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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

- Strong to Isolated Severe Thunderstorms Late this Afternoon and Tuesday Afternoon and Evening. Stronger Storm Hazards: Wind Gusts of 40-60 mph, Frequent Lightning Strikes and Locally Heavy Downpours. - Timing of Stronger Storms Today: 3 PM - 10 PM. Main Impact Areas: Southeast GA and the Interstate 10 Corridor in Northeast FL.

- Scattered to Numerous Afternoon and Evening Thunderstorms from Wednesday through Sunday.

- Moderate Rip Current Risk at All Area Beaches through Tuesday.

NEAR TERM /THROUGH TONIGHT/

Highlights through Tonight:

- Strong to Isolated Severe Thunderstorms Possible this Afternoon and Evening. Strong Storm Threats: Wind Gusts of 40-60 mph, Frequent Lightning Strikes, and Locally Heavy Downpours.

- Heat Index Values Generally Peak in the 104-108 Degree Range this Afternoon.

Early afternoon surface analysis depicts a wavy, stalled frontal boundary extending from the coastal Carolina region southwestward to near the Altamaha / Ocmulgee Rivers in southeast GA and then westward across the lower Mississippi Valley and southern Plains. Meanwhile, weak high pressure (1018 millibars) was situated to the south of the frontal boundary over the central Gulf, while stronger high pressure (1021 millibars) was building over the Upper Midwest and Great Lakes states in the wake of the stalled front. Aloft...deep troughing extends from the Great Lakes and New England southward through the Mid-Atlantic states and the Carolinas, while "Heat Wave" ridging blankets the Four Corners region of the Desert Southwest, as well as Texas and portions of the southern Plains states. In between these two features, shortwave troughs were diving southeastward from the Upper Midwest through the lower Mississippi Valley. Latest GOES-East derived Total Precipitable Water imagery indicates that a pocket of drier air remains situated over portions of northeast and north central FL, where PWATs were around 1.5 inches. Moisture levels were gradually increasing across inland southeast GA and the Suwannee Valley, where PWATs were closer to late August climatology, where values were mostly in the 1.7 - 1.8 inch range. A healthy cumulus field was developing across most of our region this afternoon, with scattered convection developing along the inland moving Gulf sea breeze boundary across the Suwannee Valley, with other isolated showers and storms developing over inland portions of southeast GA and also over portions of the Ocala National Forest in north central FL. Temperatures at 18Z were soaring to the low and mid 90s at most inland locations, with a slow moving Atlantic sea breeze boundary recently dropping temperatures back to the upper 80s to around 90 at area beaches. Dewpoints ranged from the upper 60s to around 70 across inland portions of southeast GA to the upper 70s to around 80 at coastal locations.

Northwesterly flow aloft will continue across our region through tonight, allowing for a shortwave currently progressing across the lower Mississippi Valley to dive southeastward towards the northern Gulf coast and western portions of the FL panhandle by this evening. Although the best synoptic forcing associated with this shortwave trough will remain to the west of our area, the presence of the stalled frontal boundary just north of our region, moisture levels gradually increasing from west to east, and an unstable atmosphere should allow for scattered to numerous showers and thunderstorms to develop across our region, especially late this afternoon through the evening hours. Colliding mesoscale boundaries should allow for storms to pulse and become strong, with a few isolated severe storms possible later this afternoon and early this evening. Activity should initially develop along inland moving sea, lake, and river breezes, with convection generally moving slowly southeast or southward. The primary threat area for stronger storms will likely be along the I-10 and I-95 corridors, with activity potentially shifting across inland portions of southeast GA this evening, closer to the stalled frontal boundary. Slow storm motion could create localized flooding, especially if activity impacts urban or normally flood prone, low-lying locations.

Before storm coverage increases this afternoon, heat index values will flirt with Heat Advisory criteria (108 degrees), as most locations experience values in the 104-108 degree range before convective coverage increases. Lingering convection across inland southeast GA should dissipate towards midnight, with debris cloud cover gradually thinning out overnight through the predawn hours on Tuesday. Lows will fall to the 70s inland, ranging to the upper 70s to around 80 at coastal locations.

SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/

Main Highlights This Period: (Wednesday through Thursday night)

- Chance for a few strong to severe storms each afternoon and evening this period.

The fairly persistent pattern with high pressure to the southeast, and frontal zone to the north this period will continue this period. A weak upper trough will be in place. The combination of sea breeze interactions, diurnal heating and added instability under upper trough will yield daily convection chances, mainly in the afternoon and evening hours. The chance will exist both days for a few of these storms to become strong to severe.

Temperatures will trend a little above average this period.

LONG TERM /THURSDAY THROUGH MONDAY/

Main Highlights This Period: (Friday through Monday)

- Chance for a few strong to severe storms each afternoon and evening this period.

The surface pattern will remain fairly persistent with a frontal zone across GA, and weak high pressure extending across FL. The weak upper trough will continue through Saturday, with an upper ridge then building overhead Sunday. Daily rounds of afternoon and evening thunderstorms this period, with the greatest chances through Saturday due to the added instability from upper trough.

Temperatures will be a little above average this period.

AVIATION /18Z MONDAY THROUGH 18Z TUESDAY/

VFR conditions will prevail at the regional terminals through around 20Z. Showers and thunderstorms developing over the Suwannee Valley and interior southeast Georgia will likely increase in coverage this afternoon as activity pushes slowly southeast or southward. Additional activity will develop closer to the terminals along the inland moving Atlantic sea breeze after 20Z. Colliding boundaries should increase the coverage and intensity of convection near the Duval County terminals and SSI after 21Z, and we have included TEMPO groups for brief surface wind gusts up to 30 knots and IFR visibilities during heavier downpours through around 02Z this evening. Confidence for impacts at GNV and SGJ remains lower, but we maintained a PROB30 group at GNV for brief surface wind gusts up to 30 knots and IFR conditions during heavier downpours through around 00Z. A PROB30 group was added at SGJ after 23Z for brief surface wind gusts up to 25 knots and MVFR conditions during heavier downpours. VFR conditions should then prevail at the regional terminals by 04Z Tuesday. Southeast to southerly surface winds of 10- 15 knots will prevail at the SSI and SGJ coastal terminals through around 23Z. The Atlantic sea breeze boundary will progress slowly inland across the Duval County terminals after 20Z. Otherwise, south to southwesterly surface winds sustained around 5 knots are expected at the regional terminals through the TAF period.

MARINE

A stalled frontal boundary positioned just north of the Georgia waters will remain in place during the next several days. Afternoon and evening thunderstorms developing over coastal locations will push across our local waters each day, with strong to isolated severe storms possible through midweek. Stronger storms will be capable of producing strong wind gusts, frequent lightning strikes, and torrential downpours. 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.

Rip Currents: Although surf heights are low, generally in the 1-2 foot range, a persistent long period easterly ocean swell will combine with gradually strengthening onshore winds following the passage of the sea breeze this afternoon and again on Tuesday afternoon to create a lower end moderate risk at all area beaches. This pattern may continue during the next several days.

FIRE WEATHER

- Patchy high dispersions inland Southeast GA Thursday.

A fairly persistent pattern with high pressure over FL, and a frontal zone across SE GA will continue this period. Daily rounds of showers and thunderstorms are forecast, mainly in the afternoon and evening hours.

Fog Potential: Significant fog is unlikely. Gusty and erratic winds can be expected in and near thunderstorms.

PRELIMINARY POINT TEMPS/POPS

AMG 74 94 72 93 / 40 80 30 60 SSI 80 91 76 90 / 50 60 40 50 JAX 75 92 72 91 / 60 80 30 70 SGJ 76 91 74 90 / 40 60 30 50 GNV 75 91 71 92 / 40 70 20 50 OCF 75 91 73 93 / 30 60 20 40

JAX WATCHES/WARNINGS/ADVISORIES

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