Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 171132 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 632 AM EST Sat Feb 17 2018 .SYNOPSIS... A cold front which pushed southward through the area late Friday will settle near the South Carolina border this morning. This front will lift back northward into the area as a warm front late today, followed by passage of another cold front across the area late tonight. High pressure will then build over the region on Sunday. && .NEAR TERM /THROUGH TONIGHT/... As of 345 AM Saturday... As surface high pressure moves off the coast a cold air damming wedge is expected to set up over central NC today but the best isentropic lift won`t get going until around 12z. This will bring in clouds through the morning. Ceilings are expected to come down through the day to at least IFR levels with some LIFR mixed in. Light rain or drizzle will begin late morning into the early afternoon. Rain rates aren`t expected to be high and only about a tenth to a quarter of an inch of rain will fall with the highest totals in the NW Piedmont. Temperatures will struggle with 40s north of US 64 and low 50s south. The 24 hour temperature change will be a whopping 25-35 degrees cooler depending on location. A large gradient is expected across the southern tier bringing more uncertainty to the temperature forecast. Another disturbance will form to the southwest and track over the area on Saturday night resulting in a developed low pressure by the time it moves offshore. When it goes, it will take the wedge with it helping to bring an end to the clouds and rain but that will likely not happen until Sunday morning. Overnight lows in the mid 30s to low 40s. && .SHORT TERM /SUNDAY AND SUNDAY NIGHT/... As of 345 AM Saturday... As continental high pressure moves in on Sunday, expect rain to stop and skies to clear. This will be a fast moving transitory high that will end up moving east of the area and offshore by Sunday night. For all the chilly temperatures on Saturday, Sunday will feature highs in the upper 50s to middle 60s across the area. Winds will begin to swing around to southerly by Sunday evening setting up the beginning of return flow that will exist early next week. Sunday night lows in the 40s with highest temps in the southwest. && .LONG TERM /MONDAY THROUGH FRIDAY/... As of 330 AM Saturday... A very warm work week is likely, with the potential to set some more record highs midweek. Mon/Mon ngt: We`re likely to see some like overrunning rain, particularly over the NW CWA, associated with the northward passage of an elevated warm front through the area. As the surface high moves off the coast, a surface warm front, located south of the area early in the day, will progress northwestward into the CWA, although the NW half should hold onto the cooler stable air through Mon night. Skies should be generally cloudy, with highs from the upper 50s NW to the lower to mid 70s SE as thicknesses there soar well above normal. Expect lows in the low-mid 50s NW (likely occurring early in the night, with temps steady or rising late) to the upper 50s/near 60 SE. Tue/Tue ngt: There is a good chance that the Triad area (especially INT) will still be within the in situ stable pool at daybreak Tue. But the building and deepening ridge over and just off the SE coast (highlighted by a mid level anticyclone off the Savannah GA coast that expands toward NC during the day) and subsequent subsidence aloft should allow for enough insolation atop this vulnerable stable layer to prompt its eventual erosion Tue. Still anticipate muted warming over the NW, however, as the low levels will remain moist. Should see low stratus and fog to start the day, breaking up outside of the NW sections with heating. Highs from the upper 60s NW to near 80 SE, where thicknesses may reach 60-70 m above normal, and records may be threatened (see climate section below). Mild lows of 57-62, with a potential round of nighttime stratus over the Piedmont. Wed-Fri: Wed will be another very warm day, but the mid level flow will begin to flatten a bit, transitioning from anticyclonic to neutral from the SW, allowing subtle perturbations emanating from the weak low located off Baja California this morning to track toward the region. As low level moisture inflow strengthens off the Gulf, clouds and precip chances will increase, primarily over the NW CWA Wed/Thu as a surface cold front (along the periphery of the Southeast ridge) approaches from the W and NW. Forecast uncertainty increases considerably starting Thu, as models differ as to whether or not this front pushes into NC as a backdoor front, and if so, how far south it goes. This all depends upon the amplitude of a wave passing through the St. Lawrence Valley and New England as well as on the density of the surface high behind the front, both factors with low predictability at this time range. Given this, will be more conservative but lean toward a warmer solution, as the ECMWF has been trending toward a stronger mid level ridge over the Southeast late week. Will go with just chance pops for now near and south of the approaching front Thu/Fri, but confidence in the details is low. Highs in the 70s to lower 80s Wed, upper 60s to upper 70s Thu, and lower 60s to lower 70s Fri, with a front potentially near or into northern sections of NC these latter two days, with mostly cloudy skies. -GIH && .AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
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As of 645 AM Saturday... 24 Hour TAF Period: MVFR ceilings steadily taking over now from east to west with the Triad still VFR at this time. NNE winds at 5-10 kts will continue through the overnight hours with a few sporadic gusts to 20 kts possible. As a CAD wedge builds in this afternoon expect conditions to steadily deteriorate with light rain beginning around 15z and ceilings dropping through MVFR levels to IFR/LIFR by late afternoon or early evening on Saturday. Ceilings will drive the aviation conditions with MVFR level visibilities also possible throughout the afternoon. Conditions will return to VFR in the Triad very near to the end of the TAF period with points south and east to follow later. Long term: Sunday will see a return to VFR conditions before another disturbance move in for early next week followed by an extended period of southerly return flow featuring a summer-like pattern with high moisture content and the potential for periodic sub-VFR conditions.
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&& .CLIMATE... RDU Records: Date | High Year | High Min Year ------------------------------------------ 02/20 75 1939 62 1939 02/21 76 2011 55 1939 GSO Records: Date | High Year | High Min Year ------------------------------------------ 02/20 74 1922 56 1939 02/21 74 2011 50 1954 FAY Records: Date | High Year | High Min Year ------------------------------------------- 02/20 82 2014 60 1939 02/21 80 1991 61 1953 && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...WFO RAH NEAR TERM...Ellis SHORT TERM...Ellis LONG TERM...Hartfield AVIATION...Ellis CLIMATE...KC/Badgett

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