For those who are wondering what's going on over us tomorrow, a weak coastal low will develop off the coast, which will provide a bit of lift for us NW of the circulation. How much is a good question and this is what the models are struggling to resolve. If it is going to snow, radar will fill in over us. There is no tracking of precip, it will just form. There is a lot of uncertainty in the evolution of this event so any accumulation forecasts or things based off of those (chance at a delay) should be taken with caution. Therefore, I revise the chance at a delay down to 40% in due to the uncertainty.
The latest models are out, arranged in the one that gives us the most, to the one that gives us the least.
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| From the back of the pack to the leader, the GFS gives around .15" liquid ~1-2" snow for our area. |
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| The GEM (Canadian) model gives .1-.15" liquid ~1-1.5 inches snow |
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| 12 km NAM gives us .1 liquid ~1" snow |
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| 4km NAM (The higher resolution NAM, should pick up small scale things better) gives a narrow band of .1 liquid through DC leaving the rest of us with a dusting to half inch |
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| The RGEM gives a dusting to 1 inch too |
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| The HRRR whiffs us |
Original Text:
Tomorrow, the New and Improved* GFS model (Parallel GFS) takes over as the operational American Global Forecasting System. The current GFS is not the best. Today, we started the day with a prediction of no snow for the first of 4 models runs of the day. Now, 4 runs later, the GFS pulls one last trick, giving us 2 inches of snow verbatim tomorrow. That being said all the other models caught on to the idea beforehand, however slowly and reluctantly they did so. The successor if the GFS has yet to catch on to the idea of snow, which is a bit concerning.
Temps tomorrow will be really cold, thanks to high pressure shoving cold air in... again... mid 20s around the time it is supposed to snow. The NWS has issued a Winter Weather Advisory for the immediate DC area for 1 inch of snow.
THE NATIONAL WEATHER SERVICE IN BALTIMORE MD/WASHINGTON HAS ISSUED A WINTER WEATHER ADVISORY FOR SNOW...WHICH IS IN EFFECT FROM 4 AM TO NOON EST WEDNESDAY. * PRECIPITATION TYPE...SNOW. * ACCUMULATIONS...AROUND ONE INCH. * TIMING...ONSET AROUND 4 TO 6 AM...CONTINUING INTO THE LATE MORNING HOURS...BEFORE MIXING WITH PERIODS OF SLEET AND DISSIPATING BY EARLY AFTERNOON. * TEMPERATURES...MIDDLE 20S DURING THE PREDAWN HOURS...INCREASING TO LOW 30S LATER IN THE MORNING.
Once could speculate that this is an slight overreaction to our disastrous snow event last week, where no one listened to the forecast for moderate snow and cold temps during rush hour.
So... Recap... An uncertain forecast 0.5-1.5 inches of snow (technically 0-2 if you account for natural variation in weather) beginning early in the morning and ending by late morning. More on the south side of the county
10% chance of 1.5"+
60% chance of 0.5-1.5
30% chance of 0"-0.5
