The National Weather Service has issued a winter storm watch for the entire Washington and Baltimore metro regions from 7 p.m. Wednesday night through 10 p.m. Thursday night. The forecast office serving the region sees the potential for at least 5 inches of snow and sleet in the region. (By definition, a watch is issued when the office believes there is at least a 50 percent chance of 5 inches or more snow falling)
Here’s the watch text, in its entirety:
...WINTER STORM WATCH IN EFFECT FROM WEDNESDAY EVENING THROUGH THURSDAY EVENING... THE NATIONAL WEATHER SERVICE IN BALTIMORE MD/WASHINGTON HAS ISSUED A WINTER STORM WATCH...WHICH IS IN EFFECT FROM WEDNESDAY EVENING THROUGH THURSDAY EVENING. * PRECIPITATION TYPE...SNOW AND SLEET * ACCUMULATIONS...THE POTENTIAL FOR 5 OR MORE INCHES OF SNOW AND SLEET. * TIMING...SNOW IS EXPECTED TO MOVE IN FROM THE SOUTH WEDNESDAY EVENING. SNOW MAY MIX WITH SLEET AND RAIN LATE WEDNESDAY NIGHT AND THURSDAY. THE SNOW COULD BE HEAVY AT TIMES WEDNESDAY NIGHT AND THURSDAY. * TEMPERATURES...IN THE MID TO UPPER 20S WEDNESDAY NIGHT...SLOWLY RISING INTO THE LOWER AND MIDDLE 30S THURSDAY AFTERNOON. * WINDS...NORTH 15 TO 25 MPH WITH GUSTS UP TO 35 MPH. * IMPACTS...ROADS MAY BECOME SNOW AND SLEET COVERED AND SLIPPERY. TRAVEL MAY BE DANGEROUS WEDNESDAY NIGHT AND THURSDAY. HEAVY WET SNOW COULD LEAD TO SOME POWER OUTAGES. PRECAUTIONARY/PREPAREDNESS ACTIONS... A WINTER STORM WATCH MEANS THERE IS A POTENTIAL FOR SIGNIFICANT SNOW AND SLEET ACCUMULATIONS THAT MAY IMPACT TRAVEL. CONTINUE TO MONITOR THE LATEST FORECASTS.
Model snow maps
Just to give you a sense of what models are forecasting, here is the snowfall output from the GFS, NAM, Canadian, and European models, from today (12z and 18z) runs. We don’t think any of these models has a great handle on amounts this far out (and will not put these out on social media given the possibility of misinterpretation) – but we share them to give you a sense of the range of forecasts and convey why the National Weather Service is likely issuing a watch at this time.
1. NAM model (updated 18z run – heaviest snow near and just east of D.C.; note, this model’s reliability at longer ranges can be suspect, and it has the bias of simulating too much precipitation at times)
2. GFS model (heaviest snow southeast of D.C.)
3. European model (heaviest snow west of D.C.; note – we think this simulation is probably overdone along the I-95 corridor as the model’s forecast track doesn’t support these kind of snowfall totals and it warms temperatures above freezing suggesting some rain and/or mixed precipitation.)
4. Canadian model (heaviest snow near D.C.)