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Area Forecast Discussion
316 FXUS62 KCHS 271708 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 108 PM EDT WED JUL 27 2016 .SYNOPSIS... Atlantic high pressure will prevail through the weekend while a weak trough persists inland. && .NEAR TERM /THROUGH TONIGHT/... The center of the expansive subtropical ridge will continue to stagnate right along the southeast U.S. coast providing a continuation of hot and humid weather with only spotty diurnal convection expected once again. Most areas will reach the mid to upper 90s this afternoon with the sea breeze progression slowed by a 15 kt west wind in the boundary layer during the morning hours. Forecast proximity soundings across inland areas indicate that low level dew points should mix out sufficiently during the afternoon. Peak heat indices along the near coastal sea breeze corridor may approach advisory criteria for a brief period during the mid/late afternoon hours. On average our forecast heat indices came out in the 105 to 109 degree range in the grids and daily heat safety precautions continue to be advised as this long duration hot weather pattern drags on. Convection allowing high resolution models are very scant on shower/tstm coverage this afternoon as anticipated with the high pres dome providing subsidence and quite warm temps aloft. We maintained a slight chance pops for a brief period this afternoon as soundings do show slightly better moisture profiles today and reasonable instability along the sea breeze corridor after mid afternoon. Most locations can expect a rain chance that is below 20 percent for today. Tranquil weather for tonight with very warm temps once again, probably similar to this morning. Skies should be mainly clear overnight after any evening debris clouds dissipate. && .SHORT TERM /THURSDAY THROUGH SATURDAY/... Strong ridging overhead and the associated subsidence will keep the mid and upper levels warm and dry through the end of the workweek. Only slight chance POPs included mainly along the resultant seabreeze Thursday afternoon, with mainly dry conditions expected Friday afternoon as the ridge shifts directly overhead, leading to the least impressive lapse rates and moisture profile of the period. Moving into Friday night, the ridge will begin to slide off the coast and the mid-levels will moisten/destabilize. POPs nudge closer to climo Saturday afternoon, near 30% focused along the sea-breeze corridor, though modest instability will keep the severe threat low. No relief from the heat will come this week, as high temps reach into the upper 90s for most away from the coast each day. With little to no downsloping component to the wind, triple digit highs seem unlikely at this point. Deep mixing will lower dew points into the upper 60s during peak heating daily, resulting in heat indices in the mid-100s for most. No heat advisories are anticipated at this time. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... West-southwesterly low level flow keeps a warm and humid airmass in place through the long term period. Increasingly unsettled weather will ensure as the ridge continues to slide off the Southeast coast and deep-layer moisture increases early next week. Global model solutions begin to diverge significantly heading into the middle of next week as a deteriorating cold front may approach the area Tuesday night into Wednesday. POPs have been increased well into the chance range, especially north of I-16, to account for this. Temps will remain at least a few degrees above normal through the period. && .AVIATION /17Z WEDNESDAY THROUGH SUNDAY/... VFR through 18Z Thursday. Extended Aviation Outlook: VFR will prevail at both sites. Brief flight restrictions possible with isolated afternoon showers/thunderstorms mainly over the weekend. && .MARINE... Persistence forecasting continues to drive the coastal waters forecast under the deep layer ridge and Atlantic surface high pressure. South to southwest winds will average 10-15 kt from late this afternoon into this evening, with 15-20 kt during peak nocturnal surges. Seas will average 2-3 ft. Thursday through Monday: Atlantic high pressure will prevail through the period with south-southwest winds mainly 10 to 15 knots and a 2 to 4 foot wind swell in the water. Isolated to scattered early morning thunderstorms will be a threat beginning Saturday. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$ SYNOPSIS... NEAR TERM... SHORT TERM... LONG TERM...CEB AVIATION... MARINE...