Area Forecast Discussion
Issued by NWS Sterling, VA

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KLWX 171945 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 345 PM EDT Fri Aug 17 2018 .SYNOPSIS...
-- Changed Discussion --
A cold front will slowly approach from the northwest and Saturday, then gradually cross the region Saturday night into Sunday. High pressure will briefly dominate Monday before another system approaches towards the middle of next week.
-- End Changed Discussion --
&& .NEAR TERM /THROUGH SATURDAY/...
-- Changed Discussion --
Latest surface analysis depicts high pressure dominating the western Atlantic and a slow moving frontal boundary extending from New England southwest across the Great Lakes into the Corn Belt. Aloft, a ridge dominates the western Atlantic east of Florida while a closed low is over Chicago. Tonight, the front will slowly slip southeast toward the region, but should remain outside the CWA. However, ample CAPE combined with limited shear and passing shortwave energy combined with falling heights is resulting in decent storm organization across our western zones, and this will likely translate east or northeast through the rest of the afternoon into the evening. Damaging winds are the main threat, but hail is possible with the strongest cores. Storms should gradually weaken late this evening and overnight as they continue moving northeast, with the overnight hours turning out mostly quiet. Lows will remain warm, with 70s common. The cold front will slowly slide southeast towards the region on Saturday, but will remain north of the CWA through the day. Thus, we will remain unstable, and with the upper low opening into a trough and passing to the north, more storms look likely. It should start quiet in the morning as well, likely aiding to destablization, though at this point expect less CAPE due to greater cloud cover. Otherwise, flash flooding and gusty winds look to remain a threat. Highs will be a bit cooler than today, but should approach 90 in much of the area.
-- End Changed Discussion --
&& .SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/...
-- Changed Discussion --
Front slowly crosses the area Saturday night and Sunday, and trough axis passes late Saturday night, so overall, expect less activity on Sunday. However, lingering instability may still generate some showers and a thunderstorm or two on Sunday. Highs will be cooler, with 80s common. By Sunday night, some clearing should take place as high pressure builds southward into the area. Lows will drop into the 60s.
-- End Changed Discussion --
&& .LONG TERM /MONDAY THROUGH FRIDAY/...
-- Changed Discussion --
On Monday, a upper level trough will exit the region to the east. Behind the trough, a weak upper level ridge will build into the region from the west. A frontal boundary is forecast to stall off to the south of the region becoming a focus for precipitation. A high pressure will try to build over the region. The region is expected to see a brief dry period on Monday but showers can`t be ruled in the southern parts of our CWA. Tuesday into Wednesday, a upper level trough will approach from the west early on Tuesday. A warm front will move northward through the region creating a southerly flow and transport warm and moist air into our area. Thunderstorms and showers will be possible on Tuesday especially later in the day as a cold front approaches from the west. These storms have the potential to be severe and cause localized flooding due to PWAT values over two inches. The cold front is expected to finally move through our region early Wednesday morning. Showers and storms will be possible Tuesday night into Wednesday morning with showers lingering through Wednesday morning. The best location for showers on Wednesday will be on the west side of the Blue Ridge due to a westerly flow creating upslope induce showers. Daytime high temperatures are expected to be seasonal below average in the upper 70s and low 80s. On Thursday, a high pressure system will build over the region and linger through the early parts of the weekend. Day time high temperatures look to remain below average in the low 80s. Winds will be light out of the north.
-- End Changed Discussion --
&& .AVIATION /19Z FRIDAY THROUGH WEDNESDAY/...
-- Changed Discussion --
Mainly VFR through Sunday night, but scattered showers/t-storms will present issues with low cigs/low vis/lightning and gusty winds, primarily during the afternoon and evening hours. Some reductions in vis/cig possible during the late night/early morning hours due to fog development, most likely at MRB/CHO but possibly at IAD/BWI as well. On Monday, skies will remain mostly cloudy with only scattered showers expected.Winds will be light out of the east northeast. VFR conditions are likely at this time. On Tuesday, a frontal boundary will approach from the west. Showers and thunderstorms will be possible with mostly cloudy skies. Winds will be light out of the south. The transport moisture into the region will lead to increasing cloud cover. SubVFR conditions will be possible especially within storms.
-- End Changed Discussion --
&& .MARINE...
-- Changed Discussion --
Pressure gradient increasing ahead of an approaching cold front will result in SCA conditions this aft into early Saturday. In addition, scattered t-storms this aft/even may result in gusty winds, with the need for special marine warnings. As the front slowly crosses the region on Saturday and Sunday, the gradient should diminish, but scattered t-storms will again be possible each day. Skies should remain mostly cloudy Monday with light winds out of the west to northwest. A few showers will be possible over marine areas near central Virgina. Isolated showers will be possible. A cold front will approach from the west Tuesday. Thunderstorms and showers will be possible with winds out of the south. A southerly flow could lead to a channeling effect which may lead to wind gusts above 15 to 20 knots.
-- End Changed Discussion --
&& .LWX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory until 10 AM EDT Saturday for ANZ530>543.
-- End Changed Discussion --
&& $$ SYNOPSIS...RCM NEAR TERM...RCM SHORT TERM...RCM LONG TERM...JMG AVIATION...RCM/JMG MARINE...RCM/JMG

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.