Well the NWS downgraded us to an advisory. 2-5 inches of snow across the county. The inverted trough seems to set up just NE of us, centered over Baltimore. FYI the delay is just to buy time. Its dumping snow in the northern parts of the county. Approaching 3" in Clarksburg. So we'll see.
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| 355 and Clarksburg Road |
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| I-270 and Clarksburg Road |
11:50 PM Monday 2/8/2016 Update:
For those of you wondering where the snow is. It's still up in Baltimore... Surface temperatures have dropped to the mid 30s but there seems to be a warm layer aloft that still needs to be busted. For that we need precip rates, which are lackluster at best at the moment. I'm expecting the lower ends of forecasted amounts to accumulate. This event is also going to be a headache for the schools. There will be no precip shield to track. The models show the snow developing right over us around 6 AM, after decisions are to be made. So at 5 AM, roads will be damp and nothing much will show on radar. To further add to the mess, the HRRR brings a very heavy band of snow through midday int o the afternoon. It's stuck in no man's land between early release and regular release times. Maybe this will be enough to scare the county into closing.
8:30 PM Monday 2/8/2016 Update:
Ahead of the onset of snow, the NWS has increased snow totals for the area. They are now going with the higher end of model guidance, 3-5" downcounty and 6-9" upcounty. Not sure if I agree with that. I'm going with 3-6" upcounty and 2-4" downcounty. The event is getting going now so we'll see.
The first band of precipitatoin has passed through the area as rain and temperatures have falling into the upper 30s across the county through evaporative cooling. This is in line with computer model projections.The 18z suite of models held with the idea of a localized maximum of precipitation somewhere between DC and Baltimore. Still no clue where it will set up but heavy precip is needed if you want the snow to stick in such marginal temperatures.
The next band of precip which is over Richmond should expand as it approaches us. This is our first in a series of benchmarks for accumulating snow. It is within this band that precipitation will change over to snow. If this doesn't happen, then we can start worrying. This is going to be a nowcasting event. Right now, the rain/snow line is near the MD/PA border and should begin to work its way south as evaporative cooling erodes the warm layer near the surface. Upper level temperatures are well cold enough for snow.
Well the first wave went well, bombing off the coast and preventing the second storm from developing into something meaningful. It is a beauty of a storm, 980mb of atmospheric power. Too bad it's 250 miles too far east.
First off, the NWS Snow map:
...WINTER STORM WATCH IN EFFECT FROM LATE TONIGHT THROUGH LATE TUESDAY NIGHT... THE NATIONAL WEATHER SERVICE IN BALTIMORE MD/WASHINGTON HAS ISSUED A WINTER STORM WATCH...WHICH IS IN EFFECT FROM LATE TONIGHT THROUGH LATE TUESDAY NIGHT. * HAZARD TYPE...SNOW WITH PERIODS OF HEAVY SNOW. * ACCUMULATIONS...SNOW ACCUMULATION OF 6 TO 9 INCHES. * TIMING...PRECIPITATION WILL BEGIN LATER TODAY...INITIALLY AS RAIN OR A RAIN/SNOW MIX. THE PRECIPITATION WILL TRANSITION TO ALL SNOW TONIGHT AND LAST THROUGH TUESDAY NIGHT...WITH PERIODS OF HEAVY SNOW DURING THIS TIME.
The simple fact is that widespread snowstorms usually don't happen behind storms as powerful as the first one so we're going to have to claw our way to a decent event in an unusual way. Energy over the Midwest from the kicker will spawn a coastal low off the coast of VA/MD. As this happens, an projection of low pressure -an inverted trough- will form west of the coastal over the Mid-Atlantic region. Where the inverted trough is is where the heaviest precipitation will set up. This will be quite a narrow band and can be likened to forecasting lake-effect snow bands. You know they will happen but don't know exactly where they will set up. Multiple waves of precipitation will pass through the region as pockets of upper level energy rotates around the low in the Great Lakes through Tuesday night. We expect 0.25-0.5 inches worth of liquid with localized areas to 1", most likely NE of the area.
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| The red line highlights the inverted trough over DC |
Another issue is going to be surface temperatures. Throughout the whole event, temperatures are forecast to range between the mid to upper 30s. We are relying on evaporative cooling at the onset of the storm and dynamic cooling from heavy precipitation to cool the lower atmosphere enough for the snow to stick. No precip=no cooling which leads to non-accumulating snow (white rain). So in this setup, elevation helps. That's why the winter storm watch is only issued for the Northern part of the county, which is colder and higher up.
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| No real cold air at precip onset |
Overall, this event has a high bus potential. But it seems that all models are putting the inverted trough and the heaviest precipitation in N and NE MD. DC would be at the southern fringe of the heaviest precipitation, which is a very precarious place to be if you are a snow lover. Everything is just favorable enough to give snow so any small shift could make or break the event. This is now a nowcasting event. Whether this event happens as forecast or not, as long as the NWS office holds to their forecast, MCPS should close tomorrow. Looking into the long range, the status of our winter looks alive and well It'll be cold and we may be able to time a few more storms with the cold. Oh, and Happy Lunar New Year
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