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

- Dangerously HOT Weather Continues through Thursday. Heat Advisories through 8 PM Today for Locations South & East of Waycross. Heat Advisories Likely Again on Thursday & Possible on Friday.

- Scattered to Numerous Afternoon & Evening Thunderstorms Each Day. Main Impact Areas through Thursday: Along & South of FL/GA Border. Afternoon & Evening TStorm Coverage Increases Friday through Sunday. Strong to Isolated Severe Storms are Possible Each Afternoon & Evening. Primary Hazards: Wind Gusts of 40-60 mph, Frequent Lightning Strikes, and Torrential, Slow Moving Downpours that Could Create Localized Flooding.

NEAR TERM /TODAY THROUGH TONIGHT/

Highlights through Tonight:

- Near Record High Temperatures with Dangerous Heat Indices for Portions of Our Area. Heat Advisories from 11 AM through 8 PM today for Locations South and East of Waycross, GA. - Strong to Isolated Severe Thunderstorms Possible this Afternoon and Evening Across Northeast and North Central FL. Wet Microburst Potential within Stronger Storms, Possibly Creating Wind Gusts of 40- 60 mph, along with Frequent Lightning Strikes and Localized Flooding.

Mostly sunny skies for most of the morning have allowed temperatures to rise into the 90s so far, expected to reach near 100 degrees for portions of southeast Georgia today. A Heat Advisory remains in effect for most of the area through 8pm for hazardous heat index values, with the same area under another advisory tomorrow.

Plenty of instability and moisture is present across northeast Florida this afternoon, posing a threat to some isolated strong to severe thunderstorms, mainly from boundary collisions through this evening. Primary concern will be damaging winds up to 60 mph, although heavy downpours may cause localized flooding problems, especially near locations that received decent rain yesterday, we also can't rule out some small hail again. This morning, the Storm Prediction Center placed northeast Florida and the southern portions of southeast Georgia in a 'Marginal' risk of severe winds for today. Overall, storms will begin to dissipate after sunset, but we may see some lingering showers and isolated storms through the late evening. With the drier air in place over southeast Georgia closer to the front, precipitation is unlikely north of Waycross today.

SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/

Main Highlights This Period (Thursday - Friday):

- Potential for isolated strong to severe thunderstorms each afternoon

- Heat Advisories will be issued for Thursday, and may be needed again on Friday though may be more limited in area

A weak frontal boundary will remain nearly stationary from low pressure over the Carolinas to central parts of GA and AL. Our area will remain in weak west or southwest low level flow each day with hints of weak troughing in the flow over the region. An upper trough will be in place over the area this period.

The combination of weak low level flow and diurnal heating will allow sea breezes to push inland each day. Diurnal heating and sea breeze convergence will yield scattered to numerous showers and storms each afternoon and evening for this period. Best chances of showers and storms will be over northeast FL on Thursday where the best low level moisture will be. For Friday, there may be more uniform coverage as moisture starts to expand in areal extent so generally expected afternoon and evening scattered to numerous showers and storms for the entire area. Guidance also suggests isolated convection may be around well after midnight each night which seems reasonable given the lingering instability at nighttime.

Model guidance shows the potential for cooler temperatures in the mid levels which will enhance instability for the region. In addition to more coverage of storms, this may lead to somewhat better chances of isolated severe, pulse-type storms with strong/damaging downburst winds. At this time, SPC has placed part of our area in a marginal risk of severe storms for Thursday.

Temperatures will remain above average this period. In fact, record highs may be set on Thursday and possibly on Friday. Heat advisories will be going into effect Thursday and may be needed again on Friday. But on Friday, more precip is likely and the extent of heat advisory criteria looks more limited.

LONG TERM /SATURDAY THROUGH WEDNESDAY/

Main Highlights This Period (Saturday through Tuesday):

- Isolated strong to severe thunderstorm chances each afternoon and evening

The pattern from Thursday and Friday lingers into Saturday with general low level troughing from the Carolinas southwest into central GA and AL. With more than enough moisture around the area, likely to see afternoon and evening scattered to numerous showers and storms for Saturday.

We start to see the upper trough over the area dig southward on Sunday which will shove the low level trough and moisture further south and east. This should place the higher chances of rain over northeast FL area (generally scattered coverage) with more isolated convection for southeast GA.

From Monday to Tuesday, there is not much appreciable change except for the PWATs just near average. We see weak low level troughing extending southwest to northeast over the southeast states and weak sfc ridging over the FL peninsula. Unfortunately, moisture does not appear to be high and may in fact be a little below normal. Given this, coverage of convection looks isolated to scattered at this time.

Temperatures will trend from near average to a little above average this period.

AVIATION /18Z WEDNESDAY THROUGH 18Z THURSDAY/

Showers and thunderstorms will begin developing near the northeast FL terminals towards 19-21Z, with dry weather and VFR conditions expected to prevail at SSI throughout the forecast period. PROB30 groups were maintained from around 20Z through around 01Z at some of the northeast FL terminals, with higher confidence for IFR visibilities during heavier downpours at GNV and VQQ where TEMPOs are in place. Brief surface wind gusts around 30 knots are expected during convection at the northeast FL terminals this afternoon and evening. Convection near the northeast FL terminals should dissipate by 03Z Thursday, with VFR conditions expected to prevail thereafter other than typical morning visibility restrictions at VQQ.

MARINE

Weak high pressure situated over the northern Gulf will maintain a northwest to westerly wind flow across our local waters today. The Atlantic sea breeze will push slowly inland this afternoon, shifting surface winds to southeasterly this afternoon and then southerly this evening, with speeds briefly surging around sunset before diminishing overnight. Meanwhile, a stalled frontal boundary positioned just north of the Georgia waters will remain in place during the next several days. Scattered showers and thunderstorms may impact the near shore waters adjacent to northeast Florida this afternoon and evening and again on Thursday afternoon and evening. Coverage of mainly afternoon and evening showers and thunderstorms will then increase from Friday through the upcoming weekend throughout our local waters as southwesterly winds prevail, with afternoon sea breezes developing each day.

Rip Currents: Offshore winds and low surf heights will prevail during the morning hours at area beaches during the next several days. However, the afternoon sea breeze will coincide with the outgoing tide during the next few afternoons, with breezy onshore winds likely creating a lower end moderate risk at all area beaches through Friday. Low surf heights and later outgoing tide times this weekend could lower the risk at area beaches.

..PATCH HIGH DISPERSION THIS AFTERNOON

...HEAT ADVISORIES IN EFFECT FOR PARTS OF THE AREA REST OF TODAY AND THURSDAY...

A frontal zone will remain stalled over south and central Georgia through Friday. Generally scattered showers and thunderstorms are expected, mainly in the afternoon and evening hours through Friday. Hot weather is likely to continue into Friday with above average temperatures mainly in the mid to upper 90s each day - around 100 over inland southeast GA. Min RH over inland southeast GA today and Thursday may dip into the lower to middle 30s, however, winds will remain light each day. Patchy high daytime dispersion expected this afternoon over most of southeast GA south to near the I-10 corridor. Generally lower daytime dispersion expected Thursday and Friday.

Fog Potential: Significant fog formation is not expected. Gusty and erratic winds are expected in and near thunderstorms.

CLIMATE

Near record high temperatures are possible at some of our designated climate sites during the next few days:

Today, August 19th: KJAX: 99/1900 KGNV: 100/1954 KAMG: 103/1995 KCRG: 97/2010

Thursday, August 20th: KJAX: 101/1900 KGNV: 99/1900 KAMG: 104/1995 KCRG: 98/2016

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

PRELIMINARY POINT TEMPS/POPS

AMG 74 100 75 96 / 0 10 10 70 SSI 79 95 79 93 / 10 10 0 40 JAX 75 97 75 94 / 20 30 20 60 SGJ 77 95 76 93 / 30 30 20 50 GNV 75 95 74 93 / 30 50 20 60 OCF 76 95 75 93 / 20 60 20 60

JAX WATCHES/WARNINGS/ADVISORIES

FL...Heat Advisory until 8 PM EDT this evening for FLZ021-023-024- 030-031-035-038-120-124-125-132-136>138-140-220-225-232- 233-236-237-240-322-325-333-340-422-425-433-522-533-633. Heat Advisory from 11 AM to 7 PM EDT Thursday for FLZ021-023- 024-030-031-035-038-120-124-125-132-136>138-140-220-225- 232-233-236-237-240-322-325-333-340-422-425-433-522-533- 633. GA...Heat Advisory until 8 PM EDT this evening for GAZ153-154-162- 163-165-166-264-350-364. Heat Advisory from 11 AM to 7 PM EDT Thursday for GAZ153-154- 162-163-165-166-264-350-364. MARINE...None.