Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 130746 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 346 AM EDT Wed Sep 13 2017 .SYNOPSIS...
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High pressure over eastern New York will move offshore today. The remnants of Irma will move across the Ohio Valley today and into Pennsylvania Thursday. High pressure will return to our region during the weekend.
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&& .NEAR TERM /THROUGH TONIGHT/...
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Radar is showing a couple of light showers moving up from the south along I-95 and areas to the west into north-central Virginia. These showers could produce a few hundredths of an inch at best through daybreak. Additional rain showers are expected to develop between Richmond and Virginia Beach and move north into our region closer to Washington D.C. and toward Baltimore and northeast Maryland by morning rush hour. Elsewhere there will be some low stratus clouds or patchy fog in spots. As the rain showers move to the northeast and east out of our region during the morning and midday, we will encounter a few peeks of sunshine with high temperatures climbing up to near 80 or lower 80s. This evening will be predominantly dry with weak high pressure in control ahead of the last stage of the remnants of Irma. Models are indicating increasing clouds and chances of rain showers in the Potomac Highlands, mainly after midnight. These chances will proceed eastward to the I-81 corridor and the Shenandoah Valley by daybreak Thursday. Rain amounts would be generally between one tenth to one quarter of an inch and would be mainly in the northern Potomac Highlands, along the Mason- Dixon region.
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&& .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
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The chance for rain showers persists from west to east on Thursday with an introduction of a few thunderstorms along the Mason-Dixon region from around central Maryland east to the northern Chesapeake Bay and south to around the I-66 corridor. These thunderstorms should be isolated and pop-up Thursday afternoon due to daytime heating underneath a cool-core remnant low of Irma. Once evening approaches, any thunderstorms will lose their punch. High temperatures Thursday will be lower 80s mainly east of I-95, near 80 along and just east of the Blue Ridge, and middle to upper 70s to the west. The chance for lingering rain showers exist Thursday evening before a quiet period Thursday overnight arrives as the main cool-core remnant low slides to the east. Lows Thursday night will be cooler than Wednesday night. Models are indicating that a small piece of energy could wrap around the departing remnant low Friday and approach us from the north before departing to the east as well. For this reason, as well as our high temperatures reaching around 80 once again, we will allow for a chance of a few rain showers in parts of the region. Dry conditions should arrive once again Friday night as this final piece of energy slides to the south and east. Lows will be in middle 60s.
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&& .LONG TERM /SATURDAY THROUGH TUESDAY/...
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Extended forecast hinges on the fate of Jose. There is limited skill at track/intensity forecasts at this timeframe, which is only magnified by lack of run-to-run forecast consistency amongst model guidance. Latest official NHC forecast calls for this cyclone to loop toward coast but stay offshore through Sunday, which is what the local extended forecast will be based upon. That still wouldn`t preclude occasional 20-30% PoPs this weekend into early next week due to onshore flow, vort lobes and/or an approaching cold front.
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&& .AVIATION /08Z WEDNESDAY THROUGH SUNDAY/...
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IFR conditions at the CHO terminal due to a few rain showers and low clouds through daybreak. A couple of rain showers, approaching the MRB, IAD, and DCA terminals through daybreak, could drop conditions down IFR, as well. Winds east less than 5 knots through daybreak. IFR or perhaps MVFR conditions could persist through mid- morning due to lingering rain showers and low stratus clouds at the same terminals. BWI and MTN could encounter IFR conditions around mid-morning if rain showers pivot north into these areas. VFR condtions expected at all terminals this afternoon, tonight and into Thursday morning. Winds becoming south 5 to 10 knots today, then southwest around 5 knots tonight. MVFR or brief IFR conditions possible at MRB, IAD, DCA, BWI, and/or MTN Thursday afternoon due to isolated thunderstorms that could develop due to daytime heating under the remnant low of Irma. VFR conditions at all terminals Thursday night. Winds shifting northwest 5 to 10 knots Thursday, becoming light and variable Thursday night. VFR conditions for the most part on Friday at all terminals. There could be a shower around, but don`t anticipate too much in the way of IFR conditions. VFR conditions Friday night. Winds northwest around 5 knots Friday into Friday night. At this time, VFR conditions likely to prevail. However, would not rule out clouds coming onshore; there is low confidence in a stratus deck.
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&& .MARINE...
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No marine hazards expected today through Friday night. Winds east 5 to 10 knots today, becoming southwest 10 knots tonight. Winds shifting to the northwest around 10 knots Thursday through Friday. Winds should be mainly 10 kt or less this weekend due to a ridge of high pressure located near the waters. Clouds may be prevalent, and flow likely to be off the Atlantic. Some of these details still need to be determined.
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&& .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && $$ SYNOPSIS...KLW NEAR TERM...KLW SHORT TERM...KLW LONG TERM...HTS AVIATION...KLW/HTS MARINE...KLW/HTS

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