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

- Waves of Scattered to Numerous Thunderstorms This Afternoon and Evening. Isolated Storms Capable of Gusty winds (30-45 mph), Frequent Lightning, and Torrential Downpours.

- Heavy Downpours may leadto areas of flooding. Strongest Storms Likely Along the I-95 Corridor during the late afternoon and early evening.

- Scattered to Numerous Afternoon and Evening Thunderstorms from Thursday through the Upcoming Weekend.

- Moderate Rip Current Risk Continues at All Area Beaches.

NEAR TERM /THROUGH TONIGHT/

Highlights through Tonight:

- Isolated strong thunderstorms with locally gusty winds and heavy downpours are expected late this afternoon and evening.

A wavy stalled frontal zone remains to the north today while troughing exists aloft. Similar to yesterday, a mellow low level steering flow will favor a southwesterly direction through most of the day, which will pin and slow the Atlantic sea breeze as it develops.

There appears to be a higher chance of more isolated coverage during the morning and early afternoon hours across eastern and southern zones of NE FL as a wedge of drier air over the eastern Gulf advects northward. Further north, high precipitable water (2"+) will fuel convection across SE GA and the Suwannee River valley early in the day, with thunderstorms developing along the Big Bend and pushing into the Suwannee River during the late morning hours. As more deeper moisture builds and outflows from the west begin to interact with the Atlantic sea breeze during the late afternoon and early evening scattered thunderstorms will develop and likely propagate southwestward as storm-relative inflow trends southerly. With the loss of daytime heating, there will be a quick decline in thunderstorm activity this evening.

Primary concerns with today's storm activity will be gusty outflow winds and locally heavy rainfall which may lead to flooding, particularly in low-lying, poor-drainage, or generally flood-prone locations.

Temperatures will have more time to heat up today, especially across NE FL and North Central FL, with highs pushing into the low 90s. The earlier start to convection for the Suwannee Valley and north into SE GA will limit todays highs to the upper 80s or right at 90 degrees due to the rain-cooled air and mostly cloudy conditions. Overall this will keep heat index in the upper 90s to low 100s this afternoon. A standard mild, muggy night will follow todays typical August heat as temperatures fall to the low 70s.

SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/

Main Highlights This Period:

- Chance for a isolated strong to severe storms each afternoon and evening on Thursday and Friday.

Summertime pattern for diurnal bouts of showers and thunderstorms will continue through the end of the week as a prevailing southwesterly flow remains in place between the frontal zone to the north and high pressure ridging extending over Florida from out of the east. Daytime high temperatures will be in the lower 90s for inland areas on Thursday and Friday, with max temps in the upper 80s and lower 90s along the coast. Overnight low temperatures will drop down into the lower 70s over inland areas and in the mid 70s for areas along the coast and near the St Johns River. Heat index values will rise to be over 100 during this period with a potential for some areas to reach heat advisory levels on Wednesday. The passage of upper level short waves through this period could lead to stronger thunderstorm developments in the afternoon and evening hours.

LONG TERM /SATURDAY THROUGH TUESDAY/

Main Highlights This Period:

- Chances For Isolated Strong to Severe Storms Continues Each Afternoon and Evening.

Prevailing flow will shift about to become more out of the southwest and west by the end of the weekend and into next week as the frontal zone to the north becomes less defined and high pressure builds in closer to the southeast US. Otherwise, the pattern for diurnal showers and storms will remain fairly consistent through the period with the potential for stronger storms occurring with possible passing upper level short waves. Temperatures will trend slightly above average through the weekend and into the beginning of next week with daily high temperatures reaching into the lower 90s. Heat index values will rise to be over 100 during this period but are expected to remain below heat advisory criteria each day.

AVIATION /12Z WEDNESDAY THROUGH 12Z THURSDAY/

MVFR conditions will prevail through around 14Z at GNV and VQQ due to low stratus ceilings and/or light rainfall. Otherwise, VFR conditions will prevail at the regional terminals through at least 20Z. Extensive multi-layered cloud cover today should delay development of convection until around 21Z at the regional terminals. Confidence was high enough to include a TEMPO group for brief surface wind gusts up to 25 knots and IFR visibilities during heavier downpours through around 00Z at SSI, with MVFR visibilities indicated in TEMPO groups through around 01Z at the Duval County terminals and SGJ. Confidence remains too low for a TEMPO group at GNV, where a PROB30 group was maintained for brief surface wind gusts around 25 knots and MVFR visibilities during heavier downpours through around 01Z. PROB30 groups were added for the potential for late evening and overnight convection at SSI and the Duval County terminals, where MVFR conditions will be possible during heavier downpours through around 06Z Thursday. VFR conditions will then prevail after 06Z, except at VQQ, where MVFR visibilities will be possible during the predawn hours. Southerly surface winds at the regional terminals this morning will remain sustained around 5 knots. The Atlantic sea breeze will develop towards 17Z and will progress inland this afternoon, shifting surface winds to southeasterly around 10 knots at SGJ and southerly around 10 knots at SSI by 18Z. Surface winds should shift to southeasterly at 5-10 knots towards 20Z at the Duval County terminals. Light southeasterly surface winds will resume at the regional terminals after 00Z outside of potential redevelopment of convection.

MARINE

A stalled frontal boundary positioned just north of the Georgia waters will remain in place during the next several days. Thunderstorms developing over coastal locations will push across our local waters through the upcoming weekend, mainly during the late afternoon and evening hours, with strong to isolated severe storms possible. 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. Stronger high pressure building over New England this weekend will shift prevailing winds to onshore across our local waters.

Rip Currents: Following the sea breeze a lower end Moderate Risk is expected at all area beaches each afternoon during the next through the end of the week.

FIRE WEATHER

A frontal zone will remain nearly stationary across southern GA through the end of the week, persisting elevated chances for showers and thunderstorms each day, mainly during the daytime hours. Weak high pressure ridging across and just south of the region will keep the flow direction generally out of the south to southwest, with winds peaking during the evening and overnight hours. Another frontal boundary drops southward towards area waters this upcoming weekend, maintaining an active pattern.

Fog Potential: Significant fog is unlikely over the next several days. Gusty and erratic winds can be expected in and near thunderstorms.

PRELIMINARY POINT TEMPS/POPS

AMG 91 72 92 72 / 60 30 60 30 SSI 88 76 89 76 / 40 20 50 30 JAX 91 72 91 72 / 50 30 60 20 SGJ 90 73 90 74 / 50 20 50 20 GNV 90 71 91 72 / 30 30 60 20 OCF 92 72 91 72 / 40 40 70 20

JAX WATCHES/WARNINGS/ADVISORIES

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