Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC
Issued by NWS Raleigh/Durham, NC
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705 FXUS62 KRAH 260621 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 220 AM EDT Wed Jun 26 2024 .SYNOPSIS... Hot southwesterly flow will result today between high pressure over the Atlantic and a cold front that will approach from the northwest and reach the western Carolinas by Thursday morning. The front will then move slowly east across the central and eastern Carolinas later Thursday through Thursday night. && .NEAR TERM /THROUGH TONIGHT/... As of 955 PM Tuesday... No major changes to the forecast with this evening update. The 00Z upper air analyses show a low over SC at H25, with generally nwly or nnwly flow at H5 over central NC. A capping inversion and shallow but very dry layer around H7 was evident on several 00Z soundings across the mid-Atlantic/Carolinas. There is still a bit of lingering moisture at H85, highest over the eastern Piedmont and Coastal Plain, lower west. At the surface, the dewpoint gradient was still evident at 01Z, stretching from the southern Piedmont to northern Coastal Plain, separating low/mid 60s dewpoints from those in the upper 60s/low 70s. That boundary may retreat further nwwd over night, with dewpoints mainly in the low to mid 70s expected area- wide by daybreak Wed. Low stratus will be possible again Wed morning, mainly east/south of where the dewpoint gradient was as of 01Z. Lows tonight should bottom out in the upper 60s to low 70s. && .SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/... As of 245 PM Tuesday... Hot with near Heat Advisory criteria... Hot conditions look to be close to heat advisory criteria for portions of the eastern Piedmont, Sandhills, and Coastal Plain Wednesday afternoon and early evening. The heat index numbers currently indicate that the urban areas around Raleigh and Fayetteville should top out in the 100-104 range, just short of criteria. Surrounding areas are a few degrees lower in the 98-101 range for heat indices. Maximum temperatures should top out between 96-100, except 93-96 in the NW-N Piedmont. We will hold off on a heat advisory for now, but we may need one for Wednesday in later forecasts, especially for the urban areas around the Triangle and Fayetteville. Otherwise, mostly sunny and hot conditions under strong ridging will continue. There may be an isolated thunderstorm SE Coastal Plain associated with the seabreeze late day. Another mid level trough will approach late Wednesday night. There is a slight chance of showers/thunderstorm NW-N overnight, but chances appear minimal at this time as models suggest plenty of CINH overnight. Lows will be mostly in the 70s. && .LONG TERM /THURSDAY THROUGH TUESDAY/... As of 345 PM Tuesday... Best chance of showers/storms looks to be Thu/Thu night and Sun/Sun night, both just ahead of mid level northern stream shortwave troughs and corresponding surface fronts. Temps will stay above normal through the weekend, esp Thu and Sat/Sun, before moving closer to normal Mon/Tue. Thu/Thu night: A northern stream mid level trough will cross the St Lawrence Valley into New England/Can Maritimes as the tail end of this front eases SE through the Carolinas, taking a frontal zone into our area. The greatest chance for overlapping of strong heating, high PW (near 2"), and decent surface dewpoints will be across our S and E, where the majority of NBM members have precip in the afternoon and early evening. Following this, will have a good chance of showers/storms NW and likely pops across the SE. The deep layer bulk shear will be rather low at just around 10-15 kts with marginal mid level lapse rates, and the moderate SBCAPE does shift E of I-95 late in the day, so expect a decrease in pops in the evening and mostly dry weather overnight as the mid levels dry out behind the mid level trough axis. Expect highs in the lower 90s NW trending to upper 90s SE. Lows in the upper 60s to mid 70s. Fri/Fri night: The surface front is likely to settle just to our S Fri morning, then quickly wash out as the surface high to our N shifts offshore by afternoon. Behind Thu`s shortwave trough, mid level ridging spreads in from the SW across the Carolinas and Southeast coast during this time. PW remains well above normal across our S and SW where low level confluent flow may help organize scattered afternoon convection, perhaps aided in part by an upslope low level component. Will carry chance pops, near climo, across the S and W with little or nothing in the NE, within the exiting surface ridge. With near normal thicknesses balanced by abundant heating, temps should be a bit lower than Thu, with highs around 90 to the mid 90s. Heat index values are projected to be 100-105 over all but the NW. Sat-Sun night: Mid level ridging builds further from the S Plains across the Gulf states Sat through early Sun, as our thicknesses rise to 10-15 m above normal with deep mixing and warm/dry mid levels and weak lee surface troughing over the Piedmont. We should see highs a bit warmer Sat, from the low 90s NW to upper 90s SE, and will have near-climo pops Sat focused on the W CWA where mountain convection may drift late in the day. A potent northern stream trough that moves from the Upper Midwest and across the N Great Lakes Sat will move through S Que/St Lawrence Valley and into the interior Northeast Sun/Sun night, and this plus the westward propagation of the mid level ridge further W into the S Plains and lower Miss Valley will induce mid level troughing down the Eastern Seaboard toward E NC. While SBCAPE and deep layer shear will be marginal Sun, the increasing and deepening moisture (projected PWs nearly 2.5") and the approaching surface frontal zone both support higher pops in the good chance to likely range, highest across the N Sun afternoon through the evening, with the front pushing to our SE overnight. Expect highs again from the low 90s NW to upper 90s SE with high dewpoints well into the 70s, indicative of increased heat stress as heat index values reach 100-110 over nearly the entire CWA, all but the extreme NW, both days, although confidence is lower Sun given the potential for clouds and convection. Mon-Tue: Pops should be on the low side, 10-25% along the S and W, as surface high pressure builds in from the N within mid level troughing. Low level thicknesses suggest highs fairly close to normal, with highs in the upper 80s to lower 90s. -GIH && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/... As of 220 AM Wednesday... An area of stratus based between 1000-1500 ft AGL now blossoming over nrn SC/srn NC will likely continue to expand nwd, amid light sly flow in that layer, and overspread FAY; RDU; and RWI through 11Z, then lift and disperse to VFR by 13-14Z. It may also locally lower to IFR as the sub-cloud layer further cools and moistens through sunrise. While an isolated storm cannot be ruled out mainly around FAY with daytime heating and lift from the sea breeze, there will be a slightly better chance of a few showers and isolated storms over the Piedmont tonight, as a mid-level trough and outflow boundary/front approach from the northwest - likely to be highlighted with a PROB30 group with 12Z TAF issuance. Additionally, the development of an Appalachian-lee, nocturnal low- level jet across and offshore the Middle tonight may result in marginal low-level wind shear mainly from nrn NC/srn VA to the Middle Atlantic coast. Outlook: IFR-MVFR stratus will again be possible especially at FAY and RWI in the early morning from Thu through the weekend. The chance of mainly afternoon-evening showers/storms will be highest, especially at FAY and RWI on Thu, and again area-wide Sun-Sun night. && .CLIMATE... Record High Temperatures: June 26: KRDU: 102/1952 KFAY: 101/1951 June 27: KFAY: 102/1998 June 30: KFAY: 102/2012 Record High Minimum Temperatures: June 25: KRDU: 77/2010 KFAY: 75/1952 June 26: KGSO: 74/2010 KRDU: 76/1902 KFAY: 76/1997 June 27: KGSO: 76/1969 KRDU: 76/1952 KFAY: 77/1998 June 28: KGSO: 76/1969 KRDU: 76/1952 KFAY: 78/1914 June 29: KGSO: 74/2010 KRDU: 78/1914 KFAY: 76/1969 June 30: KGSO: 74/1936 KRDU: 80/1936 KFAY: 79/1936 July 1: KGSO: 77/1970 KRDU: 75/2012 KFAY: 76/1990 && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...MWS NEAR TERM...KC SHORT TERM...Badgett LONG TERM...Hartfield AVIATION...MWS CLIMATE...RAH