Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 212000 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 400 PM EDT THU JUL 21 2016 .SYNOPSIS...
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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.
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&& .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
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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.
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&& .SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/...
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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.
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&& .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... A thermal trough is expected to remain in place Mon-Wed for continued very warm to hot conditions. 595dm upper ridge also remains situated off the SE coast. A slight buckle in the ridge across the Northeast/Mid- Atlantic due to a weak upper trough passage will knock a few degrees off max temps but still remain above normal. Highs in the mid/upr 90s Monday and low to mid 90s Tue/Wed. Thunderstorm chances will mainly be tied to the aftn/eve hours. && .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... Headlines are not anticipated over the next several days, though conditions may come close to reaching SCA thresholds Fri night. High pressure over the area today will slide offshore and become centered off the mid- Atlantic/SE coast Thu- Fri as 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 today will be light from the E-NE (<10kt) and transition to the S to avg around 10 KT tonight into Fri morning. Bay waves avg 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 avg around 15 KT during this period. A few gusts may reach SCA thresholds across the Bay (20 KT) and northern coastal waters (25 KT) Fri night as warm water temperatures 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 Sat night. The front then washes out/dissipates on Sun. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...None. VA...None. MARINE...None. && $$ SYNOPSIS...AJZ/SAM NEAR TERM...AJZ SHORT TERM...AJZ/SAM LONG TERM...JDM AVIATION...BMD MARINE...LKB

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