Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 261837 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 235 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 /Today and Tonight/... As of 1030 AM Wednesday... A shortwave ridge aloft will build eastward over central NC today which will provide subsidence and drying over the area. Current visible satellite observations show some low level clouds over the region which are expected to break up by early afternoon due to heating and mixing. Breaking of these low level clouds will allow for plenty of warming in the afternoon. Lingering low-level moisture (dewpoints in the lower 60s) and highs in the upper 70s to lower 80s may result in scattered diurnal Cu at 3000-4000 ft AGL. Expect dry conditions as a capping inversion is present over the area due to mid-level warming/drying from shortwave ridge. Overnight, limited cloud cover and light winds will allow for radiational cooling and low temperatures in the upper 50s to low 60s. -LT Earlier discussion from 345 AM: A shortwave ridge aloft will build eastward over central NC today as an upper level low NE along the Mid-Atlantic coast. Although lingering low-level moisture (dewpoints in the lower 60s) and highs in the upper 70s to lower 80s may result in scattered diurnal Cu at 3000-4000 ft AGL, strengthening subsidence in the wake of the departing upper level low (and approaching shortwave ridge) will result in pronounced mid-level warming/drying and the development of a strong capping inversion over central NC this afternoon. This, combined with a thorough lack of forcing will result in dry conditions through tonight. Expect lows in the upper 50s to lower 60s. -Vincent && .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/... As of 355 AM EDT Wednesday... Classic summertime pattern emerges for late week and into the weekend under the influence of a strengthening ~590 dm H5 ridge over the western Atlantic. By Saturday, low-level thicknesses are progged to peak between 1410-1420m(40m above normal) with H8 temps warming to around 18C. Highs Friday 85 to 90, followed by upper 80s to lower 90s on Saturday, when we could challenge the record high max at RDU. Heights are forecast to lower slightly on Sunday, with highs Sunday similar to Friday`s temps. Rain/convective chances through the weekend will be limited by the dominate ridge. Will retain slight/small chance pops across the western Piedmont, where initial convective development in the nearby higher terrain could propagate downwind into the area. If storms do develop or move east into the area on Saturday, strong instability ~3000 J/Kg aided by steep lapse rates aloft associated with a modified EML, coupled with deep layer shear of ~25kts could support some vigorous updrafts capable of producing large hail and damaging thunderstorm winds. A closed upper level low and associated deepening sfc low lifting through the Upper Midwest will push a cold front into the area Monday afternoon/evening. Attendant cold front will bring a chance for showers and storms to the area Monday-Monday night with cooler temps following on Tuesday. && .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 continue to recede today, with residual scattered road closures more infrastructure- related rather 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...CBL AVIATION...Hartfield HYDROLOGY...Hartfield

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