Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 270042 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 842 PM EDT Thu Apr 26 2018 .SYNOPSIS...
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Low pressure will approach from the south tonight before passing through the area Friday. Another cold front will cross the region late Saturday. High pressure will build across the region Saturday night and hold through the middle of next week.
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&& .NEAR TERM /THROUGH FRIDAY/...
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Low pressure moving across northern Georgia is re-developing over central North Carolina this evening. This area of redevelopment will become the primary low tonight, lifting northeastward across southern Maryland Friday morning before departing to the northeast. Lift associated with this feature combined with an inflow of Atlantic moisture will lead to another period of rain tonight into Fri morning. Axis of heaviest rainfall as depicted by deterministic and ensemble guidance shows heaviest rains around an inch in central VA east of the Blue Ridge to right along the I-95 corridor from Fredericksburg north the southern DC suburbs. Some thunder is also possible late tonight and early Fri across central VA and southern MD. Rain will exit quickly by mid-morning Fri. Brief mist or patchy fog is possible in the wake of steadier rain. Will keep a risk of showers through the afternoon as additional shortwave energy moves across the area.
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&& .SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/... Upper low over the eastern Great Lks Saturday will push a cold front through the area Sat afternoon. Decent height falls will accompany this trof with scattered showers expected to develop along/ahead of the front. SREF calibrated tstm guidance shows only a slight risk of thunder mainly over PA and northern MD. Will keep thunder out of the fcst for now. Cdfnt will clear the area by late Sat., but a few showers could still persist into the night until trof axis crosses the area around 12Z Sun. && .LONG TERM /SUNDAY THROUGH THURSDAY/... A weak cold front will move through the region late Saturday into early Sunday. A few scattered showers are possible early Sunday but the frontal passage is looking fairly dry. Behind the front, a high pressure will build into the region from the midwest settling over our region on Monday. Skies on Sunday will slowly clear through the early afternoon periods. Temperatures will be hovering in the upper 50s to lower 60s. Monday through Wednesday, a high pressure system will slowly shift eastward off the coast of the Carolinas. A southerly to southwesterly flow will form leading to warmer air being advected into the mid-Atlantic region and northward. Temperatures throughout the next week will steadily rise up into the mid to upper 70s to lower 80s by Wednesday. Winds look to remain light along with light cloud cover due to a high pressure system influencing the weather through most of next week. && .AVIATION /01Z FRIDAY THROUGH TUESDAY/...
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Developing MVFR/IFR conditions late tonight into early Fri with rain/showers. Lowest CIGS looks to develop as steadiest rain departs. IFR generally 10-16Z. Cigs improve Fri afternoon. Sct showers expected again on Sat with a frontal passage. VFR conditions are expected through Tuesday as high pressure system settles over the region.
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&& .MARINE...
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SCA for lower MD portion of Chesapeake Bay/lower tidal Potomac River late tonight for a brief period of gusts on enhanced easterly flow immediately ahead of approaching low pressure. The low will depart to the northeast Friday. A cold front will approach Saturday, then exit the region by Sunday. SCA conditions are possible immediately ahead of and again behind the front over the weekend. A high pressure system will be in place Monday through early next week likely leading to Sub-SCA conditions.
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&& .HYDROLOGY...
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Enhanced easterly flow centered around 850 mb will result in strong moisture transport into the region overnight. Favorable easterly upslope areas in the central VA Blue Ridge mountains as well as central VA piedmont into southern MD will likely see the most rain. On average around an inch is forecast in these areas, with isolated totals of 1.5-2 inches possible in heavier convective elements. Some of the flashier basins only need 1.5 inches in 3 hours (which will be about the span of the heaviest rain in any one area) to flood. But due to the isolated nature of these flashier areas and more isolated significant rainfall totals, held off on a watch, but isolated flooding issues could still arise late tonight/early Friday morning, mainly across central VA east of the Blue Ridge.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory from 3 AM to 10 AM EDT Friday for ANZ534- 537-543.
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&& $$ SYNOPSIS...LFR NEAR TERM...LFR/DHOF SHORT TERM...LFR LONG TERM...JMG AVIATION...LFR/DHOF/JMG MARINE...BJL/LFR/DHOF/JMG HYDROLOGY...DHOF

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