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

- Hot and Humid Today thru Monday - Peak Heat Index Values: 104-108

- Afternoon & Evening TStorms Area-Wide Through Most of the week. Scattered to Numerous Thunderstorms this afternoon (2 PM 9 PM). Strong Storms with Gusty Winds, Frequent Lightning Strikes & Heavy Downpours Possible Along the I-95 Corridor

NEAR TERM /THROUGH TONIGHT/

Main Highlights This Period:

- Another Hot Day with Heat Index Peaking Around 102-107 Degrees

- Scattered to Numerous Afternoon Thunderstorms, A Few Strong to Isolated Severe Storms Possible, with locally heavy rainfall

- Lower confidence in late night strong to severe storms for inland Southeast Georgia

Not much change to ongoing forecast as a moist West to Northwest steering flow along with PWATs around 2 inches will support scattered to numerous storms area-wide this afternoon and evening. These higher PWATs and generally slow storm motion from West to East around 10-15 mph or less will support localized flooding threat with isolated 2-4 inch amounts, highest threat in urban areas today.

Prior to the onset of convection expect temps to reach into the lower to middle 90s and combine with dew point temps into the mid/upper 70s to once again produce peak heat indices of 104F to 108F early this afternoon, remaining just below Advisory criteria.

Convergence in the W-SW flow along the NE Gulf Coast has already triggered early rounds of convection along the I-75 corridor of inland NE FL which will continue to progress to the East and interact with the East Coast sea breeze front trapped along the I-95 corridor and this is where the best chances for isolated Severe Storms will be with downburst winds of 60 mph possible along the Atlantic Coastal counties of NE FL/SE GA. Further inland, isolated strong storms with gusty winds of 40-55 mph still expected, and any cell mergers and/or outflow boundary collisions still have the potential to trigger an isolated severe storm as well. Mid level lapse rates are not as steep as on Saturday afternoon as 500mb temps have warmed slightly, closer to -6C.

Convection will start to fade around sunset and push into the Atlantic Coastal waters, with most areas developing fair skies by midnight with humid overnight lows in the 70s inland and near 80F along the Atlantic Coast.

There are a few higher res models which are suggesting that a line of pre-frontal showers and storms may push into inland SE GA during the overnight hours, which would impact areas to the NW of Waycross with isolated strong to severe storms with gusty winds possible after midnight. There is lower confidence in this scenario at this time, but will need to closely monitor for another potential round of convection impacting inland SE GA late tonight.

SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/

Main Highlights This Period:

- Heat index values approach Advisory levels Monday afternoon - Scattered to numerous afternoon and evening thunderstorms each day - Locally heavy rainfall, along with the potential for strong to severe thunderstorms both Monday and Tuesday afternoons

Surface high pressure ridge will stretch across southern FL Monday, as a cold front sinks south toward the region. The combination of ample moisture, diurnal heating, Gulf sea breeze and frontal convergence will lead to above average chances of afternoon and evening convection. The flow from the west is expected to be strong enough to keep the east coast sea breeze pinned to the coast. This will result in a progressive flow of convection across the forecast area from west to east, and allow the higher temperatures to reach all the way to the beaches. The potential for strong to severe storms will once again be possible.

On Tuesday, the front will sink south into the forecast area. In addition to the factors still in place from Monday, the frontal convergence will be greater. This will result in greater coverage of convection Tuesday afternoon and evening. Once again, there will be enough flow from the west to keep the east coast sea breeze from getting past the beach, allowing beach communities to heat up ahead of the storms.

With loss of diurnal heating, convection should end by midnight Monday night, but with the front in the forecast area, activity will likely continue through the night Tuesday night.

Temperatures will continue to be above average this period.

LONG TERM /WEDNESDAY THROUGH SUNDAY/

Main Highlights This Period:

- Daily scattered to numerous afternoon and evening thunderstorms - Locally heavy rainfall and potential for strong to severe storms

The cold front will remain stalled over the region Wednesday through Friday, as it slowly dissipates. This boundary will continue to aid in daily convection, with greatest chances Wednesday. As the boundary weakens Thursday into Friday, storm chances will decrease. The southwest flow will continue to be strong enough to keep the east coast sea breeze from making much progress. Temperatures will trend below average Wednesday due to convective coverage, with readings trending above Thursday and Friday, as coverage is not as great.

Another front will sink south into the area and stall over the weekend. Above average chances for storms forecast due to the frontal convergence. Temperatures will be near seasonal levels over the weekend.

AVIATION /18Z SUNDAY THROUGH 18Z MONDAY/

Convection already ongoing near GNV and will push into the rest of the TAF sites in the 18-22Z time frame and have added in VCTS with TEMPO groups for gusty winds and MVFR CIGS/VSBYS in TSRA activity at the remaining terminals. As convection develops, a few of the stronger storms may produce gusty winds to 30 knots and potential for IFR VSBYS which may need to be added in forecast updates through the afternoon hours. Convection should fade around sunset and expect a return to mainly VFR conds and convective mid/high debris clouds after 02-03Z. SW winds remain elevated tonight and should prevent much fog formation except for MVFR VSBYS at VQQ. Chances for MVFR CIGS in the 09-12Z time frame too low to include at this time. SW winds increase once again by 14-15Z time frame on Monday with VCSH and isolated showers by the end of the upcoming TAF period.

MARINE

The region will be between high pressure to the south southeast, and a frontal zone stalling just north of the local waters through most of the upcoming week. This will lead to a predominant southwest flow which will become breezy at times, with periods of Small Craft Exercise Caution conditions, mainly over the offshore waters. The offshore flow will continue to push strong storms with gusty winds and frequent lightning into the coastal waters through the period.

Rip Currents:

Generally a low risk of rip currents early this week as surf remains only in the 1-2 ft range in the predominant offshore flow.

FIRE WEATHER

- Patchy To Areas Of High Dispersions This Week

A series of frontal boundaries will keep chances for daily rounds of showers and thunderstorms above average through the week, and into next weekend. Temperatures will be largely above average this week.

FOG POTENTIAL AND OTHER REMARKS: Significant fog is expected Tonight. Daily showers and thunderstorms are expected, mainly during the afternoon and evening hours, with the potential for strong storms capable of producing gusty winds, frequent lightning, and locally heavy rainfall each day.

PRELIMINARY POINT TEMPS/POPS

AMG 74 93 73 84 / 30 80 60 70 SSI 77 95 76 89 / 30 80 60 70 JAX 75 96 76 92 / 40 70 60 70 SGJ 76 95 77 93 / 40 70 40 60 GNV 75 93 76 91 / 20 40 20 50 OCF 76 91 78 91 / 20 30 10 20

JAX WATCHES/WARNINGS/ADVISORIES

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