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

- Oppressive Heat and Humidity Continues through the Weekend. Heat Advisory for All of North Central and Northeast FL and Coastal Southeast GA Today. Extreme Heat Watch for Coastal Southeast GA on Thursday. Heat Advisories Likely Elsewhere Each Day through the Early Evening Hours.

- Scattered to Numerous Afternoon and Evening Thunderstorms Today and Thursday. Strong to Isolated Severe Storms Are Possible, with Wind Gusts of 40-60 mph, Frequent Lightning Strikes, and Heavy Downpours.

- Scattered Afternoon and Evening Thunderstorms from Friday through Monday.

NEAR TERM /THROUGH TONIGHT/

Main Highlights:

- Heat Advisory in Effect from Noon through 7 PM Today for All of North Central and Northeast FL and Coastal Southeast GA.

- Scattered to Numerous Afternoon and Evening Thunderstorms Today. Strong to Isolated Severe Storms Are Possible, with Wind Gusts of 40-60 mph, Frequent Lightning Strikes, and Heavy Downpours. Westerly surface winds continue today as the mean layer ridge into the mid levels is over the central Gulf. Deep layer flow up through about 500 mb is the west or northwest about 10-15 kt. PWATs remain elevated at about 2 inches or slightly higher. Guidance shows perhaps a better chance of showers and storms this afternoon and evening than prior forecasts. However, these higher chances, up to 40-60 percent, are focused in a convergence zone that appears to be located along the I-10 corridor northward to Highway 82 in southeast GA. Outside side of these areas, rain chances look to be 20-40 percent. Given the amount of moisture and instability, isolated strong/severe storms are probable especially with any boundary collisions and mergers. Latest model soundings show MLCAPE that may be up to 3000-3500 J/kg and the downdraft CAPE that may be near 1000. That should be enough for gusts up to 40-60 mph. The SPC has shown a marginal risk of severe storms for most of our area today. Isolated to scattered showers and storms are anticipated tonight, and will eventually fade and dissipate by midnight and will show only 10 percent chances after midnight.

Biggest concern today will be dangerously hot temperatures and heat index values. High temperatures will be in the mid to upper 90s, even at the east coast beaches. Maximum afternoon heat indices will be around 105-110 degrees. Heat advisory remains in effect.

SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/

Main Highlights This Period:

- Daily Isolated to Scattered Afternoon Thunderstorms, some of which could be strong.

- Heat Index Values near Heat Advisory levels each day. Extreme Heat Watch in place along coastal SE GA Thursday.

High pressure over the Gulf will begin to shift towards the northern Gulf coast late in the forecast period as a trough shifts south along the SE coast. With the high pressure over the Gulf, westerly- southwesterly flow will persist through the end of the week. Scattered showers and storms along the Gulf breeze as it pushes inland, with higher chances for locations south of the I-10 corridor as moisture will be slightly higher over NE FL. The Atlantic sea breeze will begin to push onshore during the afternoon hours, with coverage of showers and storms expect to inland from the coast of SE GA and NE FL as the sea breezes merge.

Warm temperatures will continue through the end of the week as daytime highs will remain in the upper 90s, close to 100F for some locations. A Heat Advisory will likely be needed for both days. An Extreme Heat Watch is currently in place for coastal SE GA as Heat Index values may rise to 112F to 114F Thursday afternoon.

LONG TERM /SATURDAY THROUGH TUESDAY/

Main Highlights This Period:

- Oppressive Heat Continues During the weekend, with Heat Advisories Likely.

A dipping cold front along the SE coast will allow for higher chances of showers and storms across SE GA on Saturday, and then south towards NE FL on Sunday. Coverage of showers and storms look to shift further south towards NE FL on Monday, and back north as the front drifts northward on Tuesday. Above average temperatures will persist into the upcoming weekend, where we will continue to have temperatures rise to the upper 90s and heat index values rising to heat advisory criteria during the afternoon hours. But the timing of showers and storms may keep some locations from rising much as cloud cover may limit much heating to take place.

AVIATION /12Z WEDNESDAY THROUGH 12Z THURSDAY/

VFR conditions will prevail at the regional terminals through at least 18Z. Showers and thunderstorms will begin developing near the Duval County terminals after 18Z, with activity then expanding to the SSI and SGJ coastal terminals towards 20Z and then southward towards the GNV terminal by around 22Z. TEMPO groups were placed at each terminal for brief wind gusts up to 35 knots, along with IFR visibilities during heavier downpours. Convection should shift southward and away from the terminals by 01Z this evening, with VFR conditions then prevailing overnight though sunrise on Thursday. Westerly surface winds will become sustained at 5-10 knots at the regional terminals by 15Z, followed by winds shifting to northwesterly by 17Z. The Atlantic sea breeze will develop after 18Z along the coast, with this boundary moving past the SSI and SGJ coastal terminals before 20Z, shifting surface winds to east- southeasterly around 10 knots at SGJ and southerly around 10 knots at SSI. After convection concludes, west-southwesterly surface winds around 5 knots are forecast during the overnight hours.

MARINE

Atlantic high pressure will shift south and westward as a trough forms over the southeastern states. Each afternoon, the sea breeze will shift winds to south to southeast over the near shore waters through the upcoming weekend, followed by southerly evening wind surges which may briefly increase to near caution levels. Scattered mainly afternoon and evening thunderstorms will remain possible each day through the upcoming weekend. Some of these storms may be strong with gusty winds and locally high waves.

Rip Currents: Low surf heights at or below 2 ft and offshore flow will likely yield a low risk at area beaches today. This pattern will likely continue through Friday.

FIRE WEATHER

- PATCHY HIGH AFTERNOON DISPERSIONS OVER SE GA TODAY AND Thursday.

Light west to southwest winds will keep the Atlantic seabreeze near the coast each day, with lower thunderstorm coverage expected Today. A few strong thunderstorms may produce gusty outflows with locally erratic winds. Warm temperatures continue as highs will be in the mid 90s inland and lower to mid 90s at the coast Today. Heat Advisory is in place across NE FL and coastal locations of SE GA as peak heat index values of 106-112. With warm temperatures expected to continue through the rest of the week, heat advisories will likely be needed. Patchy high daytime dispersions expected Today and Thursday as mixing heights increase with increasing westerly transport winds. Fog Potential: Significant fog development is not expected, with shallow, patchy fog late overnight limited to areas that receive locally heavy rainfall.

CLIMATE

Daily record high temperatures are possible from Thursday through Saturday:

Thursday, August 13th: KJAX: 99/2023 KGNV: 99/2023 KAMG: 100/9999 KCRG: 96/2023

Friday August 14th: KJAX: 99/2023 KGNV: 97/2023 KAMG: 101/2023 KCRG: 98/2023

Saturday August 15th: KJAX: 99/1956 KGNV: 100/1918 KAMG: 99/1995 KCRG: 97/9999

PRELIMINARY POINT TEMPS/POPS

AMG 94 75 96 77 / 30 10 10 10 SSI 95 78 97 80 / 40 20 20 10 JAX 95 76 97 76 / 60 20 40 10 SGJ 94 77 94 77 / 50 20 40 10 GNV 94 75 95 75 / 20 30 40 10 OCF 95 75 95 75 / 20 20 40 10

JAX WATCHES/WARNINGS/ADVISORIES

FL...Heat Advisory from noon today to 7 PM EDT this evening for FLZ021-023-024-030-031-035-038-120-124-125-132-136>138- 140-220-225-232-233-236-237-240-322-325-333-340-422-425- 433-522-533-633. GA...Heat Advisory from noon today to 7 PM EDT this evening for GAZ153-154-162-165-166. Extreme Heat Watch from Thursday morning through Thursday evening for GAZ153-154-165-166. MARINE...None.