256 FXUS64 KHUN 142303 AFDHUN Area Forecast Discussion National Weather Service Huntsville AL 503 PM CST Sat Dec 14 2019 .UPDATE... For 00Z TAFS. && .NEAR TERM...(Tonight) Issued at 235 PM CST Sat Dec 14 2019 Winds aloft will become more zonal as a weak upper ridge builds in tonight. At the sfc, winds will be variable as high pressure from the Northern Plains extended into the region. Cloudy skies will persist and help keep temps at bay with overnight temps dipping into the upper 30s. Some patchy fog is possible, but with the amount of cloud cover in place tonight, didn't have the confidence at this time to include it in the weather grids. .SHORT TERM...(Sunday through Monday Night) Issued at 235 PM CST Sat Dec 14 2019 The weak ridge and sfc high pressure that started to build in overnight will persist through most of the day. This will give way to dry and seasonable temps with daytime highs reaching the lower 60s. This pattern will quickly come to an end as the an approaching system rounding through the Four Corners will push it eastward Sunday night. Gulf moisture will start to usher into the region as sfc southerly flow and southwesterly flow aloft will set up. A LLJ Sunday night will push PWATs up to 1 inch and will allow for showers to develop then spread across the TN Valley Sunday night. The trough will swing into the Southern Plains on Monday and the associated sfc low will lift NE into the OH Valley. A weak disturbance will lift into the TN Valley late Monday morning ahead of the sfc low and increase the coverage of showers and with the availability of some elevated instability, develop a few thunderstorms too. With good shear already in place, cannot rule out some of these storms becoming strong, especially if storms are able to become discrete. The sfc low will slightly deepen as it lifts NE but will see a southwesterly 40-50kt LLJ push into the region ahead of an approaching cold front. This will increase forcing and the influx moisture even further allowing PWATs to reach 1.5 inches, get dewpoints into the lower 60s and daytime highs to encroach 70 degrees. Forecast soundings continue to show a cap holding into the early afternoon hours. Once this cap erodes, convection will be able to tap into 0-1km shear of ~30kts, and ~60kts of 0-6km shear along with 500-1,000 J/kg of instability. Given a favorable combination of deep-layer/low-level shear and instability, storms could become severe during the afternoon and evening hours on Monday. All modes of severe weather are possible. With flow parallel to the cold front combined with 1-2" of heavy rainfall (with locally higher amounts), minor flooding will be possible. Damaging winds up to 70mph, hail and tornadoes are also possible especially if storms are able to become discrete. The threat for severe weather will continue towards midnight, otherwise precip chances will taper with the passage of the cold front. It's also important to note that breezy conditions will set up across the TN Valley Monday and Monday night. A Wind Advisory may be needed for mainly elevated locations Monday afternoon to evening. Sustained winds generally 10-15kts but 15-20kts in higher elevations with gusts 25-30kts. .LONG TERM...(Tuesday through Friday) Issued at 235 PM CST Sat Dec 14 2019 Much cooler air will filter into the Southeast on Tuesday as the longwave trough axis slides east over the OH and lower MS River Valleys. Cloud cover will linger through much of the day on Tuesday, but will begin to thin after sunset. High temperatures will drop into the 40s on Tuesday, and clear skies will allow for decent radiational cooling that will bring low temperatures down into the mid and upper 20s both Tuesday and Wednesday nights. Despite clear skies on Wednesday, high temperatures will remain in the 40s under light northwesterly flow. The trough axis will clear to our east by late Wednesday, and winds will veer back to southerly on Thursday. Expect this to result in a warming trend through the end of the work week with high temperatures climbing back into the 50s Thursday and Friday. Long term guidance continues to key in on another upper trough/disturbance late next week, but considerable disagreement still exists between models. While we will have to wait for models to come into better agreement before diving into more detail, for now it does not appear that this system will bring us anything more than a few showers so have maintained only slight chance PoPs late Friday. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 502 PM CST Sat Dec 14 2019 Ceilings will remain on the border between MVFR and VFR this evening and overnight. There is a low chance for patchy fog development between 09Z and 13Z, but confidence is too low to include in this TAF. Ceilings will lift to around 3,000-5,000 ft AGL tomorrow morning, but then more southerly winds stream in more moisture and MVFR ceilings tomorrow afternoon. An approaching system will bring southeast winds around 10 kts at the surface and southwest winds near 30 kts at 1500 ft AGL. Any precipitation should hold off until Monday morning. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...NONE. TN...NONE. && $$ NEAR TERM...JMS SHORT TERM...JMS LONG TERM...25 AVIATION...30 For more information please visit our website at weather.gov/huntsville.