Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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519 FXUS62 KRAH 180255 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 955 PM EST Tue Jan 17 2017 .SYNOPSIS... A cold front will track southeast through central North Carolina late tonight through mid day Wednesday. In the wake of the front, high pressure will build into the region from the northwest Wednesday night and Thursday. && .NEAR TERM /THROUGH TONIGHT/... As of 955 PM Tuesday... Earlier shower activity was the result of weak shortwave disturbances tracking through the area, within the moist ~1.2" PWAT airmass extending from the western gulf northeast into the Carolinas. In the wake of these disturbances, central NC will see a lull in precip until the arrival of the cold front into the Triad between 09 to 12z, exiting southeastern counties between 15 to 18z. Even then precip amounts will remain light, owning to the lack of accompanying upper level support. Given the late arrival of the front into the area, broken to overcast cloud cover and swly winds will result in mild overnight lows in the mid to upper 50s. && .SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/... As of 115 PM Tuesday... Expect some chance for showers along the cold front progressing into central NC Wed morning given a modest plume of SFC-925 mb moisture in the presence of low-level convergence within the low-level trough. In the immediate wake of the front late Wed morning through early Wed afternoon, strong DPVA progged to track ESE through VA into northeast NC may encounter lingering low-level moisture across central/eastern NC. As a result, a period of anafrontal precipitation will be possible in central NC, primarily from the Triangle east into the Coastal Plain. Expect a clearing trend mid/late afternoon in assoc/w subsidence in the wake of the shortwave and the onset of low-level cold advection in the wake of the front. Given the timing of the front and the potential for precipitation /evap cooling/ late Wed morning through early Wed afternoon, high temps on Wed will vary little from overnight lows except perhaps in the far S/SE where temps may reach the mid 60s prior to cold advection post-fropa. Lows Wed night will be driven by a combination of cold advection and radiational cooling, ranging from near 40F at the VA border to the mid 40s SC border. -Vincent && .LONG TERM /THURSDAY THROUGH TUESDAY/... As of 244 PM Tuesday... There is fairly good model agreement through this period. The general pattern is a series of weather systems swinging through the region, resulting in alternating wet and dry periods. Thursday through Friday Night: Thursday will be largely dry with a surface high briefly moving over and away from the area and an upper level ridge over the Southeast U.S. Meanwhile, an upper low that developed over the Southwest U.S. will lift northeast and get absorbed into the northern stream. This low will then transition into a shortwave trough extending southeast into the Carolinas from the Plains. A warm front will lift northward through Central NC Thursday night into Friday. Strong southerly flow advecting warm moist air into the region, combined with the upper forcing from the s/w aloft, will result in a period of rain moving through the area Friday aft/eve and clearing out Friday night. Highs will increase slightly from Thursday (mid to upper 50s) to Friday (mid 50s north to mid 60s south), but lows will be mainly in the mid to upper 40s. Saturday through Monday: Saturday should be dry with highs in the low to mid 60s with continued advection of warm air into the region. The weather gets increasingly more interesting for the rest of the weekend and model agreement remains above normal, especially for this far out in the forecast period. A strong low pressure system moves off the Rockies Saturday night and quickly moves east through the ARKLATEX on Sunday. With continued advection of warm moist air off the Gulf ahead of the low, PWATs and precip chances will increase Saturday night. The trough will become increasingly negatively tilted Sunday night into Monday as the upper low swings toward and along the Appalachians. This system will bring our first chance for potentially strong storms to move through the area, though for now will indicated the chance for some isolated thunderstorms until it gets closer in time we get a better handle on the instability, shear, and lapse rates that will largely determine what type and strength of convection we can expect. Temps will increase Sunday through Monday, especially across the southeast, before decreasing again Monday night on. The weather should dry out on Tuesday, though the negatively tilted trough will remain over the Mid-Atlantic as the low lifts northward through NY into Canada. Highs in the mid 50s and lows in the upper 30s to mid 40s expected. && .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/... As of 740 PM Tuesday... 24 Hour TAF period: Isolated to scattered showers (with possibly MVFR visbys with the showers) will be possible this evening into Wednesday morning ahead of an approaching cold front that is expected to move through the area near daybreak Wednesday through around 15/16Z or so (in a NW to SE fashion). We may see some sub-VFR cigs develop after midnight in advance of the front, along with the potential for a few showers, though confidence in the coverage and how low cigs will be is much in question. For now will go with low- end MVFR cigs developing at all TAF sites in the 07-09Z time range, then continuing until fropa (low confidence though). Winds will switch around from southwesterly to northwesterly behind the front on Wednesday, with possibly some gust into the 18 to 25 mph range. Outlook: Expect a clearing trend in the wake of the front with a brief return to VFR conditions Wed night/Thu. A pattern similar to the one affecting the region today is progged to develop over the region again late this week. With this in mind, expect ceilings to begin deteriorating Thu night/Friday, with unsettled weather expected into the weekend. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Vincent NEAR TERM...CBL SHORT TERM...Vincent LONG TERM...KC AVIATION...BSD/Vincent

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