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

- Isolated Afternoon Thunderstorms Today & Friday. Storm coverage increases this weekend into early next week. Locally heavy rainfall possible Sunday through Tuesday

- Heat Advisory NE FL and SE GA Today and Friday. Peak Heat Index: 105-111 Most Areas. Major Heat Risk through Friday and Saturday

UPDATE

Quick update to increase coverage of showers/storms across NE FL from JAX metro area southward through the I-95 corridor and St. Johns River Basin, these should generally last through sunset before weakening and pushing offshore with gusty winds and heavy rainfall.

Also, updated Friday forecast to include Heat Advisory for coastal SE GA and all of NE FL for heat indices to peak out in the 107-110F range as Max Temps will reach into the upper 90s/near 100F for most locations. Some drier air will mix down across inland SE GA where heat indices will top out in the 104-107F range, and have left out of the Heat Advisory for now.

NEAR TERM /THROUGH TONIGHT/

Main Highlights through Tonight:

- Heat Advisory Area-Wide Today - Isolated Afternoon and Evening Storms

High pressure ridge axis will remain across central and south Florida maintaining SW flow across the area. Another hot day is in store with prevailing subsidence and a pinned Atlantic sea breeze. Highs will rise into the mid-upper 90s with max heat indices in the 105-110 F range. A Heat Advisory is in effect area-wide through this evening. Highest heat indices will likely be along the coast and St Johns river basin. A pocket of relatively drier air combined with subsidence will suppress convection today across the Suwannee Valley, I-10 corridor and portions of inland SE GA. Lingering tropical moisture (PWATs 2+ in) over north-central FL will allow for a few showers and storms to develop along the Gulf sea breeze as it shifts inland this afternoon. Activity increases in coverage as the Gulf sea breeze interacts with the pinned Atlantic sea breeze along the coast later this afternoon into evening. Meanwhile, an upper shortwave will pass through inland SE GA providing enough lift and moisture to trigger a few showers and storms mainly in the Ocmulgee/Altamaha river basins later this afternoon into evening. Convection wanes by midnight. Overnight lows will be in the mid- upper 70s.

SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/

Main Highlights During This Period:

- Heat Advisory potential for Friday and Saturday - Lower convective chances Friday, but increased chance Saturday

Low to mid level ridge will remain the primary weather feature of influence for Friday and most of Saturday as well before starting to break down and weaken on Saturday Night. Mean layer moisture will continue to remain somewhat limited, as PWATs average generally in the 1.7 to 1.8 inch range during the short term period, with some pockets as low as around 1.6 inches across southeast GA on Friday. There does look to be an uptick in available moisture Saturday, especially over northeast FL and therefore also expecting an uptick in rain chances across this same area. Steering flow looks to remain out of the southwest, though the weakening flow will also more of a southeasterly sea breeze to develop, especially on Saturday. This sea breeze making at least some progress inland combined with the progressing Gulf coast breeze will bring the focus area for highest PoPs/stronger t'storm potential to be generally over interior/central areas.

The main concern continues to be dangerous heat risk for both Friday and Saturday, as high temperatures rise into the mid to upper 90s, even at the immediate Atlantic coast with southwest flow. Max temps may hit century mark in some spots each afternoon, however, the "saving grace" that may prevent any heat products will be excellent mixing of some of the drier air aloft each afternoon, limiting dew points to the upper 60s for many and therefore average heat indices around the 103 to 108 range. In addition, more higher clouds and gradual increase in convective coverage could also limit this potential. Will let the next shift make the final decision on this later tonight.

LONG TERM /SUNDAY THROUGH THURSDAY/

Main Highlights During This Period:

- Unsettled Pattern Develops for Sunday Onward - Not as hot Monday to Wednesday

High pressure ridging remains weak and generally south of the region for most of the long term period as a frontal boundary drops southward towards the region Sunday and Sunday Night, becoming diffuse over/just north of the region for the next several days thereafter. The stalled boundary and continued southwest flow/moisture advection will result in higher coverage of showers and t'storms daily for at least Sunday through Tuesday, and possibly into Wednesday as well. This rainfall will remain overall beneficial to the lingering drought, though locally heavy rainfall and/or training of heavy rainfall will elevate the risk for excessive rainfall/flooding.

Temperatures drop a few degrees by Sunday, with more cloud cover and rain coverage dropping temps even further towards or slightly below normal moving towards Wednesday.

AVIATION /00Z FRIDAY THROUGH 00Z SATURDAY/

Mainly VFR conditions continue through period. SW flow develops again today and increase to around 10 kts. The Atlantic sea breeze will be pinned to the coast only causing winds to shift SSE at SSI and SGJ in the afternoon. Showers and storms look to be limited to coastal TAF sites this afternoon into the evening. Have placed VCTS/PROB30 for SGJ but with lower confidence near SSI and CRG, have left VCSH for now.

MARINE

High pressure ridge will remain anchored across central and south Florida this week as low pressure troughing develops to the north. This pattern will maintain a southwest flow through early afternoon followed by late afternoon and evening wind surges from the south and an increase to Small Craft Exercise Caution wind speeds. The offshore flow will allow for a slight chance of afternoon and evening thunderstorm over the local coastal waters through Friday, with increased chances of thunderstorms Saturday through early next week. Mariners should expect locally strong wind gusts and frequent lightning with any developing thunderstorms.

Rip Currents:

Low to moderate risk of rip currents continues through the end of the week due to fairly low surf conditions and a mainly offshore flow. Enhanced potential occurs each afternoon/evening with the south-southeast wind surge in the wake of the sea breeze. Surf remains generally in the 1-3 feet range.

FIRE WEATHER

- Areas Of High Dispersions Inland Today And Friday

- Heat Advisory In Effect Today

High pressure ridge will prevailing just south of the area through Saturday. Drier than normal conditions are forecast today 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 Friday, with areas of high afternoon dispersion inland but especially inland southeast GA each day. Despite drier air in place, minRH will remain above critical values, in the 35 to 45% range away from the coast.

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

Summer heat continues. There is potential for some locations to get to the century mark today with probability of this occurrence at about 30 to 40 percent. These probabilities look a bit higher for Friday.

For the next few days, here are the record high temperatures that are within 3 degrees of the current forecast:

July 9th: KJAX: 101/1879 KGNV: 99/1932 KAMG: 100/1986 KCRG: 101/2016

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

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

PRELIMINARY POINT TEMPS/POPS

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

JAX WATCHES/WARNINGS/ADVISORIES

FL...Heat Advisory until 8 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. Heat Advisory from 10 AM to 8 PM EDT Friday 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 8 PM EDT this evening for GAZ132>136-149- 151>154-162-163-165-166-250-264-350-364. Heat Advisory from 10 AM to 8 PM EDT Friday for GAZ153-154-165- 166. MARINE...None.