Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 281847 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 247 PM EDT Fri Apr 27 2017 .SYNOPSIS... A warm moist southerly flow will continue through the weekend, as a deep high pressure ridge strengthens off the Southeast coast. && .NEAR TERM /Today and Tonight/... As of 1030 AM Friday... Forecast is on track. 12z GSO sounding reveals a cap in the 850-750 mb layer which has helped to trap moisture beneath it within a weak wind regime, resulting in stubborn stratus in the Triad and stratocu elsewhere. As surface winds strengthen across the area in the next few hours, horizontal dispersion should help mix out and lift the remaining low clouds, resulting in partly cloudy skies for much of the day areawide. Convection chances still appear slim, given the cap and falling PW values in the wake of the early-morning showers/storms now moving off the NE NC coast. But lapse rates aloft are fairly steep and projected to top out over 7 C/km this afternoon over the Coastal Plain, which could spur development of isolated storms in our far SE, although deep layer shear will be less favorable there (just 25 kts) compared to further west, thanks to the building ridge just off the coast. Recent runs of convection- allowing models support limited to no convection over central NC today. Will maintain a dry forecast, although an isolated cell or two remain possible where local effects can prompt sufficient mass convergence and forced ascent. Expect highs today in the mid 80s to lower 90s, except for lower 80s in the immediate Triad region where insolation will be reduced. -GIH Earlier discussion from 300 am: Extreme destabilization (3000-3500 J/Kg MLCAPE) is expected today as rich low-level moisture advects poleward beneath a modified elevated mixed layer /steep mid-level lapse rates/ in the presence of unimpeded insolation. Despite atypically favorable thermodynamics, a strong cap at the base of the EML combined with the absence of any discernible forcing is expected to preclude convective development. Convective inhibition will be greatest over western portions of the state where afternoon temps will top out in the mid 80s (versus ~90F in eastern NC). Unless a well-timed shortwave/MCV in SW flow aloft progresses across western NC or upstream convection propagates downstream into western NC (neither are likely based on the latest mesoanalysis/observational data and short term model guidance), convective development is highly unlikely. Erosion of CINH will be greatest in eastern NC this afternoon where weak low-level convergence will be present in assoc/w the seabreeze (assuming it penetrates inland). However, such weak/shallow forcing is unlikely to break the cap nor sustain updrafts in the presence of such a dry mid-level airmass. It is fortunate that deep convection is unlikely to develop considering that thermodynamic/kinematic profiles would strongly support robust supercells capable of producing destructive hail/microbursts. With a moist low-level return flow and expected development of stratus, expect overnight lows in the mid 60s to lower 70s. -Vincent && .SHORT TERM /Saturday and Saturday Night/... As of 300 AM EDT Friday... Thermodynamic conditions on Saturday will be very similar to today, though kinematic profiles are progged to be weaker. Regardless, a strong cap and lack of forcing is once again expected to preclude convective development. Expect above normal highs in the lower 90s with lows Sat night in the mid/upper 60s to lower 70s. -Vincent && .LONG TERM /SUNDAY THROUGH FRIDAY/...
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As of 247 PM EDT Friday... Sunday the surface high will retreat eastward as a low pressure system moves across the central plains with a cold front extending down the Mississippi Valley. This will keep central NC in the southwesterly return flow regime and the warm temperatures will continue. Expect highs in the low to upper 80s with highest temperatures across the east with increasing clouds in the west keeping conditions cooler. Most of the day should be dry but cant rule out a stray afternoon shower or thunderstorm. The system to the west will cross the area Monday and Monday night, thus chances for precipitation go up considerably by Monday afternoon. Thunder will certainly be possible but the chances for severe seem pretty low at this time. Models are having a hard time nailing down how much QPF will be realized at this time. The front will come through and precipitation threat will end by daybreak on Tuesday. Behind the front, temperatures will moderate back into the mid to upper 70s. More of the same for Wednesday with temps rising back into the lower 80s in the east. By Thursday precip chances begin to increase once again as the Gulf of Mexico opens up and a series of shortwaves march towards the Carolinas with a stronger low pressure system forming by the end of next week into the weekend. This will keep weather unsettled with the treat for showers and storms Thursday and Friday with temperatures backing off into the 70s on Thursday and the upper 60s on Friday.
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&& .AVIATION /18Z Friday through Wednesday/... As of 145 PM Friday... After patchy sub-VFR conditions this morning, scattered to broken cloud bases have risen to VFR, where they will remain through this evening, with no vsby restrictions. Beginning soon after midnight, however, abundant low level moisture will lead to redevelopment of IFR cigs, most likely after 07z, at all TAF locations. Winds will stay up at 8-12 kts overnight, favoring clouds over fog, so vsby restrictions should be no worse than MVFR for most of tonight, and most places will see VFR vsbys dominate. The prevailing IFR cigs will rise to MVFR after 14z or so, then to VFR after 16z or so, with a breeze from the SW sustained at 10-15 kts after 14z. Storm chances will be very low through 18z Sat, less than 10%. Looking beyond 18z Sat, VFR conditions will hold through Sat evening, with once again a very low chance of any storms in central NC, although scattered showers/storms are possible in the mountains Sat afternoon. The same scenario is expected Sat night/Sun, with a good chance of sub-VFR stratus late Sat night into Sun morning, followed by VFR conditions the remainder of Sun, and afternoon storm chances confined to the mountains. The risk for sub-VFR conditions will increase Sun night through Mon, with a better chance of showers and storms Mon through Mon night as a cold front approaches from the west (although this front will dissipate before it gets into the area). VFR conditions are expected Tue into Wed. -GIH && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Hartfield NEAR TERM...Hartfield/Vincent SHORT TERM...Vincent LONG TERM...Ellis AVIATION...Hartfield

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