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 t-storms this evening with a few more storms over the northeast FL coastal waters. Isolated to Widely Scattered Afternoon & Evening Thunderstorms Wednesday through Monday.

- Dangerously Hot & Humid Conditions Late this Weekend. Heat Advisory Conditions Possible Sun & Mon, when Values Approach 110

- Minor to Moderate Flooding Along the Satilla River in Southeast GA

UPDATE

A good environment for strong wind gusts today with dry air at about 700 mb and fairly high MLCAPE values. Noted DCAPE value from our 18Z sounding was 880 J/kg. T-storm wind gusts and an outflow boundary commonly had 40-55 mph with a few observed in the 55-60 mph range in Duval county. There are some linger widely scattered showers and storms at 745 PM just south of where the main action was today and this is where the residual outflow boundary is located and also some fairly robust CAPE values are still available for storms. This activity will probably linger until 10 pm or so. However, with we can't rule our a shower or two past midnight given the unstable airmass and energy aloft rotating southeast through northeast FL.

NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/

Main Highlights Today and Tonight:

- Isolated Strong Storms During the Late Afternoon and Evening Along and south of I-10.

Prefrontal showers have begun to sprout amid the unstable airmass out ahead of the incoming cold front which is currently pushing southeastward through the Deep South and push into the local forecast area overnight. Quite a bit of buoyancy for convection to work with this afternoon owing to the pool of cold mid level air and resulting moderately steep lapse rates. The main deterring factor for convective coverage today will be the wake subsidence behind the departing mid level shortwave, displacing the better dynamics toward the Mid Atlantic. That said, the buoyancy and a weak prefrontal/moisture boundary should be sufficient for showers grow in coverage with a 40-50% thunderstorm chance this afternoon. The most likely area where strong storms may develop will generally favor locations along and south of I-10 during the mid to late afternoon and early evening hours, around 4-8 PM. The main concern with stronger storms will be the possibility of substantial outflow wind gusts to 50 mph.

Showers and isolated storms may linger along the prefrontal boundary through midnight, mainly for north-central FL areas. Much drier west- northwesterly flow will other will eliminate rain chances through the early hours Wednesday. The surface cool front will stall around the FL/GA border, bringing cooler conditions into inland SE GA tonight, reading in the upper 60s. South of the front, mild and muggy conditions will persist across NE FL with lows in the low to mid 70s.

SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/

Main Highlights This Period:

- Only Isolated Thunderstorms on Wednesday Afternoon and Evening Across North Central FL.

- Widely Scattered Afternoon and Evening Thunderstorms on Thursday.

Shortwave troughing will shift south of our area on Wednesday morning, with an unseasonably dry air mass filtering into our region from north to south as the day progresses. PWATs will fall below inch for locations from Interstate 10 northward, with values falling to around 1.5 inches across north central FL by the afternoon hours. Only isolated showers and possibly a brief thunderstorm are expected for portions of north central FL, where mesoscale boundary collisions and the presence of a weakening surface front may have just enough moisture to work with to develop some brief, weak convection around the Ocala National Forest and inland portions of Flagler County. Plenty of sunshine and a much drier air mass will allow highs to again reach the low and mid 90s at most inland locations. The drier air mass filtering into our region will allow dewpoints to fall to the low and mid 60s at most inland locations on Wednesday afternoon, which will keep heat index values in check and close to actual air temperatures. Otherwise, weak high pressure building over the southern Appalachians in the wake of the dissipating frontal boundary will loosen our local pressure gradient, allowing for the Atlantic sea breeze to return by the early to mid afternoon hours at coastal locations, which should keep highs at area beaches in the upper 80s to around 90.

Any convection that manages to develop over or near the Ocala National Forest on Wednesday afternoon should dissipate shortly after sunset, with fair skies and diminishing winds allowing for low temperatures at inland locations north of I-10 to fall to the mid and upper 60s, with lower 70s elsewhere inland and low to mid 70s at coastal locations.

Stout ridging aloft over Mexico and west Texas will direct a potent shortwave trough southeastward from the Ozarks on Wednesday morning towards the FL panhandle by Wednesday night and Thursday morning. Although this feature will likely shear out over the northeast Gulf by Thursday afternoon, low and mid level flow will back slightly across our area as the day progresses, with west-southwesterly flow gradually increasing PWATs back above 1.5 inches by late afternoon. Just enough moisture and instability will be in place for widely scattered afternoon and evening convection to develop across our area, triggered by mesoscale boundaries such as the Gulf and Atlantic sea breezes. Highs on Thursday will tick up by a degree or two at inland locations, where mid to upper 90s are forecast. An early developing Atlantic sea breeze boundary should keep coastal highs in the upper 80s to lower 90s, and slowly increasing humidity values may bring Heat Index values up to the 100-105 degree range. Convection should be directed eastward as the afternoon and evening progress, with some lingering early evening activity for coastal northeast FL as well as for portions of inland southeast GA, with dry conditions then prevailing by midnight, with thinning debris cloud cover forecast after midnight. Lows will nudge up to the low to mid 70s inland and the mid to upper 70s at coastal locations.

LONG TERM /FRIDAY THROUGH TUESDAY/

Main Highlights This Period:

- Seasonably Hot and Humid Weather Friday and Saturday.

- Heat Index Values May Approach Heat Advisory Criteria on Sunday and Monday Afternoons.

- Widely Scattered Afternoon and Evening Thunderstorms from Friday through Sunday, Mainly Along the I-95 Corridor

- Increasing Coverage of Afternoon and Evening Thunderstorms Early Next Week

Ridges aloft centered east of the Bahamas and over west Texas on Thursday will consolidate over the Deep South during the weekend. Meanwhile, the axis of Atlantic surface ridging will extend its axis across the FL peninsula on Friday and Saturday, promoting a west- southwesterly low level wind regime. This weather pattern should allow for the Gulf coast sea breeze to become convectively active as it crosses the I-75 corridor during the early to mid afternoon hours, with intensity of thunderstorms potentially increasing along the I-95 corridor as this boundary collides with a pinned Atlantic sea breeze boundary later in the afternoon and towards sunset on both days. Coverage overall should be isolated to widely scattered, with the bigger story being rising temperatures, as highs soar to the mid and upper 90s all the way to area beaches. Heat index values should peak in the 103-107 degree range, or just below Heat Advisory criteria. Lows will remain in the 70s area-wide, although a few coastal locations may remain around 80.

Ridging aloft will retrograde northwestward by Sunday and Monday, resulting in low level flow veering to northwest to northerly on Sunday and then north to northeasterly by Monday. Although forecast confidence decreases, a seasonably moist and unstable environment should allow for an uptick in mostly diurnally driven convective activity triggered by mesoscale boundary collisions, especially early next week. Highs will continue to skyrocket to the mid and upper 90s inland, with sea breezes perhaps keeping coastal highs in the lower 90s. Increasing humidity values may bring Heat Index values up to the 105-110 degree range by Sunday and Monday, possibly prompting Heat Advisories for at least portions of our area.

AVIATION /00Z WEDNESDAY THROUGH 00Z THURSDAY/

Scattered showers and a few storms continue south of a line from SGJ to GNV and will continue to push southeastward this evening. Some lingering showers and a couple of storms nearby for the TAFs sites this evening except not at SSI where there is some drier air. After about 02z/03z, should see very little activity. Winds will ease tonight from the west. VFR conditions will persist overnight but a period of MVFR ceilings are possible for areas south of line from KGNV to KSGJ Wednesday morning, and have put in usual periods of BR for VQQ for tonight. Does not look as active for Wednesday so only have VCTS for SGJ and GNV.

MARINE

Scattered strong thunderstorms expected this evening over the northeast Florida waters. A weak cold front will come into the waters and stall through Wednesday which lead to a break in the offshore flow pattern through Thursday before weak offshore winds return this weekend. The Atlantic sea breeze development is likely to develop each day through the weekend along with southerly wind increases to Exercise Caution levels each evening beginning Friday.

Rip Currents:

Rip current risk is expected to remain on the low end side of Moderate through the end of the week and through the weekend as the Atlantic sea breeze becomes established each afternoon.

FIRE WEATHER

- High Daytime Dispersion Values Through Early This Evening - Areas Of High Daytime Dispersion Inland On Friday And Saturday

Breezy westerly surface and transport winds will continue through the evening hours tonight, with high daytime dispersion values expected through around sunset across much of our area. Scattered showers and thunderstorms will be possible through early this evening, mainly for locations along and south of Interstate 10.

An unseasonably dry air mass will then filter into our area on Wednesday, with only isolated afternoon and early evening showers and thunderstorms possible for areas in and around the Ocala National Forest. Minimum relative humidity values will fall to around 35 percent at inland locations on Wednesday afternoon. Breezy west-northwesterly transport winds will yield good daytime dispersion values for inland locations south of I-10, and an afternoon sea breeze will shift surface winds to easterly along the I-95 corridor. Light transport winds are forecast on Thursday, with afternoon sea breezes moving inland and possibly triggering widely scattered afternoon and early evening thunderstorms. Fair daytime dispersion values are forecast at most locations. Gradually strengthening southwest and westerly transport winds on Friday and Saturday should allow for at least marginally high daytime dispersion values at inland locations on Friday and Saturday afternoons.

FOG POTENTIAL AND OTHER REMARKS: Patchy fog will be possible for inland portions of north central FL early on Thursday morning.

HYDROLOGY

Minor to locally moderate flooding on the Satilla River Basin will continue to move downstream and impact the forecast points at Waycross and Atkinson this week.

PRELIMINARY POINT TEMPS/POPS

AMG 69 90 70 93 / 0 0 0 30 SSI 75 89 78 89 / 10 0 0 20 JAX 74 94 74 94 / 20 0 0 40 SGJ 76 92 75 92 / 40 10 0 30 GNV 75 95 72 96 / 30 0 0 30 OCF 77 95 73 95 / 20 10 0 30

JAX WATCHES/WARNINGS/ADVISORIES

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