Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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700 FXUS62 KRAH 061150 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 650 AM 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/...
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As of 650 am Tuesday... Deamplifying closed low over the Lower MS Valley will eject northeast across the Carolinas this afternoon and off the southern Mid-Atlantic Coast this evening. Miller-B low pressure system will overspread the region, with the primary sfc low filling over the Tn and Ohio Valley this afternoon as the secondary coastal low currently developing off the SE coast deepens as it lifts up the NC Coast. After a lull in precipitation early this morning, precip will fill back in as strong low to mid-level warm moist advection ahead of the approaching shortwave trough and associated developing coastal low will result in widespread rain across the area this morning, and will persist through lunch time when the approach of the upper wave/trough could result in a more showery nature of precipitation. Dry air aloft will begin to overtake the area between 18 to 21z, which will lead to precip tapering off to drizzle before ending across the area largely by 00z. By the end of the day, rainfall amounts are expected to range between 0.50 to 1.0" across the area. Still not impressed with thunder chances across Central NC with the GFS and ECMWF only showing 100-200 J/KG of MUCAPE across the area this afternoon with the approach of the upper wave and associated cold pool with 6-6.25 C/Km lapse rates. Will leave out the mention of any thunder. Near steady temperatures across the Piedmont, possibly falling slightly due to evap cooling once the steadier precip sets in. The far eastern/southeastern zones could warm slightly(2 to 3 degrees)in proximity to the warm front. Highs ranging from mid 40s NW to lower 50s SE. 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.
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&& .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 /12Z TUESDAY THROUGH FRIDAY/...
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As of 650 AM TUESDAY... 24-Hour TAF period: Conditions will deteriorate to IFR to LIFR by 12 to 15z and should remain that way through the taf period as rain overspreads the area ahead of Miller B low pressure system and associated CAD. The low pressure system will lift northeast away from the area during the late afternoon, allowing precip to taper off from SW to NE across the area between 21 to 00z. However, IFR to LIFR conditions in low clouds and possibly fog could persist well into the overnight hours Tuesday night. Finally, concerning LLWS, given little variation in directional wind component between 1000-925mb along with recent guidance showing sustained winds of 10 to 12 kts at KRDU, KFAY, and KRWI, will not include LLWS in 12z TAF package. 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.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...CBL NEAR TERM...CBL SHORT TERM...Vincent LONG TERM...Vincent AVIATION...CBL

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