Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 011842 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 242 PM EDT Wed Jul 1 2020 .SYNOPSIS...
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An upper-level low will slowly move offshore from New England tonight through Friday. A weak backdoor boundary may approach the area during the weekend before dissipating early next week as high pressure strengthens over the Atlantic.
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&& .NEAR TERM /THROUGH TONIGHT/...
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Shortwave energy around an upper-level low over New England will pass through our area this afternoon into early this evening while a surface trough remains near central Virginia and southern Maryland. Daytime heating has led to an unstable atmosphere, with most of the instability east of the Blue Ridge Mountains, and the highest instability over southern MD into the VA Piedmont (latest mesoanalysis shows 1500-2500 J/KG of MLCAPE across these areas). The unstable atmosphere has led to popup showers and thunderstorms, and this will continue into this evening. The most widespread convection is expected over central Virginia into southern Maryland where low-level forcing will be a little stronger near the surface trough, and instability will be highest as well. A few severe storms are possible, with locally damaging winds and large hail being the primary threats. The best chance for a severe storm will be over southern Maryland into central Virginia where instability is highest. A strong to severe storm cannot be ruled out around the I-95 corridor near Washington and Baltimore, but confidence is lower due to less low-level forcing and slightly less instability. Farther northwest, coverage will be more isolated due to even less instability and no forcing. Convection will dissipate after sunset with the loss of daytime heating and subsidence behind departing shortwave energy. Patchy dense fog is possible late tonight with clearing skies and light winds.
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&& .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
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The upper-level low will continue to move offshore while upper- level ridging builds overhead for Thursday through Friday. A warming trend is expected during this time, with highs into the upper 80s to lower 90s Thursday for most areas and the lower to middle 90s for most areas Friday. Most of the time will be dry due to a capping inversion associated with the building upper- level ridge. A weak backdoor cold front may drop into the area late Friday or Friday night, and this may trigger a shower or thunderstorm. However, confidence is low at this time.
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&& .LONG TERM /SATURDAY THROUGH WEDNESDAY/...
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A weak backdoor cold front will stall out nearby Saturday and Sunday, but there will be little in the way of a temperature gradient with any marine air likely staying well off to the northeast. Therefore, more hot and humid conditions are expected with max temps in the lower to middle 90s each day. A weak wind shift from the boundary may be enough to trigger isolated to scattered showers and thunderstorms during the afternoon and evening hours from daytime heating. Forecast confidence in regards to exact location and timing of convection remains low at this time. We will continue to monitor forecast trends as we move closer to the weekend. A southerly flow will develop and bring higher humidity conditions into the region Monday and Tuesday. Threats for showers and thunderstorms will be focused moreso in the mountains and along the Blue Ridge. Highs will linger in the lower 90s. High pressure will be weak to approach on Wednesday. This day may be our drier day as we head into a more unsettled late week and weekend period.
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&& .AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
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Scattered showers and thunderstorms are expected into this evening. Brief IFR conditions are possible in convection along with gusty winds. The best chance for a storm will be across DCA, BWI, and CHO. Patchy fog is possible overnight into early Thursday, especially across KMRB and KCHO. VFR conditions are expected for Thursday and Friday along with light north to northwest winds. VFR conditions expected most of the time for Saturday through Monday. A few popup showers and thunderstorms are possible each day, especially during the afternoon and evening hours. Cigs/vsbys could briefly be reduced during times of convection.
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&& .MARINE...
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Sct-nmrs t-storms are expected into this evening. Storms may produce isolated strong wind gusts that require SMWs. Otherwise, onshore winds will be around 10 kt or less during this time. A north to northwest flow is most likely for Thursday and Friday, and winds should remain below SCA criteria for most of the time. No marine hazards expected Saturday through Monday. Winds generally north 5 to 10 knots through the period. Winds could become gusty in thunderstorms.
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&& .TIDES/COASTAL FLOODING...
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A light onshore flow has caused elevated water levels this afternoon. These levels will continue through tonight before an offshore flow develops for Thursday. Minor flooding is possible for sensitive areas around the preferred high tide late tonight into early Thursday morning. Confidence is too low at this time for advisories, but this will have to be monitored throughout the evening.
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&& .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && $$ SYNOPSIS...BJL NEAR TERM...BJL SHORT TERM...BJL LONG TERM...KLW AVIATION...BJL/KLW MARINE...BJL/KLW TIDES/COASTAL FLOODING...BJL

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