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

- Isolated to Scattered Afternoon and Evening TStorms Today. Isolated Storms May be Strong with Gusty Winds, Heavy Rainfall, and Frequent Lightning

- Moderate Risk of Rip Currents Today

- Heat and Humidity Builds this Week. Heat Indices Could Briefly Approach 108 Today. Heat Advisories Possible Each Day from Tuesday through Friday

NEAR TERM /THROUGH TONIGHT/

Main Highlights:

- Scattered Thunderstorms This Afternoon and early Evening.

- Brief Strong Storms Possible, Wind Gusts to near 40 mph and locally heavy downpours

- Moderate Risk of Rip Currents at Area Beaches.

Calm to very light south to southeast winds early this morning as some high cirrus clouds linger with scattered low clouds inland over the Suwannee Valley and across interior SE GA. The low clouds may occasionally become broken to overcast before sunrise before lifting. Very localized fog near areas with heavy rains yesterday is not expected to expand. Temperatures in the mid 70s to the upper 80s at the coast and banks of the St Johns river will hold into sunrise. Today, mean 500 mb ridge will extend from the western Atlantic waters across the north central FL coast into the the NE Gulf waters. The surface high will correspondingly stretch across NE FL and sink into north central FL through today. Low level light southwesterly flow around the surface ridge axis will prevent much inland progress of the Atlantic seabreeze to near much past US-17 where the Gulf seabreeze will merge with it in by the mid/late afternoon hours. Some drier air will lower Precipitable water levels to near normal values of 1.8-2.0 inches and scattered T'storm coverage is expected to result along the seabreeze merger with isolated to widely scattered T'storms as the Gulf and Atlantic seabreezes move inland and temperatures rise into the lower 90s by midday to early afternoon hours. Skies will be partly cloudy with some high cirrus strewn across SE GA much of the day. Southwest winds 5-10 mph will prevail by late morning, then turn southeasterly 8-12 mph behind the Atlantic seabreeze with gusts to 15 mph at the beaches. A stronger storm may produce a brief gusty winds 35-45 mph over NE FL areas east of highway 301 where the seabreezes/outflows merge, but severe T'storm potential will be low.

Highs will peak in the low to mid 90s along and west of I-95 and around 90 at the immediate coast. Max heat index values will be around 104-108 for most locations with some isolated higher values that could briefly approach 108, but not expecting high enough values to warrant a heat advisory for today. Tonight, a few thunderstorms will linger through 8-9PM then quickly fade with mostly clear skies by midnight under thinning mid and high level debris clouds. Light southerly winds will turn calm inland and 5-10 mph at the coast, turning southwesterly in the pre dawn early morning hours. Lows will be slightly above average in the low/mid 70s inland and the upper 70s for the coast.

SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/

Main Highlights This Period:

- Daily Isolated to Scattered Afternoon Thunderstorms, some of which could be strong

- Increasing Heat Index Values near Heat Advisory levels each day On Tuesday, the ridge of high pressure will be situated over the eastern Gulf, through central FL, and into the Atlantic through the Bahamas and well to the east. This ridge will shift slightly southward into Wednesday. The position of the ridge is a little south of the climatology position for August, as a broad low level trough of low pressure is located along the U.S. east coast from about Georgia northward.

Overall, lower precipitation chances will be present Tuesday and Wednesday compared to the past few days, given some drier air in the lower to mid mid levels and some suppressive affects of a mid level ridge located just to our south. Nonetheless, deep moisture levels remain near average levels for this time of year at about 1.9 to 2.1 inches, but some pockets of drier air are located over inland northeast FL at about 1.6 to 1.8 inches. On Tuesday, prevailing flow is west-southwest so the west coast sea breeze will be dominate with the east coast sea breeze making it inland to only the I-85 corridor, but Wednesday the westerly low level flow is a little stronger and more due west so think that the east coast sea breeze will not make a whole lot of progress inland. Rain chances on Tuesday look to be about 20-30 percent, mainly along and north of I- 10, and Wednesday rain chances may be slightly higher, but generally at 20-40 percent and again preferred chances from I-10 northward, and along the east coast. The higher end chances over north zones are due to the better low level moisture located there. An isolated strong storm with gusty winds remains possible given DCAPEs approach the 800-900 J/kg range with the MLCAPE of about 2500 J/kg.

With less cloud cover and storm coverage, highs will be above normal, climbing into the lower to upper 90s. Max afternoon apparent temperatures will range from 102-108 degrees, a Heat Advisory may be needed for some locations either or both days. Can't rule out some early morning patchy fog, especially over areas that receive a lot of rainfall.

LONG TERM /THURSDAY THROUGH SUNDAY/

Main Highlights This Period:

- Isolated to Scattered Afternoon Thunderstorm Coverage

- Heat Advisory Potential Each Day

Storm chances look lower than normal Thursday, and then trending to near normal Friday through the weekend.

Prevailing westerly surface winds and increasing mean layer thicknesses due to the mid level ridge lifting northward into the the southeast states will yield above normal temperatures. Highs in the mid to upper 90s are expected, even toward the coastal areas of southeast GA and northeast FL. Max afternoon heat index values will approach Heat Advisory criteria near the coast and for some inland locations.

AVIATION /12Z MONDAY THROUGH 12Z TUESDAY/

VFR conditions prevail again with southwest winds 5-8 knots inland and near 10 knots at the coast turning east to southeasterly 16-18Z behind Atlantic seabreeze. Seabreeze will help initiate afternoon thunderstorms with VCTS noted at all sites. High pressure ridge over the area will limit overall storm chances compared to past few days.

Southerly winds after 00Z with storms ending near the coast and inland after 01Z under broken mid and high level clouds from fading storms through the end of the period.

MARINE

Atlantic high pressure will gradually build westward across our local waters today and persist through the week. Southwesterly flow will prevail over the local waters with an afternoon sea breeze developing over the near shore waters each afternoon, followed by a southerly evening wind surge. Winds and seas are forecast to remain below Caution levels this week. Only isolated afternoon and evening thunderstorms are forecast today through Friday, mainly impacting the near shore waters.

Rip Currents: The afternoon sea breeze will combine with a lingering ocean swell to produce a moderate risk at area beaches this afternoon. Persistent offshore winds will likely lower this risk by midweek.

FIRE WEATHER

- Patchy High Afternoon Dispersions Beginning Tuesday

Light west to southwest winds will keep the Atlantic seabreeze near the coast each day, with lower thunderstorm coverage expected today through Wednesday and forecast to be around 20-40%. A few strong thunderstorms may produce gusty outflows with locally erratic winds.

Temperatures will rise into the mid 90s inland and lower to mid 90s at the coast today and Tuesday with peak heat index values rising to heat advisory levels to about 106-110 into midweek. Dispersions improve gradually today compared to Sunday. Patchy high inland dispersions expected Tuesday into Wednesday as mixing heights increase along with increasing westerly transport winds. Fog Potential: Significant fog development is not expected, with shallow, patchy fog late overnight limited to areas that receive locally heavy rainfall.

CLIMATE

Daily record high temperatures are possible by Thu-Fri:

Thursday, August 13th: KJAX: 99/2023 KAMG: 100/9999 KCRG: 96/2023

Friday, August 14th: KJAX: 99/2023 KGNV: 97/2023 KCRG: 98/2023

PRELIMINARY POINT TEMPS/POPS

AMG 95 76 95 75 / 10 10 30 20 SSI 92 79 95 79 / 20 0 30 20 JAX 93 75 96 76 / 40 20 30 20 SGJ 92 76 94 76 / 30 10 20 10 GNV 93 74 95 74 / 40 10 10 10 OCF 94 74 95 74 / 20 10 10 0

JAX WATCHES/WARNINGS/ADVISORIES

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