Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 140620 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 120 AM EST Sat Jan 14 2017 .SYNOPSIS...
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Cool high pressure will briefly build in from the northeast on today, followed by a secondary cold front on Sunday, and then another reinforcing high pressure Sunday night.
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&& .NEAR TERM /THROUGH TONIGHT/... As of 905 PM Friday... KRAX reflectivity shows surface cold front making it`s way into the southern portions of the forecast, with some notable 20 to 25 kt wind gusts at KGSB and KGWW immediately behind the fropa. The front should be exiting south of the area in the next couple of hours with cold dry air advection commencing from NE to SW as a transitory +1040 mb surface high over the the Eastern Great Lakes begins to wedge south down the Central and Southern Appalachians. Min temps are expected to range from near 40 north to mid/upper 40s south. Thus far, both low ceilings and precip has been overdone by the models. However, by 06z expect to see an increase in both cloud cover and patchy rain owing to the onset of weak 925-850 isentropic ascent, especially across far the western zones where easterly upslope will aide in lift. Rain will be very light, with only a few hundredths expected. && .SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/... AS OF 300 PM Friday... Strong arctic high centered over New England will nose southward into central NC Saturday and Saturday night. Circulation around this narrow ridge will keep our near sfc air mass rather chilly. Meanwhile 925-850mb will veer Saturday morning to a west-sw direction, initiating a cold air damming episode (classical by classification). The widespread cloudiness with the low level northeast flow will result in a small diurnal range in temperatures. Some places may only see temps recover 3-5 degrees from the morning lows. While cloud cover will be extensive, threat for rain will decrease to less than 20 percent by late morning as forcing available to generate precip absent. Rather dramatic shift in temps compared to the current spring-like conditions. Highs Saturday expected to vary from the low-mid 40s north to near 50 far south. Little change in sensible weather Saturday night as widespread cloudiness and cool conditions will persist. A weak perturbation expected to cross overhead which may trigger some patchy drizzle or light rain, mainly north of highway 64. Also, expect to see patches or areas of fog develop. Overnight temps near 40 to the lower 40s. && .LONG TERM /MONDAY THROUGH FRIDAY/... As of 300 PM Friday... The overall pattern for Sunday and Monday hasn`t changed much since the previous forecast. A 1032-1034 mb high will move from the Great Lakes through NY/PA and over the New England coast Sunday and Monday. The High will ridge southward, setting up a CAD wedge over NC. Meanwhile, an upper level low over the Baja will swing northeast into the Midwest through Monday Night. There is still a question of if/when the wedge will erode early Sunday morning and re-establish itself late Sunday, or whether it will hold all the way through Tuesday night. The west-northwest flow aloft on Sunday would normally result in some subsidence and drying, however there is enough moisture in the mid-upper levels that weak disturbances may generate some light rain/drizzle into the wedge airmass, thus reinforcing it. Regardless, expect overcast skies Sunday onward, which despite any clearing in the boundary layer, will help limit temperatures. Given the uncertainty, confidence is not terribly high, but current forecast highs range from upper 40s NE to around 60 degrees SW. Chances for light rain/drizzle will linger over the west through Sunday night with lows in the low 40s. Cooler but dry weather expected in the NE Sunday night. The wedge will remain in place on Monday and may slowly start to erode on Tuesday as the surface flow becomes more southerly between the high over the Atlantic and the approaching front to the west of the Appalachians. Also expect moderating temps Tuesday through Friday. The strong southerly flow ahead of the front will result in good moisture feed off the Gulf and thus high chances for rain ahead of the front. However, the medium range models are significantly different with respect to the strength/character of the low/trough as it approaches, as well as the timing of the pre-frontal rain and subsequent cold frontal passage. Will lean more toward the slower ECMWF solution which currently brings the rain in on Wednesday through Wednesday night. Uncertainty is still high at this time and thus confidence is low, however do expect a good chance of rain and possibly thunder ahead of the front, regardless of when it progresses through Central NC. && .AVIATION /06Z FRIDAY THROUGH WEDNESDAY/...
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AS OF 120 AM Saturday... An 8-12kt northeast wind has developed in the wake of a cold front that has pushed south of the NC/SC as of 06Z. MVFR cigs have been slow to develop but have started to expands from RDU to GSO/INT and northward, as an area of rain also expands near the NC/VA border. MVFR cigs should continue to develop southward overnight as the low- level flow turns to southerly and strengthens. The aforementioned rain may aid in lowering ceilings at GSO and INT this morning, possibly to IFR, but confidence is relatively low. Otherwise, MVFR cigs may not move very much today without more widespread precip, and the low clouds may even mix out at FAY where the moisture and lift are not as pronounced. Outlook: Cold air damming and associated widespread MVFR to diurnally IFR conditions will persist Sunday through most of Tuesday. Warm air scours out the colder air Tuesday with a return to VFR conditions briefly as a cold front and its associated adverse conditions approaches on Wednesday.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...SMITH NEAR TERM...CBL SHORT TERM...WSS LONG TERM...KCP AVIATION...mlm/SMITH

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