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

- Scattered to Numerous Thunderstorms this Afternoon and Evening. Isolated Strong Storms Will be Capable of Gusty winds (35-45 mph), Frequent Lightning, and Heavy Downpours that May Lead to Localized Flooding. Strongest Storms Likely along and South of the I-10 Corridor during the Late Afternoon and Evening.

- Scattered to Numerous Afternoon and Evening Thunderstorms Each Day from Thursday through Saturday.

- Moderate Rip Current Risk Continues at All Area Beaches.

NEAR TERM /THROUGH TONIGHT/

Highlights through Tonight:

- Strong thunderstorms with locally gusty winds and heavy downpours expected across coastal southeast GA, northeast and north central FL early this afternoon and evening.

- Slow storm motion may result in localized flooding for areas along and south of I-10 corridor, especially if downpours develop over urban and normally flood prone locations.

Afternoon surface analysis depicts a wavy, stationary frontal boundary extending from coastal South Carolina eastward across south central GA and then snaking across the lower Mississippi Valley. High pressure (1018 millibars) was situated to the south of this boundary over the eastern Gulf, while stronger high pressure (1021 millibars) was positioned to the north of the frontal boundary just east of the Chesapeake Bay. Aloft...troughing over the Upper Midwest, Great Lakes, and Mid- Atlantic states was being reinforced by a potent shortwave trough that was crossing Lake Superior. Otherwise, a broad trough remains in place over our area in between ridges that are centered over the Desert Southwest and also to the east of the Bahamas. Latest GOES-East derived Total Precipitable Water imagery indicates that tropical moisture remains in place across most of our region, with PWATs mostly around 2 inches. A moist and unstable air mass in place across our area to the south of the stalled boundary and slightly cooler temperatures aloft associated with the upper trough have developed scattered to numerous showers and thunderstorms across southeast GA, with isolated convection developing along the I-95 and U.S. Highway 17 corridors in northeast and north central FL. Temperatures at 18Z have climbed to the upper 80s and lower 90s across most of northeast and north central FL, while clouds and rainfall were keeping temperatures across southeast GA generally in the 70s and 80s. Dewpoints at 18Z ranged from the upper 60s to the upper 70s.

Convection is expected to increase in coverage across northeast and north central FL late this afternoon through the early evening hours, where heat and instability resides to the south of widespread cloud cover and lingering convection that currently covers most of southeast GA. Slightly cool temperatures aloft and mesoscale boundary collisions will likely result in storms "pulsing" and becoming strong, with downburst winds of 35-45 mph possible, along with frequent lightning strikes. The bigger threat through this evening for locations along and south of I-10 will be heavy downpours and the potential for localized flooding due to expected slow storm motion. Activity developing along the I-95 and U.S. Highway 17 corridors this afternoon may tend to "backbuild" towards the I-75 corridor towards the early evening hours as convection tends to fade over interior southeast GA. Convection will then dissipate overnight, although another round of nocturnal convection is expected in the prevailing southwesterly low and mid level flow across Apalachee Bay and the northeast Gulf, with this activity potentially moving onshore along the FL Big Bend and Nature Coasts during the predawn hours. A few showers and storms could sneak into the Suwannee Valley and north central FL towards sunrise, with debris cloud cover from afternoon and evening convection otherwise thinning out overnight. Lows tonight will generally fall to the low and mid 70s.

SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/

Main Highlights This Period:

- Chance for a isolated strong to severe storms each afternoon and evening Thursday & Friday

Southwest flow continues to enhance moisture across the area Thursday and Friday, with daily rounds of afternoon/evening thunderstorms expected. With generally weaker storm motion and PWATs >2.0" there will be a lingering heavy rainfall and localized flooding threat for all of northeast Florida and southeast Georgia. Overall, there may be some isolated activity in the mornings closer to the western counties, but highest precipitation chances will be in the afternoons through sunset, where rain chances are around 60- 80%. Isolated strong to severe storms will be possible wherever we have boundary/sea breeze collisions, gusty winds will be the primary threat.

Temperatures will be near normal, in the upper 80s to lower 90s, with max afternoon heat index values around 95-105 degrees.

LONG TERM /SATURDAY THROUGH WEDNESDAY/

Main Highlights This Period:

- Chances For Isolated Strong to Severe Storms and Heavy Rainfall Continues Each Afternoon and Evening.

High pressure builds across the northeast US this weekend as a front lingers across Georgia Saturday, later sinking near the Florida/Georgia state border on Sunday. This front coupled with southerly flow transitioning to southeasterly flow Sunday will continue to bring high PWATs and an isolated flooding risk through this period. High precipitation chances will be present inland Saturday and Sunday, with the coast having scattered storm chances as the Atlantic sea breeze pushes far inland. 'Cooler' coastal temperatures in the mid to upper 80s expected with the onshore flow, as inland highs reach the lower to mid 90s this weekend.

Monday and Tuesday will be a similar setup, with onshore winds keeping the coast a little cooler and lower precipitation chances than inland locations. Steering flow becomes a little more from the northeast, lowering PWATs and rain chances compared to the weekend. Highest storm chances both Monday and Tuesday afternoons/evenings will be over north central Florida.

AVIATION /18Z WEDNESDAY THROUGH 18Z THURSDAY/

The 18Z TAF period will begin with most of the showers and thunderstorms initially northwest of the TAF sites and have VFR conditions through 20Z, but will include VCTS at all sites except GNV until that time.

By 21Z, growing coverage of thunderstorms is expected with stronger thunderstorms developing along the pinned Atlantic seabreeze as the light southwest winds and low level southwest flow pushes the early storm outflows to the east and merge with the seabreeze and other storm outflows. Have tempo groups for stronger thunderstorms producing gusty outflow winds to 25 knots and MVFR VSBY which may require an upward adjustment with wind gusts should a stronger storm merger appear likely near a terminal. Storms will trend more to the southwest to the GNV TAF sites so TEMPO group will be in play through 01Z there. Scattered showers will persist under lingering storm anvil debris clouds through 02-06Z with PROB30 groups at the duval terminals for less confidence in late evening thunderstorms.

Light southerly winds around 5 knots or less will become more southwesterly towards dawn with MVFR dog at VQQ and near GNV after 06-08Z.

Thursday, VFR conditions return by 13Z at all sites with light southwest winds increasing to 5-8 knots with overall less 0 will be heavy downpours and the potential for localized clouds, but showers returning near the end of the period from strong heating and a front lingering to the north with a seabreeze developing at SSI and SGJ by 17Z.

MARINE

A stalled frontal boundary positioned just north of the Georgia waters will remain in place during the next several days. Thunderstorms developing over coastal locations will push across our local waters through Friday, mainly during the afternoon and evening hours, with strong to isolated severe storms possible. Offshore winds will otherwise prevail during the overnight and morning hours, with the Atlantic sea breeze shifting winds to onshore each afternoon across the near shore waters. Southerly winds will then surge each evening, with speeds briefly approaching Caution speeds around sunset outside of ongoing thunderstorm activity. Stronger high pressure building over New England this weekend will shift prevailing winds to onshore across our local waters, with scattered showers and thunderstorms possible at any time during the upcoming weekend and early next week.

Rip Currents: Following the sea breeze a lower end Moderate Risk is expected at all area beaches each afternoon during the next through the end of the week.

FIRE WEATHER

A frontal zone will remain nearly stationary across southern GA through the end of the week, persisting elevated chances for showers and thunderstorms each day, mainly during the daytime hours. Weak high pressure ridging across and just south of the region will keep the flow direction generally out of the south to southwest, with winds peaking during the evening and overnight hours. Another frontal boundary drops southward towards area waters this upcoming weekend, maintaining an active pattern.

Fog Potential: Significant fog is unlikely over the next several days. Gusty and erratic winds can be expected in and near thunderstorms.

PRELIMINARY POINT TEMPS/POPS

AMG 72 93 72 92 / 50 60 20 70 SSI 75 90 76 90 / 60 40 20 60 JAX 73 92 72 92 / 50 60 20 80 SGJ 74 91 74 91 / 30 50 30 70 GNV 72 90 72 90 / 40 60 10 70 OCF 72 90 73 90 / 30 50 10 60

JAX WATCHES/WARNINGS/ADVISORIES

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