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

- Medium chance (40%) of a tropical development in the northeastern Gulf through Tuesday.

- Scattered afternoon thunderstorms this weekend followed by expanding coverage by Monday with increasing potential for heavy rain and localized flooding, mainly for west of I-75 corridor.

- Moderate Rip Current Risk today and Sunday

- Heat Advisory Conditions Possible Towards the Middle of Next Week

NEAR TERM /THROUGH TONIGHT/

Main Highlights This afternoon and Tonight:

- Seasonably Hot and Humid Summertime Weather Continues.

- Scattered thunderstorms with isolated strong storms possible for Suwannee River Valley and inland Southeast GA.

Low level steering flow will trend southerly and then southwesterly through the afternoon as the Bermuda high extends an axis across southern FL and the mid/upper low off the west coast of FL migrates north-northwestward. Generally southerly flow will keep the Atlantic sea breeze from pushing as far inland this afternoon. Overall, convective coverage will be limited across most of NE FL this afternoon into evening as a dry pocket of air (PWATs 1.5-1.7 in) wraps around the base of the upper low and advects northward into NE FL generally east of I-75 and up to the SE GA coast. Though the dry pocket will curtail instability, there should be sufficient moisture (PWATs ~2 in) across interior areas of SE GA and the northern tier of the Suwannee River valley to support scattered thunderstorm development this afternoon into evening. A few showers and possibly an isolated thunderstorm may develop this evening along outflow produced by convection across central FL into the north-central FL zones. A few showers may linger over the Altamaha/Ocmulgee river basins tonight as some shortwave energy associated with the upper low rotate through southern GA.

With the Atlantic sea breeze being pinned, temperatures will be hotter for communities closer to the coast today with highs into the mid 90s. The beaches should still feel the cooling sea breeze, limiting highs to the low 90s. Heat index values will generally peak in the 100-107 degree range once again. Overnight lows will be in the 70s.

Additionally, satellite images and surface observations indicate that a broad surface low is forming in the northeastern Gulf beneath the mid/upper low. This low remains a potential candidate for tropical/subtropical development with a 30% chance of developing in the next 48 hours. Please continue to monitor for updates on this system.

SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/

Main Highlights This Period:

- Bouts of Showers and Storms & Heavy Rainfall, Especially for Western Areas

The main focus for the forecast period continues to be the evolution and movement of an upper level low currently located over the eastern Gulf, in which the National Hurricane Center (NHC) currently gives a 20% chance of developing tropical characteristics through Monday. Model guidance has mostly continued to trend further north and west with the movement of the disturbance regardless of development, resulting the the highest forecast rainfall totals and therefore more concerns for localized flooding to be areas furthest west, such as near and west of the I-75 corridor and the Upper Suwannee River Valley, with more of an influence of drier air closer to the east coast. Still expecting enough of a sea breeze influence and just high enough layer moisture for chances for convection further east, however the heaviest rainfall potential and highest coverage is expected to be over western areas each day, especially as the east coast sea breeze makes progress inland. High temperature variance will be a bit different than usual with the system skirting the area, as highs will be mainly in the low 90s with some mid 90s likely over inland north/central FL and southeast GA.

LONG TERM /TUESDAY THROUGH SATURDAY/

Main Highlights This Period:

- Scattered to Numerous Afternoon Thunderstorms - Potential heat advisory conditions by the middle of next week

The upper level disturbance in the Gulf is expected to weaken while drifting northwestward Tuesday and into mid week, with low to mid level ridging building over the FL peninsula by Wednesday. A frontal boundary is forecast to drop southward towards the area Wednesday Night and Thursday before likely slowing an stalling, bringing plenty of moisture with it and therefore more numerous convective chances for much of the long term period. Temperatures overall trend near to slightly above normal for Tuesday - Friday.

AVIATION /18Z SATURDAY THROUGH 18Z SUNDAY/

Chances for showers continue to lower. Have removed VCSH from all sites except GNV for this afternoon. Otherwise, south- southwesterly wind 5-10 kts will prevail at TAF sites west of I-95. The Atlantic sea breeze will gradually shift winds to south-southeasterly across KSSI, KSGJ and KCRG at around 10 knots.

MARINE

Bermuda high pressure will extend a ridge axis across southern Florida today, shifting winds southerly across the local waters today. As winds shift they will strengthen to Exercise Caution levels between a trough over the southeastern US and the ridge axis to the south. Drier air moving into the coastal waters will limit thunderstorm potential through the weekend and possibly into next week.

There's greater uncertainty in the forecast next week regarding the potential for tropical development in the northeastern Gulf. That system is now more likely to drift northwest through the first half of next week. For the second half of next week, a prolonged offshore flow is likely to remain in place with nocturnal southerly wind surges as a cold front approaches from the northwest.

Rip Currents:

There will be a moderate risk for rip currents this afternoon as surf elevates to 2-3 feet and flow shifts to SSE. Surf heights will relax some Sunday but a moderate risk is still expected during the afternoon.

FIRE WEATHER

An increase in moisture and southerly winds is expected over the next several days as an upper level low spins in the eastern Gulf, slowly drifting north and west through early next week. The National Hurricane Center gives this low a 20% chance of developing tropical characteristics over the next 48 hours, though impacts to our area area expected to be limited outside of bands of showers and thunderstorms affecting the area at times during daytime heating. Otherwise, the increase in flow will result in good dispersions for most, with the main exceptions being near the immediate coast and west of about I-75 in northeast FL where dispersions will be slightly lower thanks to more cloud cover. The low weakens by mid next week, with a frontal boundary dropping southward towards the region.

Fog Potential and Other Remarks: Significant fog development is not expected for the next several nights. Gusty and erratic winds will be possible in and near thunderstorms, with occasional outflow boundaries capable of producing sudden wind shifts well away from ongoing convection.

PRELIMINARY POINT TEMPS/POPS

AMG 74 94 74 93 / 30 20 10 50 SSI 79 93 80 92 / 10 10 10 40 JAX 76 94 77 93 / 10 20 10 50 SGJ 76 92 77 92 / 10 20 10 50 GNV 74 92 74 91 / 10 30 30 60 OCF 74 91 75 91 / 20 40 40 60

JAX WATCHES/WARNINGS/ADVISORIES

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