(Washington D.C.) Our first chance of some wintry weather and even accumulating snow is increasingly likely as new data comes in.
The second storm system of the week is making its way up the east coast, which will cause major travel disruptions for morning commuters, especially in the north and western suburbs of Washington D.C. For now, a couple of rain showers will linger, but they will move out by early tomorrow morning.
The next system moving in holds a lot of moisture, and by a lot, I mean a LOT.
It is expected to produce a wintry mix and snow for parts of the area. The computer models are now in good agreement of where this system will track, how much snow will fall, and its timing. The timing is pretty well situated where I think the system will arrive early Thursday morning, where temperatures will be cold enough for snowflakes, even in Washington D.C., and especially in north and western communities, such as Leesburg, Manassas, Frederick, MD, Winchester, and Front Royal.
According to the GFS and European models, the system will move in early Thursday morning. Rain will stick to the south, but it will transition into freezing rain, sleet, and snow as it tracks northward into Northern Virginia as it comes into contact with the cold air mass.
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Temperatures are expected to be slightly below freezing Thursday morning, and due to the increase in cloud cover over the next 48 hours, radiational cooling during the evening hours will be slim to none, whereas the incoming solar radiation that warms the air during the day will only raise the temperature by two to five degrees. Most areas will not get above 35 degrees Thursday, some will stay near or slightly below freezing, while D.C. and Baltimore will be slightly warmer, both around 39 degrees.
The snow is expected to start around 5:00 to 6:00 AM Thursday and it will last to about noon for those east of the Blue Ridge Mountains, before transitioning to mixed precipitation and rain. For those WEST of the Blue Ridge, the snow should last until about 4:30 PM, but it will likely stay as sleet or freezing rain, as temperatures will struggle to top 33 degrees.
For now though, a Winter Storm Watch has been issued for the Shenandoah Valley and parts of West Virginia, and it will likely get extended eastward tomorrow, with advisories east of Loudoun County.
So, what about the snow totals? This is really tricky for two reasons,
- The standard ratio between rain and snow is typically 1 inch of rain equals 10 inches of snow, but this is different for months like November, March, and April, where it is significantly less.
- The surface temperatures on the ground are warm, which will reduce any accumulation you would get than if it were December, January, or February.
The three most used forecast models; the GFS, ECMWF, and NAM, are all predicting significant snowfall totals…
|Washington D.C.||4 inches||2 inches||13 inches|
|Manassas, VA||5 inches||6 inches||14 inches|
|Leesburg, VA||7 inches||5 inches||13 inches|
|Winchester, VA||11 inches||10 inches||13 inches|
|Front Royal, VA||11 inches||11 inches||14 inches|
|Harrisonburg, VA||7 inches||8 inches||16 inches|
|Charlottesville, VA||3 inches||8 inches||17 inches|
|Culpeper, VA||5 inches||9 inches||14 inches|
|Fredericksburg, VA||3 inches||6 inches||12 inches|
|Baltimore, MD||5 inches||4 inches||13 inches|
|Petersburg, WV||13 inches||8 inches||15 inches|
Out of these three best snow forecast models, the NAM is totally worthless crap when it comes to its forecast. There is just no way that there is going to be 17 inches of snow in mid-November in Charlottesville, nor is it likely for most of the other areas (only exception was the Veterans Day Snowstorm of 1987).
The GFS and European models are also overestimating the possible snow totals, but they are much more realistic and would even be possible if we were to get colder air in place than what we are getting.
Due to warm surface temperatures in the soil and on paved surfaces, plus the low rain to snow ratio for November, the snow totals are likely to be half of what all models averaged show. Models simply do NOT pick up surface temperatures and the low rain to snow ratio when they make their model runs.
So, with that said, here is FirstWatch Weather‘s snow forecast for the DC area, Thursday into Friday.
The bottom line is that some accumulation is possible. I even think D.C. might see a dusting to half an inch before the rain melts it all, but as for the northern and western suburbs, we are looking at 0.5 to 2 or more inches, some of which may stay through Friday afternoon.
As WeatherBELL meteorologist Joe Bastardi always says,
“Enjoy the weather, its the only weather you got.”