Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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805 FXUS62 KRAH 240053 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 855 PM EDT Mon Apr 23 2018 .SYNOPSIS... Strong high pressure will remain nearly stationary or slowly drift off the New England coast through tonight. Low pressure will approach from the Tennessee Valley tonight, then track slowly east over SC on Tuesday before lifting northeast across eastern NC late Tuesday and Tuesday night. && .NEAR TERM /THROUGH TONIGHT/... As of 330 PM Monday... Latest near term model guidance in good agreement depicting a stout sfc ely wind across central NC tonight, thanks to the difference in pressure between a sfc low over northern GA, and a sfc high positioned offshore of New England. This tight gradient will produce sustained sfc winds 15-20 mph with gusts around 30 mph. This east-se fetch off of the Atlantic will tap a very moist air residing offshore where satellite imagery/blended precip water product depict precip water values hovering around 2 inches. The upslope component of the low level flow coupled with lift associated an mid-upper level s/w crossing the SE U.S. will interact with the available deep moisture to produce widespread showers. Rainfall intensity expected to increase late this evening into the overnight as the upper level s/w approaches our vicinity. While current rainfall rates are averaging less than a tenth of an inch per hour, rainfall rates associated with the better dynamics may be closer to two-tenths or a quarter of an inch per hour. This will lead to rainfall amounts on the order of one-two inches by early Tuesday morning. Where the heavier rainfall rates occur in urbanized areas, minor/nuisance flooding of streets and poor drainage areas may occur. Temperatures tonight will not cool as normal due to the widespread cloudiness and breezy ely sfc winds. Min temps should vary from the lower 50s NW to the mid-upper 50s elsewhere. && .SHORT TERM /TUESDAY AND TUESDAY NIGHT/... As of 330 PM Monday... A deep upper level low over the TN Valley will drift ever so slowly east. The primary sfc low associated with this upper system will edge east-northeast across northern GA tonight, and South Carolina Tuesday morning. A warm front stretching east from this low will also drift slowly northward with time, with an expected Tuesday morning position near or south of the NC/SC border. The approach of the sfc low will likely enhance low level convergence enough to lead to the possibility of elevated isolated convection by daybreak in proximity of our southwest counties. As the morning wears on, the bulk of the shower activity will lift into southern VA. As the sfc low migrates into upstate SC/southern NC, the sfc warm lift will lift into central NC, likely bisecting the region west-to- east in vicinity of highway 64. By mid-late afternoon, the atmosphere along the south of the boundary has the potential to destabilize to permit isolated strong/severe thunderstorms to develop. The main severe weather hazard will be locally damaging wind gusts. An isolated, weak tornado cannot be ruled out es. as the sfc wave immediately to our west-sw will lead to low level backing of the sfc winds, increasing the 0-3km helicity, especially in vicinity of the sfc warm front. The threat for scattered convection and isolated strong/severe storms will diminish early Tuesday evening as the low-mid level winds just above the surface become wly with the passage of a mid level trough. High temperatures Tuesday dependent on extent of cloudiness/showers or peeks of sun. In anticipation of the sfc warm front remaining south of the VA border, will have the coolest max temps along this region, extending west into the Triad (low-mid 60s). Probabilities for temps in the low-mid 70s look good over the southeast counties. Potential for max temperature bust will lie in vicinity of the western Piedmont into the Triangle region and east towards Wilson. If showers and the warm front remain closer to the South Carolina border, max temps in vicinity of Asheboro, Raleigh and Wilson could be no higher than the low-mid 60s. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... As of 150 PM Monday... An active, energetic upper pattern featuring a long wave trof over the eastern CONUS will persist from mid week into the weekend. There is a lot of uncertainty regarding the timing and potential for phasing of a couple of short waves which will be digging into the longer wave pattern, which will ultimately determine the potential for their producing rain over central NC. A reinforcing, but dry, cold front will be pushed southeast through the area on Wednesday into Wednesday night as our initial upper low lifts northeast to be absorbed by a stronger cutoff low moving across the Great Lakes. There will be a small chance of showers across the northern tier of the area, with highs Wednesday in the low to mid 70s. Lows Wednesday night will be in the low and mid 50s. Skies will be at least partly sunny on Thursday with cooler highs in the upper 60s to lower 70s as the cold front stalls across the Gulf states. A southern stream short wave moving across the Gulf states Thursday night will spur development of a surface wave along the front, which could slide east along the front and offshore or possibly lift more northeasterly into the area and produce showers on Friday. Highs will be below normal regardless, ranging from 70 to 75, possibly cooler if we get significant shower coverage. All this while, the primary long wave upper trof has been edging east, and the trof axis will pass over the area on Saturday, possibly squeezing out a final few showers. Highs Saturday will be in the upper 60s to lower 70s. Heights finally begin to build late in the weekend as upper ridging moves into the Midwest, with strong sunshine as the associated surface high builds over the area. Highs Sunday will be in the low to mid 70s, with mid and upper 70s expected on Monday. && .AVIATION /00Z TUESDAY THROUGH SATURDAY/...
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As of 855 PM Monday... Aviation conditions will be mostly sub-VFR, primarily MVFR but dropping periodically to IFR, through sunrise Tue. Mid level low pressure will drift slowly eastward from the mid Miss Valley across TN through Tue. A corresponding surface low and frontal system will approach our area from the west, with a warm front pushing northward into NC Tue morning. Gusty low level winds from the E and SE will draw considerable deep moisture into central NC. Numerous showers will stream over the area through tonight, in NW-to-SE oriented bands, moving generally toward the NNE. Conditions are expected to drop to MVFR toward midnight at all sites, with a risk of IFR cigs late tonight. As drier air moves in from the S Tue morning, rain chances will diminish to just patchy showers from S to N through the morning. FAY may see an isolated storm or two from late morning Tue through the afternoon. Surface winds will be mainly from the E or SE, sustained at 10-15 kts with gusts to 20-25 kts. Looking beyond 00z Wed, areas of IFR cigs/vsbys are possible through Tue night at INT/GSO/RDU/RWI, with FAY staying VFR for much of the night. Conditions are expected to trend to VFR by midday Wed as the surface low shifts to our east, although a few showers are possible in the afternoon. VFR conditions will dominate into the upcoming weekend, although a chance of sub-VFR conditions in rain is possible Thu night into Fri as an upper level trough crosses the area. -GIH
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&& .RAH WATCHES/WARNINGS/ADVISORIES... NC...None. && $$ SYNOPSIS...Badgett/Hartfield NEAR TERM...WSS SHORT TERM...WSS LONG TERM...MLM AVIATION...Hartfield is the U.S. government's official web portal to all federal, state and local government web resources and services.