Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 132001 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 300 PM EST Fri Jan 13 2017 .SYNOPSIS...
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A cold front will push south through the area tonight. Cool high pressure will briefly build in from the northeast on Saturday, followed by a secondary cold front on Sunday, and then another reinforcing high pressure Sunday night.
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&& .NEAR TERM /THROUGH TONIGHT/...
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As of 300 PM Friday... Another spring-like afternoon across central NC with temperatures once again well above normal, in some places as much as 25 degrees above normal, for mid-January. Some places are approaching near record warmth. Mid afternoon temperatures varied from near 70 across the far north-northeast to the mid-upper 70s across the south. A strong cold front has entered the northern coastal plain, evident by the northeast sfc winds observed at the Halifax County airport at 19Z. This boundary will gradually edge south-southwest for the rest of the afternoon into the evening hours, exiting our far southern counties around midnight. Low level ne flow behind the front will usher in a notably colder air mass. This cold surge will be felt first in the northern coastal plain, including the KRWI vicinity, by sunset; and into the Triangle and Triad areas this evening. As the 925-850mb flow becomes more ely later tonight, this upslope component will aid to generate patches of light rain in vicinity of the Yadkin River Valley including our far western-nw counties. Any rain that occurs over our western Piedmont will be spotty and very light. The rain chances appear to be best during the overnight hours. Not expecting much, if any, light rain east of highway 1. The low level cold air advection will persist overnight into Saturday morning. Most places will see their early morning lows after daybreak Saturday, especially across the southwest third of the forecast area. Min temps upper 30s/near 40 north to the low-mid 40s south.
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&& .SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/...
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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.
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&& .LONG TERM /MONDAY THROUGH FRIDAY/...
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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.
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&& .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/... AS OF 1235 PM Friday... VFR conditions across central NC will gradually deteriorate northeast to southwest this afternoon and this evening as a strong cold front drops southward. Low level northeast flow will usher in a moist air mass, resulting in the formation of a stratus layer and associated MVFR/IFR ceilings. These adverse ceilings should be areawide by 03Z. An intrusion of drier air in the 1000-2500 ft layer may allow ceilings to lift temporarily into the VFR category at KRWI and possibly KRDU during the overnight hours before ceilings lower back to the IFR/MVFR categories by daybreak Saturday. Pockets of very light rain should develop over sections of the Piedmont this evening and persist into the overnight hours. This probability appears greatest in vicinity of the Triad terminals, and less so toward KFAY. In addition, a stout ne sfc wind will occasionally gusts between 18-23kts tonight. The patchy light rain will gradually diminish Saturday morning though widespread IFR/MVFR ceilings will linger Saturday and Saturday night. An unsettled aviation weather period is expected Sunday through Wednesday as abundant moisture in the lower half of the atmosphere and a series of perturbation aloft will maintain extensive cloudiness and instances of light rain. This suggest prolonged periods of MVFR/IFR ceilings are likely Sunday through Wednesday. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...SMITH NEAR TERM...WSS SHORT TERM...WSS LONG TERM...KCP AVIATION...WSS

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