730 FXUS62 KTAE 311048 AFDTAE Area Forecast Discussion National Weather Service Tallahassee FL 648 AM EDT Sat Jul 31 2021 .AVIATION... [Through 12Z Sunday] VFR conditions are expected to prevail through the period. MVFR/IFR conditions may briefly impact the terminals due to fog until around 14z. Otherwise, all terminals have a Prob30 group for afternoon/evening convection. Winds will be light and mainly from the southwest this afternoon. && .PREV DISCUSSION [353 AM EDT]... .NEAR TERM [Through Tonight]... The mid-upper level ridge over our region will begin to break down later today as a broad trough digs down from the north. Low level flow will generally be from the west to southwest which will increase the boundary layer moisture. PW's are forecast to increase by late afternoon to 1.80-2.0" for locations along and near the coast to 1.60-1.80" for our northernmost zones. Therefore, we will see better chances for afternoon/evening convection but likely not before most inland areas reach the mid to upper 90s and lower to mid 90s near the coast. These temperatures combined with dew points in the mid to upper 70s will result in peak heat indices reaching our excessive heat criteria (110-115) across a large portion of our CWA with a heat advisory for our remaining counties. PoPs for today will be in the chance range (30-40%) dropping down to 20-30% for tonight. It will be muggy overnight with lows in the upper 70s to around 80. Sensitive parties should limit outdoor exposure today, and those that are working or playing outdoors should take frequent breaks and hydrate as much as possible. Heat safety tips and resources can be found in the following link: www.weather.gov/safety/heat. .SHORT TERM [Sunday Through Tuesday]... A longwave trough anchored near the Great Lakes will dig south into the Southeast States on Sunday, extending its reach further south on Monday and Tuesday. Upper height falls and larger-scale lift will be most pronounced on Monday, with the forecast area coming under cyclonic flow aloft during this time. At the surface, a slow-moving cold front will sag south through Alabama and Georgia on Monday and Tuesday. Deep-layer SW-W flow south of this front will raise Precipitable Water (PW) values well in excess of 2" starting Sunday. Even against the backdrop of the first 10 days of August climatologically having the moistest PW values of the year, the SPC sounding climatology reveals that forecast values from Sunday through Tuesday will reach 90th percentile values. So given the factors of a richly moist air mass, upper dynamics in the form of subtle shortwaves rounding the base of the eastern U.S. trough, and the additional focus of a front sagging through AL/GA, Monday and Tuesday could be wet, soggy, thundery days, with Sunday marking the transition day into this pattern. Local runoff issues could become an issue, especially if we get training convective cells. Heat index values will still be elevated on Sunday, perhaps exceeding the Heat Advisory criteria of a 108F-degree heat index in places such as the Flint River Valley in Georgia. However, improved mixing (due to cooling temperatures aloft) may cause a modest drop in dewpoints during peak daytime heating. Increasing late afternoon convection will also provide some cooling relief, and an increase in clouds will start to reduce the added effect of sun exposure. These quantitative and qualitative factors throw enough question into the heat forecast for Sunday to make any extension of the Heat Advisory premature at this time. By Monday and Tuesday, the abundance of clouds and convection will readily hold down high temperatures to 90F or less. .LONG TERM [Tuesday Night Through Saturday]... Little change is expected in the wet, thundery pattern on Wednesday. Cyclonic flow aloft in the base of an eastern U.S. upper trough will interact with an extremely moist air mass and a hung-up cold front to our north to keep things wet. The eastern U.S. trough will slowly de-amplify and fill from Thursday through next Saturday. Upper heights will slowly rise over the forecast area, and the subtropical Bermuda ridge axis will start to rebound northward closer to our latitude. PW values will retreat to values closer to normal for early August. So Thursday and Friday will be marked by a drop in rain chances, ending the week closer to normal... by mid-summer rainy season standards. .MARINE... Moderate southwest breezes will prevail over the waters through next Wednesday, as the subtropical ridge axis stays south of the waters across South Florida and the southeast Gulf. Southwest breezes will become fresh at times from Sunday through Tuesday, as a front sags slowly south through Alabama and Georgia. Otherwise, shower and thunderstorm coverage will increase over the waters through Monday and then persist through Wednesday, posing a risk to mariners from locally gusty and erratic winds. .FIRE WEATHER... Minimum relative humidity values are expected to remain high along with chances for widespread wetting rains from Sunday through at least the middle of next week. There are no fire weather concerns at this time. .HYDROLOGY... Heavy rainfall is expected at times from Monday through Wednesday, with locally heavy rainfall perhaps as soon as late Sunday. This will come courtesy of an extremely moist air mass, a cold front sagging in from the north, and cyclonic flow aloft in the base of an eastern U.S. trough. The official forecast shows 4-day QPF of 3-5 inches, heaviest over our Florida counties. Ensemble river forecasts respond with decisive rises on area rivers starting around the middle of next week. Compared with ensemble runs from 24 hours ago, there is a growing number of members at an increasing number of river forecast points which show minor river flooding. In plainer terms, the risk of flooding during the second half of the week ahead is increasing. .SPOTTER INFORMATION STATEMENT... Spotter activation is not requested. However, spotters are always encouraged to safely report significant weather conditions when they occur (while following all local, state, and CDC guidelines) by calling the office or tweeting us @NWSTallahassee. && .PRELIMINARY POINT TEMPS/POPS... Tallahassee 96 77 93 76 89 / 30 20 70 50 90 Panama City 92 80 91 78 88 / 30 30 50 60 80 Dothan 97 77 94 75 88 / 40 20 70 60 90 Albany 99 79 96 76 89 / 40 20 60 50 90 Valdosta 97 76 93 75 88 / 30 20 70 40 90 Cross City 91 78 90 78 89 / 30 20 50 50 80 Apalachicola 90 80 90 78 88 / 30 30 50 60 80 && .TAE WATCHES/WARNINGS/ADVISORIES... FL...Heat Advisory from 11 AM EDT /10 AM CDT/ this morning to 8 PM EDT /7 PM CDT/ this evening for Central Walton-Coastal Dixie-Coastal Taylor-Inland Dixie-Inland Taylor-Lafayette- North Walton-South Walton. Excessive Heat Warning from 11 AM EDT /10 AM CDT/ this morning to 8 PM EDT /7 PM CDT/ this evening for Calhoun-Coastal Bay- Coastal Franklin-Coastal Gulf-Coastal Jefferson-Coastal Wakulla-Gadsden-Holmes-Inland Bay-Inland Franklin-Inland Gulf-Inland Jefferson-Inland Wakulla-Jackson-Leon-Liberty- Madison-Washington. GA...Heat Advisory from 11 AM this morning to 8 PM EDT this evening for Ben Hill-Berrien-Clay-Cook-Irwin-Lanier-Lowndes-Quitman- Randolph-Tift-Turner. Excessive Heat Warning from 11 AM this morning to 8 PM EDT this evening for Baker-Brooks-Calhoun-Colquitt-Decatur-Dougherty- Early-Grady-Lee-Miller-Mitchell-Seminole-Terrell-Thomas- Worth. AL...Heat Advisory from 10 AM this morning to 7 PM CDT this evening for Coffee-Dale-Geneva-Henry. Excessive Heat Warning from 10 AM this morning to 7 PM CDT this evening for Houston. GM...None. && $$ NEAR TERM...Barry SHORT TERM...Haner LONG TERM...Haner AVIATION...Barry MARINE...Haner FIRE WEATHER...Barry HYDROLOGY...Haner