Massanutten Resort / Harrisonburg

Summary

SYNOPSIS

... Daily chances for showers and thunderstorms look to continue through Thursday as multiple fronts and waves of low pressure push across the area. A potent cold front will bring an increased threat for severe thunderstorms and flash flooding Thursday into Friday. Rain chances decrease into the weekend with cooler temperatures and less humidity as high pressure nears the region.

NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... Remaining radar returns are rapidly dissipating as of 9 PM. Only some mid level clouds are left from an earlier line of convection in the Ohio Valley. While a stray shower can't totally be ruled out this evening, it does appear most stay dry with a lack of focus for forcing.

Eyes turn to ongoing severe convection in the Ohio Valley, with those remnants likely approaching the area after midnight. While severe thunderstorms are not anticipated locally, some showers and isolated storms may continue eastward across the area late tonight and very early Wednesday due to weak elevated instability and a slight steepening of lapse rates associated with the feature aloft.

Fog is looking less prevalent than previous nights, but could at least see some patchy fog developing late, particularly behind any showers that move through. Overnight lows will be in the 60s for most locations.

SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/... On Wednesday, the instability in the atmosphere will be greater given a few more breaks in the clouds due in part to west to southwest flow. This will allow for some downsloping and compressional warming especially east of the Blue Ridge. The combination of downsloping flow and subtle subsidence in the wake of the decaying MCS Wednesday morning may inhibit a widespread thunderstorm threat especially along and north of the I-66/US-50 corridor. Even with that said, scattered strong to severe storms remain, with most recent CAMs targeting the central VA Piedmont to southern Maryland. The primary threat for storms will be damaging winds and localized flash flooding. Large hail up to 1" in diameter is also possible. Highs on Wednesday will soar into the mid to upper 80s across many lower elevation locations, with even a few areas potentially hitting 90 degrees. The mountains will be in the mid to upper 70s for the afternoon.

Mid-level troughing continues to deepen Wednesday night into Thursday sending a potent cold front from the Ohio River Valley toward the region. As a result, expect increasing shower and thunderstorm chances late Wednesday night into Thursday morning as another impulse of energy ripples through. Flash flooding could become a concern here given the increased PWATS above climatology for this time of year combined with antecedent conditions from multiple rounds of showers and thunderstorms earlier in the week.

There will be a break between the morning precipitation and the afternoon in which the atmosphere reloads especially in areas east of the Blue Ridge. Instability parameters increase by Thursday afternoon just ahead of the cold front, this will allow for the potential for strong to severe thunderstorms to develop. One caveat is that overall thunderstorm coverage may be limited with the enhanced cloud coverage and stabilization from morning activity. Main threats with storms Thursday look to be damaging winds, large hail, and localized flash flooding.

Afternoon highs Thursday will climb into the upper 70s to low 80s for most areas. Northwest flow kicks in behind the cold front Thursday night and will bring lows in the 40s along the Allegheny Front with 50s further east.

LONG TERM /FRIDAY THROUGH TUESDAY/... A strong cold front will track through the area early Friday. While shower and thunderstorm chances linger, the threat for severe weather should diminish in the wake. After spending the previous couple of days in the 80s, temperatures will certainly cool off to finish out the work week. Friday's forecast highs are likely confined to the mid 60s to low 70s, locally falling into the 50s across mountain locales. Depending on how quickly showers come to an end, some late day clearing is not out of the question. Northwesterly winds will be breezy at times with gusts up to 20 to 25 mph at times. Nighttime conditions will be cool with lows dropping into the mid 40s to low 50s.

This weekend will be a mixed bag given the cyclonic flow aloft. Each day is forecast to carry a risk for some isolated to scattered shower activity. High temperatures should be around 3 to 6 degrees below average. That is, mid 60s to low 70s for most, but with mainly 50s for the mountain regions. Compared to the humidity earlier in the week, it will feel much drier with dew points down in the 40s. In between disturbances, there will likely be some periods of sun, particularly by Sunday afternoon behind the next frontal system. Expect temperatures to rebound into early next week as heights begin to build.