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 /UNTIL 6 AM SATURDAY MORNING/

Main Highlights:

- Numerous Afternoon and Evening Thunderstorms Expected through Saturday. Strong Storm Potential Along the I-95 Corridor During the Late Afternoon Hours. Stronger Storms May Produce Wind Gusts of 40-55 mph, Frequent Lightning Strikes, and Torrential Downpours that Could Result in Localized Flooding.

- Daily Peak Heat Index Values of 104-108 Degrees Expected. through Monday.

- Moderate Rip Current Risk Continues at All Area Beaches through Monday. High Risk Likely from Tuesday through Thursday.

Afternoon surface analysis depicts weakening Atlantic high pressure (1019 millibars) situated off the southeastern seaboard, with this feature extending its axis westward across north central FL. Meanwhile, a frontal boundary stretching from North Carolina's Outer Banks westward across the Tennessee Valley and the Ozarks was in the process of stalling as another weak high pressure center stretches across the Great Lakes, Mid-Atlantic states and New England in the wake of this boundary. Aloft...deep-layered ridging was centered just northeast of the Bahamas, which was directing a shortwave trough located on the western periphery of this feature north- northeastward across western portions of the FL panhandle. Otherwise, a potent shortwave trough was digging eastward across the Ozarks towards the Tennessee Valley. Latest GOES-East derived Total Precipitable Water imagery indicates that deep tropical moisture remains in place area-wide, with PWAT values generally in the 2 - 2.3 inch range across our area. Convection on the leading edge of the shortwave trough that was crossing western portions of the FL panhandle has crossed the Alapaha and Suwannee Rivers, with only isolated showers located elsewhere, mainly at inland locations. Temperatures at 18Z were generally in the upper 80s and lower 90s, with dewpoints mostly in the low to mid 70s creating heat index values mostly around 100.

Abundant tropical moisture and continued slow cooling of temperatures aloft should allow for showers and thunderstorms to become numerous across our region as the afternoon progresses, with southwesterly steering flow bringing convection towards the I-95 corridor late this afternoon, where activity could linger into the early evening hours. The presence of a pinned Atlantic sea breeze boundary along the I-95 corridor and other mesoscale boundary collisions should allow for storms to "pulse" and potentially become strong later this afternoon, especially as convection intersects the Atlantic sea breeze boundary that should be positioned near I-95. Storms that pulse and become strong will be capable of producing downburst winds of 40-50 mph, along with frequent lightning strikes and torrential downpours. Given the deep tropical moisture in place, any storms that "back-build" along mesoscale boundaries such as the Atlantic sea breeze could result in localized flooding, especially if this potential event occurs at urban or low-lying, normally flood prone locations.

Convection could linger into the early to mid evening hours tonight, especially along the I-95 corridor in southeast GA, where convection may not arrive until later this afternoon. Otherwise, debris cloud cover will thin out after midnight, with deepening southwesterly flow likely developing a greater coverage of predawn convection over Apalachee Bay than what was observed this morning. Some of this activity could move onshore along the FL Big Bend and Nature Coasts towards sunrise, but activity should remain west of the Suwannee River and north central FL through the early morning hours on Saturday. Lows will fall to the low and mid 70s across most of our area.

SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY NIGHT/

Main Highlights This Period:

- Potential for isolated strong thunderstorms and localized flooding on Saturday

Southwest steering flow continues to bring in enhanced moisture (PWATs 2.2-2.4") across the area, prompting numerous showers and storms Saturday afternoon and evening. The Gulf sea breeze will push further inland, meeting the Atlantic sea breeze closer to the east coast/I-95 corridor, which is where our best chance for strong thunderstorm development will be. Gusty winds will be the primary threat with any strong storms, but also heavy rainfall may cause localized flooding concerns, especially in urban and typically flood prone areas. High temperatures Saturday will be in the low 90s, with max afternoon heat index values peaking around 104-107 for portions of northeast Florida.

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. Overall, precipitation chances will be about 20-40% across much of the area, with higher chances over north central Florida. Similar high temperatures are expected Sunday, in the lower 90s.

LONG TERM /MONDAY THROUGH FRIDAY/

Main Highlights This Period Monday through Thursday:

- Daily Thunderstorms Potential Each Day Next Week

- Elevated Rip Current Risk Next Week

Northwesterly flow Monday gradually shifts to northeasterly Tuesday, beginning a few day period of stronger onshore flow through Thursday. Tuesday through Thursday, those breezy easterly surface winds will bring showers and isolated thunderstorms onshore in the mornings, with coverage expanding inland throughout the day. For daily afternoon and evening storms, the focus will be generally south of I-10 each day. High temperatures gradually lower throughout the week, Monday highs will be in the lower to mid 90s, and by Thursday areas closer to the east coast will peak in the mid 80s.

AVIATION /00Z SATURDAY THROUGH 00Z SUNDAY/

Convection/TSRA activity ending early this evening as line of storms pushes into the Atlantic waters with just lingering IFR conds at SSI until 01Z. Otherwise mostly VFR conds this evening with mid/high clouds slowly dissipating, then the usual chances of LIFR CIGS and IFR VSBYS in low stratus/fog at VQQ/GNV from 08-12Z, with much lower chances at the coastal TAF sites towards sunrise. Light SW flow and diurnal heating will trigger afternoon showers and storms at all TAF sites Saturday afternoon and for now have added PROB30 groups at all terminals from 17-23Z for TSRA activity with gusty winds and MVFR conds for now, with timing to be refined in later TAF forecasts.

MARINE

Weakening high pressure situated off the southeastern seaboard will continue to shift southward as a frontal boundary stalls across the Tennessee Valley and the Carolinas. The axis of this feature will remain south of our local waters through the weekend, resulting in prevailing south to southwest winds, with the afternoon sea breeze providing onshore winds for the near shore waters. Thunderstorms will likely develop over coastal locations during the mid to late afternoon hours that will generally progress eastward across our local waters during the late afternoon and evening hours through the weekend, with a few stronger storms containing strong wind gusts, frequent lightning strikes, and torrential downpours possible each afternoon and evening. Meanwhile, high pressure strengthening over the Great Lakes region in the wake of a cold front on Sunday and Monday will wedge down the southeastern seaboard by Tuesday and Wednesday. Onshore winds will develop across our local waters on Monday night, followed by northeasterly winds strengthening on Tuesday and especially Tuesday night and Wednesday, when a period of Small Craft Advisory conditions will be possible, accompanied by building seas that will likely persist through Thursday.

Rip Currents: Offshore winds during the morning hours through Monday will tend to reduce the rip current risk at area beaches. The afternoon sea breeze will create breakers of 2-3 feet at the northeast FL beaches, which will combine with a lingering easterly ocean swell to create a lower end moderate risk, especially during the outgoing tide. Breakers of only 1-2 feet at the southeast GA beaches will likely yield a low risk through Monday. Northeasterly winds will develop on Monday night and will likely become breezy on Tuesday, likely resulting in a high risk at all area beaches from the afternoon hours through at least Thursday as breakers build.

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 72 92 73 92 / 40 50 30 20 SSI 77 88 76 91 / 50 50 30 30 JAX 74 91 74 92 / 40 60 30 40 SGJ 74 90 74 91 / 40 60 30 40 GNV 73 92 73 91 / 30 60 30 40 OCF 73 92 73 92 / 30 60 30 70

JAX WATCHES/WARNINGS/ADVISORIES

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