Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 250621 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 220 AM EDT SUN SEP 25 2016 .SYNOPSIS...
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A backdoor cold front will move southwestward through the area today, as a cooler air mass pushes in from the north. This front will weaken and move back northeastward as a warm front on Monday. Another cold front will approach from the west Monday night, and then slowly cross the region Tuesday through Tuesday night.
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&& .NEAR TERM /OVERNIGHT/... As of 1045 PM Saturday... Skies were mostly clear across central NC this evening as a weak ridge of high pressure aloft extended across the region. A surface cold front extended from the Tidewater region of VA northwestward into the central Appalachians. Due to the deep nw flow on the front side of the upper ridge, the sfc front will only edge slowly southwest into our region overnight. Thus, mostly clear skies will reign for most of the night for locations southwest of Raleigh, likely not becoming cloudy until close to or after daybreak. This may allow patchy or areas of fog to develop though not anticipating the need for a dense fog advisory at this time. Still expect to see a low deck of clouds infiltrate the northeast counties after midnight with a few sprinkles possible, especially near the VA border. Overnight temps should generally range between 65 and 70. && .SHORT TERM /SUNDAY and SUNDAY NIGHT/... As of 130 PM Saturday... A quick turn from summer to fall expected Sunday with some hybrid CAD expected into the Piedmont region Sunday and Sunday night. Sunday will bring much more fall-like conditions led by the cooling NE flow and cloud cover. The cooling conditions will be pushed down the eastern seaboard by surface high pressure (1025 MB) centered over SE Canada. The high pressure ridge is forecast to extend southward into NC/SC into Sunday night before the ridge axis moves east. Models still bring low stratus deep into our region with even a chance of light drizzle in the NW Piedmont by early Sunday afternoon. It appears that little if any QPF can be expected as the moist upglide is expected to be too shallow for anything more that a trace to 0.01 or 0.02 in the northwest zones, with nothing more than a sprinkle expected elsewhere. Highs will be much cooler with overcast skies in much of the region. Highs Sunday will be coolest in the north-central Piedmont where readings may hold in the 60s. Elsewhere, highs will range into the 70s across the south and west. The overcast may break into variably cloudy skies in the SE, otherwise extensive cloudiness is expected through the day into Sunday night. Lows Sunday night in the upper 50s to mid 60s. && .LONG TERM /MONDAY THROUGH SATURDAY/... As of 310 PM Saturday... Monday through Tuesday night: Surface high pressure is expected to shift eastward and off the Northeast U.S. coast on Monday, with any hybrid CAD eroding from SE to NW with possibly some lingering light precip (mainly west where the damming should linger the longest). High temps are expected to generally range from the mid to upper 70s north/northwest to the lower 80s south. A mid/upper level low will slowly wobble east and southward across the Great Lakes region early next week, allowing an associated cold front to to approach the area on Monday night into early Tuesday, then slowly cross the area on Tuesday into Tuesday evening as the cold front begins to become more parallel to the mid level flow (helping to slow its progress). With regard to any severe threat instability looks to be weak, however, deep layer shear is expected to be respectable. Thus, we could see a some storms even some weakly organization convection, but the severe potential will remain quite low. Highs Tuesday are generally expected to be in the upper 70s to lower 80s, with lows Tuesday morning in the mid to upper 60s and lows Wednesday morning ranging from the mid to upper 50s nw to the lower to mid 60s se. Wednesday through Saturday: the mid to upper level flow pattern is in question mid to late next week, with regard to what happens to aforementioned deep mid/upper low over the Great Lakes early next week. The latest GFS continue to show the feature becoming a deep trough and moving through the area Wednesday/Wednesday night, helping to push the front (which is expected to linger across coastal portions of NC on Wednesday) offshore and away from the area. Meanwhile, this is the second run in a row of the ECMWF showing the mid/upper low sinking southward towards our area mid week, and lingering the low as it becomes cut off from the westerlies. The 00Z ECMWF ensemble members didn`t show much support for the scenario, so will keep the forecast dry from Wednesday evening onward (but will need to watch this). Otherwise, surface high pressure is expected to build/extend into the area through the period, with highs and lows expected to be near to slightly below normal. && .AVIATION /06Z SUNDAY THROUGH THURSDAY/...
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As of 220 AM Sunday... RDU/RWI have already seen a trend toward IFR or low-end MVFR cigs as stratus pours in behind a backdoor cold front pushing toward the SSW through NC this morning. This low-end MVFR or IFR stratus will continue moving through the remainder of central NC through daybreak, with winds shifting to light (under 8 kts) from the NE or ENE. A period of MVFR vsbys is also possible this morning through 13z. Cigs will slowly lift to MVFR areawide by midday, with lowest cigs holding at INT/GSO, then to VFR at RWI/RDU/FAY by 19z while MVFR cigs hold at INT/GSO, through the end of the TAF valid period. A few light showers or sprinkles are possible at all sites today, with little to no risk of thunder. Looking beyond 06z early Mon morning, MVFR conditions will hold at INT/GSO with VFR cigs elsewhere through Mon morning, followed by VFR conditions areawide Mon afternoon/evening. IFR conditions are expected to develop late Mon night, trending to MVFR Tue morning with improving rain chances, as a cold front approaches slowly from the west. A period of sub-VFR conditions is likely late Tue into Wed as the front moves through with scattered to numerous showers and a few storms. Conditions will improve to VFR from west to east Wed night, lasting through Thu behind the front. -GIH
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&& .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Hartfield NEAR TERM...WSS SHORT TERM...Badgett LONG TERM...BSD AVIATION...Hartfield

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