686 FXUS62 KTAE 090354 AFDTAE Area Forecast Discussion National Weather Service Tallahassee FL 1054 PM EST Mon Jan 8 2024 ...New MESOSCALE UPDATE, MARINE, HYDROLOGY... .MESOSCALE UPDATE FOR A POTENTIALLY SIGNIFICANT SEVERE WEATHER EVENT OVERNIGHT THROUGH TUESDAY... Issued at 1021 PM EST Mon Jan 82024 Late-evening GOES 1-min satellite imagery shows a deepening surface low over LA strongly forced by its parent upper low evident near the ArkLaTex region. Immediately ahead of this feature is an extensive area of robust convection spreading into the MS Valley. To its south is a warm front nearing the East- Central Gulf Coast with a trailing cold front stretching along coastal TX. A tight pressure gradient is contributing to a potent southerly LLJ up to around 60 kts, per latest SPC mesoanalysis. Such an intense wind field is allowing for very robust inland moisture advection off the Gulf, which will steadily juice up the airmass for severe thunderstorms. Latest hi-res guidance such as the RAP shows a tongue of MLCAPE of 500-1500 J/kg translating east towards the the western FL Panhandle and southern AL overnight. That amount of instability overlapping a highly sheared environment spells trouble. Radar shows a squall line taking shape north of New Orleans and widely scattered showers & thunderstorms downstream of it. Much of this activity is poised to consolidate into a more potent QLCS while moving eastward overnight. We will have to closely monitor discrete to semi-discrete cells ahead of the line for rotation, as some are likely to acquire supercell characteristics and pose a nocturnal tornado threat. For these reasons, in coordination with SPC, a Tornado Watch was issued through 12Z for our SE AL and the FL Panhandle counties. Strong tornadoes are possible, so please ensure you have a way to be awoken by any warnings issued. Elsewhere expect mostly rain showers with some embedded thunder, though winds are expected to start really picking up after midnight. A 6Z balloon launch is forthcoming to sample the atmosphere. && .SYNOPSIS... Issued at 355 PM EST Mon Jan 8 2024 A significant weather event is still expected tonight into Tuesday across the area with multiple hazards. Key Messages below: 1. Strong to severe storms will begin late tonight in the form of isolated supercells, followed by an intense squall line during the day Tuesday. Damaging to destructive winds, tornadoes (some strong), and hail are all possible threats. 2. Heavy rainfall is also expected with this system tonight and Tuesday. Some flooding is possible, as well as rises to near flood stage on some area rivers. 3. Very strong non-thunderstorm gradient winds are expected with this system. Wind gusts of 40-55 mph are possible across the area on Tuesday. Given wet soils, this could result in trees falling more easily. Even higher wind gusts approaching 60 mph are expected along the coast from Wakulla county westward to Walton County. 4. Extremely dangerous beach and boating conditions are expected. Gales and storm-force wind gusts are expected tonight and Tuesday. Very high surf and deadly rip currents are expected. 5. Minor to moderate coastal flooding is expected on Tuesday, most likely along the shores of Apalachee Bay. && .NEAR TERM... (Through Tuesday) Issued at 355 PM EST Mon Jan 8 2024 Overall, there is little change to the previous forecast. A high-impact weather event will affect the region tonight and Tuesday. Multiple hazards are expected, including a significant outbreak of severe thunderstorms. Stay weather aware over the next 24 hours. A deepening low pressure center will turn northeast across the Mid- Mississippi Valley tonight. A large field of intense pressure gradients and wind will engulf the trailing cold front, which will quickly sweep east across our region on Tuesday. In advance of the front, an extremely strong 65-80 knot southerly low-level jet will develop tonight to our west, then translate east across the area during the course of Tuesday morning. Strong, damaging gradient winds are expected by late tonight into Tuesday, with inland wind gusts around 50 mph. Along the beaches gusts of 55 to 60 mph are forecast. The low-level jet will push a warm front northward this evening, leading a rapid influx of maritime tropical air, with surface temperatures and dewpoints rising during the night. The air mass will become weakly to moderately unstable, which is bad news in light of extreme kinematics. With the warm sector late tonight, discrete supercells could move in from the Gulf across the Panhandle, possibly reaching southeast Alabama. Any of these discrete supercells could produce a strong tornado, particularly where the air mass is most unstable and least inhibited at the coast. Then the cold front will blast through during the day on Tuesday, accompanied by a solid squall line that could bring widespread severe convective wind gusts. A few embedded tornadoes will likely accompany the line, and these could also be strong. The latest SPC outlook maintains the Enhanced Risk area (Level 3 of 5) over our entire area. The squall line should exit east of I-75 and east of the Suwannee during the late afternoon. && .SHORT TERM... (Tuesday night through Friday night) Issued at 355 PM EST Mon Jan 8 2024 In the wake of the squall line, improving weather Tuesday night, with breezy conditions as west winds gust around 20 mph. A dry period of weather with light winds is expected on Wednesday and Thursday for any post storm clean-up efforts. A couple of chilly nights are on tap with lows ranging from the low 30s northwest to low 40s southeast on both Tuesday and Wednesday nights, which is a concern for those that may be without power due to Tuesday's severe weather. The wind chill/apparent temps Tuesday night will make it feel like the mid 20s northwest to mid 30s southeast. The next system takes aim at the region on Friday, with increasing clouds in advance expected on Thursday. SPC already has much of the region in a day 5 (Friday) 15% probability for severe weather, which is equivalent to a slight risk in the day 1-3 time frame. Mid-level shortwave is modeled to go negatively tilted as it swings through the TN Valley, placing the strongest forcing for ascent northwest of the region. The wind field may be more unidirectional, but strong nonetheless, with deep layer bulk shear approaching 70 kts and a low-level jet over 50 knots. This will be more than sufficient to advect a warm and unstable air mass northward, with ensemble mean CAPE around 500 J/kg. This supports the potential for another severe weather event with damaging winds and a risk of tornadoes centered on Friday. && .LONG TERM... (Saturday through Monday) Issued at 355 PM EST Mon Jan 8 2024 In the wake of Friday's storm system, cyclonic flow aloft pulls away from the region on Saturday, with zonal flow through early next week. No major impactful weather expected at this time. && .AVIATION... (00Z TAFS) Issued at 648 PM EST Mon Jan 8 2024 Gusty winds, low cigs, and LLWS remain the primary concerns tonight. Thunder is kept at ECP/DHN given evening radar trends showing elevated convection. The main update to the 0Z TAF cycle was introducing TEMPO groups of +TSRA at all terminals for the severe squall line plowing thru the region tmrw. Latest HRRR narrows down timing: 13-15Z ECP/DHN, 14-16Z TLH/ABY, and 16-18Z VLD. Gusts of 45+ kts are likely. Improving wx from W-to-E in the line's wake, but gusty winds linger. && .MARINE... Issued at 1021 PM EST Mon Jan 8 2024 The Orange Beach Buoy (42012) was reporting sustained SE winds of 25 kts with gusts near gale force and 11-ft seas late this evening while Buoy 42036 was reporting similar conditions. From the CWF Synopsis...A very deep low pressure center will continue crossing the Mid- Mississippi Valley late tonight, and a trailing cold front and pre-frontal convection will cross the northeast Gulf waters on Tuesday. Conditions deteriorate further as the pressure gradient tightens more, culminating in frequent storm- force gusts in the southerlies preceding the front. Westerly gales will kick in behind the front, lasting into early Tuesday night. In addition, a squall line of severe thunderstorms with tornadic waterspouts will cross the waters on Tuesday. Conditions will gradually improve on Wednesday, and a high pressure center will quickly pass across the waters on Wednesday night. Southeast breezes will freshen in advance of the next storm system on Thursday and especially Friday, with a period of gale- force wind gusts possible. && .FIRE WEATHER... Issued at 355 PM EST Mon Jan 8 2024 Heavy wetting rains are expected tonight through Tuesday as a strong storm system moves through the region. In particular, a line of severe thunderstorms is expected to sweep through the entire region on Tuesday from the early morning into the early afternoon with the potential for large hail, several tornadoes, and wind gusts up to 80 mph. Ahead of this line, a period of strong winds is expected with wind gusts around 40 to 50 mph inland and 50 to 60 mph closer to the coast. Looking ahead, dry weather is forecast on Wednesday and Thursday, with a potential for low dispersions on Thursday across much of the region. && .HYDROLOGY... Issued at 1021 PM EST Mon Jan 8 2024 River forecast evening update: A Flood Warning is now in effect for the Choctawhatchee River - Newton, which is now forecast to reach minor flood stage Tuesday afternoon, then crest by Wednesday morning. The Pea River - Ariton is also forecast to minor flood stage, but given that significant rainfall has not occurred yet and that the stage change is just outside of 24 hrs, we decided to hold off on issuing a warning and wait more cycle. An incredible synoptic setup with a very dynamic system is expected to begin impacting the region this evening through Tuesday. Overall, rainfall amounts have increased slightly in the western half of the region, owing to an initial widespread stratiform rain event, then turning convective prior to the arrival of a squall line. As a result, this is why rainfall amounts mainly west of the ACF basin have trended upward. Fortunately, this area has received less rainfall than other portions of our forecast area, so while 3-6 inches of rain does present a localized flash flood threat and will lead to noteworthy rises on the Choc/Pea system in South Alabama, a significant flash flood threat does not appear likely, thus no flood watch is needed. The squall line will deliver a very quick 1-2 inches, but its fast progression will limit any flash flood concerns, even in the eastern portions of the forecast area that are much more saturated. Even so, we'll still see modest rises on our mainstem rivers. So while riverine and flash flood impacts are minor, the more pressing concern is the coastal flood impacts. While timing of the onshore winds is important, the magnitude and duration of the winds combined with attendant winds from the squall line set up a scenario where moderate flooding is likely in Apalachee Bay, especially east of Carrabelle. It's east of Carrabelle where the synoptic scale winds of 40-50 mph with higher gusts will pile water into the bay ahead of the squall line. Even if the squall line arrives around 16z, 2 hours prior to high tide, the additional influence of the squall line will push water levels to warning criteria from Carrabelle eastward. Unfortunately, the squall line timing and environmental winds are forecast to peak as they near the Taylor/Dixie County coast around 18z, which is when high tide occurs. Both deterministic and ensemble guidance suggest at least 2- 4 feet AGL with isolated pockets of inundation as much as 5 feet. While this is on the high side of the guidance, the environmental winds are well beyond 90th percentile, so favoring the higher end guidance seems appropriate here. Thus a coastal flood warning was issued for Franklin County eastward. A coastal flood advisory was issued for the Panhandle counties to account for the strong winds leading to minor flooding there. We'll watch the next system on Friday for additional rains and see how it will undoubtedly impact our river systems into the coming weekend. && .SPOTTER INFORMATION STATEMENT... Spotter activation is requested. Spotters should safely report significant weather conditions and/or damage by calling the office or tweeting us @NWSTallahassee. && .PRELIMINARY POINT TEMPS/POPS... Tallahassee 54 68 38 56 / 90 100 10 0 Panama City 56 66 40 55 / 90 100 0 0 Dothan 51 64 34 52 / 100 100 0 0 Albany 53 66 36 52 / 100 100 10 0 Valdosta 55 70 38 54 / 90 100 20 0 Cross City 59 72 42 58 / 40 100 40 0 Apalachicola 60 67 42 56 / 80 100 0 0 && .TAE WATCHES/WARNINGS/ADVISORIES... FL...Wind Advisory until noon CST Tuesday for FLZ007>010. Wind Advisory until 5 PM EST /4 PM CST/ Tuesday for FLZ011>017- 026-027-118. Wind Advisory from 4 AM to 5 PM EST Tuesday for FLZ018-019-028- 029-034. High Rip Current Risk through late Wednesday night for FLZ108- 112-114-115. High Wind Warning until 1 PM EST /noon CST/ Tuesday for FLZ108- 112-114-115-127. High Surf Warning until 11 AM EST /10 AM CST/ Wednesday for FLZ108-112-114. Coastal Flood Advisory until 1 AM EST /midnight CST/ Wednesday for FLZ108-112-114. High Surf Advisory until 10 PM EST Tuesday for FLZ115. Coastal Flood Warning from 7 AM Tuesday to 1 AM EST Wednesday for FLZ115-118-127. Wind Advisory until midnight EST Tuesday night for FLZ128-134. Coastal Flood Warning from 7 AM Tuesday to 7 AM EST Wednesday for FLZ128-134. GA...Wind Advisory until 1 PM EST Tuesday for GAZ120. Wind Advisory until 5 PM EST Tuesday for GAZ121>131-142>146- 155>158. Wind Advisory from 4 AM to 5 PM EST Tuesday for GAZ147-148- 159>161. AL...Wind Advisory until noon CST Tuesday for ALZ065>069. GM...Gale Warning until midnight EST Tuesday night for GMZ730-765. Storm Warning until 1 PM EST /noon CST/ Tuesday for GMZ750-752- 755-770-772-775. && $$ MESOSCALE UPDATE...IG3 NEAR TERM...DVD SHORT TERM...LF LONG TERM....LF AVIATION...IG3 MARINE...LF/IG3 FIRE WEATHER...LF HYDROLOGY...Godsey/IG3