Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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957 FXUS62 KRAH 261927 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 325 PM EDT Wed Apr 26 2017 .SYNOPSIS... A high pressure ridge will build eastward over the Carolinas this afternoon into tonight. A weakening cold front will approach the mountains from the west on Thursday, then dissipate over the Mid- Atlantic Thursday night. && .NEAR TERM /through tonight/... As of 250 PM Wednesday... Expect a quiet night as mid level ridging builds over the area from the SW, and deep subsidence takes place in the wake of the deep low now drifting off the Northeast coast. Flat scattered to broken cumulus clouds over the area will dissipate with loss of heating this evening, resulting in mostly clear skies overnight with a light wind from the S or SW. Expect decent (although not ideal) radiational cooling tonight, and with elevated dewpoints, lows will be mild tonight, in the upper 50s to lower 60s. -GIH && .SHORT TERM /Thursday and Thursday Night/... As of 345 AM EDT Wednesday... A strong subsidence inversion /cap/ will remain over central NC on Thu. As such, one would expect dry conditions to persist. A squall line over MO/AR at 06Z this morning is expected to propagate eastward into the TN valley by 12Z Thu as a potent (albeit deamplifying) shortwave trough lifts NE from the lower Midwest through the OH valley. Despite decreasing/departing forcing, the ongoing squall line in the TN valley Thu morning is expected to propagate eastward into the southern Appalachians during the aft/eve. An increasingly hostile thermodynamic environment with eastward extent over the Carolinas should result in rapid weakening (and eventual dissipation) of the squall line as it progresses over/east of the Appalachians, however, it is possible that lingering convection could affect portions of the western Piedmont between 21-00Z before dissipation occurs. Outflow assoc/w the remnants of the squall line could result in gusty westerly winds and a 10-15F temperature drop in the Foothills/western Piedmont late Thu afternoon, complicating the temperature forecast. Will indicate a chance for showers and thunderstorms in the western Piedmont during the late afternoon, with dry conditions elsewhere and highs in the 80s, coolest west and warmest (mid/upper 80s along/east of Hwy 1). Expect warmer low Thu night (mid 60s) in assoc/w low-level moisture advection from the SW and likely development of low stratus during the pre-dawn hours. -Vincent && .LONG TERM /Friday through Tuesday/...
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As of 325 PM Wednesday... A weak surface tough associated with dying overnight convection is forecast to stall over the coastal plain and then retreat back to the west on Friday as the subtropical ridge amplifies off the Southeast coast. The ridge, and associated rising thicknesses will peak on Saturday (thicknesses of 1410-1420m), with highs accordingly peaking in the upper 80s to lower 90s, just short of record highs. Convection each day should mainly be tied to the seabreeze and higher terrain in southwesterly flow and no strong forcing. However, with strong instability forecast, owing to a plume of steep mid-level lapse rates off the Mexican Plateau, there could be a large hail and damaging wind threat, more so on Saturday when models suggest a shallow tropopause disturbance/jet moving lifting through the Deep South that could aid in triggering storms. Confidence in this feature and whether or not storms will be able to develop is still low at this point. The ridge will hold on Sunday and then give a little to a strong upper low forecast to lift from the Southern Plains to the Great Lake by Monday. POPs will increase on Monday as the associated cold front advances east across the mountains. Shear looks favorable for severe weather, but instability is questionable on Monday. Temps will accordingly be knocked back toward normal for the middle of next week.
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&& .AVIATION /18Z Wednesday through Monday/... As of 235 PM Wednesday... High confidence in VFR conditions for the next 24 hours. Yesterday`s deep low pressure system has moved well NE of the area, leaving behind drier air beneath a ridge of high pressure aloft. Scattered VFR clouds will largely dissipate this evening with loss of heating, leaving mainly clear skies overnight, followed by a redevelopment of flat daytime VFR cumulus clouds by late morning Thu. Surface winds will be light from the S or SW through tonight, then increase from the SW by 15z Thu to 12-15 kts gusting to around 20 kts late in the TAF valid period. Looking beyond 18z Thu, a line of showers and storms will approach the southern Appalachians from the west during the afternoon, then slowly weaken as it moves into central NC Thu afternoon through the evening and early overnight hours. Best chance of showers/storms will locally erratic winds/enhanced gusts and brief sub-VFR conditions will be at INT/GSO late Thu into the early evening. Other isolated storms are possible Sat and Sun afternoon/early evening, especially at INT/GSO, with a better chance areawide Mon as a front approaches. Sub-VFR fog and shallow stratus are possible each late- night through early-morning. -GIH && .HYDROLOGY... As of 230 PM Wednesday... High water in area creeks and drainage ditches continues to recede today, with residual scattered road closures appearing to be more infrastructure-related than hydrological. Main stem river flooding will likely persist for several more days, particularly over north central and northeast sections. See water.weather.gov/ahps2/index.php?wfo=rah for the latest forecasts and additional information. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Hartfield NEAR TERM...LT/GH SHORT TERM...Vincent LONG TERM...Smith AVIATION...Hartfield HYDROLOGY...WFO RAH

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