Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 212047 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 447 PM EDT THU JUL 21 2016 .SYNOPSIS... High pressure prevails through the weekend, with heat returning Friday into early next week. Heat indices will climb to 100 to 108 degrees Saturday through Monday. The next cold front approaches the region late Monday. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... Current wv imagery depicts a broad ridge from the central and srn Plains through the Southeast states, with a trough pushing through the Great Lakes region and a lingering trough off the East Coast. At the surface, weak high pressure is situated over the Southeast and Mid-Atlantic. Temperatures this afternoon average in the mid/upper 80s across the area with dewpoints in the mid/upper 60s. Visible satellite imagery shows sct afternoon cu. A brief shower is possible over the Piedmont and along the sea-breeze. However, coverage will be very limited so forecast PoPs will be < 15% through the late afternoon. High pressure gradually slides offshore tonight with a light SE wind becoming SW. Lows drop into the upper 60s to around 70 under a mostly clear sky. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/... An anomalous upper ridge over the n-central US dampens and build ewd Friday through the weekend. 850mb temperatures warm to 20-22C (+2 st dev) by Friday afternoon. These values will support highs solidly in the low/mid 90s Friday. A deep well-mixed boundary layer combined with a SW wind around 10 mph will help dewpoints mix down into the mid/upper 60s resulting in heat indices no higher than the upper 90s. High pressure remains over the wrn Atlantic as pressure falls on the lee-side of the mountains induce a lee- side/thermal trough over the Piedmont. Limited forcing, a lack of moisture, and warm temperatures aloft should result in dry conditions. A weak trough slides across the area Friday night, but should only result in passing mid-clouds as forcing remains limited. Warm and humid with lows in the low/mid 70s. The airmass continues to warm Saturday resulting in highs solidly in the mid 90s inland. Dewpoints again mix down into the upper 60s over the Piedmont. However, dewpoints may remain in the low 70s over SE VA/NE NC and this will result in heat indices of 100-104. A weak frontal boundary clips the nrn Mid-Atlantic Saturday night. A 20-30% PoP has been introduced to the lower MD Ern Shore given some elevated instability and the presence of a shortwave trough within a NW flow regime. Warm and muggy with lows in the mid to potentially upper 70s. The frontal boundary stalls/dissipates over central/se VA/ne NC Sunday. This will result in highs in the low 90s Sunday over the Ern Shore. However, higher dewpoints should pool along the old boundary and highs remain in the mid 90s from inland VA to NE NC. This results in forecast heat indices in the 100-104 range from the Piedmont to the I-95 corridor to 105-108 over se VA/ne NC. An isolated tstm is possible in vicinity of the boundary, or along a sea/bay breeze. However, coverage will be very limited. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
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Not as hot acrs the region thru the extended period, with Mon and Tue being the hottest days in advance of a cold front approaching fm the NW. Unstable airmass combined with a lee trough ovr the area on Mon and a cold front pushing into and acrs the region on Tue will result in isolated to sctd showers and tstms. That frontal boundary will then become nearly stationary along the VA/NC border or just S of there ovr NC Wed thru Thu. So, the best chc for showers and tstms will be acrs the srn half of the area during this period. Highs in the lower to mid 90s Mon and Tue, in the upr 80s to lower 90s Wed, and in the mid 80s to lower 90s Thu. Lows will range thru the 70s Sun ngt and Mon ngt, and mainly in the lower to mid 70s Tue ngt and Wed ngt.
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&& .AVIATION /20Z THURSDAY THROUGH TUESDAY/... Surface high pressure settles over the western Atlantic and Southeast Coast through the weekend...resulting in primarily VFR conditions. Weatherwise, isolated seabreeze thunderstorms are possible near the coast this aftn/early evening. A brief period of shallow fog development is possible at KRIC and KSBY between 22/1000-1200Z. KECG may also experience shallow fog within this timeframe, however confidence is much lower and can be added as a tempo group if needed. Otherwise, conditions are dry on Saturday with another round of isolated to scattered storms possible across the area on Sunday. A cold front approaches the region on Monday and then crosses the area on Tuesday. There is enough incoming moisture to interact with a thermal trough on Monday and with the cold front on Tuesday to trigger a higher chance for scattered thunderstorms both days...primarily during the afternoon/evening hours. Locally heavy downpours, strong gusty winds, and brief reductions in flight conditions to MVFR/IFR ceilings and visibilities will be the primary impacts with thunderstorms early next week. && .MARINE...
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No headlines in the short term tngt thru Sat, though conditions may come close to reaching SCA thresholds Fri night. High pressure will slide offshore tngt and become centered off the mid-Atlc coast Fri, then a weak front approaches from the NW Fri night into Sat. This front looks to remain N of the CWA, with a pre-frontal trough in place over the region on Sat. Winds will be light from the E-SE (<10kt) this evening and transition to the S to average around 10 KT overnight into Fri morning. Bay waves will average 1-2 ft with coastal seas 2-3 ft. The pressure gradient will increase a bit by late Fri, especially by Fri night, so S/SW winds will ramp up and average around 15 KT during this period. A few gusts could reach SCA thresholds across the Bay (20 KT) and northern coastal waters (25 KT) Fri night, as warm water temps will be conducive to mixing the low level nocturnal Jet. Still would be marginal at best, with waves over the Bay building to 2-3 ft, and coastal seas to around 4 ft N and 3 ft S. The sfc trough/boundary drops into the area on Sat with lighter W/SW flow turning back to the S later Sat into Sat evening. The front then washes out/dissipates on Sun.
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&& .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...None. VA...None. MARINE...None. && $$ SYNOPSIS...AJZ/SAM NEAR TERM...AJZ SHORT TERM...AJZ/SAM LONG TERM...TMG AVIATION...BMD MARINE...TMG

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