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

- Widely Scattered Showers and Thunderstorms Today. Isolated Strong Thunderstorms Possible. Hazards: Gusty Winds 40-60 mph. Limited Storm Coverage Wednesday to Friday

- Seasonably Hot Conditions Continue With Peak Heat Index Values 102-108

- Moderate Rip Current Risk Today and Wednesday, lower risk Thursday

- Small Craft Advisory Conditions Begin this Afternoon

NEAR TERM /THROUGH TONIGHT/

- Seasonably Hot Summer Conditions

- Isolated strong storms capable of strong outflow wind gusts this afternoon

Overall, a similar strong southerly flow pattern will be in place again today between westward moving Tropical Storm Bertha in the northern Gulf and the western extension of the Bermuda ridge. A dry air intrusion in the mid to lower levels will lead to a sharp reduction in coverage this afternoon with generally isolated to scattered thunderstorms developing through the afternoon hours.

With precipitable water falling between the 10th and 25th percentile and only marginally sufficient mid level lapse rates, the threat of severe convection will be dampened. However, the prevailing southerly flow around 20-25 mph and the potential for strong downbursts (DCAPE > 1000 j/kg) will exist even with marginal convective developments. Available instability will be a limiting factor but outflow sea breeze convergence during the mid to late afternoon may be enough to overcome it, allowing a few strong pulses to develop. If (a big "if") strong convection can mature, the resulting downbursts will drop into steep near-surface lapse rates and may lead to localized gusts up to 60 mph.

Temperatures will again be seasonably hot as highs push toward the mid 90s this afternoon. Heat index will push well into the 102-108 degree range today and may flirt with Heat Advisory levels along the immediate coast as dewpoints rise with the sea breeze. Due to the very localized nature, elected to continue without adding any heat- related headlines this morning.

Though a few showers may linger after the sun sets, the bulk of the diurnal convection will fade quickly with the loss of heating. While low level flow remains elevated, overnight low temperatures will again be above normal general in the mid 70s inland and upper 70s at the coast.

SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/

Main Highlights This Period:

- Drier conditions on Wednesday - Isolated to Widely Scattered Thunderstorms return Thursday Afternoon

Wednesday, high pressure ridging will work back eastward over the FL peninsula as Tropical Storm Bertha shifts further west over the northern Gulf waters near the central Gulf coast. Drier air in the low/mid levels will linger over the area as Bertha moves further away and will greatly reduce pops leading to a dry day along the coast and only widely isolated thunderstorms west of US-441/221 in SE GA and west of the Suwannee River in NE FL.

Southerly winds will become more south southwesterly during the afternoon as surface high pressure surface ridge axis extends into central FL and breezy 10-15 mph with gusts to 20-25 mph with the elevated pressure gradient. Breezy winds and partly cloudy skies will allow highs to reach the mid 90s for most of the area except the Suwannee valley where onshore flow from the Gulf will limit highs to the low 90s there and along the immediate coast. Dewpoints mixing out to around 70 north of I-10 and low 70s over NE FL will limit heat index values to 100-104 and 102-106 along the coast where dewpoints stay in the mid 70s.

Thursday, moisture levels will increase to near normal as a cold front sinks south of the TN valley into northern GA with a return of isolated to widely scattered thunderstorms across SE GA and isolated storms along the Atlantic seabreeze moving into the I-95 corridor in the afternoon and just past US-17 corridor by late afternoon. Similar highs are expected in the mid 90s with low 90s at the coast and Suwannee Valley behind the Advancing seabreezes.

LONG TERM /FRIDAY THROUGH MONDAY/

Main Highlights This Period:

- Scattered to Numerous Afternoon Thunderstorms, Especially Friday into the Weekend - Potential Heat Advisory Conditions Late Week & Weekend

The cold front will stall north of the area near central GA Friday with weak SW flow and moisture levels increasing above normal with support scattered thunderstorm chances across SE GA and less chances further south away from the front.

Shortwave energy shifting ESE across the southern Appalachians to the Carolina coast will help amplify a trough over the Mid Atlantic and southeast coast, and will allow the front will sink into SE GA Saturday and then sink into NE FL Sunday where it will stall into Monday. The front will bring increasing chances for showers and thunderstorms with numerous thunderstorms across SE GA Sunday and portions of NE FL on Monday. West to WSW flow will become a bit breezier late this weekend as a low develops near the NC coast on Sunday and lifts away to the NE on Monday.

Highs during the period will be above normal in the mid 90s Friday and Saturday, with low 90s on Sunday due to more clouds from the front and low to mid 90s Monday with more partly cloudy skies. Heat index values will approach heat advisory levels by this weekend into Monday as dewpoints remain in the mid to upper 70s each afternoon with values 104-108.

AVIATION /12Z TUESDAY THROUGH 12Z WEDNESDAY/

VFR conditions will be the prevailing sky condition outside of shower/thunderstorm occurrences today. Convection will be stunted by incoming dry air aloft but isolated to scattered thunderstorms are still possible at area terminals. Due to the decreased coverage, the forecast still keeps potential for terminal impacts due to storms around 20-40% through 18z-00z this afternoon and evening. Southerly winds will increase again, becoming gusty after 15z, with peak gusts around 20-25 knots. Given the dry air aloft, in the slim chance scenario of robust convection developing in vicinity of terminal airspace (about 10 miles) there will be potential for strong localized wind gusts in excess of 35 knots produced by downbursts.

MARINE

Breezy southerly winds between the tropical storm Bertha and the Bermuda high will lead a couple more days of breezy conditions. Winds will increase to Small Craft Advisory levels this afternoon and remain elevated through early Wednesday. Seas will rise toward 5 or possibly 6 feet today in response to the winds. Relaxing winds are expected Wednesday night as flow generally trends offshore as a weak cold front approaches from the northwest. The front is likely to stalls north of the waters this weekend as waves of low pressure track along it. Though offshore flow will be in place from Thursday onward, afternoon winds in nearshore waters will be driven by the coastal sea breeze development each afternoon.

Rip Currents:

Increasing southerly winds along with sea breeze development will push elevated wind waves into the coastline this afternoon along with strong longshore. Given a minimal onshore swell, the rip current risk will be on the upper-end of Moderate this afternoon but not quite High Risk. Moderate risk is likely again Wednesday before falling Thursday.

FIRE WEATHER

- Areas Of High Daytime Dispersions Through Midweek Inland

Tropical Storm Bertha will move slowly westward away from the area today across over the northern Gulf waters with breezy southerly winds 15-20 mph and gusts to 25-30 mph. Atlantic seabreeze will move slowly onshore only to I-95 by mid afternoon. Scattered showers will lift from the Gulf coast over the Suwannee Valley into western Southeast Georgia late this morning with scattered afternoon storms. A few storms may be strong with gusty and erratic winds as they move quickly northward. Mainly dry conditions expected on Wednesday as surface high builds over the Florida peninsula with breezy southerly winds continuing. A frontal boundary will approach on Thursday with isolated to scattered thunderstorms during the afternoon hours through Friday. Increasing thunderstorm chances expected this weekend as the front sinks into the area.

Breezy surface and transport winds today and Wednesday will create areas of high dispersions across the area each day away from the coast.

Fog Potential and Other Remarks: Significant fog development is not expected for the next several nights. No significant impacts expected from Tropical Storm Bertha.

PRELIMINARY POINT TEMPS/POPS

AMG 94 75 94 75 / 30 10 10 10 SSI 92 81 94 80 / 20 20 0 0 JAX 95 77 96 76 / 40 20 0 0 SGJ 93 76 95 76 / 30 20 0 0 GNV 93 74 94 74 / 50 0 10 0 OCF 93 74 94 75 / 50 0 10 0

JAX WATCHES/WARNINGS/ADVISORIES

FL...None. GA...None. MARINE...Small Craft Advisory from 2 PM this afternoon to 5 AM EDT Wednesday for AMZ450-452-454-470-472-474.