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 Afternoon & Evening Thunderstorms Today

- Dangerously Hot & Humid Conditions Late this Weekend. Heat Advisory Conditions Possible Sun & Mon, Peak Heat Index: 108 -110 F

- Minor Flooding Along the Satilla River in Southeast GA

NEAR TERM /THROUGH TONIGHT/

Main Highlights through Tonight:

- Scattered Strong/Isolated Severe Storms this afternoon and evening, mainly for Northeast Florida, between the I-95 and US-301 corridors

The afternoon sea breeze has taken a bit of time to get going today. However, all available short-term numerical weather guidance supports our meteorological reasoning that is just a matter of a couple of hours before this convection forms along the sea breeze as it presses inland. A few strong to isolated severe storms with gusty winds 40 to 50 mph and locally heavy rainfall will be the primary threats, in addition to possible frequent cloud to surface lightning strikes. The timing for convection initiation in northeastern Florida will be around 2-3 pm, and a bit delayed for southeastern Georgia.

Slow moving convection along the I-95 corridor this evening around sunset will drift into the Atlantic coastal waters or push NE across the Altamaha River Basin by the midnight time frame. Fair skies and generally quiet weather during the overnight hours with the usual muggy overnight lows in the 70s inland and near 80F along the Atlantic beaches. Some convergence in SW flow along the NE Gulf may trigger some isolated storms along the NE Gulf Coast that may drift into Gilchrist county towards sunrise Friday morning.

SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/

Main Highlights This Period:

- Scattered to Numerous Thunderstorms Friday and Saturday.

- Seasonably Hot and Humid Weather Friday and Saturday.

A strong, broad upper-level ridge will stretch across the southern half of the CONUS, extending eastward into the western North Atlantic. A Bermuda surface high will remain well planted in the central Atlantic through Saturday night. Coupled with seasonal moisture profiles, all in all, a "rinse and repeat" forecast for Friday through Saturday night, with rain and thunder chances limited to typical summertime sea breeze circulations in the afternoon and evening hours.

Highs on Friday and Saturday will rise to the mid 90s along and west of I-95 across our inland zones. Highs will be a bit lower in the climatological cooler areas west of US-441 over southeastern Georgia and along the coastlines each day, peaking in the low 90s. There will be little relief in the heat in the overnight periods, with lows only dropping into the mid to upper 70s Friday and Saturday mornings.

LONG TERM /SUNDAY THROUGH WEDNESDAY/

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

- Numerous showers and thunderstorms expected for Monday, possibly lingering into Tuesday.

- Decreasing rain chances expected for Wednesday and Thursday.

The strong upper-level anticyclone will remain parked over the lower Mississippi Valley on Sunday. Coupled with a surface high remaining anchored in the central North Atlantic, expect a continuation of summer-like conditions. Global ensemble mean fields suggest temperatures and dew points may even nudge up a couple of degrees, possibly supporting the need for Heat Advisories for portions of the CWA, particularly in the favored warmer inland locations. The only relief from the heat will be yet another possible round of sea breeze-driven afternoon showers and thunderstorms.

Global deterministic and ensemble guidance highlight a change in the synoptic pattern for the early part of next week. A positively tilted shortwave trough located off New England is expected to deepen, supporting surface cyclogenesis in the west-central Atlantic. This will drive a weak frontal boundary towards the Southeast Sunday night into Monday. Forecast soundings indicate a possible period of overlap among deep lower tropospheric moisture, minimal inhibition, and at least moderate shear in the area, which may support some stronger thunderstorms during the daytime hours on Monday. This will be monitored over the next several forecast cycles.

Despite the generally high confidence in the forecast through Monday, ensemble member solutions diverge substantially beyond regarding the evolution of the front. Most GEFS members, along with the deterministic GFS, quickly press the front south of the area, drying out southern Georgia and the Jacksonville area. On the contrary, other solutions, including many of the Canadian ensemble members, like to stall the front in the vicinity of the CWA for a period of time, before finally either dissolving or pushing the front further south. This would provide several more forecast periods with elevated rain and thunder chances. Outside of the heat risks, fine-tuning the forecast associated with the ultimate evolution of this frontal system will our main focus over the next couple of days--stay tuned.

AVIATION /18Z THURSDAY THROUGH 18Z FRIDAY/

Isolated to scattered convection will develop shortly, first along the I75 corridor including GNV then spreading east to the I95 corridor terminals by 20-22z. Outside of convection expect VFR conditions, however, in and around convection anticipate more erratic and gusty winds as well as reduced VIS/CIGs at least to MVFR ranges. Convection should decrease quickly at around sunset this evening again allowing for VFR conditions with light winds to develop overnight. That said, there is a lower VIS signal for KVQQ and KGNV later tonight, which will improve around sunrise Friday morning. (WFO LIX: Frye)

MARINE

Atlantic high pressure in the central North Atlantic will dictate the synoptic pattern for the southern Georgia and northern Florida Atlantic coastal waters through the weekend. The high will support prevailing westerly light to gentle breezes in the overnight and early morning periods, with easterlies owed to afternoon and evening sea breeze circulations. Rain and thunder chances will remain near- normal through the weekend. A weak frontal boundary will approach the marine zones on Monday, supporting increased coverage for showers and thunderstorms for the first part of early next week.

Rip Currents:

A low rip current risk is expected during the morning hours each day through the weekend for all southern Georgia and northern Florida Atlantic beaches. As a sea breeze circulation kicks up each afternoon, winds will clock around to the southeast, supporting a moderate risk for rip currents through the evening hours for all the area beaches.

FIRE WEATHER

- High Dispersion Indices Expected for Inland Locations Friday

A developing Atlantic sea breeze will nudge westward throughout the afternoon, with easterly surface winds 5-10 mph behind its passage. Scattered thunderstorms will develop as the Atlantic sea breeze shifts onshore, with more numerous thunderstorms along the St. Johns River Basin. Minimum relative humidity values will remain above 40% throughout the afternoon. Similar conditions are expected to continue throughout the weekend, although increased southwesterly transport winds coupled with deeper mixing heights will support somewhat higher daytime dispersion indices on Friday afternoon, approaching 75 for some island areas.

FOG POTENTIAL AND OTHER REMARKS: Significant fog is not expected the through the weekend. Any developing thunderstorm will be capable of producing gusty winds to 40-50 mph, frequent cloud to surface lightning strikes, and locally heavy downpours.

HYDROLOGY

Minor Flooding will continue along the Satilla River Basin into the upcoming weekend.

PRELIMINARY POINT TEMPS/POPS

AMG 92 72 92 73 / 40 30 30 20 SSI 90 79 91 78 / 10 10 50 20 JAX 96 75 95 75 / 50 20 50 10 SGJ 94 75 93 76 / 50 30 60 20 GNV 96 73 94 73 / 40 10 60 10 OCF 94 74 93 74 / 30 10 50 10

JAX WATCHES/WARNINGS/ADVISORIES

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