Area Forecast Discussion
Issued by NWS Sterling, VA
Issued by NWS Sterling, VA
358 FXUS61 KLWX 130114 AAA AFDLWX Area Forecast Discussion...UPDATED National Weather Service Baltimore MD/Washington DC 914 PM EDT Mon Aug 12 2024 .SYNOPSIS... Tranquil weather conditions are expected through Wednesday as surface high pressure resides over the Northeast and Mid-Atlantic states. Precipitation chances return later this week and into the weekend as a slow moving area of low pressure and series of fronts cross the region. && .NEAR TERM /THROUGH TUESDAY/... Scattered mid-high level clouds are expected overnight as shortwave energy moves across the area. Low temperatures will be similar to this morning, if not a touch warmer. && .SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/... As the upper level trough lifts off to the northeast early on Tuesday, high pressure is expected to build over our region and remain in place through the majority of this week. North to northwesterly flow will remain in place leading to continued dry conditions and near normal temperatures through Wednesday for most of the region. Some model guidance has a chance for a few thunderstorms over central Virginia on Wednesday due to a combination of an upper level jet and an upper trough nearby, but a lack of low level moisture will limit threat for storms and showers. && .LONG TERM /THURSDAY THROUGH MONDAY/... Key Messages: 1) Increasing chances for showers and thunderstorms Friday into the upcoming weekend. 2) Near normal temperatures expected through the period. Not too much of a change in the extended period although both deterministic and ensemble models continue to slow the progression of an approaching low pressure system over the Great Lakes and it`s associated fronts for the latter half of the workweek. Thursday continues to trend dry with an outside chance of an isolated shower or thunderstorm over ridges west of the Blue Ridge. This is largely due in part to brief upper level ridging building back overhead with the trough exiting east and the incoming trough back across the Midwest/Ohio River Valley. One thing to note will be the low level flow out of the south ushering in more humidity and high temperatures around 90 degrees Thursday afternoon. By Friday, eyes turn toward the amplifying shortwave trough digging south from the Ohio River Valley. With the trough will come an area of low pressure ejecting north and east from the Upper Midwest into the northern Ohio River Valley and Great Lakes region. As the low pressure system, lifts north and east it`s associated warm front will cross the area Friday into Saturday followed by a cold front Sunday into early next week. Until the cold front passes low level flow will remain out of the south and southwest advecting more moisture into the region. This will lead to increased shower and thunderstorm chances Friday and into the weekend especially for areas along and west of the Blue Ridge. As of now, severe weather and flooding do not appear to be a concern given the several dry days of weather leading up to the weekend. Current 12z precipitable waters from both the ensembles and deterministic runs average around 1.25-1.75 inches. Any rain that we do see will be beneficial as we continue to chip away at the drought across the region. Temperatures will remain near normal throughout the period. 850 mb temperatures will sit right around +15 to +17 degrees C Friday through SUnday. This will yield highs in the mid to upper 80s east of the Alleghenies with lows in the 60s and 70s. One caveat would be that temperatures could be slightly cooler than normal this weekend given abundant cloud cover and increased precipitation chances with multiple fronts nearby. && .AVIATION /01Z TUESDAY THROUGH SATURDAY/... Winds will remain out of the north to northwest through Wednesday with afternoon gusts of 16 to 20 knots possible. Scattered high clouds are expected overnight. Cloud cover will thin out on Tuesday with VFR conditions expected through Wednesday and winds generally out of northwest. Prevailing VFR conditions expected Thursday and Friday at all terminals with high pressure nearby. Light north to northwest flow Thursday will switch to the south Friday as high pressure slides offshore. Periods of sub-VFR are expected this weekend as shower and thunderstorm chances increase with an area of low pressure and it`s associated fronts set to cross the region. && .MARINE... Light north to northwesterly winds are expected through Wednesday with subSCA conditions. No marine hazards are expected through Friday morning as surface high pressure slowly slides east of the area. Light north to northwest winds are expected Thursday switching to the south Friday. SCA level winds may return as early as Friday afternoon and night due to southerly channeling. Additional concerns for southerly channeling can be expected Saturday and Sunday as the gradient tightens with the next front set to cross the region. Shower and thunderstorm chances will also pose a threat to mariners during the afternoon and evening hours this weekend. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && $$ SYNOPSIS...LFR NEAR TERM...LFR SHORT TERM...JMG LONG TERM...EST AVIATION...LFR/EST MARINE...LFR/EST