Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC
Issued by NWS Raleigh/Durham, NC
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091 FXUS62 KRAH 192336 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 735 PM EDT Thu Sep 19 2024 .SYNOPSIS... An upper level low over the eastern Carolinas will lift northeast along the Mid Atlantic coast through Friday and then persist as an upper level trough just off the East Coast through the weekend. An upper level ridge of high pressure will move into the northern Gulf States late in the weekend and then extend into the Southeast states through early next week. && .NEAR TERM /THROUGH TONIGHT/... As of 235 PM Thursday... The latest surface analysis continues to show surface high pressure centered over Quebec that extends southwest across the eastern Great Lakes and into the southern Appalachians. A frontal zone with weak areas of low pressure extends northeast to southwest just off the East Coast. A light north to northeasterly low level flow persists across the region in rather moist air mass with PW values of 1.6 to 1.8 inches or about 125% of normal. The airmass across the region is weakly to moderately unstable with MLCAPE values of 500-1000 J/Kg, greatest in the southeast. Further aloft, a persistent upper- level low was centered across southeastern VA and northeast NC with 500 mb temps of -10C and a cyclonic flow from the northwest across central NC. The forecast through tonight remains a little uncertain as a moist and weakly to moderately unstable airmass across central NC is triggered by various mid and upper level disturbances in the cyclonic flow aloft. An area of showers and a few embedded thunderstorms continues to shift south across the southern Piedmont, Sandhills and southern Coastal Plain. This area appears triggered by a disturbance in the mid levels as noted on the 1.5 PVU surface. Another cluster or two of showers and possibly storm`s will drop out of VA into northern and northwestern NC late this afternoon and evening. The convection has not been terribly deep but precipitation rates seem to over perform modest radar reflectivity signatures. With a moist airmass, the rain may be heavy at times and with saturated soils, some localized flooding can`t be ruled out. Despite the instability, the low and mid level flow is rather weak and the CAPE is skinny so not too concerned about any severe storms. CAMs suggest that the convective coverage will relax decrease quickly during the evening hours with dry conditions overnight. Another round of stratus and fog is expected late tonight with perhaps a bit more fog than last night. Lows tonight should range in the lower to mid 60s. -Blaes && .SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/... As of 105 PM Thursday... Aloft, the trough off the mid-Atlantic coast will continue to shift ewd over the Atlantic, allowing high pressure to ridge enewd into the area. A lobe of vorticity in the upper levels will swing sewd through central NC Fri morn/aft, while a trailing mid-level disturbance follows Fri aft/eve. At the surface, a low will continue to meander off the northern mid-Atlantic/New England Coast Fri/Fri night, while high pressure ridges swd through central NC. Some lower dewpoint air should push into the far northeast portions of central NC as the high ridges in. While widespread convection is not anticipated, if showers do develop, the best chance would be over the western Piedmont during the morn/aft with the passage of the vort max aloft, and over the northeast Piedmont/northern Coastal Plain during the aft/eve, generally along the dewpoint gradient as the high ridges swd. The NAM does have some MUCAPE in the 500-1000 J/Kg range Fri morn through the eve, thus an isolated storm or two is still possible if/where convection occurs. Highs should generally range from around 80 degrees NE to mid 80s south, with lows in the upper 50s to mid 60s expected. && .LONG TERM /SATURDAY THROUGH THURSDAY/... As of 325 PM Thursday... Saturday morning, surface high pressure will be centered over eastern Canada with a pressure ridge extending all the way to the Gulf Coast. A weak front will move across the area Saturday night. Am not terribly impressed by the depth of the moisture with the front, but there are too many models, deterministic and ensembles, to keep a dry forecast in that time period. Rainfall does not appear to be substantial, but have gone ahead and added slight chance pops across the northern half of the area. Sunday and Monday continue to have a dry forecast as high pressure reestablishes itself, with just the Triad being clipped on Tuesday with a slight chance of showers in advance of the next front. Low pressure will move across the Great Lakes during the middle of the week, and it currently appears that the most likely timing for any showers or thunderstorms with the upcoming cold front will be Wednesday night. Highs will be slightly above normal for the weekend, then drop a few degrees below normal for the weekdays. Lows will be near normal through the extended period. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/... As of 735 PM Thursday... VFR conditions will persist for the next several hours as most of today`s convection has diminished. There are a few isolated VA mountain showers/storms that may approach KINT/KGSO the next few hours, but this activity should also wane with time. Otherwise, there continue`s to be a good signal for widespread fog potential early Friday morning. Will maintain low visibilities at all sites between ~08 to 13Z via dense fog. Any lingering fog/stratus should lift by mid to late Friday morning. Otherwise, convection chances should be fairly limited Friday compared to recent days. Outlook: Areas of overnight and early morning fog and perhaps low stratus are expected on Friday and Saturday morning. A transient system may bring a few showers or storms to the area on Saturday night otherwise a return to more tranquil weather is expected for Sunday through Tuesday. -Blaes && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Blaes NEAR TERM...Blaes SHORT TERM...KC LONG TERM...Green AVIATION...Luchetti/Blaes