Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 121113 AFDRAH AREA FORECAST DISCUSSION National Weather Service Raleigh NC 713 AM EDT Wed Aug 12 2020 .SYNOPSIS... Broad low pressure will linger over the Carolinas through the weekend. && .NEAR TERM /THROUGH TONIGHT/... As of 350 AM Wednesday... A low to mid level trough/broad low will become a little better defined over the Carolinas through tonight, with an increasingly ely/sely component (off the Atlantic) to the sfc-700 mb flow. The air mass over cntl NC has become considerably more moist than this time Tue, with around 2" precipitable water values now in place east of the Appalachians, per regional observed soundings last evening. Diurnal heating of the unseasonably moist air mass will result in moderate destabilization and the development of scattered to locally numerous, slow-moving showers and storms through the afternoon and evening hours, with the greatest concentration likely drifting into the wrn Piedmont by early tonight. Given weak deep layer flow and resultant shear, and amidst a deeply moist column characterized by the 2" precipitable water values, the threat of severe storms will be low. Instead, the aforementioned slow-movement will favor locally heavy rain and localized flooding, particularly in urban areas. Generally persistence temperatures will be followed given comparable 18-19 C 850 mb temperatures forecast to continue from recent days - highs mostly in the upr 80s to around 90 and lows in the lwr 70s. && .SHORT TERM /THURSDAY AND THURSDAY NIGHT/... As of 400 AM Wednesday... Generally, there will be little change in the synoptic pattern at the surface and aloft over cntl NC this period, though with some modest sharpening of the trough at 850 mb. Associated stronger convergence and lift provided by the 850 mb trough axis, amidst continued high precipitable water values around 2", will favor greater cloud and convective coverage than previous days, and resultant cooler highs in the mid-upr 80s. And with weak deep layer flow remaining, slow cell movement will pose a risk of heavy downpours and localized flooding. && .LONG TERM /FRIDAY THROUGH TUESDAY/... As of 240 AM Wednesday... An extended period of wet weather likely through the weekend. The flow aloft will be weakly cyclonic between a high centered over the Southwest US and another over Bermuda. An area of low pressure in the mid-levels will sit over the southern Appalachians over the weekend before slowly lifting east-northeast early next week. The upper trough to the northwest will amplify as it migrates eastward into the mid-Atlantic region through the weekend. At the surface, an inverted trough will remain over the Appalachians, extending from a low over northern MS/AL through the end of the week, shifting into central NC over the weekend as the low lifts through the Carolinas. While the trough/low should shift off the Carolina coast on Monday, another low/trough will develop over the Deep South and Appalachians on Tuesday. Expect near normal temperatures with highs consistently in the mid to upper 80s and lows in the upper 60s to mid 70s. Min RH values only drop into the mid 60s to mid 70s during the day, with PWATs in the 1.8" to 2.2" range through the weekend. Showers and thunderstorms are expected through the extended period, with the highest chances during the aft/eve, lowest but still lingering chances into the overnight/early morning. && .AVIATION /11Z WEDNESDAY THROUGH SUNDAY/... As of 710 AM Wednesday... Areas of LIFR stratus and fog through 14Z, with perhaps a fleeting MVFR ceilings as the associated moist layer is heated and lifted, will give way to scattered to locally numerous, slow-moving showers and storms this afternoon and evening. Outlook: A persistent regime of late night-morning stratus and fog and diurnally-maximized showers and storms will continue through the weekend, through which time an area of low pressure will remain over the Carolinas. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...MWS NEAR TERM...MWS SHORT TERM...MWS LONG TERM...KC AVIATION...MWS

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