Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 220641 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 241 AM EDT FRI JUL 22 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 THIS MORNING/... Latest wv imagery depicts a broad ridge extending from the central and srn Plains toward the Southeast/Deep South. To the north, 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, and will slide offshore overnight, with light onshore winds becoming S-SW overnight. Any lingering CU and rogue shower activity from earlier this evening have diminished with loss of heating. Have maintained a dry forecast overnight. Only adjustment to the forecast was to bump up clouds overnight in association with some remnant mid to high clouds from upstream convection over the Ohio Valley. These clouds will be thin enough that they`ll have minimal operational impact overnight, so forecast will average out at partly to mostly clear through Friday morning. Look for a mild night with early morning lows into the upper 60s to around 70. && .SHORT TERM /6 AM THIS 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/... 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. && .AVIATION /06Z FRIDAY THROUGH TUESDAY/... Surface high pressure has become centered well offshore over the western Atlantic, with more mixing of SSW winds than past several nights. This should preclude any fog development at TAF sites and have removed this from SBY. VFR/dry conditions to prevail today and Saturday with mainly S/SW winds around 10 KT. Isolated/scattered tstms possible Sat night at SBY, and then across southern VA and northeast NC Sun afternoon and evening. A cold front approaches on Monday and crosses the area on Tuesday bringing scattered showers and tstms both days...primarily during the afternoon/evening hours. Brief reductions in VSBYS and CIGS to MVFR/IFR levels with the storms. && .MARINE... S Winds currently avg around 10 KT across most of the area, with a few locations as high as 15 KT. Bay waves will average 1-2 ft with coastal seas 2-3 ft through early this afternoon. The pressure gradient will increase a bit more later today, and especially tonight, so S/SW winds will ramp up and average 15-20 KT during this period over much of the Bay and the coastal waters. With water temps in the 80s and a decent SSW low level Jet strengthening by tonight, should be a favorable enough setup for a southerly overnight SCA event in the Bay. Will be raising SCA headlines there with the 4 am issuance. Expect a few gusts in the rivers to approach 20 KT as well, but should be shorter lived and will allow next shift to evaluate need for a SCA there (as well as in the coastal waters off the VA/MD eastern shore for gusts to 25 KT and seas approaching 5 ft out near the 20 NM offshore areas). Waves over the Bay building to 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, with winds to avg < 10 KT and becoming onshore by afternoon with the seabreeze. Another front approaches from the NW early next week. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...None. VA...None. MARINE...None. && $$ SYNOPSIS...AJZ/SAM NEAR TERM...AJZ/MAM SHORT TERM...AJZ/SAM LONG TERM...TMG AVIATION...LKB MARINE...LKB is the U.S. government's official web portal to all federal, state and local government web resources and services.