Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 171428 AAA AFDLWX Area Forecast Discussion...UPDATED National Weather Service Baltimore MD/Washington DC 1028 AM EDT Tue May 17 2022 .SYNOPSIS...
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A cold front will drop through the area this afternoon. High pressure will follow tonight into early Wednesday. A warm front will develop over the south-central Appalachian Mountains tonight, then lift northeastward through early Friday. A cold front is expected to approach from the Midwest over the weekend. High pressure will likely follow early next week.
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&& .NEAR TERM /THROUGH WEDNESDAY/...
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A mainly dry cold front will cross the area this afternoon. Guidance show lots of mid-level clouds (bases around 8kft) accompanying this front as it crosses the area and even a few CAMs show a few sprinkles or a spotty shower or two across northwestern areas. 12Z IAD sounding shows wind gust potential up to 25 kt likely through the day after nocturnal inversion erodes. Anything that happens should dissipate by 00Z tonight with clear skies expected tonight. Previous afd... A secondary cold front will drop southeastward out of Pennsylvania. There is very little moisture in the atmosphere, so no rain is expected. However, a some cumulus clouds will likely develop along the front during the afternoon. The front will also act to kick up winds a bit, with gusts of 25 to 30 mph possible at times. Humidity should drop markedly through the day, as well. Mainly clear and calm conditions are expected tonight into Wednesday morning, though some high clouds may begin to filter in late tonight. A warm front is then expected to develop over the south-central Appalachian Mountains Wednesday. As it lifts northward, a subtle wave aloft will crest around a building ridge. Low-level warm advection coupled with this wave and the nearby warm front may lead to the development of showers and a few thunderstorms by late Wednesday.
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&& .SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/... With the warm front nearby and a disturbance aloft, at least scattered showers and a few thunderstorms may linger much of Wednesday night. Shear profiles are rather impressive, but instability (especially in the low levels) is currently expected to be lacking. Should more instability be realized, a hail or gusty wind threat could evolve, especially if upstream convection that may develop over the Ohio/Tennessee River Valleys manages to hold together as it approaches. Overnight guidance has trended somewhat stronger with a surface low lifting through western Pennsylvania, which raises the threat of showers and storms at least a bit. The warm front will continue a slow northward jog Thursday. Instability likely increases. Shear becomes a bit more modest, but would still be enough to support some organized convection if it were to develop. The question is whether or not anything develops, as there appears to be a lack of a trigger much of the day. Perhaps warm advection or daytime heating will do the trick. For now, the threat for any strong to severe storms looks low and conditional, but is worth keeping an eye on. The warm front will continue to lift slowly northward Thursday night. The GFS has been showing a stronger potential for some showers and thunderstorms Thursday night beyond what most other guidance currently shows, but again given the warm front nearby, it`s worth keeping an eye on. Otherwise, temperatures and humidity will increase during this time. && .LONG TERM /FRIDAY THROUGH MONDAY/... By Friday and Saturday, the region will be firmly in the warm sector with a large ridge of high pressure situated off the southeast coast. Most areas will see the hottest days so far this year, with temperatures pushing into the upper 80s to mid 90s and heat indices potentially in the upper 90s. High temperatures could approach records. There will likely be a cap in place preventing much in the way of thunderstorm development. Subtle height falls and/or convective propagation from the Ohio Valley will provide a little higher chance for showers and thunderstorms Saturday afternoon and evening, especially western areas. The greatest shear will remain to the northwest, with storm strength dependent on instability and forcing. On Sunday, a cold front to our northwest will finally receive a push to the southeast, resulting in the highest rain chances for the weekend. Timing is still uncertain, which will be important for how much instability can build (as well as high temperatures). At this time, thunderstorm potential is highest across the eastern part of the area. The front will likely be south of the area on Monday, although there is some risk of it stalling, which could cause clouds to hang around along with a low chance of showers. Temperatures will return closer to normal, if not a little below. && .AVIATION /15Z TUESDAY THROUGH SATURDAY/... VFR conditions are expected through the TAF period. Few to scattered cumulus around FL060-FL120 are possible this afternoon as a dry cold front crosses. W/NW flow around 15 knots with frequent gusts to around 25 knots are most likely 13z-22z, though a few peak wind gusts of 28-33 knots are possible. MVFR or IFR ceilings are possible ahead of an approaching warm front Wednesday night into Thursday, along with the potential for a few showers, thunderstorms, and low-level wind shear. There is a lower/more conditional risk of showers or storms Thursday into Thursday night. Otherwise, mainly VFR is expected Wednesday into Thursday as flow becomes SE then S. Mainly VFR conditions expected Friday and Saturday with light south winds. The chance for thunderstorms will increase Saturday afternoon and evening, though coverage remains very uncertain at this time. && .MARINE... Westerly to northwesterly winds associated with a secondary/dry cold front will likely gust to around 25 knots, with perhaps a few gusts around 30 knots today into this evening. Gusty winds may persist much of the night, especially over the wider waters. Flow will become southeasterly then southerly Wednesday into Thursday as a warm front lifts north; gusts of 20-25 knots are possible due to channeling and a strong gradient despite warmer air over cooler water. In addition, a few showers and thunderstorms are possible late Wednesday through Thursday as the warm front lifts by. South to southwest winds are expected Friday into Saturday due to high pressure offshore. Small Craft Advisories are possible Friday into Friday night. With hot daytime air temperatures, stronger gusts may be over inland areas during the day, and over the main channel of the bay at night. Thunderstorm risk is low but not zero. && .TIDES/COASTAL FLOODING... Astronomical tides are high currently due to the recent full moon. Stagnant water levels will mean that DC SW Waterfront will be very close to minor flooding this morning. Northwest winds may bring a bit of a reprieve through Wednesday, but a return to southerly winds could mean sensitive sites once again approach minor flood stage Wednesday night into Thursday morning. && .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...Coastal Flood Advisory until noon EDT Wednesday for DCZ001. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory until 8 AM EDT Wednesday for ANZ530>533- 535-536-538>542. Small Craft Advisory from 8 PM this evening to 8 AM EDT Wednesday for ANZ534-537-543.
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&& $$ SYNOPSIS...DHOF NEAR TERM...LFR SHORT TERM...DHOF LONG TERM...ADS AVIATION...ADS/LFR MARINE...ADS/LFR TIDES/COASTAL FLOODING...

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