FXUS62 KJAX 200202 AFDJAX Area Forecast Discussion National Weather Service Jacksonville FL 1002 PM EDT Sat Jul 19 2025 ...HEAT ADVISORY AREA-WIDE ON SUNDAY... ...DANGEROUS COMBINATION ON HEAT AND HUMIDITY CONTINUES MON... ...THUNDERSTORM COVERAGE INCREASES BEGINNING MON AFTERNOON... For the latest NE FL and SE GA Daily Key Messages please visit: https://www.weather.gov/media/jax/briefings/nws-jax-briefing.pdf .UPDATE... Issued at 1001 PM EDT Sat Jul 19 2025 Late evening surface analysis depicts weakening high pressure (1021 millibars) stretching across our region. Aloft...deep- layered ridging continues to slowly retrograde westward and was now centered over the FL Big Bend region and the eastern Gulf. Latest GOES-East derived Total Precipitable Water imagery indicates that pockets of drier air were advecting into our region, with PWATS of 1.6 - 1.8 inches along the I-10 corridor and southeast GA, while deeper moisture prevails to the south of Gainesville in north central FL, where values were closer to 2 inches. Convection that developed over southern portions of the St. Johns River basin and along the I-95 corridor in northeast FL have dissipated, with mid and high altitude debris cloudiness quickly thinning out and shifting west of our region. Temperatures at 02Z were generally in the low to mid 80s, with dewpoints mostly in the 70s across our area. Fair skies and warm temperatures will continue overnight as light southerly low level flow veers to west-southwesterly after midnight. Lows will only fall to the mid and upper 70s inland, ranging to around 80 at coastal locations. These values may challenge record warm minimum temperatures for July 20th (see Climate Section below for details). A Heat Advisory has been issued area-wide for Sunday from 11 AM through 7 PM. Highs will soar to the 95-100 degree range, with maximum heat index values reaching the dangerous 108-112 range by the early to mid afternoon hours. && .SHORT TERM... (Sunday through Monday night) Issued at 134 PM EDT Sat Jul 19 2025 Sunday, low/mid level ridging will be over the NE to north central Gulf waters to our west and southwest. Drier than average airmass (PWATs about 1.5 to 1.75 inches close to the 25th percentile for drier air) and subsidence under the ridge will limit chances for showers for most of the area to under 10 percent. A bit more moisture across north central FL and to the north over the Altamaha river basin will allow for up to a 20 percent chance of T'storms in the afternoon. For Monday, the low/mid level ridge will shift onto the central Gulf coast as the trough, initially positioned along the Southeast US coast, sinks into the area through the day. Aloft the low and mid level flow will turn northwesterly. Additional moisture (PWATs climbing to 2.0-2.25 inches (90th percentile this time of year) will pool into the area along and ahead of the trough axis as it moves southward. The combination of lift along the trough, higher moisture, and shortwave energy arriving from around the periphery of the ridge to the west will produce scattered to numerous showers and T'storms across NE FL as the Gulf seabreeze moves inland and near the coast where the Atlantic seabreeze stays pinned as light west to southwest flow prevails. Hot temperatures are expected each day with highs Sunday reaching near the century mark from Jacksonville westward along and north of I-10 and into the upper 90s for most areas on Monday. Heat index values from the hot temperatures will also combine with dewpoints in the mid 70s to create heat index values 106-112 degrees across much of the area, except for areas north and west of Waycross. Therefore, heat advisories are likely for a majority of NE FL and along into the SE GA coast the next couple of days. && .LONG TERM... (Tuesday through next Saturday) Issued at 134 PM EDT Sat Jul 19 2025 Next week, the low/mid level ridge will slide westward into the north central Gulf as a trough/weak frontal boundary settles southward along the Southeast U.S. coast towards the area. Tuesday and Wednesday, the front will slide into the area with PWATs reaching near daily max values (above 2.3-2.4 inches). The combination of very high moisture, lift from the front, shortwave energy aloft with a mid/upper trough moving SE off the eastern seaboard will promote widespread showers and T'storms over our area each day. The mid level temps will stay near to slightly warmer than climatology (about -5 to -7 Celsius), so the potential for strong gusty downburst winds will remain given steep low level lapse in the afternoon where seabreeze and storm outflow collisions occur, especially Tuesday before more persistent east to northeast winds arrive into Wednesday as high pressure ridge axis builds down the east coast. The front will be stalled over the area on Wednesday with the flow from the east northeast promoting convergent onshore flow that will help enhance bands of showers moving onto the coast with locally heavy rainfall possible from heavy downpours. The Weather Prediction Center has a marginal risk of rainfall for Tuesday and Wednesday as the front arrives. Thursday into Friday, the front will begin to weaken with some drier air working in from the north into SE GA as weak high pressure extends from near coastal New England into the Carolinas and then shift off the SC/NC coast. This will slightly limit chances to scattered to numerous T'storms over SE GA by Friday with numerous coverage over NE FL as the front becomes more diffuse and high moisture remains over our area. Temperatures will begin the period above normal as highs remain in the mid to upper 90s away from the coast with high heat index values potentially into heat advisory levels Tuesday before highs trend back to near to slightly above normal Wednesday through Friday. && .AVIATION... (00Z TAFS) Issued at 800 PM EDT Sat Jul 19 2025 An isolated shower may develop early this evening near the GNV terminal as the Atlantic sea breeze boundary pushes westward across the area. However, confidence was too low to include in the evening TAFs. Otherwise, VFR conditions will prevail at the regional terminals through at least 07Z. Periods of IFR visibilities are expected overnight at VQQ. Isolated showers and thunderstorms may develop near SGJ and CRG during the early to mid afternoon hours on Sunday as the Atlantic sea breeze moves slowly inland from the coast. Confidence was too low to mention anything other than vicinity shower coverage after 18Z. Showers and thunderstorms may otherwise approach the SSI terminal from the north and northwest towards 00Z Monday, and this possibility will be addressed in future TAF issuances. Southerly surface winds of 5-10 knots this evening will shift to west-southwesterly after 05Z, with speeds diminishing inland and remaining sustained around 5 knots at the SSI and SGJ coastal terminals. Westerly surface winds of 5-10 knots will develop at the regional terminals by 14Z. Surface winds will shift to east-southeasterly around 10 knots at SGJ and southerly around 10 knots at SSI towards 18Z as the Atlantic sea breeze moves slowly westward across the coastal terminals. && .MARINE... Issued at 1001 PM EDT Sat Jul 19 2025 High pressure centered over our local waters this evening will shift westward on Sunday as troughing develops over the southeastern states. Showers and thunderstorms may develop on Sunday evening and night, especially over the Georgia waters. Troughing along the southeastern seaboard will continue to sharpen early in the upcoming week, resulting in increasing chances for showers and thunderstorms across our local waters. Strong to isolated severe thunderstorms will be also possible through midweek. Seas of 2 to 3 feet will prevail both near shore and offshore through Tuesday. Weak low pressure may develop near our local waters towards midweek as high pressure over New England wedges down the southeastern seaboard, creating a brief increase in northeasterly winds through Wednesday evening. A northeasterly swell may also build seas to Caution levels of 4 to 6 feet offshore later in the upcoming week, with 3 to 5 foot seas possible near shore. Low pressure will then shift to the west of our local waters by Wednesday night and Thursday, allowing surface winds to shift to southeasterly and then southerly by late in the week. Rip Currents: Developing onshore winds on Sunday afternoon will combine with a persistent easterly ocean swell to create a lower end moderate rip current risk at all area beaches. Similar conditions are expected on Monday. && .FIRE WEATHER... Issued at 1001 PM EDT Sat Jul 19 2025 Westerly surface and transport winds will develop towards sunrise on Sunday, with breezy transport speeds combining with elevated mixing heights to create high daytime dispersion values for inland locations along and north of Interstate 10. Good values will prevail elsewhere inland, except fair values across north central FL, where lighter transport speeds are forecast. Onshore surface winds developing at coastal locations during the afternoon hours will also result in fair daytime dispersion values. Similar conditions will prevail on Monday, with surface and transport winds shifting slightly to west-northwesterly. Northwesterly transport winds will then weaken on Tuesday, with elevated mixing heights for locations from Waycross northward keeping daytime dispersion values good, while fair values generally prevail elsewhere. Coverage of showers and thunderstorms will increase on Monday and especially Tuesday and Wednesday, with strong to isolated severe thunderstorms possible each day. && .CLIMATE... Issued at 1001 PM EDT Sat Jul 19 2025 Daily record high temperatures at our designated climate sites through Tuesday, July 22 Sunday Monday Tuesday ----------------------------- Jacksonville 103/2000 102/1942 101/1942 Gainesville 100/1942 102/1942 99/1907 Alma, GA 104/2000 102/1942 100/1942 Craig Airport 100/2000 98/2015 99/1977 Daily record high minimums at our designated climate sites through Tuesday, July 22 Sunday Monday Tuesday ---------------------------- Jacksonville 80/1872 81/1942 81/1872 Gainesville 77/2018 78/1894 77/2015 Alma, GA 79/1986 78/2015 76/2021 Craig Airport 79/2023 81/2023 78/2025 && .PRELIMINARY POINT TEMPS/POPS... AMG 77 100 78 98 / 10 20 10 40 SSI 80 96 80 95 / 10 20 30 40 JAX 77 100 78 98 / 10 10 20 60 SGJ 79 96 79 95 / 10 10 20 50 GNV 75 99 76 97 / 10 0 10 60 OCF 75 96 75 95 / 10 10 10 50 && .JAX WATCHES/WARNINGS/ADVISORIES... FL...Heat Advisory from 11 AM to 7 PM EDT Sunday for FLZ021-023-024- 030-031-035-038-120-124-125-132-136>138-140-220-225-232-233- 236-237-240-322-325-333-340-422-425-433-522-533-633. GA...Heat Advisory from 11 AM to 7 PM EDT Sunday for GAZ132>136-149- 151>154-162-163-165-166-250-264-350-364. AM...None. && $$