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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

- Hot and Humid Today - Peak Heat Index Values: 103- 109

- Afternoon & Evening TStorms Area-Wide Through Most of. Scattered to Numerous Thunderstorms this afternoon (2 PM 9 PM). Strong Storms with Gusty Winds, Frequent Lightning Strikes & Heavy Downpours I-95 & I-10 corridor and all of SE GA this afternoon

UPDATE

Not much change to the ongoing forecast with hot and humid conditions today with most recent JAX sounding showing PWAT of near 2 inches. This value is about 125-130 percent of normal. Prevailing westerly flow from sfc through 6 km was 280 deg at 20 kt on the 12z sounding, and rich mean mixing ration of 17.1 g/kg.

Seeing old boundary laying out across northeast FL in radar imagery this morning where there are a couple of little showers starting to develop, but very early in the day so far for anything significant. Not seeing much in the way of convective inhibition over northeast FL at 9 AM. The POPs forecast look on track and did not change the high POPs today of upwards of 60-80 percent. Latest guidance on track for the highest rain chances in a broad zone from about St Johns/Flagler to the Suwannee Valley area throughout the day and into the evening hours. Given the orientation of the zone and the near parallel flow aloft, some training of convection is possible today. Expect that some 2-4 inch rain amounts are possible but should be pretty isolated in that range. Temps aloft are about -5 to -6C at 500 mb, but may cool slightly this afternoon per latest RAP. Given that the airmass remains on the moist side, the probability of an isolated severe downburst looks a bit lower than the past couple of days. Nonetheless, pockets of strong heating and water loading may support a couple of storms with gusts over 50 mph.

Max temps still in the lower 90s today with heat indices touching heat advisory criteria in a couple of areas, but not widespread enough for an advisory and enhanced/early onset of precip will help limit high heat indices.

NEAR TERM /THROUGH TONIGHT/

Main Highlights This Period:

- Another Hot Day with Heat Index Peaking Around 102-107 Degrees

- Scattered to Numerous Afternoon Thunderstorms, A Few Strong to Isolated Severe Storms Possible, with locally heavy rainfall

Convection has come to an end early this morning, and guidance has overall backed off with respect to convection potential with a pre frontal trough moving towards the area from the northwest overnight. A few showers and perhaps a thunderstorm cannot be ruled out from about the 2am to 6am time frame, especially across southeast GA. However, these chances are generally less than 20%.

Otherwise, no significant chances to the forecast and overall regime as compared to the last few days, as warm and moist southwest flow continues at the low levels with a general west to northwest steering flow aloft. A frontal boundary well to our north will drop a bit further south throughout the day today, in which the main impact will be a little bit of additional lift to aid in the shower and thunderstorm coverage. Expecting a fairly similar outcome as compared to Sunday with respect to timing and coverage, as some activity will fire over northeast FL to start late morning into around midday with the Gulf sea breeze before filling in north and west into the afternoon. Convergence of sea breezes and outflows will once again be the main factor behind any strong to isolated severe potential, but shortwave energy aloft along and south of the frontal boundary will also aid in this potential. PWATs will once again be in the 2+" range, and therefore isolated minor flooding is possible as well in addition to the "usual" wind gust potential up to around 40-60mph, though storm motion looks to be fast enough for anything more than a slight risk of flooding in more flood prone areas.

Similar to Sunday, the southwest flow will bring hot and humid conditions, though earlier convection onset will limit high temps "only" to the low to mid 90s for most. Heat indices will flirt with heat advisory criteria, overall averaging in the 102-107 range. Convection mostly comes to an end from about 8-9pm onward, though most guidance is suggesting the chances for a few showers and perhaps an isolated thunderstorm continues over interior GA overnight, especially towards early Tuesday Morning, and closer to the nearly stationary boundary. Low temps will be mild, in the low to mid 70s once again.

SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/

Main Highlights This Period:

- Locally heavy rainfall possible both afternoons - Potential for isolated strong to severe thunderstorms - Greatest storm coverage expected on Wednesday

A moist and increasingly unsettled summertime pattern will persist through the short-term period as a cold front gradually settles southward toward the region. Deep tropical moisture, ample instability, and increasing low-level convergence along the boundary will support scattered to numerous showers and thunderstorms each afternoon and evening.

On Tuesday, the frontal boundary will sag into central Georgia while persistent southwesterly flow aloft remains strong enough to keep the Atlantic sea breeze pinned near the immediate coastline. This setup will allow temperatures to climb into the lower 90s across coastal areas before convection develops over inland locations and gradually shifts eastward through the afternoon and evening. Precipitable water values will remain well above seasonal normals, with the potential for locally heavy downpours. Areas that receive multiple rounds of thunderstorms could experience localized flooding concerns. In addition, a few stronger storms may produce frequent lightning, gusty winds, and isolated severe wind gusts. High temperatures will generally range from the 80s inland SE GA, upper 80s to the lower 90s inland NE FL to near 90 along the coast, with overnight lows settling into 70 to 75 degree range SE GA and lower to mid-70s NE FL and coast.

By Wednesday, the front is expected to stall across southeast Georgia, providing a persistent focus for convective initiation and organization. Combined with continued deep tropical moisture and strong daytime heating, this pattern should support the greatest coverage of showers and thunderstorms during the short-term period. Scattered to numerous thunderstorms are expected during the afternoon and evening hours, with locally heavy rainfall remaining the primary hazard. Given the favorable thermodynamic environment, a few storms could become strong, with isolated damaging wind gusts possible. Increased cloud cover and more widespread precipitation should temper daytime heating somewhat, keeping afternoon highs mainly in the mid to upper 80s north of SR16 and in the lower 90s south of SR16.

Overall, temperatures will remain near to slightly above seasonal normals through midweek, while elevated humidity levels and daily thunderstorm chances continue across the region. The primary hazards will be locally heavy rainfall, frequent lightning, isolated strong wind gusts, and localized flooding in areas that experience repeated rounds of convection.

LONG TERM /THURSDAY THROUGH SUNDAY/

Main Highlights This Period:

- Daily afternoon and evening thunderstorms continue - Locally heavy rainfall and isolated strong storms remain possible - Rain chances increase again next weekend

A weakening frontal boundary will linger across the region Thursday and Friday, gradually losing definition but leaving behind a very moist and unstable airmass. This will support scattered afternoon and evening showers and thunderstorms each day. While convective coverage may be somewhat lower than earlier in the week, locally heavy rainfall, frequent lightning, and isolated strong wind gusts will remain possible with the strongest storms.

Persistent southwesterly flow will continue to inhibit the inland progression of the Atlantic sea breeze, favoring thunderstorm development along inland mesoscale boundaries during the afternoon and evening hours. Temperatures will climb into the lower and middle 90s both days, with peak heat indices generally reaching the 100 to 105 degree range before convection develops.

Forecast is also focused on a broad area of disturbed weather currently being monitored by the NHC over the NW Gulf of America. Considerable uncertainty remains regarding the evolution and potential development of this system. Regardless of tropical development, deep tropical moisture associated with this disturbance may surge northeastward into portions of southeast Georgia late this week, potentially pushing precipitable water values above 2 inches and enhancing low-level moisture transport, especially north and west of Waycross. This could result in an increased threat for heavy rainfall Thursday into Friday, although confidence in specific impacts remain very low at this time.

Attention then shifts to the weekend as another frontal boundary approaches from the north and stalls across the southeastern states. Increasing low-level convergence along the boundary, combined with a persistently moist airmass, will support above-normal rain chances Saturday and perhaps into Sunday depending on the timing of the front or its potential passage. Scattered to numerous showers and thunderstorms are expected each afternoon and evening, with locally heavy rainfall remaining the primary concern. Temperatures should remain near seasonal normals, with highs generally in the upper 80s to lower 90s.

Overall, the primary hazards through the extended period will be locally heavy rainfall, frequent lightning, isolated strong thunderstorms capable of producing gusty winds, and periods of elevated heat and humidity.

AVIATION /12Z MONDAY THROUGH 12Z TUESDAY/

IFR stratus clouds could affect some of the northeast FL TAFS and possibly SSI but they should disperse over the next couple of hours. MVFR cigs will still be possible 13z-16z and could see a few showers nearing GNV by 14z-15z. Otherwise, breezy southwest to west flow is expected once again today, with convection spreading generally from southwest to northeast and PROB30/TEMPO included for all airfields once again. Convection is expected to wane after 00Z as mostly mid and high clouds linger. Sfc winds become west-southwest (from near 240-270 deg) about 8-12 kt, but then may back to the southwest (220- 240 deg) for a time at SSI, CRG, and SGJ after 18z/19z. Expect variable and gusty winds near and in any thunderstorm activity.

MARINE

The region will be between high pressure to the south southeast, and a frontal zone stalling just north of the local waters through most of the upcoming week. This will lead to a predominant southwest flow which will become breezy at times, with periods of Small Craft Exercise Caution conditions, mainly over the offshore waters. The offshore flow will continue to push strong storms with gusty winds and frequent lightning into the coastal waters through the period. The frontal zone will weaken mid week which will likely limit showers and thunderstorm activity before another frontal boundary drops southward late week.

Rip Currents:

Generally a low risk of rip currents continues early this week as surf remains only in the 1-2 ft range in the predominant offshore flow. This trend is likely to continue through mid week as well.

FIRE WEATHER

- Patchy to areas of high daytime dispersion values this week - Daily showers and thunderstorms expected

A series of frontal boundaries interacting with a warm, moist, and unstable airmass will maintain above-normal chances for showers and thunderstorms through much of the upcoming week and into next weekend. Periods of locally heavy rainfall, frequent lightning, and gusty winds will accompany the stronger storms. Outside of convection, favorable transport winds and mixing heights will at times support patchy to widespread high daytime dispersion values. Temperatures are expected to remain near to slightly above seasonal normals throughout the period, accompanied by elevated humidity levels.

FOG POTENTIAL AND OTHER REMARKS: Significant fog is not expected this morning. Daily showers and thunderstorms are expected through the period, with the greatest coverage occurring during the afternoon and evening hours. Some storms may become strong, producing gusty and erratic winds, frequent cloud-to-ground lightning, and locally heavy rainfall that could result in brief reductions in visibility. Areas that receive heavier rainfall may also experience patchy late-night and early-morning fog development due to increased low-level moisture and light winds.

PRELIMINARY POINT TEMPS/POPS

AMG 92 72 82 70 / 80 60 80 70 SSI 93 76 88 75 / 70 50 70 50 JAX 93 75 91 73 / 80 50 70 30 SGJ 93 76 92 75 / 70 50 70 30 GNV 92 75 91 74 / 40 30 40 30 OCF 91 77 91 76 / 30 10 30 30

JAX WATCHES/WARNINGS/ADVISORIES

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