Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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929 FXUS62 KRAH 221440 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 1040 AM 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/...
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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.
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&& .SHORT TERM /MONDAY AND MONDAY NIGHT/...
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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.
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&& .LONG TERM /TUESDAY THROUGH SATURDAY/...
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As of 233 AM Sunday... Low level jetting will be moving east of the Coastal Plain early on Tuesday morning, with drier and cooler air beginning to filter in as the moisture tap is cut off. Cloudiness will be diminishing, but low level cold air advection will be delayed until later in the day as the lagging surface front crosses the area. Highs will have time to reach mostly low 70s with some upper 60s in the northwest where cold air advection will begin earlier and there will be additional potential for stratocumulus accompanying the cool surge. With the cool air settling into place, mins Tuesday night will fall to the mid and upper 40s. An additional reinforcing surge of cool air is expected Wednesday as strong shortwave energy digs into the Midwest trof, shifting it across the Ohio Valley, with the axis moving across the south Atlantic coast Wednesday night. Highs Wednesday and Thursday will be mostly in the low and mid 60s, with morning mins Thursday morning in the upper 30s to lower 40s. Shortwave ridging and return flow as associated surface high pressure moves offshore will give us a warmup late in the week, with highs Friday and Saturday mostly in the mid 60s to lower 70s.
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&& .AVIATION /15Z SUNDAY THROUGH THURSDAY/...
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As of 1040 AM Sunday... Under the continued influence of high pressure along the middle Atlantic coast, generally VFR conditions are expected to persist for most of the forecast period, with one exception. Increasingly moist east to sely low level flow off the Atlantic ocean will favor the development of IFR-MVFR ceilings mainly at wrn TAF sites (INT/GSO), and perhaps some visibility restrictions in fog at ern TAF sites where radiational cooling potential will linger, late tonight-early Mon. Outlook: An approaching frontal system will then result in the ewd progression of a band of IFR-MVFR ceilings, showers and isolated storms (some possibly severe), and strong/veering winds with height late Mon and Mon night.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...MWS NEAR TERM...WSS SHORT TERM...mlm LONG TERM...mlm AVIATION...MWS

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