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 Storms This Evening over inland Northeast FL

- Isolated to Widely Scattered Afternoon & Evening Thunderstorms Wednesday

- Dangerously Hot & Humid Conditions Late this Weekend. Heat Advisory Conditions Possible Sun & Mon, when Values Approach 110

- Minor to Moderate Flooding Along the Satilla River in Southeast GA

NEAR TERM /THROUGH TONIGHT/

Main Highlights Today and Tonight:

- Drier air mass will limit convection to portions of Northeast Florida south of a line from Gainesville to St Augustine

Rather unusual southward push of a weak "cool" frontal boundary for late June will clear SE GA this morning and stall across NE FL this afternoon. A much drier air mass will push in aloft with PWATs dropping to around an inch or less across SE GA and into the 1.2 to 1.4 inch range across NE FL. This will basically shutdown diurnal convection chances from the I-10 corridor northward across SE GA to around 10% or less. Meanwhile in areas across NE FL closer to the stalled frontal boundary, a few morning showers and /or isolated storms will be possible, along with widely scattered showers and storms this afternoon as the East Coast sea breeze pushes inland. Any significant afternoon convection will be mainly south of a line from Gainesville to Augustine in the 3pm-9pm time frame, and mostly between the I-95 and US 301 corridors along the St. Johns River Basin. Still enough moisture aloft and cool mid levels to support a few strong to isolated severe storms with gusty winds to 50 mph and locally heavy rainfall due to the slow storm movement, mainly for Putnam, Flagler and Marion counties.

Despite the weak cool frontal boundary pushing into the region, temps today will still be on the Hot side with Max temps well into the lower/middle 90s inland, and even some upper 90s across inland NE FL, while the East Coast sea breeze will hold the Atlantic beaches "cooler" than yesterday as onshore flow peaks temps out closer to 90F. The main difference behind the frontal boundary will be the "lower" humidity values as dew point temps mix out into the mid/upper 60s across SE GA, upper 60s/near 70F along the I-10 corridor, and lower 70s for the rest of NE FL. Despite the hot temps the lower humidity values will hold heat indices in the mid/upper 90s across SE GA and around 100F along the I-10 corridor and into the 102-106F range for the rest of NE FL to the south of I-10.

SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/

Main Highlights This Period:

- Widely Scattered Afternoon and Evening Thunderstorms Thursday and Friday

- Seasonably Hot and Humid Weather Thursday and Friday

Thursday, a dampening mid/upper level trough moving through the deep south will back winds aloft to the SW as Bermuda high ridging aloft well SE of the region. The flow pattern will deliver higher moisture content compared to Wednesday with PWATs increasing to near normal values 1.5-1.75 inches. The SW flow will allow the Gulf seabreeze to progress northeastward with isolated to widely scattered showers increasing in coverage along the I-95 coverage slightly as the Gulf seabreeze and storm outflows merge with the slower moving Atlantic seabreeze. The weakening shortwave energy will allow for some lingering convection over inland SE GA late afternoon into the early evening hours before ending by midnight. Slow storm motions Thursday will create potential for locally heavy downpours and minor flooding in low lying areas.

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. Wind gusts to 40 mph expected along with Frequent lightning and locally heavy downpours Thursday and Friday.

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. Lows Thursday and Friday mornings will be a little above normal in the low to mid 70s.

LONG TERM /SATURDAY THROUGH TUESDAY/

Main Highlights This Period:

- Hot conditions This weekend into Monday

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

- Widely Scattered Afternoon and Evening Thunderstorms from Saturday through Sunday, Mainly Along the St Johns river basin Corridor

- Numerous T'storms across the area Monday

This weekend, mid/upper level ridging over the northeast Gulf will retrograde and build across the Arklamiss region as surface Bermuda high pressure ridge axis lifts into central FL. Aloft, light westerly flow Saturday will become northwesterly on Sunday. The Subsidence due to the building ridge just to the NW of the region will limit T'storm chances to widely isolated over locations 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, very close to heat advisory levels as daytime humidity remains with dewpoints in the low 70s.

Monday, an mid/upper level trough will dive southeast from the Mid Atlantic coast into the Atlantic waters off the Carolina coast as strong mid/upper level ridge builds over the mid south and mid MS valley. A surface "back door" cold front will approach from the north Monday evening with another hot afternoon as highs inland rise into the upper 90s ahead of the approaching front providing plenty of instability. The NW flow aloft will allow inland progression of both seabreezes and increasing shortwave energy and seasonably moist atmosphere will lead to numerous T'storm coverage. Heat index values will bump higher into the 106-110 range as dewpoints rise to the mid to upper 70s.

Tuesday, strong ridging will shift across the OH valley and surface high pressure will build in from the north over the Mid Atlantic states with increasing northeast onshore flow pushing the Atlantic seabreeze SW into the I-75 corridor. Highest coverage of T'storms will be over north central FL with widely scattered T'storms away from the coast northward as drier air aloft presses in from the north and northeast.

Temperatures will begin the period above normal this weekend into Monday with temperatures Tuesday a little above normal inland and near normal at the coast.

AVIATION /06Z WEDNESDAY THROUGH 06Z THURSDAY/

Much drier air mass pushing into the region for Wednesday will shut down most of the afternoon convection at NE FL/coastal SE GA terminals and with rainfall chances less than 20% at all terminals will leave out any mention with this forecast package. Lighter winds and some clearing VFR skies early this morning will allow for some low MVFR BR potential at GNV/VQQ. Morning diurnal heating and some lingering low level moisture at GNV/SGJ will provide some 20-30% chances of brief MVFR CIGS in the 11-15Z time frame, but probs too low for any TEMPO groups and will continue mention of just SCT 015- 025 for now. Light winds with east coast sea breeze passage at coastal terminals this afternoon with speeds still at 10 knots or less through the afternoon hours. Decreasing winds and mainly VFR conds expected after sunset through the end of the current forecast period (06Z Thursday).

MARINE

A weak frontal boundary will drift south into the local waters Today which lead to a break in the offshore flow pattern through Thursday before weak offshore winds return this weekend. The Atlantic sea breeze development is likely to develop each day through the weekend along with southerly wind increases to Exercise Caution levels each evening beginning Friday.

Rip Currents:

Rip current risk is expected to remain on the low side Wednesday and Thursday with surf of less than 2 feet. Models suggest a slight uptick by Friday into the weekend with surf around 2 feet and potential Moderate Risk at local beaches.

FIRE WEATHER

- Areas Of High Daytime Dispersion Inland Thursday And Friday

Dry conditions are expected today for most areas with exception of north central FL later this afternoon where convergence of east and west coast seabreezes near a weakening frontal boundary will create scattered T'storms into Ocala national Forest and Flagler County. Otherwise, light northwest winds prevail 5-10 mph with the afternoon Atlantic seabreeze turning winds easterly 8-12 mph shifting to I-95 by late afternoon. Hot conditions expected under mostly sunny skies with highs in the low to mid 90s. Max heat index values will rise to 100-105 south of I-10. Min RH values inland will be 35-40 percent.

Thursday and Friday, moisture will return aloft with a return of light southwest flow yielding widely scattered afternoon T'storm coverage with Atlantic seabreeze shifting west across I-95 in the mid afternoon hours and near highway 301 after sunset. Increasing mixing heights and gradually increasing transport winds from the southwest will lead to areas of high daytime dispersions Thursday and Friday. Hot and mostly sunny conditions expected this weekend with highs in the upper 90s away from the coast each day with heat index values close to heat advisory levels peaking 104-108.

FOG POTENTIAL AND OTHER REMARKS: Patchy, shallow ground fog is possible early this morning over areas that received rainfall Tuesday between Waycross and Gainesville. Isolated strong to severe T'storms over north central FL with threat for gusty wet downburst winds over 50 mph.

HYDROLOGY

Minor to locally moderate flooding on the Satilla River Basin will continue to move downstream and impact the forecast points at Waycross and Atkinson this week.

PRELIMINARY POINT TEMPS/POPS

AMG 92 70 93 73 / 10 10 20 30 SSI 88 77 89 79 / 0 0 20 10 JAX 94 73 95 76 / 10 10 50 10 SGJ 92 75 93 77 / 10 10 40 10 GNV 96 72 96 74 / 10 10 20 10 OCF 96 73 95 75 / 30 10 30 10

JAX WATCHES/WARNINGS/ADVISORIES

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