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

- Moderate Rip Current Risk all Local Beaches Today and Friday. Elevated Risk Returns Early Next Week

- Daily Heat Index up to 107 through Sunday

- Daily Afternoon & Evening Thunderstorms. Main Hazards: Locally Heavy Rain, Lightning & Gusty Winds Up to 40-50 mph

NEAR TERM /TODAY THROUGH TONIGHT/

Main Highlights:

- Potential for a few strong thunderstorms and localized flooding.

- Moderate Risk of Rip Currents Today

- Patchy Dense Fog This Morning

Some patchy fog early this morning inland areas, and can't rule out brief locally dense fog over inland southeast GA. Already seeing areas of low stratus in southeast GA so not a stretch to see a period of lower vsby there. Meanwhile, the pattern for today will pivot fairly quickly back to a southeast to south flow from 1000-700 mb as low level ridging moves offshore of the southeast states. A weak boundary, probably remnants of a frontal zone, will lift northward over the area today while dissipating, and be positioned near the Altamaha River Basin by about 2 PM. The airmass remains moist with PWATs of just over 2 inches per the 18z JAX RAOB, with NAM and other guidance showing values near 2.25 inches this afternoon. This moisture and daytime heating should result in MLCAPE of up to about 2500 J/kg, though deep layer shear remains weak. Isolated strong thunderstorms are still expected with gusty winds to about 40-50 mph and locally heavy rainfall. Max estimated max rainfall amounts may be near 4 inches in some spots. The more robust thunderstorms should be inland mainly near the U.S. Highway 301 corridor. Movement of the cells should be northerly about 10 mph by the afternoon. Isolated to scattered showers and storms expected this evening, but should dissipate through midnight as instability wanes. Patchy fog may develop once again late tonight inland areas.

Temperatures will trend above average with highs in the lower 90s for most inland locations to upper 80s to near 90 at the coast. Peak heat index values will reach to about 106 or so today. Muggy overnight lows will range in the lower/mid 70s.

SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/

Main Highlights This Period:

- Daily potential for isolated strong thunderstorms and potential for localized flooding.

Southwesterly to southerly steering flow will be in place through the period, bringing Gulf moisture across NE FL and SE GA as PWATs rise to above 2.25". The steering flow will allow for the Gulf breeze to move well inland each afternoon, with mergers with the Atlantic sea breeze occurring between the US-301 corridor towards the I-95 corridor. With the elevated moisture aloft, showers and storms that do develop could bring periods of locally heavy rainfall. Isolated strong storms, maybe a few severe storms, could bring gusty winds in the 30 to 50 mph range.

Daytime highs will be in the 90s along inland locations on Friday and Saturday with highs in the upper 80s to lower 90s along the coast. Overnight Lows will be in the lower to mid 70s. Heat index values will hover just under Heat Advisory criteria, with values in the upper 90s to around 107F.

LONG TERM /SUNDAY THROUGH WEDNESDAY/

- Above Average Temperatures & Daily Thunderstorms this Weekend

- Elevated Rip Current Risk Next Week

Relatively stubborn pattern will develop over the weekend and through next week as deep ridging becomes stacked well offshore. Initially over the weekend this positions a lower level ridge axis directly across the local area, resulting in a weak southerly flow regime. The Gulf and Atlantic coast seas breezes are expected to push inland and trigger showers and storms as the breezes merge across inland areas during the late afternoon and into the evening. By Monday, the ridge axis moves north, reintroducing onshore flow early next week. The primary concerns each day will be localized potential for strong thunderstorms due to mesoscale boundary collisions with the potential for localized rainfall and flooding concerns. With the return of easterly winds next week, local rip current risk will also become elevated once again.

Temperature highs in the 90s will begin to decrease into the middle of the upcoming week, with highs in the mid to upper 80s as easterly flow returns on Tuesday. Lows will continue to range in the 70s.

AVIATION /06Z THURSDAY THROUGH 06Z FRIDAY/

A couple of showers are expected around SSI through about 11z for SSI, but main impacts through early this morning will be periods of MVFR and IFR cig and vsby especially at VQQ and GNV. After any stratus dissipates, weak isolated convection may develop around the east coast terminals from about 15z to 17z, with scattered to numerous showers and storms thereafter. Given the environment, have gone with PROB30 and TEMPO groups this afternoon for MVFR vsby in TSRA. As confidence increases, PROB30 groups may be upgraded to TEMPO groups. Showers and storms will become widely scattered after 00z. For Sfc winds, light and variable, will become south about 4-6 kt, and become southeast near 10 kt for JAX, SSI, CRG, and SGJ, more south-southwest for VQQ and GNV at 4-7 kt.

MARINE

High pressure stretching across Georgia and the Carolinas will gradually weaken while shifting south through the weekend. Meanwhile, a cold front will move into the Ohio and Tennessee Valleys by Friday and move toward the area waters early next week.

Rip Currents: Diminished winds and dropping surf will tend to lower the rip current risk toward the moderate range today. Prevailing winds will become south-southwesterly by Friday, with a lingering easterly ocean swell and onshore winds developing during the afternoon hours behind the inland moving sea breeze keeping a lower-end moderate risk at area beaches.

FIRE WEATHER

Winds will steadily veer to become southerly to southwesterly Today. This will allow for the Gulf Coast and Atlantic Coast sea breezes to push inland by the afternoon hours, with showers and storms developing and increasing in coverage near Highway 301. As weaker transport winds develop, Dispersions will be Fair for most of the time over the next few days. Otherwise, RH values will sit at Good levels through the weekend as moisture moves in from the Gulf and towards southeast Georgia and northeast Florida.

Fog Potential: Gusty and erratic wind shifts will occur from thunderstorm activity. Patchy fog is expected across inland areas this morning, with widespread dense fog unlikely.

HYDROLOGY

As far as coastal water levels, we expect tidal water levels to peak to near the Action stage through Friday due to the recent onshore flow but mainly due to the new moon phase which is Friday, Sept 11th. Mostly nuisance type flooding is expected for a brief time into the weekend, including in the St Johns River Basin.

As far as rainfall today, isolated pockets of about 4 inches are possible mainly across an area from eastern Marion county northward to around Baker county. These storms may cause temporary flooding, especially in any poor drainage or urbanized areas.

PRELIMINARY POINT TEMPS/POPS

AMG 92 73 92 73 / 40 30 60 20 SSI 89 77 90 77 / 30 20 50 40 JAX 91 74 91 74 / 40 20 80 20 SGJ 89 75 90 75 / 40 30 80 20 GNV 92 73 91 73 / 50 20 80 20 OCF 92 74 91 74 / 40 20 80 10

JAX WATCHES/WARNINGS/ADVISORIES

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