Area Forecast Discussion
Issued by NWS Sterling, VA

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057 FXUS61 KLWX 011816 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 216 PM EDT Fri Jul 1 2016 .SYNOPSIS... A cold front will pass through the area tonight. High pressure will build over the area for Saturday into Saturday night. A warm front will move into the area Sunday into Sunday night...and a wave of low pressure will ride along the boundary and pass through our area Monday into Tuesday. High pressure may return for the middle portion of next week. && .NEAR TERM /THROUGH TONIGHT/... A Severe Thunderstorm Watch is in effect for locations along and east of the Blue Ridge and Catoctin Mountains through northern Virginia. The watch is in effect until 10 pm this evening. High pressure remains over the Atlantic and a cold front will approach the area from the Ohio Valley late this afternoon and evening. A southerly flow ahead of the boundary has resulted in warm and humid conditions...which will lead to an unstable atmosphere. The most instability is located near and east of the Blue Ridge Mountains ahead of a pressure trough where dewpoints will be in the upper 60s/lower 70s has resulted in MLCAPE values around 1500-2000 J/KG. An upper-level trough will dig into upstate New York through this evening and this will cause deep layer shear profiles to strengthen. 0-6 KM bulk shear will be around 40 knots. The pressure trough will act as the primary lifting mechanism for showers and thunderstorms to develop. The combination of moderate to strong shear along with high instability enhances the threat for severe thunderstorms. The primary threats will be damaging wind gusts and large hail from Multicell clusters and/or Supercells. An isolated tornado cannot be ruled out...especially if there is an easterly component to the surface wind from a bay/river breeze. The best chance for severe thunderstorms will be along and east of the pressure trough that will setup near the Blue Ridge and Catoctin Mountains between 4 pm and 8 pm this afternoon and evening. The cold front will pass through the area late this evening and drier air will move in behind the boundary overnight. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... High pressure will build overhead for Saturday into Saturday night...bringing dry conditions along with low humidity. There will be some high clouds in the zonal flow aloft. A warm front will build north into the area Sunday into Sunday night. Warm advection and isentropic lift will lead to more clouds along with an increasing chance for showers. The best chance for showers will be late Sunday into Sunday night. && .LONG TERM /MONDAY THROUGH FRIDAY/... A storm system will ride along a warm front across the Ohio Valley Monday and Monday night. Showers and thunderstorms will develop along the front and accompany the storm system. Showers and thunderstorms will linger Tuesday along an associated trailing cold front. If any showers remain Tuesday night, they would most likely be focused over the Potomac Highlands and central Shenandoah Valley. As the main storm system moves off the East Coast Tuesday night, a brief area of high pressure will build into the eastern half of the region for Wednesday and Wednesday night. There is a chance for a few showers in the Potomac Highlands Wednesday night. The threat for showers and thunderstorms, again, will be expected Thursday through Friday as the pattern remains active. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/... Thunderstorms will impact the terminals late this afternoon into early this evening. A few thunderstorms may be severe...with damaging winds and large hail being the primary threats. Cigs/vsbys may briefly drop to IFR levels in heavier thunderstorms. Drier air will move in overnight and VFR conditions are expected through Saturday night with high pressure in control. A warm front will return for Sunday...bringing the chance for some showers and possible subvfr cigs. The best chance for showers and subvfr cigs will be Sunday night. Ifr conditions expected Monday and Monday night with showers and thunderstorms. Winds south 5 to 10 knots Monday and Monday night. && .MARINE... Thunderstorms may impact the waters this afternoon into this evening. Damaging wind gusts and large hail will be the primary threats. High pressure will build in behind a cold front overnight and northwest winds are expected. A small craft advisory is in effect for the Maryland Chesapeake Bay and lower Tidal Potomac River overnight through Saturday morning. Winds should decrease later Saturday into Saturday night as high pressure builds overhead. A warm front will move into the waters Sunday and a wave of low pressure will ride along the boundary...passing through the area Monday into Tuesday. Showers and thunderstorms are possible during this time...especially Monday into Monday night. High pressure may return for the middle portion of next week. && .TIDES/COASTAL FLOODING... Tidal anomalies are running about a half foot above normal this afternoon. Water levels will stay below flood stage however will reach action stage at sensitive locations at Annapolis, Alexandria and DC SW/Waterfront during the high tide cycle late this afternoon and evening. Will have to monitor tidal anomalies during the higher of the two high tides overnight...but offshore flow should be developing. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory from midnight tonight to noon EDT Saturday for ANZ530>534-537>543. && $$ SYNOPSIS...BJL NEAR TERM...BJL SHORT TERM...BJL LONG TERM...KLW AVIATION...BJL/KLW MARINE...BJL/KLW TIDES/COASTAL FLOODING...BJL is the U.S. government's official web portal to all federal, state and local government web resources and services.