Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 241124 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 623 AM EST Tue Jan 24 2017 .SYNOPSIS... Mild high pressure will build into the area in the wake of the deep low pressure system lift northeast up the northern Mid Atlantic coast. A cold front will push east across Central NC on Thursday. && .NEAR TERM /THROUGH TONIGHT/... As of 305 AM Tuesday... In the wake of deep low pressure system lifting up the Mid-Atlantic Coast, shortwave ridging extending from the GOM northward into the Middle MS Valley will shift east over the area. Resultant strong subsidence will lead to rapid clearing this morning with breezy conditions developing in response to the tight gradient between the low to our northeast and the ridging building from the west. Expect sustain winds of 12 to 15 kts, gusting to 25 to 28 kts through the afternoon. Winds will decouple this evening as surface ridge builds briefly over the area overnight. Low-level thicknesses support highs ranging from upper 50s north to lower 60s south. Good radiational conditions tonight will support lows in the mid 30s north/northwest to lower 40s elsewhere. && .SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/... As of 305 AM Tuesday... Ridging over the area to start the day on Wednesday will shift east and offshore during the later half of the afternoon, in advance of a lead positively tilted shortwave trough ejecting eastward through the Central Plain and MS Valley, with attendant cold front progged to reach the central and southern Appalachians around midnight Wednesday night. Temperatures ahead of the front on Wednesday will warm well into the 60s across all of Central NC, and will flirt with 70 across the southern half. Additionally, with the approach of the front, we will also see some breezy swly winds materialize by the late afternoon, but certainly by the evening, gusting into the upper teens. A 50 to 60kt LLJ racing out ahead of the system and underneath the entrance region of a 125-135kt jet streak moving into the Mid- Atlantic region will lead to rapid 1000-700mb moistening Wednesday evening/night, and bringing a quick moving band of low topped showers into the area after midnight. Due to fast-progressive nature of the system, qpf amounts will be light, generally a tenth of an or less. Lows Wednesday night ranging from mid to upper 40s NW to lower/mid 50 east. && .LONG TERM /THURSDAY THROUGH MONDAY/... As of 400 AM Tuesday... Thursday: Light rain associated with low-mid level frontogenesis along and behind a cold front progressing across central NC is expected to end from west-east Thursday morning as the front tracks east of central NC/offshore and the parent shortwave/sfc cyclone lift NE through New England toward the Canadian Maritimes. A rapid clearing trend is expected in the wake of the front in assoc/w strong low-level cold advection. Forecast soundings show low-level lapse rates rapidly steepening (becoming dry adiabatic from the SFC- H85) as CAA coincides with peak heating Thu afternoon, a favorable setup for strong W/WNW winds. 00Z GFS/NAM/ECMWF guidance differ with regard to the precise evolution of the parent cyclone in New England during the day Thu. The GFS solution indicates a stronger cyclone and tighter mslp/height gradient over the Mid-Atlantic/Carolinas than the NAM, while the ECMWF is somewhere in-between. Although the difference in the synoptic pattern is relatively subtle, the difference is sufficient enough that westerly flow within the mixed layer is ~10 knots stronger on the GFS in comparison to the NAM. At A blend between the GFS/NAM suggests that W/WNW winds will become sustained at 15-25 mph with frequent gusts to 30-35 mph during the strongest pressure rises (6-8mb/6-hr between 18-00Z) Thursday afternoon. Additionally, although less likely at this time, 40+ mph convective gusts could accompany shower activity in vicinity of the front along/east of I-95 late Thu morning or early Thu afternoon. Expect highs in the mid/upper 50s to near 60F (warmest near SC border). Lows Thu night in the lower to mid 30s. Fri-Sun: Long range guidance continues to indicate dry conditions, below normal temperatures and a brisk W/WNW breeze during the afternoon hours Fri-Sun. Sunday Night-Monday: The latest 00Z guidance suggests that Canadian shortwave energy digging southward through the Upper Great Lakes and western Ohio Valley on Sunday may dig further south/west than in previous runs. As a result, light precipitation (and ptype issues) may accompany the deeper /more amplified/ upper level wave progged to track across the region Sunday night/Monday. -Vincent && .AVIATION /12Z TUESDAY THROUGH SATURDAY/...
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As of 623 AM Tuesday... 24-Hour TAF period: Deep low pressure will move northeast, away from Central NC through the day. Low-level dry air will continue to filter into the area from west, with the lingering MVFR ceilings across eastern NC expected to improve/lift to VFR at or shortly after 12z. Breezy NWLY winds will develop everywhere by mid to late morning with sustained winds of 14 to 17kts, gusting to 25 to 30kt through the afternoon. Winds should decouple by the evening as surface ridge axis extends into the area from the south. Looking ahead: VFR conditions are expected through Wednesday. A cold front will cross the region late Wednesday night/early Thursday, bringing with a chance of showers and sub-VFR ceilings to the area. VFR conditions should return late Thursday afternoon/evening.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...CBL NEAR TERM...CBL SHORT TERM...CBL LONG TERM...Vincent AVIATION...CBL/SMITH

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