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Area Forecast Discussion
Issued by NWS Jacksonville, FL
Issued by NWS Jacksonville, FL
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113 FXUS62 KJAX 121152 AFDJAX Area Forecast Discussion National Weather Service Jacksonville FL 752 AM EDT Mon Aug 12 2024 ...New AVIATION... .SYNOPSIS... Issued at 420 AM EDT Mon Aug 12 2024 Early morning surface analysis depicts a stationary trough that stretches from the coastal Carolinas southwestward across the Deep South and along the northern Gulf coast. Meanwhile, weakening high pressure (1020 millibars) blankets the Ohio, Tennessee, and lower Mississippi Valleys in the wake of this surface trough. Aloft...weak flow persists locally between Atlantic ridging that was building westward across the Bahamas and another ridge centered over Texas that was nosing eastward along the Interstate 10 corridor. Otherwise, troughing was digging southward from Quebec through New England and eastern portions of the Great Lakes. Latest GOES-East derived Total Precipitable Water imagery indicates that a moisture gradient persists along the surface trough axis across inland southeast GA, where PWATs have fallen to near 1.5 inches along the Altamaha and Ocmulgee Rivers. Meanwhile, deeper moisture persists for locations south and east of Waycross, where PWATs were around or above 2 inches. Cirrostratus debris cloudiness from late evening convection over coastal southeast GA has been slow to thin as it drifts southward across northeast and north central FL, while fair skies now prevail for ideal viewing of the peak of the Perseid meteor shower across southeast GA during the predawn hours. Overnight convection generated by low level west southwesterly flow has remained confined to the FL Big Bend and Nature coasts thus far, with only a few light showers occasionally approaching southern portions of the Suwannee River basin. Temperatures and dewpoints were in the 70s at inland locations as of 08Z, ranging to around 80 at coastal locations. && .NEAR TERM... (Today and Tonight) Issued at 420 AM EDT Mon Aug 12 2024 Debris cloud cover should continue to gradually thin out through sunrise across northeast and north central FL, while patchy fog may develop around sunrise for locations near the Altamaha and Ocmulgee Rivers that are beneath the drier and more subsident air mass. Any fog or lower stratus clouds that manage to develop will quickly dissipate during the early morning hours, with a healthy cumulus field expected to be generated during the mid to late morning hours, especially for locations within the moist air mass to the south and east of Waycross. Meanwhile, low-topped convection developing within the low level west southwesterly flow pattern along the FL Big Bend and Nature coasts may begin to move across the Suwannee River and also into north central FL by the mid to late morning hours. Heat index values will begin to approach advisory criteria before noon for locations south and east of Waycross, where dewpoints will remain in the mid to upper 70s for most of the day today. Temperatures will soar to the low and mid 90s this afternoon, with a few upper 90s possible for inland locations along and north of the Interstate 10 corridor. Dewpoints for locations north and west of a line from Homerville to Waycross to Jesup will fall to the upper 60s and lower 70s this afternoon, keeping heat index values closer to 100. A Heat Advisory is again in effect today elsewhere for maximum heat index values of 108-112 degrees. The moisture gradient in place across our area should keep afternoon convection isolated to widely scattered at best for most of inland southeast GA, with west-southwesterly low level flow keeping afternoon and evening convection focused along the I-95 corridor in coastal southeast GA. Early afternoon convection is expected to increase in coverage along the I-75 corridor in the Suwannee Valley and north central FL as it progresses east- northeastward along the Gulf coast sea breeze. This activity should then collide with a pinned Atlantic sea breeze along the I-95 corridor, resulting in a few storms pulsing and briefly becoming strong during the late afternoon or early evening hours. A few storms could be slow movers along the I-95 corridor around sunset, but activity should quickly diminish as it moves offshore during the early to mid evening hours. Debris cloud cover should thin out towards midnight, with lows falling to the mid 70s inland and the upper 70s at coastal locations. && .SHORT TERM... (Tuesday through Wednesday night) Issued at 420 AM EDT Mon Aug 12 2024 The region will be between high pressure to the east southeast, and an elongated frontal zone to the north and northwest Tuesday. The frontal zone will sink south across forecast area Tuesday night, then push to the south Wednesday, as high pressure builds down the east coast. The boundary will begin to break down Wednesday night, as a potential tropical system develops over the western Atlantic. A little bit drier air will advect into region with boundary will help to limit convection this period. Isolated to scattered showers and storms will develop in the late morning/early afternoon period each afternoon each day. This activity will then largely diminish will loss of diurnal heating in the evenings. Temperatures will trend above normal this period. && .LONG TERM... (Thursday through Sunday) Issued at 420 AM EDT Mon Aug 12 2024 A high pressure ridge will extend down the east coast of the US Thursday, then slide off the coast Friday. Meanwhile, a northward moving potential tropical system will pass by well to the east. Once the tropical system passes further away to the northeast, the high will continue to move further to the east southeast over the weekend, as a trough digs along the US east coast. Surface ridging, and drier air that will be in place behind, will yield lower than normal precipitation chances this period. With diurnal heating, isolated to scattered afternoon convection is forecast. Temperatures will trend near to a little below normal Thursday and Friday, then trend a little above over the weekend. && .AVIATION... (12Z TAFS) Issued at 750 AM EDT Mon Aug 12 2024 VFR conditions prevail at 12z this morning but a chance of MVFR ceilings of around 1500-2500 ft as low levels are very moist and will get cumulus developing pretty quickly this morning. VFR clouds will then develop by early aftn and should already see some convection forming from about 15z-17z (initially near GNV), and we have TEMPO group for GNV and either PROB30 or TEMPO group for other TAFs. Confidence is not too high to go full to TEMPO for all the TAFs as the probabilities are not very high but we will continue to monitor trends in the radar and guidance. Gusts of 25-35 kt will be possible in the convection and some brief vis/cig restrictions. Most of the convection will end by 01z-02z with a lingering shower or two along the coast from SGJ to SSI by that time. Mainly southwest winds 5-10 kt will develop this morning and expect the Atlantic sea breeze boundary will again be slow to progress inland today at SGJ and SSI. && .MARINE... Issued at 420 AM EDT Mon Aug 12 2024 A surface trough will remain situated to the west of our local waters through Tuesday night, resulting in prevailing southwesterly winds across our local waters. Scattered showers and thunderstorms will progress east-northeastward across mainly the near shore waters during the late afternoon and early evening hours today and again on Tuesday. Outside of thunderstorm activity, winds will become southeasterly over the near shore waters during the afternoon hours as the sea breeze pushes slowly inland. Seas of 2 to 4 feet will prevail both near shore and offshore through Wednesday night. A cold front will then approach our area from the north on Tuesday night, pushing through the Georgia waters on Wednesday morning and the northeast Florida waters by Wednesday evening. High pressure building over New England and the Mid- Atlantic states in the wake of this frontal boundary will then wedge down the southeastern seaboard in the wake of this frontal passage, creating strengthening onshore winds by Wednesday night and Thursday. Meanwhile, distant Potential Tropical Cyclone 5 will remain east of the Bahamas as it turns northward late this week, resulting in building seas and increasingly rough surf throughout our local waters by late Friday and the upcoming weekend. Caution level seas of 4 to 6 feet are expected offshore by Friday, with near shore seas building to the 3 to 5 foot range. Rip Currents: A lingering easterly ocean swell will combine with developing onshore winds this afternoon to keep a lower-end moderate rip current risk in place at the northeast FL beaches today. Low wave heights should keep the risk low at the southeast GA beaches today, and a low risk appears likely at all area beaches on Tuesday. Long period swells from distant Potential Tropical Cyclone #5 will begin to enter our local waters on Friday, bringing an elevated rip current risk to all area beaches from Friday afternoon through the upcoming weekend. && .HYDROLOGY... Issued at 420 AM EDT Mon Aug 12 2024 Water levels have crested in a moderate flood along lower portions of the Santa Fe River near the gauge at Fort White. Moderate flooding will continue around this gauge through at least early Friday. Rises will continue downstream towards the Three Rivers Estates gauge, where a crest near major flood levels is forecast later this week. Water levels along middle and lower portions of the Santa Fe near the gauges at High Springs, O`Leno State Park and Worthington Springs have fallen back to minor flood levels. Otherwise, minor flooding is forecast at the gauge near Hildreth, where a crest is forecast late this week or during the upcoming weekend. Water levels have crested in a minor flood along upper portions of the Suwannee River near the gauges at Suwannee Springs and White Springs. Water levels have crested in a moderate flood near the gauge at Benton. Rises will continue downstream along lower portions of the Suwannee River during the next week, with minor flooding forecast at several gauges from around the gauge at Luraville and points downstream. Water levels have crested in a moderate flood along lower portions of the Satilla River near the gauge at Atkinson, where water levels have since fallen back to minor flood levels. Water levels are forecast to fall below flood stage late this afternoon at the gauge further upstream near Waycross. Water levels are cresting in a moderate flood along lower portions of the Altamaha River near the Everett City gauge. Water levels are forecast to fall below flood stage at this gauge by late Tuesday afternoon. River levels have fallen below flood stage for gauges upstream on the middle and upper portions of the Altamaha River. Moderate flooding will continue through late this week along the St. Marys River near the gauge at Macclenny, with water levels downstream recently crest at the major flood threshold near the gauge at Traders Hill. Crests have occurred along the Alapaha River, where water levels will fall below flood stage later today near the gauge at Jennings. && .PRELIMINARY POINT TEMPS/POPS... AMG 96 74 96 75 / 20 10 20 10 SSI 92 80 92 77 / 40 20 30 10 JAX 96 76 96 77 / 50 50 30 10 SGJ 93 78 94 77 / 50 10 30 10 GNV 93 75 94 75 / 60 10 40 0 OCF 93 75 94 76 / 60 10 40 0 && .JAX WATCHES/WARNINGS/ADVISORIES... FL...Heat Advisory from 11 AM this morning to 7 PM EDT this evening for FLZ021-023-024-030-031-033-035-038-120-124-125-132-133- 136>138-140-220-225-232-236-237-240-322-325-340-422-425-522. GA...Heat Advisory from 11 AM this morning to 7 PM EDT this evening for GAZ136-151>154-162-163-165-166-250-264-350-364. AM...None. && $$