textproduct: Jacksonville

KEY MESSAGES

For the latest NE FL and SE GA Daily Key Messages please visit: https:/www.weather.gov/media/jax/briefings/nws-jax-briefing.pdf

- Isolated to Widely Scattered Afternoon & Evening Thunderstorms

- Dangerously Hot & Humid Conditions Late this Weekend. Heat Advisory Conditions Possible Sun & Mon, Peak Heat Index: 108 -110 F

- Minor Flooding Along the Satilla River in Southeast GA

NEAR TERM /THROUGH TONIGHT/

Main Highlights Today and Tonight:

- Scattered Strong/Isolated Severe Storms this afternoon/evening, mainly for Northeast Florida, between the I-95 and US-301 corridors

Old frontal boundary across NE FL will dissipate as it lifts back to the north through tonight, which will bring deeper moisture and PWATs into the 1.7 to 1.9 inch range back northward into NE FL, which will interact with daytime heating and the inland moving East Coast sea breeze to produce scattered to numerous showers and storms this afternoon and evening, mainly between the I-95 and US-301 corridors, strong to isolated severe storms will be possible along the East Coast sea breeze with gusty winds to 40-60 mph, along with locally heavy rainfall due to the slow storm motion, the strongest storms will be along cell mergers from the JAX Metro Area southward along the St. Johns River Basin. Timing is generally 3pm-9pm.

Further northward across SE GA, the drier air mass aloft will be slower to exit the region to the NE, as a current shortwave in the mid levels across the SE US states will track into the region from the West by the afternoon evening hours with deeper moisture (PWATs 1.6-1.8") and lift, which should help to trigger scattered late afternoon/evening hours, mainly along the East Coast sea breeze as it presses inland. A few strong to isolated severe storms with gusty winds 40-60mph and locally heavy rainfall as well. Timing of strongest storms across SE GA may be slightly later from 4pm-10pm.

Temps will remain at above normal levels with highs in the mid/upper 90s across inland NE FL and lower 90s coastal NE FL, along with higher humidity values should push Heat Indices up to 102-106F. Slightly lower humidity values lingering across SE GA and dew point temps into the upper 60s will combine with Max temps into the lower/middle 90s to produce seasonable Heat Indices of 98-102F this afternoon.

Slow moving convection along the I-95 corridor this evening around sunset will drift into the Atlantic coastal waters or push NE across the Altamaha River Basin by the midnight time frame. Fair skies and generally quiet weather during the overnight hours with the usual muggy overnight lows in the 70s inland and near 80F along the Atlantic beaches. Some convergence in SW flow along the NE Gulf may trigger some isolated storms along the NE Gulf Coast that may drift into Gilchrist county towards sunrise Friday morning.

SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/

Main Highlights This Period:

- Widely Scattered Afternoon and Evening Thunderstorms Friday - Seasonably Hot and Humid Weather Friday and Saturday

Friday, a little faster southwesterly low to mid level flow over the region as Bermuda surface ridging becomes established over the southern half of the FL peninsula. Near normal moisture values will remain, but lack of shortwave energy will keep T'storm chances to widely scattered as the Gulf seabreeze pushes well inland with a few T'storm mergers along the US-17 corridor. T'storms will end before 10PM.

Saturday, mid to upper level ridging will build over the central Gulf coast with westerly flow aloft turning more northwesterly by afternoon. At the surface, Bermuda high pressure surface ridge axis will stretch across central FL with light west southwest flow in the low levels. This will allow the Gulf seabreeze a head start and pin the Atlantic seabreeze east of US-17. Initial Isolated showers and T'storms will increase to widely scattered T'storms within the St Johns river basin south of Jacksonville into north central FL where higher moisture axis will be along with less subsidence, allowing for convection to develop.

Highs will rise to the mid 90s along west of I-95 across our inland zones cooling to the low 90s west of US-441 over SE GA and along the coast each day with peak heat index values maxing out in the 102-106 range. Lows will be above normal in the mid to upper 70s Friday and Saturday mornings.

LONG TERM /SUNDAY THROUGH WEDNESDAY/

Main Highlights This Period:

- Heat Index Values May Approach Heat Advisory Criteria Sunday, and into heat advisory levels Monday.

- Numerous T'storms across the area Monday, decreasing coverage into Midweek

Sunday, strong mid/upper level ridging over the lower MS valley will build north into the Arklamiss region while surface Bermuda high pressure ridge axis remains over central FL. Aloft, north to northwest flow. Subsidence due to the building ridge just to the NW of the region will limit T'storm chances to widely isolated primarily east of Highway 301 with widely scattered T'storms over the St Johns river basin. Mostly sunny, skies and rising heights will send highs into the upper 90s for most inland areas away from the coast. Heat index values will rise to 104-108 with some isolated pockets 108-110 values south of I-10 as daytime humidity remains with dewpoints mixing down into the low 70s.

Monday, an mid/upper level trough will dive along the southeast coast as a strong heat dome mid/upper level ridge builds over the mid south and mid MS valley. The upper trough will bring a surface "back door" cold front towards the area, but another hot afternoon will result ahead of this front before it arrives providing plenty of instability. The NNW flow aloft will allow inland progression of both seabreezes before merging with above normal moisture levels supporting numerous T'storm coverage. The high humidity and hot temperatures will deliver widespread heat index values into heat advisory levels of 108-110 with isolated pockets of higher values near 112 before T'storms, rain and gusty outflows cool temperatures down.

Tuesday, strong ridging will shift across the OH valley while sfc high pressure builds to the NNE over the Mid Atlantic states with increasing northeast onshore flow and breezy winds 10-15 mph, but gusting to 25 mph. This will push the Atlantic seabreeze SW to the I-75 corridor. Highest coverage of T'storms will be inland south of I-10 inland into north central FL with widely scattered T'storms away from the coast northward as drier air aloft presses in from the north and northeast. Highs will cool to the low 90s along I-95 and the mid 90s near I-75 with upper 80s along the coast. Heat index values will peak 104-108 inland.

Wednesday, the heat dome ridging aloft will build to the NNW over the upper OH valley with NE flow aloft. High pressure to the north will retreat to off the New England coast with ENE winds still breezy with a a long fetch of low level moisture from the Atlantic underneath drier air aloft due to the ridging north of the region, lowering overall moisture levels a little below normal. Scattered inland T'storm coverage is expected in this pattern. Highs in the low to mid 90s inland will again limit heat index values below heat advisory levels.

Temperatures will begin the period above normal Sunday and Monday and cool midweek to slightly above normal inland and near normal at the coast.

AVIATION /06Z THURSDAY THROUGH 06Z FRIDAY/

VFR conds through Thursday morning, then diurnal heating, increasing moisture levels aloft and inland moving East Coast sea breeze will support scattered storms in the 18-24Z time frame and will continue PROB30 groups for TSRA, MVFR VSBYS/CIGS and gusty winds at all NE FL terminals, slightly lower chances at KSSI so will hold only a VCTS there during the afternoon hours. Rainfall chances decrease around sunset Thursday evening, leaving VFR conds through the end of the TAF period with lingering mid/high clouds.

MARINE

A weak boundary that will be over the local waters today will dissipate Tonight. A high pressure ridge will then build over through Saturday. High pressure will then influence the weather pattern into next week.

Rip Currents:

A lower end moderate risk will develop during the late afternoon hours each day through Friday at area beaches as onshore winds become breezy following the passage of the sea breeze. A developing southeasterly ocean swell will combine with onshore winds developing during the mid to late afternoon hours this weekend to maintain a lower end moderate risk at all area beaches.

FIRE WEATHER

- Areas Of High Daytime Dispersion Inland Friday

Today, light southerly winds 3-5 mph will become southwesterly 5-10 mph by the afternoon. Atlantic seabreeze will develop at the coast by noon, moving onshore past I-95 in the early afternoon hours, and US-17 by late afternoon with easterly winds 5-10 mph behind its passage. With an increase in moisture aloft, scattered T'storms will develop as the Atlantic seabreeze shifts onshore with more numerous tT'storms along the St Johns river basin. High temperatures will rise to the mid 90s away from the coast with heat index values ranging 100-105. MinRH values will be 35-40 percent inland.

Friday, more moisture will return over the area with southwest flow off the Gulf coast yielding widely scattered afternoon T'storm coverage with Atlantic seabreeze struggling to move as far inland remaining east of US-17 through the afternoon hours. Increasing mixing heights and gradually increasing transport winds from the southwest will lead to areas of high daytime dispersions Friday.

Hot and mostly sunny conditions expected this weekend with highs in the upper 90s away from the coast each day with heat index closing in on heat advisory levels 106-110 by Sunday and widely scattered T'storms. Dispersions will be in the good range.

FOG POTENTIAL AND OTHER REMARKS: Significant fog is not expected the next few mornings into the weekend. Gusty winds to 40-50 mph, frequent lightning, and locally heavy downpours will be the main hazards from T'storms today. Slow storm motions may lead to minor flooding concerns in urban and low lying areas, especially east of highway 301.

HYDROLOGY

Minor Flooding will continue along the Satilla River Basin into the upcoming weekend.

PRELIMINARY POINT TEMPS/POPS

AMG 93 72 93 74 / 40 50 50 20 SSI 88 77 92 78 / 20 20 40 20 JAX 94 74 96 76 / 50 30 50 20 SGJ 93 75 95 76 / 50 30 50 30 GNV 96 73 95 74 / 50 20 30 10 OCF 95 73 94 75 / 40 20 40 10

JAX WATCHES/WARNINGS/ADVISORIES

FL...None. GA...None. MARINE...None.