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

- Areas of Locally Dense Fog Possible Early on Sunday Morning

- Cold Weather Advisory for Sunday Night & Monday Morning. Cold Weather Advisory [Wind Chills: 15-25F] Set for Southeast GA, Suwannee Valley & Portions of Inland Northeast FL

- Freeze Advisory for SE GA and Inland NE FL Sun Night & Mon. Hard Freeze Potential SE GA Early on Monday & Tuesday Mornings. Light Freezes for the Suwannee Valley & Portions of Inland Northeast FL

- Gale Warning Set for Sunday Night & Monday Morning

UPDATE

Some increase in high clouds tonight, but overall forecast remains on track with temps not as cold as previous nights with lows in the 45-50F range inland and 50-55F along the Atlantic Coast. Near calm winds at the surface will help to support locally dense fog formation across most of NE FL to the south of the I-10 corridor, while a slight increase in winds across SE GA towards morning ahead of approaching frontal boundary should prevent significant fog formation there. Latest model blend guidance suggesting about 20-40% chances of dense fog formation across portions of NE FL late tonight, but not confident in enough coverage to support dense fog advisories at this time.

NEAR TERM /UNTIL 6 AM SUNDAY MORNING/

The beautiful, warm, sunny day continues under the influence of high pressure this afternoon with highs pushing into the 70s areawide.

Though weather conditions today are excellent, a large upper trough will begin its dive toward the southeast tonight. This will be a significant system as the airmass will be a true arctic airmass with a deep northwesterly flow with extending through Canada and into the southeastern US. The surface attendant surface front and arctic high aren't expected to blast through the area until Sunday night, so preparations to protect sensitive plants, livestock, and people should begin today.

As far as tonight, another cool but near normal December night is expected. The increasing southwesterly flow tonight should push lower-level Gulf moisture inland resulting in an increased fog potential for the Suwannee Valley, interior area of SE GA, and north- central FL where locally dense fog may develop by daybreak.

SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY NIGHT/

Cold front will move southeast of the area Sunday morning, with a weak secondary front moving through in the afternoon, as strong high pressure builds to the northwest. A few showers will be possible with the frontal passage, mainly for inland SE GA, where better moisture will be. Temperatures will likely not fall a diurnal curve on Sunday, with readings peaking earlier in the afternoon, with readings then falling. Skies will slowly clear from northwest to southeast through day. Due to the gradient between the exiting frontal system and building high, winds will become elevated and gusty during the afternoon.

On Sunday night the high will build more toward the north. This pattern will yield a cold north northeast flow across the area. The exception will be for coastal NE FL, where the northeast flow will bringer milder air from the Atlantic. Skies will be clear, except for a few clouds in the onshore flow along NE FL coast. The pressure gradient will still be pretty significant Sunday night, keeping winds elevated and gusty through the night. Temperatures Sunday night will have a wide range, with lows over inland SE GA in the lower to mid 20s, and lower to mid 40s NE FL coast. With winds still elevated, Cold Weather Advisory headlines will be needed to highlight expected cold due to winds chills and impacts on people, while freeze warnings will be needed to highlight impact on plants. Too much wind for frost development Sunday night.

On Monday, the high will build closer to the area. Weak troughing along the coastal waters will result in scattered cloud cover over eastern counties, with more sunshine further inland. The cold airmass will remain in place, with highs well below seasonal averages.

For Monday night, the high will settle over southern GA, with weak troughing remaining over the coastal waters. Once again, a wide range in temperatures are expected due to the onshore flow. Lows in the middle 20s will be common over inland SE GA, to the middle 40s NE FL coast. In addition to the freezing temperatures, light winds will yield a greater Frost potential.

LONG TERM /TUESDAY THROUGH SATURDAY/

High pressure ridge will become centered more toward the northeast Tuesday, then east Wednesday and Thursday. The high will away late week, as a cold front moves through. High pressure will build to the northeast following passage on Saturday.

Other than the chance for a few showers inland SE GA ahead of the front Thursday night, this is expected to be a dry period.

Above normal temperatures are forecast this period.

AVIATION /00Z SUNDAY THROUGH 00Z MONDAY/

VFR conds with near calm and/or light and variable winds this evening, otherwise boundary layer cooling and increased low level moisture will lead to high chances of LIFR/IFR conds expected at VQQ/GNV in the 06-14Z time frame, while CRG/JAX/SGJ will remain on the edge of this fog/stratus development and have just trended close to MVFR conds in the 08-12Z time frame with SSI likely remaining fog free tonight. Arctic cold frontal passage expected in the 17-19Z time frame with increased NW winds to 15G25 knots along with lower VFR cloud decks around 4Kft, with some lower potential for MVFR CIGS but have just kept as SCT025 in the terminal forecasts for now. Clearing skies and winds shifting to the N-NW right at the end of the current 00Z TAF period and have showed this clearing at the 22- 23Z time frame at the terminals.

MARINE

Fair maritime conditions continue through Sunday afternoon before a strong, arctic cold front pushes through the waters Sunday, bringing gales and moderately high seas, especially offshore, during the overnight hours Sunday into Monday.

North-northwesterly winds nearing gale force developing through the overnight hours Sunday into Monday with frequent gusts up to 40 knots. For this a Gale Watch has been issued across all the waters Sunday afternoon through Monday morning. Winds should decrease to Small Craft Advisory levels late Monday morning and continue to as high pressure slides in from the north. Seas will lower Monday night with the diminishing winds with generally fair maritime conditions through Thursday as a weaker front approaches from the northwest.

Rip Currents: SE GA Moderate Sunday NE FL Moderate Sunday

FIRE WEATHER

PATCHY HIGH DISPERSIONS SUNDAY... CRITICALLY LOW RH LEVELS INLAND SE GA MONDAY... PATCHY LOW DISPERSIONS TUESDAY AND WEDNESDAY...

A cold front will move southeast across the area Tonight into Sunday morning. Strong high pressure will build behind this boundary. Elevated and gusty winds expected from Sunday afternoon through Sunday night. High pressure will be the prevailing weather feature then through Thursday night. A cold front will move southeast across the area Friday, followed by high pressure ridging Saturday.

FOG POTENTIAL AND OTHER REMARKS: Patchy to areas of fog Tonight, with greatest coverage south of Gainesville. Widespread Frost SE GA, and inland NE FL Monday night. Areas of frost inland SE GA Tuesday night.

PRELIMINARY POINT TEMPS/POPS

AMG 47 63 24 44 / 10 10 0 0 SSI 53 67 32 47 / 0 10 0 0 JAX 49 72 33 50 / 0 10 0 0 SGJ 53 74 43 57 / 0 10 0 10 GNV 50 75 35 55 / 0 10 0 0 OCF 51 76 39 57 / 10 10 10 0

JAX WATCHES/WARNINGS/ADVISORIES

FL...Cold Weather Advisory from 1 AM to 10 AM EST Monday for FLZ021- 023-024-030-031-035-120-124-125-132-136-220-225-232-236- 322-325-422-425-522. Freeze Watch from late Sunday night through Monday morning for FLZ021-023-024-030-031-035-120-124-136-220-225-232-236- 322-422-425-522. GA...Cold Weather Advisory from 1 AM to 10 AM EST Monday for GAZ132>136-149-151>154-162-163-165-166-250-264-350-364. Freeze Watch from late Sunday night through Monday morning for GAZ132>136-149-151>154-162-163-165-166-250-264-350-364. MARINE...Gale Watch from Sunday afternoon through Monday morning for AMZ450-452-454-470-472-474.