Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 261057 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 657 AM EDT Thu Apr 26 2018 .SYNOPSIS... A warm front will retreat northward across the central Carolinas through this evening, immediately preceding an area of low pressure that will track across the Carolinas and into southern VA tonight. A trailing trough will linger over the southeastern U.S. Friday and Friday night. && .NEAR TERM /THROUGH TONIGHT/...
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As of 355 AM Thursday... Shortwave ridging over the TN Valley and srn Appalachians this morning will expand newd across the cntl Appalachians and Carolinas through early this afternoon. Meanwhile, a potent mid-upr level low this morning will continue to amplify across the lwr MS Valley early today, to nwrn AL by 18Z, before deamplifying newd across the srn and cntl Appalachians tonight, in response to an upstream "kicker" trough amplifying from the cntl Rockies to the srn Plains/lwr MS Valley. Focused forcing for ascent and CAA aloft will accompany the deamplifying wave, though with a weakening wind field as it deamplifies and devolves into an open wave over the Virginias by 12Z Fri. At the surface, a quasi-stationary front was analyzed at 08Z from s- cntl SC wwd across n-cntl GA/AL, to a 1009 mb low over e-cntl MS. A trailing cold front was analyzed swwd from the low, across cntl LA and the wrn Gulf of Mexico. The ern portion of the stationary front is forecast to retreat nwwd across the cntl Carolinas this afternoon. The models indicate a weak frontal wave will develop along the retreating boundary, while the parent wave now over e-cntl MS tracks enewd into the srn Appalachians by 00Z Fri. These lows are forecast to then track newd, in the lee of the Appalachians/across the Carolinas tonight. Broken to overcast altocumulus over n-cntl SC and srn NC this morning, related to convergence within a trough and weak frontal zone at 850 mb, is forecast to expand newd into cntl NC in a developing WAA regime in that layer, through midday. While no rain is expected to accompany this cloudiness, the retreat of the aforementioned warm front/moistening/weak destabilization may result in widely scattered showers over the srn half of cntl NC, roughly south of Highway 64, this afternoon. Temperatures are expected to range from around 70 over the nrn Piedmont to mid to perhaps upr 70s over the Sandhills and srn Coastal Plain - a slightly larger than average range given the presence of the frontal zone. Tonight: The probability of rain will rapidly increase across the srn and wrn Piedmont after sunset, as the aforementioned lead frontal wave lifts newd from SC. Weak instability may support a few rumbles of thunder during the evening there, though with most of that rain likely to hold west of Highway 1. A secondary band of convection will then likely accompany the parent wave of low pressure, beneath the focused forcing for ascent accompanying the upr wave, as they track across the remainder of cntl NC after midnight. Focused forcing for ascent and cooling temperatures aloft accompanying the upr wave may provide for a better chance of thunder embedded within that convective band, including some surface-based owing to theta-e advection/mixing and resultant moist neutral low level thermal profiles per bufr forecast soundings. Strong wind gusts may accompany the convective band, but a lack of more appreciable boundary layer moisture (ie. surface dewpoints only in the mid-upr 50s), and the aforementioned weakening of the height/wind fields aloft --and bulk shear values to around 35-45 kt-- as the upr wave deamplifies, suggests any severe threat will be low. Lows in the 50s.
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&& .SHORT TERM /FRIDAY AND FRIDAY NIGHT/... As of 350 AM Thursday... The deamplifying short wave lifts north, with its associated surface low passing across the Delmarva peninsula early Friday afternoon. A few lingering showers will be possible in the morning, with shower coverage increasing along with a chance for a few thunderstorms in the northeast during the afternoon as a weakening cold front edges slowly east across the area. Some sun ahead of the front will allow highs to reach the low to mid 70s. Cool air advection will be weak behind the front with predominantly westerly flow and scattered cloudiness overnight. Mins will range from around 50 northwest to mid 50s in the southeast. && .LONG TERM /SATURDAY THROUGH THURSDAY/... As of 350 AM Thursday... A reinforcing dry cold front will move across the area Saturday night. This front will precede the passage of a long wave mid level trof which will slowly edge east, its axis passing across the area Sunday night. So, despite dry conditions with plentiful sunshine this weekend, temperatures will be slightly cooler than normal through Monday, with highs mostly 70 to 75 each day after morning mins mostly in the mid and upper 40s. High pressure building in early next week will allow for the airmass to begin warming concurrent with height rises behind the upper trof passage. Conditions will be dry with mostly clear skies to accompany a warming trend Tuesday through late week. Highs Tuesday will edge into the mid and upper 70s, warming to the low and mid 80s on Thursday. Morning mins will follow a similar trend, from around 50 Thursday morning to the upper 50s Thursday morning. && .AVIATION /11Z THURSDAY THROUGH MONDAY/...
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As of 655 AM Thursday... VFR conditions are expected through mid-afternoon, before a warm front and accompanying chance of mainly VFR showers retreat nwd into cntl NC between 21-00Z. A strong upper level trough and related low pressure system will then track newd across w-cntl NC tonight. A band or two of heavy showers and a few storms ---and IFR-MVFR conditions-- will accompany the passing low pressure, with the greatest concentration and duration at Piedmont sites (INT/GSO/RDU). Outlook: A widely scattered shower will be possible Fri afternoon. Otherwise, VFR conditions are anticipated through early next week.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... NC...None. && $$ SYNOPSIS...MWS NEAR TERM...MWS SHORT TERM...mlm LONG TERM...mlm AVIATION...MWS is the U.S. government's official web portal to all federal, state and local government web resources and services.