Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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378 FXUS62 KRAH 060725 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 225 AM EST Tue Dec 6 2016 .SYNOPSIS... High pressure will build across the Middle Atlantic states through tonight, ahead of a Miller B low pressure system and associated cold air damming, which will result in the development and deepening of an area of low pressure through the eastern Carolinas on Tue. Another area of high pressure will build overhead for the middle of the week. && .NEAR TERM /THROUGH TONIGHT/... As of 1010 PM Monday... Conditions continue to slowly deteriorate as short lived Miller-B CAD setup progresses pretty much on schedule. Rain coverage will approach 100 percent of the area by morning as southeast isentropic flow and attendant lift strengthens on the 290K surface between 09Z and 12Z. No changes of note are needed except minor timing adjustments on the temps, which are falling a little more slowly than forecast. Previous discussion: The weather will be quiet through early evening, as surface high pressure continues to ridge across the Middle Atlantic states. Clouds will then quickly thicken and lower, with light rain having already been observed at 21Z as far E as Wrn SC and SWrn NC, in association with a lead deamplifying perturbation now lifting across the Lower MS Valley. This light rain, from mid level ceilings, will overspread our region overnight, with temperatures expected to wet-bulb into the lower to middle 40s by daybreak. && .SHORT TERM /Wednesday through Thursday Night/...
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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
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&& .LONG TERM /Friday through Monday/...
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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
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&& .AVIATION /06Z TUESDAY THROUGH FRIDAY/... As of 115 AM TUESDAY... 24-Hour TAF period: Conditions will Deteriorate to IFR to LIFR between 06 to 12z 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, have removed the mentioned of LLWS from 06z terminal forecast. 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. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...MWS NEAR TERM...mlm/MWS SHORT TERM...Vincent LONG TERM...Vincent AVIATION...CBL

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