Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 240735 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 335 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/... 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 && .LONG TERM /SATURDAY THROUGH WEDNESDAY/...
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As of 335 AM Thursday... Much of the long term forecast will be consumed by what could be our first tropical system of the year coming out of the Gulf of Mexico. The current tropical weather outlook from the National Hurricane Center gives the system a 70% chance of formation within the next five days. Regardless of if that happens or not, the result for central NC will be the same. That is, a lot more moisture over the area and rain chances through the long term forecast. This is the first hint we have seen at longer term deterministic models coming into better agreement on where the storm might end up. For Saturday, both simulations put the storm between Western Cuba and Southwest Florida with the EC solution further west. That is important because that scenario is mirrored through the forecast with the GFS bringing the system into the Florida Panhandle and into GA/AL before dissipating and being caught up in the northern stream flow. The EC solution stays west and brings the system into Louisiana on Monday evening before moving it north into Mississippi and spinning it there for several days. Both of these scenarios bring a wave of heavy rain through the Carolinas Sunday afternoon through Monday which could be our wettest period. Chances for rain and thunder will be present throughout the period but like recent afternoons, expect some breaks in the rain in time and space and that could leave some folks dry for periods of time. While rain will definitely be a concern for central NC given that we have already had an extended period of wet weather, wind is not expected to be a problem in this area. Temperatures through the period will top out in the 80s with lows in the upper 60s to low 70s making it very humid throughout the long term forecast.
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&& .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...Ellis AVIATION...Hartfield

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