Area Forecast Discussion
Issued by NWS Jacksonville, FL
Issued by NWS Jacksonville, FL
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820 FXUS62 KJAX 170733 AFDJAX Area Forecast Discussion National Weather Service Jacksonville FL 333 AM EDT Tue Sep 17 2024 ...TIDAL FLOODING PERSISTS ALONG THE ATLANTIC COAST, ICWW & ST. JOHNS RIVER BASIN... .NEAR TERM... Issued at 333 AM EDT Tue Sep 17 2024 For the latest NE FL and SE GA Daily Key Messages please visit: https://www.weather.gov/media/jax/briefings/nws-jax-briefing.pdf The region will be on the southern periphery of a weakening stacked low associated with the remnants of PTC 8 over the Carolinas today. This will result in west-southwesterly flow which will keep the Atlantic sea breeze pinned to the I-95 corridor. Drier air (PWATs 1.3 - 1.5 in.) has advected in from the north which will suppress convection across SE GA for today. A lingering frontal boundary over central FL will gradually lift northward up the peninsula through the day maintaining decent moisture across north-central FL. Convection will be diurnally driven and along the sea breezes as they shift inland this afternoon. Isolated to widely scattered showers/t`storms will develop mainly south of I-10 corridor. Convection wanes this evening with the loss of daytime heating. Temperatures warm to around climo with highs in the mid 80s in SE GA to around 90 in north- central FL. Overnight lows will be in the upper 60s to low 70s. && .SHORT TERM... (Wednesday through Thursday night) Issued at 333 AM EDT Tue Sep 17 2024 The cutoff trough that was once Potential Tropical Cyclone #8 will meander over the southern Appalachians on Wednesday, with the base of this trough swinging eastward across our region during the afternoon and evening hours. Meanwhile, a stubborn frontal boundary that has been nearly stationary across the FL peninsula and panhandle during the past several days will lift north of our area, placing our region in a seasonably warm and humid air mass. Scattered convection is expected to develop along mesoscale boundaries such as the Gulf and Atlantic sea breezes during the afternoon hours, with deep west-southwesterly flow tending to focus mesoscale boundary collisions along the I-95 corridor during the late afternoon and early evening hours. Colliding mesoscale boundaries may allow for a few storms to pulse and become strong as they intersect the pinned Atlantic sea breeze boundary along the coast during the late afternoon and early evening hours, with stronger storms being capable of producing downburst winds of 40-50 mph, along with slow moving downpours and frequent lightning strikes. Highs will climb to the upper 80s to around 90, with a few lower 90s possible in north central FL. Maximum heat indices will reach the 95-100 degree range in the early to mid afternoon before convection and cloud cover become more widespread during the late afternoon. Evening convection may linger along the I-95 corridor to the south of Jacksonville and across north central FL, with activity then pushing offshore or towards the I-4 corridor before midnight. Flow aloft will shift to a more west-northwesterly direction overnight following the passage of the base of the aforementioned trough through our area, which will advect a drier air mass into our region. Lows will fall to the upper 60s to lower 70s inland, ranging to the low and mid 70s at coastal locations. Troughing will lift northeastward towards the Mid-Atlantic region on Thursday, finally pushing the stubborn frontal boundary southeastward across our area as deep-layer flow veers to northwesterly. A drier air mass will continue to advect across inland southeast GA and northern portions of the Suwannee Valley, but enough moisture may be in place for isolated to widely scattered afternoon and early evening convection to develop along the frontal boundary as it crosses coastal southeast GA and the rest of northeast and north central FL. Highs on Thursday will again climb to the upper 80s and lower 90s, with maximum heat indices peaking in the 95-100 degree range during the afternoon hours. Convection that manages to develop during the afternoon hours should push offshore of the northeast FL coast towards sunset, with fair skies expected area-wide overnight. A drier and more subsident air mass may allow for areas of locally dense fog to develop by early Friday morning, especially across inland portions of southeast GA and the Suwannee Valley. Lows will again fall to the upper 60s and lower 70s inland, ranging to the lower 70s at coastal locations. && .LONG TERM... (Friday through Monday) Issued at 333 AM EDT Tue Sep 17 2024 Troughing aloft will persist along the New England and Mid-Atlantic coast on Friday and Saturday, while stout ridging centered over Texas and the southern Plains states late this week begins to flatten as it expands eastward along the northern Gulf coast this weekend. Surface low pressure may strengthen off the Mid-Atlantic coast as it meanders this weekend, while strong high pressure building over Quebec and Atlantic Canada begins to expand down the U.S. eastern seaboard. This weather pattern will eventually tighten our local pressure gradient during the weekend, although there are timing differences at this point in the extended guidance. Model blends currently depict northeasterly low level flow developing locally on Friday and then gradually strengthening as the weekend progresses. This flow may advect isolated to widely scattered showers and possibly a few embedded thunderstorms onshore along the northeast FL coast, with activity potentially shifting inland towards north central FL during the afternoon hours each day. An overall drier and more subsident air mass will prevail for southeast GA and the Suwannee Valley, where a dry stretch of weather appears likely from Friday through at least Monday. Breezy onshore winds during this period should keep coastal highs in the low to mid 80s, with mid to upper 80s forecast for most inland locations. Highs may trend down a few degrees by Monday across inland southeast GA as high pressure wedges into the Deep South. The drier and more subsident air mass will allow lows to fall to the mid to upper 60s at most inland locations through the period, while onshore winds keep coastal lows in the low to mid 70s. && .AVIATION... (06Z TAFS) Issued at 130 AM EDT Tue Sep 17 2024 Patchy fog will develop for inland TAF sites especially KVQQ and KGNV where brief IFR/LIFR conditions are possible. Otherwise, light westerly flow and a return to sea breeze dominated wind regime is on tap today. Isolated showers and thunderstorms are possible but confidence is too low to be bullish enough to predict anything beyond VCSH. May need to consider VCTS at KGNV during the afternoon hours in the next TAF cycle. && .MARINE... Issued at 333 AM EDT Tue Sep 17 2024 Winds and seas subside today as a subtropical low pressure system weakens over the Carolinas. A leftover frontal boundary and weak pressure pattern will linger over the region through the middle of the week. The sea breeze returns with afternoon wind shifts to onshore for the nearshore waters through Thursday. A frontal passage is expected late this week with high pressure building north of the region by this weekend and will lead to an increase in Northeast winds by Friday and Saturday. Rip Currents: Rough surf (4 to 6 ft) and onshore winds in the afternoon will result in high risk of rip currents continuing for area beaches today. Winds and seas subside with a moderate risk anticipated for Wednesday. && .HYDROLOGY... Issued at 333 AM EDT Tue Sep 17 2024 High astronomical tides with the upcoming full moon, trapped tides and runoff from recent heavy rainfall will continue minor to moderate coastal flooding along the St. Johns river through at least mid-week. Waves begin to subside today but minor flooding will continue along the Atlantic coast and ICWW. Peak tidal levels will generally be in the 1.5 to 2.3 ft range above MHHW along the St. Johns River Basin and the Atlantic coast. && .PRELIMINARY POINT TEMPS/POPS... AMG 85 68 88 69 / 0 10 30 10 SSI 83 73 87 72 / 0 10 50 50 JAX 87 72 90 71 / 10 10 60 50 SGJ 85 74 89 72 / 10 10 60 50 GNV 87 71 90 70 / 30 10 50 20 OCF 89 71 91 71 / 30 10 50 10 && .JAX WATCHES/WARNINGS/ADVISORIES... FL...Coastal Flood Warning until 5 AM EDT Wednesday for FLZ033-038- 125-132-137-225-325. Coastal Flood Advisory until 5 AM EDT Wednesday for FLZ124-133- 138. High Rip Current Risk through late tonight for FLZ124-125-133- 138. GA...High Rip Current Risk through late tonight for GAZ154-166. AM...None. && $$