Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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249 FXUS62 KRAH 241830 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 230 PM EDT Mon Jul 24 2017 .SYNOPSIS... A surface trough will extend from central Virginia southwest into central North Carolin through tonight. A cold front will drop south into the region late tonight and on Tuesday. The front will stall across the Carolinas on Wednesday. && .NEAR TERM /THROUGH TONIGHT/... As of 1050 AM Monday... The latest surface analysis shows a surface trough extending southwest from near KDCA through central Virginia into the Piedmont of NC. A cold front extends from east to west across the Mid Atlantic to the OH river valley. Further aloft, a moderate amplitude trough extends south from the eastern Great Lakes into the Carolinas with the two short wave troughs embedded within with one at the coast and the second moving east of the NC/VA mountains. The air mass across central NC is beginning to dry out from the northwest with morning precipitable water values ranging from 1.5" near KGSO to around 2.0" near KFAY. The air mass has also cooled down with the 1000-850 MB thickness values about 20m lower than yesterday day at this time at KGSO and KRNK with less cooling, around 10m at KMHX. A band of scattered showers and enhanced cloudiness moving across the northern Coastal Plain is associated with a convergence axis that is fairly well defined at 925 and 850 hPa. This convergence axis washes out this afternoon with a more general westerly flow developing. Additional scattered convection is expected to develop this afternoon ahead of the eastward advancing short wave trough. The atmosphere today is less unstable than previous days with afternoon MLCAPE values likely to peak in the 500-1500 J/Kg range. Bulk shear values should range between 15 and 20 kts. The result should be a decrease in storm coverage this afternoon compared to previous days with the greatest chances across the eastern Piedmont and especially the Coastal Plain and Sandhills. Storm coverage will be greatest during the afternoon and evening with only an isolated threat of a shower or thunderstorm overnight, again mainly across the Southeast. Temperatures today will be modulated by the cloud cover. Widespread stratus this morning is beginning to lift and thin but expect less insolation as in past days. Highs today will range in the lower 90s with a few hotter spots such as Fayetteville making it in into the 90s. Expect max heat index values to range in the mid 90s in the Triad, near 100 degrees in the Triangle, and in the 100 to 105 range across the the Coastal Plain, Sandhills and Fayetteville area. Lows will be similar or perhaps a degree or two cooler than previous nights, bottoming out in the 71 to 77 range. -Blaes && .SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/...
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As of 230 PM Monday... The main portion of the upper level trough across the Northeast and Mid Atlantic shifts east and lifts on Tuesday and Tuesday night while a shear axis lays down east-northeast to west-southwest from near Cape Hatteras to central GA. The latest GFS and EC both try to close off a portion of the shear axis over eastern GA and the SC coast. At the same time, the associated cold front drops south into NC on Tuesday afternoon and evening and then stalls toward the NC and SC border by daybreak Wednesday. This is a more aggressive and southward solution than recent model runs. This trend would tend to confine precipitation further south and east and could result in additional cooling across our northern tier with the possibility of a layering of additional stratus and then some clearing near the VA border. Not ready to jump all in on this solution, but have trended the forecast that way. Highs on Tuesday will range in the lower 90s but could be cooler near the VA border if the cooler air is aggressive. Lows Tuesday night will range in the 68 to 75 range. -Blaes
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&& .LONG TERM /WEDNESDAY THROUGH SUNDAY/...
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As of 310 AM Monday... Surface high pressure over the northeastern CONUS will extend into the region on Wednesday as a frontal zone lingers south of the CWA. This will be our first break from 90 degree temperatures as highs are expected to be in the mid to upper 80s which is actually below normal for this time of year by a few degrees. This high will remain over the area on Thursday as well although temperatures will begin to creep back towards the 90 degree mark. Although diurnal showers and a possible thunderstorm cannot be ruled out, these days should be fairly dry. Lows in the lower 70s. By Friday, a developing low pressure system, spurred on by a shortwave upper trough, will cross the mid-Atlantic states and move off the coast. As it does so, an east-west oriented front will sag southward towards central NC. Timing in both the GFS and ECMWF solutions is fairly similar and it looks like enhanced precipitation will begin at some point Friday afternoon/evening and continue through Saturday as a secondary low develops along the front. Some uncertainty remains in just how far south the frontal zone will progress which could leave our forecast area dry for Sunday but it is entirely possible that the southern half of the area still experiences precipitation associated with this boundary. After a brief stint back in the 90s on Friday, temperatures will return to the mid to upper 80s for the remainder of the forecast period.
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&& .AVIATION /18Z MONDAY THROUGH SATURDAY/... As of 210 PM Monday... 24-Hour TAF period... VFR conditions are expected to be common across central NC outside of some residual stratus in the Coastal Plain near the KFAY terminal early this afternoon, areas of morning stratus in the Coastal Plain on Tuesday morning, and local restrictions in an isolated shower or thunderstorm. isolated showers and storms will develop this afternoon and could persist into the evening, mainly across the Coastal Plain and Sandhills. West to southwest winds at 5 to 10kts will become light northerly after midnight. Looking ahead... Primarily VFR conditions are expected through much of the work week with scattered, mainly afternoon and evening showers and thunderstorms expected, especially toward the end of the period. Areas of late night and morning stratus can be expected, especially Thursday into Saturday. -Blaes && .EQUIPMENT... The KRAX WSR-88D will be down for the Service Life Extension Upgrade (SLEP) beginning this morning and likely lasting through Thursday or Friday. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...BLAES NEAR TERM...BLAES SHORT TERM...KCP LONG TERM...RE AVIATION...BADGETT/BLAES EQUIPMENT...BLAES

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