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

- Near Record Heat and Dangerous Heat Indices through the Weekend. High Temperatures through Saturday: 96 - 100. Heat Advisory Today from 11 AM 7 PM for Northeast & North Central FL &

- Coastal Southeast GA, with Major to Extreme Heat Risk Area-Wide this Afternoon. Peak Heat Index Values: 105 - 112

- Isolated to Widely Scattered Afternoon Thunderstorms Today. Main Impact Area: Inland Locations South of Interstate 10. Stronger Storms May Produce Localized 40-50 mph Wind Gusts & Lightning

- Increasing Coverage of Afternoon & Evening TStorms Sat - Tues. Locally Heavy Downpours Possible Sunday through Tuesday

NEAR TERM /THROUGH TONIGHT/

Main Highlights through Tonight:

- Near Record Heat Continues Area-Wide.

- Heat Advisory for Northeast and North Central FL and the Coastal Southeast GA Counties Today.

- Isolated to Widely Scattered Afternoon and Early Evening Thunderstorms, Mainly Across Inland Northeast and North Central FL.

Ridge axis over the FL peninsula will lift slightly northward developing a more south-southwest flow. This will advect in the northern extent of a Saharan Air Layer (SAL) into northeast and north central FL. PWATs could lower into the 1.4-1.6 inch range but should provide enough moisture to trigger isolated to widely scattered showers and storms along the inland-moving Gulf and Atlantic sea breezes later this afternoon into evening. Activity will likely remain south of the I-10 corridor with a few brief storms along the coast and SE GA. A few storms could briefly pulse and become strong late this afternoon as mesoscale boundaries collide. With potential dry air entrainment and DCAPE values around 1000 J/kg, strong wind gusts of 40-50 mph will be the primary threat.

The bigger story will continue to be the heat, with a more subsident air mass beneath the SAL allowing highs to soar to near daily records (see "Climate" section below for details), as most locations across our region top out between 95-100 degrees. The increasingly subsident air mass will allow dewpoints to mix down to the mid-upper 60s across most of inland SE GA and along the FL/GA border. This will limit the oppressive heat in inland SE GA today. Dewpoints will remain in the 70s at coastal locations and most of NE FL where t. he Heat Advisory continues into this evening. Peak heat indices will soar to the 108-112 degree range, with a few coastal locations briefly nudging to 113 degree threshold before the Atlantic sea breeze pushes inland later this afternoon. Overnight lows will be in the mid-upper 70s.

SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/

Main Highlights During This Period:

- Heat Advisory potential for Saturday - Increased Storm Chances This Weekend, Especially Sunday

Southerly flow brings in more moisture across the area, with convective chances increasing Saturday primarily over Northeast Florida where PWATs will rise into the 2-2.5" range. Dangerous heat continues on Saturday, with highs reaching the mid to upper 90s and max afternoon heat index values of 105-110 degrees. A Heat Advisory may be necessary for northeast Florida and coastal Southeast Georgia.

Sunday, deep southwest flow and an approaching front from the north will prompt numerous showers and storms across the area, especially near the east coast where the Atlantic and Gulf sea breezes meet. The Weather Prediction Center has southeast Georgia and coastal Northeast Florida under a 'Marginal' risk of Excessive Rainfall. With higher cloud cover and storm coverage, temperatures will finally drop to near normal, with max heat indices staying below Advisory criteria.

LONG TERM /MONDAY THROUGH FRIDAY/

Main Highlights During This Period:

- Unsettled Pattern Early to Mid Week - Not as hot Monday to Wednesday

Storm chances remain high through Tuesday as the front sinks into Georgia Sunday night into Monday, then reaches the area on Tuesday and dissipates through mid-week. Several days of numerous heavy showers and storms will pose a threat to localized flooding, most of the area is under a 'Marginal' risk of Excessive Rainfall on Monday. The generally westerly surface flow will keep highest storm chances and strong storm potential closer to I-95 where the sea breezes interact. Temperatures drop further Monday and Tuesday, with highs in the mid 80s to mid 90s.

Wednesday onward, scattered storms forecast area-wide for the afternoons and evenings, with near seasonal temperatures.

AVIATION /18Z FRIDAY THROUGH 18Z SATURDAY/

Mostly VFR conditions continue through the period. SW winds increase to around 5-10 kts after 15Z. The Atlantic sea breeze will shift onshore by 19Z shifting winds to SSE around 10-12 kts for coastal TAF sites. Isolated showers and storms may develop along the Gulf sea breeze as it shifts inland for the NE FL sites. Confidence remains low except for GNV which has a TEMPO group for brief wind gusts up to 30 knots and MVFR visibilities during heavier downpours after 21Z through around 00Z Saturday. Otherwise, have VCSH between 20-01Z.

MARINE

Atlantic high pressure will continue to extend its axis westward across the Florida peninsula through Saturday morning, with this weather pattern maintaining a prevailing southwesterly wind flow during the overnight and morning hours, with southeast and southerly winds then surging to Caution levels during the late afternoon and evening hours as the Atlantic sea breeze shifts inland through Saturday. Only isolated thunderstorms will be possible across the near shore waters this afternoon, mainly from around St. Augustine southward. Troughing will then develop over the southeastern states by late Saturday and Sunday, with prevailing westerly winds forecast and increasing chances for afternoon and evening thunderstorms, especially by Sunday and Monday. A frontal boundary will then sink into the southeastern states early next week, with this feature likely stalling over the southeast Georgia waters by Tuesday before weakening towards midweek. Numerous showers and thunderstorms are forecast on Tuesday across our local waters, with coverage then expected to gradually decrease by Wednesday and especially Thursday.

Rip Currents:

Southeast to southerly winds strengthening late this afternoon will create a lower end moderate risk at all area beaches today, with surf increasing to 2-3 feet towards sunset at the northeast FL beaches, while surf only increases to 1-2 feet at the southeast GA beaches. A lower end moderate risk may develop again at the northeast FL beaches late on Saturday afternoon as onshore winds strengthen, but a low risk appears likely at the southeast GA beaches due to low surf heights. Prevailing offshore winds on Sunday and Monday should yield a low risk at area beaches.

FIRE WEATHER

- Areas Of High Dispersions Today And Saturday North Of I-10

- Heat Advisory In Effect Today

High pressure ridge will prevailing just south of the area through Saturday. Drier than normal conditions are forecast through Saturday before rain chances begin to increase late weekend and into early next week as a frontal boundary approaches from the north. Above average temperatures and dangerous maximum afternoon heat index values expected through Saturday. Southwesterly surface winds continue through Saturday, with areas of high afternoon dispersion along and north of I-10. Despite drier air in place, minRH will remain above critical values, in the 35 to 45% range away from the coast. Heavy rain potential Sunday through Tuesday.

Fog Potential and other remarks: Significant fog potential is not expected through Friday night. Erratic wind gusts possible in and near thunderstorms, and at times, at a distance due to outflows.

CLIMATE

Daily record high temperatures at our designated climate sites for Friday and Saturday, July 10th-11th.

July 10th: KJAX: 102/1879 KGNV: 99/1914 KAMG: 99/1980 KCRG: 99/2016

July 11th: KJAX: 104/1879 KGNV: 100/1900 KAMG: 100/1980 KCRG: 99/1998

PRELIMINARY POINT TEMPS/POPS

AMG 75 98 77 96 / 10 0 20 40 SSI 80 98 80 97 / 10 20 10 50 JAX 77 100 77 98 / 10 40 20 60 SGJ 78 98 77 97 / 10 30 30 50 GNV 74 98 75 96 / 30 50 30 50 OCF 74 97 76 95 / 30 40 30 50

JAX WATCHES/WARNINGS/ADVISORIES

FL...Heat Advisory until 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 until 7 PM EDT this evening for GAZ153-154-165- 166. MARINE...None.