Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 210729 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 329 AM EDT TUE JUN 21 2016 .SYNOPSIS...
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A cold front over the eastern Great Lakes will move through the Mid Atlantic states this afternoon and evening. High pressure will pass to the north Wednesday. Low pressure will track to the north of the region Thursday. High pressure will return for the weekend.
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&& .NEAR TERM /TODAY/...
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03Z surface analysis showed low pressure over Quebec with an attendant cold front extending from Lake Ontario back across central IL. This will descend into the northern part of our forecast area late this afternoon/this evening. Temperatures will warm to around 90...hence there will be plenty of low level energy/CAPE. The approaching boundary will provide a focus for afternoon convection...with DC/Balt areas being the most likely target. Helicity is marginal. SPC has placed DC...MD south of Baltimore...the Highlands and almost all of the LWX part of VA in slight risk. Strong winds and large hail are the most prominent concerns.
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&& .SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/...
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Storms should be exiting the region during the evening as boundary tracks south and weakens. If areas outside of cities receive rain these will have a chance of patchy fog. Temperatures outside now are in the low/mid 70s. The upcoming night should be cooler - lows in the lower 70s in the cities/along the Bay...60s elsewhere. We will be "in between systems" Wednesday. Highs expected to reach the mid/upper 80s - right around climo norms. The next precip chance will be Wednesday night as an upper level short wave tracks across OH and into the northern Mid Atlantic. Low temperatures will be similar to Tuesday nights.
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&& .LONG TERM /THURSDAY THROUGH MONDAY/...
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After an active weather day Thursday, Friday and into the weekend will feature improving conditions under summer sunshine. Low pressure system will push eastward out of the Midwest and across the Mid-Atlantic states in west-northwest flow between large scale trough in SE Canada and large upper level ridge across the southern US Wednesday night and Thursday. Guidance has come into a general agreement of tracking the surface low across the PA/NJ/NY area during the day Thursday, placing the region in the warm sector following a warm frontal passage late Wednesday night/early Thursday morning. Will likely see an initial surge of some showers/thunderstorms with the warm frontal feature. Afterward, evolution becomes a little more tricky. Will likely see a robust CAPE field develop Thursday afternoon, with strong overlaying wind field, leading to the potential for strong to severe thunderstorms, especially along cold frontal boundary as low presses eastward. However what`s not clear is the role any ongoing potential convection (MCS) plays in the region`s eventual convective outcome. Also of note, is presence of deep westerly flow, which promotes downsloping and low level drying. High temperatures in the warm sector likely to be in the 80s to near 90F. Conditions should dry out for Friday, although a few lingering isolated showers/tstorms possible in the upper trough across the higher terrain. Heights then begin to buid Saturday and Sunday as ridge amplifies out ahead of a system ejecting from the central US and into Canada. Dry weather expected Saturday and Sunday. Next chance at any showers/storms will be Monday with trailing cold front from Canada-bound low. High temperatures in the low 80s Friday, with gradual warming each day, approaching 90F by next Monday.
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&& .AVIATION /07Z TUESDAY THROUGH SATURDAY/...
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VFR conditions this morning. Afternoon thunderstorms are possible...esepcially at the major airports. Strong gusty winds/hail will be possible...especialy in the 21 to 03Z timeframe. No problems expected tonight or Wednesday. Ceilings could drop to around 030 Wednesday night...and showers/thunderstorms will be possible. Showers and thunderstorms likely on Thursday with periodic Sub-IFR conditions. Some thunderstorms may become strong to locally severe with gusty winds and hail. Conditions improve to VFR for Friday and Saturday.
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&& .MARINE...
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Marginal SCA currently in effect on the lower Potomac/Bay. Winds are gusting to around 15 knots. SCA will be in effect for all waters today ahead of an approaching frontal boundary. Showers and thunderstorms...some with strong gusty winds...will be possible from mid afternoon through mid evening. SCA conditions likely Thursday/Thursday night on increased south/west flow with low pressure system. Showers/thunderstorms are also likely, possibly strong to locally severe. Sub-SCA conditions return for Friday and Saturday.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory until 4 AM EDT early this morning for ANZ530>534-537>541-543. Small Craft Advisory from 9 AM this morning to 6 PM EDT this evening for ANZ530>543.
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&& $$ PRODUCTS...WOODY!/MJM

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