Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 141851 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 251 PM EDT Sat Oct 14 2017 .SYNOPSIS... High pressure over the area will weaken rapidly through Sunday. A cold front will push into the Mid Atlantic Sunday night followed by a return to high pressure early next week. && .NEAR TERM /THROUGH TONIGHT/...
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The back edge of the eroding cloud deck has made it to MRB-GAI- EZF. Based on these trends and most recent mesoscale guidance, am hopeful that skies will partially clear areawide, except for maybe the tip of southern Maryland. However, the boundary layer will still have ample moisture, making for a situation where redevelopment likely after dark...either low clouds and/or fog. Am leaning a bit heavy on radiational cooling/fog at this time, but could easily see cloud development instead per BUFKIT NAM profiles. Tranquil conditions will otherwise prevail.
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&& .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
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Southerly flow will increase ahead of a cold front Sunday. Any low clouds or fog that does form will have a much better chance at eroding during the morning hours. Advection and insolation will allow temps to rise back above 80 degrees. The cold front will pass through the area Sunday night. The best support will come from low-level convergence and thermal advection. Showers should result, but am not sold on a solid or prolonged period of precip, and have back POPs down accordingly. The pressure surge that follows Monday will bring gusty winds and cooler temperatures. Some upper 30s possible in outlying areas by Monday night.
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&& .LONG TERM /TUESDAY THROUGH SATURDAY/...
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High pressure will promote dry conditions Tuesday through Saturday. Tuesday`s high temperatures and Tuesday night`s low temperatures will be about 5 degrees below normal. Wednesday and Thursday will warm up to near or slightly above normal with plenty of sunshine each day. Friday and Saturday are expected to be warm with sunshine. Highs each day in the middle to upper 70s.
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&& .AVIATION /18Z SATURDAY THROUGH THURSDAY/...
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Clouds eroding across the metro hubs and MRB this afternoon. Will go from a BKN deck 015-020 straight to SCT VFR. With plenty of moisture left in the boundary layer, anticipate either clouds redeveloping or thick fog forming where it doesnt. Currently, forecast is leaning toward the fog scenario, but could easily see low clouds instead. Either way, expect IFR (or lower) after midnight through the morning push. Mixing will be better tomorrow, so flight restrictions should dissipate quicker. VFR by mid-morning through the rest of the day. Some G20kt gusts likely. Cold front will cross through the terminals Sunday night. Associated flight restrictions should be fleeting. Best bet would be for briefly lower cigs. Monday, perhaps as early as predawn, northwest winds will increase. That would be the only potential flight restriction, due to NW flow G20-25 kt. VFR and decreasing winds Monday night. VFR conditions Tuesday through Wednesday night. Winds light and variable each period.
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&& .MARINE...
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Winds mostly 10 kt or less this afternoon, with the prevailing direction from the north. Should have light winds tonight, with increasing south flow on Sunday ahead of a cold front. Have a Small Craft Advisory in effect for all waters Sunday afternoon/early evening (started a little earlier for the Bay/lower Potomac). The threat likely will continue through Sunday night on the Bay and mouth of the Potomac. Confidence not as high, but Advisories have been extended accordingly. A cold front will cross the waters Sunday night. There may be a bit of a lull in the mixing during the rain/wind shift. Mixing will then improve Monday. Although not continuous, Small Craft conditions likely on Monday as a result. No marine hazards Tuesday through Wednesday night.
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&& .TIDES/COASTAL FLOODING...
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Water levels running about a foot above astronomical normals. Only potential issues will be with the upcoming high tide at St George Island and SW Washington DC. In both cases, the minor threshold may barely be reached; Advisories are in effect, but confidence diminishing. Water levels should decrease over the next couple of days. No other issues anticipated at this time.
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&& .CLIMATE...
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A surge of warm air is expected Sunday ahead of the cold front. We are not currently forecasting records, but we are expecting temps to be close. Warm Temperature Records for October 15 (Sunday)... High Warm Low DCA 87 (1975) 67 (2008) BWI 86 (1989, 1975) 66 (1941) IAD 88 (1989) 64 (1985)
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&& .EQUIPMENT... The NWS 88D Sterling radar (KLWX) will be down through at least 5 PM today. This is for nationally scheduled maintenance on the radome. Surrounding WSR-88D radars as well as FAA Terminal Doppler radars will provide coverage during this downtime. && .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...Coastal Flood Advisory until 6 PM EDT this evening for DCZ001. MD...Coastal Flood Advisory until 1 AM EDT Sunday for MDZ017. VA...None. WV...None. MARINE...Small Craft Advisory from 10 AM Sunday to 6 AM EDT Monday for ANZ530>534-537>543. Small Craft Advisory from noon to 8 PM EDT Sunday for ANZ535- 536.
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&& $$ SYNOPSIS...LFR NEAR TERM...HTS SHORT TERM...HTS LONG TERM...KLW AVIATION...HTS/KLW MARINE...HTS/KLW TIDES/COASTAL FLOODING...HTS CLIMATE... EQUIPMENT...HTS

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