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. Storm Hazards: Lightning, Gusty Winds up to 50 mph & Localized Flooding

- Daily Peak Heat Indices up to near 105-110F. Building heat risk potential heat advisory conditions next few days

- Moderate Rip Current Risk Beaches Today

NEAR TERM /TODAY THROUGH TONIGHT/

Main Highlights:

- Max Heat Indices to 104-109, Near Heat Advisory Criteria - Scattered convection near I-75 by mid morning, Scattered Storms this afternoon toward the east coast

Deep southwest steering flow is now estimated to be about 12-16 kts today per RAP soundings, with this flow caused by high pressure extending across south Florida and an approaching trough northwest of the region. PWATs are lower a little lower compared to yesterday, now near 1.7 - 1.9 inches. Chances of showers and thunderstorms today, initially focused close to the I- 75 corridor heavily influenced by Gulf moisture and low level convergence and the west coast sea breeze. Convection then expands inland and further east into the afternoon as instability increases. The highest daily rain chances focus near and east of the St. Johns River basin to the Atlantic coast mid afternoon into the early evening where the east coast sea breeze, river breeze and boundary mergers focus. Potential for heavier rain is lower today owing to the faster cell motions and overall weaker convergence with the pinned east coast sea breeze. This is reflected in the last 2 runs of the HREF guidance. Some isolated evening convection is anticipated which will dissipate by about 10-11 pm. After midnight, a near repeat of late night isolated convection off the Gulf, mainly showers, will move toward the I-75 corridor after about 3-4 AM Tuesday morning.

Temperatures will continue above average with highs in the mid/upper 90s and daily heat index values right near local Heat Advisory criteria of 105-109 deg, with the higher values across the St. Johns River basin of northeast FL and toward the Atlantic coast given southwest flow. At this time, no plan for a heat advisory today given some better boundary layer mixing and possible early onset of convection. Muggy overnight lows range in the mid/upper 70s inland to near 80 coast.

SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/

Main Highlights This Period:

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

Southwesterly flow persists through midweek with showers and storms building across the forecast area, developing from west to east. Convection will become less widespread on Wednesday as the influence of high pressure ridging reaching in over Florida from out of the east increases. High temperatures 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 100-105 with a potential for Heat Advisory conditions on Tuesday and Wednesday.

LONG TERM /THURSDAY THROUGH SUNDAY/

Main Highlights This Period:

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

Pattern will continue through the end of the week and into the weekend with scattered to isolated diurnal showers with embedded storms forming in the afternoon and evening hours. Inhibited convection will be in place through the end of the week with chances potentially increasing by the end of the weekend as a frontal boundary presses in towards the forecast area from out of the north. Temperatures will remain above average through the end of the week with daily max temps rising into the mid 90s. Heat index values will rise up to over 100-105 into mid-late week with a potential for Heat Advisory conditions through the period.

AVIATION /06Z MONDAY THROUGH 06Z TUESDAY/

Light winds during the overnight hours could allow for shallow fog to develop near VQQ by sunrise. Otherwise, breezy southwest winds will lead to early showers once again, as early as 12Z-14z for GNV, and further heating will develop possible BKN cumulus around 2-2.5 kft. Storms will once again develop around 17z-19z along the sea breezes with diurnal heating fueling storms. Overall chances are not too high compared to yesterday so for now will maintain the PROB30 TSRA group for aftn storms. Shower and storm chances diminish by about 00z-01z Tuesday.

MARINE

High pressure ridge will continue across central and south Florida this week as low pressure troughing develops to the north. This pattern will lead to prolonged southwesterly flow during the day followed by nightly wind surges from the south to Small Craft Exercise Caution speeds. The offshore flow will increase afternoon and evening thunderstorm chances over the local coastal waters each day through the upcoming week. Locally strong wind gusts and frequent lightning will be possible with these thunderstorms.

Rip Currents:

Surf estimated to be 1 to 2 feet with weak onshore swell will keep rip current risk at low-end moderate levels during the afternoon hours as the sea breeze develops through the first half of the week. Some enhanced rip current potential may develop from about Fernandina Beach north to Brunswick late afternoon due to the strengthened southeast flow. A similar situation on Tuesday as well with the persistent offshore flow and then south-southeast flow by the late afternoon.

FIRE WEATHER

Southwest flow continue today and Tuesday with showers and isolated storms moving inland from the Gulf Coast during the morning, spreading toward the Atlantic coast into the afternoon. The east coast sea breeze will develop and drift inland toward the I-95 corridor mid to late afternoon each day. The best chance of afternoon and evening storms each day will focus between Highway 301 and the Atlantic coast and across inland southeast GA Tuesday afternoon and evening ahead of a stalling front. Dispersion will be elevated across inland southeast GA and parts of the Osceola NF each afternoon. 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

Water levels on the Satilla River at Atkinson continues to lower and is now forecast to drop to the action stage this afternoon.

PRELIMINARY POINT TEMPS/POPS

AMG 95 76 95 76 / 30 30 30 10 SSI 94 79 95 79 / 30 10 30 10 JAX 95 77 96 77 / 40 10 30 10 SGJ 94 77 95 78 / 40 10 30 0 GNV 93 75 94 76 / 30 10 20 0 OCF 93 75 93 76 / 30 10 20 0

JAX WATCHES/WARNINGS/ADVISORIES

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