Area Forecast Discussion
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Issued by NWS
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159 FXUS62 KTAE 271501 AFDTAE Area Forecast Discussion National Weather Service Tallahassee FL 1101 AM EDT Mon May 27 2024 ...New UPDATE... .UPDATE... Issued at 1056 AM EDT Mon May 27 2024 Our 12z sounding this morning showed a rather impressive elevated mixed layer (EML) with mid-level lapse rates in excess of 8 C/km, which is very impressive for this part of the country. However, there is a good bit of dry air in the mid and low levels as well as a capping inversion around 800 mb. This makes sense as farther south, the influence of the ridge is still present. However, an approaching shortwave and diurnal heating could erode any inversion farther north. We still expect that we`ll be plenty unstable with about 30-35 kt deep layer shear and 850-1100 J/kg of DCAPE. The question remains how much forcing will we have. If we have less forcing, there may be fewer storms overall, and more forcing means greater coverage of storms. Regardless, any storms that do develop in this environment will be capable of becoming strong to severe with damaging winds and large hail being the primary severe concerns. Frequent lightning will accompany all storms today. Rain chances were tweaked, mainly in the Florida Panhandle later this afternoon and evening where the hi-res guidance suggests that storms may eventually move into. Storm motion today will generally be east to southeast. High temperatures were also nudged upward a bit, mainly in the southern and eastern parts of the area where a bit more sunshine is starting to break through. && .NEAR TERM... (Today and tonight) Issued at 426 AM EDT Mon May 27 2024 Overall, another warm to hot afternoon is expected with temperatures pushing into the upper 80s to lower 90s for much of the area. The concern with today`s forecast is the potential for strong to severe thunderstorms later this morning and into the afternoon and evening. The Storm Prediction Center has maintained a Slight Risk (level 2 of 5) for severe weather from a line that extends from northern Walton County northeastward through Tifton and a Marginal Risk (level 1 of 5) from just north of Panama City through Tallahassee and just south of Valdosta. Any storms that move through later this morning and into the afternoon and/or are able to develop later today will have the potential of producing damaging wind gusts and large hail. Today`s thunderstorm potential is highly conditional on what happens upstream of the region early this morning. Most Convection Allowing Models (CAMs) are in decent agreement on the Mesoscale Convective System (MCS) continuing to dive southeast through Mississippi and Alabama this morning. However, they begin to differ on just how far south the MCS can make it and whether any storms can develop in its wake. If the MCS holds together through the morning, it is forecast to arrive in our southeastern Alabama counties as early as 10-11AM CDT before pushing southeast into the rest of the area in the afternoon. This is during peak heating hours, so there will be plenty of energy available for these storms to continue. One limiting factor is the fact the bulk of the upper-level support is expected to remain north of our area. Still, forecast soundings show 2,000 to 3,000 J/kg surface based CAPE along with Downdraft CAPE (DCAPE) between 1,000 to 1,500 J/kg. Values that high coupled with some mid-level dry air support the possibility of damaging wind gusts. Mid-level lapse rates will generally be between 7 to 7.5 C/km, which will support the potential for large hail within any of the stronger storms. Later tonight, a weak cold front is forecast to push through most of the region outside of the southeast Florida Big Bend. Temperatures won`t fall a whole lot tonight, generally in the upper 60s to lower 70s, as the drier air will take a while longer to push into the region. && .SHORT TERM... (Tuesday through Wednesday night) Issued at 426 AM EDT Mon May 27 2024 In the wake of the weak late season cold frontal passage late Monday night, a drier air mass will trickle in across the region on Tuesday. Precipitable Water (PW) values will dry out well below 1.5 inches, which will suppress attempts at afternoon convection. Am suspicious of the NBM`s dry forecast for Wednesday and Wednesday night. Most guidance increases PW values on Wednesday, albeit holding them a little below 1.5 inches. However, we will be under cyclonic 500 mb flow, and some guidance members are painting a shortwave rippling across the region on Wednesday. Perhaps this will manifest itself as a leftover MCV from an earlier thunderstorm complex well off to the west. Seabreeze boundaries will also spread inland in the afternoon. This should present a few ways to focus convection, if we can get enough moisture. While most GEFS ensemble members are dry on Wednesday, there are a few that produce moderate instability and respectable QPF. Have therefore at least included slight chance PoPs, which is supported by GFS- and NAM-based MOS guidance values along and west of the Flint River. && .LONG TERM... (Thursday through Sunday) Issued at 426 AM EDT Mon May 27 2024 Beyond Wed night through next weekend, the forecast area will lie near a substantial north-south moisture gradient, with drier air to the north and moister air to the south. This comes as surface high pressure will move from the Ohio Valley on Friday night off the U.S. Mid- Atlantic coast by Sunday. This will cause our low- level flow to clock around more easterly and perhaps southeasterly over the course of next weekend. Given our proximity to the moisture gradient, small differences in its north-south position have caused GEFS ensemble members to show a large range of possible PW values, ranging from very moist to very dry. Looking at trends in guidance for different runs over the last couple days, there may be a trend toward less and less drying the air mass late this week and next weekend. While the GEFS ensemble means keep PW values in the drier 1.3 to 1.4 inch range late this week and next weekend, there is a large number of ensemble members up in the 1.5 to 1.8 inch range. Given the seabreeze to focus convection in the presence of enough moisture and instability, the latest forecast has slightly nudged up PoP more squarely into the 20-30 percent range heading into next weekend. && .AVIATION... (12Z TAFS) Issued at 636 AM EDT Mon May 27 2024 Batches of clouds have develop over KDHN, KABY, and KVLD and are leading to IFR to VLIFR conditions for our northern TAF sites. Meanwhile, low stratus is attempting to move over KTLH and KECP, so kept MVFR to IFR in the TAFs another couple of hours to account for that potential. Beyond mid-morning, confidence goes down in the TAFs a bit due to some uncertainty with regards to showers and thunderstorms heading south through Alabama this morning. As of now, have refined the timing of VCTS a bit, but confidence remains low to medium at this time. Any storms this afternoon will be capable of producing damaging winds and hail. Additional showers and scattered thunderstorms are possible into the early evening hours. Drier air begins to filter in late tonight and should lead to VFR conditions late Monday night into Tuesday morning. That said, there is a non-zero chance of some fog formation at the TAF sites, especially KVLD, early Tuesday morning. Winds will generally be out of the southwest most of the TAF period with occasional gusts up to 20 knots possible. && .MARINE... Issued at 426 AM EDT Mon May 27 2024 Moderate southwest breezes will prevail through this evening, in advance of a weak cold front that will enter the waters early Tuesday morning. Westerly breezes will prevail behind the front on Tuesday, before gradually clocking around northerly by late Tuesday night. Though general northerly winds will continue through Wednesday night, nearshore seabreeze effects will be at play in the afternoon hours. The southern periphery of high pressure will bridge down the Southeast Atlantic coast on Friday night, bringing a marked turn and increase in easterly flow. && .FIRE WEATHER... Issued at 426 AM EDT Mon May 27 2024 Good dispersions are forecast this afternoon along and east of the Flint and Apalachicola Rivers. Scattered showers and thunderstorms are possible, mainly in Alabama and Georgia, this afternoon and could produce strong, erratic wind gusts and frequent lightning. A weak cold front arrives tonight and will lead to drier conditions Tuesday and Wednesday afternoons with MinRH values generally between 30 to 40 percent each afternoon. Dispersions will be high for much of the region Tuesday and Wednesday. && .HYDROLOGY... Issued at 426 AM EDT Mon May 27 2024 New flooding along the Suwannee River is possible this week, as last weeks floodwaters on the Withlacoochee slowly route downstream through the Suwannee. However, 7-day river forecasts for the Suwannee have been gradually been trending down with the respective crests from Branford down to Manatee Springs. Though minor flooding is still the forecast a few days from now, this seems to become less certain with each forecast update. Otherwise, rainfall in the week ahead is unlikely to cause flooding issues. Thunderstorms later today have potential to dump a quick 1-3 inches in heavier pockets, which would merely cause short- duration runoff issues. Additional rainfall through next weekend is forecast to be hydrologically insignificant. && .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 92 74 94 70 / 30 30 10 10 Panama City 89 76 92 72 / 20 20 10 0 Dothan 89 70 92 68 / 60 40 0 0 Albany 90 71 92 67 / 60 50 0 0 Valdosta 93 72 93 68 / 30 50 10 0 Cross City 89 73 93 69 / 10 20 30 10 Apalachicola 86 76 89 74 / 10 20 10 0 && .TAE WATCHES/WARNINGS/ADVISORIES... FL...High Rip Current Risk through late tonight for FLZ108-112-114. GA...None. AL...None. GM...None. && $$ NEAR TERM...Reese SHORT TERM...Haner LONG TERM....Haner AVIATION...Reese MARINE...Haner FIRE WEATHER...Reese HYDROLOGY...Haner