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

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

- Moderate Rip Current Risk all Local Beaches Today through the weekend. Elevated Risk Returns Next Week

- Daily Heat Index up to 107 Each Afternoon through Sunday

NEAR TERM /TODAY THROUGH TONIGHT/

Main Highlights:

- Potential for isolated strong thunderstorms and localized flooding.

- Moderate Rip Current Risk at All Area Beaches.

Mean layer ridge oriented more or less west-east through 700 mb is located in central FL area. Typically, for September, this ridge is located further north. Deep layer flow is southwesterly at about 10 kt, and we continue with the deep moisture in place with the 18z JAX Sounding showing a PWAT of 2.29 inches and 500 mb temp of only -4.1C. Fairly confident PWATS will stay the same today, but the 500 mb temps may drop another degree or so during the day. Models suggest that some shortwave energy may impinge on the forecast area after 21z today which will likely encourage more cloudiness and probably boost rain chances this evening.

Given the moisture and summer-like pattern, we anticipate scattered to numerous showers and storms to develop during the day. Initial development of convection likely to be around any lingering boundaries from Thursday, and also along the west and east coast sea breezes that develop by the early afternoon. Climatology would suggest the I-75 corridor first near the developing west coast sea breeze. The movement of the west coast sea breeze may meet the east coast sea breeze this afternoon and early evening, and cells mergers may would be near and east of the U.S. Highway 301 area. The moisture-laden airmass will be efficient for heavy rainfall/localized flooding. Isolated rain amounts in excess of 3 inches in spots are likely. The DCAPE on the model soundings looks unimpressive at about 500-600 J/kg, similar to yesterday, so for now assuming peak tstorm gusts of about 40-50 mph. Cannot totally rule out an isolated severe storm though where strongest convergence occurs. Scattered showers and storms expected in the evening and will fade overnight. Patchy fog again is possible this morning and early Saturday morning.

Daytime highs will be in the lower 90s, and probably around 90 at the east coast as the sea breeze develops. Heat index values will hover under Heat Advisory criteria, with values in the upper 90s to around 105F. Lows tonight in the lower to mid 70s.

SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/

Main Highlights This Period:

- Potential for isolated strong thunderstorms and localized flooding on Saturday

Scattered to numerous showers and storms are anticipated on Saturday as moist southwesterly flow, with PWAT values of 2 to 2.3 inches, continues to move over the region from out of the Gulf. There is a potential for heavy rains and localized flooding for storms developing along the sea breeze boundaries and areas of convergence, likely along and west of the I-95 corridor. Convection is expected to be less widespread on Sunday as the high pressure ridge shifts northward and crosses over the forecast area, with the prevailing flow gradually shifting to a more northeasterly onshore flow by the beginning of next week. High temperatures will rise up into the lower 90s this weekend with overnight low temperatures dropping down into the lower to mid 70s over inland areas and int the mid to upper 70s for areas along the coast. Heat index values today will rise to over 100 with apparent temperatures potentially reaching as high as 110 for northeast Florida, however conditions are anticipated to remain below heat advisory criteria. Potential for patchy early morning fog and low cloud decks over inland areas before and around sunrise during the overnight and early morning hours this weekend.

LONG TERM /MONDAY THROUGH THURSDAY/

Main Highlights:

- Daily Thunderstorms Potential Each Day Next Week

- Elevated Rip Current Risk Next Week

Northeasterly onshore flow will be in place through the latter part of next week as the axis of high pressure rotation settles in to the north. Chances for daily bouts of showers and storms will lessen for southeast Georgia and areas of northeast Florida north of the I-10 corridor as drier air advects into the forecast area from out of the northeast, with a higher likelihood of convection for areas south of I-10. Above average high temperatures reaching into the lower 90s will gradually drop down into the upper 80s and be nearer the seasonal average by midweek. Heat index values will drop down to be below 100.

Rip current risk will also become elevated rather than moderate as a result of the pattern shift.

AVIATION /06Z FRIDAY THROUGH 06Z SATURDAY/

VFR clouds have returned to the area with all the showers done tonight. Light winds may allow for some cigs and vsby restrictions for VQQ and possibly GNV through 12Z.

Active convective day again with scattered to numerous showers and storms for all terminals this afternoon. TEMPO and PROB30 groups are in place for MVFR/IFR TSRA activity from 18-22Z, and little later for SSI. Expecting scattered TSRA at 22z so have continued some mention for TS through 02z Saturday. Movement of TSRA will be northeast up to around 10-15 kt. Convection will be winding down in the 02Z to 05Z time frame. Southwest winds near 4-8 kt expected to turn southeast for CRG, SGJ, and SSI after 16-18Z.

MARINE

Atlantic high pressure ridge will be centered from Bermuda to central Florida through early next week. This will favor prevailing southwest to south winds the next few days but the afternoon sea breeze will shift winds to southeast each afternoon across the near shore waters. Thunderstorms will likely develop over coastal locations during the afternoon hours will shift eastward across our local waters during the late afternoon and evening hours through the weekend. Onshore winds are forecast to develop Tuesday, with breezy conditions and building seas forecast towards Tuesday and Wednesday of next week.

Rip Currents: Generally offshore flow and weakening surf conditions suggest continuing a moderate risk today, with a lingering 2 foot wind-sea swell of about 7-8 seconds. This trend continues into the weekend likely maintaining a low to moderate risk. An increased threat of dangerous rip currents possible on Tuesday into Wednesday.

FIRE WEATHER

Diurnal southwesterly winds will persist through the end of the week and through the weekend. As a result of the moist southwesterly flow, the diurnal east coast sea breeze will be pinned near the shoreline and not reach inland much past the I-95 corridor. Flow pattern is expected to shift to become more onshore by the beginning of next week.

Fog Potential: Gusty and erratic wind shifts will occur from thunderstorm activity. Patchy fog is expected across inland areas the next couple of mornings, with widespread dense fog unlikely.

HYDROLOGY

As far as coastal water levels, coastal water levels will remain near and below action stage despite the new moon phase today.

As far as rainfall again today, isolated pockets of up to 3-4 inches are possible mainly the St Johns River Basin northward to near or just south of Waycross and Nahunta. These storms may cause temporary flooding, especially in any poor drainage or urbanized areas.

PRELIMINARY POINT TEMPS/POPS

AMG 91 73 91 73 / 30 20 50 20 SSI 90 77 89 76 / 30 20 50 20 JAX 91 74 91 74 / 60 30 70 10 SGJ 90 75 90 75 / 70 30 60 10 GNV 91 73 91 73 / 60 20 70 20 OCF 92 74 92 74 / 60 20 70 20

JAX WATCHES/WARNINGS/ADVISORIES

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