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 Thunderstorms throughout the week. A few strong storms capable of lightning, gusty winds and localized flooding. Storms still possible, but less coverage between Wednesday-Saturday

- Daily Peak Heat Indices up to near 105-108F. Building heat risk potential localized heat advisory conditions Tuesday onward. Hottest Part of the Day: 2-6 PM

- Moderate Rip Current Risk Beaches Today

NEAR TERM /THROUGH TONIGHT/

Main Highlights:

- Max Heat Indices to 100-108, Near Heat Advisory Criteria - Scattered Storms this afternoon toward the east coast

Deep southwest steering flow continues with high pressure ridge axis stretching across central/south FL. Plenty of moisture remains with PWATs in the 1.9 - 2.2 in. range according to GOES satellite estimates. Convection developed early this morning in the Gulf has shifted northeastward in the southwest flow. Scattered showers and storms will continue to shift inland toward the Atlantic coast through the early evening hours. Strongest storms will likely be in the St Johns river basin and NE FL coastal counties later this afternoon as the Gulf sea breeze interacts with the St Johns river breeze and pinned Atlantic sea breeze. A few storms linger over inland SE GA this afternoon. Activity gradually wanes later this afternoon into evening and shifts into the Atlantic ocean. With the Atlantic sea breeze pinned just off the coast, activity may shift into the Atlantic ocean by 5 PM and focus stronger storms just offshore. If that occurs, a few waterspouts could develop in the nearshore waters. 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. Highs today will rise to the low/mid 90s with heat indices in the 100-107 F range, with the higher values across the St. Johns River basin of northeast FL and toward the Atlantic coast given southwest flow. A few coastal locations may hit Heat Advisory criteria but not widespread enough to warrant a Heat Advisory. Overnight lows will be in the mid/upper 70s.

SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/

Main Highlights Tuesday and Wednesday:

- Decreasing rain chances and hotter temperatures - Low Confidence of Heat Advisory Levels, but High Confidence in 100- 107 heat index Tuesday and Wednesday

While southwesterly flow remains through midweek, a dry tap over the northwestern Gulf will be advected into NE FL and SE GA. While this won't eliminate chances for showers and thunderstorms, it will reduced the expected to coverage to more widely scattered afternoon thunderstorms. Cannot rule the potential for a few strong storms as well, particularly along the Atlantic coastal interface where the sea breeze will be pinned prior to outflow/convective influence. As the belt of dry lays across the area into Wednesday, rain chances will continue to be limited to areas where deeper moisture exists. These areas may be along the Altamaha River, portions of North Central FL, and along the merging sea breezes. PoPs for Wednesday were increased to around 30% for the beaches and coastal waters, favoring MOS guidance.

Given the incoming drier air, there will be less of chance for shower/storm relief as temperatures trend well above normal, which is the low 90s this time of year. Readings will easily push into the mid 90s Tuesday and upper 90s by Wednesday as morning boundary layer is mixed out. Heat index values will be high and flirt with Heat Advisory levels but if dew points mix closer to 70 degrees expect peak "feels like" to be in the 100-105 range each afternoon.

LONG TERM /THURSDAY THROUGH MONDAY/

Main Highlights Thursday through Sunday:

- Dangerous Heat Possible - Scattered Afternoon Thunderstorms

Moist southwesterly flow will remain in place and strengthen through the end of the week as a series of mid level shortwaves are deflected to the north and enhance a stationary surface trough. Gradients will tighten between the surface trough to the north and a ridge axis laid out across central FL. Stubborn upper ridging over FL will likely suppress deep convection and available convective energy somewhat due to subsidence and weak mid level lapse rates. However, rounds of typical summertime convection is likely given the support of near climo PWAT values. Heat will be the other contending weather factor that is much less certain given the early convective cooling that tends to occur with southwesterly flow. There is a chance that temperatures will push into the upper 90s into the weekend and push daily peak heat index to Heat Advisory levels, especially toward the I-95 corridor where convective cooling will take longer.

AVIATION /18Z MONDAY THROUGH 18Z TUESDAY/

Showers and storms have shifted inland past GNV and into the JAX metro and coastal sites. Activity looks to be ending earlier than previously forecast with storms shifting offshore mostly by 21-00Z. Have TEMPOs in for brief breezy winds and lower conditions from passing storms between 18-20Z for JAX, CRG and SGJ. SW winds around 10 kts outside of storms subside to less than 5 kts overnight.

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

- Patchy High Dispersion Today And Tuesday North Of I-10

Southwesterly flow will prevail through the week becoming breezy with gusts 15 to 20 mph during the afternoon hours. Widespread thunderstorm chances today will be followed by suppressed activity through at least Friday. 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 76 95 77 96 / 20 20 10 20 SSI 78 94 80 95 / 20 30 20 20 JAX 76 95 78 97 / 20 30 20 20 SGJ 77 94 77 95 / 30 30 20 20 GNV 76 95 76 95 / 10 30 10 10 OCF 75 93 76 94 / 10 30 10 10

JAX WATCHES/WARNINGS/ADVISORIES

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