Area Forecast Discussion
Issued by NWS Sterling, VA

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163 FXUS61 KLWX 180226 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 926 PM EST Wed Jan 17 2018 .SYNOPSIS...
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A cold front will move offshore tonight as low pressure off the Carolina coast moves northeastward over the western Atlantic. High pressure will build south of the area through the weekend. A cold front may approach the area early next week.
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&& .NEAR TERM /THROUGH THURSDAY/...
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Temperatures this evening have dropped quickly in to the teens across our northern and western zones where skies are clear, winds have slackened a bit, and a snowpack exists. After seeing some decreasing in cloud coverage earlier this evening, clouds have filtered back in from the south over the DC metro area southward, likely in response to the mid to upper level trough swinging through our area. Low pressure developing off the Carolina coast overnight will deepen and race off to the east northeast over the Atlantic as the aforementioned trough moves east of our region. This will allow skies to clear for the entire CWA, except along the western Allegheny front, as temperatures bottom out in the teens for most, and near 20 degrees in the city centers. With gusty northwest winds overnight, but not as gusty as earlier today, wind chills will dip in to the single digits to below zero across the higher elevations and ridgetops. The ridgetops are expected to see wind chills of -10 to -20 tonight into Thursday morning, and a Wind Chill Advisory is in effect for these areas. Winds turn more westerly as strong warming commences aloft Thursday (850 mb temperatures rise from -5 to +5 C in about 12 hours). Despite this advection, dry W flow and subsidence behind an upper low to the east likely keep the region mainly sunny Thursday. Downsloping winds could push temperatures in the lowlands well into the 40s.
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&& .SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/... Undercut most guidance for temperatures Thursday night with clear skies and light winds and dew points still in the teens. BUFKIT soundings imply de-coupling at our usual ideal radiational cooling spots. A shortwave passing to the north could result in a modest increase in high clouds Friday, but no precipitation is expected. The moderating trend in temperatures will continue Friday with highs nearing 50 in many places. We will still be under the influence of high pressure, though, so with mainly clear skies and light winds Friday night, temperatures should again drop into the 20s. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... High pressure will continue to settle south of the region over the weekend. A draw of milder air from the south will allow for temperatures to at least reach the 50s. There could be a couple of rain showers in the western mountains as a weak front moves west to east Saturday night into Sunday. High pressure will move east Monday. A cold front will approach from the west and bring a chance of rain showers, mainly in the west and northern areas during the day. By Monday night, the rain shower threat spreads west to east. High temperatures likely reach the 50s once again. Cooler air will move into the region behind the system on Tuesday, with a decreasing chance of rain as high pressure builds back into the region. Highs will be in the 30s and 40s. Wednesday will be even cooler than Tuesday with high pressure reinforcing itself across the region. Highs will be 40s near the Bay but colder in the central and western areas. && .AVIATION /02Z THURSDAY THROUGH MONDAY/...
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Predominate VFR conditions forecast through Friday night as high pressure builds across the Ark-La-Tex region and eastward in to the southeast U.S. Northwest winds will abate a bit overnight, but regain their gustiness (17-20kts) Thursday morning, veering more westerly and diminishing to around 10 knots through Friday. VFR conditions Saturday through Sunday. Sub-VFR possible by Monday as a cold front approaches from the west. Winds light and southwesterly Saturday into Monday before increasing.
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&& .MARINE...
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In the wake of the frontal passage earlier today, gusty northwest winds have prevailed over our waters, resulting in SCA headlines. This gustiness will remain over the open waters overnight, before SCA gusts return for all waters during the day on Thursday. Winds should become light through Friday, and even though there may be a bit of a gradient at times between high pressure to the south and a shortwave passing to the north, waters will be cooler than the air and that should preclude mixing/SCA gusts. No marine hazards expected Saturday through Sunday night. Winds southwest to west 5 to 10 knots each period.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...None. MD...Wind Chill Advisory until 9 AM EST Thursday for MDZ501. VA...Wind Chill Advisory until 9 AM EST Thursday for VAZ503-504-507- 508. WV...Wind Chill Advisory until 9 AM EST Thursday for WVZ501-503-505- 506. MARINE...Small Craft Advisory until midnight EST tonight for ANZ530-531- 535-536-538>540-542. Small Craft Advisory from 8 AM to 4 PM EST Thursday for ANZ530- 531-535-536-538>540-542. Small Craft Advisory until 4 PM EST Thursday for ANZ532>534- 537-541-543.
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&& $$ SYNOPSIS...BKF/DHOF NEAR TERM...BKF/DHOF SHORT TERM...DHOF LONG TERM...KLW AVIATION...BKF/KLW/DHOF MARINE...BKF/KLW/DHOF

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