Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 211516 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 1116 AM EDT Wed Jun 21 2017 .SYNOPSIS... A frontal boundary dissipates over the local area today as an upper level disturbance passes just north of the region. Bermuda High begins to shift back towards the Eastern Seaboard this afternoon through Thursday. The high becomes centered off the Southeast Coast Friday and Saturday as low pressure moves through eastern Canada. && .NEAR TERM /THROUGH TONIGHT/...
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Latest analysis reveals diffuse frontal boundary draped just east of the central Appalachians this morning. To the north, a weakening cold front stretches from eastern New England to the Mason-Dixon line and back west into the middle Missouri Valley. Offshore, Bermuda high continues to slowly build toward the coast from this afternoon through tonight. Aloft, mid-level trough axis continues to edge east this morning, and will push offshore this afternoon. Disturbances just ahead of this feature which allowed for sct/numerous showers across the E-SE portions of the area have largely pushed offshore by late morning. Drier air aloft will push in from the west (and also in subsidence behind the trough), quickly diminishing rain chances for the afternoon. Given light flow and plenty of low-level moisture, have retained a slight to low end chance pop across the southeast. Dried things out tonight for the most part, with the exception being over the Northern Neck and Eastern Shore, where CAMs continue to depict some light shower activity in association with another very subtle shortwave pushing across. Kept 20-30% POP in for Iso to Sct showers over the NE corner of the CWA. Otherwise, partly to mostly clear with some patchy fog late, mainly away from the coast. Lows in the 60s to low 70s at the coast.
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&& .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... The Bermuda High continues to shift towards the East Coast on Thursday as TS Cindy makes landfall near the TX/LA Gulf Coast. An interesting weather pattern sets up as strong high pressure over the Desert SW creates an omega block with the Bermuda High in the east...effectively "trapping" TS Cindy in the middle. General model trends show shortwave energy ejecting from Cindy and getting pulled around the Bermuda High towards the Mid Atlantic Region during the short term periods. As the Bermuda High settles near the Southeast Coast Thursday night through Friday night, ample moisture and heat will be pumped into the local area... resulting in warm/muggy conditions. Highs Thursday in the lower 90s with dewpoints around 70F. Highs Friday slightly cooler with temps in the mid-upper 80s due to potential rainfall (see next paragraph); dewpoints in the lower 70s. Lows Thu/Fri nights in the 70s. Overall, Thursday should be dry for the local area. However, a constant stream of subtropical moisture from the Gulf and Atlantic should arrive late Thursday night as showers and steadily march across the region into Friday night. The general trend is for showers and thunderstorms to be ongoing Fri/Friday night. Pwats upwards of 2.00 inches will create the potential for moderate to heavy rainfall, which may also cause localized flooding. Given timing/placement differences between models and model runs, it is too soon to define these details attm. Will monitor closely over the next day or so. && .LONG TERM /SATURDAY THROUGH TUESDAY/... Lots of uncertainty in the extended range as models differ on handling strength and timing of several frontal boundaries along with the movement of now TS Cindy. The operational 12z GFS is strong and faster than the previous 06z run with a cold front that would sweep across the area on Saturday by 18z with the remnant of Cindy pushing through quickly ahead of the front. The 06z GFS was at least 6 to 12 hours slower and was weaker with the front. The 00z ECMWF was even slower than the GFS with the remnants of Cindy being left behind the initial frontal boundary, which stalls over the area on Saturday with the sfc low associated with Cindy getting pulled over the area Saturday night. A stronger secondary front arrives Monday and finally pushes the humidity off the coast by Tuesday. The WPC guidance is much closer to the ECMWF scenario and slower, which given the time of the year, makes sense as the frontal boundaries of late have struggled to make it through the CWA. So as a result, have held onto a mention of precipitation into the day on Monday, but the best chances for rain should be from Friday night into the day on Sunday as the remnants of Cindy increase the moisture over the region. I don`t think it is wet all the time, but expect some periods of showers with the best chance being during the day on Saturday into Saturday night. Temperatures are a challenge as well with cloud cover creating much of the uncertainty. While temperatures should drop a degree or two each day, clouds could certainly have an impact and either hold readings down more than expected or should the clouds break more than expected, readings could certainly jump. Right now, have readings in the upper 80s to low 90s on Saturday and gradually reduce highs on Sunday and Monday a couple degrees with the front in the area. By Tuesday, expect to see a stronger push of cooler and drier air which could get highs back down around 80. && .AVIATION /15Z WEDNESDAY THROUGH SUNDAY/... Light rain showers southeast of KRIC this morning will slowly shift eastward through today and are now expected to exit the coast across far SE VA/NE NC by late this afternoon. Thunderstorms could develop late morning/early afternoon due to daytime heating increasing instability aloft (despite plenty of clouds present). Overall, MVFR-VFR conditions should be anticipated invof showers (pockets of IFR CIGs 600-800ft AGL also possible) with VFR conditions north. As the front washes out over the area today, clouds may break up late this morning/early afternoon (mainly north). This should be short- lived as an upper level shortwave passes just north of the region later this afternoon. This will cause clouds to fill back in with light sprinkles possible across the Nrn Neck and MD/VA Eastern Shore (again due to daytime heating increasing instability aloft). All precip comes to an end this evening and skies scatter out as weak high pressure builds north of the region. Fog is likely to develop late tonight considering the saturated soils present from several days of rain. Winds will be too strong near the coast for fog formation, however low stratus may be possible. Will address these concerns with the 21/1200Z TAF issuance. Otherwise, fog will dissipate by roughly 22/1300-1400Z Thursday with dry weather and VFR conditions anticipated. Subtropical moisture moves into the region late Thursday night into the upcoming weekend. Showers and thunderstorms with moderate to heavy rainfall will be common beginning Friday. MVFR conditions are likely with periods of IFR during this time. This does not take into account the remnants of TS Cindy, however similar conditions are likely to persist if/when they impact the area. && .MARINE... High pressure off the Southeast coast will prevail today through Saturday. A weak boundary will approach from the north late tonight, but remain immediately north of the local marine area, and then depart to the northeast by Thursday aftn. A SW wind will mainly be 10-15kt today through Thursday night, with 2-4ft seas and 1-2ft waves in the Bay. A cold front will push into the Ern Great Lakes Friday and this will result in a tightening pressure gradient Friday aftn into Friday night. A SW wind will increase to 15-20kt, primarily for the ocean/Bay, with 4-5ft seas possible out near 20nm north of Parramore Island, hence a period of low-end SCA conditions are possible. The remnant low of TS Cindy may pass across the region later in the weekend. Not much wind should be associated with this system and the main threat should be an increased chc of showers/tstms. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...None. VA...None. MARINE...None. && $$ SYNOPSIS...MAM NEAR TERM...BMD/MAM SHORT TERM...ALB/BMD LONG TERM...ESS AVIATION...BMD MARINE...AJZ

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