Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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528 FXUS62 KRAH 230702 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 305 AM EDT Wed May 23 2018 .SYNOPSIS... A warm and humid southwest flow will hold over the area today. A cold front will approach from the northwest this afternoon, and then push southeast through North Carolina tonight. This front will settle across South Carolina Thursday through Friday, as high pressure builds in from the northeast. && .NEAR TERM /THROUGH TONIGHT/... As of 250 AM Wednesday... Looks like a good shot at a few strong to marginally severe storms this afternoon into early evening. The latest surface map shows a frontal zone extending through the Ohio Valley NE to W NY then SE through the Delmarva peninsula. The remnants of last evening`s convection are crossing SE VA in the form of patchy showers, while a more organized W-to-E prefrontal band of storms bisects WV. Soupy air holds over NC, with a light SW flow and dewpoints in the mid- upper 60s contributing to lingering weak CAPE (offset by widespread CIN). Accompanying the surface front is a mid level trough axis, and both of these features will progress ESE through the day, resulting in an increase in deep layer shear over NC, most markedly over far N and NE sections. Decent insolation in the warm sector today is likely to push temps up into the mid-upper 80s, and with dewpoints holding fairly steady despite mixing, moderate CAPE peaking at 2000- 2500 J/kg is expected. But the forecast lapse rates (6.0-7.0 at 925- 700 mb and 6.0-6.5 at 700-500 mb) are good but not remarkable, and the deep layer shear will still be muted at around 25-30 kts at most (highest in the NE CWA), limiting storm severity. Dynamic forcing for ascent will also be marginal, with weak upper divergence and weak mid level DPVA, along with decreasing low level winds as the cold front approaches. That said, the potential destabilization and improving winds aloft still support a few strong to marginally severe storms, mainly along and N of the Highway 70 corridor, with both damaging winds (given forecast downdraft CAPE over 1200) and large hail (with decent -10C to -30C CAPE projected and a lot of hail-heavy analog events) possible. Storms are expected to become more organized roughly along the Highway 64 corridor late this afternoon, then propagate to the ESE out ahead of the front itself. Will trend pops up to high chance in the far N before going up to likely, moving from N to S as the cold pool translates to the S during the evening and early overnight hours. Will finish up the night with lingering showers and isolated storms over the far S CWA late. Expect lows in the mid-upper 60s. -GIH && .SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/...
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As of 305 AM Wednesday... All but the southern third of the forecast area is expected to be mostly dry. The broad mid level trough will continue to push ESE and offshore Thu morning, while the surface cold front will have settled just to our south, as high pressure builds in from the N. Models depict a lingering moisture axis near the front spanning southern NC through Thu/Thu night, with warmer temps and higher dewpoints here supporting scattered showers and perhaps a few storms. Will retain low chance pops and mostly cloudy skies across the S Thu, with no pops and fair skies over the N. Highs from the lower 80s N to mid 80s S. As the low level anticyclone center moves over and off New England, the degree and depth of low level upslope-directed flow should allow low pops to drift into the SW CWA, and will hold only 15-25% rain chances across the SW sections Thu night. Fair skies elsewhere. Lows from the upper 50s NE to the mid 60s S. -GIH
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&& .LONG TERM /THURSDAY THROUGH TUESDAY/... As of 235 PM Tuesday... Progressive high pressure over the Great Lakes will make a stab at drying us out, pushing a front south of the area early on Thursday. With the front along or south of the area, will have only small chance PoPs along the southern tier counties Thursday into Thursday night. Highs will be only mildly influenced by the front due to strong insolation and should reach mostly mid 80s. The high moves off the New England coast, with return flow beginning to spread into the west Friday into Saturday. As such, chance category PoPs in the west Friday taper off eastward, with all areas in the low chance category on Saturday as we sit beneath an upper ridge conducive to airmass thunderstorms in the resulting unstable, but weakly forced environment. Highs both days will mostly reach mid 80s after mild morning lows in the mid and upper 60s. The moisture transport from the south returns once again for the late weekend aided by the Bermuda high and a developing low pressure system in the Gulf of Mexico. The moisture return will increase precip coverage Sunday and into early next week, and while there is a lot of uncertainty as to the timing of forcing mechanisms driving heavier convection, it will be diurnally influenced, and will maintain high chance to likely PoPs Sunday through Tuesday. Highs will show little variation from previous days, mostly mid 80s, with morning mins in the soupier airmass closer to 70 each morning. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/... As of 1235 AM Wednesday... VFR conditions will dominate through the noon hour at all central NC terminals, although a period of MVFR cigs is possible 08z-12z this morning at INT/GSO within and behind a dissipating batch of light showers crossing the area. Otherwise, any other shower activity through the morning hours will be isolated and confined to the VA border region. By early afternoon, a band of scattered to numerous storms will develop across northern NC, sinking slowly to the SSE through the afternoon/evening as a cold front approaches from the NW. Storm chances will be greatest at INT/GSO/RDU/RWI 19z-01z and at FAY 22z-05z. Brief sub-VFR conditions with strong/shifting winds and hail are possible with any of these storms from mid afternoon through late evening. VFR conditions should then return after midnight as the cold front sinks just south of the area, allowing drier air to build in from the north. Looking beyond 06z Thu, there is a chance for brief late-night/early- morning stratus in the S (near FAY) early Thu, but otherwise VFR conditions and dry weather will rule over the region Thu into Fri as high pressure builds in from the N and NE. Early morning fog/stratus chances return Sat/Sun as the surface high moves out over the Atlantic, bringing a moist southerly return flow. Mainly afternoon/ evening shower/storm chances will resume Sat/Sun areawide. -GIH && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Hartfield NEAR TERM...Hartfield SHORT TERM...Hartfield LONG TERM...mlm AVIATION...Hartfield

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