214 FXUS64 KHUN 141210 AFDHUN Area Forecast Discussion National Weather Service Huntsville AL 610 AM CST Fri Feb 14 2020 .UPDATE... For 12Z TAFS. && .NEAR TERM...(Today) Issued at 440 AM CST Fri Feb 14 2020 West-southwesterly flow aloft continues across the TN Valley this morning, in the gradient between a subtropical ridge centered north of the Greater Antilles and a positively-sheared longwave trough extending from the Canadian maritime provinces southwestward into the southern Plains. At the surface, moderate northerly flow to the south of an Arctic high building into western IL will maintain strong low-level CAA this morning, and with temperatures anticipated to fall at a rate of 1-2 degrees per hour through 13-14Z, temperatures will likely reach the l-m 20s before stabilizing. Due to the combination of cold temperatures and elevated winds, morning wind chills will bottom out in the 10-15 degree range for valley areas, and in the 5-10 degree range for elevated terrain locations where northerly flow will be sustained around 15 MPH with occasional gusts of 20-25 MPH. Otherwise, current RGB satellite imagery reflects a broad area of low stratus clouds and pockets of light snow flurries spreading southward from western KY into middle TN, likely initiated by weak synoptic scale ascent to the east of the aforementioned mid-level trough. This regime will likely impact portions of the TN Valley, until the mid-level trough axis crosses the region during the late morning/early afternoon hours, and we have increased morning cloud cover region-wide and introduced a very low probability for snow flurries across the northeastern portion of the forecast area. Due to morning cloud cover and moderately strong cold air advection which will persist through the afternoon, high temperatures will only reach the 38-42 degree range in valley areas and 34-38 degree range in higher terrain. .SHORT TERM...(Tonight through Sunday night) Issued at 440 AM CST Fri Feb 14 2020 Models suggest that a shortwave ridge aloft (in the wake of today's longwave trough) will quickly translate across the region this evening, before mid/high-level flow backs to the west-southwest once again by 12Z Saturday. With dewpoints in the teens and low-level flow predicted to weaken/veer to northeast as the Arctic ridge builds into New England, conditions appear optimal for strong radiational cooling, and a hard freeze is anticipated for all forecast zones featuring morning temps in the upper teens/lower 20s. Modest warm air advection aloft will begin on Saturday downstream from a weak 500-mb trough spreading across the northern/central Plains and into the upper MS Valley, and this coupled with light- moderate southeasterly flow in the boundary layer will yield high temps in the l-m 50s. Large scale ascent will begin to increase on Saturday evening, as the southern portion of the aforementioned 500-mb trough shifts southeastward into the TN Valley. Although this will likely result in the development of a thick deck of altostratus clouds by early Sunday morning, forecast sounding indicate a very dry subcloud layer and we will maintain a dry forecast through 12Z. Conditions will become slightly more favorable for a few light showers during the day on Sunday as the low-level airmass moistens and another weak mid- level wave ejects east-northeastward from the western Ozarks into the OH Valley in prevailing zonal flow aloft. Low clouds and perhaps a few light showers will persist across the region on Sunday night, with lows only falling into the l-m 40s. .LONG TERM...(Monday through Thursday) Issued at 440 AM CST Fri Feb 14 2020 High pressure will continue to shift off to the east into the Mid Atlantic region on Monday, allowing for south to southwesterly flow to develop across the Deep South. The end result will be a pronounced warming trend and a return of Gulf moisture as temperatures rise back into the mid to upper 60s and dewpoints climb into the mid 50s. A surface low will lift NE from the Southern Plains into the Great Lakes on Monday, pushing a cold front into the Mid-Mississippi Valley. A secondary low along the Gulf Coast will also develop ahead of the front, lifting north and spreading isolated to scattered light rain showers into the region by late Monday afternoon/evening along/ahead of a warm front. As this feature tracks north into the region overnight, numerous to widespread showers are expected. A warm, moist air mass will be in place by early Tuesday. This, combined with some appreciable deep layer wind shear and some modest elevated instability may allow for a few isolated thunderstorms as the aforementioned cold front drops south into the region later in the day. The main story, however, will be another round of moderate to heavy rainfall, with storm total amounts of 1.5" to 2" likely resulting in some additional areal flooding issues and continuing some of the river flooding taking place at least through the middle of next week. The cold front will begin to drop south of the area Tuesday night, with a cooler, and drier air mass trying to work its way into the region in its wake. The boundary may briefly stall just south of the region, so we'll be caught between a strong high pressure ridge trying to build in from the north and the front across Central Alabama. Models are still a bit unsure on the details regarding the location of the boundary, but for now think it's a pretty safe bet to keep denser cloud cover in the forecast, along with some isolated to widely scattered rain showers for both Wednesday and Thursday. Lingering cloud cover over the area will limit the degree of cooling that takes place behind the front. However, think there will be enough moisture left over and colder air aloft to potentially have a few areas of a rain/snow mix (mainly across S. Middle Tennessee) in a few elevated locations early Thursday morning. Otherwise it will just be colder with highs in the 40s expected for Thursday. Alas, the roller coaster pattern of warm and cool temperatures continues into late February. && .AVIATION...(For the 12Z TAFS through 12Z Saturday morning) Issued at 610 AM CST Fri Feb 14 2020 Current satellite imagery depicts a vast area of low stratus clouds building southward into northern AL from adjacent portions of middle TN. This regime will likely continue until the axis of an upper-lvl trough crosses the region later this morning, and we will include tempo groups from broken cigs arnd 2500 ft at both terminals thru 16Z. Otherwise, a few mid-level clouds are expected late this morning and early this aftn, before skies clear completely for the second half of the TAF period. Sfc winds will remain from the NNW at 10G18 knots thru late this aftn, but should veer to the NE and diminish overnight as an arctic ridge of high pressure spreads eastward into New England. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...NONE. TN...NONE. && $$ NEAR TERM...70/DD SHORT TERM...70/DD LONG TERM...AMP.24 AVIATION...70/DD For more information please visit our website at weather.gov/huntsville.