253 FXUS64 KHUN 200254 AFDHUN Area Forecast Discussion National Weather Service Huntsville AL 954 PM CDT Sat Oct 19 2019 .NEAR TERM...(Rest of tonight) Issued at 954 PM CDT Sat Oct 19 2019 Light rainfall from earlier today, which was generated by the combined lifting effects from a vort lobe which split off the circulation of TS Nestor and the southern end of a mid-latitude trough over the northern Plains, has now come to an end across the TN Valley. And, with the source of mid-level ascent expected to advance further northeastward into the southern Appalachians, we will maintain a dry forecast for the region overnight. However, stratus clouds in the wake of the rainfall will be much slower to dissipate, and we expect these to persist through perhaps the mid-morning hours on Sunday. Based on recent trends in satellite data and surface observations, cloud bases appear to be rising sufficiently for the development of a patchy-areal coverage of fog later this evening. Due to the widespread coverage of light rainfall and expectations of weak (if any) flow in the boundary layer, the fog could become fairly widespread/locally dense early Sunday morning. It still appears as if lows will be in the l-m 50s, and essentially no changes were made to the temp/dewpoint forecast in this update. .SHORT TERM...(Sunday through Monday night) Issued at 243 PM CDT Sat Oct 19 2019 Cloud cover may begin to diminish some during the day Sun, as drier air above H85 spreads into the region out of the WSW. With sfc winds also turning more to the south on Sun, afternoon temps look to rebound well into the mid/upper 70s. This seasonably warm trend will continue into Sun evening, with cloud cover beginning to gradually spread back into the area from the west, well ahead of the next oncoming storm system. Temps early Mon will reflect this trend, with lows more in the upper 50s/lower 60s. Showers and perhaps a few tstms will then begin to develop/spread west to east into the cntrl TN Valley during the day Mon, as a cold front approaches the MS River. Showers/embedded tstms will increase during the afternoon/evening hrs Mon, as the front approaches NW AL. Instability remains fairly marginal thru the day Mon, with SBCAPE values generally in the 500-1000 J/kg range. Slightly more favorable wind energy/shear looks to develop ahead of the front late Mon, with 0-6km Bulk Shear values climbing above 50kt. However, better forcing may lift more to the north, as the front begins to move thru much of the region Mon night. Nevertheless, a line of strong/marginally severe tstms is xpcted to sweep ewd thru the TN Valley late Mon afternoon/evening. Given the Bulk Shear coupled with some turning in the low level wind field, damaging wind gusts and perhaps a brief tornado remain the primary threats with any stronger/severe storms. Lingering showers/tstms should then quickly taper off from the west late Mon night, as the cold front moves east of NE AL. .LONG TERM...(Tuesday through Friday) Issued at 243 PM CDT Sat Oct 19 2019 After a Quasi-Linear Convective System/squall line and cold front pass across the area Monday evening and night, dry conditions will return for the mid and latter half of the work week. The cold front by daybreak Tuesday should be located from near the Tri Cities of VA/TN, to across central Georgia to west of Apalachicola. The parent low over the northern Great Lakes early Tuesday should move northward to the Hudson Bay. High pressure building eastward over the CONUS from the northeast Pacific basin will be the main controlling feature regarding our sensible weather through the latter portion of the work week. Slightly cooler than seasonable high/low temperatures are forecast for the Tue-Wed time frame (normally around 72/48). High temperatures on Tuesday should range in the mid 60s, with mid 60s to near 70 on Wednesday. Lows Tuesday night will range in the lower 40s, and mid/upper 40s Wednesday night. Temperatures should return to seasonable levels in the lower 70s on Thursday, as a southerly flow becomes more predominate. The return flow will bring additional moisture from the Gulf well inland. This moisture and a system to our west developing and nearing will return rain chances beginning Thursday night, continuing on Fri/Sat. The model timing into Friday was in rather good agreement, with the GFS a tad faster returning moisture sufficient for showers. Differences between the deterministic runs become more noticeable Fri evening into Saturday. The GFS tended to bring a frontal type system across the area Sat morning, while the ECMWF was hinting at an upper low forming over OK/TX slowing down the progress of a boundary, and prolonging the rain event. Either case does show some instability and moderate shear on Fri. However taking into account the ECMWF trend, will hold off on thunder for late next week. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 636 PM CDT Sat Oct 19 2019 The western edge of light rainfall associated with a passing upper- lvl disturbance will continue to shift eastward and out of the local area early this evening. However, latest model guidance suggests that little if any flow/mixing will occur overnight, and thus we expect low stratus clouds to persist thru at least sunrise on Sunday morning. We have also indicated the development of MVFR vsby reductions in light BR/FG beginning arnd 20/03Z, with cigs descending to IFR levels by 06Z. A tempo group for LIFR cig/vsby was also included at both HSV/MSL btwn 09-13Z. Conditions should begin to improve by 14Z as SSE low-level flow slowly becomes established across the area, with VFR conditions returning to both terminals by 16Z. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...NONE. TN...NONE. && $$ NEAR TERM...70/DD SHORT TERM...09 LONG TERM...RSB AVIATION...70/DD For more information please visit our website at weather.gov/huntsville.