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Area Forecast Discussion
Issued by NWS Sterling, VA
Issued by NWS Sterling, VA
781 FXUS61 KLWX 131837 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 237 PM EDT Tue Aug 13 2024 .SYNOPSIS... Broad high pressure will continue to maintain mainly dry weather conditions and low humidity through Thursday. Precipitation chances return by Friday and into the weekend as a slow moving area of low pressure and series of fronts cross the region. This system exits off the coast Monday into Tuesday with high pressure set to return to the region by the middle of next week. && .NEAR TERM /THROUGH TONIGHT/... The cold front that impacted our region over the weekend has continued to drift southward into parts of Georgia and Southeast South Carolina this afternoon. Behind this boundary, high pressure has slowly built into our region from the midwest and Great Lakes regions. Below normal temperatures are being observed for the second day in row this afternoon with dewpoints in the 50s making it feel like mid to late September. The morning showers that were observed in parts of central Virginia have dissipated and clouds are slowly starting to break up. Scattered to broken cloud decks continue to be observed in areas along and south of I-66 with light winds generally out of the north to northwest. Dry and below normal temperatures are expected to continue through this evening. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... Upper level ridging will slowly build over the region from the west on Wednesday with high pressure in control at the surface. Winds will continue out of the north and lead to another day of near normal temperatures with dewpoints in the 50s once again. Skies will be much clearer than today with mostly sunny conditions expected. The pattern starts to break down on Thursday as the upper level ridge shifts off to the east, but high pressure will remain in control. Winds will begin shifting out of the south leading to increasing temperatures and dewpoints. High temperatures should return near normal with highs in the upper 80s to lower 90s. Upper level troughing starts to build into the region late Thursday evening. Shortwave energy dropping into our region from the west will bring increasing chances for showers during the overnight periods into early Friday morning. && .LONG TERM /FRIDAY THROUGH TUESDAY/... 1) Not a washout this weekend, although scattered to numerous showers and thunderstorms are expected. 2) Near normal temperatures expected through the period. 3) Drying back out early next week. 12z deterministic and ensemble guidance continues to show an amplifying shortwave trough digging south from the Ohio River Valley for the end of the workweek. 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 Saturday especially for areas along and west of the Blue Ridge. More widespread shower and thunderstorm activity is likely Sunday as the cold front and upper level trough swing through the region. Once again no washouts are expected on any given day between Friday through Sunday with the bulk of any thunderstorm coverage contained to the afternoon and evening hours. After several dry days of weather flooding does not appear to be an issue. Any rain that we do see will be beneficial as we continue to chip away at the drought across the region. Precipitable water values through the weekend will run between 1.25-1.75 inches due in part to increased southerly low level flow. As for the severe weather threat, it remains very low. Will continue to monitor this threat for Friday as the warm front lifts into the region and the weekend as we sit in the warm sector ahead of the approaching upper level trough. Trailing shortwave energy will follow the front Monday leading to additional shower chances east of the Blue Ridge. It`s not until the middle of next week when surface high pressure builds back into 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 /19Z TUESDAY THROUGH SUNDAY/... VFR conditions are expected through Wednesday with winds generally out of the north. A period of 15 to 18 knots gusts will be possible in the afternoon during peak mixing. Prevailing VFR conditions expected Thursday through Sunday 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 (mainly during the afternoon & evening hours) as shower and thunderstorm chances increase with an area of low pressure and it`s associated fronts set to cross the region. Winds Saturday and Sunday increase out of the south with gusts around 15-20 kts both afternoons. && .MARINE... SubSCA conditions are expected through Wednesday with winds generally out of the north. 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. The open waters in the central and southern Bay are the areas most likely to reach SCA criteria. Shower and thunderstorm chances will also pose a threat to mariners during the afternoon and evening hours this weekend. && .TIDES/COASTAL FLOODING... Tidal Anomalies remain relatively low, but a few tide cycles may reach action stage at a couple of sensitive sites. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && $$ SYNOPSIS...JMG NEAR TERM...JMG SHORT TERM...JMG LONG TERM...EST AVIATION...JMG/EST MARINE...JMG/EST TIDES/COASTAL FLOODING...