808 FXUS64 KHUN 221746 AFDHUN Area Forecast Discussion National Weather Service Huntsville AL 1146 AM CST Fri Feb 22 2019 .UPDATE... For 18Z TAFS. && .NEAR TERM...(Rest of Today) Issued at 941 AM CST Fri Feb 22 2019 Light to moderate rain continues to push to the northeast across the TN Valley this morning, driven by low level convergence around 850 mb and a weak shortwave moving through the southwest flow at 500 mb. Latest guidance suggests that this axis will not move very much through the next several hours, keeping the area under at least light rain through the mid afternoon hours. Heavier precip was noted just south of our area, which may lift northward and move over areas that have received the heaviest rain over the last 24 hours. Needless to say, with fully saturated soils and flooding ongoing across portions of the area, conditions will only get worse before the rain ends. When the rain ends is still in question, as this largely remains contingent on the northward movement of the convergence axis. Short term models do should this lifting north of the area by the late afternoon hours, which would bring a brief break in the overall rainfall. However, another inch or 2 of rainfall is expected today, especially over northwest Alabama. Extreme caution should be used for any travel across the TN Valley today. Temperatures today will generally be mild, with highs rising into the mid to upper 60s .SHORT TERM...(Tonight through Sunday) Issued at 356 AM CST Fri Feb 22 2019 A frontal boundary that has been positioned well south of the forecast area since the early half of the week should slowly continue moving northward as a warm front, finally moving northward across most of the forecast area on Saturday morning. A warmer and more unstable airmass will help boost high temperatures to around 70 for most areas west of Huntsville. Cold high pressure off of the Mid Atlantic coast will continue to produced a cold air damming effect over our far eastern areas Sat. Think the push of warmer air northward should overcome the colder air for the most part, with some of the far NE AL valleys staying a few degrees cooler than points west. An area of low pressure over the 4-Corners region will move eastward across the CO/NM region tonight, then rocket NE-ward towards the upper Mississippi Valley by Sat evening, and southern Great Lakes before daybreak Sunday. A cold front trailing south of this parent low will move across the area after dusk on Sat. The approach of this front, along with much higher lower level moisture values and resultant instability, and decent shear will set the stage for strong to severe thunderstorms. The stronger severe parameters will generally be across our western areas on Sat afternoon/evening. All modes of severe weather are possible Sat afternoon/evening, especially over NW AL. The cold front passing in a west to east manner should end the severe threat overnight Sat, as drier/cooler air from the NW filters to the SE. Sunday will feature a dry day for a change, with a return of direct solar insolation too! With cooler high pressure building in, highs will be close to seasonable norms in the mid/upper 50s. .LONG TERM...(Sunday night through Thursday) Issued at 356 AM CST Fri Feb 22 2019 Quiet and more seasonal like wx conditions look to prevail across the cntrl TN Valley heading towards the end of the weekend period. Latest global model runs are still showing a large ridge of high pressure at the sfc out of the nrn Plains gradually building southeast into the Midwest states, while a broad WSW flow regime develops over most of the srn Plains/SE states. With cold air advection filtering into the area from the north, a seasonably cool night is xpcted into the early morning hrs Mon, under mostly clr skies, with lows falling mainly into the lower/mid 30s for most locations. This gen trend should continue into the daytime period Mon, as the sfc high moves further southeast into the Great Lakes/Midwest regions. Afternoon temps are xpcted to trend right around normal for this time of the yr, with highs climbing predom into the mid/upper 50s. With the upper flow pattern becoming more zonal over much of the region, the quiet wx pattern looks to prevail thru Mon night and into Tue, with lows early Tue mainly in the mid 30s before temps rebound more into the lower to perhaps mid 60s later in the day. The sfc high then looks to translate more into the nrn/mid Atlantic Basins as mid week approaches, thereby allowing more of return flow pattern to evolve across the Lower MS/TN Valley areas. This should translate into Gulf moisture spreading back into the region as cloud cover begins to increase Tue night/Wed. With the southerly fetch of slightly warmer conditions/temps, temps early Wed look to be more in the lower/mid 40s, before again rebounding into the lower/mid 60s that afternoon. There are some discrepancies between the 00Z ECMWF/GFS with respect to the overall pattern by the middle of next week, with the latest GFS suggesting a more robust influx of moisture into much of the region. Both model suites show another cold front diving southeast into the TN/OH Valley states late Tue into Wed, as the sfc high translates more into the mid Atlantic. The latest GFS though hints at a stronger low level convergent pattern along/ahead of the front, coupled with a bit higher dynamic forcing, while the 00Z ECMWF keeps most of the precip/QPF suppressed well south/west of the local area. As such, stayed close to the blended guidance regarding the next chc of rainfall, with mainly just some sct showers possible Tue night thru Wed evening. Even with the influx of cooler air behind this next front, lows early Thu again look to be predom in the lower/mid 40s before gradually climbing into the mid/upper 50s that afternoon. && .AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon) Issued at 1140 AM CST Fri Feb 22 2019 The complicated weather situation across the region currently will likely require amendments to TAF ceilings/vis over the next 24 hours. Nevertheless, the latest TAF forecast represents the latest best thinking and attempt at timing of impacts, while conveying the big picture. Large scale processes are currently driving the generation of a broad area of RA to our west, while showers are developing in response to cold pool interaction to our S-SW. In between, rain has gradually decreased over the KHSV and KMSL TAF sites this morning. After 00Z tonight, a low-lvl warm front will cross the area and may instigate a period of lower (MVFR) ceilings and SHRA activity. After 12Z, instability aloft may be sufficient for TSRA activity at KMSL first, then KHSV. PROB30 groups were added to address this threat. Winds will gradually increase especially later tonight and veer from the SE. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...Flash Flood Watch through late tonight for ALZ001>010-016. TN...Flash Flood Watch through late tonight for TNZ076-096-097. && $$ NEAR TERM...73 SHORT TERM...RSB LONG TERM...09 AVIATION...KDW For more information please visit our website at weather.gov/huntsville.