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

- Scattered to Numerous Thunderstorms through the Weekend. Numerous Showers and Thunderstorms Today. Isolated Strong Storm Potential Each Afternoon and Evening. Heavy Downpours May Cause Localized Flooding this Weekend.

- High Risk of Rip Currents at All Area Beaches Today. Moderate Risk of Rip Currents at All Area Beaches Sunday.

- Extreme Heat returns next week with Heat Indices around 110F. Heat Advisories possible each day from Tuesday through Friday.

NEAR TERM /THROUGH TONIGHT/

Main Highlights:

- Heavy Downpours and Isolated Strong Storms Possible Today, with a Localized Flood Threat this Afternoon through Early this Evening.

- High Risk of Rip Currents at Area Beaches Today.

A broad, surface trough of low pressure extends northeast from over the eastern Gulf to our forecast area and to the GA and SC coasts early this morning. This feature will lift to the northwest today and tonight while weak sfc ridge attempts to build over the central FL peninsula. The deep layer flow over the region will start out from the southeast about 10-15 kt, and veer to southerly by late today. Latest satellite derived PWAT imagery at 2 AM shows high values generally from about 2 inches to 2.3 inches, though there is some drier air over inland southeast GA below 1.7 inches northwest of a line from Baxley to Douglas. Given the steering flow changes, widespread PWATs of 2.1 to 2.4 inches are expected to develop through the day.

With weak convective inhibition and the trough feature, scattered showers and some storms will be over the marine waters and brushing the coastal areas early this morning. Expect that showers and storms will continue to move in from the Atlantic, and also forming along the east coast sea breeze, through the day and increase in coverage. It won't take much time for this deep convection to form this morning given the abundant moisture and low level convergence. The potential exists for an isolated strong to severe thunderstorm this afternoon and evening, but the main threat will be lightning and localized flooding rainfall. Regarding the localized flooding threat, HREF and REFS show a few pockets of 3-5 inches in a few spots. Hourly rain rates could easily be 2-3 inches per hour in some storms, which will cause a higher concern in urban areas and poor drainage locations.

Precipitation will slowly end this evening inland, but the trough in the vicinity and the moist airmass may keep a low threat of showers for the coastal areas, but especially the marine waters through the night.

With the onshore flow, highs will range from the mid/upper 80s at the coast, the lower 90s further inland. Lows in the middle 70s will be common Tonight, except upper 70s along the coast.

SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/

Main Highlights This Period:

- Isolated strong to severe thunderstorms each afternoon and evening. Sunday, mid/upper level Atlantic ridge will shift southward over the western Atlantic waters as a weak shortwave associated with an upper level low/surface trough exits NE along the Carolina coast. Light southerly flow in the low levels will allow both the Atlantic/Gulf seabreezes to merge inland and along with high moisture levels remaining in the wake of the upper low/surface trough (PWATs 2.0- 2.25 inches) will support scattered T'storms becoming numerous inland as the o seabreezes/outflows merge. A few strong T'storms with gusty wet downburst winds up to 40-50 mph, frequent lightning, with brief locally heavy downpours. With the loss of heating, T'storms will wane after sunset.

Highs Sunday will be near to slightly above normal in the low/mid 90s inland and upper 80s to near 90 at the coast from decreasing clouds from the ridge and heat index values rising over 102-106. Lows will be in the mid 70s inland and the upper 70s along the coast Sunday night.

Monday, the ridge aloft over the Atlantic will shift south and west across the FL peninsula. Low level flow will trend more from the southwest direction around high pressure surface ridge axis extending across central FL from Bermuda and prevent the Atlantic seabreeze from pressing in much past I-95. Lower PWATs near seasonal levels of 1.6-1.9 inches will limit coverage of T'storms with isolated T'storms inland as the Gulf seabreeze advances across NE FL and scattered along I-95 as it merges with the Atlantic seabreeze. A few storms could be briefly strong.

Highs will rise Monday with low to mid 90s inland and near 90 along the coast. Heat index values will also rise to around 104-108 as dewpoints remain in the low/mid 70s inland and upper 70s along the coast, but will stay below heat advisory levels.

LONG TERM /TUESDAY THROUGH FRIDAY/

Main Highlights This Period:

- Scattered Afternoon and Evening Thunderstorms. - Heat Advisory Potential Returns.

Atlantic high pressure ridge will become more centered over the FL peninsula through midweek with a trough extending across the southeast states late in the week. The flow between the ridge over the region the trough will create light west southwest flow to persist over the area as the surface high pressure ridge axis stays across central FL. Drier air under the ridge will allow for strong diurnal heating while also suppressing convective coverage to isolated to widely scattered each afternoon as the Gulf seabreeze advances and merges with the Atlantic seabreeze near the NE FL coast.

Temperatures will be more of a concern next week, rising to the mid/upper 90s inland and low/mid 90s along the coast due to the offshore flow and Atlantic seabreeze remaining near/just offshore the beaches much of the afternoon. The above normal highs and dewpoints in the mid 70s inland and upper 70s at the coast will support peak heat indices into heat advisory levels of around 110 degrees Tuesday through next Friday. Lows will be slightly above normal in the mid 70s inland and upper 70s at the coast.

AVIATION /12Z SATURDAY THROUGH 12Z SUNDAY/

Periods of low MVFR ceilings of 1,000 - 2,000 feet will be possible through around 16Z at the regional terminals. Showers and thunderstorms developing over the near shore waters adjacent to southeast GA early this morning may impact the SSI terminal after 13Z, and we have inserted a PROB30 group through around 14Z for MVFR conditions during potentially heavy downpours. Please check for amendments this morning as convection approaches the SSI terminal. We expect that showers and thunderstorms will begin developing near the northeast FL terminals after 16Z, and we have included TEMPO groups for brief wind gusts up to 30 knots and IFR visibilities at the regional terminals through around 00Z this evening. VFR conditions should then prevail at the regional terminals by 03Z, with periods of MVFR visibilities possible overnight at VQQ. East or southeasterly surface winds sustained around 5 knots this morning at the regional terminals will become southeasterly around 10 knots after 15Z, except southerly at 5-10 knots at GNV outside of developing convection. Southeast or southerly surface winds will diminish to around 5 knots after 01Z this evening.

MARINE

A trough of low pressure will move through the area today with breezy southeast to south winds and occasionally rough seas. In addition, numerous showers and thunderstorms are expected at times over the area waters through tonight. Some of the thunderstorms may be strong. High pressure ridging will slowly build into the area late Sunday into early next week resulting in a slow lowering of winds and seas.

Rip Currents: Seas at coastal buoys are currently showing 4-5 ft with coastal observations showing due east flow about 10 mph. Winds are expected to veer slightly today, but still be in the 10-15 mph range. The rough seas and elevated winds suggests high risk for area beaches today so extended the high risk into southeast GA. NWPS rip current guidance also shows rip current probabilities higher than 75-80 percent over large areas of the coastline today.

Maybe a touch lower risk on Sunday, but still close to the moderate to high category. In any event, ocean swimming conditions are not safe this weekend.

FIRE WEATHER

- Patchy low daytime dispersions inland Today.

- Patchy high afternoon dispersions beginning Tuesday.

A trough moving in from the Atlantic will lead to numerous showers thunderstorms today with light southeasterly winds inland turning breezier and more easterly behind the Atlantic seabreeze pressing well inland. Sunday, the trough will lift away to the northeast with light southerly winds and scattered thunderstorms as Atlantic seabreeze moves past US-17 to near highway 301 before merging with Gulf seabreeze with light southeast winds 5-10 mph with gusts 15-20 mph at the coast. High pressure ridging will be over the FL peninsula next week as a trough extends over the southeast states northwest of the area and decreasing chances for thunderstorms.

Patchy low daytime dispersions expected inland today due to mostly cloudy skies and numerous coastal showers and storms moving inland from the coast today along with light transport winds away from the coast. Daytime dispersions will be generally fair to good Sunday and good Monday. Patchy high inland dispersions expected Tuesday through the end of next week as mixing heights increase under the ridge.

Fog Potential: Significant fog development is not expected, with shallow, patchy fog late overnight limited to areas that receive locally heavy rainfall.

PRELIMINARY POINT TEMPS/POPS

AMG 90 73 93 74 / 70 20 50 20 SSI 88 78 90 78 / 80 20 30 10 JAX 90 74 93 75 / 70 20 50 10 SGJ 89 76 90 76 / 60 20 40 0 GNV 91 74 93 74 / 70 20 50 10 OCF 91 74 93 74 / 60 20 40 10

JAX WATCHES/WARNINGS/ADVISORIES

FL...High Risk for Rip Currents through late tonight for FLZ124-125-138- 233-333. GA...High Risk for Rip Currents through late tonight for GAZ154-166. MARINE...None.