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

- A Few Strong/Severe This Afternoon & Evening Thunderstorms Inland. Hazards: Wind Gusts of 45-60 mph, Frequent Lightning & Heavy Downpours. Main Areas of Concern: Inland Northeast FL

- Increasing Coverage of Afternoon/Evening Storms this Weekend into Monday with Marginal Flood Risk for Inland NE FL

- Heat Advisory Conditions Possible Towards the Middle of Next Week

NEAR TERM /THROUGH TONIGHT/

Main Highlights This afternoon and Tonight:

- Seasonably Hot and Humid Summertime Weather Continues.

- Strong Pulse Thunderstorms possible late this afternoon for inland NE FL, mainly along the I-75 corridor; Localized Urban Flooding possible.

No changes to ongoing forecast as deep moisture over the FL Peninsula with PWATs of 2.0 to 2.2 inches will continue to drift northward this afternoon and will interact with an inland moving East Coast sea breeze front, which is expected to merge with the Gulf Coast sea breeze over inland NE FL, near the I-75 corridor. This area will be the focus for scattered strong/isolated severe storms with damaging downburst winds of 40-60 mph possible, but isolated severe storms will even be possible into inland SE GA as predicted Downdraft CAPE values are forecast to exceed to 1000J/kg over all inland areas, due to the strong surface heating and steep low level lapse rates. In addition to the isolated severe wind threat, expect the slow storm motion around 10 mph or less, high PWATs and merging sea breeze fronts to support localized/isolated rainfall amounts of 2-4 inches in the more intense storms. Activity is expected to develop in the 2-4pm time frame and linger over far inland areas until at least 8-10 pm, before ending around the midnight time frame. Expect fair skies and humid conditions during the overnight hours with patchy fog possible towards morning over inland areas that receive heavy rainfall this afternoon/evening.

Temps will continue to run slightly above normal prior to the afternoon convection, reaching the middle 90s inland and around 90F along the Atlantic Coast. A few local spots of heat indices in the 105-110 range will be possible along the I-95/US-301 highway corridors early this afternoon, but not widespread enough for Heat Advisory headlines. Elsewhere over inland areas, peak heat indices will top out around 105F. Overnight lows tonight are expected in the lower/middle 70s inland and upper 70s/near 80F along the Atlantic Coastal areas.

SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/

Main Highlights:

- Heavy Rain and Localized Flood Concerns - Daily bouts of showers and storms

A Tropical Upper Tropospheric Trough (TUTT) will be located along the west FL coast on Saturday with an embedded upper low located near Tampa. This upper low pressure center will slowly migrate north- northeast through Sunday. A weak surface low may attempt to develop beneath the upper feature and acquire some subtropical or tropical characteristics as it moves northeast on Sunday. However, confidence in surface low development remains low at this time due to model disagreement, with the National Hurricane Center maintaining a 20 percent chance of tropical development for this weekend into early next week.

The combination of the rich tropical moisture advecting into the region with PWATs 2+ inches and temperatures cooling aloft will increase afternoon and evening thunderstorm coverage this weekend. Regardless of tropical development, the deep tropical airmass will support rounds of scattered to numerous showers and thunderstorms each afternoon and evening. Best convective coverage and heavy rainfall amounts look to occur over inland areas, as the east coast sea breeze should push inland far enough to keep the bulk of the heavier storms further west and away from the Atlantic coast. The primary hazard with storms will be periods of heavy rainfall capable of producing localized flooding, especially across northeast and north central Florida where repeated rounds of convection are most likely. Frequent lightning and locally gusty winds will accompany the stronger storms.

Temperatures will remain seasonably hot Saturday, with highs in the lower to middle 90s and peak heat index values of 102 to 107 degrees. Increasing cloud cover and numerous showers and storms on Sunday should hold highs closer to the lower 90s while maintaining humid conditions.

LONG TERM /MONDAY THROUGH FRIDAY/

Main Highlights For Next Week:

- Scattered to Numerous Afternoon Thunderstorms - Potential heat advisory conditions by the middle of next week

Weak mid to upper level trough will continue across the region early next week, oriented from the eastern Gulf then northeastward over our forecast area to the Carolina coast. This upper trough looks to weaken and become less defined by mid week. Low level troughing also continues over the southeast states into the northeast Gulf early next week. Importantly, the northeast Gulf continues to be an area that is being monitored by the NHC early next week with low chances of tropical development. Still much uncertainty if anything develops given it would be close to land and models are having a hard time showing anything well-defined. As low to mid level ridging begins to build back in over the FL peninsula by Wednesday, any troughing or low pressure would shift northward. Still looks like numerous showers and storms for Monday and Tuesday, especially over northeast and north central FL. The high PWAT air of near 2 to 2.2 inches (near or above the 90th climate percentile), coupled with convergent south or southwest low level flow will support a continued localized flooding rain threat for inland areas, especially northeast and north central FL.

Coverage of convection appears to decrease slightly Wednesday and Thursday. At the same time, increasing heights aloft will allow temperatures to climb back into the middle 90s, with oppressive humidity pushing peak heat index values to about the 105 to 110 degree range by midweek. Given this, heat advisory conditions may become increasingly likely for some areas.

AVIATION /18Z FRIDAY THROUGH 18Z SATURDAY/

Sea breeze activity will push inland faster this afternoon, limiting the potential for convective impacts at KSSI, KSGJ, and KCRG as well. Main areas and terminals impacted by TSRA will be west of I-95 with increasing chances the farther west you go. Heavy rain with thunderstorms will restrict terminal visibility to IFR or less temporarily. The concentration of convection will be along the Gulf and Atlantic sea breeze merger, which will be near KGNV around 20- 22z. Expect Atlantic sea breeze to arrive around 16z at coastal terminals then KJAX/KVQQ around 18z/19z. After sunset and through the overnight hours, expect VFR conds with the low chance of MVFR fog towards sunrise at GNV/VQQ from 07-11Z, but will hold off on any inclusion at this time. A few patchy MVFR CIGS will be possible in diurnal heating Saturday morning in the 13-15Z time frame but probs continue to be too low for any inclusion at this time.

MARINE

Light flow will favor a dominant sea breeze wind pattern this afternoon and evening. This weekend southerly winds will strengthen to Exercise Caution levels as gradients increase between a trough over the southeastern US and strengthen Bermuda high pressure. As steering flow pattern turns offshore this weekend, chances for afternoon and evening thunderstorms will increase.

Surface troughing will strengthen Sunday and Monday, with weak low pressure possibly developing over the northeast Gulf. The National Hurricane Center has maintained a low chance of weak tropical disturbance development. The weak wave of low pressure should progress northeastward across our local waters early next week.

Rip Currents:

Low to Moderate risk of rip currents today with surf 1-2 feet will become a solid Moderate risk this weekend as South-Southeast flow will increase and build surf into the 2-3 feet range at all NE FL/SE GA beaches, which will likely continue into early next week.

FIRE WEATHER

- Poor To Fair Dispersions Today

Surface and transport wind speeds are forecast to be weak today which will lead to poor to fair dispersion values. South-southwest surface and transport winds increase this weekend improving dispersions to the fair to generally good range. Moisture steadily increases across region, with rain and storm chances increasing through the weekend. Rounds of heavy downpours will move through the area this weekend into early next week causing localized flooding as a tropical disturbance potentially passes through.

Fog Potential and Other Remarks: Significant fog development is not expected for the next several nights. Gusty and erratic winds will be possible in and near thunderstorms, with occasional outflow boundaries capable of producing sudden wind shifts well away from ongoing convection.

PRELIMINARY POINT TEMPS/POPS

AMG 74 94 73 93 / 50 70 50 60 SSI 79 92 78 92 / 10 20 30 40 JAX 75 94 75 93 / 20 30 30 60 SGJ 75 93 76 92 / 20 20 20 50 GNV 73 93 73 90 / 40 40 20 80 OCF 73 92 74 90 / 40 50 20 80

JAX WATCHES/WARNINGS/ADVISORIES

FL...None. GA...None. MARINE...None.