750 FXUS62 KJAX 241920 AFDJAX Area Forecast Discussion National Weather Service Jacksonville FL 320 PM EDT Tue Aug 24 2021 .NEAR TERM [Through Tonight]... Late morning surface analysis depicted a rather stagnant weather pattern locally, as Atlantic high pressure (1022 millibars) remains centered near Bermuda and was extending its axis southwestward across the FL peninsula. Meanwhile, a narrow deep- layered trough continues to extend from Henri's remnants from the Canadian Maritime region south-southwestward to the Georgia coastal waters and along the Interstate 10 corridor in northeast FL and the Suwannee Valley. Otherwise, ridges aloft remain centered over eastern Texas and the lower Mississippi Valley and also near Bermuda, while a Tropical Upper Tropospheric Trough (TUTT) was spinning westward beneath this ridge towards the Bahamas. Latest RAP/LAPS analyses indicate that deep tropical moisture remains in place locally, with PWAT values around or above 2 inches region-wide, with rather significant surface-based CAPE values above 3,000 j/kg already in place all along the I-10, while lower values were in place for locations north of Waycross and also across north central FL, where cloud cover was thicker this morning. Scattered convection was already developing late this morning along the trough axis from coastal southeast GA southwestward to the Suwannee Valley, with activity generally moving slowly eastward. Temperatures at 15Z were rising through the mid 80s, except around 80 for locations north of Waycross, where stratus has been slower to thin out. Dewpoints remain in the muggy mid to upper 70s at most locations. The base of the narrow trough aloft will slowly pivot southward across our region this afternoon and evening, resulting in numerous showers and thunderstorms developing almost area-wide through the early evening hours. Latest short-term, high resolution guidance indicates that convection currently developing over southeast GA will increase in coverage as it expands southward, with the Gulf coast sea breeze then pushing activity towards the I-95 corridor in northeast FL later this afternoon through early this evening. Northward moving convective outflows may also generate convection later this afternoon for locations near the Altamaha, Ocmulgee and Alapaha Rivers that are currently more stable due to early morning fog and stratus. Cell mergers and mesoscale boundary collisions may result in pulsing convection through early this evening, with stronger storms capable of producing downburst wind gusts up to 50 mph and frequent lightning strikes. However, localized flooding is likely the primary hazard due to slow moving convection, with urban and typically flood prone low lying areas being the most threatened by tropical and possibly training downpours. Widespread convection and cloud cover should keep highs mostly in the 85-90 degree range, with a few lower 90s possible along the I-75 and I-10 corridors, where sunshine has been more plentiful thus far. Convection may linger through the early to mid evening hours tonight as base of the narrow trough pivots eastward over our adjacent Atlantic waters. Additional shallow convection could also develop along the I-10 corridor during the predawn hours as deep tropical moisture remains in place ahead of the approaching TUTT feature from the southeast. Lows will mostly fall to the low and mid 70s. .SHORT TERM [Wednesday Through Thursday Night]... The aforementioned TUTT will slide north-northwest towards the Florida Big Bend over the next couple days with persistent easterly onshore flow at the lower and mid levels. Forcing will be weak, but between an east coast sea-breeze in the afternoon, the lingering trough across SE GA, there should be at least scattered if not numerous showers and thunderstorms Wednesday from the early afternoon into the evening. A swath of drier air (PWATs around 1.4-1.8 inches) will brush the area Wednesday night and Thursday morning, then those 1.8 to 2.2 inch PWATs will return from southeast to northwest across the area on Thursday afternoon. Scattered to numerous afternoon showers and thunderstorms once again across the area Thursday afternoon, lingering along the coastline through the night Thursday night. .LONG TERM [Friday Through Tuesday]... Persistent south-southeasterly from the low to mid levels will continue for the next several days. There is some model discrepancy in regards to tropical development in the southern Gulf waters that may approach anywhere from south TX to southern LA by the weekend. The further west this feature tracks, the more likely we'll have a drier pattern for the weekend. On the flip side, the further northeast the disturbance track, the more tropical moisture will be on tap for the region. Model trend has been closer to the latter, so leaning towards the wetter pattern continuing through at least Saturday. Deep layer ridging will build over the region early next week, bringing with it subsidence and thus lower chances for storms. && .AVIATION... [Through 18Z Wednesday] IFR visibilities are expected through around 19Z at GNV as slow moving thunderstorms impact the terminal. MVFR conditions will likely prevail at SSI through at least 19Z. Showers and thunderstorms will likely overspread the Duval County terminals and SGJ through the mid to late afternoon hours, and we included TEMPO groups for briefly gusty winds and IFR visibilities during heavier downpours through around 23Z at these terminals. Conditions will likely improve to VFR at SSI and GNV towards 21Z. Activity could linger through the early evening hours at SGJ. Outside of thunderstorm activity, southerly surface winds will remain sustained around 10 knots at the inland terminals through around 23Z, while the Atlantic sea breeze situated just inland from the coastal terminals results in southeasterly surface winds sustained at 10-15 knots at SGJ and SSI. Southerly surface winds will then decrease to around 5 knots or less at the inland terminals after 01Z, with sustained speeds remaining at 5-10 knots overnight at the coastal terminals. Periods of MVFR to IFR visibilities will be possible overnight at VQQ and possibly GNV. && .MARINE... Southerly winds today will shift to become more southeasterly and then easterly the next few days as an inverted trough drifts westward, nudging the Bermuda high to the north and west. This onshore flow will keep scattered to numerous showers and thunderstorms in the forecast for the next several days. When the trough makes its closest approach to our offshore waters Wednesday and Thursday, offshore winds will increase to around 15 knots, possibly 15 to 20 knots and seas will increase to around 5 to 7 feet. Rip Currents: Low risk of rip currents today and Wednesday, increasing Thursday and Friday. && .FIRE WEATHER... Scattered to numerous showers and thunderstorms the next several days, with heavy rainfall possible each afternoon. Gusty winds and localized flooding will be the main concern for storms. This wet pattern, along with light winds in place, will prevent us from reaching red flag criteria for the next several days. && .HYDROLOGY... Minor river flooding will continue along upper portions of the Suwannee, along lower portions of the Santa Fe and also for the lower Suwannee River south of the confluence with the Santa Fe through at least late this week, as most river gauges are slowly falling or nearly steady. Widespread 1 to 3 inches of rain is expected to accumulate over the area over the next few days, with isolated totals closer to 3 to 5 inches. The highest accumulations are generally anticipated along the I-95 corridor. This could lead to localized flooding. && .PRELIMINARY POINT TEMPS/POPS... AMG 71 87 72 87 71 / 40 50 20 30 20 SSI 76 87 78 87 77 / 60 70 20 50 50 JAX 73 89 75 88 75 / 40 40 20 60 50 SGJ 74 88 77 86 75 / 40 30 30 70 50 GNV 72 89 73 88 73 / 40 40 20 60 20 OCF 73 90 73 88 73 / 50 40 20 70 20 && .JAX WATCHES/WARNINGS/ADVISORIES... FL...None. GA...None. AM...None. &&