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 Continues Across Most of Our Area through Saturday.

- Isolated to Widely Scattered Afternoon and Early Evening Thunderstorms are Possible Today, Mainly for Locations South of Interstate 10.

- Heat Advisory Today for all of Northeast and North Central FL and Also the Coastal Counties in Southeast GA. Peak Heat Index Values of 105-112 for Most Locations. Major Heat Risk for Portions of Our Area Continues through Saturday.

- Afternoon and Evening Thunderstorm Coverage Gradually Increases this Weekend through Early Next Week. Locally Heavy Rainfall is 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 Northeast and North Central FL.

Overnight surface analysis depicts Atlantic high pressure (1021 millibars) centered over the southwestern Atlantic, with this feature extending its axis westward across the FL peninsula and into the southeastern Gulf. Aloft...deep-layered Atlantic ridging remains in control of our weather pattern, with a weak shortwave trough moving slowly eastward across southeast AL and southwestern GA on the northern periphery of the Atlantic ridge. Meanwhile, a tropical upper tropospheric trough (TUTT) was spinning westward across the Bahamas, with this feature moving across the southern periphery of the deep-layered ridge. Latest GOES-East derived Total Precipitable Water imagery indicates that seasonably moist conditions remain in place across southeast GA, northern portions of the Suwannee Valley, and across portions of north central and coastal northeast FL, where PWATs were generally around 1.9 inches. The northern extent of a Saharan Air Layer (SAL) has otherwise dropped PWATs to around 1.6 inches elsewhere across northeast and north central FL. Mainly mid and high altitude debris cloud cover originating from late afternoon and evening convection was drifting across portions of our area, with fair skies otherwise in place. Temperatures at 07Z ranged from the mid to upper 70s at most inland locations to the lower 80s at coastal locations. Dewpoints were generally 70-75.

Deep-layered ridging will lift slightly northward today as the weak shortwave over the Deep South fills. Meanwhile, the aforementioned TUTT feature will continue to spin slowly westward across the Bahamas through tonight. This evolution of the weather pattern will place the ridge axis directly across our region, with prevailing low level southwesterly flow advecting the northern extend of the SAL into southeast GA this afternoon. Otherwise, a pocket of deeper moisture currently in place from St. Augustine southward along the northeast FL coast and also over eastern portions of the Ocala National Forest will also shift slightly northward, and just enough moisture should be in place across north central and portions of northeast FL this afternoon to ignite isolated to widely scattered convection along mesoscale boundaries such as the inland moving Atlantic and Gulf sea breezes, as well as the St. Johns River and Lake George breezes, with activity mainly developing for locations south of Interstate 10. A few storms could briefly pulse and become strong late this afternoon as mesoscale boundaries collide, with strong wind gusts of 40-50 mph being the primary threat, along with cloud to ground lightning strikes. Activity should quickly diminish early this evening.

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 60s across most of inland southeast GA and for inland portions of northeast and north central FL. Dewpoints will remain in the 70s at coastal locations and will again increase to the upper 70s late this afternoon as the Atlantic sea breeze pushes inland past the I-95 corridor. We left the inherited Heat Advisory untouched, which includes all of northeast and north central FL, as well as Camden and Glynn Counties in coastal southeast GA. Heat indices will soar to the 108-112 degree range in the Heat Advisory area, and a few coastal locations and possibly inland locations in northeast FL could briefly nudge above the 113 degree threshold as the sea breeze pushes inland later this afternoon. Confidence was too low to try and pinpoint any areas that will reach Excessive Heat Warning criteria (113 degrees and above) at this time.

Breezy conditions will develop at coastal locations late this afternoon and will continue through early this evening as the Atlantic sea breeze shifts inland. Otherwise, debris cloud cover from any convection that manages to develop later this afternoon will gradually thin out towards midnight, with low level southwesterly flow keeping lows in the mid to upper 70s, except around 80 at coastal locations.

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 THURSDAY/

Main Highlights During This Period:

- Unsettled Pattern Early to Mid Week.

- Not as hot Monday through 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 /06Z FRIDAY THROUGH 06Z SATURDAY/

VFR conditions will prevail at the regional terminals through at least 17Z. Only isolated to widely scattered showers and thunderstorms are expected to develop near the northeast FL terminals after 17Z, with confidence high enough to include a PROB30 group for brief wind gusts up to 30 knots and MVFR visibilities during heavier downpours at GNV after 21Z through around 01Z Saturday. Confidence remains too low elsewhere at the Duval County terminals and SGJ to maintain vicinity shower or thunderstorms during the afternoon and early evening hours. VFR conditions should then prevail at the regional terminals after 02Z Saturday, with MVFR visibilities possibly developing towards the end of the TAF period at VQQ. Southwesterly surface winds will remain sustained around 5 knots at the SSI and SGJ coastal terminals overnight. West- southwesterly surface winds are expected to develop by 13Z elsewhere, with speeds at the regional terminals increasing to 5-10 knots by 15Z. The inland moving Gulf and Atlantic sea breeze boundaries will shift surface winds to southeasterly and southerly at the coastal terminals by 19Z, with speeds increasing to 10-15 knots. Outside of developing convection, surface winds at GNV will shift to south-southwesterly around 10 knots towards 21Z. South to southwesterly surface winds will then diminish to around 5 knots or less at the inland terminals by 03Z, while speeds remain in the 5-10 knot range at the coastal terminals through around 06Z Saturday.

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 Friday 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 98 76 98 76 / 0 10 20 20 SSI 99 81 98 80 / 10 10 20 20 JAX 100 77 99 77 / 10 10 50 40 SGJ 97 79 96 77 / 10 20 40 30 GNV 98 74 97 75 / 30 20 50 20 OCF 99 74 96 77 / 20 30 40 20

JAX WATCHES/WARNINGS/ADVISORIES

FL...Heat Advisory from 11 AM this morning 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 11 AM this morning to 7 PM EDT this evening for GAZ153-154-165-166. MARINE...None.