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

- Flood Watch for Locations West of I-75 Through Monday Evening. Rainfall amounts of 1 to 3 inches, with locally higher amounts of 4 to 6 inches

- Numerous TStorms through Early This Week. Strong Storm Potential Each Afternoon and Evening. Daily Rounds of Heavy Downpours May Cause Localized Flooding

UPDATE

Another round of rain with some embedded thunder are currently moving across much of the area as of 745pm, with some of the stronger activity still producing wind gusts up to 35-40mph at times. This trend is likely to continue through the next few hours before a break occurs from about 10pm onward with the loss of daytime heating. Hi res guidance has overall continued to struggle with timing and magnitude of impacts with these "waves", though confidence is still high enough that showers and perhaps an isolated t'storm will continue to impact areas furthest south and west towards the Gulf overnight. Some activity will likely spread inland as well, so have kept general 30-50% PoPs closer to the east coast overnight and a bit higher the further south and west you go. Low temps will bottom out in the low to mid 70s.

SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/

Main Highlights This Period:

- Strong to severe afternoon and evening thunderstorms - Isolated Pockets of Heavy rainfall with a localized flooding potential

A stalled frontal boundary will remain positioned across northern Georgia on Monday while broad high pressure persists to the south, maintaining deep southwesterly flow and anomalously high moisture across northeast Florida and southeast Georgia. An upper level trough over the southeastern United States will provide additional synoptic scale lift. Combined with deep tropical moisture, strong daytime heating, and abundant instability, this pattern will support multiple rounds of showers and thunderstorms throughout the day. Locally heavy rainfall will remain the primary concern, with repeated rounds of convection capable of producing localized flooding, especially near and west of the Interstate 75 corridor where storms may repeatedly track over the same areas.

Monday will feature the greatest potential for widespread showers and thunderstorms and the highest risk for excessive rainfall. The Weather Prediction Center continues to highlight portions of the Suwannee Valley and the Interstate 75 corridor in a Slight Risk for Excessive Rainfall. Rain chances will peak from late morning through early evening, with widespread convection expected across the forecast area. A few storms may become strong to locally severe, producing wind gusts of 40 to 60 mph, frequent lightning, torrential rainfall, and localized flooding. Extensive cloud cover and precipitation will keep afternoon highs below early August normals, generally in the upper 80s to lower 90s. Breezy southwesterly winds will persist through the day, with overnight lows settling into the lower to middle 70s.

By Tuesday, the mid level trough is forecast to evolve into a closed low over the Tennessee River Valley and northern Georgia while the frontal boundary gradually weakens as it sags southward into central Georgia. Although synoptic scale forcing will diminish, abundant tropical moisture and strong daytime instability will remain in place, supporting another round of scattered to numerous afternoon and evening thunderstorms. Rain chances will decrease slightly across inland southeast Georgia and areas west of the Highway 301 corridor, while remaining elevated at 60 to 80 percent across locations east of Highway 301 where deeper moisture and sea breeze interactions will maintain greater convective coverage. With increasing sunshine between periods of convection, afternoon highs will climb into the lower 90s, allowing peak heat index values to approach 105 degrees across portions of inland northeast Florida before thunderstorms develop.

LONG TERM /WEDNESDAY THROUGH SUNDAY/

Main Highlights This Period:

- Isolated strong to severe thunderstorms possible each afternoon and evening

The overall pattern will transition toward a more typical summertime regime as the frontal boundary dissipates and high pressure gradually builds across the southeastern United States and the western Atlantic. The Atlantic ridge will strengthen through the latter half of the week while tropical moisture and weak embedded shortwave disturbances continue to support daily afternoon and evening thunderstorm development. Midweek will mark the transition back to a more east to southeast boundary layer flow, allowing the Atlantic sea breeze to once again become the primary focus for convective initiation and inland storm focus of higher POPs.

From Wednesday through Thursday, the Atlantic surface ridge axis will lift into southeast Georgia, establishing a southeasterly low level flow that will push the Atlantic sea breeze progressively farther inland each afternoon. Thunderstorm development will become focused along sea breeze collisions, with the favored corridor extending from the Highway 301 corridor westward toward the Interstate 75 corridor. Scattered showers and thunderstorms remain expected each afternoon and evening, with rain chances settling into the 40 to 60 percent range on Wednesday before decreasing slightly to 35 to 50 percent on Thursday. Although storm coverage will be lower than earlier in the week, a few storms may still become strong, producing gusty winds, frequent lightning, torrential downpours, and localized flooding. Temperatures will gradually warm into the lower to middle 90s inland, while peak heat index values rise into the 102 to 107 degree range, especially where convection develops later in the afternoon.

By Friday and Saturday, the Atlantic ridge becomes firmly established over the Mid Atlantic states, resulting in a persistent easterly flow across southeast Georgia and northeast Florida. This pattern will shift the greatest thunderstorm coverage farther inland, generally along and west of the Highway 301 corridor, while lowering rain chances near the Atlantic coast. Scattered afternoon and evening thunderstorms will continue each day, driven primarily by daytime heating and sea breeze interactions, with rain chances generally ranging from 40 to 60 percent. Temperatures will remain seasonably warm, with highs in the lower to middle 90s inland and the upper 80s to around 90 degrees at the beaches. Heat index values will continue to approach 105 degrees across portions of inland northeast Florida and north central Florida. Confidence remains high in the evolution toward a more typical summertime onshore flow pattern, although some uncertainty remains regarding the timing of embedded shortwave disturbances and the strength of the upper ridge, which will influence the daily coverage and intensity of thunderstorms.

AVIATION /00Z MONDAY THROUGH 00Z TUESDAY/

Another round of RA with some embedded TSRA will continue to move northeastward and across most terminals over the next 2-3 hours, with gusts up to 25-30 knots possible as well brief MVFR or IFR vsbys at times in heavier downpours. Periods of SHRA/RA will also affect sites closer to the Gulf coast overnight, spreading northeast once again towards morning. Confidence is moderate at best with respect to timing and extent of impacts with activity overnight, though for now ave included only VFR impacts from RA/SHRA through Monday Morning. A brief lull in the winds are also occurring this evening, though expecting winds to pick up towards 10 knots with higher gusts towards Monday Morning as the next round of SHRA and TSRA move inland. Confidence is similarly lower than desired with respect to the next "wave" of activity Monday afternoon, but high enough to include PROB30 groups at all airfields.

MARINE

A cool front moving through the southeastern US will shift into Georgia today and stall through mid-week. Small Craft Advisory conditions this afternoon will continue through early Monday morning as a prevailing southwesterly offshore wind flow persist into mid- week. High coverage of mainly afternoon and evening thunderstorms are expected to continue through Tuesday, with a few strong storms possible each afternoon and evening.

Rip Currents: Prevailing offshore winds through Tuesday will likely yield a low to low-end moderate risk at area beaches.

FIRE WEATHER

Main Highlights This Period:

- Daily potential for strong to severe thunderstorms, with gusty and erratic winds, along with heavy rainfall and flooding

- Patchy high dispersions inland Tuesday

Deep tropical moisture combined with persistent southwesterly flow will support numerous to widespread showers and thunderstorms through Monday, with scattered to numerous thunderstorms continuing on Tuesday. Outside of convection, southwesterly winds of 10 to 15 mph with gusts of 20 to 25 mph are expected across northeast Florida, while lighter winds prevail across southeast Georgia. Dispersion values will generally range from fair to good through Monday as increased transport winds offset lower mixing heights associated with extensive cloud cover and precipitation. Patchy high dispersion values will be possible across inland northeast Florida on Tuesday as mixing improves.

Fog Potential: Significant fog development is not anticipated through Tuesday morning due to persistent cloud cover, elevated low level moisture, and continued boundary layer mixing. Fire weather operations should anticipate sudden and erratic wind shifts, strong outflow winds, and dangerous cloud to ground lightning in and near thunderstorms.

PRELIMINARY POINT TEMPS/POPS

AMG 73 86 71 91 / 50 60 40 30 SSI 76 87 76 90 / 40 70 30 60 JAX 73 87 73 91 / 40 60 30 60 SGJ 75 88 74 90 / 20 60 30 80 GNV 72 85 72 90 / 50 80 50 50 OCF 73 86 73 90 / 50 80 50 60

JAX WATCHES/WARNINGS/ADVISORIES

FL...Flood Watch through Monday evening for FLZ021-035-236-340-522. GA...None. MARINE...Small Craft Advisory until 11 AM EDT Monday for AMZ450-452-470- 472.