356 FXUS64 KHUN 122008 AFDHUN Area Forecast Discussion National Weather Service Huntsville AL 308 PM CDT Fri Apr 12 2019 .NEAR TERM...(Tonight) Issued at 310 PM CDT Fri Apr 12 2019 Based on area observations, the weakening boundary that pushed east into the area earlier today, has not moved much. General broad mid to upper level lift ahead of it has continue to produce a large area of cloud cover that is mostly above 9000 feet across much of northern Alabama. However, not before portions of northeastern Alabama reached highs between 75 and 80 degrees. Expect this cloud cover to linger overnight as the boundary moves northward into southern/central Tennessee as a warm front overnight. Both the ECMWF and NAM12 continue to show more significant precipitation form along this boundary as it does so. Soundings do show a small amount of elevated instability over the area overnight. Therefore, kept isolated thunderstorms in the forecast overnight. Towards midnight into the daybreak hours on Saturday, the coverage of rain will likely be scattered or a bit more numerous. .SHORT TERM...(Saturday through Sunday) Issued at 310 PM CDT Fri Apr 12 2019 This boundary should linger higher chances of precipitation as well as isolated thunderstorms in northwestern Alabama and southern middle Tennessee Saturday morning as the front moves towards the Nashville area by Saturday afternoon. Highs will be a bit cooler near the AL/TN state line (70 to 75 degrees primarily) and in northwestern Alabama due to precipitation and cloud cover expected. Further southeast highs cold still make it into the mid to upper 70s again. These storms could produce some small hail and gusty winds. Models have not changed much with the evolution of the strong storm system moving from eastern Texas eastern Arkansas and Mississippi Saturday afternoon into Saturday evening. An area of strong to severe thunderstorms still looks to move from Texas into central Mississippi Saturday evening. Bulk shear and very strong wind energy continues to forecast with this system. Models do show the better instability developing over Mississippi, southern Arkansas, and Louisiana. CAPE values there mainly are forecast to be between 500 and 1500 J/KG. Further east over northern Alabama, guidance does show instability between 500 and 1000 J/KG. However, the convective activity is forecast to move further east into northwestern Alabama later in the evening towards midnight. This should allow instability to decrease some. However, an instability axis (300 to 800 J/KG) still noses into northwestern Alabama southeastward into Cullman county ahead of this activity. Enough helicity is in place ahead of this convective activity to keep a threat of tornadoes in the forecast, especially west of the I-65 corridor. Further east, lower instability is expected, but models still keep just enough for damaging winds along with a isolated tornado to be possible. Cannot rule out large hail anywhere, but this is expected to be a very low threat. There continues to be some question on how much redevelopment we could have along and just ahead of the main cold front lagging behind this convection overnight and into Sunday around daybreak. However, models continue to show some convection east of I-65 through the afternoon hours and CAPE increasing with time. Strong bulk shear remains in place ahead of the front and some models continue to show good helicity as well. Thus, cannot rule out all modes of severe weather with any redevelopment ahead of the actual cold front. However, damaging winds and large hail look to be more certain at this time. Windy conditions are expected Sunday afternoon outside of thunderstorms with sustained winds around 15 mph with gusts to around 30 mph. .LONG TERM...(Sunday night through Thursday) Issued at 310 PM CDT Fri Apr 12 2019 A few lingering showers are possible Sunday night, but will be light in nature. The big change will colder air pushing into the area behind the front. Strong cold air advection should drop lows into the upper 30s to lower 40s despite lingering cloud cover. In the wake of the departing upper trof, a rather tight pressure gradient at the surface should be relaxing on Monday. This will allow cold advection to rapidly transition to warm through the day as a surface and 8h ridge positions shifts east into the lower OH and TN valleys. Expecting highs back into the 60s Monday afternoon as a result. By Tuesday, as the ridge positions shift east of the spine of the Appalachians, warm advection and column warming due to insolation should yield 8h temps in the 13-14C range, and 9h temps in the 17-18C range. Thus, blended guidance in l-m70s looks good at this point. Same goes on Wed with continued south-southwest low level flow (i.e. 8h flow accelerates to 25-35kt). Moisture transport will also increase with elevated showers potentially shifting into our western counties on Wednesday. Another strong upper low and trough pushes out of the Rockies in to the Upper Midwest/Missouri Valley on Wed-Thu. There are latitudinal differences amongst the medium range models. But both yield a deepening surface low in KS or MO Wed lifting northeast into the western Great Lakes by late Thu. This along with a a rather classic cold frontal band southward along the middle and lower MS valleys Thursday. At this point, it is far to early to predict convective impacts, but situation will need to be monitored closely with a deep moisture fetch over a long period next week preceding the front, good frontal convergence, and ample deep layer shear. && .AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon) Issued at 1208 PM CDT Fri Apr 12 2019 VFR conditions are expected at both terminals much of the period. A warm front is expected to move north and through both terminals just before daybreak on Saturday. As this occurs, cannot rule out -tsra activity near it. If this slows, then lower CIGS/VSBYS may be possible with lingering -TSRA activity at KMSL into the early morning hours. This forecast mirrors a quicker movement of this front northward and exits any -TSRA by 08Z at both terminals. Due to uncertainty of coverage with this activity, only have include a predominant VCSH after 13/04Z at both terminals. A tempo group was included at both terminals though between 04Z and 08Z with -TSRA and MVFR CIGS/VSBYS to account for any activity directly impacting both terminals. Otherwise, expect VFR conditions to return the remainder of the TAF period. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...NONE. TN...NONE. && $$ NEAR TERM...KTW SHORT TERM...KTW LONG TERM...12 AVIATION...KTW For more information please visit our website at weather.gov/huntsville.