Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 230708 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 308 AM EDT Mon Oct 23 2017 .SYNOPSIS... A potent upper level trough and accompanying surface frontal system will approach from the west and cross the Appalachians and middle Atlantic states this afternoon through tonight. A secondary cold front will follow and cross our region late Tue and Tue night. && .NEAR TERM /THROUGH TONIGHT/... As of 1020 PM Sunday... Closed upper low over the Lower/Middle Ms Valley this evening will progress east and become increasingly negatively tilted as it moves into the TN Valley by daybreak. Strengthening SELY 925- 850mb moist upglide in advance of the low will be maximized across western NC, leading to the expansion and lowering of the 3 to 4 kft stratus deck across upstate SC into western Piedmont counties overnight, that will then spread east central and eastern NC between 12 to 18z Monday. Can`t rule out an isolated shower/sprinkles within the low-level warm moist air advection, but measurable rain chances should largely remain along and west of the Yadkin River, near the upslope areas. Dewpoints have recovered into the upper 50s to lower 60s this evening, which will result in significantly milder temperatures overnight. Lows generally in the upper 50s to lower 60s, with some mid 50s possible across the NE. && .SHORT TERM /TUESDAY AND TUESDAY NIGHT/... As of 310 AM Monday... Tuesday morning, precipitation associated with a cold front moving through central NC will be in the vicinity of the eastern edges of the CWA and heading eastward with time. Since the low pressure system associated with this front will be located well to the northwest of the area over the Great Lakes, it will take some time for the colder airmass to filter in behind the front. Therefore high temperatures will remain fairly high on Tuesday with upper 60s to mid 70s expected across the area from NW to SE. Lows Tuesday night will be in the low 40s across the NW Piedmont to near 50 degrees in eastern counties. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... As of 310 AM Monday... After the surface front moves through the area by Tuesday morning, attention will turn to the parent low pressure system which will hang back over the Great Lakes for a day or so before weakening considerably and heading due north into Canada. As a result of this, the upper level trough never really digs southward and upper level flow over central NC doesn`t ever go northwesterly. While the surface air will certainly be cooler than we have been, it isn`t an extremely cold airmass that will be filtering into the area. Therefore expect highs to drop into the upper 50s to mid 60s Wednesday and Thursday but then moderate once again to near 70 degrees for the end of the work week. The coldest night will be Wednesday night but guidance shows only upper 30s to lower 40s and with some light westerly winds and possibly some clouds aloft, frost may not be a threat. Lows will remain in the 40s for the majority of the week and then climb back into the upper 40s to lower 50s for the weekend. The next frontal system will approach the area next weekend but there is uncertainty with regards to timing and also the evolution of a low pressure system riding up the southeast coastline prior to the arrival of the cold front that could cause a chance of precipitation earlier in the weekend. && .AVIATION /00Z MONDAY THROUGH SATURDAY/... As of 215 AM Monday... In strengthening and increasingly moist east to sely low level flow off the Atlantic ocean, an axis of MVFR ceilings and showers extending from se to nw across SC, will gradually edge ewd and into the Triad vicinity (INT/GSO) between 12-15Z this morning, then continue, with periods of IFR ceilings, today through this evening. Meanwhile, radiation fog, and perhaps some associated ceilings, will occur at RWI, where radiational cooling potential will linger in closest proximity to the ridge of high pressure that has extended across NC in recent days, which has since moved offshore. Aside from a brief instance of an MVFR ceiling at RDU and FAY, generally VFR conditions are expected to persist at those locations until this evening. An approaching frontal system will then result in the ewd progression of a band of IFR-MVFR ceilings, heavy showers and isolated storms with strong and gusty sly to sswly winds --including some severe with isolated tornadoes and straight line wind gusts aoa 50 kts-- between 22Z/23rd and 05Z/24th. Sely surface winds will otherwise increase after daybreak today, and become strong and gusty by late morning to midday, ahead of the expected line(s) of convection. West to east clearing will occur with the passage of the associated cold front this evening-early tonight. Outlook: Lessening winds and lingering low level moisture late tonight may result in the development of fog and low stratus primarily at INT and GSO between 08-12Z/24th, with VFR conditions anticipated otherwise and elsewhere for at least the next several days. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...MWS NEAR TERM...CBL SHORT TERM...Ellis LONG TERM...Ellis AVIATION...MWS is the U.S. government's official web portal to all federal, state and local government web resources and services.