Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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707 FXUS62 KRAH 260755 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 354 AM EDT Wed Apr 26 2017 .SYNOPSIS...
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A shortwave ridge aloft will build into the Carolinas from the west in the wake of the upper level low lifting northeast along the Mid- Atlantic coast. A moist southerly return flow on the western periphery of an offshore ridge and southwest flow aloft downstream of troughing over the central CONUS will prevail late this week through the weekend.
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&& .NEAR TERM /Today and Tonight/...
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As of 900 PM Tuesday... 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
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&& .SHORT TERM /Thursday and Thursday Night/...
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As of 345 AM 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
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&& .LONG TERM /THURSDAY THROUGH TUESDAY/... As of 330 PM Tuesday... A fairly stout upper trough will lift out of the southern Plains on Thursday, though the core of the upper forcing will pass through the Ohio Valley. Limited moisture transport off the GOMEX and lack of better forcing should result in a decreasing chance of convection as the front attempts to cross the mountains late Thursday. The front it self may nit actually make it across the mountains, so just a few showers are possible as a pre-frontal trough moves into the Piedmont. A sub-tropical ridge will then expand across the Southeast through the weekend as an upper low develops over the southwest US, resulting in thicknesses nearing 1410m and near record heat peaking Saturday. these thicknesses support highs climbing in the upper 80s and lower 90s, about 10-15 degrees above normal. Climatological convective chances will be diurnally driven and focused in the higher terrain, though GFS forecast soundings indicate rather strong instability by Saturday, which is plausible given that the upper ridge is centered to our south and the cap will be weaker to the north. Height aloft then lower Sunday and Monday as the aforementioned upper low lifts toward the Great Lakes, but the influence of the upper ridge may still be felt over the east, leading to highs more in the lower 80d west to upper 80d east. A stronger cold front attendant to the upper low will is forecast to move through Monday, bringing a better chance of showers and storms and temps falling back toward normal by the middle of next week. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
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As of 230 AM Wednesday... 24 Hour TAF Period: Challenging aviation forecast. Conditions ranged from VFR to LIFR across central NC at 06Z this morning. Expect MVFR/VFR ceilings at the Triad terminals with a potential for MVFR fog 09-12Z. Expect MVFR/IFR ceilings at eastern terminals this morning. Ceilings will lift to VFR (3000-4000 ft AGL) at all terminals by early afternoon. A westerly wind at 5-10 knots this morning will back to the SW/SSW at ~10 knots this afternoon, then become light/variable after sunset. Looking Ahead: Sub-VFR conditions assoc/w the remnants of a weakening squall line are expected to affect the western Piedmont (INT/GSO) late Thu aft/eve. With an offshore ridge, expect a persistent southerly return flow over the Carolinas through the weekend. As such, expect a potential for IFR/LIFR stratus each morning (08-13Z). A conditional potential for isolated severe thunderstorms will exist during the late afternoon hours Fri/Sat/Sun across western portions of the state, potentially affecting the INT/GSO terminals (should convection develop and/or propagate into the area). -Vincent
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&& .HYDROLOGY...
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As of 230 AM Wednesday... Small creeks and streams will gradually recede over the next 24 hours. Main stem river flooding will likely persist for several more days. See water.weather.gov/ahps2/index.php?wfo=rah for the latest forecasts and for additional information.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Vincent NEAR TERM...Vincent SHORT TERM...Vincent LONG TERM...SMITH AVIATION...Vincent HYDROLOGY..Vincent/MLM

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