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Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC
Issued by NWS Raleigh/Durham, NC
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771 FXUS62 KRAH 181404 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 1004 AM EDT Thu Jul 18 2024 .SYNOPSIS... A cold front will approach the region today, bringing showers and storms to the area. The front will remain stationary through the end of the week resulting in unsettled weather and cooler temperatures. && .NEAR TERM /TODAY THROUGH TONIGHT/... As of 1004 AM Thursday... There was little change to the going forecast for this afternoon and tonight. Based on 24-hour QPF amounts, areas from Person to Halifax Counties received some 2-4 inches of rainfall last night. Based on forecast QPF later today and tonight, 1-3 inches of additional rainfall is possible. Current 3-hr FFG values in these counties ranges from 1.5 to 2.5 inches. As a result, localized flash flooding may occur and we went ahead and issued a Flood Watch until midnight tonight, collaborating with neighboring offices. Storms appear to still be relatively fast moving, even with the latest 12Z HRRR, but given prior considerations from the prior discussion, some training may be possible, especially over previously saturated ground. Surface analysis shows the front is draped presently from eastern TN into portions of WV and central PA. A pre-frontal trough was located across western NC and into western VA. It still appears convection will develop along the trough or just ahead of the cold front, with storms initially being isolated to scattered. That activity is still expected to become numerous to widespread as they track ESE into the mid to late evening hours. The main action still looks to be between about 2 to 8 PM, with most storm activity waning after midnight. The front will slowly settle along the NC/VA border by sunrise Fri. Highs this afternoon are expected to be in the upper 80s to lower 90s, as sunshine ahead of storms should allow us to warm up as most guidance suggests. If radar and observational trends become more apparent this afternoon, the Flood Watch may be expanded to include portions of the Triangle. But as it stands, there was limited confidence to include these counties. Lingering convection over the northern Coastal Plain early this morning will continue to diminish over the next few hours. Aloft, water vapor imagery depicts broad swly flow over the southeast associated with an upper trough currently lifting into the northeast. && .SHORT TERM /FRIDAY AND FRIDAY NIGHT/... As of 312 AM Thursday... The front will become quasi-stationary over central NC on Friday while the anomalously moist airmass lingers. Shear will weaken Friday afternoon as the upper jetstreak pulls off into eastern Canada. As such, upper forcing during the daytime will be minimal as weak ridging builds over the southeast. However, given the presence of the front, and the anomalously moist airmass, scattered showers and storms will likely develop during peak heating Friday afternoon. Overall coverage will likely be less compared to Thursday, but given slower expected storm motion, any training cells could lead to instances of localized flash flooding. The greatest threat for flash flooding Friday will be south and east of Raleigh, areas that will likely receive the highest rainfall on Thursday. Convection should generally wane with loss of heating Friday evening. Max temperatures Friday will reach the upper 80s. Overnight lows will remain warm in the 70s. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... As of 225 AM Thursday... As the extended forecast period begins, an unseasonably strong upper low will be over Quebec, with an upper level trough extending south into the Gulf of Mexico. While the upper low will move east over the Atlantic Ocean by Monday, the trough will remain nearly stationary over the Mississippi River valley into next week. Weak southerly flow will allow continued advection of moist air from the Atlantic Ocean and Gulf of Mexico, and with the trough to the west acting as a constant forcing mechanism, showers and thunderstorms can be expected every day. Went with likely pops Saturday through Monday, then capped pops at high chance Tuesday and Wednesday because of the convective nature of the precipitation and uncertainty this many days out. Most of the region will continue to be under a marginal (level 1 of 4) risk for excessive rainfall with any stronger thunderstorms that have high rainfall rates, despite nearly the entire forecast area being in moderate drought. While the weather will remain quite humid, daytime highs limited to the upper 80s and lower 90s with the widespread cloud cover should keep heat indices under 100 degrees, so no heat headlines are expected. && .AVIATION /11Z THURSDAY THROUGH MONDAY/... As of 642 AM Thursday... Scattered to numerous showers and storms are expected to develop this afternoon and evening, peaking near KRDU/KRWI/KFAY later today. As such, expect temporary flight restrictions to develop at these sites at times later today and tonight. The bulk of the heavier rain should move east of central NC late tonight, however MVFR to IFR ceilings are expected to fill in over much of the eastern two thirds of central NC starting near 03Z and persisting through the end of the 24 hr TAF period. Beyond 12Z Friday: A cold front will sag into and stall across the region Friday through Sunday which will increase the chances for sub- VFR conditions through this weekend. && .CLIMATE... Record High Minimum Temperatures: 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 July 21: KGSO: 76/2011 KRDU: 78/1932 KFAY: 80/2017 July 22: KRDU: 78/2011 July 23: KRDU: 78/2011 July 24: KRDU: 79/2011 KFAY: 79/1945 && .RAH WATCHES/WARNINGS/ADVISORIES... Flood Watch through this evening for NCZ007>011. && $$ SYNOPSIS...Leins NEAR TERM...Kren SHORT TERM...Luchetti LONG TERM...Green AVIATION...Luchetti CLIMATE...RAH