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 Isolated To Scattered Thunderstorms This Week

- Daily Peak Heat Indices up to near 105-110F. Heat Advisory for Coastal Southeast GA Today. Building heat risk Wednesday onward. Hottest Part of the Day: Noon to 6 PM

- Moderate Rip Current Risk Beaches Today

NEAR TERM /TODAY THROUGH TONIGHT/

Main Highlights:

- Hot / above normal temperatures. Heat Advisory for coastal southeast GA. Other locations will see heat indices near 102-107. - Decreased rain chances today.

Typical pattern for July with southwesterly flow over the region with the Atlantic high pressure ridge over central and south FL. Mean deep layer flow sfc-500 mb is southwest or west-soutwhest about 12-16 kt based on model soundings. PWATs fairly high still up to about 1.8 to 2.1 inches, which is slightly above average. Guidance is a bit spread in the rain chances today, but overall looking at rain chances a little below normal given the warm temps aloft (-5c to -6c at 500mb) and moderate wind speeds in the low levels, which helps inhibit low level convergence. First chances of showers and storms will be inland northeast FL near and west of I-75 through about 10-11 AM, and then spread eastward and northeastward rest of the day. Cannot rule the potential for a couple of stronger storms, particularly along the Atlantic coastal interface where the sea breeze will be pinned prior to outflow/convective influence. Convection will dwindle this evening and disperse. However, another chance of a few showers late tonight near the I-75 corridor area toward early morning as moisture moves in off the Gulf.

There will be less of chance for shower/storm relief as temperatures trend well above normal, which is the lower 90s this time of year. Readings will easily push into the mid 90s today. Heat index values will be high and flirt with Heat Advisory levels, mainly across coastal southeast GA where a heat advisory will go into effect today for heat indices topping out near 107 to 110. For other locations, dew points may mix closer to 70-74 degrees (similar to Monday) expect peak "feels like" to be in the 102-107 this afternoon. Muggy overnight lows in the mid to upper 70s are anticipated.

SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/

Main Highlights During This Period:

- Decreasing rain chances and hotter temperatures

Storm chances are abnormally low for Wednesday and especially on Thursday as Saharan dust makes it's way into the region and a ridge of high pressure builds, limiting precipitation potential despite southwesterly flow. Wednesday, likely will still see some isolated activity closer to Marion/Putnam/Flagler counties and up the coast to near the Altamaha river, but overall chances are low elsewhere. For Wednesday late afternoon into the evening, CAMs highlight stronger storm potential near the northeast FL coast south of St. Augustine where sea breezes interact. Thursday, some moisture will remain over north central FL keeping potential for isolated storms, but precipitation chances remain <15% north of Gainesville/St. Augustine.

Brutally hot high temperatures expected Wednesday and Thursday as we see southwesterly surface winds and less cloud cover both days. Highs will reach the mid to upper 90s even at the immediate Atlantic coast, with heat indices reaching the 103-109 degree range both afternoons.

LONG TERM /FRIDAY THROUGH MONDAY/

Main Highlights During This Period:

- Dangerous Heat Friday through Sunday - Scattered Afternoon Thunderstorms Saturday Onward

Storm chances remain very limited on Friday, with only a ~20% chance over north central Florida as upper level ridging and drier air from Saharan dust lingers in the area. Moisture begins to recover area- wide on Saturday, with isolated showers and storms expected across the region, with a smaller area again over north central Florida showing potential for more activity. Precipitation chances gradually rise then through Monday, where numerous showers and storms will likely develop as a front approaches from the north early next week.

With less storm coverage Friday through Sunday, temperatures will be dangerously hot, highs in the mid to upper 90s area-wide with southwesterly surface winds. Maximum afternoon heat index values will be around 102-108 degrees, with a few locations each day approaching Heat Advisory conditions. With higher cloud cover and storm coverage forecast for Monday, temperatures will be more near normal in the lower to mid 90s.

AVIATION /06Z TUESDAY THROUGH 06Z WEDNESDAY/

Southwest wind pattern will continue again today with speeds enough to keep any fog and mist chances low. SW winds will begin to pick up once again around 14Z, with scattered showers and storms develop along the sea breezes. First TAF that may be affected will again be GNV by midday, then rest of the TAFs after about 17z-18z. So far, given th current guidance and expectation of chances generally below 50 percent, have maintained PROB30 groups for each of the TAF sites, with further refinement in upcoming TAF packages. Convection should be mostly dissipated by 01z or so.

MARINE

High pressure ridge will remain anchored across central and south Florida this week as low pressure troughing develops to the north. This pattern will maintain a prolonged southwest flow during the day followed by nightly wind surges from the south to Small Craft Exercise Caution wind speeds. The offshore flow will allow for a chance of afternoon and evening thunderstorm over the local coastal waters each day through the week. Mariners should expect locally strong wind gusts and frequent lightning with any developing thunderstorms.

Rip Currents:

Mainly offshore flow regime dominates the next few days. Local buoys show about 2 ft and nearer to the coast surf is estimated to be 1 to 2 feet. Primarily a wind-wave due to the enhanced winds each late aftn from the southeast. Wave spectra reveals southeast wave energy so weak to moderate longshore current is directed northward. 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 Wednesday as well.

FIRE WEATHER

- Patchy High Dispersion North Of I-10 Through The Week

Southwesterly flow will prevail through the week becoming breezy with gusts 15 to 20 mph during the afternoon hours. Drier air will be channeled from the Gulf and across NE FL and SE GA Tuesday through at least Friday, leading to progressively lower inland dew points day after day. Very hot and borderline dry conditions will be possible toward the end of the week as afternoon humidity falls below 40%. Under the southwesterly transport, the Atlantic sea breeze will be pinned close to the coast through the week and also resulting in peak dispersion reaching high levels inland.

Fog Potential and other remarks: No significant fog development expected. Erratic gusts possible in the vicinity and at a distance from area thunderstorms.

PRELIMINARY POINT TEMPS/POPS

AMG 95 76 97 77 / 20 10 20 0 SSI 94 80 95 81 / 30 20 20 10 JAX 95 77 96 78 / 30 20 20 10 SGJ 95 77 96 78 / 30 20 20 10 GNV 94 76 96 76 / 30 10 10 0 OCF 93 75 95 76 / 40 10 10 0

JAX WATCHES/WARNINGS/ADVISORIES

FL...None. GA...Heat Advisory from noon today to 6 PM EDT this evening for GAZ153-154-166. MARINE...None.