Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 210618 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 217 AM EDT SUN AUG 21 2016 .SYNOPSIS... An upper level trough and attendant cold front approaching the mountains from the west this morning will progress east through the Mid-Atlantic and Carolinas this evening into tonight. In the wake of the front, dry high pressure will build into the region from the west through mid-week. && .NEAR TERM /TODAY AND TONIGHT/... As of 145 AM Sunday... Westerly flow aloft will strengthen over the region today as an upper level low progresses ENE through the Upper Great Lakes into southern Canada, additional shortwave energy digging southeast through the central MS river valley amplifies an upper level trough over the OH valley and Great Lakes, and an attendant cold front approaches the mountains from the NW, progressing through central NC this evening/tonight. Expect the best potential for convection north of hwy 64 (closer to stronger DPVA progressing into the Mid- Atlantic) during the late afternoon and evening hours (21-03Z) as the surface cold front /low-level trough/ progresses into the region around/shortly after peak heating in the presence of above normal moisture and moderate destabilization. Deep moisture /cloud-cover/ and weak mid-level lapse rates may temper instability such that more favorable deep layer shear attendant stronger flow aloft may not be fully realized/capitalized upon by updrafts at this latitude, though NAM forecast soundings from the Triangle NE into the Coastal Plain show ~1500 J/kg MLCAPE and sufficient shear for SCP values of 1-2 around 23-00Z. Uncertainty remains high with regard to convective evolution (timing/location/coverage/organization), though the latest convection allowing models have trended toward decreased coverage confined primarily along/north of hwy 64. Despite weak mid-level lapse rates and weak DCAPE, brief supercellular organization possible across the northern Piedmont and NE Coastal plain would support an isolated potential for damaging winds (aided by precip loading and downward momentum transport) and marginally severe hail. Expect convection to end from west-east this evening/night (by midnight) as the surface front /low-level trough/ progress toward the Carolina coast. Expect highs in the upper 80s to lower 90s and lows tonight driven by weak cold advection behind the front, ranging from the lower/mid 60s W/NW to lower 70s far SE. -Vincent && .SHORT TERM /MONDAY AND MONDAY NIGHT/... As of 145 AM Sunday... Synoptic subsidence in the wake of the upper level trough progressing offshore the Mid-Atlantic coast tonight will increase surface pressure over the Ohio Valley and Appalachians during the day Monday, aiding the advection of a drier airmass into the Carolinas from the NW. Expect clear skies and a light NW breeze with highs ranging from the lower/mid 80s NW to upper 80s SE. High pressure will build east into the Mid-Atlantic Monday night, with a sfc ridge axis extending SE into the Carolinas. With a much drier airmass in place (dewpoints in 50s) and clear/calm conditions, lows may fall below 60F into the upper 50s Monday morning, primarily across the N/NW Piedmont, with lows in the lower/mid 60s elsewhere, warmest in the SE coastal plain. -Vincent && .LONG TERM /TUESDAY THROUGH SATURDAY/...
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As of 217 AM Sunday... Ridging, both sfc and aloft, will promote a continuation of dry weather across our area right through the work week. In addition, look for little airmass change from Monday, so highs in the mid 80s, lows in the mid 60s, and dewpoints in the low-mid 60s will continue right through Thursday. By Friday we`ll begin to see the airmass moderate to above-normal readings as the sfc ridge axis moves offshore and southerly flow re-establishes over our area. On Saturday, the next cold front will drift south toward then stall across our area. While the front will bring a slight chance for showers/tstms, given limited moisture, right now it appears that most of the day Saturday should remain dry.
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&& .AVIATION /06Z SUNDAY THROUGH THURSDAY/... As of 155 AM Sunday... 24-hr TAF period: Expect VFR conditions to prevail this morning through advance of a cold front approaching the mountains from the west. Sub-VFR conditions attendant convection expected to develop along the front during the late afternoon and evening hours (21-03Z) will be possible at all terminals, though most likely at northern terminals, especially RDU/RWI. An isolated severe thunderstorm with sfc wind gusts AOA 50 KT cannot be ruled out. Expect WSW winds of 5-10 kt with gusts up to 15 kt this afternoon to become NW at 5-10 kt in the wake of the front this evening/early tonight. Looking Ahead: VFR conditions and light winds will prevail through mid-week as dry high pressure builds eastward from the OH Valley into the Mid-Atlantic. -Vincent && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Vincent NEAR TERM...Vincent SHORT TERM...Vincent LONG TERM...NP AVIATION...Vincent is the U.S. government's official web portal to all federal, state and local government web resources and services.