Area Forecast Discussion
Issued by NWS Wilmington, NC

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469 FXUS62 KILM 220133 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 933 PM EDT Fri Jul 21 2017 .SYNOPSIS... Hot and humid conditions will prevail today through the weekend with only isolated rain chances. Storms will increase next week as a series of weak fronts approach the coast, with near normal temperatures for late July. && .NEAR TERM /THROUGH SATURDAY/... As of 915 PM Friday...Diurnally driven convection along the Piedmont trof basically dissipated by and just after sunset. Do not expect any convection this evening thru the overnight. Skies basically clear except the far NW portions of the FA where convective debris clouds will slowly scour out during late this evening and overnight. Min temps will basically run in the mid 70s with upper 70s to near 80 along the immediate coast due to a partially onshore SSW-SW flow having crossed adjacent SSTS that are in the 80-85 degree. Previous....................................................... As of 645 PM Friday...Quick update issued to account for isolated convection drifting into the NW portions of the ILM CWA thru sunset. Previous...................................................... As of 300 PM Friday...Steep low level lapse rates have combined with just enough low level moisture to pop some cu throughout the forecast area, especially along the sea breeze boundary where moisture advecting in off the ocean provides a little more fuel. However, it is very dry above 850 mb so still looks like the remainder of today will be a dry one with only the odd spot shower or thunderstorm possible. Best chances for anything look to be well inland in closest vicinity to the persistent thermal trough. As this is all diurnally-driven, expect overnight to be clear and dry with lows in the mid 70s. Similar story for Saturday, with diurnally-driven slight chance POPs at best during the afternoon and early evening. It is possible that a heat advisory may be required for heat index values of 105F or higher, but confidence is not high enough at this time for issuance. A consensus of guidance has actual temperatures for Saturday much the same as today, with highs from around 90 near the coast to the mid 90s inland. && .SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/... As of 330 PM Friday...Overall expect hot and humid weather with heat advisory conditions over most of area on Saturday. A Broad trough in the mid to upper levels extends just far enough south into Carolinas as to prevent strong ridging to build in from west or east to push temps high enough for any record heat, but enough to produce temps a good 3 to 7 degrees above normal. Temps should reach into the mid 90s over most of the area. Temps overnight will remain well into the 70s most places. SW sfc winds around Bermuda High will become quite gusty Sun aftn into Sun eve as sea breeze and trough inland become more pronounced, and should see winds increase further Sun night as trough pushes east and tightens pressure gradient. Both the Atlantic ridge and strong ridge over central CONUS seem to exert enough influence with enough dry air and subsidence to keep area mostly rain free, but with with troughing inland and decent sea breeze on Sunday, can not rule out an isolated shower Sat night into Sunday. By Sun night, the mid to upper trough begins to dig a bit more south and a shortwave rides by as well as a disturbance moving up the coast from the south. This will all lead to better chc of shwrs/tstms late Sun into Mon. && .LONG TERM /MONDAY THROUGH FRIDAY/... As of 300 PM Friday...A shortwave trough moving through New England on Monday night, and a large upper low developing across southern Quebec late in the week will help put a dent in the heat. Falling upper level heights associated with these systems will shift the core of the upper ridge (and its associated heat) farther west into Texas and New Mexico. Don`t expect a cleansing frontal passage by stretch, (06Z GFS ensemble 850 mb temps don`t fall below climatology next week) but at least we should lose the 100+ heat indices for a few days. Both the GFS and ECMWF show a cold front moving into northern North Carolina on Tuesday. The GFS then sinks the boundary a little farther south by Wednesday morning. There are enough GFS ensemble members showing the front making it into South Carolina that I`m leaning toward the GFS in this case. This front should enhance the coverage of t-storms Tuesday night and Wednesday, and I`ve placed my highest forecast PoPs (50-60 percent) of the extended period during this period. With a progressive upper level pattern to our north, surface high pressure will push off New England and out into the western Atlantic Thursday and Friday, probably with enough southerly wind developing over the Carolinas to lift the front or its remnants back to the north. && .AVIATION /01Z SATURDAY THROUGH WEDNESDAY/... As of 00Z...High confidence with VFR conditions across all terminals during the 24 hr TAF issuance period. The only fly in the ointment will be the possibility of BR across the inland terminals during the 08Z to 12Z timeframe. If winds stay decoupled long enough and the sfc temp/dewpt spread drops below 2, then the possibility increases. For now, will keep the fog out of the fcst due to latest model mos guidance keeps the sfc dewpoint depression at 3 degrees or hier during the Sat early morning hrs. Given the isolated convection that developed along the Piedmont trof today, expect this to likely re-fire again during Sat aftn and evening. As a result, will include VCTS for the inland terminals. Winds this evening and overnight inland will become SW less than 5 kt and occasionally may go calm especially across the LBT terminal. Across the coastal terminals, look for the demise of the sea breeze circulation with S-SSW 10 to 15 kt winds diminishing and veering to the SW around 5 kt by or just after 04Z. Will repeat the sea breeze circulation process again during Sat with winds backing to S-SSW around 10 kt by midday and increasing to 10 to 20 kt during the aftn and evening. Extended Outlook...VFR through Sunday. Brief MVFR/IFR possible in scattered showers and tstorms Mon and Tue due to a slowly approaching cold front from the NW. && .MARINE... NEAR TERM /THROUGH SATURDAY/... As of 915 PM Friday...Strong ridging from high pressure centered well offshore and the Piedmont trof across the central Carolinas will result with a slow tightening of the sfc pg tonight thru Sat. Look for SSW-SW winds 10-15 kt g20 kt tonight that will increase to 15 to 20 kt with g25 kt, especially near shore due to a healthy inland progressing sea breeze. Significant seas will run 2 to 4 ft tonight and build to 3 to 5 ft thruout by late Sat thru Sat night. Power-wise, a 1 to 2 foot ESE ground swell at 7 to 8 second periods will dominate over the wind driven waves at 4 second periods. During Sat and Sat night, the wind driven waves at 4 to 5 second periods will become more dominant. Previous....................................................... As of 300 PM Friday...Circulation around high pressure over the western Atlantic will keep winds from the SW, generally in the 10 to 15 kt range, through the period. Seas will likewise show little variation, running right around 3 ft through Saturday. SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/... As of 330 PM Friday...Precautionary headlines may be needed Sun into early Mon as winds increase to 15 to 20 KT winds and seas reach 4 feet offshore and possibly up to 5 ft. The afternoon sea breeze circulation will keep winds gusty and seas choppy near shore Sun afternoon to early evening. Very little TSTM activity is expected until Sun night into early Mon when activity will increase across the waters as trough shifts farther east toward the coast. LONG TERM /MONDAY THROUGH WEDNESDAY/... As of 300 PM Friday...Bermuda High Pressure well offshore will lose its influence on our weather by the middle of next week as low pressure in the Canadian maritime provinces pushes a cold front down the U.S. East Coast. This front is shown by the latest GFS and ECMWF models to make it down to near Hatteras on Tuesday. Models diverge slightly on Wednesday as the ECMWF keeps the front stalled to our north and the GFS brings it down to the Myrtle Beach vicinity Wednesday morning. Regardless of which solution is correct, the frisky southwest winds of the weekend should diminish by Tuesday within the weaker pressure gradient near the front. Unfortunately thunderstorm potential should also increase as the front approaches. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...Coastal Flood Advisory until 10 PM EDT this evening for NCZ107. MARINE...None. && $$ SYNOPSIS...RGZ NEAR TERM...DCH/REK SHORT TERM...RGZ LONG TERM...TRA AVIATION...DCH is the U.S. government's official web portal to all federal, state and local government web resources and services.