652 FXUS62 KRAH 081758 AFDRAH AREA FORECAST DISCUSSION National Weather Service Raleigh NC 155 PM EDT Wed Jul 8 2020 .SYNOPSIS... An area of low pressure over the Savanna River Valley will move slowly east and offshore this morning and then northeast up the Carolina coast through Thursday night. A trailing cold front will linger across the Carolinas into the weekend. && .NEAR TERM /THROUGH TONIGHT/... As of 1000 AM Wednesday... Not much in the way of changes with today's forecast. Backed off pops slightly across northwest counties through the morning hours taking a look at current radar trends. Scattered to numerous showers and thunderstorms are still expected this afternoon, and as previously mentioned, very high PW values could allow for very efficient rainfall in some locations. Previous discussion follows. As of 340 AM Wednesday... An area of low pressure over the Savanna R. Valley will move slowly east and then northeast up the Carolina coast through Thursday night. Plume of tropical moisture, featuring PWATS of 2-2.3"(2.5 standardized anomalies above climatology), will spread inland into the area today, courtesy of the deep ESELY flow ahead/to the north of the low pressure system. Rain chances will remain isolated/patchy this morning. However, the commencement of daytime heating and resultant weak destabilization (500-1000 J/Kg MLCAPE) during the late morning/early afternoon, will lead to showers and embedded thunder becoming numerous across eastern two-thirds of the forecast area, with more in way of scattered convection across the western Piedmont. Given the tropical moisture in place, expect some heavy downpours that could easily drop 1 to 1.5"/hour. However, the potential for cell training looks low and thus any threat for flooding should be limited to poor drainage areas. Additionally, weak lapse rates and equally weak shear should preclude a severe threat as well. Similar to this past evening, showers and storms are expected to diminish with loss of heating, with widespread IFR to MVFR developing again tonight. Highs today in the lower to mid 80s, potentially cooler in the east where convective onset will occur earlier in the diurnal cycle. Lows tonight 70 to 75. && .SHORT TERM /THURSDAY AND THURSDAY NIGHT/... As of 340 AM Wednesday... The coastal surface low will continue to jog slowly north, near or just off the northern NC coast. The deep tropical moisture is forecast to shift across eastern NC, with significantly drier air overspread the western third of the forecast area. This should result in drier conditions across the western Piedmont, and while rain chances on Thursday will not be as high as today, central and especially eastern portions should continue to see a good chance for diurnally driven convection Thursday afternoon and evening. Once again, expect convection to diminish after sunset, with the northern coastal plain counties standing the best chance of seeing some isolated showers overnight. Isolated flooding in poor drainage areas will remain the main threat. As rain chances decrease, temperatures will begin to warm up. Highs 85 to 90. Lows again in the lower 70s. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... As of 137 PM Wednesday... Low pressure along the Mid-Atlantic Coast will be lifting north thanks to increasing southerly flow ahead of a deepening short wave trough crossing the Great Lakes and Ohio Valley regions. With our area in between these two system, and esp given subsidence in the wake of the coastal low, we should see mainly dry weather during the daytime Friday with highs in the low 90s. By Friday evening, scattered showers/tstms associated with the upstream short wave and assoc prefrontal sfc trough will begin approaching our western zones and will move across central NC during the night hours into Saturday morning. Previous runs have depicted the sfc boundary and mid level trough axis basically stalling across the Carolinas during the weekend with mainly diurnal rain chances continuing. However, the 12Z GFS now wants to push these features a bit farther east, which would mean lesser rain chances for central NC. Since sfc boundaries typically stall across the Carolinas this time of year, for now prefer to hold on to climo PoPs and above normal temps during the weekend, pending continuing runs showing the same trends. Early next week, another short wave will drop into the mean trough that will be in place over the East. This would result in a period of above-climo PoPs on Monday. Thereafter, the main weather story will feature the ridge that is currently over the Southwest and Southern Plains, which is progged to gradually shift east during the long term period. This ridge ends up extending from the Southern Plains all the way east to the Southeast states by the middle of next week. While this pattern is a drier pattern, it's a hotter pattern for us as well. && .AVIATION /18Z WEDNESDAY THROUGH MONDAY/... As of 155 PM Wednesday... 24 hour TAF period: Low pressure moving slowly up the North Carolina coast will bring showers and isolated thunderstorms into the state, with the greatest coverage across eastern portions of the area. Have continued the TEMPO group mention for RDU/FAY/RWI for the possibility of visibility reduction in stronger showers, although confidence wasn't high enough to include a TSRA mention at the time (although a thunderstorm cannot be ruled out). Shower coverage will diminish with the loss of daytime heating, although eastern sites could still have a passing shower during the evening hours. Low ceilings are expected once again, and have continued an IFR mention at RDU/FAY/RWI, although confidence was not high enough to keep the inherited LIFR ceilings. Conditions should slowly improve Thursday morning, although VFR cigs are not expected until the afternoon hours. The diurnal trend of showers should start before the end of the 18Z TAF period at FAY/RWI. Winds will remain out of the northeast around 5-10 kt with the associated low pressure moving along the Carolinas. Looking ahead: Showers and restrictions will continue Thursday afternoon/evening. Friday should be dry before a cold front brings the return of a chance of showers and restrictions into the weekend. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...CBL/KC NEAR TERM...Green/CBL SHORT TERM...CBL LONG TERM...np AVIATION...Green/CC