362 FXUS64 KHUN 231720 AFDHUN Area Forecast Discussion National Weather Service Huntsville AL 1120 AM CST Wed Jan 23 2019 .UPDATE... For 18Z TAFS. && .NEAR TERM...(Rest of Today) Issued at 952 AM CST Wed Jan 23 2019 The cold front has moved closer and based on surface observations and radar analysis the front is nearing NW AL. A few bands of showers continue to move across the TN Valley ahead of this feature and made adjustments to the PoPs to reflect this. The question for this morning/early afternoon is whether or not we'll be able to get enough instability for any thunderstorms. While some guidance does have very limited MUCAPE (<100 J/kg) over the area right along the front, radar is showing a developing line of storms in southern MS with additional storms over southern AL. These will likely result in keeping much of the instability bottled up to our south and thus any thunderstorms should stay south of the area. The heaviest rainfall will arrive behind the front as lift tied to a elongated trough over the central US moves towards the area. Temperatures will plummet quickly behind the front with values dropping down into the 40s to upper 30s by this evening. The Wind Advisory for areas west of I-65 will continue through 18z and the rest of the area will remain under the advisory until 21z. The strongest winds have likely occurred as the pressure gradient is starting to weaken as the front approaches. Winds behind the front while gusty should stay below criteria. The rest of the forecast is in good shape. .SHORT TERM...(Tonight through Friday night) Issued at 339 AM CST Wed Jan 23 2019 Rain will end from west to east tonight, as drier air moves in from the NW. A surface high in the 1040mb magnitude range over Alberta will build to the SE, bringing another dose of Canadian/Arctic air to the Deep South. This makes for a tricky forecast for the late evening and overnight regarding wintry weather. Air temperatures towards midnight should be nearing the freezing point. Forecast soundings suggest near saturated temps of -3 to -5C to 850mb, then much drier above that, for a short duration. Our Forecast Builder came up with light freezing rain in the higher terrain of eastern Franklin county TN, along with eastern Jackson and northern DeKalb counties too. But given a warm and wet ground beforehand, do not anticipate any issues with this brief wintry mix. A steady NW wind of 10-15 mph should also help dry exposed surfaces in the evening, helping minimize the formation of significant icing before sunrise Thursday. For Thu, quite a different day is expected regarding temperatures. After highs in the mid/upper 50s today, the highs on Thu will struggle to reach mid 40s, with most locations only in the lower 40s. WNW winds around 10 mph should create wind chill values about 10 degrees cooler. The Arctic high will show its true colors Thu night and Fri night, with lows falling into the lower 20s. Highs on Fri will only be in the low/mid 30s. Normal highs for that time of year are around 52 degrees. .LONG TERM...(Saturday through Tuesday) Issued at 339 AM CST Wed Jan 23 2019 The longwave trough aloft maintains its grip on most of the CONUS throughout the long term period. Surface high pressure progresses over the Southeast on Saturday, causing light surface winds to veer to southerly. Slight increase in moisture will be enough to maintain cloud cover, but light southerly flow will be enough to allow high temps on Saturday to climb into the mid 40s. A low pressure system will track over the Northeast with the weak cold front progressing through the Tennessee Valley Sunday night. Without an opportunity to regain moisture, the only impacts from this front will be a slight increase in winds as they become easterly Sunday. Despite the weak cold front, temperatures will see a gradual warming trend, reaching the upper 40s on Sunday and finally back to seasonal averages in the low 50s on Monday. Average temperatures will be short-lived, as a true arctic airmass will dig down into the CONUS early next week. A shortwave trough looks to track through the longwave trough and approach the region by Tuesday. A Clipper system will also track down into the Central Plains before lifting into the Ohio Valley and then the Northeast early next week. Expect winds to increase once again ahead of this system, with most of the rain behind of the associated cold front. While timing has come into better agreement between models, this system is still six to seven days out and much can change. At this time, it looks as though the best shot for rain will be late Monday into early Tuesday. The arctic air arrives Tuesday morning, allowing the lingering precip to gradually become a wintry mix Tuesday afternoon with only minor accumulations forecast. && .AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon) Issued at 1120 AM CST Wed Jan 23 2019 The cold front is approaching the KMSL terminal as of 17z and should be near the KHSV terminal by 19z. Expect a brief drop to IFR cigs/vis as the heavier showers along this front move across the terminals. Additional rain behind the front will likely keep cigs/vis between IFR to low end MVFR through the afternoon and into the evening hours. We won't see improvement in cigs/vis until closer to 08-12z Thursday with MVFR conditions. Winds for much of the period remain out of NW with speeds around 10kts and gusts initially up to 25kts but gradually weakening with time. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...Wind Advisory until 3 PM CST this afternoon for ALZ005>010-016. Wind Advisory until noon CST today for ALZ001>004. TN...Wind Advisory until 3 PM CST this afternoon for TNZ076-096-097. && $$ NEAR TERM...Stumpf SHORT TERM...RSB LONG TERM...30 AVIATION...Stumpf For more information please visit our website at weather.gov/huntsville.