Area Forecast Discussion
Issued by NWS Sterling, VA

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866 FXUS61 KLWX 180028 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 828 PM EDT Sat Jun 17 2017 .SYNOPSIS... A very warm and moist air mass will remain in place through Monday until a cold front clears the area Monday night. Weak high pressure will build over the area for the middle of next week. && .NEAR TERM /UNTIL 7 AM SUNDAY MORNING/...
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A few showers and thunderstorms left out there this evening but coverage is considerably less than on previous nights. These should weaken/dissipate over the next several hours. Overnight, there will be a mix of clearing and debris clouds leftover from the day`s convection. There may also be some lower stratus that tries to develop overnight, with the highest chances over northern/central Maryland as well as the Potomac Highlands/Shenandoah Valley. In areas that see some clearing, there may also be some fog development, especially any location that saw rain today. However continued light southerly flow should preclude a more widespread dense fog. Otherwise a warm and muggy night with lows from the mid 60s to mid 70s.
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&& .SHORT TERM /7 AM SUNDAY MORNING THROUGH MONDAY NIGHT/... A cold front will move through the Midwest and into the Ohio Valley Sunday. Somewhat drier air aloft and a stronger capping inversion will allow for more sunshine Sunday after low clouds and fog burn off. A south to southwest flow along with more sunshine will cause hot and humid conditions with max temps in the upper 80s and lower 90s across most locations. The hot and humid conditions will lead to an unstable atmosphere. The heat and humidity should be enough to break the capping inversion during the afternoon and evening hours. Isolated to scattered thunderstorms are expected. Coverage may not be as widespread as recent days...but shear profiles will be noticeably stronger. Therefore...a few thunderstorms may become severe especially west of the Blue Ridge Mountains where 500mb heights will be a bit lower and shear will be strongest. The cold front over the Ohio Valley will approach western portions of the CWA Sunday night. Additional showers and thunderstorms are possible ahead of the boundary...especially across western portions of the CWA. More warm and humid conditions are expected Sunday night ahead of the boundary. The cold front will slowly pass through the area Monday into Monday night. Shear profiles will continue to strengthen as the upper-level trough associated with the cold front digs over the Ohio Valley and Midwest. A south to southwest flow ahead of the cold front will continue to usher in very warm and humid conditions. The unstable atmosphere...along with forcing from the cold front will lead to showers and thunderstorms. Strong shear profiles suggest that there is an enhanced threat for severe thunderstorms with damaging winds being the primary threats due to unidirectional winds with height. Copious amounts of moisture will also cause thunderstorms to contain heavy rainfall. A shear vector nearly parallel to the cold front suggests that training convection is possible. This elevates the threat for flash flooding despite the faster storm motion expected. The best chance for severe storms with heavy rain will be during the afternoon and evening hours east of the Allegheny and Potomac Highlands. The cold front will move off to the east by Tuesday morning and convection should dissipate overnight behind the boundary. && .LONG TERM /TUESDAY THROUGH SATURDAY/... Weak high pressure will build toward the region Tuesday and Wednesday while an upper-level trough builds overhead. Drier and less humid conditions are expected along with seasonably warm temperatures. A couple popup showers and thunderstorms cannot be ruled out though due to the upper-level trough overhead. A nearly zonal flow aloft develops Thursday through Saturday. Most of the jet energy should remain to our north...which puts our area on the warm side of a nearly stationary to our north. More hot and humid conditions are possible along with increasing chances for showers and thunderstorms. && .AVIATION /00Z SUNDAY THROUGH THURSDAY/...
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A few showers and thunderstorms this evening will dissipate overnight. Coverage is isolated to scattered and most sites will not see any impacts. Overnight, VFR at all sites to start, however, there may be a low stratus deck that develops late tonight and lasts into Sunday morning. This has the potential to bring MVFR ceilings for about a 3-6 hour period. There may also be some patchy fog around which may bring visibility reductions. A cold front will then approach from the west Sunday. A few showers and thunderstorms are possible during the afternoon hours into Sunday night. The cold front will pass through Monday and there is a better chance for showers and thunderstorms. Some thunderstorms may be severe. Weak high pressure will build over the terminals during the middle portion of next week.
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&& .MARINE...
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A southerly flow will continue through tonight. A Small Craft Advisory is in effect for the Chesapeake Bay and middle/lower Tidal Potomac River for gusts up to about 20 knots. A cold front will approach the waters Sunday and Monday before passing through Monday night. South to southwest winds will increase during this time. A Small Craft Advisory is in effect for all the waters Sunday and Sunday night and will likely need to be extended into Monday and Monday night. Popup showers and thunderstorms are expected Sunday afternoon and evening. Locally gusty winds are possible in stronger thunderstorms. More widespread thunderstorms are expected later Monday into Monday night. Severe thunderstorms are possible during this time with damaging winds being the primary threat. Weak high pressure may build over the waters behind the boundary for the the middle portion of next week...but the boundary will stall out nearby.
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&& .TIDES/COASTAL FLOODING... A southerly flow has developed over the waters today. Tidal anomalies are around one foot above astronomical norms. The southerly flow is expected to strengthen through tonight and the southerly flow is expected to continue through Monday. Tidal anomalies will likely increase a bit in response to the strengthening flow. Minor tidal flooding is likely for Straits Point and Annapolis with the high tide cycle tonight. A Coastal Flood Advisory is in effect for St Marys County and Anne Arundel Counties. Minor tidal flooding is possible with the high tide cycle tonight for other sensitive locations...but confidence is too low for an advisory at this time. Minor flooding is also possible Sunday and Monday as the southerly flow continues. && .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...None. MD...Coastal Flood Advisory until 3 AM EDT Sunday for MDZ014. Coastal Flood Advisory until 11 PM EDT this evening for MDZ017. VA...None. WV...None. MARINE...Small Craft Advisory until 6 AM EDT Monday for ANZ530>534- 536>543. Small Craft Advisory from noon Sunday to 6 AM EDT Monday for ANZ535.
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&& $$ SYNOPSIS...BJL NEAR TERM...BJL/MM SHORT TERM...BJL LONG TERM...BJL AVIATION...BJL/MM MARINE...BJL/MM TIDES/COASTAL FLOODING...BJL

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