Area Forecast Discussion
Issued by NWS Sterling, VA

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771 FXUS61 KLWX 190100 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 900 PM EDT Tue Jul 18 2017 .SYNOPSIS...
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Upper-level low will move away from the area tonight into Wednesday. High pressure will then build in for later Wednesday and Thursday, followed by the potential for additional disturbances Friday and into the weekend. Temperatures will be on the rise through the week with hot and humid conditions expected.
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&& .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
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Upper-level low remains centered just to the south and a pressure trough is currently located near the Blue Ridge Mountains. A southerly flow will continue to usher in warm and humid conditions tonight. MIn temps will range from the 60s in the Allegheny and Potomac Highlands to the mid 70s in downtown Washington and Baltimore. Isolated showers and thunderstorms are possible through late this evening. The best chance for a shower/storm will be to the north and west of Interstate 95...closer to the pressure trough. Also...an outflow boundary from previous convection remains over this area. Similar to last night, there is potential for patchy fog, especially in areas that see rainfall today.
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&& .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/... Upper trough will continue to slowly pull away on Wednesday as ridging builds in from the west. Thus, while a few isolated showers/storms are possible, most places should remain dry. Temperatures will be on the rise, with highs in the low to mid 90s. This combined with dew points near 70F will lead to heat indices around 100F or so east of the Blue Ridge and in the mid/upper 90s west. Quiet weather expected Wednesday night, but warm and muggy with lows in the 70s. Partly to mostly sunny skies expected for Thursday, with temperatures topping out again in the low-mid 90s, but will likely be even a couple degrees warmer than Wednesday. Some model guidance depicting a light westerly flow which may bring dew points down some, but not a given at this time. Heat indices again near or perhaps above 100F in some locations. Warm and muggy conditions continue Thursday night, with lows 70s to near 80F in the urban centers. && .LONG TERM /FRIDAY THROUGH TUESDAY/... A front should sag across the region Friday and Friday night bringing a chance for showers and thunderstorms. High temperatures will be in the middle 90s across much of the region. As the front stalls across the central portions of our region Saturday and Saturday night, the threat for additional showers and thunderstorms are expected. Highs will once again reach the middle 90s in many areas. The front will move north of the region as a warm front Sunday into Sunday night. Showers and thunderstorms will develop along and north of the front. Most of the activity should be focused across Maryland and northern Virginia. Highs will reach the middle to upper 90s with high heat indices during the afternoon. The heat lingers Monday and so do the chances of showers and thunderstorms as a cold front approaches from the west later in the day. The cold front could push through the area Monday night, bringing one final round of heavy showers and thunderstorms. High temperatures will be in the lower to middle 90s. On Tuesday, a broad ridge of high pressure will build in from the west. The heat and humidity will be elevated with highs in the middle 80s. && .AVIATION /01Z WEDNESDAY THROUGH SUNDAY/...
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VFR overall through the next few days. Overnight tonight, similar to last night, there will likely be some patchy fog around, although coverage/density is uncertain at this time. Winds mostly 10 knots or less. There is a possibility for a few isolated thunderstorms Wednesday as well, but risk lower compared to recent days. Mostly VFR, although with potential for showers and a few thunderstorms Friday through Sunday. Heavy downpours and gusty thunderstorms are possible in any storms. Winds generally less than 10 knots.
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&& .MARINE...
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Southerly winds will be close to SCA criteria through late this evening across the Maryland Chesapeake Bay and lower Tidal Potomac River. Otherwise, wind speeds should remain below SCA criteria most of the time through Thursday. There is a possibility for a few isolated thunderstorms Wednesday afternoon and evening. No marine hazards expected Friday through Sunday. Winds west- northwest around 10 knots Friday and Friday night. Winds becoming southwest 5 to 10 knots Saturday into Sunday.
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&& .TIDES/COASTAL FLOODING...
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South flow will maintain elevated water levels through Wednesday night. Water levels are expected to remain just below minor coastal flood thresholds during the afternoon/evening preferred high tide. However...it will be close for Annapolis overnight and this will have to be monitored.
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&& .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && $$ SYNOPSIS...BJL/MM NEAR TERM...BJL/MM SHORT TERM...MM LONG TERM...KLW AVIATION...BJL/MM/KLW MARINE...BJL/MM/KLW TIDES/COASTAL FLOODING...MM/BJL

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