Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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528 FXUS62 KRAH 271146 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 646 AM EST Mon Feb 27 2017 .SYNOPSIS... High pressure will move offshore today, followed by a warm front lifting through the area tonight. Meanwhile, warm southwesterly flow will continue ahead of a cold front approaching from the west through midweek. && .NEAR TERM /THROUGH TONIGHT/... As of 340 AM Monday... A 1028mb surface high is centered off the Delmarva this morning and will continue to shift east today, resulting in a light southerly flow that will increase 1000-850mb thickness by about 25m over Sunday. Thin high clouds will spread in from the southwest ahead of a shearing shortwave currently over MO/AR, but thicker mid clouds should hold off until this evening and the impacts on highs look negligible. The 25m increase in thicknesses supports guidance consensus of lower 60s northwest to 70 southeast. The aforementioned sheared shortwave will cross the region tonight, leading to increased cloud cover, initially mid/high level and then later in the form of stratus associated a warm front and strengthening warm advection. Most models continue to be essentially dry overnight, as upstream precip should dissipated with eastward extent this evening. However, the NAM still indicates some light showers breaking out with the warm front after midnight, due at least in part to some questionable elevated instability, and the 00Z ECMWF supports at least a slight chance POP after midnight. Mid and high clouds look like they`ll move east by midnight and may yield a period of brief clearing before stratus develops across the west. This should allow temps to fall into the mid 40s west to lower 50s east. && .SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/...
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As of 340 AM Monday... West-southwest flow will ensue on Tuesday as a surface warm front lifts north of the area. Morning stratus will likely hold longest across the west but full heating is expected for a large portion of the area as period of high clouds spread east in relatively low amplitude flow. 1000-850mb thicknesses support highs in the lower 70s west to near 80 east. Dewpoints creeping into the upper 50s and modest 6.5-7 C/KM mid level lapse rates will lead to weak instability, but forcing is largely lacking outside of warm advection. Currently think showers and a few storms will be widely scattered across the Piedmont and coastal plain. Tuesday will be rather mild in the warm sector of a stronger low pressure system moving through the Midwest, with lows in the upper 50s and lower 60s.
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&& .LONG TERM /WEDNESDAY THROUGH SUNDAY/... As of 400 AM Monday... Wed-Wed night: A complex mid-upper level trough compromised of multiple embedded shortwave perturbations will move E from the Plains states early Wed to the Northeast by Thu morning. At the same time and at the surface, related waves of low pressure will migrate from the mid MS Valley to New England, while the trailing cold front will move from the Appalachians late Wed-Wed evening to the Atlantic coast by Thu morning. It will be warm and windy, but dry for most of the day Wed, owing to a stout capping inversion. Strong SWly flow in the warm sector will yield sustained 15-20 kt winds, with gusts up to 30-35 kts during the afternoon. Morning stratus, trapped beneath the aforementioned inversion, will disperse by midday or early afternoon, so temperatures should consequently rise rapidly into the upper 70s to lower 80s. Pre-frontal showers and storms will be possible over the far wrn Piedmont, as mid level height falls related to the approaching trough aloft move overhead and fully lift and erode the preceding capping inversion there by sunset. The better chance of showers and storms will occur Wed evening and Wed night, as the surface front sweeps Ewd. Strong SWly deep layer flow, oriented mainly parallel to the frontal zone, will favor linear convection that would pose primarily a damaging wind threat given a relative lack of more robust low level moistening, and associated instability. Blustery post- frontal NWly winds will follow in strong CAA late Wed night- early Thu, with lows in the low- mid 40s west to middle 50s east. Thu-Sun: A following clipper shortwave trough in NW flow aloft will amplify across the Middle Atlantic states Thu night-Fri, with an associated re-enforcing, but dry, cold frontal passage on Fri. Temperatures will nadir in the middle 20s to around 30 degrees Sat morning, but a moderating trend will follow as the flow aloft becomes more zonal by the weekend. && .AVIATION /12Z MONDAY THROUGH FRIDAY/...
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As of 645 AM Monday... High confidence in VFR today under influence of high pressure. A light south-southwest wind will develop today as the high moves east. Mid and high level clouds will increase this evening as a weakening upper level disturbance moves overhead and a warm front lifts north into the Carolinas. More substantial MVFR stratus, will likely come after 06Z and be most prevalent at GSO and INT, with a low end chance of a few showers as the warm front lift through through central NC. Some IFR stratus is possible, though the lowest ceilings should remain west of INT. Outlook: Stratus developing early Tuesday will burn off prior to midday, with scattered showers and storms possible during the afternoon and evening. A more substantial threat of sub-VFR is expected late Wednesday and early Thursday a cold front crosses the region. VFR will then return for the end of the week.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...SMITH NEAR TERM...SMITH SHORT TERM...SMITH LONG TERM...MWS AVIATION...SMITH

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