Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 201849 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 249 PM EDT Sat May 20 2017 .SYNOPSIS...
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A cold front is positioned across southern Virginia. The front will return north into the area as a warm front late Sunday ahead of a cold front which will move through from the west Monday. High pressure will briefly return Tuesday before another cold front impacts the area Wednesday. High pressure will return for the end of the week.
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&& .NEAR TERM /TONIGHT/...
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Via a now-stationary boundary across southern VA and a 1032 mb high over Quebec Mid Atlantic has moved into somewhat of a CAD situation with a band of stratus setting up across PA into northern VA. If history is an indicator this will be hard to dislodge after sunset. Expect a mostly cloudy night with lows in the 50s. In the southwest portion of the forecast area...where there has been a decent amount of insolation and temperatures have risen to near 80...scattered convection is developing. RNK VWP is more representative of the wind field there than our radar. All the way to 30K ft the wind field is light. Brief heavy downpours will be possible. Thunderstorms will be possible through around 9 pm.
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&& .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
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Likewise the band of low level moisture will persist over the region Sunday keeping it cloudy and relatively cool. Highs around 70. Things will change Sunday night as a cold front reaches the Appalachians forcing the CAD-style cloud wedge to weaken but a line of showers/isolated thunderstorms to move through the area. Severe threat will be very low with this front as it will be coming through at night after a day with very little heating. Have upped PoPs to likely everywhere Sunday night. Precipitation chances will continue Monday as the cold front slowly works it way off the east coast. For the entire event QPF of 1/2" west to 1" east is possible. Precipitation should be ending in the west during the afternoon and east by evening. Improvement in sky condition is expected Monday night. Lows in the 50s except warmer in the cities and Lower Southern MD.
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&& .LONG TERM /TUESDAY THROUGH FRIDAY/...
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High pressure should keep the region dry Tuesday. The chance for rain showers return Tuesday night with a liklihood of rain showers Wednesday and Wednesday night as a broad storm system over the Ohio and Tennessee Valleys send pieces of energy our way from the southwest. The chance for rain showers or perhaps a rumble of thunder or two will linger Thursday and Thursday night as the main low pressure system decides to trek eastward toward the East Coast. Timing is uncertain as to how long it will take for the main low to move out of the area. There could be some leftover upper level energy overhead Friday. This could spawn a shower or two, mainly across the north and eastern areas. By Saturday, broad high pressure works its way into the region. Dry conditions and seasonable temperatures expected Saturday.
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&& .AVIATION /18Z SATURDAY THROUGH THURSDAY/...
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Cloud wedge hanging over the Mid Atlantic tonight. Ceilings high MVFR to low VFR. Some improvement in cloud heights is expected Sunday ahead of a frontal boundary. Sunday night should be wet with multiple showers..continuing into Monday morning. A return to VFR is expected late Monday and Monday night. Vfr conditions Tuesday. Winds light and variable. Mvfr conditions Tuesday night. Winds light and variable. Ifr to lifr conditions possible Wednesday and Wednesday night. Winds south 5 to 10 knots Wednesday becoming light and variable Wednesday night.
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&& .MARINE...
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Easterly flow over the waters this afternoon with scattered wind gusts into the SCA range across the central Bay and lower Potomac. SCA will remain in affect through 6 pm. Next possible SCA situation will be Sunday night ahead of a cold front and Monday behind the front. No marine hazards Tuesday through Wednesday night.
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&& .TIDES/COASTAL FLOODING...
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Easterly onshore flow has developed due to high pressure over eastern Canada. Flow turns southerly Sunday night as warm front lifts into the area. Water levels will gradually increase through Monday, with anomalies supporting elevated/minor coastal flooding at Annapolis, Straits Point, and DC by Sunday night.
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&& .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory until 6 PM EDT this evening for ANZ531>534-536-537-539>543. && $$ PRODUCTS...WOODY!/KLW

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