Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 290138 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 935 PM EDT WED SEP 28 2016 .SYNOPSIS... A strong upper level low over the Great Lakes will drift southward through the Ohio valley tonight, stall over eastern Tennessee and Kentucky Thursday and Friday, then move back north through the Ohio valley and lower Great Lakes this weekend. && .NEAR TERM /THROUGH TONIGHT/... As of 935 PM Wednesday... Severe thunderstorm watch will expire at 1000 PM... Localized flash flooding continues a threat. We will allow the Severe Thunderstorm Watch to expire at 1000 PM. Parameters indicate stabilizing of the boundary layer while large scale lift arrives from the west. Additional severe threat should be localized and not widespread. However, the threat of additional flash flooding is increasing as training of storms continues in favored areas. Two areas of strong to severe thunderstorms continue through our region. One line was located SW to NE through the southern Piedmont into the Sandhills. The other was located from near Charlotte NE through the Triad region. Both of these lines have been problematic with flash flooding around or north of Fayetteville into Harnett County, and over Greensboro. Large hail has been the main severe weather hazard with both lines. It appears that the low level jet will increase with strong surface moisture convergence into central NC overnight. The two distinct lines of storms may merge into one line toward late evening or just after midnight. This would place the main severe and flash flood threats from the Triad to the Triangle overnight. Some areas have already had 1 to 3 inches of rain with locally 4 inches in Harnett and NW Cumberland Counties. The Triad is currently in line for additional very heavy rain with additional flash flooding appearing likely, especially east of Winston-Salem, with Greensboro to Burlington targeted at the moment. && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... As of 120 PM Wednesday... Additional showers and storms with training moderate to heavy rain remains likely over Central NC Thu, with a gradual shift to the ENE on Fri. The powerful mid level low will continue to sit and spin over KY on Thu before drifting/wobbling slightly northward to IN on Fri, with lobes of DPVA sweeping through western and central NC, along/atop the very slow-moving north-south oriented cold/occluded surface frontal zone. PW values remain elevated (over 1.5") over all but the far west Thu, shifting to east of I-95 Fri, beneath nearly continuous bands of pronounced upper divergence. The WRF-ARW/NMM both start the day Thu with a band of convection bisecting the forecast area, drifting slowly eastward through the far eastern Piedmont and Coastal Plain through Fri, filling in with better coverage with time, with a cell motion that presents a threat for training and resultant localized flooding. Will retain, with minor tweaks, the overall pattern of the earlier forecast, with lower chance pops west and high pops in the central/eastern CWA Thu, trending lower WSW to ENE through Fri but remaining high in the far eastern/NE forecast area Fri, tapering off further Fri night. Temps both days will be held down by clouds/precip in the east and by lowering post-front thicknesses in the western CWA. Highs in the upper 70s to lower 80s Thu and in the mid 70s to lower 80s Fri, still slightly above seasonal normals. Lows 60-68 Thu night and 54- 65 Fri night. -GIH && .LONG TERM /Saturday through Wednesday/... As of 320 PM Wednesday... A few showers are likely to linger Sat into Sun in the eastern CWA, along and east of the frontal zone, but otherwise this period appears mostly dry. The large mid-upper low centered over IN early Sat will drift across lower MI and slowly fill through Sun before being drawn across the St. Lawrence Valley and Northeast states by a shortwave trough rotating around a northern Atlantic polar vortex. This, in conjunction with a large longwave trough shifting onto the West Coast and over the western CONUS, will gradually build ridging over the eastern CONUS heading into early next week. The surface front over the East will continue to ease eastward and wash out with a weakening low level wind field fostering frontolysis. A few mainly afternoon showers are possible along this diffuse frontal zone over the far eastern counties of NC early next week, but the PW will be quite low elsewhere with a lack of instability, and will keep the forecast mostly dry. Temps should hold a bit above normal through the period, following thickness trends, with highs mostly in the upper 70s and lower 80s, and lows in the upper 50s to mid 60s. Uncertainty grows during the middle of next week, with a lot of questions regarding the fate of what is now Tropical Storm Matthew, located north of Venezuela this afternoon. However, at this time, it appears that it will still be far from NC through Wed. Check with the National Hurricane Center for the latest on Matthew. -GIH && .AVIATION /00Z WEDNESDAY THROUGH MONDAY/... As of 830 PM Wednesday... Bands of showers and storms will continue to develop and edge EWD for the next several hours, before decreasing in coverage and intensity late tonight and early Thu. Sub-VFR conditions; hail mostly less than an inch in diameter; and gusty winds up to 30-35 kts will accompany the storms. In addition, a blanket of low (LIFR) stratus is expected to redevelop mainly over the Piedmont (INT/GSO/RDU) late tonight, before lifting and scattering to VFR with diurnal heating between 13-16Z Thu. That heating, in conjunction with lift supplied by a slow-moving wave of low pressure and associated frontal zone, will also cause showers and storms to increase in coverage and intensity once again by midday-early afternoon Thu. Outlook: Drier air is finally expected to filter into the region on Friday, leading to improved aviation conditions through the weekend. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Badgett NEAR TERM...Badgett SHORT TERM...Hartfield LONG TERM...Hartfield AVIATION...MWS/BS is the U.S. government's official web portal to all federal, state and local government web resources and services.