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

- Daily Afternoon & Evening Thunderstorms. Highest coverage over north central and Northeast FL this weekend. Storm Hazards: Lightning, Gusty Winds around 50 mph, & Localized Flooding

- Hot Holiday Weekend Daily Peak Heat Indices: 105-109F. Heat Advisory Today Eastern Zones. Building heat next week potential heat advisory conditions

- Moderate Rip Current Risk At Area Beaches Today

NEAR TERM /TODAY THROUGH TONIGHT/

Main Highlights:

- Peak Heat Indices around 105-109, Heat Advisory Potential - Afternoon & Early Evening Storms Today - Moderate Rip Current Risk Today

Today will see the start a slightly stronger southwest deep steering flow with heat rising through the day and a good chance of showers and storms for the eastern zones through the afternoon hours. West coast sea breeze will be dominant with convection starting well inland then spreading east and northeast during the afternoon. Merging of west coast and east coast sea breeze will be best over northeast FL after about the 2-3 pm time frame. With some dry air in the mid levels, the main concerns with storms will be strong downburst winds and lightning. Storm motion is also only about 6-10 kt so localized flooding rainfall is possible, but model signal from the HREF not as strong as yesterday for this hazard. Nonetheless, a quick 2-3 inches of rain possible as PWATs are pushing just above 2 inches. Precip chances should fade in the evening, but some weak convection may push toward the I-75 corridor well after midnight given the fairly moist airmass and low level convergence coming in off the Gulf.

Max temperatures expected to be above average with highs in the mid to upper 90s, even the low/mid 90s at the beaches with a delayed east coast sea breeze start compared to recent days. This building heat combined with elevated dew pts will created heat index values in the 105-110 deg range, near to just above Heat Advisory criteria for zones east of Highway 301 and toward the coast. Have come with some areas of 107 to 109 in our forecast grids, and since it's close with outdoor activities, opted to issue heat advisory for the eastern zones starting at 11 AM. However, precip could potentially hold back the max heat indices a bit. Muggy overnight lows range in the 70s inland to near 80 coast.

SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/

Main Highlights This Period:

- Daily Max Heat Indices 105-110, Heat Advisory Potential - Daily Afternoon & Early Evening Storms

Prevailing flow will be from out of the southwest for the beginning of next week resulting in scattered showers with embedded storms building in the afternoon and evening hours, with stronger developments expected over north central Florida and for areas south of the I-10 corridor. PWAT values are expected to vary greatly on Monday and Tuesday with values transitioning between as low as 1.5 inches and 2.4 inches, with convection likely to be more inhibited during periods of lower moisture. High temperatures for the end of the weekend and into the beginning of next week will be in the mid to upper 90s for inland areas and in the upper 80s and lower 90s for areas nearer to the coast. Overnight low temperatures will drop down into the mid 70s for inland areas and in the upper 70s for areas along the shoreline and near the St Johns River. Heat index values will rise up to over 100 with a potential for Heat Advisory conditions on Monday and Tuesday.

LONG TERM /WEDNESDAY THROUGH SATURDAY/

Main Highlights This Period:

- Above Average Temperatures with High Heat Index Values - Daily Thunderstorm Chances

The daytime sea breeze will be pinned closer to the coast through end of the week as prevailing flow continues to be mainly out the south and southwest while high pressure ridging extends over the Florida peninsula from out of the east. Daily bouts of convection will continue through the extended period with PWAT values over over the forecast area vary between 1.5 and 2.3 inches , with convection potentially becoming less widespread due to drier air mixing in and as the high pressure ridging from the east enhances over the region and shifts northward by Saturday. Temperatures will remain above average through the end of next week with daily max temps rising into the mid 90s. Heat index values will rise up to over 100 into midweek next week with a potential for Heat Advisory conditions through the period.

AVIATION /06Z SUNDAY THROUGH 06Z MONDAY/

Light to calm winds expected through the early morning. The light winds and clearing skies may enable lower vsbys for inland sites. Winds will continue mainly from the southwest today to about 7-10 kt, with a sea breeze wind shift to southeast for SSI and SGJ expected during the aftn. Showers and storms will move from the southwest to northeast, with convective activity likely to increase near and after 17z. Convective chances will diminish for GNV by about 21z-22z, but will linger for rest of the TAFs until about 01z. Likely impacts to TAF sites is not certain, but recent guidance suggests transitioning to TEMPO groups around JAX TAFS, with further refining in upcoming TAF packages.

MARINE

High pressure ridge will build across central and south Florida this weekend into early next week with a transition to a prolonged south to southwest flow over the local waters through next week. This will increase afternoon and evening thunderstorm chances over the local waters. Evening and nightly wind surges are expected with near exercise caution levels developing by Sunday night and again the next several nights.

Rip Currents:

Overall risk appears to be on a downward trend so will highlight a moderate risk for all area beaches today. Surf looks to be about 1-2 ft, but may get a slight bump up as winds turn south-southeast during the afternoon hours. NWPS rip current probabilities look to be under 50 percent. Main favored areas for rips will be near jetties, sandbars, inlets, and piers this afternoon. Conditions look similar for Monday.

FIRE WEATHER

Southwest flow will continue today and Monday with showers and isolated storms moving inland from the Gulf Coast through late morning. The east coast sea breeze will develop and drift inland toward the I-95 corridor mid to late afternoon. The best chance of afternoon and evening storms each day will focus between Highway 301 and the Atlantic coast. Dispersion will be elevated across inland southeast GA and parts of the Osceola NF on Monday. Daily heat index values will approach 105-110 deg. Afternoon minimum humidity will continue above critical values.

Fog Potential and other remarks: Patchy inland fog each morning around sunrise is possible, especially where rainfall recently occurred. Thunderstorms will be capable of producing lightning, torrential rainfall, and erratic wind gusts during the afternoon and evening.

HYDROLOGY

Satilla River at Atkinson will remain in Minor Flood through the Sunday and is forecast to lower into action stage Monday morning.

PRELIMINARY POINT TEMPS/POPS

AMG 97 75 95 77 / 30 20 40 20 SSI 95 79 94 80 / 30 20 30 10 JAX 96 77 96 77 / 50 20 40 10 SGJ 94 77 95 77 / 40 20 40 0 GNV 93 75 94 75 / 30 10 30 0 OCF 92 75 93 75 / 30 30 40 0

JAX WATCHES/WARNINGS/ADVISORIES

FL...Heat Advisory from 11 AM this morning to 7 PM EDT this evening for FLZ024-038-124-125-132-137-138-225-232-233-237-325- 333-425-433-533-633. GA...Heat Advisory from 11 AM this morning to 7 PM EDT this evening for GAZ153-154-165-166. MARINE...None.