2016 Cycle:
GEFS
All big hits except for 3 that miss us to our south

GEFS Mean
21-24 inch mean. Enough said.

EPS Mean


06Z Jan 19 2016 Cycle: 
NAM
We are finally in range of the mesoscale models. It's not going to be accurate at all at this point, but it's a milestone we have not reached all winter. All our previous storms died before d7 or so.

 GFS
Fails to capture the upper level low resulting in a less amped storm. "Only" 20-25 inches,at least half of which is from the front end thump.
GEFS

GEFS Mean
 16-20 inches of snow across the whole area
 
00Z Jan 19 2016 Cycle:
GFS
Central MD Jackpot. Widespread 30"+

GEFS

GEM
 20-30 inches of cold snow. No changeover
GEPS
16-18" of snow

ECMWF
Insane amounts of snow west. Probably not gonna verify, but fun to look at

18Z Jan 17 2016 Cycle:
DGEX
This is basically an extension of the NAM model which is a short range hi res mesoscale model. That should give you an idea on how right this map is.  It actually suppresses the storm to the south. Also drops an absolutely ridiculous amount of precip/snow.

Clownmap Score: 9/10 
Point taken off for not bulls-eyeing DC.
Points for showing an insane amount of precip, being the southernmost solution, screwing over the Northeast, and being the DGEX

GFS
American Model. Bullseyes DC with 21.8 inches of snow, well actually, bullseyes Fairfax City with 24+ inches.

Clownmap score: 9/10
Point taken off for outputting snowfall amounts that are even possible
Points for showing a bombing out low, DC bullseye, and a closed upper level low with extreme snowfall rates.

GEFS
 


12Z Jan 17 2016 Cycle:
GFS

GEFS

ECMWF

EPS

CMC

GEPS

UKMET

Finals Week and Jan 22-24 Possible Storm

Jan 19 6:30 PM Update:
The European Model shifted south with the low.  Otherwise, non of the other models have changed much. The GFS still jackpots Central MD and Northern VA. Basically nothing has changed since the last update. A major snowstorm is still likely. We're waiting for the lead time to shorten and our storm to begin its trek across the US so we can parse out where the best dynamics for snow growth and banding will occur.

This morning, Paul Kocin wrote up the extended forecast for the HPC. Him and Louis Uccellini conducted research on NE snowstorms and created the NE Snowfall Impact Scale and thus is very well regarded as an expert on snowstorms. He wrote some very nice things as well as some things to watch:

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1100 AM EST TUE JAN 19 2016

VALID 12Z FRI JAN 22 2016 - 12Z TUE JAN 26 2016

HIGHLIGHTS...

LETS CUT TO THE CHASE. THE MAIN EVENT IN THE MEDIUM RANGE IS THE
POTENTIAL FOR A SIGNIFICANT EAST COAST SNOWSTORM FROM FRIDAY
THROUGH SUNDAY/DAYS 3 TO 5.  THERE HAS BEEN AND CONTINUES TO BE
RELATIVELY GOOD AGREEMENT ESPECIALLY BETWEEN THE MODEL ENSEMBLES.
COMPARING THE OPERATIONAL RUNS TO THE ENSEMBLE MEANS DOES INDICATE
SOME DIFFERENCES THAT ARE SMALL IN THE LARGE SCALE BUT CRUCIAL TO
THE FORECAST.  ALL MODELS SUGGEST THAT MAJOR DEVELOPMENT FOR THIS
SYSTEM WILL OCCUR AS IT MOVES TO THE MID ATLANTIC COAST AND THEN
THE SYSTEM OCCLUDES...BECOMES MORE VERTICAL AND THEN CONTINUES
NORTHEASTWARD WITH THE MOVEMENT OF THE UPPER TROUGH.  WITH THAT IN
MIND...THE STORM WILL LIKELY SLOW IN ITS FORWARD MOVEMENT AS IT
MOVES OFF THE MID ATLANTIC COAST AND THEN WILL LIKELY ACCELERATE
NORTHEASTWARD OR ANOTHER TRIPLE POINT LOW MAY DEVELOP FARTHER
NORTH AND EAST. THE 00Z ECMWF SUGGESTS BOTH SCENARIOS.  IN EITHER
EVEN...THE OVERALL SPEED OF THE SYSTEM IS IMPORTANT TO AFFECT THE
AMOUNT OF SNOW IN ANY ONE AREA.  THIS WILL BE AN IMPORTANT TREND
TO FOLLOW AS THE MORNING MODEL SOLUTIONS START COMING IN.

IN ADDITION...ANY TRENDS EITHER NORTH OR SOUTH WILL IMPACT
SNOWFALL AMOUNTS ALONG THE NORTHERN EDGE OF THE HEAVIEST SNOW AS
WELL AS THE ISSUES OF MIXING/CHANGEOVER ALONG THE SOUTHERN EDGE OF
THE SYSTEM.  THERE HAVE BEEN SUBTLE NORTH/SOUTH SHIFTS WITH THIS
FORECAST BUT WILL HAVE TO BE ASSESSED WHEN THE MORNING MODELS
ARRIVE. THERE HAVEN'T BEEN LARGE CHANGES WITH THE OVERNIGHT CYCLE.

IN GENERAL...THE OPERATIONAL GFS RUNS ARE SLIGHTLY MORE
PROGRESSIVE THAN THE OPERATIONAL ECMWF RUNS. IN PARTICULAR THE 06Z
GFS TRENDED FASTER THAN PREVIOUS RUNS RESULTING IN LOWER SNOWFALL
AMOUNTS DUE TO LOWER SNOWFALL DURATION. THE 00Z UKMET IS SIMILAR
TO THE ECMWF AND TO SOME EXTENT THE GFS BUT THE 00Z CANADIAN WAS
MUCH MORE PROGESSIVE THAN ANY OTHER MODEL AS WELL AS THE CANADIAN
ENSEMBLES.  AS A RESULT...LATER IN THE FORECAST...THE NAEFS MEAN
IS FASTER THAN THE GFS MEAN DUE TO THE CONTRIBUTION OF THE
CANADIAN SOLUTIONS.   AT THIS TIME...THE HIGHEST PROBABILITIES FOR
THE HEAVIEST SNOW BETWEEN THE ISSUES WITH THE NORTHERN EDGE AND
THE SOUTHERN MIX/CHANGEOVER IS CURRENTLY SUGGESTED TO RUN FROM
NORTHERN VIRGINIA TO EASTERN PENNSYLVANIA/NEW JERSEY INTO SOUTHERN
NEW ENGLAND.

TO PUT THIS SYSTEM IN CONTEXT...THE POTENTIAL SNOWFALL
DISTRIBUTION HAS SIMILARITIES TO SEVERAL MAJOR EAST COAST STORMS
IN RECENT PAST INCLUDING THE 5-6 FEBRUARY 2010 SNOWSTORM/THE
JANUARY 1996 BLIZZARD OF 1996 AND THE PRESIDENTS DAY OF FEBRUARY
2003. JANUARY 1996 IS LIKELY TO BE MORE WIDESPREAD/HEAVY BUT ONLY
TIME WILL TELL. THE MECHANISMS COMING TOGETHER FOR A MAJOR
SNOWFALL ARE TEXTBOOK.

IN THE WEST...PRECIPITATION SHOULD WANE ALONG THE COAST DAY 3 INTO
DAY 4...WITH THE NEXT MAJOR PRECIPITATION EVENT EXPECTED ACROSS
THE PACIFIC NORTHWEST BY NEXT MONDAY OR TUESDAY...WITH SEVERAL
INCHES OF LIQUID EQUIVALENT EXPECTED.

CONFIDENCE...

THIS IS A HIGH CONFIDENCE EVENT THIS FAR OUT IN ADVANCE BUT THAT
ALSO SUGGEST THAT SMALL CHANGES CAN HAVE SIGNIFICANT CHANGES TO
IMPACT. THERE IS STILL 3 TO 4 DAYS FROM THE EVENT AND MANY MODEL
SOLUTIONS TO COME.  THERE HAS BEEN EXCELLENT CONTINUITY RELATIVE
TO AVERAGE AND PERHAPS SIMILAR TO WHAT WAS OBSERVED WITH THE
FORECASTS PRIOR TO 5-6 FEBRUARY 2003...WHICH WAS FORECAST AS MUCH
AS 8 DAYS IN ADVANCE.  OTHER STORMS HAVE BEEN MUCH LESS
PREDICTABLE.  THIS MAY BE ONE CASE WITH A HIGH DEGREE OF
PREDICTABILITY BUT WE SHALL SEE.

KOCIN

Jan 19 2016 10:00AM Update
The shortwave that becomes our storm is coming ashore in the pacific northwest. We are rounding curve into the home stretch. Models still have not wavered from bringing heavy snow to the region. If anything, the 00z Euro upped the ante once again, bringing widespread totals of over 3 feet west of DC. The GFS and the Canadian have more "realistic" snow totals, between 20 and 30 inches.

The Weather Prediction Center (WPC) places the rapidly deepening low east of the Delmarva Peninsula on Saturday morning. This is a near ideal track for heavy snow; it would be perfect if the storm was just another 20-50 miles east, then we would be deep in the deform band behind the storm as opposed to flirting with the dryslot. As with any strong coastal low, we will have to watch for the rain/snow line, especially those who are below the fall line. A track farther east would also keep cold entrenched in the region, preventing a changeover to sleet or rain which would lower snow totals.

Our local NWS office is also on-board with a major snowstorm.

.LONG TERM /FRIDAY THROUGH MONDAY/...
THE THREAT FOR A SIGNIFICANT WINTER STORM CONTINUES FOR THE MID-
ATLANTIC REGION FRIDAY-SATURDAY NIGHT.

MODEL GUIDANCE IS IN AGREEMENT THAT AN INTENSIFYING SFC LOW WILL BE
IN THE VICINITY OF CAPE HATTERAS SATURDAY MORNING. THE DETERMINISTIC
GFS AND EURO ARE IN AGREEMENT PLACING THE SFC LOW JUST NORTH OF
THE CAPE...HOWEVER THE EURO IS ABOUT 6 HRS SLOWER. EITHER WAY...A
SIGNIFICANT WINTER STORM IS PROGGED TO REACH THE MID- ATLANTIC
WITH SNOW SPREADING NORTHWARD FRIDAY. AT THIS TIME...MODEL
GUIDANCE HAS TEMPERATURES ABOVE FREEZING IN VICINITY OF I-95 AND
EAST. THIS WOULD CAUSE LOWER SNOWFALL RATIOS AND THEREFORE LESSER
AMTS. THIS MAY LEAD TO A RAIN-SNOW LINE AS WELL. THESE DETAILS
WILL TAKE TIME TO IRON OUT AS WE ARE STILL 4 DAYS AWAY. CONFIDENCE
IS HIGHER FOR ACCUMULATING SNOWFALL ALONG AND WEST OF THE BLUE
RIDGE THROUGH SATURDAY NIGHT.

PLEASE PAY ATTENTION TO FORECASTS FOR UPDATES THIS WEEK ABOUT THIS
WINTER STORM.

SUNDAY AND MONDAY: HIGH PRESSURE WILL BUILD INTO THE AREA BEHIND THE
DEPARTING LOW SUNDAY. SEASONABLY CHILLY CONDITIONS ARE EXPECTED. A
WEAK COLD FRONT MAY MOVE THROUGH THE AREA MONDAY...BUT THERE WILL BE
LITTLE MOISTURE ASSOCIATED WITH IT.

&&

Jan 18 2016 9:00PM Update
The stakes have risen. Computer models have continued to hold on to the idea Mid-Atlantic snowstorm.  If anything, agreement has increased for a major snowstorm. 

Here's the current idea of storm progression:
Friday: Front-end Thump
Precipitation begins Friday morning as snow, becoming heavy into afternoon and night. The low will pass through the Southeast during this period and being to transfer to the developing coastal storm offshore. This is part of the storm we have the highest confidence in.
Saturday Morning: Wind-driven Precipitation
A coastal low will bomb out east of the Delmarva peninsula. Winds will increase, with sustained winds in the 20-30 mph range, possibly gusting up to 60 mph. Due to the close track and strength of the storm, mixing with rain or sleet is possible during the height of the storm, especially in the eastern areas. We also may be stuck in a dry slot, between the deformation band to the west and the low to the east. There is little confidence in the forecast at this time period. There are still many details to be worked out since they depend on exactly where the coastal low sets up; check back later.
Saturday Evening: Winding down
As the storm pulls away to the NNE, precip will change back over to snow. Another few inches would be possible with the passage of the deformation band before winding down. It is unknown exactly when the precipitation will shut off. I'm guessing sometime in the early evening.

As I mentioned before, the digital snowstorm has looked better and better with each model run. Both the GEFS and EPS Ensemble mean snowfalls for this storm has increased to around a foot and the operational runs of both these Ensembles have given us totals approaching 2 feet. The upper level and mid level low tracks are ideal for this area. Remarkably the GFS and the Euro have nearly identical solutions in this aspect. Where they differ is the surface low placement and precipitation distribution. Warm air intrusion at the mid levels is an issue on the GFS. Mixing is definitely possible so snow forecasts will vary. The important thing is the increased agreement on a major snowstorm. Whether we get something historic, as depicted in some of the model runs, remains to be seen.

EPS Ensemble Mean (51 member mean)-Classic snowstorm look

Original Text
As we head into late Janurary, things have been bleak over the past new weeks. A pattern that was supposed to increase snow chances lead to two cutters, a coastal storm @38 degrees F and a two dustings, one from an arctic front and another from a coastal storm that got shunted south, resulting in under half an inch of snow. I also told some of you that winter would be over in 2-3 weeks. In retrospect that was probably not a good idea as most models have no clue what's going to happen in the next week let alone a month in the future. But anyways, Let's forget about what's going to happen in February and just look at next 7 days.

Chance #0
An arctic front will crash through tonight, dropping temperatures into the low 20s and will bring an outside chance of a snow shower. Chances are the snow we saw today will be all. However, the cold airmass that comes will set us up for the rest of the week.

Chance #1
The next chance of snow will be Wednesday. This will be a clipper type disturbance (storm is giving it too much). It will act like most clippers, dying when it hits the Appalachians. Some non-accumulating flurries look likely at the moment. The bigger story is that the energy from this clipper help set the stage for the next storm as it heads off to sea.

Chance #2
A strong shortwave will hit the West coast in 3 days. As it tracks eastward, cold high pressure drops out of Canada, reinforcing a cold air wedge ahead of the storm. At the upper level, energy associated with the previous clipper will drop south, forcing the shortwave south. The storm is expected to track across the SE before turning the corner and heading up the coast, where current models have it bombing out during the January 22nd to 24th time frame, 6 days out. The operational models vary from a major snowstorm to a major rainstorm. However, operational models are prone to being wildly different from actual outcomes (being very wrong) this far out. Thus, to account for variations in initial conditions, we look at ensemble runs of the models. They are basically 20-50 low resolution runs with random variations in initial conditions. We look at the means of these results. A larger spread would mean lower confidence. What we want is the ensemble mean to show a tightly clustered low track as well as a high mean snowfall. We really can't ask for anything more. All 3 major global ensemble means (GEM/CMC, ECMWF, and GFS) give us more than 6 inches of snow. There are a multitude of possible outcomes with this storm. It looks likely that we can at least expect accumulating snow of some sort. How much will depend on how the atmosphere evolves over the next week. Updates will come as more information is gleamed about the situation.