Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 271441 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 1042 AM EDT SAT AUG 27 2016 .SYNOPSIS... An upper level ridge will persist over the region through the weekend. An upper level disturbance over the Atlantic will then drift west and linger over the Southeast states early next week. && .NEAR TERM /THROUGH TONIGHT/...
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As of 1042 AM Saturday... 12Z upper air analysis along with the 14Z meso analysis suggest that best chance for scattered convection this afternoon across roughly the south half of our forecast area. A mid/upper level anti-cyclone positioned to our north will maintain a deep ely flow over our region with the best moisture confluence across the sandhills and the southern piedmont. While the atmosphere will be slight- moderately unstable across the northeast piedmont/northern coastal plain, difficult to discern any mechanism to initiate lift, aside from strong heating. Even across the southern counties, little if any support discernible aloft to initiate/sustain convection. Thus, appears we will need to rely on orographic lift and residual outflow boundaries from previous days convection along with strong heating to initiate lift. With the meso analysis depicting the best moisture axis residing across our southern and western counties, should see the greatest concentration of convection in this part of the forecast area (though no worse than scattered (30-40 percent)). A few strong storms possible with the main hazard being strong gusty winds ~40-45kts and frequent lightning. This has been addresses in the latest HWO product. Afternoon temps in track to reach the low-mid 90s. Counting on some cloud build up/scattered convection to moderate temps a little this afternoon. If this does not occur, places such as Fayetteville and Laurinburg may reach the upper 90s. Afternoon heat index values expected to vary from 98-102 degrees across the north and 102-105 degrees across the south. Do not plan an advisory at this time but will continue to monitor. What convection is occurring at 6 PM will quickly diminish/dissipate around sunset. Under clear-partly cloudy skies, overnight temps will lower into the low-mid 70s.
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&& .SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/... As of 350 AM Saturday... The upper level ridge will continue a northward drift on Sunday, while an upper disturbance over the Atlantic slowly drifts west and undercuts the ridge, essentially settling over the Southeast US through early next week. This disturbance along with increasing moisture flux off of the Atlantic - PW increasing to around 2 inches - and weak to moderate instability will likely result in enhanced convective coverage along the coast, drifting inland through the day. Coverage will be best over the coastal plain, diminishing with westward extent into the Piedmont where deeper mixing and drier air will limit coverage. Some of the showers may continue into the evening and overnight hours, mainly across the southern coastal plain. Highs 89-92, warmest west. Lows 69-74. && .LONG TERM /MONDAY THROUGH FRIDAY/... AS OF 350 AM Saturday... WV imagery this morning depicts an increasingly well-defined mid to upper level low a few hundred miles SW of Bermuda. The forecast models continue to indicate this feature will drift W --around the SRN periphery of an initially strong sub-tropical ridge over the Central Appalachians and Middle Atlantic states-- and stall along the SE U.S. coast early next week. Divergence and upper level venting in the deformation zone to the N of the low /over NC/ in conjunction with convergence along the sea breeze, will support a chance of diurnal convection over the ERN half of our forecast area, also where boundary layer moisture is forecast to be most plentiful, Mon afternoon-evening. The presence of the mid-upper low and associated height falls will also cause the preceding sub-tropical ridge to split, with an associated positively-tilted trough/shear axis expected to evolve invof the SERN and SRN Middle Atlantic coasts through mid week. While this weakness in the ridge will provide a corridor through which low pressure associated with the tropical wave now over the central Bahamas could pass --up the coast and mostly E of central NC-- this system remains disorganized and the probability of any appreciable development at all decreases with each passing day - now 40 percent or less per the NHC. It will nonetheless bear watching and remain a forecast concern for FL and the adjacent Gulf and SERN U.S. coastal areas during the next few days. Thereafter, the aforementioned split in the sub-tropical ridge will cause the main ridge center to retrograde and strengthen over the central U.S., with accompanying downstream trough development in the ERN U.S. through the end of the week. The models indicate an associated NRN stream cold front will settle through the SRN Middle Atlantic states and Carolinas Thu-Fri, with an accompanying chance of convection maximized in central NC on Thu, followed by cooler and drier conditions in post-frontal high pressure ridging across the Middle Atlantic region, on Fri. && .AVIATION /12Z SATURDAY THROUGH WEDNESDAY/... As of 640 AM Saturday... Currently VFR at TAF sites, with MVFR vsbys around the northern Piedmont. Vsbys may still briefly fall to 4-6sm at the TAF sites prior to 13z. There are also a few isolated showers moving southwest through the northern coastal plain, but the chance of one moving over RWI is very low. Models continue to suggests widely scattered showers and storms are possible this afternoon with an easterly flow setting up. These should mostly be confined to an area from KFAY to just south of KGSO/KINT, though confidence is low given very little forcing to initiate storms. Will indicate the best chance at KFAY after 19z. Afternoon storms will diminish after sunset, and most of the night will be VFR. East-northeasterly flow will support stratus across the coastal plain late tonight, so have included some IFR ceilings at KRWI and KFAY after 09z. Long Term: VFR conditions are expected to prevail over the next few days, with after noon showers and storms mostly confined to the eastern areas of NC. Some early morning fog/stratus will also be possible. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...BS NEAR TERM...WSS SHORT TERM...BS LONG TERM...MWS AVIATION...BS

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