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

- Heat Advisories for NE FL and portions of SE GA today

- Isolated strong to severe thunderstorms today and Saturday for portions of the area, mainly across southeast GA.

- Limited thunderstorms Sunday and Monday, followed by daily scattered thunderstorms Tuesday onward.

NEAR TERM /THROUGH TONIGHT/

Highlights through Tonight:

- Heat advisories in effect for portions of the area Today

- Potential for strong to severe thunderstorms this afternoon and evening

Weak surface troughing will extend south across the area Friday, from a low over the Carolinas. An upper trough will move east toward the region this period.

The combination of diurnal heating, sea breeze interactions, and a gradual increase in instability from upper trough, will yield the production of showers and thunderstorms Friday, mainly during the afternoon and evening hours. With the upper trough moving in Friday night, this activity could linger into the overnight.

As has been the case the last few days, storms which develop could become strong with isolated severe storms possible.

Above average temperatures are expected Today, with near average Tonight. Drier air will linger over inland SE GA, limiting the need for Heat Advisories there. For the rest of the area, convection may limit heat, but potential is still high enough for an advisory.

SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/

Main Highlights This Period:

- Strong to possibly isolated severe thunderstorms possible Saturday.

- Heat Advisory level conditions possible for NE FL on Sunday.

Moist, southwesterly flow remains in control through Saturday and intensifies as an upstream upper trough buckles and digs equatorward toward the region through the day Saturday. The upper wave will be accompanied by a surface front and prefrontal trough which will serve as the primary focus of convective initiation Saturday afternoon as the pinned Atlantic sea breeze focuses scattered convection along it during the late afternoon. At this time, the prefrontal trough is progged to sag across south of the Altamaha and possibly US-82 by the afternoon hours on Saturday, training and strong convective development is likely along this boundary. Cooler air aloft will support steeper mid level lapse rates and the potential for isolated pulse severe storms through the early evening hours Saturday for most of NE FL and SE GA. Main concerns will be localized flooding and wind damage related to downburst activity. Temperatures will be closer to typical heat levels for late August with highs in the low 90s and peak heat index in the 100-105 degree range.

By Sunday, the northwesterly flow will push the slowing frontal feature into SE GA where it'll stall. The drier airmass will allow dewpoints to mix out through the afternoon with temperatures soaring into the upper 90s amid the drier airmass under mostly sunny skies. Further south across NE FL, sufficient moisture will be in place to facilitate the development of isolated to scattered thunderstorms south of I-10. A few stronger storms may develop along I-95 corridor and the pinned Atlantic sea breeze during the late afternoon and early evening. While highs will be in lower 90s in NE FL, the higher mid 70s dew points may allow peak heat index to be near Heat Advisory levels prior to the onset of convection.

LONG TERM /MONDAY THROUGH THURSDAY/

Main Highlights This Period:

- Hot and dry Monday followed by increasing Thunderstorm chances Tuesday onward.

The broader pattern will keep an initially drying northwesterly flow established across the region, limit rain chances through at least Monday before deeper moisture returns by Tuesday. Expansive upper ridging centered across the southwestern US will consolidate through the middle of next week, which will "open the door" to peripheral shortwaves moving along the ridge and direct them right into the local area. Current medium range guidance has this scenario playing out Tuesday and again Thursday which should bring added forcing for ascent and result in increasing coverage in afternoon convection amid the persistent southwesterly steering flow. The hottest day will be Monday as a dry airmass heats up in to the mid/upper 90s. Above normal temperatures are expected to continue through the week with highs generally in the low 90s Tuesday onward.

AVIATION /06Z FRIDAY THROUGH 06Z SATURDAY/

VFR conditions will prevail early this period, but a little patchy fog will be possible inland.

Convection will get an earlier than usual start Today, with activity beginning during the morning inland, then spreading northeast through the afternoon and evening. Convection may linger into the night Tonight. Gusty and erratic winds will be possible in and near storms.

MARINE

A frontal zone will extend across the Carolinas and into Georgia this period, with a high pressure ridge to the southeast. Rounds of mainly afternoon and evening showers and thunderstorms can be expected each day.

Rip Currents: Offshore winds will prevail throughout the morning hours, along with low surf heights, during the next several days. With the outgoing tide occurring later in the afternoon, the overall risk will be low today and low to low end moderate this weekend as an afternoon seabreeze brings light south to southeast winds to the beaches.

FIRE WEATHER

Scattered thunderstorms are expected to develop across inland portions of southeast GA and along the sea breezes this afternoon and early evening. Additional rounds of thunderstorms are expected Saturday before drier air limits chances on Sunday and Monday. Outside of thunderstorm outflow winds, light southwesterly wind will be favored for inland areas not influenced by the east-coast sea breeze. The incoming drier air will lead to hot and dry conditions north of I-10 with afternoon humidity down in the 30-40% range Sunday and Monday afternoon. Thunderstorms chances start to ramp back up on Tuesday.

Fog Potential: Considerable fog is unlikely, and any strong wind will be associated with nearby thunderstorm activity.

CLIMATE

Less likely to push to record territory today but chances increase in near record heat by Sunday as drier airmass enters the region.

Friday, August 21st: KJAX: 101/1900 KGNV: 99/1983 KAMG: 100/1980 KCRG: 99/2016

PRELIMINARY POINT TEMPS/POPS

AMG 97 72 93 73 / 60 70 50 10 SSI 93 77 92 77 / 30 30 60 20 JAX 94 73 92 73 / 50 30 60 20 SGJ 94 75 92 75 / 40 20 50 10 GNV 93 73 90 73 / 40 20 70 20 OCF 93 74 90 74 / 30 20 60 20

JAX WATCHES/WARNINGS/ADVISORIES

FL...Heat Advisory from 11 AM this morning to 7 PM EDT this evening for FLZ021-023-024-030-031-035-038-120-124-125-132- 136>138-220-225-232-233-236-237-322-325-333-422-425-433- 522-533-633. GA...Heat Advisory from 11 AM this morning to 7 PM EDT this evening for GAZ136-152>154-162-163-165-166-264-350-364. MARINE...None.