Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 061740 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 1245 PM EST Tue Dec 6 2016 .SYNOPSIS... Cool and wet conditions are expected today, ahead of a Miller B low pressure system and associated cold air damming. An arctic cold front will approach the area Wednesday night and cross the Carolinas on Thursday. && .NEAR TERM /THROUGH TONIGHT/... As of 935 am Tuesday... Spotty light rain continues this morning ahead of a slowly shearing upper wave lifting out of the Lower Mississippi Valley and a Miller B low transitioning across the locked in CAD airmass. Radar returns are still pretty unimpressive and have really fallen off over Upstate SC as the dry slot is surging north. Expect this trend of spotty rain diminishing from southwest to northeast to generally continue this morning. There is an area of convective elements to watch upstream over northern GA, where dry air aloft looks to create a little potential instability (100-200 J/KG MUCAPE) between 800mb and 600mb, per RAP soundings, which may be enough to enhance or fill in precipitation as the upper lifts across the area through early afternoon. Any instability will remain elevated above the strong cold dome, with guidance keeping the warm sector well southeast near the NC/SC coastal areas. Changes to the forecast have been relatively minor; mainly tweaks to POPs in the next few hours and reductions in QPF, with a focus of best rain rates in the 15Z to 21Z period. Temps will hold relatively steady in the 40s areawide, possibly rising a few degrees in the southeast as the surface low passes by this afternoon. -BS Low-level moisture could be slow to mix out tonight. However, in areas that do clear out, wet soils could result in some areas of fog, potentially dense in spots. Lows in the upper 30s to lower 40s. && .SHORT TERM /Wednesday through Thursday Night/... As of 220 AM Tuesday... Minimal drying will occur on Wed (in the wake of the low pressure system progged to track offshore the Carolina coast tonight) as low- level flow quickly backs to the south/southwest (giving rise to weak warm advection) in response to upstream height falls as potent shortwave energy ejects E/ENE from the Rockies toward the central Appalachians and the leading edge of an arctic cold front progresses eastward through the TN/OH valley to the western slopes of the southern Appalachians by 12Z Thu. Low-level frontogenesis, glancing DPVA, strengthening cyclonic flow aloft and lingering low-level moisture are expected to result in the development of light rain/sprinkles /anafrontal precipitation/ along and behind the arctic cold front as it progresses through central NC during the day Thu. 00Z ECMWF guidance has trended wetter compared to yesterday and is in relatively good agreement with the 00Z GFS now, indicating that a few hundredths of an inch of rain will be possible between 12- 18Z Thu, with the relative best chance of measurable precip in the Northern Piedmont and NE Coastal Plain. Expect highs in the 50s on Wed and lows in the lower 40s Wed night. Highs on Thu will depend on fropa timing, timing/amount of precipitation and cloud cover. At this time, will continue to indicate highs ranging from the upper 40s/lower 50s far NW to mid /upper 50s far S/SE. Lows Thu night will highly depend on fropa timing and ensuing cold advection. Anticipate lows ranging from the mid/upper 20s NW to lower 30s SE. -Vincent && .LONG TERM /Friday through Monday/... As of 220 AM Tuesday... Expect cold/brisk conditions on Friday with highs in the mid/upper 30s to lower 40s and a NW breeze assoc/w strong cold advection as 1040 mb arctic high pressure builds eastward from the central plains toward the Appalachians in the wake of the cold frontal passage Thu/Thu night. Expect cold lows in the upper teens to lower 20s Sat morning as the arctic high settles over the Carolinas late Friday night. Highs on Sat will be similar to Friday (albeit a few degrees warmer). Forecast confidence decreases at the end of the weekend and early next week as guidance diverges with regard to the onset of southerly return flow /warm advection/ as the next cold front approaches the mountains from the west and modified arctic high pressure shifts offshore the Carolina coast. -Vincent && .AVIATION /18Z TUESDAY THROUGH SATURDAY/... As of 1245 PM TUESDAY... 24-Hour TAF period: Widespread light rain will give way to drizzle and fog this afternoon as low pressure along the coast lifts north and drier air filters in from the west and southwest. The drying will be initially at the mid levels, and IFR/LIFR ceilings and visibility in fog will linger through most of the overnight. Should see conditions gradually improve in the west after 06Z as a second low over the Tennessee Valley weakens and lifts into the Ohio Valley after midnight, with ensuing westerly flow drying out the low levels. The drying trend will reach the eastern TAF sites towards sunrise, with VFR conditions prevailing area-wide after around 12Z tomorrow morning. Looking ahead: VFR conditions will return on Wednesday. However, sub- VFR ceilings could return Wednesday night and linger into the day on Thursday ahead of an arctic cold front moving through the area. High pressure building in behind the front by Thursday night will produce VFR conditions through Sunday. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...CBL NEAR TERM...CBL/Smith SHORT TERM...Vincent LONG TERM...Vincent AVIATION...mlm

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