Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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527 FXUS62 KRAH 221821 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 220 PM EDT Sun Oct 22 2017 .SYNOPSIS... High pressure will extend across the eastern United States through tonight. Meanwhile, a strong frontal system will approach from the west and cross the Appalachians and Carolinas late Mon through early Tue. && .NEAR TERM /THROUGH TONIGHT/... As of 1040 AM Sunday... Little adjustment required to the near term forecast. Mid/upper level ridge has moved offshore while the sfc ridge axis remains across our area. Narrow band of fog/low clouds across portions of the western-southern Piedmont will disperse by mid day. Expect mostly sunny skies through most of the afternoon, with a notable increase in high level cloudiness, especially across the Piedmont. Temperatures on track to reach well into the 70s across the north, and near 80-lower 80s across the south. These temperatures are a solid 7-10 degrees above normal. Clouds will continue to increase and thicken tonight as a s/w deepens and becomes a closed low over the western TN Valley by early Monday. Strengthening isentropic upglide ahead of this system may generate a shower or two late tonight in vicinity of the Yadkin/Pee Dee River Valley. Southerly flow and thickening cloud cover will yield overnight temperatures mainly in the 55-60 degree range. && .SHORT TERM /MONDAY AND MONDAY NIGHT/... As of 330 AM Sunday... A vigorous cutoff shortwave will lift northeast up the Appalachians into the mid Atlantic as it is reabsorbed into a longwave trof digging southeast across the Great Lakes. Low level flow will be increasing and providing a strong moisture feed into the southern mountains early Monday, with low level jetting increasing to exceed 50 knots as the flow veers increasingly southerly and begins marching east ahead of an associated surface cold front. While instability will be limited by cloudiness and numerous prefrontal showers, low level convergence in the frontal zone will be very strong and a line of vigorous convection is expected in the west during the afternoon, which will move east to reach the Coastal Plain after midnight Monday night. The strong low level flow could be translated to the surface by convective activity, so damaging winds will be possible, especially in the convective line accompanying the front. In addition, the low level shear profile would support rotation in stronger storms, so isolated tornadoes cannot be ruled out. Highs Monday will be mild despite cloudiness and shower activity due to strong warm air advection, reaching mostly mid and upper 70s with some lower 70s in the far western Piedmont. Mixing and warm southerly flow overnight will maintain mild mins in the mid 50s northwest to lower 60s east. && .LONG TERM /TUESDAY THROUGH SUNDAY/...
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As of 220 PM Sunday... Low level jetting and the associated deep moisture plume will be moving east of the Coastal Plain early Tuesday morning, with drier and cooler air beginning to filter in as the moisture tap cuts off. Cloudiness will be diminishing, with stratocumulus lingering primarily across the northern tier associated with the H85 trof which will be moving across during the afternoon/evening. Cold air advection will be delayed until the surface front exits the area towards sunset, allowing highs to reach mostly lower 70s, with some upper 60s in the northwest. The cool air settles in Tuesday night and Wednesday, with mins mostly in the mid 40s Wednesday morning warming to mostly low and mid 60s in the afternoon. The main long wave trof axis will cross the area Wednesday night as it rotates across the Great Lakes into New England. The ensuing northwest flow will reinforce the cool air and perhaps produce some scattered very light showers in the lee of the mountains, but it will be short-lived as the progressive pattern rapidly transitions to a short wave ridge and rising heights in the late week. Lows Thursday morning will be our coolest of the period, falling to the upper 30s to lower 40s, with highs Thursday topping out 5-7 degrees below normal in the 60 to 65 range. The short-lived ridging shifts offshore and ensuing southerly return flow induces a modest warming trend into the weekend, with highs from 65 to 70 on Friday, and upper 60s to lower 70s on Saturday. Our next front will be approaching from the west, perhaps as early as Saturday night, with associated showers and a cool down into the 60s likely on Sunday.
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&& .AVIATION /18Z SUNDAY THROUGH FRIDAY/...
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As of 220 PM Sunday... There is a high probability that VFR conditions will persist across central NC through 03Z Monday. After 03Z, a strengthening sely flow a few thousand feet above the surface will advect moisture into central NC. This moisture feed will be centered mostly over the western-southern Piedmont and less so over the northern coastal plain. This will result in a deck of stratocu with ceilings as low as 1000-1500 ft. These ceilings will likely persist well into Monday in vicinity of the Triad terminals. In vicinity of KFAY and KRDU, ceilings will likely bounce between MVFR and low end VFR until late Monday when MVFR ceilings should persist. Scattered showers will pass in vicinity of the Triad terminals as early as Monday morning. Shower coverage in vicinity of the triad will increase Monday afternoon with numerous showers anticipated by Monday evening. This band of showers will inch eastward, and affect operations in vicinity of KRDU and KFAY by 02z through 07Z, and in vicinity of KRWI between 04Z through 10Z. Parameters for thunder are weak though a t-storm could occur in vicinity of KFAY between 00Z-06Z. Sfc winds will be gusty late Monday through Monday night with southerly winds gusting 20-30 mph. The showers will exit our eastern counties shortly after daybreak tuesday as a cold front sweeps east across the region. Ceilings will begin to lift in the western Piedmont including the Triad terminal after 06Z, and across the remainder of central NC between 10Z and 14Z. VFR parameters are anticipated areawide Tuesday afternoon through Friday. The exception will be a brief instance of MVFR ceilings Wednesday as an upper level trough passes overhead.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...MWS NEAR TERM...WSS SHORT TERM...mlm LONG TERM...mlm AVIATION...WSS

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