433 FXUS64 KHUN 121117 AFDHUN Area Forecast Discussion National Weather Service Huntsville AL 617 AM CDT Tue Mar 12 2019 .UPDATE... For 12Z TAFS. && .NEAR TERM...(Today) Issued at 305 AM CDT Tue Mar 12 2019 GOES-16 water vapor imagery was showing a steady stream of cirrus clouds progressing over the area due to persistent westerly flow aloft early this morning. High pressure centered over the Ohio Valley will slowly translate eastward today. Subsidence from the surface high will keep winds light and variable. As the high moves eastward, mid-level winds become southerly, streaming in Gulf moisture and causing cloud cover to increase this afternoon from west to east. Upper level ridging will be amplified by a deepening shortwave trough over the Baja Peninsula as it lifts into the Southern Plains. This upper level ridging will bring a slight warming trend to the Southeast for the next several days. We kick off this warming trend today as high temperatures reach the mid to upper 60s this afternoon. .SHORT TERM...(Tonight through Thursday night) Issued at 305 AM CDT Tue Mar 12 2019 A surface trough will develop and deepen tonight as it tracks with the upper level shortwave through the Plains. Surface winds over the Mid South will veer to southeasterly as the surface high progresses eastward over the Mid Atlantic. Mid-level cloud cover will continue to build tonight, which will help insulate the atmosphere and keep low temperatures tonight in the low to mid 50s. As the aforementioned surface low tracks northward and the high remains over the Mid Atlantic, the surface pressure gradient will tighten in response. This will cause southerly winds to surge to 15-20 mph during the day Wednesday and into Wednesday night, potentially gusting 25-30 mph at times. A wind advisory may be required for tomorrow through Thursday. High temperatures tomorrow will reach the upper 60s in Northeast Alabama and up to the mid 70s in Northwest Alabama. The upper level shortwave will continue its track from the Southern Plains into the Great Lakes Region Wednesday night into Thursday. As the surface low lifts with the shortwave, a warm front will progress through the area Wednesday night. At the same time, a fairly strong low level jet with winds at 850 mb of 60-70 kts will enter Northwest Alabama. 00z guidance has begun to show the LLJ lingering over the Mid South longer throughout the day Thursday. Soundings indicate that surface-based instability will increase Thursday afternoon, as well. Because of the delay for the LLJ exiting the region, there may be some overlap with the surface-based CAPE. This would increase the potential for strong to severe storms on Thursday. There is low confidence on timing, as this event is still three days out. Overall, scattered to numerous showers with isolated thunderstorms are expected to begin late Wednesday night into early Thursday morning. Some guidance continues to suggest that there may be a break in precipitation during the day Thursday ahead of the main line of storms ahead of the approaching cold front. Any potential breaks in cloud cover would increase the amount of warming, and therefore increase the potential for strong to severe storms Thursday afternoon and evening. Either way, strong winds, lightning, and heavy rainfall continue to be the main threats with this system late Thursday. Rainfall totals will be 1-2" with isolated higher amounts possible. The line of storms will progress through the Mid South Thursday night, and should be out of the area by daybreak Friday. .LONG TERM...(Friday through Monday) Issued at 305 AM CDT Tue Mar 12 2019 Lingering light rain over the southeast portion of the area will quickly taper off Friday morning as a cold front moves through the area. The associated upper trough will broaden as it moves east, with zonal flow aloft over the TN Valley. At the surface, a Canadian high pressure system will build into the region, with north-northwesterly flow sending much cooler and drier air into the area. Although skies will clear through the day, CAA will keep temps from warming much, with highs struggling to rise above the upper 50s. The high will continue to build through the overnight hours Friday, though winds will stay elevated enough to prevent temps from bottoming out too much, though the continuous CAA will help lows fall into the mid to upper 30s. The center of the surface high will shift into the Ohio Valley on Saturday, with winds becoming more northerly before shifting to the northeast Saturday night. The continuous northerly flow will keep temps on the cool side for the middle of March, with highs in the lower 50s. Winds will lessen Saturday night as the high moves through the region and the pressure gradient relaxes. Under mostly clear skies, temps will drop into the lower 30s, with some of our northern areas dropping below freezing for a couple of hours early Sunday morning. A shortwave will round the base of a broad upper trough and move through the TN Valley Sunday into Monday, though forecast models differ on this exact timing. Not expecting much impact to the sensible weather pattern across the region, other than to keep temperatures slightly below normal for the remainder of the extended. Highs on Sunday and Monday will generally remain in the upper 50s to around 60 degrees, with overnight lows in the mid to upper 30s. && .AVIATION...(For the 12Z TAFS through 12Z Wednesday morning) Issued at 617 AM CDT Tue Mar 12 2019 Scattered cirrus decks will continue to stream in from the west this morning. Light northeast winds will gradually veer to easterly this afternoon then southeasterly tomorrow morning. Southeast winds will pick up near 10 kts shortly after daybreak tomorrow. VFR conditions will prevail through the TAF period. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...NONE. TN...NONE. && $$ NEAR TERM...30 SHORT TERM...30 LONG TERM...73 AVIATION...30 For more information please visit our website at weather.gov/huntsville.