Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 292020 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 420 PM EDT FRI JUL 29 2016 .SYNOPSIS... High pressure will continue to bring oppressive heat and humidity to the region through Saturday. The high will begin to break down beginning Sunday. A cold front will drop slowly across the area Tuesday into Wednesday bringing good chances for thunderstorms. Cooler temperatures will follow for the middle and end of next week. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... As of 330 PM Friday...Latest heat indices remaining running just below heat advisory levels most places. Drier moderate to strong westerly downslope winds were keeping sea breeze pinned closer to the coast with some minor backing to the SW expected through this afternoon as sea breeze becomes stronger. Therefore dewpoint temps were running several degrees lower than yesterday at the same time in places while 850 temps were running below 19c keeping overall temps a couple of degrees less than yesterday. Therefore, although it is hot, heat indices will remain just below 105 most of the day, which is below heat advisory thresholds. Overall high pressure ridge remains to the southeast and a Piedmont trough continues to the west. Cu field was developing and clustering mainly I-95 corridor and west with flatter cu along sea breeze boundary. Convective indices point to best chc of convection inland along trough or even farther west toward the mountains where better upper level support is. Otherwise could see isolated shwrs/tstms pulse up along sea breeze boundary mainly from Cape fear northward where best convergence and lift will be as winds back slightly in response to sea breeze this afternoon. The westerly steering flow will guide any shwrs/tstms east but expect them to dissipate as upper level ridging and drier air remain to the east. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY NIGHT/... As of 330 PM Friday...The heat indices will kick back up above advisory levels once again on Saturday. It appears the atlantic ridge may push back toward the northwest a bit with heights rising a bit and 850 temps up a couple of degrees, mainly eastern two thirds of area. Temps should reach the mid 90s for highs. Therefore we will once again issue heat advisories mainly I-95 corridor east where dewpoint temps will increase as aftn sea breeze draws atlantic moisture inland. The main focus for convection will be along Piedmont trough and along sea breeze boundary. The overall chance for convection will increase and may decrease the overall length of heat advisory, but for now, have issued it from noon to 8 pm. some needed rain and may temper some of the heat. By Sunday, Atlantic ridge gets pushed south and east a little farther as mid to upper trough makes a little headway east. The fight between the ridge and trough will be tricky in delineating the area of greater convective potential. Overall expect moisture to increase through the atmosphere and greater potential for convection mainly along Piedmont trough inland and sea breeze boundary. This should also keep temps from reaching heat advisory criteria with greater amount of clouds and shwrs/tstms. Temps should reach into the low to mid 90s on Sunday. && .LONG TERM /MONDAY THROUGH FRIDAY/... As of 300 PM Friday...Significant airmass change occurs...finally as the calendar flips to August. The tremendous heat and humidity through which we have been suffering will persist one last day Monday with highs in the 90s and high humidity once again, but a return to seasonable or even slightly below normal temps is forecast by mid week. The cause of this change is a sharp mid-level trough driving a cold front through the Carolinas Tuesday and Wednesday. Guidance is in agreement this front will slow across the area, but eventually will sink south of the region on Wednesday as the upper ridge breaks down. Guidance can frequently be too aggressive and quick with the breakdown of these ridges, so will lean on the slower solution and dissipate the front Wednesday just south of the area to blend with inherited, but much cooler temperatures are forecast Tue/Wed/Thu with a slow return to warmer temperatures possible late in the period. Along with these cooler temperatures, tstms should become more numerous Monday night through Wednesday associated with the fropa, decreasing back to seasonable POP at the end of the week. && .AVIATION /20Z FRIDAY THROUGH WEDNESDAY/... As of 18Z...VFR through the valid taf cycle. SCT040 in CU/TCU but upper ridge may suppress VCTS development. Any formation of TSTMS will be very isolated in scope. Winds W-SW 7-12 KT gusts to 19 KT between 18z-22z. WSW winds overnight 4-9 KT, increasing aft 15Z Sat to W-WSW 7g16 KT. EXTENDED OUTLOOK...Isolated to scattered afternoon convection Sunday and onward through the forecast will create fleeting and localized MVFR/IFR. Otherwise expect VFR. && .MARINE... NEAR TERM /THROUGH TONIGHT/... As of 330 PM Friday...Southwest winds will continue as the Bermuda High remains suppressed to the south of the coastal waters. The stronger westerly component to the wind has kept sea breeze pinned to the coast with winds basically 10 to 15 knots or less. Seas will continue to run 2 to 3 ft with 4 ft seas especially 10 miles off the coast with stronger off shore component. SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... As of 330 PM Friday...The Bermuda High and Piedmont trough will continue to be main players with a SW wind 10 to 15 knots through much of the period. As mid to upper trough pushes a cold front into North Carolina Sun night the gradient should tighten and winds will increase to 15 to 20 knots. Seas will remain 2 to 4 feet through the period. LONG TERM /MONDAY THROUGH WEDNESDAY/... As of 300 PM Friday...Bermuda high pressure remains dominant one last day Monday before a mid- level trough drives a slow moving cold front across the waters through mid-week. This causes a wind shift, so after 10-15 kts of SW winds on Monday, the gradient becomes diffuse as the front drops south and weakens, with winds gradually becoming NE at 5-10 kts by Wednesday. Highest seas will be Monday with the SE swell and SW wind wave producing 3-4 ft seas. Wave heights will fall slowly Tuesday, and then down to 2-3 ft Wednesday with a confused spectrum likely as a NE wind wave develops atop the residual SE swell. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...Heat Advisory from noon to 8 PM EDT Saturday for SCZ032-033- 039-053>056. NC...Heat Advisory from noon to 8 PM EDT Saturday for NCZ099- 105>110. MARINE...None. && $$ SYNOPSIS...JDW NEAR TERM...RGZ SHORT TERM...RGZ LONG TERM...JDW AVIATION...MJC MARINE...JDW/RGZ

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