Area Forecast Discussion
Issued by NWS Sterling, VA

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840 FXUS61 KLWX 201852 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 252 PM EDT Sun May 20 2018 .SYNOPSIS...
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A weak cold front will cross the area tonight and settle over the Carolinas on Monday. High pressure will build over the area on Monday. The front will return north as a warm front on Tuesday with a cold front expected to pass through the area on Wednesday. Weak high pressure will build over the area for the second half of the week.
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&& .NEAR TERM /THROUGH TONIGHT/...
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An isolated shower or t-storm will remain possible into early this evening as a weak cold front crosses the area. Otherwise, just sct-bkn cumulus clouds. Models now indicate the front will make it much farther south into southern VA and North Carolina on Monday leading to a dry day on Monday. Areas of fog are possible late tonight given strengthening mid-level subsidence and very wet/moist ground despite lowering sfc dewpoints/dry air advection.
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&& .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
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Sct-bkn mid-high level clouds Mon under sfc high pressure. Strengthening warm air advection pattern Mon night and Tue associated with front lifting north will bring another round of showers late Mon night into Tue evening with between a quarter to half inch of rain expected. Chance of elevated t-storms Mon night mainly west of the Blue Ridge. Things begin to dry out late Tue night as main shield of rain lifts to the east and cold front begins to push south.
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&& .LONG TERM /WEDNESDAY THROUGH SUNDAY/...
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A upper level trough over eastern Canada will slowly shift southward into Maine and New England on Wednesday. A surface low associated with the trough will settle over New England. A frontal boundary associated with the low will become stalled to the southeast of our county warning area. Both GFS 12Z and the 00Z Euro show a chance for showers moving through our region on Wednesday. Precipitation will be most likely on the western side of the Shenandoah mountains and our western parts of our CWA due to upsloping flow out of the west. The area should remain on the cold side but the front doesn`t look to shift out of the region until early Thursday as a upper level ridge shifts into the region from the west. Temperatures will hover in the upper 70s to mid 80s throughout the region. Thursday into Saturday, a upper level ridge shifts eastward over our region. A high pressure system will slowly shift eastward into our area from the Great Lakes. Skies will slowly clear and a southerly flow forms as the high pressure shifts eastward off the Atlantic coast on Friday. Temperatures will slowly build into the low 80s thursday and then rise up into the mid to upper 80s toward the end of next week. On Saturday, a cold front will approach from the west leading to stronger warm air advection into the region.
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&& .AVIATION /19Z SUNDAY THROUGH FRIDAY/...
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Patchy dense fog possible at KMRB late tonight, otherwise 3-5sm br at KCHO and KIAD. Showers return to the area late Mon night and Tue with possible flight restrictions. On Wednesday, a frontal boundary will be stalled to the southeast of the county warning area. A westerly to northerly flow is expected to the north of the boundary. Precipitation is possible which could lead to the dropping of both visibilities and ceilings on Wednesday. Thursday, skies begin to clear and winds look to remain mostly light.
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&& .MARINE...
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Winds should diminish below SCA by 22Z today then remain below SCA through Tue morning. Possible SCA Tue afternoon into Wed as winds turn southerly as warm front lifts through. A frontal boundary to the southeast of the CWA will lead to winds out of the west and the north. A northerly flow could lead to longer fetches and the need for small craft advisories. Thursday, skies are expected to clear as high pressure settles over the region. Winds should remain below Small craft advisor thresholds.
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&& .TIDES/COASTAL FLOODING...
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Moderate coastal flooding at Georgetown through 6PM this evening. Otherwise, minor coastal flooding expected at DC Waterfront and Georgetown into Monday afternoon.
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&& .CLIMATE... It has been an unusually wet pattern over the last week. For DCA (Reagan National), there has been at least 1/4" of rain each of the last 7 days. This is the longest streak on record. The previous longest was 5 days in 2011, 2009, 1975, 1950, 1942, and 1937. Precipitation records date back to 1871. && .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...Coastal Flood Warning until 6 PM EDT this evening for DCZ001. Coastal Flood Advisory from 6 PM this evening to 6 PM EDT Monday for DCZ001. MD...None. VA...Coastal Flood Advisory until 6 PM EDT this evening for VAZ054. WV...None. MARINE...Small Craft Advisory until 6 PM EDT this evening for ANZ530>543.
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&& $$ SYNOPSIS...LFR NEAR TERM...LFR SHORT TERM...LFR LONG TERM...JMG AVIATION...LFR/JMG MARINE...LFR/JMG TIDES/COASTAL FLOODING... CLIMATE...

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