Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 200827 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 415 AM EDT Tue Jun 20 2017 .SYNOPSIS... A cold front located across the eastern slopes of the southern Appalachians early this morning will move east and then stall across the central and eastern Carolinas today and tonight. The The front will gradually dissipate over the region on Wednesday. && .NEAR TERM /Today and Tonight/... As of 415 AM Tuesday... The latest surface analysis shows the cold front was located across the eastern slopes of the Appalachians. VWP observations and the SPC mesoanalysis shows the 925 hPa and 850 hPa trough now extending from just east of KRIC southwest to near KBUY to near KCLT, roughly coincident with the back edge of the shield of showers and embedded thunderstorms. This area of showers should lift northeast during the next few hours and should be largely clear of the RAH CWA by 12Z. Not surprisingly given the moist air mass, convection should redevelop late this morning toward midday near and southeast of the 925 hPa and 850 hPa boundary across GA and SC with the precipitation spreading northeast into NC. As the boundary stalls across the Coastal Plain and the Sandhills by midday, the southerly flow south of the boundary will strengthen and the boundary will lift north with time. This will allow the sharp nw edge to convective precipitation shield to gradually ease northward into the southern and eastern Piedmont, enhanced by northward ejecting outflow boundaries. Tough call on far northwest the precipitation will push but will include PoPs up to the I-85 corridor. The convection will be most widespread this afternoon and evening and then slowly decrease in coverage through the evening into the overnight hours. The airmass across the region will be much more stable than previous days with MLCAPE values ranging from 500-1000 J/kg across the southeast ahead of the front, around 500 J/Kg near the boundary in the Triangle and even more stable toward the Triad. Given the limited instability and modest shear, organized severe weather is not expected but the northeast-southwest orientation of precipitation closely parallel to the storm motion could lead to localized heavy rain and possible flooding. The good news is that the heaviest precipitation will be well removed from locations across the northern Piedmont and Triad that experienced flooding on monday night. Highs today will range between 80 to 85 degrees. Lows will vary more tonight than in previous mights with cooler air moving into the Triad, lows will range in the mid 60s in the Triad to the upper 60s to lower 70s elsewhere. -Blaes && .SHORT TERM /Wednesday/... As of 415 AM Tuesday... The upper level trough axis slides east across the Mid Atlantic and Carolinas on Wednesday and then offshore. Behind the trough axis, a drier air mass and subsident pattern will work into the region with PW values ranging from 1.5 to 2.0 inches early Wednesday dropping to 1.3 to 1.5 inches by Wednesday evening. The lingering cold front across the eastern Carolinas will dissipate on Wednesday. The air mass across central NC will only be weakly unstable on Wednesday with the best forcing for ascent located near the deteriorating surface boundary. Will keep afternoon PoPs in the 15% northwest to 35% far southeast. Highs will range from 80 to 85. -Blaes && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... As of 147 AM EDT Tuesday... The chance of showers and thunderstorms will increase again Thursday as deep subtropical moisture surges northward again around the Bermuda surface high pressure. The influx of deep subtropical moisture will be aided by the remnants of the tropical disturbance that is forecast to get pulled NW into the western Gulf Coast states Thursday. A broad southerly flow from a wide open Gulf of Mexico will lead to PW`s increasing again to 2+ inches by Thursday and Friday, into the weekend and early next week. Convection should be largely diurnally driven, with likely POP during the afternoon and evening, then high chance POP`s overnight Thursday into Monday. Rainfall may be enhanced by a cold front that is expected to slowly move SE into the region Sunday into Monday. QPF of 2-4 inches is expected late week into the weekend into Monday. With the recent heavy rain over portions of the Triad, Triangle, and the Piedmont in general, a flooding threat may develop. Temperatures should be above normal given the very high dew points in the 70s, keeping nightly lows 70+ and possible 75 in the SE. Highs should be in the mid 80s NW ranging to lower 90s SE each day, with some cooling aided by the expected heavy rain and cloudiness early next week. && .AVIATION /06Z Tuesday through Saturday/... As of 240 AM Tuesday... A large area of convection extending from near Roanoke Rapids southwest through the Triangle to near Charlotte NC is associated with an approaching cold front. The showers and storms will slowly shift southeast through daybreak with reduced cigs and vsbys and an embedded thunderstorm or two. Expect cigs to fall into the MVFR and possibly IFR range by daybreak in most location with most of the convection dissipated by this time. Conditions will improve after sunrise with VFR conditions expected behind the front in the Triad today at the KINT and KGSO terminals. Near and southeast of the front, after a period of VFR conditions this morning, scattered convection is expected to redevelop this around midday and this afternoon with the greatest coverage across the Sandhills and southern Coastal Plain near the KFAY terminal. Another round of low stratus is likely to develop late tonight. Looking beyond the 24 hour TAF period...a typical summertime regime is expected with perhaps greater than climatological coverage during the period. This pattern will feature scattered diurnal afternoon and evening convection with periods of early morning stratus. During the period it appears convective coverage will be more limited on Wednesday into Thursday and increase into the weekend. -Blaes && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Blaes NEAR TERM...Blaes SHORT TERM...Blaes LONG TERM...Badgett AVIATION...Blaes

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