Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 210759 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 359 AM EDT Sat Apr 21 2018 .SYNOPSIS... High pressure over the Great Lakes will slowly move east into the Northeast U.S. by Sunday night. This high will move offshore Monday. A low pressure system will bring unsettled weather to the region Monday night through the middle of next week. && .NEAR TERM /THROUGH TONIGHT/... Skies are generally clear across the region thanks to broad high pressure over the Great Lakes region. There could be a few thin cirrus clouds streaming overhead. Winds are light out of the northeast to northwest across Maryland, eastern West Virginia and northeast to eastern Virginia. Winds are calm to the southwest. Temperatures range from near 30 degrees in parts of the western ridges to the lower to middle 40s along I-95 and the Chesapeake Bay area. A Freeze Warning remains in effect for the Shenandoah Valley and areas to the east, but just to the west of the heavily populated suburbs of Washington D.C. and Baltimore. Any frost overnight and early this morning will be patchy due to the dry low levels of the atmosphere. Quiet weather conditions expected much of this weekend as high pressure remains in control and gradually builds to the east from the Great Lakes to the Northeast U.S. Light winds and below normal temperatures are expected as a result. Additional middle and high clouds will move overhead this afternoon and linger through tonight. High temperatures should reach the lower to middle 60s this afternoon. With the additional middle level clouds and increasing low level dewpoint temperatures, we don`t anticipate freezing temperatures for a second night in a row tonight. Low temperatures will bottom out in the upper 30s to lower 40s. && .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... High pressure will continue to provide partial sunshine and tranquil conditions Sunday into Sunday night. High temperatures Sunday will reach the lower to middle 60s, while low temperatures will drop down into the middle 40s and near 40 in the western ridges and along the Mason-Dixon region. As the high pressure moves offshore Monday, winds will become more persistently from the southeast, bringing additional moisture into the region. A cut-off low pressure system will work its way up the East Coast from the Southeast U.S. to the Carolinas Monday and Monday night. Some rain should begin to overspread the region from southwest to northeast, beginning with the central Shenandoah Valley. Temperatures Monday could be just a few degrees below normal. && .LONG TERM /TUESDAY THROUGH FRIDAY/... Unsettled weather conditions expected Tuesday into Wednesday as low pressure over the southeastern U.S. and an upper level cutoff low over TN/KY nears our region. Rain chances will be increasing during the day on Tuesday from southwest to northeast as low pressure spreads northeastward. Models trending to favor the latter half of Tuesday before the rain moves in to the metro areas, with our far southwestern zones seeing activity pick up early Tuesday morning. Continued rain chances expected to persist in to the day on Wednesday as weak surface low pressure hovers near the Carolina coastline and mid level troughing starts to dampen a bit. This low pressure area will move off to the northeast during the day on Wednesday, bringing a downward trend to shower activity across the region. Another shortwave trough will approach from the west Wednesday night and Thursday as surface low pressure passes to our west, bringing additional moisture and isentropic lift across the area. Some model differences remain with regards to the strength of these features and ultimately the coverage/amount of rain during this time period. The stubborn mid to upper level troughing will hang around on Friday, as surface low pressure passes to our north, and a cold front looks poised to move through the Mid Atlantic region Friday night. Below normal temperatures will be maintained Tuesday and Wednesday with elevated moisture and increased cloud coverage, with a return to near normal temperatures Thursday and Friday, potentially breaking the 70 degree mark for portions of the area to close out the work week. && .AVIATION /08Z SATURDAY THROUGH WEDNESDAY/... VFR conditions expected through Monday with light and variable winds, becoming southeast 5 to 10 knots by Monday afternoon. MVFR conditions are possible at the CHO terminal Monday night with some light rain approaching from the southwest. Sub-VFR conditions expected Tuesday through Wednesday as a broad area of low pressure will impact the terminals with increasing rain chances. Heaviest rain and ultimately greatest flight restrictions will likely occur Tuesday night into Wednesday morning, where IFR/LIFR conditions will be possible. Increasing easterly breezes are forecast Tuesday into Wednesday, with gusts nearing 20 knots Tuesday. As the main area of low pressure starts to pull away from the area Wednesday, winds will abate a bit, backing out of the north northeast and turning light, with MVFR VIS/CIGs likely persisting into Wednesday night. && .MARINE... No marine hazards expected through Monday. Winds will be light and variable, becoming southeast around 10 knots by Monday. Small craft advisory conditions may be possible Monday night. Winds southeast becoming east 10 to 15 knots with possible gusts up to 20 knots. A broad area of low pressure will impact the waters Tuesday into Wednesday, with SCA conditions likely during this time period as a strong easterly flow develops across the area. As low pressure starts to move off to the northeast on Wednesday, sub-SCA conditions forecast to return for the latter half of the day. && .TIDES/COASTAL FLOODING... Persistent onshore flow is expected to result in increased tidal anomalies and possible coastal flooding during the middle part of next week. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...Freeze Warning until 9 AM EDT this morning for MDZ003>006-503- 505-507-508. VA...Freeze Warning until 9 AM EDT this morning for VAZ025>031- 038>040-051-501-502-505>508. WV...Freeze Warning until 9 AM EDT this morning for WVZ051>053. MARINE...Small Craft Advisory until 6 AM EDT early this morning for ANZ534-537-543. && $$ SYNOPSIS...KLW NEAR TERM...KLW SHORT TERM...KLW LONG TERM...BKF AVIATION...BKF/KLW MARINE...BKF/KLW TIDES/COASTAL FLOODING...DHOF

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