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

- Scattered to Numerous Thunderstorms this afternoon and evening. Main Hazards: Wind gusts up to 50 mph, frequent lightning, locally heavy rainfall.

- Hot and Humid Conditions Continue into Next Week. Heat Advisory headlines possible.

UPDATE

A few things to note on with this morning's observations, but the main difference today will be a slight drop in available moisture for afternoon convection. Though precipitable water was measured at nearly two inches this morning (around the "top- end" of climo at the 90th percentile), there should be a small pull-back with "less moist" air advecting overhead on deep westerly flow. Otherwise, sufficient instability and a westerly steering flow will focus the best chances along the I-95 corridor and the Atlantic coast during the mid afternoon. Anticipate showers and isolated t'storms to begin to initiate around 12 PM in the westerly dominant flow with individual cells moving around 20 mph while trekking eastward.

Still tracking another day of triple digit peak heat index readings prior to the showers and scattered convection. Still doesn't appear that it'll be hot enough to hoist a Heat Advisory for this afternoon.

NEAR TERM /THROUGH TONIGHT/

Main Highlights Today and Tonight:

- Hot and humid with less storm coverage this afternoon/evening - Heat indices 104-108F NE FL/coastal SE GA and 102-106F inland SE GA

Current PWATs in the 2.0-2.3 inch range will shift into the Western Atlantic and will be replaced by more seasonable PWATs in the 1.7-2.0 inch range by this afternoon as West to Southwest steering flow continues. This will lower storm chances slightly this afternoon into the 30-50% range with mainly scattered storms between the I-95 and US-301 corridors as storms will continue movement towards the Atlantic Coast and interact with the East Coast sea breeze along the I-95 corridor and still expect strong to isolated severe storms with gusty winds to 40-60mph. Lower rainfall coverage will lessen the overall flooding threat, but heavy rainfall still possible with quick 1-2 inch totals still possible. Timing of storms still in the 2-8pm time frame.

Models are not in good agreement with rainfall chances and/or timing today, so this will impact potential for Heat Advisory headlines. Guidance is generally supporting lower 90s inland SE GA and Heat indices of 102-106F, and more into the middle 90s for coastal SE GA and most of NE FL with Heat Indices of 104-108F. With abundant clouds to start the day and the trend for the models to under estimate the amount of afternoon convection, will hold off on any Heat Advisory headlines with this package, but any trends towards lower PWATs and delayed and/or lower storm coverage a Heat Advisory may be required for portions of the I-95/US-17/US-301 corridors of coastal SE GA and portions of NE FL to the Atlantic Coast with the pinned East Coast sea breeze.

Tonight, any lingering convection in the evening hours should fade earlier than previous nights and end or push into the Atlantic just after sunset. Skies will likely become mostly clear with muggy overnight lows in the middle 70s inland and upper 70s/near 80F along the Atlantic Coast. Lower coverage of rainfall Monday afternoon should lead to lower chances for any fog potential late Monday Night.

SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/

Main Highlights This Period:

- Slightly lower rainfall coverage Tuesday and Wednesday - Heat Advisory conditions possible

Drier air associated with high pressure from out of the north will extend over the forecast area on Tuesday and Wednesday. Models differ on how far south the associated boundary will advance over southeast Georgia and into northeast Florida, however it is expected that convective developments for this period will be reduced compared with earlier in the week with scattered showers and storms following the predominantly zonal flow pattern with stronger developments anticipated along the sea breeze boundaries and areas of collision with more widespread developments occurring . High temperatures going into midweek will be in the lower to mid 90s over southeast Georgia and in the mid to upper 90s over northeast Florida. Overnight low temperatures will drop down into the lower to mid 70s over inland areas and in the mid to upper 70s along the coastline. Heat index values are expected to rise to be over 100 with a likely chance for Heat Advisory conditions on Tuesday and Wednesday.

LONG TERM /THURSDAY THROUGH SUNDAY/

Main Highlights This Period:

- Daily heat indices near 105 - Weekend heat index near 110 inland, possible Heat Advisory - Daily thunderstorm risk, less weekend coverage

Daily mainly afternoon and evening showers and storms will continue with with decreasing coverage after Thursday when more widespread activity develops by afternoon with a slow-moving, southward- advancing surface front interacts with sea breezes under a moist and unstable airmass as an upper level short wave trough moves over the region.

By Friday, less rainfall coverage is expected across southeast GA as much drier air (below the 10th percentile for preciptable water) invades Friday into the weekend as an upper level ridge builds across the eastern GOMEX. Rain chances across southeast GA will be generally < 20% by late weekend with higher daily rain chances of 30- 40% will focus across northeast FL with a more dominant west coast sea breeze regime under westerly steering flow. This pattern will bring late morning and early afternoon convection inland across the Suwannee River Valley with the sea breeze merger focused toward the Atlantic coast in the late afternoon and early evening where isolated stronger storm potential will be greatest near boundary mergers.

With lower rain chances and building thicknesses under the mid level ridge, temperatures and daily heat indices increase. Highs in the low to mid 90s daily with heat index values 105-110, peaking this weekend. Local heat advisory criteria of 108-112 degF maybe reached at times. Muggy overnight lows range in the 70s.

AVIATION /12Z MONDAY THROUGH 12Z TUESDAY/

Mainly VFR cloud cover this morning will persist through this morning. There could be a short duration MVFR ceilings this morning between 12z-14z. For the afternoon convection, it appears it'll be lower coverage this afternoon but decent chances (40-50%) for TSRA along the coast this afternoon between 19z-24z. Upgraded a few airfields (KSGJ/KCRG/KGNV) to TEMPO groups for convection in the afternoon window. With lower confidence at remaining sites, PROB30 groups have been maintained. Convection will bring potential for gusty and erratic winds, IFR visibility with the downpours and lower ceilings. Activity will diminish after sunset with perhaps a few lingering showers until midnight; however, VFR conditions are expected overnight.

MARINE

A predominant offshore southwest flow will remain in place this week as frontal boundaries push through the SE US states but continue to stall north of the local waters and high pressure ridge axis remains south of the region. Periods of stronger southwest winds close to Small Craft Exercise Caution levels will be possible during the evening hours. Main threat to boaters will continue to be any offshore moving storms with gusty winds and frequent lightning, mainly during the afternoon and evening hours.

Rip Currents:

Rip current risk is expected to remain on the low side with the predominant offshore flow and surf/breakers 1-2 ft early this week.

FIRE WEATHER

- Areas Of High Daytime Dispersion Values On Today And Tuesday

Scattered showers and thunderstorms expected today with a potential for locally heavy rainfall, cloud-to-ground lightning, and gusty winds at times. More reduced chances of showers and thunderstorms anticipated for Tuesday and Wednesday, as drier air moves into the region. Areas of higher daytime dispersion values are expected for portions of southeast Georgia and northeast Florida today and Tuesday due to higher transport wind speeds and mixing heights.

FOG POTENTIAL AND OTHER REMARKS: Areas that receive heavier rainfall may also experience patchy late-night and early-morning fog.

PRELIMINARY POINT TEMPS/POPS

AMG 92 74 91 73 / 40 20 30 10 SSI 92 77 95 77 / 40 20 30 20 JAX 94 75 97 77 / 40 20 20 30 SGJ 94 76 97 77 / 40 20 20 20 GNV 94 75 95 76 / 30 10 10 10 OCF 94 74 95 77 / 20 10 10 10

JAX WATCHES/WARNINGS/ADVISORIES

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