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. Sunday: Strong thunderstorm Risk near U.S. Highway 301 & I-75 corridors. Main Storm Hazards: Lightning, Localized flooding & Gusty Winds

- Moderate Rip Current Risk at All Area Beaches. Increased rip current risk possible late next week

NEAR TERM /THROUGH SUNDAY/

Highlights Today and Tonight:

- Heavy rainfall/localized flooding remains the main threat from thunderstorm activity today, mainly between the I-95 and US-301 highway corridors

Showers and thunderstorms will build through the afternoon and into this evening as southwesterly and southerly flow persisting through the day and shifting to become more out of the southeast overnight and into early Sunday morning as high pressure ridging over the Atlantic shifts northward and the stalled frontal boundary to the north becomes more disorganized, with PWAT values of over 2 inches in place over the region which may result in heavier amounts of localized rainfall for areas west of I-95 corridor and east of I-75. Potential for isolated strong storms to develop today. High temperatures will rise into the mid to upper 80s over southeast Georgia and in the lower 90s over northeast Florida this afternoon. Overnight low temperatures tonight will drop down into the lower 70s over inland areas and in the mid to upper 70s for areas along the coastline and near the St Johns River. Heat index values today will rise to to over 100 for northeast Florida and adjacent portions of southeast Georgia.

SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/

Main Highlights This Period: (Sunday through Monday night)

- Low Flooding Rain Risk Inland Northeast Florida - Daily Thunderstorm Potential

Easterly flow and coastal troughs will bring morning coastal showers and isolated thunderstorms, then with diurnal heating rain chances shift inland and shower and thunderstorm activity expands from east to west each afternoon. The best chance of isolated stronger storms will focus toward the I-75 corridor during the late afternoon and early evening where boundary mergers focus. Above average rain chances continue Sunday with deep moisture across the area and precipitable water over 2 inches. Monday, some drier air begins to infiltrate across southeast GA, which will bring a decrease in rain chances compared to recent days. Given high moisture and weak steering flow of < 10 kts, a marginal risk of flooding rainfall (level 1 out of 4) is advertised by the Weather Prediction Center for areas near the I-75 corridor each day. Rain chances tapper off inland before midnight, then resurrect near the Atlantic coast overnight with easterly flow. Patchy inland late night fog will be possible each night.

Temperatures will trend near to little above average this period with highs in the upper 80s along the Atlantic coast to lower 90s well inland and daily peak heat index values around 105 degF. Muggy overnight lows will range in the 70s.

LONG TERM /TUESDAY THROUGH SATURDAY/

Main Highlights This Period: (Tuesday through Friday)

- Daily Thunderstorms - Isolated Strong Storms Possible Inland - Increased Rip Current Risk Mid-Week

East to southeast steering flow will continue through the period between a strong 500 mb ridge anchored north of the region and inverted troughs/easterly waves to the south and west. The deeper moisture will focus across northeast FL with drier air across southeast GA, which will influence daily thunderstorm coverage from about 20-40% across southeast GA to around 40-70% across northeast FL. With the easterly flow, Atlantic coast showers and isolated storms will move inland through midday, then rain chances expand westward into the afternoons with diurnal heating.

The risk of isolated stronger storms and localized flooding rainfall potential increases late week (Thu-Fri) and depends on the track and structure of the tropical wave that was TS Dolly as the system approaches the Bahamas and possibly crosses south FL. The upper level dynamics with this passing wave could enhance lift and increase tropical moisture across northeast FL, which would favor increased rain chances and storm strength.

Given the position of the upper level ridge and daily rain chance pattern, above average temperatures will trend in the mid to upper 90s for southeast GA to the low to mid 90s for northeast Florida each day. Daily peak heat index values are expected to range in the 100-105 deg range with drier air mixing down limiting heat advisory risk.

Persistent easterly flow combined with increasing ESE swells as the tropical wave approaches the Bahamas mid week could increase the local rip current risk from Moderate to High in the Wed/Thu time- frame.

AVIATION /00Z SUNDAY THROUGH 00Z MONDAY/

Ongoing convection continues to push westward further inland, with only GNV hanging onto VCTS and minor restrictions from lingering SHRA for the next hour or so. Otherwise, main concern for the overnight hours will be some lower clouds and scattered vsby restrictions for most terminals. Lower clouds will move onshore at times overnight thanks to an offshore inverted trough, though restrictions are not forecast at this time. Only restrictions for the overnight hours included was at GNV and VQQ, where FG/BR is expected. Any restrictions are expected to clear throughout the morning hours, with confidence high enough to include PROB30 groups at all airfields diurnally on Sunday. Lowest confidence is for coastal sites, as TSRA development may be mostly inland thanks to another day of onshore flow.

MARINE

Onshore winds continue this weekend as high pressure builds to the north of the local waters and remains in place through much of next week. This will focus chances for showers and thunderstorms mainly inland, with lower chances across area waters overall.

Rip Currents: Moderate risk of rip currents will persist this weekend in the onshore flow as surf/breakers slowly increase to 2 to 3 feet. This pattern will continue into early next week as well.

FIRE WEATHER

Prevailing east to southeast winds with a dominant east coast sea breeze. Midday showers and isolated thunderstorms shift inland into the afternoon, with isolated stronger storms most likely between Highway 301 and Interstate 75 in the afternoons and early evening. Thunderstorm chances decrease next week with a warming trend in temperatures. Minimum humidly remains above critical values. Daytime dispersion will be in the fair to generally good range Sunday and Monday.

Fog Potential: Gusty and erratic winds can be expected in and near thunderstorms with briefly localized flooding rainfall. Late night and early morning patchy fog will be possible.

PRELIMINARY POINT TEMPS/POPS

AMG 72 90 73 91 / 20 40 10 50 SSI 78 88 76 88 / 20 30 30 40 JAX 74 90 74 90 / 20 30 40 50 SGJ 76 88 76 88 / 30 40 40 40 GNV 73 91 73 91 / 20 60 20 80 OCF 73 91 74 91 / 20 70 20 80

JAX WATCHES/WARNINGS/ADVISORIES

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