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

- Hot & Humid Weather Continues. Peak Heat Indices this Afternoon of 102-108.

- Heat Advisories Possible this Weekend and Next Week for Portions of Our Area.

- Moderate Rip Current Risk Continues at Area Beaches.

- Only Isolated to Widely Scattered Afternoon and Evening Thunderstorms Today, Mainly West of U.S.-301.

- Scattered to Numerous Afternoon and Evening Thunderstorms Saturday through Mondays. Strong to Isolated Severe Storms Will be Possible, Accompanied by Frequent Lightning Strikes and Locally Heavy Downpours.

- Only Isolated to Widely Scattered Afternoon and Evening Thunderstorms on Tuesday and Wednesday.

NEAR TERM /THROUGH TONIGHT/

Main Highlights through Tonight:

- Isolated to Widely Scattered Thunderstorms this Afternoon and Evening along the I-75 Corridor in Northeast FL and west of highway 301 in Southeast GA.

The Atlantic sea breeze is steadily pushing inland early this afternoon, with relatively cooler temperatures behind the sea breeze. With clear skies across the area, temperatures have already risen into the 90s for most locations west of the I-95 corridor. Temperatures are expected to continue to rise to the mid to upper 90s as the afternoon progresses. As the overall flow remains weak, both sea breezes will continue to push inland, merging near the I- 75 corridor in NE FL, while near highway 301 and US-221 in SE GA. Higher moisture aloft over SE GA and the Suwannee Valley Region in NE FL will likely spark a isolated to scattered showers and storms along the sea breeze mergers during the mid-afternoon to evening hours. Convective activity will begin to diminish by the early evening hours as diurnal heating cools off. Winds will begin to calm overnight. Lows this evening will dip to the mid 70s for inland locations, while the upper 70s along I-95 and east towards the coast in SE GA and NE FL.

SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/

Main Highlights This Period:

- Coverage and Intensity of Afternoon and Evening Thunderstorms Increases this Weekend.

- Strong Storms and Locally Heavy Downpours Possible.

- Heat Advisory Conditions Likely on Saturday for Portions of Our Area.

"Heat Wave" ridging will remain in place over the Four Corners region of the Desert Southwest and the Plains states this weekend, allowing for troughing to dig into the Deep South. Winds aloft will become northwesterly, shifting deeper moisture values along and ahead of a decaying frontal boundary into our area. Low level flow will become westerly on Saturday morning, which will delay the development of the Atlantic sea breeze boundary until the early to mid afternoon hours. Filtered sunshine beneath a thinning cirrus cloud deck on Saturday morning will allow highs to soar to the mid and upper 90s inland, with the delayed sea breeze allowing highs to reach the low to mid 90s all the way to coastal locations. PWATs increasing to around or even above 2 inches will not allow dewpoints to mix down below the mid 70s, and heat index values will climb to the oppressive 105-110 degree range, with Heat Advisory conditions likely being required for portions of our area, especially for coastal southeast GA and for locations along and south of Interstate 10, where convection will likely not develop until the mid to late afternoon hours.

Deepening northwesterly flow aloft will steer convection southeastward on Saturday afternoon and evening, with activity initially developing south of a stalling frontal boundary over southeast GA and then increasing in coverage and intensity as thunderstorms encounter the slow moving Atlantic sea breeze boundary over coastal southeast GA and northeast FL during the mid to late afternoon hours. Mesoscale boundary collisions will allow storms to pulse and become strong, with an isolated severe storm or two not out of the question. Plenty of instability and some increase in northwesterly speed shear will allow for stronger storms to produce downburst winds of 40-60 mph, along with frequent lightning strikes and heavy downpours. Although a southeastward storm motion should gradually increase, PWATs increasing to the 2.2 - 2.4 inch range per model soundings could present a localized flood threat, especially if heavy downpours persist over urban or low lying, normally flood prone locations.

Convection could linger into the evening hours on Saturday, especially for locations south of I-10. Unstable northwesterly flow and the presence of the stalled frontal boundary near or just north of the Altamaha River could send another wave of showers and thunderstorms southeastward across inland portions of southeast Georgia during the predawn hours on Sunday. Lows will generally fall to the mid and upper 70s region-wide.

A similar weather pattern will prevail on Sunday, although more cloud cover is expected on Sunday morning in the wake of potential predawn convection that could impact southeast GA. The frontal boundary should remain stalled just north of our area, and shortwave energy embedded in the prevailing northwesterly flow pattern should touch off another round of southeastward moving convection, especially later in the afternoon and into the evening hours, as morning cloud cover could delay the onset of showers and thunderstorms across our region. Highs should still reach the 90-95 degree range even with less insolation, with prevailing west- northwesterly low level flow again delaying the development of the afternoon sea breeze at coastal locations. Storms may again pulse as they encounter the pinned sea breeze boundary along the I-95 corridor, with strong storms possible into the evening hours, especially from I-10 southward. A drier air mass could then advect into southeast GA towards midnight on Sunday night, ending convection during the evening hours, while activity potentially extends into the overnight hours for locations south of I-10. Lows will generally fall to the low and mid 70s inland and the mid to upper 70s at coastal locations.

LONG TERM /MONDAY THROUGH FRIDAY/

Main Highlights This Period:

- Heat Advisory Conditions Possible Across Much of Our Area During the Early to Middle Portions of Next Week.

- Coverage of Afternoon and Evening Thunderstorms Gradually Decreases through Midweek.

- Increasing Coverage of Afternoon and Evening Thunderstorms Possible Late Next Week.

"Heat Wave" ridging will remain centered over the Southern Plains and Desert Southwest next week, with this feature briefly expanding into the Deep South on Tuesday and Wednesday. However, unstable northwesterly flow will bring shortwave energy into our area that will be difficult to time out, which could bring more convection southeastward into our region than model blends currently indicate. Meanwhile, a frontal boundary that will be stalled just north of our area on Monday will likely dissipate on Tuesday and Wednesday, but another frontal boundary could dive into the Deep South late next week as the "Heat Wave" ridge retreats slightly westward, resulting in troughing aloft deepening over the eastern third of the nation. This evolution of the weather pattern could potentially increase afternoon and evening convective coverage across our area, as deeper moisture pools across our area that will be south of another slow moving frontal boundary.

A drier air mass shifting into southeast GA on Monday could limit the development of afternoon and evening convection to locations south of I-10, with less afternoon and evening convection potentially spreading southward across the rest of our area by Tuesday and Wednesday, as PWATs fall back below 2 inches. Less convective coverage should allow highs to climb back to the mid and upper 90s, with heat index values possibly soaring to the 105-110 degree range, prompting Heat Advisories for portions of our area. Lows will only fall to the mid and upper 70s, with coastal locations possibly remaining near 80 degrees. High temperatures may fall back to the low and mid 90s by Thursday and next Friday as convective coverage potentially increases.

AVIATION /18Z FRIDAY THROUGH 18Z SATURDAY/

VFR conditions continue this period. Inland push of Atlantic breeze will bring winds from the east to southeast through 00Z. Southeasterly winds around 5-8 knots along the coast and variable under 5 knots inland under scattered to broken mid and high level clouds past 00Z and through 12Z. Could see lower vsbys for VQQ around 06Z.

MARINE

East to southeasterly winds will continue through the afternoon hours. A stationary frontal boundary extending from the Carolina coast westward across the deep south will begin to drift southward towards the Georgia waters this weekend, pushing the axis of Atlantic high pressure southward. This change in the weather pattern will create a prevailing offshore wind flow through the weekend and into next week, with scattered to numerous afternoon and evening thunderstorms expected across our local waters each day. A few stronger storms will be possible during the late afternoon hours, with briefly strong wind gusts, frequent lightning strikes, and torrential downpours possible. Another front will approach the waters next week with offshore southwest winds increasing to near advisory levels midweek.

Rip Currents:

A moderate risk of rip currents is expected across area beaches today due to onshore east-southeast winds this afternoon with wave heights 2 to 3 feet. A moderate risk of rip currents will continue on Saturday with southeasterly winds behind the afternoon seabreeze.

FIRE WEATHER

Only isolated to widely scattered showers and thunderstorms are forecast to develop late this afternoon and evening, mainly across southeast Georgia, the Suwannee Valley, and along the Interstate 75 corridor in north central Florida. Coverage and intensity of showers and thunderstorms will then increase during the afternoon and evening hours area-wide this weekend. A gradual decrease in afternoon and evening shower and thunderstorm activity is then expected during the early to middle portions of next week. Very hot and seasonably humid conditions will otherwise prevail, with heat advisory conditions possible across portions of our area this weekend and next week. Light westerly transport winds will prevail this afternoon across interior southeast Georgia, while easterly surface and transport winds will gradually increase from east to west across the rest of our area as the Atlantic sea breeze boundary moves inland. Surface and transport winds will shift to southwest and westerly by early Saturday morning, with transport winds shifting to northwesterly during the afternoon at inland locations. Elevated mixing heights will generally yield good daytime dispersion values at inland locations through Saturday, while fair values prevailing at coastal locations. Northwesterly surface and transport winds will then prevail on Sunday, with marginally high daytime dispersion values possible at inland locations before thunderstorm activity increases during the afternoon hours.

Fog Potential and Other Remarks: Significant fog development is not expected during the next several mornings.

PRELIMINARY POINT TEMPS/POPS

AMG 76 94 75 93 / 20 50 20 60 SSI 80 96 78 93 / 0 60 40 70 JAX 76 98 77 94 / 0 70 60 80 SGJ 75 95 77 93 / 0 50 50 80 GNV 74 97 76 94 / 10 50 40 80 OCF 75 96 77 94 / 10 60 30 80

JAX WATCHES/WARNINGS/ADVISORIES

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