Forecast Discussion
Sunday, December 25, 2022 1:00PM EST
Winter Weather Advisory in effect until 5pm est, Dec 25, 2022
High Wind Warning in effect until 8am est, Dec 26, 2022
Wind Chill Warning in effect from 8pm est, Dec 25, 2022 until 10am est Dec 26, 2022
The next 36 to 48 hours will be very notable in the sensible weather department. An intense snow squall w/ occasional lightning associated with the arctic front is currently moving east through the Appalachian mountains at around 50 or so kts. Snow Squall Warnings are already in place extending from eastern WV to the I-95 corridor. With increased sunshine associated with the mid-level dryslot moving overhead surface temps ahead of the line have warmed up into the upper 30s/lower 40s while dewpoints remain relatively high in the mid/upper 20s across the DC and Baltimore metros. With the very steep environmental lapse-rates immediately ahead of the front a couple hundred j/kg of MLCAPE has developed. This combined with the extreme forcing along the front courtesy of the impressive dynamics associated with the shortwave through swinging through and strong deep-layer shear in place (especially considering the thermodynamics) may lead to even further intensification of this low-topped convection. Lots of areas in northern WV received a quick 1 to 3 inches of snow from this squall. While temperature east of the mountains are well above freezing even more extreme snowfall rates, owing to the increasing instability that the system is moving into, will offset the effects of initial melting and graupel mixed in with the snow so that snow totals are similar east of the mountains.
Snow Squall Impacts:
1. Widespread severe wind gusts (55-65+ mph) will accompany this squall leading to scattered to numerous power outages and many downed trees.
2. Instantaneous snowfall rates of several inches per hour will lead to whiteout conditions w/ visibilities dropping to 100 feet or less at times. Snowfall amounts will total 1 to 3 inches w/ locally higher amounts possible.
3. Temperatures will rapidly fall from near 40F into the 20s in a matter of minutes leading to flash freeze conditions across the entire area as the system moves through.
All of this will combine to make travel virtually impossible for a time. Use extreme caution and avoid travel until the squall has passed. Even then, use extreme caution with icy roadways and downed trees/powerlines.
Other than wind and snow, the temperatures tonight and tomorrow will be the main story. West-northwesterly winds will remain very strong with sustained winds of 25 to 40mph and gusts to around 60mph through the evening and much of the night. Winds will still be gusting to around 45mph by dawn Monday morning. Meanwhile, temperatures will fall through the 10s and into the single-digits through the evening and overnight hours bottoming out in the lower single-digits in the urban corridor and southeast areas w/ lower negative single-digits well northwest and around 0F in the close-in NW suburbs. Wind chills will hover around 20 to 30F below zero across the Greater Metropolitan area throughout the overnight hours until dawn w/ windchills falling to as low as 35F below zero in far northwestern suburbs. Temperatures will only rise into the mid-10s or so during the afternoon with wind chills remaining around 0 to -5F with the still brisk though, by then, sub-advisory level winds. With diminishing winds and clear skies Monday night into Tuesday morning leading to decent enough radiational cooling conditions, temperatures may drop to as low as -5 to -10F in the coldest northwestern suburbs and valleys with temps probably remaining at or just above zero in urban areas and near the bay.
Alerts:
Winter Weather Advisory in effect until 5pm est, Dec 25, 2022
High Wind Warning in effect until 8am est, Dec 26, 2022
Wind Chill Warning in effect from 8pm est, Dec 25, 2022 until 10am est Dec 26, 2022
“Forecaster”: George BM
