Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 200107 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 907 PM EDT Thu Apr 19 2018 .SYNOPSIS... An unseasonably strong area of high pressure will migrate across the Great Lakes and into the northeastern U.S. Friday into the weekend, then move offshore early next week as low pressure approaches from the lower Mississippi River valley. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... As a cold front moves farther away to the southeast, the pressure gradient is lessening and winds are diminishing gradually. The same can be said for the stratocumulus clouds. Moisture is decreasing rapidly enough that the chance for any snow showers in the mountains is coming to an end as well. A Freeze Warning has been issued for much of the area between I-95 and I-81. Winds likely stay up for most areas tonight (10 knots or so), but 925 mb temperatures drop to -3 to -5 C which should correspond to surface temperatures at or a little below freezing at the surface. Temperature trends and model guidance don`t support any changes to the headline this evening. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/... Canadian high pressure will build north of our area from the Great Lakes on Friday. Sunny and breezy conditions are expected with wind gusts generally in the 20 to 30 mph range. Winds will diminish in the evening as high pressure moves closer and the gradient relaxes. Light winds and clear to mostly clear conditions are expected Friday night. May need to watch temperatures again for possible freezing conditions, mainly over the Shenandoah Valley and northern Maryland. Pleasant but somewhat cooler than normal conditions are expected Saturday into Saturday night as the high slowly moves by to the north of the area. && .LONG TERM /SUNDAY THROUGH THURSDAY/... High pressure centered over the eastern Great Lakes/Northeast will continue to dominate our weather on Sunday bringing dry conditions and slightly below normal temperatures to the region. By Sunday Night, models have a cutoff upper-level low and associated surface low tracking through the Deep South. Deterministic models diverge significantly with the handling of this system. The deterministic GFS moves this system up the east coast and into our CWA by Monday Night. The GEFS support the operational GFS solution, suggesting that a period of rainfall may be possible Monday Night through Tuesday with this system. This differs significantly from the 00z Euro, which keeps the system stalled out to our south until Wednesday, when it is picked up by a trough approaching from the Midwest. The 00z European ensembles showed a wide range of solutions, suggesting that uncertainty is high with this event. Generally speaking, Monday appears to be mostly dry and an unsettled period of weather will be likely sometime in the Tuesday through Wednesday period. However, exact timing and details remain up in the air. Regardless of what happens with the upper-level cutoff, it appears as though some precipitation will be possible on Wednesday as an upper-level trough swings in from the Midwest. && .AVIATION /01Z FRIDAY THROUGH TUESDAY/... VFR through Saturday. Remain stratocumulus clouds around 5kft should be dissipating after midnight as high pressure builds to the north from the Great Lakes. Gusty NW flow should remain below 30 kt, potentially becoming 10 kt or less at times tonight. Gusts may peak around 25 kt Friday morning before diminishing through the afternoon, then becoming light N Saturday. VFR conditions are expected for the weekend into Monday. Sub- VFR conditions are possible Monday Night through Wednesday as an area of low pressure approaches the region from the south. && .MARINE... There are still a few gale force gusts on the Bay this evening, but observational trends and model guidance suggest the warning will be able to be dropped for most if not all waters by evening`s end. A Small Craft Advisory follows into Friday with northwest flow gusting 20-25 kt at times. Winds are expected to fall below Small Craft Advisory criteria Friday night and remain light through the weekend. Sub SCA conditions are forecast to persist into early next week as a ridge of high pressure should keep winds light. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...Freeze Warning from 2 AM to 9 AM EDT Friday for MDZ003>006- 503>508. VA...Freeze Warning from 2 AM to 9 AM EDT Friday for VAZ025>031- 036>040-050>053-055-056-501-502-505>508. WV...Freeze Warning from 2 AM to 9 AM EDT Friday for WVZ051>053. MARINE...Small Craft Advisory until 6 PM EDT Friday for ANZ531>533-536- 537-539>541. Gale Warning until 11 PM EDT this evening for ANZ531>533-536- 537-539>541. Small Craft Advisory until 6 PM EDT Friday for ANZ530-535-538- 542. Small Craft Advisory from 6 AM to 6 PM EDT Friday for ANZ534- 543. Gale Warning until 6 AM EDT Friday for ANZ534-543. && $$ SYNOPSIS...IMR/DHOF NEAR TERM...ADS/IMR/DHOF SHORT TERM...IMR/DHOF LONG TERM...KJP AVIATION...ADS/IMR/DHOF/KJP MARINE...ADS/IMR/DHOF/KJP is the U.S. government's official web portal to all federal, state and local government web resources and services.