Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 261716 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 115 PM EDT Thu May 26 2016 .SYNOPSIS...Bermuda high pressure will extend over the area through Friday. Meanwhile, a storm system will develop over the sub-tropical Atlantic and drift toward the Southeast U.S. coast through the holiday weekend. && .NEAR TERM /through tonight/... As of 1025 AM Thursday... A slightly unstable low level air mass this afternoon with sbcape values of 1000-1500 j/kg will interact with a weakening disturbance aloft to possibly trigger a few showers and t-storms late this afternoon and this evening. This potential appears best west of highway 1, with the greatest threat along the western periphery of our forecast area. Have adjusted/expanded slight chance pops to encompass most of the southern Piedmont and the western sandhills. At this time, atmosphere does not appear that it will support any severe storms as the shear is very weak/non-existent and instability weak. Thicknesses this afternoon projected to be near or slightly warmer than those observed Wednesday. Thus, max temps this afternoon should be comparable to yesterday, ranging from the mid 80s in the nw Piedmont, to the upper 80s/near 90 elsewhere. -WSS The surface ridge axis, accompanied by lower theta e air, will begin to slowly shift back west over eastern NC tonight, allowing for good radiational cooling conditions and a range of lows from 61-65 (coolest in the east). -BLS && .SHORT TERM /Friday through Friday Night/... As of 340 AM Thursday... Strengthening of the upper ridge and shifting of the surface ridge overhead will lessen the prospects of convection on Friday, compared even to the little chance there is today. If there is a chance it will again be int he northwest Piedmont, but even then the steering flow should keep any convection confined to the higher terrain. H10-H85 thicknesses will be around 1415m, yielding highs of 85- 90. Lows mostly in the lower 60s. && .LONG TERM /Saturday THROUGH Wednesday/... As of 400 AM Thursday... Downstream of a longwave trough that will migrate from the West Coast to the Rockies, an energetic southern stream will provide a steady feed of vorticity that will maintain a mean mid to upper- level low in the vicinity of the Bahamas/off the southeast U.S. coast. This upper low will evolve at the base of/beneath a strong ridge forecast to extend from the western Atlantic Ocean to central Canada. The flow between these features will direct a deep feed of moist SE flow, characterized by precipitable water values between 1- 2 standard deviations above normal, into the Carolinas/Middle Atlantic region throughout the period. Given the presence of the deep moist axis --including humid conditions at the surface characterized by dewpoints in the middle 60s to lower 70s, particularly from Sunday onward-- the air mass will be ripe for diurnally-enhanced showers and storms. In fact, the ultimate track of the now well-advertised surface low pressure, which may acquire sub-tropical or tropical characteristics off the southeast U.S. coast, will likely be secondary to the effects of the moist plume. Regardless, we should remain under the influence of ridging at the surface and aloft for much of Saturday, though with an initial band of showers and storms likely to spread inland /into the I-95 corridor/ during the afternoon. The forecast for the remainder of the period will include above average chances of showers and storms, particularly with heating of the humid boundary layer each day, and temperatures tempered by both onshore flow, and clouds and convection. && .AVIATION /18Z Thursday through Tuesday/...
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As of 115 PM Thursday... It`s highly likely that VFR conditions will persist across central NC through Friday. The exception will be a small risk for early morning fog, limiting the visibility to MVFR criteria for a brief period. In addition, isolated convection late this afternoon through this evening, and again Friday afternoon through the evening, will produce instances of MVFR ceiling and visibility. Aviation conditions on Saturday will vary between VFR and MVFR criteria as increasing moisture results in lowering cloud bases and an enhanced threat for afternoon and evening scattered convection. Sub VFR conditions appear more likely Sunday and Memorial Day due to an area of low pressure projected to be positioned off the GA/SC coast. Circulation around this feature could send abundant moisture into central NC, resulting in widespread cloud cover and scattered to numerous showers and thunderstorms. Aviation conditions may slowly improve by Tuesday, though periods of MVFR conditions are probable.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...CBL/BLS NEAR TERM...WSS/BLS SHORT TERM...BLS LONG TERM...26 AVIATION...WSS is the U.S. government's official web portal to all federal, state and local government web resources and services.