836 FXUS62 KJAX 100712 AFDJAX Area Forecast Discussion National Weather Service Jacksonville FL 312 AM EDT Fri Sep 10 2021 ...DRIER TODAY FOR SE GA WITH CONVECTION ACROSS NE FL... .NEAR TERM [Through Tonight]... A surface front in the wake of departing post-tropical cyclone Mindy will slide across the local area this morning as surface high pressure builds northwest to north of the region. In the upper levels, a long wave trough extended from New England to across the central Gulf Coast states, with embedded mid level lobes of PVA tracking across the local area from the WSW. As the surface front slides southward across SE GA this morning, a drier, more stable airmass will prevail into the afternoon under partly cloudy skies and breezy onshore flow at the coast. The higher rain chances will focus across NE FL where the front will begin to stall and linger as a wave of low pressure develops across north- central FL into the afternoon under the deepening upper level trough. Early this morning, a cluster of showers and storms was edging inland from the GOMEX just head of the approaching surface front under passing mid level PVA. Through late morning, this convection will drift eastward across our southern FL zones, with additional showers or isolated storm possible along the actual surface front which was shifting south of the GA waters around 3 am. The stronger mid level short wave trough fueling the early morning storms across the Suwannee River Valley will shift eastward through 15-18z, with convection expected to decrease across our western zones but increase across our eastern FL zones as upper level dynamics phase over the stalling surface front, inducing a broad surface low along the boundary across north-central FL into the afternoon and early evening hours. Surface convergence near this wave of low pressure under a strengthening jet within the deepening upper level trough combined with cool 500 mb temps of -8 to -9 deg C will bring the potential for locally heavy rainfall and a few strong pulse storms generally after 18z across NE FL into the early evening hours especially across the St. Johns River basin and toward toward the Atlantic coast. Convection will tend to shift WSW through 00z as the surface ridge strengthens north and northeast of the region into the evening, shifting the broad surface low westward. Strong storms today will have the potential today and this evening will have the potential to produce gusty winds of 40-60 mph, small hail, locally heavy rainfall and frequent lighting. Although precipitation will decrease in coverage and intensity into the evening over inland areas, the lingering trough axis will serve as a convergent zones tonight which will bring the potential for showers and isolated storms to coastal areas of NE FL through the night. Temperatures will trend near to just below normal with highs in the mid to upper 80s inland to the low/mid 80s along the local coast. Lows tonight will cool into the mid 60s across much of SE GA under partly cloudy to mostly clear skies and backing ENE drainage winds. NE FL lows will range in the 70s under lingering clouds and coastal showers/isolated tstorms. .SHORT TERM [Saturday Through Sunday Night]... A stalled boundary near the Florida / Georgia border will become progressively more diffuse and hardly discernible this weekend. As a result, north of the front, a slightly cooler and drier air mass will prevail across inland portions of southeast GA through this weekend allowing lows to fall into the mid to upper 60s each night. The aforementioned weak frontal boundary and deepening onshore flow will again develop scattered to numerous mainly afternoon and evening convection for locations along and south of I-10 on Saturday, with higher areal coverage and intensity expected during the late afternoon hours across north central FL where dewpoints will be in the lower to mid 70s. Strong storms will again be possible for locations south of Gainesville due to lingering cool temperatures aloft (-10C, 500 mb) as well as mesoscale boundary collisions, which could produce strong downburst winds as well as localized heavy rain / potential flooding due to expected slow storm motion. Highs will generally remain in the mid to upper 80s again area-wide, with higher humidity values keeping lows in the 70s for most of northeast and north central FL. Upper level troughing will then progress off the U.S. eastern seaboard by Saturday night, allowing for the massive ridge currently in place over the Rockies to expand eastward into our region with center of ridge over the Mid South extending into Georgia. Consequently, there will be a big moisture gradient across the region Sunday with precipitable water values across SE Georgia between 1.25 and 1.50 inches with 1.75 to 2 inches across northeast and north central Florida. This change in the weather pattern should allow for only isolated to widely scattered afternoon and evening convection to develop for locations south of I-10 on Sunday. Our local pressure gradient will also loosen as high pressure over the Carolinas weakens. Highs will climb to the upper 80s to near 90 for inland locations, while a lingering onshore breeze keeps coastal highs mostly in the mid 80s. .LONG TERM [Monday Through Thursday night]... Ridging aloft will briefly reside over the SE U.S. early next week and will then progress eastward towards midweek, with deepening southeasterly flow expected towards midweek. Moisture levels will gradually increase each day, but convective coverage should be limited to widely scattered early next week, with less coverage expected across southeast GA. Higher rain chances will then develop towards midweek as tropical moisture overspreads our area from southeast to northwest. Highs early next week will generally climb to around 90 inland and the mid 80s at coastal locations, followed by highs cooling slightly towards midweek as cloud cover and convective chances increase. The lingering dry and subsident air mass should allow lows to fall to the 60s again on Monday night in southeast GA, but 70s will then prevail area-wide by midweek as humidity levels climb. && .MARINE... A front will move south across the local waters this morning then begin to stall across north-central Florida this afternoon. A wave of low pressure will form along the surface front this afternoon, then will shift west across the Gulf of Mexico tonight as high pressure strengthens northeast of the region. An extended period of easterly flow is expected Saturday through Tuesday. Elevated combined seas due to long-period swells will gradually subside late this weekend. Continued Small Craft Advisory headline for the outer today and tonight due to marginal combined seas near 7 ft, with a Small Craft Exercise Caution headline for the near shore waters due to combined seas near 6 ft at times. Latest NWPS run was trending about 1-2 ft at times too high for wave heights based on buoy observations, and if this trend continues will update to trend more toward the WNA guidance which lowers seas to below SCEC over the near shore waters today and has only a brief period of near 7 ft seas tonight (Fri night) near the Gulf stream for waters south of St. Augustine. Rip Currents: A high rip current risk will continue for all local beaches through Saturday due to persistent, long period easterly swells combined with strengthening onshore flow. Swells dampen Sunday into Monday, with a moderate rip current risk likely by early next week. && .HYDROLOGY... Minor flooding continued along lower portions of the Santa Fe River near the Three Rivers Estates gauge. River levels upstream will rise to action stage during the weekend due to recent runoff. && .PREV DISCUSSION [221 AM EDT]... .AVIATION... [Through 06Z Saturday] Prevailing VFR conditions expected through 12z with tempo MVFR at VQQ due to shallow ground fog. Will also need to monitor inland progression of early morning convection drifting inland from the Gulf Coast region which could impact GNV through 12z and at this time indicated VCSH by 08z. NE winds increase at SSI this morning trailing an early morning frontal passage. This front is expected to stall and linger across NE FL this afternoon as a wave of low pressure develops along the boundary across north-central FL this afternoon. Showers and storms will increase in coverage and intensity after 17z across NE FL into the early evening under easterly winds. Advertised VCSH BY 16z for NE FL terminals with VCTS by 16-19z. Easterly winds increase at coastal terminals through the day today from SSI to SGJ with gusts of 11-13 kts into the early evening. Precip coverage will tapper off inland during the early evening, but onshore low level flow under a deepening mid/upper level trough will continue isentropic lift over the area along the meandering front along the NE FL coast tonight, which could bring passing showers or TS to SGJ, CRG and potentially JAX through 06z Saturday. SREF probabilities suggest the highest potential for MVFR ceilings at SGJ this afternoon and evening between 18z-00z. .FIRE WEATHER... Breezy westerly surface and transport winds will quickly diminish this evening and will shift to northwesterly towards midnight and then northerly towards sunrise on Friday. Breezy northeasterly surface and transport winds will then develop towards noon at coastal locations and will gradually spread inland towards the Suwannee Valley. Lighter wind speeds will prevail across inland southeast Georgia as well as north central Florida, where low daytime dispersion values are expected. Meanwhile, a drier air mass will filter into inland portions of southeast Georgia from Friday through the weekend, where minimum relative humidity values will fall to 40-45 percent during the afternoon hours. Breezy easterly surface and transport winds will continue across northeast Florida this weekend, with lower speeds over north central FL resulting in marginally low daytime dispersion values. && .PRELIMINARY POINT TEMPS/POPS... AMG 86 66 87 65 88 / 10 10 10 0 10 SSI 84 73 86 75 86 / 10 10 20 10 20 JAX 86 70 87 73 88 / 30 30 30 10 20 SGJ 85 74 85 74 86 / 50 50 50 10 30 GNV 88 71 87 70 88 / 50 40 50 10 30 OCF 88 71 88 72 89 / 60 50 50 10 30 && .JAX WATCHES/WARNINGS/ADVISORIES... FL...High Rip Current Risk through late Saturday night for Coastal Duval-Coastal Flagler-Coastal Nassau-Coastal St. Johns. GA...High Rip Current Risk through late Saturday night for Coastal Camden-Coastal Glynn. AM...Small Craft Advisory until 7 AM EDT Saturday for Waters from Altamaha Sound GA to Fernandina Beach FL from 20 to 60 NM- Waters from Fernandina Beach to St. Augustine FL from 20 to 60 NM-Waters from St. Augustine to Flagler Beach FL from 20 to 60 NM. &&