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

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

- Hard Freeze Potential for Inland Southeast GA Early Next Week. Hard Freeze Potential Early on Monday & Tuesday Mornings. Light Freezes for the Suwannee Valley & Portions of Inland Northeast FL

- Gale Warnings Possible on Sunday Night & Monday Morning

NEAR TERM /UNTIL 6 AM THIS MORNING/

The area will remain mainly under the influence of the western periphery of an Atlantic ridge throughout the day today and into the first part of tonight, keeping the benign and dry pattern persistent through most of the near term period. More mid and high clouds will start to stream across the area today as southwesterly flow aloft off the Gulf increases, especially over northeast Florida. But otherwise a dry and mild day is expected featuring light southwesterly winds only around 5 mph, and high temps in the upper 60s to mid 70s. A slightly milder night will be in store tonight as well thanks to more cloud cover and southwesterly flow, though still in the 40s across much of southeast GA and the Upper Suwannee Valey wilth low to mid 50s elsewhere. Early Morning fog chances Sunday Morning will be a little bit higher with an uptick in surface moisture throughout today and into tonight. Primary focus area would be over inland northeast FL, though some patchy fog is likely over interior southeast GA as well given a frontal boundary starting to approach Sunday Morning.

SHORT TERM /6 AM THIS MORNING THROUGH SUNDAY NIGHT/

Troughing aloft digging southeastward from the eastern Great Lakes and Ohio Valley on Sunday morning will pivot eastward across New England on Sunday night. This potent trough will drive an Arctic cold front across southeast GA on Sunday morning and the rest of our area during the early to mid afternoon hours. A narrow ribbon of moisture will pool just ahead of the approaching Arctic cold front late on Saturday night across the Deep South, where PWATs will climb to around 1.25 inches after midnight on Saturday night and early Sunday morning. Strong forcing just ahead of the Arctic cold front and these slightly higher moisture levels will likely allow for a few showers to develop over the Altamaha / Ocmulgee River basins early on Sunday morning, with a few showers possible across the rest of inland southeast GA through around noon. Although an isolated shower cannot be ruled out elsewhere during the frontal passage, dry weather is likely to prevail on Sunday across northeast and north central FL. The frontal passage will likely be accompanied by a band of mid-level cloudiness that will progress southward during the afternoon hours. A cooler and drier air mass will begin to advect into our region on Sunday afternoon, with dewpoints falling below freezing for locations from Waycross northward in southeast GA during the late afternoon hours. Breezy northwesterly winds will overspread our region on Sunday afternoon, and cold air advection will counter increasing sunshine across southeast GA, keeping early afternoon highs in the 60s, with temperatures falling through the 50s during the mid to late afternoon. Highs will climb into the 70s early in the afternoon across northeast and north central FL, with temperatures then falling back through the 60s during the late afternoon.

The base of deep troughing over the eastern third of the nation will pivot across our region on Sunday night, with dry northwesterly flow then prevailing locally through Monday night. An Arctic dome of high pressure (around 1045 millibars) will build over the northern Plains on Saturday night, with this surface ridge only slowly weakening as it slides southeastward on Sunday and Sunday night, reaching the Ohio and Tennessee Valleys by early Monday morning. Our local pressure gradient will continue to tighten as this surface ridge wedges down the southeastern seaboard, likely creating Gale Conditions over our local Atlantic waters by the early evening hours. Low level flow will quickly veer to northerly towards sunset and then northeasterly by sunrise on Monday. Strong cold air advection will drive an extremely dry air mass into southeast GA and inland portions of northeast and north central FL, with dewpoints falling into the single digits across inland southeast GA after midnight, with teens extending into the Suwannee Valley and coastal southeast GA and 20s for inland northeast and north central FL. A hard advective freeze is likely across inland southeast GA, where lows will fall to the low and mid 20s, with a light northeasterly breeze dropping wind chill values to mid teens. A light advective freeze will extend to coastal portions of southeast GA, the Suwannee Valley and inland northeast FL, and possibly for portions of coastal northeast FL, where breezy northeasterly winds will drive wind chills down to the upper teens and lower 20s. Cold Weather Advisories and Freeze Watches will likely be issued later today in advance of this Arctic plunge for these locations. Breezy onshore winds will likely keep lows in the 30s to around 40 for inland north central FL and the lower 40s for coastal St. Johns and Flagler Counties, where gusty northeasterly winds will drive wind chill values down to the low and mid 30s by sunrise on Monday.

Arctic high pressure will continue to steadily weaken as it builds over the southeastern states on Monday, allowing the local pressure gradient to loosen over southeast GA during the afternoon hours. Despite plenty of sunshine, the Arctic air mass will keep highs in the 40s for locations north of Interstate 10. A tighter local pressure gradient will continue for locations south of I-10, keeping breezy northeasterly winds in place, where highs will generally remain in the low to mid 50s, except upper 50s to around 60 for inland north central FL.

Coastal troughing will begin to take shape over our near shore waters adjacent to northeast FL on Monday afternoon, likely driving a deck of marine stratocumulus onshore along the I-95 corridor on Monday evening. Lows on Monday night will likely remain above freezing for locations east of I-95, with low to mid 40s forecast along the northeast FL coast, where a light northerly breeze will prevail overnight. Fair skies and decoupling winds elsewhere will allow for radiational cooling, with another hard freeze likely across inland southeast GA, with a light freeze expected for the Suwannee Valley. Light winds will allow for widespread frost formation, with frosty conditions likely extending into inland portions of north central FL, where lows will fall to the mid and upper 30s.

LONG TERM /MONDAY THROUGH FRIDAY/

Troughing aloft will exit the U.S. eastern seaboard on Tuesday, with dry northwesterly flow prevailing locally through Tuesday night. Our local pressure gradient will continue to loosen on Tuesday as coastal troughing persists over our local Atlantic waters. Cold air advection will shut off as high pressure weakens along the southeastern seaboard, allowing highs to rebound to the upper 50s across southeast GA to the 60s across northeast and north central FL. One more night of radiational cooling is expected on Tuesday night, but model blends keep lows above freezing across our area. Widespread frost formation is still likely for inland southeast GA, where lows will fall to the low and mid 30s. Lows elsewhere will likely remain in the upper 30s and 40s inland, ranging to around 50 along the northeast FL coast, where marine stratocumulus may continue to move onshore along the I-95 corridor.

Temperatures will continue to modify on Wednesday as zonal flow aloft develops and surface ridging shifts offshore of the southeastern seaboard. Onshore low level flow on Wednesday will continue to advect marine stratocumulus onshore from the Atlantic waters across our region, but rising heights aloft will allow highs to climb into the 70s for inland locations south of I-10, while mid to upper 60s prevail elsewhere. Lows on Wednesday and Thursday nights will only fall to the mid and upper 40s for inland southeast GA and northern portions of the Suwannee Valley, with 50s elsewhere.

Southwesterly flow aloft will develop on Thursday and Friday downstream of a trough that will be pivoting across the Great Lakes, Ohio and Tennessee Valleys. Low and mid level flow will continue to veer, with southerly winds on Thursday morning shifting to south- southwesterly during the afternoon, boosting highs into the 70s, except upper 60s for coastal southeast GA due to the afternoon sea breeze. This front and gradually increasing moisture levels could bring a few showers to inland portions of southeast GA and western portions of the Suwannee Valley by Thursday afternoon and night. Support aloft for the front will wane by Friday, with this boundary potentially stalling across the Interstate 10 corridor. A slightly cooler air mass may filter into southeast GA as winds shift to northwesterly during the morning hours and then quickly veer to northeasterly by the afternoon. Highs will likely remain in the 70s across inland portions of northeast and north central FL.

AVIATION /06Z SATURDAY THROUGH 06Z SUNDAY/

VFR is expected to prevail for the majority of the rest of the morning hours. Have opted to keep TEMPO groups for possible shallow FG/BR over inland airfields, though general trend has been downward with this potential from hi-res model guidance. Any FG/BR will dissipate by late morning, with VFR and light winds expected to prevail throughout the afternoon and evening. BR/FG appears more likely Sunday Morning ahead of an approaching front, though any impacts to area terminals are expected to be after the current forecast period.

MARINE

High pressure ridge hold over area waters through this evening before breaking down tonight ahead of an approaching cold front. The front will cross through the area on Sunday, bringing only very isolated shower chances Sunday. Northwesterly winds will strengthen in the wake of this frontal passage on Sunday and Sunday Night afternoon: Small Craft Advisories are very likely, with Gale Warnings also possible Sunday Night as winds shift to northerly and then northeasterly due to strong high pressure wedging down the southeastern seaboard. High pressure will then gradually weaken over the southeastern states early next week as coastal troughing develops over our local waters. Small Craft Advisories and/or Gale Warnings will likely continue through Monday morning, with onshore winds and seas then gradually subsiding from Monday afternoon through Tuesday. Coastal troughing may generate a few showers early next week, mainly for the offshore waters. High pressure will then shift eastward and off the southeastern seaboard by midweek.

Rip Currents: SE GA Low Sunday NE FL Low Sunday

..PATCHES OF HIGH DISPERSION VALUES ON SUNDAY AFTERNOON

...ELEVATED DISPERSION VALUES ON SUNDAY NIGHT FOR LOCATIONS ALONG AND EAST OF I-95...

Light and variable surface winds this morning for locations south of Waycross will shift to southwesterly this afternoon, with transport speeds increasing to 5-10 mph. Westerly transport winds of 5-10 mph this morning for locations north of Waycross will shift to southwesterly this afternoon, where fair daytime dispersion values are forecast. Light speeds elsewhere will yield poor dispersion values, with pockets of marginally low values at coastal locations and also for the Suwannee Valley and Okefenokee Swamp. Surface and transport winds will shift to west-northwesterly by sunrise on Sunday, with breezy conditions developing across inland southeast Georgia during the morning hours, where a few showers will be possible. Winds will then shift to northwesterly during the afternoon hours, with steadily increasing speeds area-wide creating good daytime dispersion values, with marginally high values possible in the Ocala National Forest as well as inland southeast Georgia.

Surface and transport winds will shift to northeasterly after midnight on Sunday night, with strong speeds persisting along the Interstate 95 corridor, where elevated nighttime dispersion values are forecast. A cold and very dry air mass will then settle over our region on Monday, with critically low humidity values expected on Monday afternoon across most of inland southeast Georgia. Breezy northeasterly surface and transport winds on Monday morning will shift to east-northeasterly with diminishing speeds across inland southeast Georgia and northern portions of the Suwannee Valley, precluding Red Flag Conditions. Breezy speeds will continue elsewhere, resulting in fair daytime dispersion values, except for good values at coastal locations and for north central Florida.

FOG POTENTIAL AND OTHER REMARKS: Patchy fog is possible early this morning for portions of the Suwannee Valley and inland southeast Georgia. Areas of locally dense fog will be possible during the predawn and early morning hours on on Sunday across much of our area. Cold Weather Advisories and Freeze Watches will likely be issued later today in advance of a significant cold spell that will arrive on Sunday night, with wind chill values falling to the 15-25 degree range by sunrise on Monday for southeast Georgia, the Suwannee Valley, and portions of inland northeast Florida. A hard freeze is likely during the early morning hours on Tuesday for inland southeast Georgia, with a light freeze likely for the Suwannee Valley and portions of coastal southeast Georgia and inland northeast Florida.

PRELIMINARY POINT TEMPS/POPS

AMG 70 48 63 23 / 0 10 20 0 SSI 68 52 68 31 / 0 0 10 0 JAX 74 49 73 32 / 0 0 0 0 SGJ 73 54 75 43 / 0 0 0 0 GNV 76 51 75 34 / 0 0 0 0 OCF 75 53 75 39 / 0 0 0 0

JAX WATCHES/WARNINGS/ADVISORIES

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