Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 260803 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 402 AM EDT Thu May 26 2016 .SYNOPSIS...Bermuda high pressure will extend over the area through Friday producing above normal temperatures. 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 340 AM Thursday... A string upper level ridge, weakened slightly on the northwest periphery by disturbances moving through the TN Valley, continues to hold across the Southeast US, while Bermuda high pressure has become anchored offshore. Outside of debris cloudiness this morning and a patch of mid-clouds approaching the northwest Piedmont, skies will be partly cloudy to mostly sunny today. Weak and mostly uninhibited CAPE may support a few showers and storms drifting east off the higher terrain and into the western Piedmont late this afternoon, a scenario generally supported by most CAM`s. The airmass is largely unchanged since yesterday, so highs should again be in the 84-89 range. 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). && .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/...
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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.
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&& .AVIATION /06Z Thursday through Memorial Day/... As of 145 AM Thursday... Strong high pressure over the Southeast US will continue to promote VFR conditions through the TAF period. Dewpoints have come up a few degrees since last night, so there may be a few pockets of MVFR visibilities by 12z despite the thin high level debris clouds drifting overhead. Otherwise, a light southwesterly wind will prevail today, with just a small chance of a brief shower or storms at KINT/KGSO after 20z as convection drifts east off the mountains. Long term: More chances for sub-VFR conditions for the end of the week as a plume of moisture moves in from the southwest Atlantic that could affect the area for several days. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...CBL/BLS NEAR TERM...BLS SHORT TERM...BLS LONG TERM...26 AVIATION...BLS/Ellis

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