Marine Weather and Tide Forecast for Neptune Beach, FL

NEAR TERM /THROUGH TONIGHT/

Main Highlights through Tonight:

- Scattered Strong to Isolated Severe Storms Possible Late this Afternoon and Evening, Mainly along the I-95 and U.S. Highway 301 Corridors. Potential Hazards: Damaging Wind Gusts, Small Hail, Frequent Lightning Strikes, and Heavy Downpours.

- Small Craft Advisory Conditions Begin Late Tonight Offshore.

Afternoon surface analysis depicts strong low pressure (991 millibars) that was pivoting across the Upper Midwest, with a trailing cold front crossing the southern Plains states.
Meanwhile, a warm front has lifted northward of our region into south central GA
Aloft
southwesterly flow continues to deepen locally downstream of a trough that was digging southeastward from the Plains states towards the Mississippi Valley. Latest GOES-East derived Total Precipitable Water imagery indicates that deeper moisture is surging northward from north central FL in the wake of the overnight and morning warm frontal passage, with PWATS above 1.5 inches located across north central FL and values rising to around 1.25 inches for the rest of northeast FL and coastal southeast GA. Meanwhile, a drier air mass remains in place across inland southeast GA, where values were in the 0.75 - 1 inch range. A healthy cumulus field has developed where PWATs are above 1 inch, while a flatter field was located over inland southeast GA, where the air mass was more subsident.
Mesoscale boundaries such as the St. Johns River breeze have already developed a few showers that were moving quickly across eastern Duval County. Temperatures at 19Z were generally in the low to mid 80s inland and the mid to upper 70s behind a pinned Atlantic sea breeze at coastal locations.
Dewpoints ranged from the mid and upper 50s across inland southeast GA to the 60s elsewhere, except around 70 for portions of coastal northeast FL.

Deeper moisture surging northward from the FL peninsula this afternoon will combine with an existing warm and unstable air mass over our area to develop scattered to numerous thunderstorms during the mid to late afternoon hours along the I-95 and U.S. Highway 301 corridors in north central and northeast FL. This activity will likely be initially triggered by mesoscale boundary interactions, with activity then interacting with convective outflow boundaries emanating northward from central FL to increase the coverage and intensity of showers and thunderstorms for locations south of I-10 through early this evening. Convective outflows moving north and northwestward will then spread activity towards the I-75 corridor in north central FL and the Suwannee Valley, as well as coastal southeast GA and the Okefenokee Swamp towards sunset.
Given cool mid- level temperatures and steep lapse rates already in place, along with ML CAPE values in excess of 2,000 j/kg, storms may pulse and become strong or even briefly severe in these areas into the evening hours. The Storm Prediction Center has maintained a Marginal (level 1 out of 5) Risk for severe thunderstorm development across our area, with downburst winds of 40-60 mph and small hail being the primary threats, along with frequent lightning strikes and locally heavy downpours.

Troughing will continue to deepen as it takes on a more neutral tilt tonight over the Upper Midwest, Great Lakes, and Mississippi Valleys. Southwesterly flow aloft will also continue to deepen downstream of this trough and its associated powerful cold front across our region, with flow aloft also becoming increasingly diffluent towards sunrise on Monday. Widespread showers and thunderstorms ongoing early this evening across the I-95 and U.S.- 301 corridors will tend to weaken towards midnight as activity attempts to build northwestward towards the Suwannee Valley and interior southeast GA. Strong to isolated severe storms will remain possible early this evening, with a break in activity expected to be short-lived overnight as the cold front enters the southeastern states and moisture levels continue to increase ahead of this strong boundary. A wave of showers and thunderstorms may develop over Apalachee Bay and the northeast Gulf during the predawn hours, with this activity rapidly spreading inland across the Suwannee Valley and southeast GA towards sunrise. Strong warm air advection and gusty southerly winds will keep lows in the mid to upper 60s tonight area-wide.

SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/

Main Highlights This Period:

- Scattered Strong to Severe Storms on Monday. Potential Hazards: Damaging Wind Gusts, Tornadoes, and Large Hail.

- Wind Chill Values Fall to the 20s and Lower 30s Area-Wide late Monday Night and Early Tuesday Morning.

- Light Freeze and Widespread Frost for Inland Southeast GA and Suwannee Valley on Tuesday Night and Early Wednesday Morning.

- Small Craft Advisory Conditions through Tuesday Afternoon.

A cold front will move southeast across the area Monday. Showers and thunderstorms will accompany this front. Conditions are expected to be favorable for severe weather, to include the potential for damaging winds, hail, and tornadoes. Due to frontal timing high temperatures will range from the lower 70s inland SE GA, to the lower 80s coastal NE FL.

High pressure will build from the west Monday night following the frontal passage. Strong cold advection will push temperatures down significantly through the night. Lows near freezing over inland SE GA, can be expected. Winds will continue to stir through the night, limiting frost potential.

The center of the surface high will build closer to the area Tuesday, but the region will be in the base of an upper trough, so while it will be dry, clouds will stream across. With cold advection continuing, it will be well below normal, with highs largely in the 50s. A few spots south of GNV could get to 60.

The surface high will build more toward the north Tuesday night, as region remains in base of upper trough. Clouds will move move off to the southeast, which will allow temperatures to fall further, with inland areas north of I10 experiencing a freeze.
With lighter winds, frost chances are high Tuesday night, except for coastal NE FL.

LONG TERM /WEDNESDAY THROUGH SUNDAY/

Main Highlights This Period:

- Warming trend late in the period.

Surface high pressure will be centered to the north northeast Tuesday night through Wednesday. Freezing temperatures inland expected north of I10. Winds will be fairly light, so frost is expected for all but coastal NE FL. Temperatures will begin to moderate Wednesday, but remain below average.

The region will be between a ridge of high pressure to the northwest and a trough of low pressure Wednesday night through Thursday night. The dry weather will continue during this time, with temperatures coming closer to normal.

The surface high pressure ridge will build overhead of the region Friday into Friday night, as temperatures rise above normal.

The high will sink to the south over the weekend, but dry weather will continue with temperatures continuing above normal.

AVIATION /18Z SUNDAY THROUGH 18Z MONDAY/

Showers and thunderstorms will gradually increase in coverage near the Duval County terminals and SGJ towards 20Z, with activity shifting northeastward towards coastal southeast GA, including the SSI terminal, and expanding westward towards the U.S. Highway 301 corridor by 00Z. TEMPO groups were used at these terminals for briefly strong wind gusts of 35 knots and IFR conditions during heavier downpours, mainly from 22Z through 03Z tonight. PROB30 groups were used at GNV due to uncertainty in how far west the convection will expand early this evening.
Convection should wane towards 05Z, but another round of showers and potential thunderstorms could develop over Apalachee Bay and the northeast Gulf, which may impact GNV after 08Z. Low stratus ceilings could develop towards sunrise at the regional terminals as well. Showers and thunderstorms will then increase in coverage and intensity across inland southeast GA and the Suwannee Valley after 12Z Monday, with potential impacts to the regional terminals after 15Z. PROB30 groups were used for strong wind gusts and potential IFR conditions during heavier downpours towards the end of the TAF period at all terminals.
Southerly surface winds will prevail after the conclusion of this evening's convective impacts, with speeds remaining sustained at 10-15 knots overnight at the coastal terminals and 5-10 knots inland after 06Z. South-southwesterly winds will then increase to around 15 knots and gusty after 13Z Monday.

MARINE

A strong low pressure center will pivot northeastward from the Upper Midwest across towards the Great Lakes states tonight. Showers and thunderstorms will develop late this afternoon near our near shore waters and will continue through this evening, with strong to isolated severe storms possible. This storm system's cold front will then enter the southeastern states late tonight, crossing our local waters on Monday afternoon. Southerly winds will strengthen over the offshore waters adjacent to northeast Florida late this afternoon and evening, where Small Craft Advisories are expected to develop overnight. Southerly winds will strengthen near shore this evening, and Small Craft Advisory conditions will develop shortly after sunrise on Monday. Strong to severe thunderstorms are forecast to impact our local waters on Monday afternoon, with the potential for damaging wind gusts, waterspouts, and large hail.

Winds will shift to westerly during the passage of the strong cold front, with strong northwesterly winds forecast on Monday night and Tuesday morning throughout our local waters as high pressure builds into the southeastern states. Winds will shift to northerly on Tuesday afternoon and then northeasterly by Wednesday as high pressure shifts northeastward towards the Mid-Atlantic coast. This strengthening high pressure center will wedge down the southeastern seaboard later this week, creating another round of Small Craft Advisory conditions on Wednesday night and Thursday. Winds and seas are expected to diminish by Friday afternoon.

Rip Currents: A moderate risk is expected with breezy southeast to southerly winds this afternoon at local beaches, along with surf/breakers of 2-4 ft, along with a greater impact from potential thunderstorm activity late this afternoon and evening. Gusty southwest to westerly winds on Monday will knock surf down slightly to 2-3 ft, but a moderate risk of rip currents will continue at all area beaches.

FIRE WEATHER

- AREAS OF MINRH LEVELS BELOW 30 PERCENT INLAND TUESDAY THROUGH Thursday

- AREAS OF HIGH DISPERSION MONDAY AND TUESDAY, AND AGAIN FRIDAY Through Sunday

- Patchy High Dispersions Ne Fl Thursday

A strong cold front will move southeast across the area on Monday. Showers and thunderstorms can be expected ahead of the front Tonight, with potential for strong to severe storms along front during the day Monday. High pressure will be the prevailing weather feature Tuesday through Sunday.

FOG POTENTIAL AND OTHER REMARKS: Significant fog potential is not expected Tonight. Thunderstorm chances through Monday, with chances for strong to severe storms. The greatest chance for the severe weather will be during the day Monday. A frost/freeze is forecast for Tuesday night, mainly inland areas north of I-10.

PRELIMINARY POINT TEMPS/POPS
AMG 67 75 33 54 / 40 90 10 0 SSI 65 76 38 54 / 70 80 10 0 JAX 67 83 36 57 / 70 80 10 0 SGJ 66 80 39 58 / 80 80 20 0 GNV 67 81 36 59 / 60 90 10 0 OCF 67 82 38 59 / 60 90 10 0

JAX WATCHES/WARNINGS/ADVISORIES
FL...None.
GA...None.
MARINE...Small Craft Advisory from 8 AM Monday to 11 AM EDT Tuesday for AMZ450-452-454.
Small Craft Advisory from 2 AM Monday to 2 PM EDT Tuesday for AMZ470-472-474.