Today was a surprise...

Today's snow was quite a surprise. It was not caught well by any of the models save for some short range models such as the NAM 4km Nest and the Canadian RGEM models. Global models did not foresee any snow for today. 1-3 inches of snow fell in the immediate DC metro, with less elsewhere, quite a interesting bullseye. It seems that more snow falls elsewhere most of the time. 2.8 inches fell at DCA, bringing the seasonal total to 18.3 inches at DCA.

Total snowfall today

The NWS has issued a winter weather advisory for tonight into tomorrow morning for snow with 1-3 inches possible.

THE NATIONAL WEATHER SERVICE IN BALTIMORE MD/WASHINGTON HAS
ISSUED A WINTER WEATHER ADVISORY FOR SNOW...WHICH IS IN EFFECT
FROM 1 AM TO NOON EST WEDNESDAY.

* PRECIPITATION TYPE...SNOW.

* ACCUMULATIONS...1 TO 3 INCHES.

* TIMING...SPREADING EAST BETWEEN 2 AND 4AM. SNOW WILL END BY NOON.

* TEMPERATURES...MID TO UPPER 20S.

* WINDS...LIGHT AND VARIABLE...BECOMING WEST AROUND 10 TO 15 MPH
  BY NOON.

* IMPACTS...SNOW ACCUMULATION WILL AFFECT THE WEDNESDAY MORNING
  COMMUTE. UNTREATED ROADWAYS WILL BE SLICK.

Official Snow forecast

These are the NWS forecasts around MoCo.

Location	Min	Likely	Max	0"	0.1-1"	1-2"	2-4"	4-8"	8-12"	12-18"	>18"
Burtonsville, MD	0	2	4	2%	26%	35%	37%	0%	0%	0%	0%
Chevy Chase, MD	0	2	4	3%	27%	32%	38%	0%	0%	0%	0%
Damascus, MD	0	2	3	4%	28%	45%	23%	0%	0%	0%	0%
Germantown, MD	0	2	4	3%	27%	37%	33%	0%	0%	0%	0%
Poolesville, MD	0	2	3	5%	28%	40%	27%	0%	0%	0%	0%
Rockville, MD	0	2	4	3%	27%	33%	37%	0%	0%	0%	0%
Silver Spring, MD	0	2	4	3%	27%	32%	38%	0%	0%	0%	0%
Takoma Park, MD	0	2	4	3%	26%	30%	41%	0%	0%	0%	0%

The WPC seems quite excited about this clipper.

DAY 1...

...MID-ATLANTIC/NORTHEAST...

ANOTHER STRONG...FAST MOVING SHORT WAVE WILL TRAVERSE ACROSS THE
MID-ATLANTIC EARLY HOURS ON WEDNESDAY AS THE JET STREAK
STRENGTHENING ACROSS THE REGION.  THIS WILL REINFORCE ANOTHER COLD
FRONT TO PASS THROUGH...AND WITH ENOUGH LIFT AND MOISTURE IN PLACE
A SECOND ROUND OF SNOW FOR THE MID-ATLANTIC IS EXPECTED.  THE
ECMWF/GFS AND EVEN THE NAM/SREF HINTED AT A SLIGHTLY ENHANCED QPF
BULLSEYE OVER THE DELMARVA REGION...BETWEEN 0.10-0.20 INCHES. 
KEPT THE ACCUMULATIONS IN THE MID-ATLANTIC AT 1"...BUT THERE IS
CERTAINLY A CHANCE TO SEE LOCALLY HEAVIER AMOUNTS. 
HOWEVER...SINCE THESE HIGHER TOTALS WILL BE LOCALIZED...DECIDED TO
KEEP OUT THE 4 INCHES OR MORE PROBABILITIES. 

For those who want hope...

This map basically shows the high end scenario of this storm. Although this is more likely than a low end bust, it is still quite unlikely. The highest amounts are more likely to the east since they will have the influence of a developing coastal low.
There are 2 ways of achieving higher than forecast amounts. The first , and traditional way is to have more precipitation than expected. This is a very dry system, a clipper. However, the atmosphere over our region has been sorta primed by the snow today. The dew points are higher, cutting down on snow lost to evaporation. In addition, this storm will have more upper level support, with a jet streak (local maxima of jet stream winds) over the area, this will allow some banding to occur and enhance snowfall rates. This may result in overachieving totals. This was the case today. The jet streak was right over the DC area so the snow fell over us. There is no guarantee that the bullseye will be over the same area again. The second way, is to have higher snow to liquid ratios. Upper level temperatures will be very cold, allowing snowflakes with open structures to form. This will mean there is more air in the snow but it would accumulate more. The snow will be light and fluffy.

We have a decent chance of a 2hr delay, maybe even a day off if the storm way over performs by a lot. Need to go do hw... Maybe I will come out with model outputs later but those are all about the same with .1-.2 QPF...

Thanks for reading!

-Alex