Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC
Issued by NWS Raleigh/Durham, NC
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552 FXUS62 KRAH 071926 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 326 PM EDT Sun Jul 7 2024 .SYNOPSIS... A weak frontal zone extending from the Chesapeake Bay into the Piedmont of the Carolinas will linger and weaken before dissipating by Tuesday. Mid and upper level high pressure will then build across the area before another cold front approaches late in the work week. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... As of 325 PM Sunday... * Scattered to numerous showers and storms with locally torrential rain will be focused across the western and northwest Piedmont and VA border counties this evening. The latest surface analysis shows a cold front extending from southern Chesapeake Bay southwest across southeastern VA into the northwestern Piedmont of NC and into far upstate SC. The air mass across central NC is very moist with PW values of 2.0 to 2.3 inches. Southeast of the front, dew points range in the mid to upper 70s. Breaks of sunshine have allowed temperatures to climb into the 90 to 95 degree range in parts of the southern Coastal Plain. Northwest of the front, a light northeast wind is observed in the Triad and in the VA border counties in a cooler and more stable air mass. With the widespread rain and cooler air mass, temperatures are only in the upper 70s to lower 80s. Further aloft a 594dm mid and upper level anticyclone is centered over the eastern Gulf of Mexico, sandwiched between Beryl and the closed mid/upper level low east of the Carolinas. The mid and upper flow across NC is rather light from the west and southwest. Multiple clusters of convection continue to move east and northeast across the western and northwester Piedmont this afternoon. These storms are being enhanced by a warm southwesterly flow atop a cooler air mass near the surface and in a region of convergence near the front. CAMS suggest that this convection will continues for the next several hours with other more widely scattered convection expected across the rest of central NC. The air mass across southern NC and especially the Coastal Plain is much greater with MLCAPE values in excess of 2000 J/Kg. Convection across the southwestern NC Mountains will shift east into SC tonight, and should just skirt the southern portion of the forecast area. Other storms may fire later this evening in the Coastal Plain as outflows converge in this area. The main weather hazard tonight will be slow moving convection in a moist and weakly to moderately unstable environment will be produce some locally heavy rain and possible flooding concerns. It will remain warm and muggy overnight with considerable cloudiness and some patchy areas of fog late. Lows will range in the lower to mid 70s. -Blaes && .SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/... As of 250 PM Sunday... * Continued shower/thunderstorm chances, albeit it with lower areal coverage * Brief periods of heavy rain likely the primary threat with any storms that develop We should have a very similar synoptic setup across the area tomorrow with PW`s still running around 2 to 2.2". The presence of a stalled surface boundary may be lacking though and with only a lee trough and sea breeze to contend with, the overall triggering mechanisms for convection may ultimately be the limiting factor. Storms are once again favored across the western Piedmont along with the Sandhills/southern Coastal Plain, with lesser chances elsewhere. Storms are likely to be outflow dominant and pulse-type in nature given very weak steering flow around 15kts or less. While wet microbursts would be a possibility with any storms that approach severe limits, locally heavy rainfall from slow moving/training storms would likely be the primary threat tomorrow. However given relatively limited areal coverage, we shouldn`t need any flood watches. PoPs in the 20-40 percent range area-wide are the general consensus from the NBM, HREF, and other global models and this seems reasonable at this point. Temps will be on par with today`s values with highs in the upper 80s/lower 90s with lows falling into the lower 70s. && .LONG TERM /TUESDAY THROUGH SUNDAY/... As of 250 PM Sunday... * Typical summer pattern through the weekend * Some storms possible Tuesday/Wednesday, becoming more numerous late in the week Precip chances look to decrease on Tuesday as an offshore upper low off the NC coast dives southwestward toward Florida. In its wake, mid level heights appear to increase by a few meters and this may be enough to further inhibit storm development across the area. While similar PW`s will be in place area-wide, very limited forcing and instability outside of an area near a lee trough across the western Piedmont should keep storms isolated/widely scattered in nature. Meanwhile, the remnant circulation and moisture associated with T.C. Beryl will be drawn inland and absorbed into a longwave trough approaching the western Great Lakes later this week. This will spawn a relatively deep surface cyclone that will track northward across the Great Lakes into southern Ontario. An attendant surface boundary will make an eastward run at the mountains, but likely stall/wash out before it makes it across. However the remnant boundary and/or lee troughing will likely result in an area of enhanced surface convergence which will be stall out and be slow to exit the area. Nearly all global models suggest a plume of increased PW`s will be drawn inland from off the SE coast on Wednesday, interacting with and serving as a necessary ingredient for increased shower and thunderstorm coverage to close out the week. There is a general consensus among the ensembles that Thursday and Friday could be particularly active as a weak surface low develops along the stalled surface boundary to our south and tracks through central NC. Looking at the 100 member grand ensemble of the Canadian, GFS, and EC ensemble forecast systems, nearly 80 percent suggest precip across the area on Thursday and nearly 90 percent on Friday, which is an unusually high amount of agreement for this time of year at this lead time. Of course exactly how much rain will fall, and exactly where the surface boundary and low track set up, is still TBD but the trend of increasing late-week PoPs will continue. Precip chances should remain elevated (although slightly lower as compared to Thursday/Friday), as we get into the weekend. Temperatures this week should be within a few degrees of normal. Through mid week with mid level ridging sneaking in from the east, temps should make a solid run into the mid 90s area-wide and it is on these days (Tuesday and Wednesday) where heat indices could make a return to dangerously high values. However increased cloud cover and precip chances will knock readings back into the mid/upper 80s Thursday, especially Friday, and possibly into Saturday as well before returning to normal by Sunday. Lows throughout the period generally upper 60s to mid 70s. && .AVIATION /19Z SUNDAY THROUGH FRIDAY/... As of 225 PM Sunday... A cold front extends from southeast VA southwest to just south of the Triad into southwestern NC. Near and north of the front widespread clouds with MVFR and even IFR restrictions are noted with scattered to numerous showers and thunderstorms. The most unsettled weather is expected at the KINT and KGSO terminals through around 23Z with additional showers and storms possible through around 02Z. Similarly convection will be near the KRDU terminal but perhaps with a less coverage. Showers and storms are expected to be more isolated at the KFAY and KRWI terminals with a threat of convection continuing a little later into the evening hours but greatest between 22Z and 02Z. The convection should ramp down late in the evening with just a risk of an isolated shower overnight. Some patchy MVFR to IFR stratus and fog is possible late tonight. The greatest threat will across the western Piedmont and locations where significant rain has fallen. Winds will be light tonight and will be from the north or variable at KINT and KGSO and variable or from the south at KRDU, KRWI, and KFAY. Light southwest winds are expected on Monday with VFR conditions arriving by mid to late morning. Looking beyond 18Z Monday: A rather typical summer pattern of scattered afternoon and evening showers and storms along with some late night and early morning stratus and fog is expected through the period with the coverage of storms and restrictions expected to uptick on Wednesday and increase for Thursday and especially Friday. -Blaes && .CLIMATE... Record High Minimum Temperatures: July 7: KGSO: 73/2019 KRDU: 77/1900 KFAY: 78/2017 July 8: KGSO: 76/2010 KRDU: 78/1986 KFAY: 79/2012 July 9: KGSO: 76/1987 KRDU: 74/2014 && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Blaes NEAR TERM...Blaes SHORT TERM...DL LONG TERM...DL AVIATION...Blaes CLIMATE...RAH