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Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC
Issued by NWS Raleigh/Durham, NC
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278 FXUS62 KRAH 080709 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 305 AM EDT Mon Jul 8 2024 .SYNOPSIS... A weak frontal zone extending from Chesapeake Bay through the Piedmont of the Carolinas will weaken further today before dissipating tonight. Mid and upper level high pressure will build across the area through mid week, before another cold front approaches Wednesday night. This front will then stall out and hold over the western and central Carolinas through Friday. && .NEAR TERM /TODAY AND TONIGHT/... As of 205 AM Monday... Continued partly to mostly cloudy and humid but with slightly lower convection coverage expected today. The degree and extent of morning cloudiness will play a role in the initiation of showers/storms today. An MCV and persistent widespread rain with embedded storms covering much of central SC has scraped across our SW areas, bringing locally heavy rain to Anson county in the last couple of hours, although cloud tops with this feature continue to warm steadily as it drifts ESE. This MCV appears to be locked to a very weak and diffuse frontal zone stretching over the Carolina Piedmont, and this front should continue to weaken today. A very moist column persists over our area, with PWs in the 2-2.5" range, 150%-175% of normal, although the highest values are expected to push slightly NW to be situated more over the NW Piedmont, nudged by the upper low off the Carolina coast tracking to the SSW toward the N Bahamas. Narrow mid-upper level ridging will build today from the central FL panhandle NE through central NC, which will keep our mid level flow and steering very weak, thus slow and meandering outflow-steered convective cells/clusters may produce a localized mostly nuisance flooding risk once again today. The presence of nocturnal stratus well into the morning and abundant debris mid and high clouds in tandem with slightly warmer mid levels should cut back on SBCAPE a bit today, too, which with poor deep layer shear should hinder storm organization. Will have scattered showers and isolated storms through this morning, with pops then rising to good chance in the afternoon, highest in the W and SE (the latter likely focused on old boundaries and sea breezes). Expect pops to again decrease in the evening, although given the potential for another round of MCVs and warm/moist low levels to keep some amount of marginal elevated CAPE going well past sunset, confidence in a dry overnight is pretty low. Expect highs in the upper 80s to mid 90s, followed by lows in the 70s. -GIH && .SHORT TERM /TUESDAY AND TUESDAY NIGHT/... As of 300 AM Monday... Very little changes with our weather pattern, and again expect convective coverage to peak at scattered, focused across our west sections and southeast. The narrow mid-upper level ridge continues to build across central NC, while a diffuse MSLP pattern with weak surface winds and continued dewpoints mostly in the 70s will contribute to a weak wind profile through the column and, once again, slow-moving and outflow-driven convective clusters that could drop isolated heavy rain. With higher res models like the RAP and HREF members showing lower storm coverage and an earlier demise than what we`ve seen the last couple of days, the resulting reduction in convective debris clouds that might hinder heating combined with thicknesses about 5-8 m above normal suggests that we`ll see temps a bit warmer than today. Expect highs in the low-mid 90s which will push HeatRisk into the high-end Moderate and low-end Major categories. Lows will again be mostly in the 70s. -GIH && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... As of 308 AM Monday... * Typical summertime pattern through the extended with high humidity * Hottest temperatures Wed/Sun and lowest highs Fri * Highest shower/storm chances Thu into Sat The remnants of Beryl, after interacting with a mid-level shortwave trough over the Great Lakes and Midwest, will be located somewhere near IL/IN by early Wed. Little has changed with its overall track, with most ensemble and deterministic solutions taking this area of low pressure ENE into the Great Lakes and Canada by Thu/Fri. The system will bring a cold front near the area late Wed night to early Thu across the western NC mountains and then is still forecast to stall along or just west of the area into Sat. With the front not approaching until late Wed across the west, we will have another day of hot and humid conditions midweek as southerly flow remains well entrenched, if not more so. Heat indices could meet or exceed 105 in portions of the Triangle and Sandhills, with highs in the low to mid 90s and dewpoints near the low to mid 70s. Scattered showers and storms appear favored in the aftn/eve, especially across the west with the approaching front and pre- frontal trough. As the front gets hung up and stalls along or just west of the Piedmont Thu, guidance continues to show an area of low pressure forming along the SE US and riding up along the boundary through central/eastern NC late Thu into early Sat. This area of low pressure could be convectively induced as an MCV and/or through some interaction with an upper-level shortwave tracking toward the Carolinas from the western Atlantic. Either way, during this time, there continues to be deep moisture transport and anomalous PWATs of 2.1-2.3 inches (normals are about 1.4-1.5 in) to couple to the low- level frontal/trough convergence. WPC is currently placing our area in a Level 1 out of 4 risk of excessive rainfall for Fri/Sat and this is quite reasonable given the mentioned factors. This will continue to be monitored as we get closer. As such, our highest rain chances still appear to be Thu into Sat. By the weekend, we will see more typical diurnal shower/storm chances, though somewhat drier conditions should take hold by Sun as WSW flow ensues with a trough axis building in from the west and ridging off the western Atlantic reasserting itself. A more typical lee trough looks to take over at the surface, with PoPs more toward climo. Temperature wise after Wed, highs trend to the 80s on Fri, coincident with highest rain chances. A return to the 90s, and consequently heat indices above 100, look in store Sat/Sun as the ridge builds back west with lesser rain chances. && .AVIATION /06Z MONDAY THROUGH FRIDAY/... As of 1230 AM Monday... Confidence is high in widespread sub-VFR stratus (mostly IFR/LIFR) and areas of mostly MVFR fog persisting across much of central NC until mid morning, particularly affecting INT/GSO/RDU, with slightly lower confidence at RWI/FAY. Patchy rain will dwindle but linger over the far SW edges of the forecast area through daybreak, however much of the area will stay dry through mid morning. IFR clouds will be slow to improve, likely rising to MVFR between 14z and 16z (slowest in the W Piedmont) and to VFR by 18z. FAY is likely to see MVFR/IFR cigs lasting a shorter time, 10z-14z, with 08z-14z at RWI. Scattered showers and storms are expected today, through the central sections (RDU) late morning/early afternoon then over the NW and SE areas (INT/GSO and FAY) mid afternoon through early evening, with storms likely to develop over the higher terrain and drift into the Triad, and along an inland-moving sea breeze toward FAY. Overall coverage is expected to be lower than over the last two days, and showers and storms should start to decrease and diminish by mid to late evening. Periods of sub-VFR cigs/vsbys and gusty/erratic winds are possible in and near any storms today. Outside of any storms today/tonight, surface winds will be light and variable, mainly from the S (SE through SW). Looking beyond 06z Tue, there is a chance for sub-VFR cigs/vsbys early Tue morning, mainly across the S, but should be less coverage than this morning. A general pattern of scattered to numerous showers and storms primarily each afternoon through evening will continue through Fri, with the highest chances late Wed night through Fri, and at least some chance of early-morning sub-VFR clouds/fog each day. -GIH && .CLIMATE... Record High Temperatures: July 10: KRDU: 99/1993 Record High Minimum Temperatures: July 8: KGSO: 76/2010 KRDU: 78/1986 KFAY: 79/2012 July 9: KGSO: 76/1987 KRDU: 74/2014 July 10: KGSO: 77/1981 KRDU: 77/1981 KFAY: 77/1998 July 11: KGSO: 75/1992 KRDU: 77/1981 KFAY: 76/2019 July 12: KGSO: 76/2011 KRDU: 78/2011 KFAY: 80/1935 && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Hartfield NEAR TERM...Hartfield SHORT TERM...Hartfield LONG TERM...Kren AVIATION...Hartfield CLIMATE...RAH