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Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC
Issued by NWS Raleigh/Durham, NC
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261 FXUS62 KRAH 180715 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 314 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 312 AM Thursday... 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. At the sfc, latest obs displayed a cold front draped across western TN extending northeast into western PA. This front will slowly sag into our northern areas this evening. Ahead of the front, MLCAPE will rise well into the 2000 to 3000 J/kg range this afternoon. As the upper trough continues to eject eastward, a few triggering mechanisms will promote scattered to numerous showers and storms this afternoon and evening. First, an MCV currently generating convection over central TN will pivot across the NC/VA border later today. Outflow out ahead of this feature will combine with remnant outflow from yesterday`s convection (and likely also weak sfc convergence along a lingering sfc trough) and likely trigger showers and storms early this afternoon across the Piedmont/northern Coastal Plain. This convection will then likely pivot southeast and move towards the coast late tonight. Bulk-layer shear will reach upwards to 30 to 35 kts (peaking across the north) and thus there should be a decent chance for multi- cellular/linear structures to develop later today into the late evening period. Forecasted hodographs appear rather straight over much of central NC. Thus, if any stronger/organized storms do develop today, the main concern would be the potential for damaging wind gusts to occur (with large hail a secondary threat). The HRRR Neural Network Convective Hazard Forecast (which accurately depicted yesterday`s severe storms across the NC/VA border) suggests that the highest probabilities for any severe weather hazard would be across the northern Piedmont/Coastal Plain between ~19 to 23Z. This makes sense conceptually, as effective shear will maximize in this vicinity. While the mean-layer flow will be relatively strong this afternoon, the shear orientation to the boundaries will be relatively parallel. As such, training convection and instances of flash flooding are possible especially for those south and east of Raleigh. Max temps today will hover in the upper 80s (N) to lower 90s (S). Overnight lows in the upper 60s/lower 70s. && .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 /06Z THURSDAY THROUGH MONDAY/... As of 131 AM Thursday... KRWI and KRDU may experience some residual showers/storms the next few hours, but overall terminals should mainly remain VFR through this afternoon. 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 ceilings are expected to fill in over much of the eastern two thirds of central NC starting near 03Z. Beyond 06Z 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... None. && $$ SYNOPSIS...Leins NEAR TERM...Luchetti SHORT TERM...Luchetti LONG TERM...Green AVIATION...Luchetti CLIMATE...RAH