Bryce Resort / Basye

Summary

SYNOPSIS

... A strong cold front and potent area of low pressure will impact the area today into Monday morning bringing heavy rain, gusty winds, and mountain snow. The potent weather system pulls to the north and east Monday with high pressure building in for the middle of the workweek.

NEAR TERM /THROUGH TONIGHT/... The potent upper-level trough with northern and southern stream energy will continue to slowly pass through the Great Lakes, Tennessee Valley, and Gulf Coast states today while surface high pressure remains well offshore over the Atlantic. The cold front associated with the trough axis will slowly approach from the west during this time. This is a potent system and this can be seen by the strong meridional component to the upper-level trough axis. Therefore, warm advection and moisture advection will be strong ahead of the cold front. Also, the thermal gradient will be quite strong with subtropical air being pulled into the area ahead of the cold front and a Canadian airmass on the other side of the boundary. A strong low-level jet will also aid in moisture advection as well with pwats most likely around 3 to 4 standard deviations above climo.

Therefore, widespread rain is expected across the area today into tonight. There is some elevated instability progged in much of the latest guidance, suggesting and embedded thunderstorm is possible with the convection. A line of heavier showers and perhaps a thunderstorm will also accompany the frontal passage later this afternoon into this evening. afternoon/evening. Given the strong winds aloft, this has the potential to mix down gusty to perhaps even locally damaging wind gusts. One mitigating factor will be the lack of instability that is progged to be rooted within the boundary layer. Therefore, certainty for damaging wind gusts is low at this time (with the best chance for strong to damaging wind gusts near and east of the blue Ridge Mountains). A soaking rain is expected given the dynamics and moisture associated with this system. Rainfall amounts around 1-3" are most likely, and much of that may fall in a 3 to 6 hour period this afternoon and evening. A Flood Watch is in effect for the Washington and Baltimore Metropolitan areas into portions of northern VA and northeastern MD where the heaviest rainfall is most likely to overlap with relatively lower FFG values due to urban areas.

Colder air will move in behind the front, first this evening in the mountains, and then later tonight from northwest to southeast across the valleys and metro areas. With the upper- level trough axis lagging behind the frontal passage by a few hours or so, this suggests that there will be some anafrontal characteristics to the boundary. Therefore, moderate precipitation is expected for a few hours or so behind the cold front before drier air eventually works its way in toward Monday morning. There will be enough cold air for rain to change to snow in some areas. As of now, it appears that the heaviest snow will be in the mountains. Winter headlines are in effect. For locations along and west of the Allegheny Front, an upslope component to the low-level flow will cause additional snow showers to last longer behind the cold front, enhancing accumulations.

A slushy coating to an inch of snow will make it into some of the valleys and a slushy coating may approach the metro areas. However, the most likely scenario is for the boundary layer to remain above freezing so impact should be minimized.

SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... The cold front will move off to the east Monday and a northwest flow will usher chilly conditions. There will be a snow showers to start along/west of the Allegheny Front (flurries may spill east) before drier air works its way into the area during the afternoon. Winter weather headlines continue through Monday morning along/west of the Allegheny Front.

The main story for Monday will be the blustery and gusty northwest winds due to low pressure rapidly intensifying to our northeast (system phases during this time). Frequent gusts around 30 to 45 mph are possible for most areas. Even stronger winds are possible over the ridges and an a Wind Advisory may be warranted. High pressure will build toward the area Monday night. Winds will gradually diminish, but it will be cold with lows in the 20s for most areas (teens in the mountains and portions of the Shenandoah Valley).

High pressure will bring dry and chilly conditions Tuesday.

LONG TERM /WEDNESDAY THROUGH SATURDAY/... Surface high pressure continues building into the region Wednesday and will be the feature dominating the weather for our area through the remainder of the week and into the weekend, leading to dry conditions. A reinforcing cold front is expected to pass through Wednesday but the moisture starved air mass won't bring any precipitation. The next shot for precipitation doesn't look to approach the area until late in the weekend, if not early next week.

Guidance diverges significantly after Friday, with models disagreeing on how to develop a series of shortwaves within both the northern and southern streams. Current suite of ensembles only bring marginal PoPs into the area by Sunday at the earliest, and most suggest later at this point.

Near normal temperatures Wednesday cool to below normal going into Thursday with the passage of the reinforcing cold front, highs struggling to get out of the low 40s for most of the area Thursday after morning low temperatures well into the 20s. Temperatures moderate going into the weekend.