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Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC
Issued by NWS Raleigh/Durham, NC
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519 FXUS62 KRAH 171448 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 1048 AM EDT Wed Jul 17 2024 .SYNOPSIS... A strong subtropical ridge will gradually weaken over the Southeast though mid-week. A cold front will settle into the Carolinas on Thursday, then become quasi-stationary while weakening into the weekend. && .NEAR TERM /THROUGH TONIGHT/... As of 1048 AM Wednesday... * One more day of hot temperatures * Showers and storms possible this afternoon Mid morning water vapor imagery and surface analysis depicts longwave troughing across the lower Great Lakes, with a cold front stretching from western NY through OH and into IL. Across NC, high pressure remains off the coast with broad southwesterly flow aloft. A series of weak perturbations are noted in WV imagery across GA and SC, and there is some ongoing convection off the southeast NC coast, but conditions remain mostly dry across central NC. Despite some early morning cloud cover, temperatures have quickly risen into the lower 80s in the Triad and in the mid/upper 80s in the east. One more day of dangerously hot temperatures and high heat indices are in store for the region as dewpoints remain in the low to mid 70s with air temps in the mid to upper 90s. Heat Advisories were expanded overnight and look good based on obs as of 10am. As for storm chances, 12Z HREF continues to depict an active afternoon not only across the western Piedmont but also across the Coastal Plain. Curiously enough, several consecutive runs of the NAM nest and HRRR aren`t terribly enthused about storm chances in the east, and debris cloud cover from morning convection off the coast could limit heating and storm potential across the those areas. I`ll maintain at least a 30-40 percent chance of storms across the southeast as it is mostly clear across the Sandhills and the entire CWA should rapidly destabilize by early afternoon. However the best forcing for ascent and synoptic scale forcing will be closer to the longwave trough as it migrates into New England this afternoon, and storm chances will remain highest in the NW Piedmont, decreasing as one travels eastward. Forecast remains in good shape overall. Hot today, with overnight lows in the mid to upper 70s. && .SHORT TERM /THURSDAY AND THURSDAY NIGHT/... As of 345 AM Wednesday... Broad mid-level troughing will dig from New England into the lower MS Valley on Thursday, as a cold front approaches central NC from the NW before moving through on Thursday night. The front will be slow moving given the front-parallel (southwesterly) flow aloft, which could result in training convection. There will be plenty of moisture for this front to tap with PW values of 2 to 2.25 inches, along with marginal to moderate instability of around 1000-2500 J/kg, highest SE. There will also be upper support as we will be in the right entrance region of a jet streak over New England and the northern Mid-Atlantic. Thus widespread showers and storms are expected, and the vast majority (80-90%) of GEFS/EPS/CMC ensemble members depict precipitation. Categorical POPs continue, maximized with daytime heating in the afternoon/evening, though some chance POPs still linger overnight. Total rainfall amounts on Thursday and Thursday night are expected to range from 0.5 inches NW to as much as 2 inches in the east, but locally higher amounts will be possible especially where slow-moving storms occur. WPC continues a slight (level 2 of 4) risk for excessive rain across roughly the eastern half of central NC, with a marginal (level 1 of 4) risk elsewhere. While the strongest mid-level flow will be north of the region, the flow will still be perturbed enough that 20-30 kts of deep layer shear is possible. So SPC has a marginal (level 1 of 5) risk for severe storms, with damaging winds the main hazard. The dangerous heat will finally come to an end on Thursday despite still being ahead of the front, thanks to all the clouds and precipitation. Forecast highs are in the upper-80s to lower-90s (near normal), with lows Thursday night in the upper-60s to lower-70s. && .LONG TERM /FRIDAY THROUGH TUESDAY/... As of 415 AM Wednesday... The front will settle near the NC/SC border on Friday and then slowly lift north through the day. More heavy rain will be possible especially south where moisture and instability will be greatest. Amounts do look to decrease a bit overall as upper support wanes with the mid/upper trough lifting into Canada. Shear also looks even weaker so severe weather may be even less of a concern. Forecast amounts on Friday/Friday night range from around a quarter inch in the north to around an inch in the south, but again locally higher amounts will be possible, and WPC still has central NC in a marginal (level 1 of 4) risk for excessive rain. The front then looks to continue slowly lifting north through the mid-Atlantic from Saturday through Tuesday, becoming more diffuse as it does so. Overall rainfall amounts and shower/storm coverage should continue to slowly decrease each day as Atlantic ridging builds back westward and we actually get mild height rises, with the front moving farther away. But rich moisture and marginal to moderate instability will still be in place, so POPs stay above climo. The upside is the drought relief all this rain will provide, as well as keeping the heat at bay. Forecast highs from Friday through Tuesday are mostly in the mid-to-upper-80s, gradually moderating from slightly below normal to near normal. Lows will be in the upper-60s to mid-70s. && .AVIATION /12Z WEDNESDAY THROUGH SUNDAY/... As of 631 AM Wednesday... VFR conditions will prevail for much of the 24 hour TAF period. However, scattered showers and storms will develop and spread west to east this afternoon through tonight. Associated brief sub-VFR restrictions could develop at any terminal during this period. Any lingering showers/storms should diminish overnight. Early morning stratus looks possible across the I-95 corridor Thursday. However, confidence was too low to include in the KRWI or kFAY TAFs with this package. Outlook: A cold front will sag into and stall across the region Thursday through Saturday which will increase the chances for sub-VFR conditions through this weekend. && .CLIMATE... Record High Temperatures: July 17: KRDU: 100/1887 KFAY: 102/1932 Record High Minimum Temperatures: July 17: KGSO: 75/2013 KRDU: 80/1887 KFAY: 77/2019 July 18: KGSO: 76/1986 KRDU: 79/1887 KFAY: 77/2019 July 19: KGSO: 75/2016 KFAY: 77/2023 July 20: KGSO: 75/2019 KRDU: 76/2020 && .RAH WATCHES/WARNINGS/ADVISORIES... Heat Advisory from 11 AM this morning to 8 PM EDT this evening for NCZ008>011-024>028-040>043-075>078-084>086-088-089. && $$ SYNOPSIS...MWS NEAR TERM...Leins SHORT TERM...Danco LONG TERM...Danco AVIATION...Luchetti CLIMATE...RAH