Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 290122 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 922 PM EDT SAT MAY 28 2016 .SYNOPSIS... An area of low pressure, associated with Tropical Storm Bonnie, will come ashore along the Carolina coast, and then move slowly northeastward over the next couple of days. A trough axis will pass through the area on Monday. High pressure will build for the middle of the week. A cold front will push through the region at the end of the week. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... Surface high combined with ridging aloft over the eastern portions of the US have continued to not only keep the area warm, but also provide a shield from any thunderstorms. There are still a few thunderstorms developing west of the Allegany Front. Per the latest RAP, these storms should dissipate by midnight. That is in keeping with the going database, which was based on activity dropping off after sunset with the loss of diurnal heating. Still think dry conditions will prevail through the night. RAP/HRRR both support that position. Increasing moisture in the low levels could result in patchy fog, and have expanded that possibility beyond typical, climo-favored valleys. However, high clouds may interfere with its development. && .SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY NIGHT/... Increasing coverage in rain and thunderstorms Sunday. As previously mentioned, latest guidance showing that the rain will reach the area slightly slower than previous runs indicated. TD 2 nearing the SC coast this afternoon is expected to be right along the coast by Sun morning, then slowly progressing nearly parallel to the coast into the first part of the coming week. Please refer to NHC products for the official forecast. Also to monitor during this time is an approaching trough across the northern US. As energy from the low to the south swings around the western side of the ridge aloft, it becomes sandwiched between the ridge to the east and this approaching trough from the west. There remains some question exactly where this energy becomes trapped, but the latest guidance shows to be right across the Mid- Atlantic. This will aid in enhancing further shower and thunderstorm development across the CWA. Moisture advection will increase Sun from the low to the south and combined with the aforementioned features, the potential exists for moderate to periods of heavy rain. With the overall flow on the lighter side and the potential of training activity, will continue to highlight flooding potential in the HWO. At the moment can not pinpoint exactly where, but the latest thinking is that the heaviest band sets up between the Blue Ridge and Chesapeake Bay. The rain will continue into Monday, especially over eastern areas. Subsidence builds in later in the day with the next ridge nudging in from the west so should see precip cutting off over western areas with a possible dry period over the east before the remnants of the low finally move north mid week. && .LONG TERM /TUESDAY THROUGH SATURDAY/... Upper level ridging starts building up on Tuesday and a low pressure system stalls over the North Carolina coast through Thursday. Moisture advection from this system will depend on its location... but guidance is showing that showers and thunderstorms are possible over our CWA from Tuesday into Thursday. A cold front approaches from the west on Friday and moves across Friday night into Saturday, continuing with the chance of showers and thunderstorms during this period. Upper trough approaches the eastern CONUS during the weekend. High temperatures will be in the upper 70s and low 80s before the cold front... in the 70s for Saturday. Low temperatures will be in the 50s and 60s. && .AVIATION /01Z SUNDAY THROUGH THURSDAY/... VFR conditions through at least the first half of tonight. Possible patchy fog dropping vis to 3-5SM late tonight, around daybreak. Rain moves in generally late tomorrow morning into Sun afternoon. With the heavier rain later in the day comes sub-VFR conditions in both the cigs and vis, lasting into Sun night. IFR may be possible by Monday morning, which later forecasters will need to consider. Improvement back to VFR returns during the day on Monday. Winds less than 10 knots through the period, southerly becoming easterly. VFR conditions expected for Tuesday through Thursday...with some showers and thunderstorms possible bringing brief periods of sub- VFR conditions due to a low pressure system to our southeast. && .MARINE... Southerly flow continues on the waters this evening. However, speeds are just below Small Craft Advisory criteria, and should remain so through the night. As tropical rainfall heads north on Sunday, mixing will become increasingly poor. Therefore,sustained winds through Sunday night should remain less than 10 kt. Winds will become northwesterly on Monday as a trough axis passes through. At this point, the pressure gradient still looks weak. Sub-SCA conditions expected Tuesday as winds will be below SCA criteria. Showers and thunderstorms possible during the waters during this period with low pressure system to our southeast. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && $$ SYNOPSIS...HTS NEAR TERM...HTS SHORT TERM...Sears LONG TERM...IMR AVIATION...HTS/Sears/IMR MARINE...HTS/Sears/IMR is the U.S. government's official web portal to all federal, state and local government web resources and services.