Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC
Issued by NWS Raleigh/Durham, NC
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272 FXUS62 KRAH 052333 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 735 PM EDT Fri Jul 5 2024 .SYNOPSIS... Surface high pressure across the western Atlantic and Deep South will shift east through tonight as a surface trough extends south across the Piedmont of Virginia and North Carolina. A cold front will approach the region from the northwest this evening and then move into and stall across Virginia and Carolinas this weekend. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... As of 405 PM Friday... * Dangerously hot this afternoon with record high temperatures set across the area. * Scattered afternoon and evening thunderstorms, especially across the west and north which may produce strong gusty winds The latest surface analysis shows a broad surface troughs extending north to south across VA and the Carolinas. A 1016mb surface high across the western Atlantic extends southwest into the coastal Carolinas and FL. A cold front extends southwest from a weak surface low over northeast PA into eastern OH and KY. The airmass across central NC is hot and humid with surface dew points in the lower 70s with some upper 60s noted in south central NC and northern SC. It has been an extremely hot day with temperatures at or in excess of 100 at numerous locations including 106 at KRDU; 101 at KFAY, KMEB, KGSB, KVUJ, KPOB, and KFBG; and 100 at KRWI. Widely scattered showers and thunderstorms have developed across the Piedmont and Coastal Plain near and east of the surface trough. With weak shear, the convection has been very pulsey and limited in breadth. Slightly more organized and more widespread convection developed in the Blue Ridge and across the NC mountains just east of an advancing cold front. This convection will move into the Triad, western Piedmont/Yadkin Valley area and the VA border counties late this afternoon and evening. Storms today will still have the potential to be efficient wind producers with an inverted-V sounding noted and with DCAPE values in excess of 1000 across the western Piedmont. SPC has a marginal risk of severe storms across the northwest Piedmont area with this in mind. Convection will translate east during the evening and gradually weaken during the mid to late evening but unlike previous nights, it will tend to persist a bit later into the overnight. Outside of cooling from thunderstorms, temperatures will be slow to cool this evening. Expect temperatures to persist in the lower and mid 80s in most locations through midnight or later before eventually dropping into the mid 70s to around 80 by Saturday morning. -Blaes && .SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/... As of 300 PM Friday... * Hot and humid once again with Heat Advisories across the east * Storm chances increase by early afternoon, periods of heavy rain could result in flash flooding Upper low over the western Great Lakes will gradually weaken as it moves into Ontario on Saturday. Longwave troughing and the associated attendant surface cold front is likely to get hung up west of the mountains and wash out before it ever arrives across central NC. However, lingering boundaries from today`s (Friday`s) convection will likely lay down a boundary somewhere across central NC this evening, and that will serve as a focal point for shower and thunderstorm development once again on Saturday. Thermodynamic parameters aren`t overly impressive on Saturday with MLCAPEs generally topping out around 1000-1500 J/KG. The combination of modest instability, generally weak steering flow running parallel to the stalled surface boundary, and 99th+ percentile PW`s across the area (2.25 - 2.5 in) would suggest that anything that develops tomorrow will be extremely efficient at producing rainfall. HREF Local Probability Matched Mean QPF suggests the potential for upward of 3-4 inches of rain (if not higher) where storms develop, with the Sandhills suggested as the favored location for heaviest rainfall. While the stalled boundary will likely help concentrate precip across the eastern half of the CWA, it`s hard to pinpoint exactly where the highest rainfall would be. Going to hold off on a Flood Watch at this point given some of the geographic uncertainty of where storms are most likely to occur. Also, the ground should be able to accept at least some amount of rainfall given recent dryness but high rainfall rates, especially across highly urbanized areas, could necessitate a few short-fused flood advisories and/or flash flood warnings tomorrow afternoon/evening. Before any showers develop though, temps should easily rise into the mid/upper 90s once again. Moisture pooling on the eastern side of the stalled boundary and dewpoints once again in the mid to upper 70s will result in another dangerously hot day especially across the Triangle and the Coastal Plain. While Heat Index values and ambient air temperatures may fall a few degrees shy of today`s (Friday`s) observed values, they will still be high enough to warrant a Heat Advisory across eastern portions of our forecast area. Relief in the form of clouds and rainfall will certainly help, although temps and heat indices will likely reach dangerous values for several hours before that relief arrives. Temps will be just a bit cooler in the west (lower 90s) with heat indices hovering right around 100 degrees. Lows tomorrow night will be tricky given lingering cloud cover and rain cooled air but low to mid 70s is the general consensus. && .LONG TERM /SUNDAY THROUGH FRIDAY/... As of 326 PM Friday... A potentially unsettled pattern with daily pops aoa climo is shaping up for much of the long term period, thanks to 1persistent lee trough along with moist s to sw flow in the lower troposphere resulting in abundant antecedent moisture as noted by forecast PWAT values aoa 2 inches. Scattered shower/tstm activity will be primarily diurnal in nature, as typical this time of year. Meanwhile, we`re not expecting any notable change to the hot airmass, so any prolonged dry episodes will result in above, or well- above normal hot temperatures; however, since we`re likely to see an abundance of clouds and scattered shower/tstm activity during this time, high temps should mostly remain closers to climo (lower 90s) each day. && .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/... As of 735 PM Thursday... VFR conditions are largely expected to start the TAF period. Scattered showers and storms continue to develop across central NC. The latest radar trends favor the best chance of storms at RDU, GSO, and INT between 00z and 03z. Storms have recently moved through GSO/INT, and with nocturnal stability taking hold, the storm threat at these terminals appears to be diminishing. However, some VCSH could move in prior to 06z with ongoing moist SW flow aloft. An outflow boundary approaching RDU from the western Piedmont should favor VCTS for the first few hours of the TAF. A storm could impact the terminal but confidence was too low to mention at this time. Stability appears favored at FAY/RWI, but cannot rule out a stray shower/storm until 02z. Largely quiet conditions will take over overnight. Some low stratus is possible early Sat but there is limited agreement in the guidance so have left out any mention for now. Some low VIS are possible at GSO/INT Sat morning, where rain impacted the terminals. A good threat of showers/storms will be in place Sat aftn/eve, with the highest confidence at RDU/FAY/RWI and lesser at GSO/INT. The main storm chances appear favored in the 17z to 00z time period. Outlook: Scattered showers and storms Sat aftn/eve will dissipate by late evening and favor fog/stratus developing Sun morning. A more typical summer time weather pattern will then setup late in the weekend through mid week featuring scattered afternoon and evening showers/storms and a good chance of late night and early morning stratus and fog. && .RAH WATCHES/WARNINGS/ADVISORIES... Heat Advisory until 8 PM EDT this evening for NCZ007-021>023- 038-039-073>075-078-083>086-088-089. Excessive Heat Warning until 8 PM EDT this evening for NCZ008>011-024>028-040>043-076-077. Heat Advisory from 11 AM to 8 PM EDT Saturday for NCZ008>011- 023>028-040>043-075>078-084>086-088-089. && $$ SYNOPSIS...Blaes NEAR TERM...Blaes SHORT TERM...DL LONG TERM...np AVIATION...Kren/Blaes