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

- Numerous Afternoon Thunderstorms Today. Strong to Isolated Severe Thunderstorms Possible [3-9 PM]. Storm Hazards: Wind Gusts of 40-60 mph, Frequent Lightning Strikes and

- Elevated Flash Flood Potential. Slow-moving, Heavy Downpours with localized amounts 3-4 Possible

- Scattered to Numerous Afternoon & Evening TStorms Each Day

- Moderate Rip Current Risk Continues at All Area Beaches

NEAR TERM /UNTIL 7 AM WEDNESDAY MORNING/

Highlights through Tonight:

- Strong to Isolated Severe Thunderstorms Possible across Southeast GA and the Suwannee Valley through Early this Evening. Stronger Storm Threats: Wind Gusts of 40-60 mph and Frequent Lightning Strikes

- Slow-moving heavy downpours will lead to an increased risk for flash flooding through early this evening across southeast GA and the Suwannee Valley.

Afternoon surface analysis depicts a wavy, stationary frontal boundary extending from coastal South Carolina westward across south central GA and then extending through the lower Mississippi Valley and the southern Plains. Meanwhile, high pressure (1018 millibars) remains situated to the south of the frontal boundary over the central Gulf, with stronger high pressure (1022 millibars) building through the Ohio Valley in the wake of this frontal boundary. Aloft...troughing continues to dig over the eastern third of the nation, with an embedded shortwave at the base of this trough progressing slowly southeastward across our area. Meanwhile, "Heat Wave" ridging remains centered over New Mexico, with this feature extending its axis southeastward across Texas and into the lower Mississippi Valley. Latest GOES-East derived Total Precipitable Water imagery indicates that tropical moisture has overspread our area since this time yesterday, with PWATs of 1.8 - 2.1 inches, which is above late August climatology for our area. A very unstable atmosphere and the presence of the shortwave trough ignited convection across northeast and north central FL just before noon today, with convective outflows migrating northward increasing the coverage and intensity of showers and thunderstorms across southeast GA, where temperatures have soar to the low and mid 90s as of 19Z. Similar conditions exist over western portions of the Suwannee Valley that have yet to experience convection, where dewpoints in the lower 70s have driven heat indices over 100 degrees. Rain-cooled temperatures have otherwise fallen through the 80s and 70s elsewhere, with dewpoints generally in the low to mid 70s across our region.

Shortwave troughing will continue to dig slowly southeastward across our area, with longwave troughing positioned along the U.S. eastern seaboard maintaining an unstable northwesterly flow aloft tonight. Convection will continue to increase in coverage and intensity in the hot and humid air mass that persists across southeast GA late this afternoon and into the early evening hours, with convective outflows expected to trigger convection across the Suwannee Valley and I-75 corridors into the evening hours as well. Colliding mesoscale boundaries should continue to result in "pulsing" convection through the early evening hours, with strong to isolated severe thunderstorms possible across southeast GA, the Suwannee Valley and portions of the I-75 corridor. Stronger storms will be capable of producing downburst winds of 40-60 mph, along with frequent, deadly lightning strikes and torrential downpours. Slow storm motion may result in localized flooding, especially if downpours persist at urban or normally flood-prone, low-lying locations. Anvil rains should otherwise persist across portions of northeast and north central FL through around sunset. Convection over southeast GA and the Suwannee Valley should then dissipate during the mid-evening hours (before midnight), but southwesterly low level flow to the south of the stalled frontal boundary should ignite nocturnal and predawn convection over Apalachee Bay and the northeast Gulf that may move onshore before sunrise on Wednesday, potentially impacting western portions of the Suwannee Valley and for locations west of Interstate 75 in north central FL towards sunrise. Debris cloud cover elsewhere will gradually thin out during the overnight and predawn hours, with lows generally falling to the low and mid 70s.

SHORT TERM /7 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/

Main Highlights This Period:

- Chance for a isolated strong to severe storms each afternoon and evening Wednesday & Thursday

A rather stagnant pattern will continue through the end of the week, as a frontal zone lingers just north of the region, and weak high pressure ridging remains across/south of our area. Upper troughing will also hold rather firm across of the north and northeastern US, with several weak shortwaves breaking off to help increase both the coverage of daily convection, as well as potential for isolated strong to severe cells, especially closer to the east coast sea breeze that will not make it much further west than about the I-95 corridor each afternoon/evening. Primary storm hazards will be gusts up to 40-60 mph, as temps aloft will be generally near climo and therefore lower chances for hail. Storm motion around or under 10 mph and PWATs over 2 inches will also favor an isolated flash flooding threat daily. High temperatures will run generally close to normal, as low 90s will be common. Deep moisture and southwest flow off the Gulf will also support a few isolated showers and perhaps a thunderstorm overnight and into the morning hours towards and west of the I-75 corridor, with generally some clearing elsewhere as lows drop into the low to mid 70s.

LONG TERM /FRIDAY THROUGH TUESDAY/

Main Highlights This Period:

- Chances For Isolated Strong to Severe Storms Continues Each Afternoon and Evening

Only minor changes in the overall synoptic pattern to end the week and through the upcoming weekend, as another frontal boundary approaches and likely stalls near southeast GA. Deep layer moisture and therefore higher coverage of showers and t'storms therefore looks to continue through this period, with gusty winds and heavy rainfall/flooding potential with isolated strong to severe cells as well.

Temperatures will trend near to slightly above average this period.

AVIATION /00Z WEDNESDAY THROUGH 00Z THURSDAY/

Showers gradually dissipate over the next couple of hours. Winds calm overnight increasing the chance for patchy fog. Best chances will be at GNV and VQQ between 09-12Z. south-southwesterly surface winds around 5 kts develop after 14Z. Winds shift to south- southeasterly after 18Z as the Atlantic sea breeze shifts inland. Another round of showers and storms will spread across the TAF sites between 18-24Z. Stronger storms will likely affect all TAF sites except GNV as the sea breezes collide near I-95 corridor.

MARINE

A stalled frontal boundary positioned just north of the Georgia waters will remain in place during the next several days. Thunderstorms developing over coastal locations will push across our local waters through the upcoming weekend, mainly during the late afternoon and evening hours, with strong to isolated severe storms possible. Offshore winds will otherwise prevail during the overnight and morning hours, with the Atlantic sea breeze shifting winds to onshore each afternoon across the near shore waters. Southerly winds will then surge each evening, with speeds briefly approaching Caution speeds around sunset outside of ongoing thunderstorm activity. Stronger high pressure building over New England this weekend will shift prevailing winds to onshore across our local waters.

Rip Currents: Although surf heights are low, generally in the 1-2 foot range, a persistent long period easterly ocean swell and onshore winds following the sea breeze will create a lower end moderate risk at all area beaches each afternoon during the next several days.

FIRE WEATHER

A frontal zone will remain nearly stationary across southern GA through the end of the week, persisting elevated chances for showers and thunderstorms each day, mainly during the daytime hours. Weak high pressure ridging across and just south of the region will keep the flow direction generally out of the south to southwest, with winds peaking during the evening and overnight hours. Another frontal boundary drops southward towards area waters this upcoming weekend, maintaining an active pattern.

Fog Potential: Significant fog is unlikely over the next several days. Gusty and erratic winds can be expected in and near thunderstorms.

PRELIMINARY POINT TEMPS/POPS

AMG 72 92 72 93 / 80 60 20 50 SSI 75 89 76 90 / 60 40 30 50 JAX 74 91 72 92 / 30 70 30 60 SGJ 76 91 74 91 / 30 40 30 60 GNV 74 91 72 91 / 30 30 20 60 OCF 74 92 72 92 / 20 20 10 60

JAX WATCHES/WARNINGS/ADVISORIES

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