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

- Locally Dense Fog Possible Early Saturday Morning

- Strong to Isolated Severe Thunderstorms for SE GA Saturday

- Extreme Drought Prevails Across Most of the Region. Red Flag Conditions Possible Monday

- Moderate Rip Current Risk at Area Beaches Today

- Small Craft Advisory Conditions Sunday through Monday

- Freeze and Frost likely Monday night and Tuesday night

NEAR TERM /THROUGH TONIGHT/

Main Hazards this period: Locally dense fog this morning, mainly near I75. Potential for a few strong to severe thunderstorms late this afternoon through Tonight.

High pressure ridge over southern FL will move away to the southeast later Today, as a cold front approaches from the northwest. The cold front will move to near the GA/FL border by sunrise Sunday.

Fog and stratus which advects in from the Gulf early this morning will lift by mid morning. The most favorable location for dense fog this morning will be along and near the I75 corridor of NE FL.

Convection is expected to develop ahead of the front in a moist and unstable airmass across region mid afternoon, and spread southeast in the evening and through Tonight. The greatest chance for a few strong to severe storms will be over SE GA, which is closer to the center of the surface low, and under an upper wave.

Today will be another day with well above normal temperatures, with highs well into the 80s. Could see a few spots reach 90 over interior NE FL. Temperatures will remain above normal into Saturday night, as colder air behind front will largely advect in after this period.

SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/

MAIN WEATHER CONCERNS (Sunday - Monday Night: - Northwesterly Winds Strengthen on Sunday

- Sharply Colder Sunday Night with a Light Freeze Possible Across Inland Southeast GA & Wind Chills Falling to the 20s - Gusty Northwesterly Winds and Low Humidity Increase the Wildfire Danger on Monday

- Widespread Freeze & Dangerously Cold Wind Chills Monday Night

Deep troughing will dig southeastward from the Great Lakes through the Deep South during this period, driving a strong cold front across our region during the predawn and morning hours on Sunday. Model soundings indicate some surface-based CAPE increasing to the 250-500 j/kg range ahead of this front across north central FL during the early to mid-morning hours, indicating the potential for a few thunderstorms to accompany scattered to numerous showers along the I-95 corridor. This activity will sweep southeastward, with any leftover showers expected to move offshore by noon. A colder and much drier air mass will advect into our region as the front pushes offshore and low pressure develops near the Outer Banks, allowing skies to clear from northwest to southeast on Sunday afternoon. Strong and frequent northwesterly wind gusts of 30-40 mph will assist in temperatures falling through the 50s and 60s for most locations by the mid to late afternoon hours on Sunday.

Bombogenesis is forecast near the Delmarva peninsula on Sunday night, with arctic high pressure spilling southward from the Canadian prairies through the Plains states and into Deep South Texas. This weather pattern will keep a tight local pressure gradient in place across our region from Sunday afternoon through Monday night as rapidly deepening and slow moving low pressure parallels the Mid-Atlantic and New England coasts and Arctic high pressure pivots across the Ozarks, eastern Texas, and the lower Mississippi Valley. A light advective freeze is now likely for inland southeast GA, while lows elsewhere generally fall to the mid 30s towards sunrise on Monday. Wind speeds sustained at 10-15 mph, with frequent 20-30 mph gusts throughout the night will drive wind chill values down into the mid and upper 20s during the predawn and early morning hours on Monday.

Despite sunny skies on Monday, strong cold air advection and a tight pressure gradient will only allow highs to reach the upper 40s to around 50 for most of southeast GA and the 50-55 range elsewhere. Dewpoints plunging through the teens inland and lower 20s at coastal locations will combine with northwesterly winds sustained at 15-25 mph with frequent 30-40 mph gusts to create potential Red Flag conditions, denoting an increasing wildfire danger across our area.

Weakening Arctic high pressure will pivot eastward along the northern Gulf coast on Monday night, resulting in a loosening local pressure gradient that will yield gradually decreasing northwesterly winds, especially at inland locations. A hard freeze will be possible across inland southeast GA and the Suwannee Valley, with a light freeze extending to coastal locations. The northwesterly breeze will drop wind chill values down to the low and mid 20s, likely prompting Cold Weather Advisories for northeast and north central Florida in subsequent forecasts later today or tonight.

LONG TERM /TUESDAY THROUGH FRIDAY/

Main Hazards During the Long Term Period: - Elevated Fire Danger Possible on Tuesday Afternoon

- Light Freeze and Widespread Frost on Tuesday Night - Warming Trend Wednesday through Friday

- Some Beneficial Showers and Fog Potential Late in the Week

Deep troughing will shift offshore on Tuesday, leaving behind a dry northwesterly flow pattern that will quickly transition to zonal by midweek and then southwesterly on Thursday downstream of a quickly approaching trough of Pacific origins. At the surface, Arctic high pressure will gradually weaken as it settles over the FL peninsula on Tuesday afternoon and night, with this feature then pushing offshore of the southeast FL coast by Wednesday afternoon. Sunny skies and a very dry air mass will result in highs rebounding to the mid and upper 50s area-wide on Tuesday. Dewpoints remaining in the teens and 20s will keep at least an elevated wildfire danger in place across our area despite decreasing west-northwesterly surface winds, with long durations of critically low humidity values forecast at inland locations.

Although some thin high clouds will begin to enter our area from the northwest on Tuesday night and early Wednesday, decoupling winds early in the evening will create radiational cooling, with a light freeze possible at most inland locations and areas to potentially widespread frost potentially extending to coastal locations, where lows may fall to the mid 30s. Temperatures will then quickly moderate on Wednesday as southwesterly low level flow develops shortly after sunrise. Inland highs should approach late February climatology, with values climbing to the upper 60s and lower 70s, while colder shelf waters keep coastal highs in the mid to upper 60s. Lows on Wednesday night will remain in the 40s area-wide.

Shower chances will gradually increase downstream of the next approaching frontal boundary from Thursday afternoon through Friday. A dry air mass will initially linger across northeast and north central FL on Thursday, with showers possible by late afternoon across mainly inland southeast GA as PWATs begin to increase. Model blends currently indicate scattered showers traversing our region o Thursday night and Friday. Highs will climb well into the 70s on Thursday and Friday despite increasing cloud cover, with lower 80s possible across north central FL, especially on Friday. Warm air advection should keep lows in the 50s region-wide on Thursday night.

AVIATION /06Z SATURDAY THROUGH 06Z SUNDAY/

Low stratus and fog will continue to move northeast across the area from the Gulf early this morning. Conditions will trend toward VFR later this morning, with prevailing VFR conditions through the day. Precipitation chances will slowly increase from northwest to southeast late this afternoon through the evening as a cold front approaches. Restrictions are expected in showers and stratus this evening.

Thunderstorms are possible as the front moves through overnight, but the best chance will be after this 06z TAF period.

MARINE

High pressure will sink southeast of the area Today. A cold front will move southeast across the region Tonight into Sunday morning. A few thunderstorms will be possible as the front moves through. High pressure will build from the west Sunday afternoon, with winds increasing through the day. Gales will be possible from Sunday afternoon through Monday morning. The high pressure ridge will build overhead of FL Tuesday. The high will move off to the east Wednesday and Thursday.

Rip Currents: Moderate through Sunday.

FIRE WEATHER

- Red Flag Conditions Possible Across Much Of Our Area On Monday - High Daytime Dispersion Values Each Afternoon Through Monday - Elevated Nighttime Dispersion Values On Sunday Night - Long Durations Of Critically Low Humidity On Tuesday Inland

Showers and a few thunderstorms will overspread southeast Georgia late this afternoon through the evening hours. A few thunderstorms could become strong to possibly severe across southeast Georgia. Breezy southwesterly surface and transport winds will create high daytime dispersion values at most locations this afternoon, with good to marginally high values elsewhere. Shower activity will then migrate across northeast and north central Florida on Saturday night and Sunday. Breezy west-southwesterly transport winds on Saturday night will shift to northwesterly during the early to mid-morning hours on Sunday, with strengthening speeds throughout the rest of the day creating very high daytime dispersion values area-wide on Sunday afternoon.

A much drier air mass will filter into our area on Sunday afternoon, with minimum relative humidity values possibly approaching critical thresholds. Gusty northwesterly surface and transport winds on Sunday night will yield elevated nighttime dispersion values nearly area-wide. Red Flag conditions will be possible across most of our area on Monday, as breezy northwesterly surface winds combine with critically low humidity values and drying soil conditions. Strong transport speeds through early afternoon will create high to very high daytime dispersion values. Northwesterly surface and transport winds on Tuesday will then diminish, with long durations of critically low humidity values forecast at most inland locations.

FOG POTENTIAL AND OTHER REMARKS: Dense fog and widespread low clouds are likely during the predawn through mid-morning hours on Saturday across inland north central and portions of inland northeast Florida. Super fog development is possible in the vicinity of smoldering fires, especially ones producing copious amounts of smoke. A few strong to isolated severe thunderstorms are possible late Saturday afternoon through Saturday evening across southeast Georgia, with strong wind gusts being the main hazard for any stronger storms that develop. Widespread subfreezing temperatures are forecast area-wide late on Monday night through early Tuesday morning, with widespread frost and a possible light freeze forecast from late Tuesday night through early Wednesday morning.

CLIMATE

Record High Temperatures will be possible again this afternoon.

Sat, February 21: KJAX: 86/2019 KCRG: 84/2019 KGNV: 89/2019 KAMG: 87/2018

PRELIMINARY POINT TEMPS/POPS

AMG 83 53 61 30 / 60 90 20 0 SSI 76 57 67 34 / 30 70 40 0 JAX 86 60 70 33 / 10 50 50 0 SGJ 84 61 72 36 / 0 40 60 0 GNV 85 62 71 33 / 0 50 40 0 OCF 85 61 72 33 / 0 40 50 0

JAX WATCHES/WARNINGS/ADVISORIES

FL...None. GA...None. MARINE...Gale Watch from Sunday evening through Monday morning for AMZ450-452-454. Gale Watch from Sunday afternoon through Monday afternoon for AMZ470-472-474.