Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 091822 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 120 PM EST Fri Dec 9 2016 .SYNOPSIS... Arctic high pressure will build across the area through Saturday. A cold front will approach from the west late Sunday and move through the area on Monday. && .NEAR TERM /THROUGH TONIGHT/... As of 950 AM Friday... Forecast is in good shape. A large area of arctic high pressure continues to build in from the NW today, with fast mid level flow from the WNW and a dry column. A weak wave passing by to our north is responsible for the sporadic snow showers on the western slopes, but neither these nor the associated cloud cover will survive crossing the mountains. The observed thickness at GSO this morning was 1278 m, well below the seasonal normal, and steady cold air advection today will not afford much of a rise, even with ample sunshine. Temps so far this morning are running a degree or so above the forecast pace, so have nudged up temps accordingly this afternoon by a degree or so, peaking at 40-46. -GIH The expansive arctic high pressure currently centered over nation`s mid-section will build slowly eastward into the area through the weekend. Aloft, trailing channeled shortwave energy, associated with the closed low moving out over the Canadian Maritimes will traverse the Mid-Atlantic region today. However, it will prove of little consequence as the cP airmass in place(PWATS ~ 0.10") is just too dry to support any clouds. With H8 temps -10 Celsius(2 to 3 standard deviations below normal) and low-level thicknesses bottoming around 1275 meters(45 meters below normal), temperatures will will run a good 10 to 15 degrees below normal. Highs in the upper 30s to lower 40s. Lows in upper teens to lower 20s. && .SHORT TERM /SATURDAY AND SATURDAY NIGHT/... As of 200 AM Friday... Flow aloft transitions to zonal on Saturday. Otherwise, very little little change as the modified arctic high pressure migrates east atop the region. Temperatures Saturday and Saturday night will be very similar to today and tonight. Highs 40 to 45. Lows 20 to 25. && .LONG TERM /SUNDAY THROUGH THURSDAY/... As of 400 AM Friday... Overview: Long range model guidance has come into better agreement on Sunday/Monday, however, considerable uncertainty plagues the remainder of the extended forecast. Sun/Mon: A shortwave trough and attendant low pressure system expected to move onshore the Pacific NW on Saturday is progged to track rapidly east across the Upper Midwest (Sun), Great Lakes (Sun night), and New England (Mon) via a 125-150 knot upper level jet extending from coast-to-coast at ~40 degrees latitude. An associated cold front will rapidly approach the mountains from the west Sunday night, however, the front will slow down as it tracks SE through the Carolinas on Monday and will likely stall in a west-east orientation over the Deep South/Southeast Tuesday morning. With the above in mind, expect increasing cloud cover and highs in the 40s on Sunday (coolest NW/warmest SE), with light rain assoc/w southerly return flow /warm advection/ possible Sunday evening/night, primarily in the SE coastal plain. Chances for precipitation will increase on Monday as the front progresses into the Carolinas. Temperatures on Monday will be a function of strong warm advection, cloud cover, and precipitation, resulting in low confidence. At this time will indicate highs ranging from the mid 50s NW to mid/upper 60s SE. Mon Night-Thu: Considerable uncertainty persists from Monday night onward as the aforementioned front stalls in a west-east orientation across the Deep South/Southeast, beneath an energetic upper level pattern characterized by numerous small amplitude waves embedded within a ~150 knot jet that extends from the Pacific to the Atlantic. With confidence so low, will make little change to this period of the forecast. -Vincent && .AVIATION /18Z Friday through Wednesday/...
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As of 120 PM FRIDAY... High confidence in chilly but tranquil aviation conditions for the next 24 hours. Skies will be virtually cloud-free with unrestricted vsbys for the rest of today through tonight and into Saturday as high pressure builds in from the NW. Only a few high clouds tonight are expected as a weak mid level wave passes by within a fast flow aloft. Looking beyond 18z Saturday, VFR conditions should hold through the first half of Sunday as high pressure builds overhead. As a warm front approaches from the south, moisture will increase, and cigs will trend to MVFR then IFR Sunday afternoon from south to north. Adverse aviation conditions, including sub-VFR cigs and vsbys, are expected to dominate from late Sunday through at least Monday night -- and perhaps into Wednesday -- as waves of low pressure track along the frontal zone as it holds over or just south of the area. - GIH
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&& .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...CBL NEAR TERM...Hartfield/CBL SHORT TERM...CBL LONG TERM...Vincent AVIATION...Hartfield

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