Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 221736 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 136 PM 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 /THROUGH TONIGHT/... Latest GOES water vapor imagery depicts a broad, anomalous ridge centered over the Southern Plains with a trough of low pressure over the western Atlantic. At the surface, high pressure remains centered well offshore, extending westward into the local area. Temperatures as of 10 am range from the low to mid 80s across the region with dewpoints in the low/mid 70s, with some sct cu pushing ewd off the coast and thin cirrus moving in from the nw. The upper ridge builds ewd today as 850mb temperatures warm to 20-22C (+2 standard deviation over the region. Expect temperatures to warm into the low to mid 90`s. A southwest wind around 10 mph will help mix dewpoints into the mid to upper 60`s today, outside of low 70s in the far se, resulting in heat indices of 95 to 100. A small convective complex is dropping sewd across wrn PA this morning, but is expected to dissipate before reaching the local area. Otherwise, pressure falls on the lee side of the mountains induce a lee/thermal trough today, but a lack of appreciable forcing, limited moisture, and warm temps aloft will keep the forecast dry. Expect some afternoon cumulus, especially across the southeast half of the area. A weak trough slides across the area tonight, but should only result in passing mid level clouds. Humid with lows in the low to mid 70`s. && .SHORT TERM /SATURDAY THROUGH SUNDAY/... The upper ridge dampens as it builds eastward through the weekend. 850mb temperatures remain in the 20-22C range (+2 standard deviations). Highs forecast solidly in the mid 90`s Saturday and Sunday. While winds will generally be less than 10 mph, soundings indicate deep mixing Saturday, which will help dewpoints drop into the mid to upper 60`s inland. Warmer dewpoints expected in the southeast, which will push heat indices into the 100 to 104 range. A weak frontal boundary clips the nrn Mid- Atlantic Saturday night. Have maintained chance POPs for the Eastern Shore given some elevated instability and the presence of a shortwave trough within a NW flow regime. Humid Saturday night with lows in the mid 70`s. The frontal boundary stalls/dissipates over central/se VA/ne NC Sunday. This will result in highs in the low 90s Sunday over the Eastern 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 /18Z FRIDAY THROUGH WEDNESDAY/...
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Surface high pressure has become centered well offshore over the western Atlantic. VFR/dry conditions to prevail through Saturday with mainly S/SW winds around 10 KT. Except will be during the 21Z through 06Z time frame, when an increase in S/SW winds is expected at KORF/KPHF/KSBY, with gusts perhaps reaching 20kt at KORF. Increased mixing should prevent any fog development again tonight. 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.
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&& .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. && .CLIMATE... While its certainly going to be hot Sat-Mon, climatologically this is the hottest time of the year with several heat waves having occurred in the past that have been far more intense than what we will experience. Record highs are unlikely to be set and in most cases, doubt they will even challenged within 5 degrees. * RECORD HIGHS: * Sat (7/23) Sun (7/24) Mon (7/25) * RIC: 103 (1952) 105 (2010) 105 (2010) * ORF: 103 (2011) 105 (2010) 105 (2010) * SBY: 103 (2011) 101 (2010) 100 (2010) * ECG: 104 (1952) 97 (2012) 99 (1949) && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...None. VA...None. MARINE...Small Craft Advisory from 6 PM this evening to 6 AM EDT Saturday for ANZ630>632-634. && $$ SYNOPSIS...AJZ/SAM NEAR TERM...AJZ/SAM SHORT TERM...AJZ/SAM LONG TERM...TMG AVIATION...LKB/WRS MARINE...LKB CLIMATE...

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