Area Forecast Discussion
Issued by NWS Sterling, VA

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580 FXUS61 KLWX 210116 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 916 PM EDT Tue Sep 20 2016 .SYNOPSIS...
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High pressure will build over the region through Thursday. A cold front will move through the area early Saturday. High pressure builds again over the region early next week.
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&& .NEAR TERM /THROUGH WEDNESDAY/...
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High pressure will continue across much of the Mid-Atlantic region tonight. A surface low will remain nearly stationary across the southern Outer Banks into Wednesday. Light northeast flow will continue tonight. Showers should stay across the southern Chesapeake Bay tonight. Mid-high level thin clouds are expected tonight across most of the region with the exception of southern MD and surrounding waters. Fog is expected to develop across low lying areas across the Shenandoah Valley and Central Foothills. Fog will be less widespread than last night however some visibilities may become less than a mile. Fog will taper off shortly after sunrise Wednesday. High pressure will move southward Wednesday and an isolated shower can`t be ruled out across the Central Foothills and Southern MD however chance is low as drier air moves southward Wednesday. Temps in the low to mid 80s expected.
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&& .SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/...
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Fog appears less likely Wed night as models show sfc dewpoints dropping Wed night. High pressure will continue to hold over the area with fair weather conditions.
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&& .LONG TERM /FRIDAY THROUGH TUESDAY/...
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Main weather story during the long term will be first real taste of autumn...as a cold front drops southward through the area Saturday. Friday into Saturday: Remaining warm prior to frontal passage, with highs 5-10 F above climatological normals. Dewpoints in the 60s will be just high enough for at least a hint of humidity. Moisture- starved cold front moves through the area during the day Saturday...with only a limited chance of precipitation (anything that manages to develop would be light and isolated). Sunday through Monday: Pleasant weather expected behind the front as high pressure builds into the area and dewpoints fall into the U40s/L50s. Temperatures also cool to near seasonable values with highs generally in the 70s and lows in the 50s/60s. Dry weather expected during this time. Tuesday: Next front approaches the region Tuesday. Quality moisture appears to be lacking again...so currently expecting limited precipitation chances.
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&& .AVIATION /01Z WEDNESDAY THROUGH SUNDAY/...
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Potential for fog development exists again tonight in Wednesday morning. Best chance will be across KMRB however confidence is low taking it down to LIFR at this time. At this time...MVFR vsbys expected at CHO and IAD with a chance at BWI. VFR conditions expected at DCA. VFR conditions expected Friday through the weekend as a mostly dry cold front passes through the area. Winds shift from southerly to northerly with frontal passage Saturday into Sunday.
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&& .MARINE...
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NE winds have been flirting with 18-20kts across the lower Tidal Potomac and adjacent Chesapeake Bay zones this evening. A SCA is in effect this evening. Winds are expected to diminish overnight and into Wednesday. NEly flow 10-15kt through Thursday as low pressure lingers along the Carolina coast. Winds forecast to remain below SCA values Friday. Winds could increase near SCA values near/behind cold front Saturday into Sunday.
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&& .TIDES/COASTAL FLOODING...
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Possible minor coastal flooding at Alexandria/DC this evening however tidal anomalies should decrease towards the high tide and therefore water levels should stay under flood stage. Confidence is low, so will closely monitor.
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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 2 AM EDT Wednesday for ANZ534-537- 543.
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&& $$ SYNOPSIS...LFR NEAR TERM...HAS/LFR SHORT TERM...LFR LONG TERM...MSE AVIATION...HAS/MSE/LFR MARINE...HAS/MSE/LFR TIDES/COASTAL FLOODING...HAS

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