Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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642 FXUS62 KRAH 262355 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 750 PM EDT WED OCT 26 2016 .SYNOPSIS... Cool high pressure will extend into our region from the north through tonight, before shifting offshore early Thursday. A cold front will move into the area from the northwest Thursday night. && .NEAR TERM /through tonight/... As of 230 PM Wednesday... Quiet weather and generally clear skies for the rest of the afternoon will give way to increasing clouds overnight, as the surface ridge axis extending into the area from the north shifts east and offshore, resulting in a low level return flow and inducing strengthening and deepening moist isentropic upglide focused at 285- 295K, within a surface-based stable layer extending up to around 940 mb. This should lead to development of stratus late tonight as the upglide ramps up. We`ll also see increasing mid and high clouds based around 18kft to 25kft, ahead of the weakening positively tilted mid level shortwave trough, spreading in from the west soon after midnight, and this in part may help limit fog development, and as such, stratus is favored as 925-850 mb flow increases late from the southwest. All of this will translate to clear skies this evening, trending to mostly cloudy or cloudy overnight. Expect lows to be much milder than last night, in the mid-upper 40s. -GIH && .SHORT TERM /Thursday through Friday night/... As of 250 PM Wednesday... We`re firmly in the warm sector for the entirety of Thu, although the chance for any significant precip late Thu into Thu night remains on the low side. Vorticity within the incoming weakening mid level shortwave trough continues to shear out as the trough axis swings through the area Thu, just ahead of the weak surface front being driven by potent surface and mid level low pressure crossing the Great Lakes and Northeast. Forecast soundings indicate a dry and fairly stable column between 850 and 700 mb, coupled with borderline surface dewpoints low to rise into the 50s until late in the day. By the time the lower levels moisten up, the mid levels (500-700 mb) begin to warm and stabilize/dry out Thu night as the weak trough axis shifts to our east. This all serves to limit deep destabilization that would support convection ahead of or with the front. Other forcing mechanisms also grow weaker with each model run, it seems, with upper divergence a non-issue at our latitude based on weak upper winds, and an 850 mb southwesterly jet that is focused well to our northwest and north. Ensemble model output shows unimpressive precip chances, with the SREF probabilities of measurable rain quite low, even in our far northern section, while the GEFS members almost uniformly indicate just a few hundredths of an inch of precip through the event. Will trim pops by a few percentage points, keeping chances in the far north and northeast with no better than a slight chance of showers along and south of Highway 64 through central NC, focused on very late Thu afternoon into Thu evening. The trough axis hangs back just enough to keep a few clouds in central and eastern sections later Thu night, but these should clear out for Fri, yielding mostly sunny/clear skies Fri/Fri night as broad mid level ridging extending from west of Baja California NE through the lower Miss Valley builds toward the Carolinas. Models don`t show much of a dropoff in thicknesses heading into Fri, mainly because the surface front will be undergoing frontolysis by that point as it dips into northern NC Fri morning before washing out completely. Expect highs of 72-77 Thu and 69-76 Fri. Warm lows in the 50s Thu night and in the upper 40s to lower 50s Fri night. -GIH && .LONG TERM /Saturday through Wednesday/... As of 256 PM Wednesday... Primary storm track will follow the main belt of westerlies that will shift northward along the US/Canada border as upper level ridge over the Central Plains expands eastward into the Southeast US. This will favor a continuation of dry conditions with temperatures well-above normal, averaging a good 7 to 12 degrees above normal through next week, potentially peaking Sunday with some lower to mid 80s possible in advance of a dry and weak back-door cold front late Sunday night. && .AVIATION /00Z Thursday through Monday/... As of 750 PM Wednesday... VFR conditions continue this evening and confidence is high in VFR conditions through 06Z. After that, increasing southerly flow above the surface will moisten the low-levels and increase the chance of sub-VFR ceilings by 12z. Forecast soundings suggest any stratus will be IFR or LIFR, but the degree of moistening isn`t overwhelming, so confidence in widespread stratus remains low. The chance of fog may also exist at RWI and FAY where surface winds will be very light and the thin cirrus drifting overhead will have less impact. Increasing low-level moisture may also result in some brief MVFR ceilings between 12z and 15z, with generally VFR expected for Thursday afternoon and west-southwest wind gusts of 15-20t Outlook: A few showers are possible Thursday evening and early Friday night on the southern end of a low-pressure system moving through the Ohio Valley, though any sub-VFR conditions would likely be brief. A cold front will slip south into the area on Friday, with high pressure then dominating through the weekend. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Hartfield NEAR TERM...Hartfield SHORT TERM...Hartfield LONG TERM...cbl AVIATION...BS is the U.S. government's official web portal to all federal, state and local government web resources and services.