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. Today: Highest coverage toward I-95 corridor & Atlantic Coast. Storm Hazards: Lightning, Gusty Winds up to 50 mph & Localized Flooding

- Hot Holiday Weekend Daily Peak Heat Indices: 105-110F. Heat Advisory Today Eastern Zones. Building heat risk next week potential heat advisory conditions

- Moderate Rip Current Risk Beaches Today

NEAR TERM /THROUGH TONIGHT/

Main Highlights:

- Peak Heat Indices around 105-109 near the I-95 corridor - Marginal Flood risk due to slow-moving downpours with PM T'Storms for coastal areas of NE FL - Moderate Rip Current Risk Today

Scattered to numerous thunderstorms will begin to develop through the afternoon hours, generally moving southwest to northeast around 10 mph. The slightly stronger southwesterly flow has injected high- grade moisture (PWATs 2"+) into the NE FL that will nourish convection this afternoon while the Atlantic sea breeze stays pinned a few miles from the Atlantic shoreline.

Though storm motion has increased over the last 24 hours, the slow- moving pulses developing along the the sea breeze collision and outflow/storm mergers will be capable of high-volume rain rates for short durations, increasing a localized flood threat mainly for NE FL. To underscore the flood threat today, the Weather Prediction Center has highlighted a sliver of NE FL coast (south of St Augustine) for a Marginal Risk of flooding this afternoon, especially in locations that received significant downpours yesterday. In addition to the flood threat, stronger pulse storms along the sea breeze merger around 4-7 PM today will be capable of gusty winds up to 50 mph and localized episodes of frequent lightning.

Latest surface observations in the eastern/coastal counties are already showing temperatures trending 2-4 degrees warmer than this time yesterday. Heat will build more early this afternoon ahead of convection and combine with dewpoints in the mid/upper 70s, bolstering Heat Index values into the upper 100s, especially in the beachside communities. A Heat Advisory is in effect through 7 PM for the coastal counties and the St Johns River valley, but likely will be potentially ended early as convection ensues during the mid afternoon rain cools the advised area.

This evening and overnight, thunderstorm activity will move into the adjacent Atlantic waters before sunset with lingering activity over land dissipating through 9 PM. Leftover cloud cover will gradually clear overnight, which may lead to patchy ground fog by dawn Monday, especially in areas where downpours occur this afternoon. Lows tonight will be similarly mild to this morning, reading around the mid 70s inland and upper 70s to near 80 at the coast.

AVIATION /18Z SUNDAY THROUGH 18Z MONDAY/

Pushed the TSRA tempo period up a couple of hours to reflect current conditions. Widespread showers and numerous thunderstorms have filled in across NE FL with impacts near the immediate coastal terminals at 18z. Expect 2-3 hours of temporary TSRA impacts and MVFR to IFR restrictions due to heavy downpours. By the early evening, around 22z, convective activity will be pushing offshore while lingering activity over land begins to diminish. Outside of thunderstorms, southwesterly winds at or below 10 knots will prevail until sunset, trending calm thereafter. Possible shallow fog at inland airfields by sunrise Monday. Breezy southwest winds will lead to early showers once again, as early as 14z will develop with possible BKN cumulus around 2-2.5 kft.

MARINE

High pressure ridge will build across central and south Florida early this week as low pressure troughing develops to the north. This pattern will lead to prolonged southwesterly flow during the day followed by nightly surges from the south to Small Craft Exercise Caution speeds. The offshore flow will increase afternoon and evening thunderstorm chances over the local nearshore waters this afternoon and again each day through the upcoming week.

Rip Currents:

Surf between 1 to 3 feet with weak onshore swell will keep rip current risk at low-end moderate levels during the afternoon hours as the sea breeze develops through the first half of the week.

FIRE WEATHER

Southwest flow continue Monday and Tuesday with showers and isolated storms moving inland from the Gulf Coast during the morning, spreading toward the Atlantic coast into the afternoon. The east coast sea breeze will develop and drift inland toward the I-95 corridor mid to late afternoon each day. The best chance of afternoon and evening storms each day will focus between Highway 301 and the Atlantic coast and across inland southeast GA Tuesday afternoon and evening ahead of a stalling front. Dispersion will be elevated across inland southeast GA and parts of the Osceola NF each afternoon. Daily heat index values will approach 105-110 deg. Afternoon minimum humidity will continue above critical values.

Fog Potential and other remarks: Patchy inland fog each morning around sunrise is possible, especially where rainfall recently occurred. Thunderstorms will be capable of producing lightning, torrential rainfall, and erratic wind gusts during the afternoon and evening.

PRELIMINARY POINT TEMPS/POPS

AMG 76 95 76 95 / 30 30 30 30 SSI 79 94 79 95 / 30 30 10 30 JAX 77 95 77 96 / 10 40 10 30 SGJ 77 94 77 95 / 10 40 10 30 GNV 75 93 75 94 / 10 30 10 20 OCF 75 93 75 93 / 10 30 10 20

JAX WATCHES/WARNINGS/ADVISORIES

FL...Heat Advisory until 7 PM EDT this evening for FLZ024-038-124- 125-132-137-138-225-232-233-237-325-333-425-433-533-633. GA...Heat Advisory until 7 PM EDT this evening for GAZ153-154-165- 166. MARINE...None.