Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 221925 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 220 PM EST Sun Jan 22 2017 .SYNOPSIS... A potent low pressure system will track northeast from the Deep South into the Carolinas tonight, linger over the area on Monday, then track off the Mid-Atlantic coast on Tuesday. && .NEAR TERM /TODAY AND TONIGHT/... As of 1040 AM Sunday... No major changes evident in the large scale flow, with a deepening upper low over the ArkLatex region this morning and the associated 994mb surface low just downstream over Arkansas. Still expect intense deep layer lift as upper diffluence and DCVA increase rapidly after 00Z and a 50kt LLJ translates east across SC/GA. A QLCS will develop across GA/AL/FL Panhandle by early afternoon (the initial stages may be just getting going south of Mobile), and expand north toward the Carolinas this evening. The biggest question in central NC continues to be the northward extent of the warm sector and efficiency of CAD erosion before QLCS arrives. The severe threat looks very questionable west of Raleigh given the persistence of the CAD this morning. Rain earlier this morning, while likely eroded on the back side by a weak meso-low, has helped to keep the wedge front suppressed south of the FAY. There are some signs of clouds trying to scattered around FAY and CTZ, but there`s also quit of a bit of convection blow off from the overnight convection in southern GA, which may hinder heating even as the warm sector(s) begin to move northward. Consequently, most guidance suggest highs of 70 or below in the southeast CWA this afternoon and temps holding in the 50s in the Triad. For instability, the aforementioned surface low deepening to around 985mb over the southern Appalachians this evening and the isallobaric response will certainly help draw higher dewpoints/theta e air into the Piedmont beneath a plume of 7-8 C/KM mid-level lapse rates observed over GA this morning. However, most of the latest guidance suggests 60s dewpoints and MLCAPE over 500 J/KG will stay east of US 1, and even HRRR simulated reflectivity is unimpressive outside of an area from Richmond Co to Wilson Co. As such, current thinking is the best threat of severe (wind/tornado) is southeast of this line between 01Z and 05Z. Deep layer shear 60-80kt and 300-600 J/KG of MUCAPE may still support some intense elevated cells in the Piedmont and a hail threat. Bottom line, the severe threat is still possible but will likely be isolated in nature (we don`t expect a squall line to rip through central NC), mostly confined to the Sandhills and southern Coastal Plain. -Smith The main segment of convection will be departing after midnight, but the threat of showers and isolated storms may continue from the southwest overnight as the upper low slowly wobbles toward the area. Expect lows tonight ranging from the upper 40s in the NW Piedmont to the lower 50s elsewhere. -Vincent && .SHORT TERM /MONDAY AND MONDAY NIGHT/... As of 317 AM Sunday... Models have trended slower and farther south with the deepening upper low and attendant upper trough moving through the area Monday. Cold core aloft featuring H5 temps of -22 to -24C and mid-level lapse rates of 7 to 7.25 C/km will support instability showers in a southwest to northeast fashion throughout the day with rain expected to finally shift northeast of the area between 06 to 09z Tuesday. Highs Monday ranging from mid 50s NW to lower 60s east. Drier air filtering into the area with the departure of the system should lead to SW to NE clearing late Monday night into Tuesday morning. Lows Monday night in the lower 40s NW to mid 40s elsewhere. && .LONG TERM /TUESDAY THROUGH SUNDAY/... As of 220 PM Sunday... Tuesday and Wednesday: Any lingering cloudiness Tuesday morning will be retreating rapidly to the northeast as the coastal low lifts up the mid Atlantic coast. Unseasonably mild temperatures will stay with us through mid week with copious sunshine and increasing heights as mid level ridging migrates across the area. Highs on Tuesday will range from the upper 50s north to lower 60s south, warming on Wednesday to the mid and upper 60s. A strong shortwave lifting out of a longer wave trof into the Great Lakes region will push a cold front across the mountains Wednesday night and rapidly east across central NC and out of the area by mid afternoon Thursday. This front will be accompanied by scattered showers and begin our transition to north west flow and attendant cooler temperatures for late week and through the upcoming weekend. Temperatures on Thursday will have time to warm to the mid 50s west to lower 60s east before the cooler air arrives, and we will really notice the end of our two week mild spell Thursday night as mins fall to near freezing in the northwest to mid 30s elsewhere. Northwest flow will produce dry, but much cooler conditions Friday through Sunday, with highs in the 40s each day. Mins Friday and Saturday night will range from 25 to 30. && .AVIATION /18Z SUNDAY THROUGH Friday/... As of 100 PM Sunday... LIFR is holding strong across the Piedmont, while there have just recently been some signs of the wedge airmass beginning to erode around the FAY area, allowing ceilings to lift to IFR and MVFR. This will stay fairly steady for a few more hours - northwest wind and IFR at RDU/GSO/KINT/RWI - with some minor improvements through 00Z. After 00Z, there is a lot more uncertainty, as the northern end of a severe QLCS will cross NC from southwest to northeast. Right now it appears conditions will remain fairly stable over central NC, and the threat of storms and severe winds will be confined to FAY (maybe RWI) and southeast between 01-05Z. Any storms around around RDU/GSO/INT should remain elevated and not pose a significant wind threat. A warm front will eventually move through the area tonight and cause ceilings to lift to IFR/MVFR by Monday morning, but the primary ow pressure system responsible for tonight`s storms will cross the area cause ceilings to lower again Monday, along with scattered showers and possibly a few storms. -Smith Conditions are expected to improve /return to VFR/ sometime late Monday night or early Tuesday as the aforementioned system tracks offshore the Carolina/Mid-Atlantic coast. A cold front will cross the region by Thursday and may bring some adverse aviation weather. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Vincent NEAR TERM...Vincent/Smith SHORT TERM...CBL LONG TERM...mlm AVIATION...Smith

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