Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 240716 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 315 AM EDT Thu May 24 2018 .SYNOPSIS... A cold front will push southward through North Carolina early this morning. This front will settle across South Carolina today through Friday, as high pressure builds in from the northeast. This high will then move offshore by the weekend, resulting in a return to moist and unsettled weather. && .NEAR TERM /THROUGH TONIGHT/... As of 245 AM Thursday... Isolated showers linger over central NC within the still-damp air ahead of the incoming backdoor front, stretching from SW NC across the Triad to extreme south-central and SE VA. Marginal elevated CAPE of 250-500 J/kg persists over central NC, helping to fuel these showers despite reduced dynamic forcing for ascent and a weak wind field. The mid level shortwave trough over the Northeast last evening will drop SE out over the W Atlantic this morning, leading to a flattening and weakening steering flow. Surface high pressure drifting from lower MI to N OH will build into our area from the north, pushing the front southward to near the SC this morning, with an expected drop in PW over all but the southern quarter of the forecast area. The dry air, subsiding column, and lack of instability will make for a dry forecast for all but the S and far SW CWA, closer to the surface front and within a low level upslope- directed flow, respectively. Models are in fairly good agreement on confining convection today to the far S (within moderate MUCAPE but marginal deep layer shear) this afternoon, translating into the SW CWA this evening as the low level E/SE flow deepens, causing a greater pooling of moisture over our SW Piedmont. Expect fair to partly cloudy skies across the N and NE today, with partly to mostly cloudy skies and chance pops across the S and SW. Thicknesses support highs just a couple of degrees lower than yesterday, 82-87, still slightly above normal. Expect lows tonight from around 60 N to the mid 60s S. -GIH && .SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/...
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As of 315 AM Thursday... The mid level ridge axis extending from NE of the Bahamas into the Southeast will start to be broken down by both a shortwave trough moving through the Upper Midwest into the W Great Lakes as well as by a weak but expansive mid level trough covering the Lower Miss Valley and Gulf of Mexico. Flow through the low and mid levels will strengthen from the SSE and S, drawing deepening moisture into S and W parts of central NC, with less influence over NE sections still within the scope of influence of the offshore-drifting low-level ridge. This will result in an increase in clouds, thickest over the S and W CWA, although precip chances won`t immediately increase substantially given the light winds through the column and lack of mechanisms to force ascent, as well as the clouds themselves which will decrease heating, thus limiting CAPE. Nevertheless, PW is forecast to rise well over 1.5" over the SW CWA, sufficient to keep chance pops in this area Fri through Fri night, with lower to no pops further NE. Expect highs to be similar to today, mostly lower to mid 80s. With the clouds and rebounding dewpoints, lows Fri night should respond accordingly, popping back up to above normal readings in the mid to upper 60s. -GIH
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&& .LONG TERM /FRIDAY THROUGH WEDNESDAY/... As of 330 PM Wednesday... Within relatively slow, blocked flow aloft across the CONUS during the medium range, the pattern over cntl NC will be dominated by a broad, re-loading trough centered over the GOM/Gulf coast states, and a downstream ridge extending across the top from the swrn N. Atlantic and cntl/ern Caribbean Sea nwwd across the upr Midwest. The (generally sly) flow between these two features will direct a plume of tropical moisture characterized by precipitable water values of 1.75 to 2.5" from the nwrn Caribbean Sea nwwd across the sern U.S., especially by early next week. At the surface, an initially cooler and drier continental air mass, accompanying modifying surface high pressure off the srn middle Atlantic coast, will extend wwd into NC on Fri. This ridge will then drift east of Bermuda through the weekend, with progressively modifying return flow throughout the sern U.S. through early next week. (Possibly tropical) low pressure over the GOM this weekend would likely meander slowly over the nrn GOM and Gulf coast states through the period owing to the ridge downstream, and over the top. Some "ring of fire" convection may skirt the wrn and srn Piedmont late Fri-Fri night, in a developing warm/moist advection regime directed there, with otherwise continued drier and more stable conditions in closer proximity to the offshore (deep layer) ridging. This regime will then likely edge ewd, with an associated good chance of showers and storms across cntl NC, on Sat. There may be a relative lull in convective probabilities/coverage, in briefly more pronounced ridging aloft downstream of the GOM low pressure, on Sun. It will then become increasingly unsettled, with high chance to likely probabilities of showers/storms, maximized with diurnal heating, Memorial Day through the middle of next week. High temperatures are likely to be near to slightly above normal, though modulated/hindered by convection/clouds especially early-mid next week, while low temperatures are likely to be a category or three above normal for the same reason. && .AVIATION /06Z THURSDAY THROUGH MONDAY/... As of 150 AM Thursday... The scattered showers and storms over central NC this past evening have largely diminished, although a brief shower producing MVFR conditions is possible 06z-08z at RWI. Otherwise, VFR cigs will hold through daybreak, although INT/GSO/RDU may see a short period of MVFR cigs between 08z and 13z. After 13z, there is high confidence that VFR conditions will dominate today through tonight. A surface cold front now dropping southward through NC will settle just to our south, as high pressure builds in from the north. This will result in a largely dry day, with the only shower/storm threat expected to be across the south, mostly south of FAY, during the afternoon through mid evening. In general, only VFR mid and high clouds are expected across the area, lasting through the end of the TAF valid period. Surface winds will be less than 10 kts from the NE for much of the day. Looking beyond 06z Fri, VFR conditions are likely to hold overnight, although FAY may see scattered clouds based around 3000 to 4000 ft AGL 08z-12z. Just scattered to broken VFR afternoon cumulus is expected Fri afternoon, with a chance of showers near INT/GSO/FAY from mid afternoon through Fri night. Sub-VFR conditions are expected late Fri night through daybreak Sat as moisture returns across the area. Daily rain chances will resume Sat afternoon into Mon, mainly affecting INT/GSO, as an upper level trough approaches from the west. Sub-VFR stratus/fog may impact all central NC terminals early each morning Sun/Mon. -GIH && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Hartfield NEAR TERM...Hartfield SHORT TERM...Hartfield LONG TERM...MWS AVIATION...Hartfield

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