Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 192310 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 710 PM EDT Wed Jul 19 2017 .SYNOPSIS...
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High pressure builds toward the Mid Atlantic into the weekend, bringing increasingly hot and humid conditions to the area. The hottest weather can be expected from Friday through Sunday.
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&& .NEAR TERM /THROUGH THURSDAY/...
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Radar rather quiet this evening compared to the past few days. What activity popped up is quickly dissipating including the tstms that were apprchg OXB/SBY from the north. Thus, went ahead and dropped pops except for the lwr MD eastern shore this evening. Otw, mainly clr. Lows upr 60s to mid 70s. PVS DSCN: The trough of low pressure (aloft) will continue to weaken and gradually shift south of the local area tonight and Thu as the upper ridge centered over the central/southern Plains begins to build east. With rising heights on Thu, and increasing 850 mb temperatures, expect high temperatures on Thu to be about 2 to 5 degrees warmer than Wed, ranging from the mid to upper 90s well inland to 90-95 closer to the coast (locally upper 80s immediate coast). To a varying degree, the models once again depict enough mixing of dew pts in the aftn on Thu for the NW 2/3 of the CWA (into the 60s). While dew pts will tend to remain in the 70-75 F range across the SE, temperatures will be a little cooler there so resultant heat indices look to peak in the upper 90s to 104 F at reputable sites. This will fall shy of heat advisory criteria (105 to 109 F) so will not be issuing any heat advisory headlines for now. Except for isolated sea breeze boundary induced showers or tstms Thu aftn, expect mainly dry conditions and will keep PoPs of 14% or less except near the coast (15-20% there).
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&& .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/... Model consensus has the upper ridge axis centered from the TN Valley to the Carolinas Fri into early Sat, with an upper trough over the Great Lakes and NE states on Sat. The core of the highest 850 temperatures on Fri (22-24C) will be over the NW portion of the CWA, shifting to the southern zones on Sat (22-23C). Fri may be the hottest day across the N high temps ranging fm the mid 90s to around 100 degrees. A heat advisory will be likely on Fri, as heat index values will be 103 to 108 degrees over most of the region. Sat may be slightly cooler and a bit more unstable as heights aloft drop, but should once again see highs of 95 to 100 F. Dew pts may be a little higher so heat indices should be at least as high if not higher. At least a heat adsy will likely be needed, possibly even excessive heat warning (especially for SE VA/NE NC). This is certainly not unprecedented heat for this part of the country during this time of year (see climate section), but it will be very hot nonetheless, and potentially dangerous for those not prepared for it. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... An upper level trough tracks across the Great Lakes and Northeast through the extended period, pushing a weakening cold front into the region during the Monday night to Tuesday morning time frame. Another hot day is forecast Sunday, but modest height falls and lower thickness values will knock a few degrees off. Highs in the mid to upper 90`s with heat indices back in the 105 to 108 range. Pressure falls ahead of the approaching from will sharpen the thermal gradient over the Piedmont, but a general lack of appreciable forcing, warm temperatures aloft, and westerly flow will result in only a slight chance POP over the Piedmont into central Virginia. Better chances (albeit 30-40% at this time) for diurnally driven showers/thunderstorms expected Monday as deep layer moisture increases ahead of the front and the upper trough tracks into the Northeast. Few degrees colder again, with highs generally in the mid 90`s and heat indices 100 to 105. Chance POPs continue into Monday evening as general model consensus drops the front over the local area Monday night. Strongest height falls progged north of the region, which result in cyclogenesis off the Northeast coast. The front likely stalls along the coast Tuesday, with chance POPs continuing across the southeast forecast area. Cooler, with highs in the upper 80`s to low 90`s. Thereafter, medium range guidance is at odds with handling the upper trough over southeast Canada. Prefer the more progressive ECMWF solution, which builds high pressure across the Northeast Tuesday, resulting in onshore flow and unsettled conditions over the local area. However, confidence is not high at this time, so have trended toward model consensus. Highs Wednesday in the mid to upper 80`s. Overnight lows through the period will generally be in the 70`s. && .AVIATION /00Z THURSDAY THROUGH MONDAY/...
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VFR conditions expected through the forecast period with only sct CU developing Thursday. Any fog tonight will be patchy at best and left out of forecast for now. S-SW winds below 10 kts. OUTLOOK...VFR conditions expected into the weekend, as high pressure builds toward the Mid Atlc region.
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&& .MARINE... Latest surface analysis depicts high pressure over the western Atlantic with a trough of low pressure over central Virginia. Winds are generally south to southeast at or below 10 knots. Waves generally 1 foot and seas 2 feet. Little change in the surface pattern expected through the weekend as high pressure remains entrenched over the western Atlantic and the storm track remains well north of the region. Thus, a prevailing south to southwest wind at or below 15 knots is expected through Monday. Winds increase slightly late each day into the overnight hours. Seas generally 2-3 feet and waves 1-2 feet. A weakening cold front approaches the region late Monday, dropping across the region Monday night into Tuesday morning. Flow backs to the northwest to north Tuesday at or below 10 knots due to a lack of cold advection. High pressure builds across the Northeast into Wednesday, resulting in onshore flow Wednesday. && .CLIMATE... Heatwave is expected to develop, mainly Friday through Sunday. The 2nd half of July is climatologically the hottest few weeks of the year so we still may not set any daily records at our main climate sites. For reference, record highs Thursday through Sunday are listed below: * Date: Thu(7/20) Fri(7/21) Sat(7/22) Sun(7/23) * RIC: 103/1930 104/1930 103/1952 103/1952 * ORF: 102/1942 101/1926 102/2011 103/2011 * SBY: 104/1930 106/1930 104/1930 103/2011 * ECG: 104/1942 102/1987 104/1952 104/1952 && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...None. VA...None. MARINE...None. && $$ SYNOPSIS...LKB NEAR TERM...LKB/MPR SHORT TERM...LKB LONG TERM...SAM AVIATION...MPR MARINE...SAM CLIMATE...AKQ

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