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

- Localized Dense Fog for portions of Inland Northeast FL through 9AM

- Isolated Strong to Severe TStorms for Southeast GA Late this Afternoon &. Primary Hazard: Strong Wind Gusts of 40-60 mph

- Gale Watches from Sun Afternoon through Mon Afternoon

- Extreme Drought Prevails Across Most of Our Region. Elevated Fire Danger Possible on Sun Afternoon & Tues Afternoon. Red Flag Conditions Possible on Mon Afternoon

- Light Freeze Possible Late Sun Night & Early Mon for Inland Southeast GA

- Widespread Freeze & Low Wind Chill Values Mon Night & Early Tues

UPDATE

Area webcams and visibility observations indicate localized dense fog mainly along the I-75 corridor. This will last until around 9 AM before lifting to stratus and eventually scattering out later this morning.

We're monitoring the development of a weak wave of low pressure that will translate east-northeastward across southern GA along a leftover frontal zone this afternoon. Pooling moisture along the that frontal feature will moisten previously dry layers aloft this afternoon, resulting a modestly destabilized warm sector across SE GA. Further south a mid-level capping inversion should keep the "lid" on convective potential across NE FL this afternoon and this evening. A prefrontal line of convection organizing and trailing the surface low will push a messy line of showers and embedded storms into SE GA early this evening. Some of the isolated storms may produce gusty winds up to 50 mph.

Otherwise, the warm start to the day (only a few degrees short of daily record High Minimum Temperatures) will kick off another record day of warmth with prefrontal mixing boosting temps into the mid and upper 80s this afternoon.

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 /12Z SATURDAY THROUGH 12Z SUNDAY/

IFR conditions are expected to prevail at the regional terminals through around 14Z due low stratus ceilings of 500-900 feet and locally dense fog. Ceilings will then lift to MVFR before 16Z, with VFR conditions expected to prevail by 18Z. Showers and isolated thunderstorms moving across inland southeast GA late this afternoon should approach the SSI terminal towards 23Z. Confidence was only high enough to include vicinity thunderstorms from 00Z-04Z at SSI within prevailing MVFR visibilities due to showers. Confidence was only high enough to indicate vicinity showers after 00Z at the northeast FL terminals. Southwesterly surface winds sustained at 5- 10 knots through around 14Z will increase to 10-15 knots by 16Z, with occasional gusts of 20-25 knots possible through around 22Z. Speeds will then diminish to 5-10 knots towards 00Z.

MARINE

Low pressure will develop over the southeastern states this afternoon along a slow moving frontal boundary. This low pressure center will move northeastward towards the coastal Carolina region tonight, dragging the cold front across our local waters on Sunday morning. Showers and a few potentially strong thunderstorms could impact the Georgia waters ahead of this storm system this evening, with showers and possibly a few embedded thunderstorms then pushing southeastward across the rest of our local waters late tonight and Sunday morning. Northwesterly winds will quickly strengthen in the wake of this frontal passage on Sunday afternoon, with Gale Watches posted for frequent Gale force wind gusts through Monday afternoon. Meanwhile, low pressure will parallel the Mid-Atlantic and New England coasts while rapidly strengthening from Sunday night through Monday night, with Small Craft Advisory conditions prevailing locally on Monday night. Arctic high pressure will then build along the northern Gulf coast on Tuesday and will then push southeastward across the Florida peninsula on Tuesday night, allowing for winds and seas to diminish across our local waters. This high pressure center will then push offshore by midweek ahead of another approaching cold front that should impact our local waters late in the upcoming week, with south to southwesterly winds prevailing in advance of this frontal boundary.

Rip Currents: Rip current risk will be moderate today thanks to breezy offshore flow and some remnant long period swells. Surf/breakers of 1-3 ft today will trend downward to around 2 feet or less this weekend.

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.