Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 270021 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 820 PM EDT Wed Apr 26 2017 .SYNOPSIS... A high pressure ridge will build eastward over the Carolinas this afternoon into tonight. A weakening cold front will approach the mountains from the west on Thursday, then dissipate over the Mid- Atlantic Thursday night. && .NEAR TERM /through tonight/... As of 250 PM Wednesday... Expect a quiet night as mid level ridging builds over the area from the SW, and deep subsidence takes place in the wake of the deep low now drifting off the Northeast coast. Flat scattered to broken cumulus clouds over the area will dissipate with loss of heating this evening, resulting in mostly clear skies overnight with a light wind from the S or SW. Expect decent (although not ideal) radiational cooling tonight, and with elevated dewpoints, lows will be mild tonight, in the upper 50s to lower 60s. -GIH && .SHORT TERM /Thursday and Thursday Night/... As of 335 PM Wednesday... Skies will be generally sunny for much of Thu morning, with the mid level ridge axis sliding to our east, although high clouds will be increasing as the weakening line of convection approaches from the west, along with a weakening surface trough that brushes our W and N sections late Thu through Thu night before lifting up into the Mid Atlantic region. Warm and stable 850-600 mb air will inhibit convection in our area through early afternoon, despite surface dewpoints within a few degrees of 60, and this is further supported by the latest hi-res WRF-ARW/NMM runs which stay dry in our area through 18z. By mid afternoon, however, a weakened version of the convective line will be moving into the western CWA, accompanying a 30-40 kt 850 mb SSW jetlet, weaker than its previous state but still enough to support low level mass convergence over central NC, mainly from very late afternoon until shortly after midnight. Forecast soundings show mostly elevated instability increasing by evening, peaking in the 800-1200 J/kg range, and deep layer shear ranging from around 40 kts west to around 20 kts east, with column moistening as high PW values of 1.5-1.75" advect in from the SW. Detrimental to maintenance of this convection will be the lack of dynamic forcing for ascent, as any weak DPVA will track well to our NW, although models do indicate a pocket of enhanced upper divergence tracking NE through the area Thu evening, which may support greater storm coverage. For now, will hold onto low-end likely pops west, with lower chances through the central CWA and just small chances east, where deep layer shear and dynamic forcing for lift will be weaker closer to the departing ridge. With thicknesses higher than yesterday tempered by the increase in clouds, expect highs from near 80 NW to the mid 80s SE. Lows Thu night ranging from the low 60s NW to the upper 60s SE. -GIH && .LONG TERM /Friday through Tuesday/... As of 325 PM Wednesday... A weak surface tough associated with dying overnight convection is forecast to stall over the coastal plain and then retreat back to the west on Friday as the subtropical ridge amplifies off the Southeast coast. The ridge, and associated rising thicknesses will peak on Saturday (thicknesses of 1410-1420m), with highs accordingly peaking in the upper 80s to lower 90s, just short of record highs. Convection each day should mainly be tied to the seabreeze and higher terrain in southwesterly flow and no strong forcing. However, with strong instability forecast, owing to a plume of steep mid-level lapse rates off the Mexican Plateau, there could be a large hail and damaging wind threat, more so on Saturday when models suggest a shallow tropopause disturbance/jet moving lifting through the Deep South that could aid in triggering storms. Confidence in this feature and whether or not storms will be able to develop is still low at this point. The ridge will hold on Sunday and then give a little to a strong upper low forecast to lift from the Southern Plains to the Great Lake by Monday. POPs will increase on Monday as the associated cold front advances east across the mountains. Shear looks favorable for severe weather, but instability is questionable on Monday. Temps will accordingly be knocked back toward normal for the middle of next week. && .AVIATION /00Z THURSDAY THROUGH MONDAY/...
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As of 820 PM Wednesday... 24 Hour TAF Period: VFR conditions are generally expected to continue through the 24 hour TAF Period. Mid level ridging is expected to shift to the east of the area overnight, allowing for a cold front to approach the area tonight into Thursday. This will allow for a south to southwesterly 5 to 10 mph wind overnight, increasing to 10 to 15 mph by mid morning tomorrow, with gusts in the afternoon of 20 to 25 mph. Very late in the TAF period, we could see a few showers and storms affect KGSO/KINT, possibly resulting in sub-VFR conditions. Outlook: Any storms that move into the area late afternoon/early evening Thursday will weaken as they moves into central NC. Other isolated storms will be possible Sat and Sun afternoon/early evening, especially at KINT/KGSO, with a better chance areawide Mon as a cold front approaches. Sub-VFR fog and shallow stratus will be possible each late-night/early-morning as well.
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&& .HYDROLOGY... As of 230 PM Wednesday... High water in area creeks and drainage ditches continues to recede today, with residual scattered road closures appearing to be more infrastructure-related than hydrological. Main stem river flooding will likely persist for several more days, particularly over north central and northeast sections. See for the latest forecasts and additional information. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Hartfield NEAR TERM...Hartfield SHORT TERM...Hartfield LONG TERM...Smith AVIATION...BSD/Hartfield HYDROLOGY...WFO RAH is the U.S. government's official web portal to all federal, state and local government web resources and services.