Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 180828 AAA AFDLWX Area Forecast Discussion...UPDATED National Weather Service Baltimore MD/Washington DC 328 AM EST Wed Jan 18 2017 .SYNOPSIS... A cold front will pass through the area this morning. High pressure will build toward the region today before settling overhead Thursday. A warm front will move into the area Friday and it will stall out nearby through Saturday. Low pressure will affect the area to start the new week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Warm front from yesterday has stalled overnight across the region, and have seen widespread dense fog develop on the cool side of the boundary, from about the DC metro on northward. At the same time, a cold front will continue pushing eastward across the area through the early morning hours. As it crosses, will see a wind shift to the northwest and a general drying trend as cool/dry air advection ensues. This should cause the fog erode and dissipate. Small/compact upper level low will then cross the region during the late morning/early afternoon hours. This combined with some lingering moisture and developing northwesterly flow will lead to a strato-cu deck of clouds, especially northeastern areas, with clearing developing by the afternoon for central VA. May also be a few isolated showers across Maryland as the upper low spins across. The northwest flow will also help to touch off upslope rain/snow showers, although with warm boundary layer conditions, any snow accumulations will be negligible. Peak wind gusts to the 20-30 mph range. Highs today quite mild, from 50-60F.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY NIGHT/... High pressure then builds in for tonight and Thursday with dry and mild conditions expected. Lows tonight in the 30s, with highs Thursday into the 50s again. Low pressure system will then push northeastward out of the Mississippi Valley and into the Lower Great Lakes Thursday into Thursday night before weakening on Friday. This will send an area of rain towards the Mid Atlantic states for Friday along the weakening warm frontal boundary. Current indications are that the highest chances of rain will fall in the 15z-21z (10am-4pm) time period for the DC Metro area. Rain will then taper off by the evening with clouds and possible areas of fog persisting Friday night. High temperatures Friday will range from the mid 40s north/east to low 50s south/west. Lows Friday night around 40F. && .LONG TERM /SATURDAY THROUGH TUESDAY/... A weak boundary will remain overhead for Saturday...but ridging overhead behind a departing disturbance should allow for dry conditions across most areas. Temperatures will continue to be above normal for this time of year. A potent jetmax in the southern stream of the jet will track into the Gulf Coast States Saturday night...forming a cutoff low. The low will track northeast into the Tennessee Valley and Mid- Atlantic Sunday before passing through our area Monday. Details with timing are uncertain this far out...but it does look like a soaking rain is likely Sunday into Monday. The low will slowly pull away from the area during the middle portion of next week. && .AVIATION /09Z WEDNESDAY THROUGH SUNDAY/... Widespread reductions early this morning in fog and low stratus will improve to VFR for most TAF sites by around 12z as a cold front crosses the region. Will see a strato-cumulus deck of clouds with bases from about 3000-5000 feet agl persist through the day, and this may cause occasional periods of MVFR, mainly at MRB. Otherwise, gusty northwest winds will develop with gusts up to about 25 knots. VFR will continue with winds slackening tonight and Thursday. Sub-VFR conditions then expected to develop again on Friday with period of rain and lowering ceilings as a warm front crosses the region. Low clouds and areas of fog may persist Friday night. Low clouds are likely for Saturday through Sunday. Areas of fog are possible Saturday morning. Rain chances will increase Saturday night into Sunday as low pressure approaches from the south. IFR/SubIFR conditions are most likely during this time. && .MARINE... Southerly winds will turn northwesterly as cold front crosses the region early this morning with gusts 20-25 knots expected today. Therefore, SCA is in effect through 6 PM. Winds will slacken tonight, however some gusts near SCA are still possible across the central Chesapeake Bay. Sub-SCA winds then expected Thursday through at least Friday night. A weak boundary will remain near the water Saturday. Low pressure will approach the waters Saturday night through Sunday before passing through Monday. A Small Craft Advisory will likely be needed for the waters during this time. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...Dense Fog Advisory until 4 AM EST early this morning for DCZ001. MD...Dense Fog Advisory until 4 AM EST early this morning for MDZ003>006-011-013-014-502>508. VA...Dense Fog Advisory until 4 AM EST early this morning for VAZ028-031-053-054-505-506. WV...Dense Fog Advisory until 4 AM EST early this morning for WVZ050>053-504. MARINE...Small Craft Advisory from 7 AM this morning to 6 PM EST this evening for ANZ530>532-535-536-538>541-543. Small Craft Advisory until 6 PM EST this evening for ANZ533- 534-537-542. && $$ SYNOPSIS...BJL NEAR TERM...MM SHORT TERM...MM LONG TERM...BJL AVIATION...BJL/MM MARINE...BJL/MM

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