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

- Increasing Daily Thunderstorm and Heavy Downpour Coverage. Flood Watch In Effect Through This Evening Along & North of I-10. Waves of Heavy Downpours Will Increase Flooding Threat Through This Week

- Moderate Rip Current Risk all Area Beaches Today

- Coastal and Marine Hazards Tuesday Through Much of This Week. Strong & Gusty Northeast Winds Arrive Tuesday Morning. Small Craft Advisory Conditions Likely for the Atlantic Waters Tuesday through

- Wednesday with occasional Gusts to Gale Force. Deadly Rip Currents, Rough Surf & Substantial Beach Erosion Likely. Minor to ally Moderate Tidal Flooding Risk Tuesday through Thursday Along the Atlantic

- Coast, ICWW & Tidal Tributaries of the St. Johns & St. Marys River Basins

NEAR TERM /THROUGH TONIGHT/

Main Highlights Today and Tonight:

- Flood Watch extended for the same area (I-10 and areas north) through 8 PM

- Scattered strong thunderstorms, capable of heavy rainfall and potential flooding, this afternoon across north central FL

Soggy conditions continue today with most seeing rain again today as a cold front slides southward across the area. The steady moist southwesterly flow will continue to feed shower and thunderstorm development along the front as it pushes through SE GA this morning and gradually across NE FL during the afternoon. An upper shortwave digging into the southeastern US today will bring additional lift along the front.

While instability will be lacking across SE GA due to cooler surface temperatures, elevated showers and steady stratiform will remain capable of efficient rain rates up to 1-3" per hour through the afternoon. Diurnal heating will be stronger and encourage sufficient destabilization across NE FL and north-central FL through the afternoon which will be more of a concern regarding the potential for isolated to scattered strong thunderstorms. With the nearly front-parallel steering flow there could be a more favorable training set up south of I-10 this afternoon and evening, elevating the risk of localized flash flooding, especially for the urban areas in north central FL (Gainesville, Ocala, and St Augustine and Palm Coast). The latest HREF guidance does indicate a reasonable probability, around 30-50%, for localized rainfall of 3"+ early this evening. Given the potential for flooding once again, the Flood Watch for areas along and north of I-10 has been extended but given the mainly stratiform rain expected there, an early cancellation isn't out of the question.

The cold front will slow tonight as it pushes into central FL. Prolonged stratiform rain is expected for NE FL overnight as the aforementioned shortwave lifts across the front. An additional inch or two of rain is possible through the overnight stretch but more gradual hourly rates will limit flood threat.

Cloudy, soggy conditions will subdue temperatures and compress the diurnal range north of I-10 where temperatures are likely to only reach the upper 70s this afternoon. Further south a bit more heating is expected, especially across north central FL where highs are expected to be in the mid 80s. Temperatures will begin to drop behind the cold front tonight but not significantly; lows in the mid/upper 60s are expected north of I-10 with low 70s to the south.

SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/

Main Highlights This Period:

- Potential for rounds of heavy rainfall continues Tuesday across NE FL and the coast, then shifting to the NE FL coast on Wednesday

- Strong northeast flow pattern through midweek with potential for dangerous Surf Zone conditions, coastal flooding, and gusty winds

Tuesday, the strong trough axis extending from Nova Scotia will depart away from the east coast into the western Atlantic waters as the southern extension of the trough broadens east of the SE US coast with trailing shortwave energy across the coastal waters westward along the FL panhandle. Behind the trough, mid/upper level ridging will shift across the Great Lakes and Midwest OH valley which will support surface a high pressure center building into the Mid Atlantic states and then the Delmarva Peninsula through the day. The surface cold front will be south of I-10 and quickly sink into north central FL from morning into afternoon, with strong winds developing as the high builds north of the region and tightens the local pressure gradient. Breezy NE winds will increase to 15-20 mph with gusts to 30-35 mph along the coast from Mayport/Jax beaches northward into the SE GA coast with inland winds 10-20 mph with gusts to 25-30 mph. As the high builds in a bit more from the north, the potential for windy conditions will increase Tuesday afternoon from the coast into portions of the St Johns river from Jacksonville to Palatka with sustained winds 15-25 mph and gusts 35-45 mph.

Rounds of heavy rain and will shift across NE FL as the strong NE flow develops convergent bands of showers that will focus along the coast with less coverage of showers north of US highway 84. Isolated to scattered embedded T'storms will form generally south of I-10 where some elevated instability will linger north of the frontal boundary, helping to enhance rainfall rates. This will lead to widespread 1-2 inch amounts along and south of I-10 with isolated totals of 3-4 inches.

Highs will be limited Tuesday from clouds and rainfall with mid to upper 70s over much of the area to low 80s over north central FL. Lows Tuesday night will range from near normal in the low 60s over inland SE GA and to the low 70s along the NE FL coast.

Wednesday, the high to the north shifts to the NE as the front remains across the central FL peninsula. Inverted troughing will develop over the offshore waters and continue a strong local pressure gradient with potential for wind advisory conditions shifting more into the NE FL coast will persist as gusts to 35-40 mph making their way across the entire St Johns river basin. The highest rainfall chances will be along the NE FL coast as convergent bands of showers move onshore with decreasing chances across the Suwannee Valley and silent pops NW of Waycross. Cooler highs prevail in the upper 70s to around 80 due to the enhanced onshore NE flow. Heaviest Rainfall amounts be shift to along the NE FL coast into north central FL of where half inch to one inch will fall with localized higher amounts up to 1.5 - 2.0 inches.

Drier air will settle into SE GA Wednesday night cooling lows below normal into the upper 50s to near 60 over inland SE GA with near normal lows in the mid 60s inland NE FL, but warming to to the mid 60s along the SE GA coast and low 70s NE FL coast. Breezy winds will remain overnight 15-20 mph with gusts to 30 mph along the coast gradually diminishing into early Thursday morning with winds decreasing inland.

The strong NE flow Tuesday and Wednesday and high astronomical tides due to the approach of the new moon will push water levels along the coast, ICWW, and the St Johns river into at least Minor flood stage around each high tide cycle. Water levels may reach moderate flood stage within portions of the St Johns river due to a combination of high tides, heavy rainfall and reverse flow conditions which largely prevent drainage of the river into the Atlantic. While a Coastal Flood advisory will most likely be issued for this event, the need for a Coastal Flood Watch will be evaluated over the next 24 hours as we get closer to the event.

LONG TERM /THURSDAY THROUGH SUNDAY/

Main Highlights This Period:

- Elevated northeast flow continues through the end of the week with potential for Minor to Moderate Tidal Flooding, Deadly Surf, and Gusty Coastal Winds

- Strengthening winds and increasing Rain and Thunderstorms Chances return Next Weekend

Thursday, broad surface high pressure will be north of the region as the frontal boundary remains across the central FL peninsula. The front will remain across central FL Friday as high pressure rebuilds across the OH valley into the Mid Atlantic states which will begin to increase onshore winds further across the area as local pressure gradient tightens again.

This weekend, a closed mid/upper level will develop as broad troughing shifts away from the east coast into the Atlantic and Bermuda ridging aloft builds towards the Bahamas to the SE. The closed mid/upper level trough will lift into the lower/middle MS river valley around the Bermuda ridging to the SE. This will induce a surface low pressure forming over the NW Gulf waters that will shifts to the Gulf coast, lifting the frontal boundary through NE FL Saturday and north of the area on Sunday. This will bring widespread rainfall chances across the area Saturday and Sunday with potential for heavy rainfall amounts. The National Hurricane Center is currently monitoring the potential for the low to form into a tropical Depression late this week as north and east from the western Gulf waters to the central Gulf coast, with a moderate chance of development. No direct impacts are expected to our area from this system at this time.

Persistent elevated to breezy NE to ENE onshore flow will continue through Saturday with southerly winds Sunday as the front lifts north of the area, which will continue a threat for minor to possible low-end Moderate tidal flooding into next weekend. Dangerous surf conditions, Rip Currents, and minor to moderate beach erosion will also be likely due to the elevated winds.

High temperatures will trend below average this period. Low temperatures will begin near to below normal inland/above normal along the coast and warm to near normal inland into Saturday.

AVIATION /12Z MONDAY THROUGH 12Z TUESDAY/

A cold front tracking south across the area today will bring low ceilings, generally around MVFR, through this afternoon. A disturbance moving across the front will bring waves of stratiform rain showers with embedded heavy rain leading to degraded visibility at times. Thunderstorm potential is higher at KGNV and KSGJ this afternoon, less likely further north. Low stratus will spread inland on northeasterly winds through the evening hours leading to IFR and possibly LIFR ceilings. Additional waves of showers are expected overnight. Ceilings may occasional break during moderate to heavier rain but the prevailing conditions will be restricted.

MARINE

A cold front will push into north to south across the waters today. As it moves through, winds will shift to the northeast and increase to Caution levels late this afternoon and through the evening hours. Conditions deteriorate Tuesday as a surge of strong northeasterly winds arrive leading to Small Craft Advisory conditions early Tuesday morning across the southeast Georgia waters and gradually spreading south into northeast Florida waters after sunrise and through the afternoon. Due to the potential for frequent gusts to gale force, a Gale Watch is in effect for Tuesday afternoon for waters north of Saint Augustine. Prolonged northeasterly winds are expected to gradually decrease through Friday and shift onshore this weekend.

Rip Currents: A moderate risk at all area beaches Today. Dangerous high surf conditions are expected to develop on Tuesday as northeasterly winds strengthen, resulting in battering surf up to 10 feet and deadly rip currents from Tuesday through the end of next week.

FIRE WEATHER

- Areas Of Low Daytime Dispersions Through Tuesday

- High Minimum Dispersions Tuesday Night And Wednesday Night

Waves of rain with embedded thunderstorms through this week as a wave of low pressure along the central Gulf coast moves east along an associated frontal boundary which will gradually sink south across the area. Lower mixing heights across much of the area due to low cloud cover, showers an thunderstorms will lead to poor dispersions Monday for the entire forecast area, and low dispersion continues for portions of northeast Florida Tuesday. An area of low pressure is expected to develop just to the northeast Tuesday as high pressure builds to the north into midweek, bringing elevated northeasterly winds to the area, especially along coastal locations.

Fog Potential... Patchy fog is possible this morning across inland areas, especially where heavy rainfall amounts occurred. Gusty and erratic winds will be possible in and near thunderstorms. Locally heavy rainfall with localized flooding possible today and Tuesday, potentially returning this weekend.

HYDROLOGY

A tropical-like airmass will remain over the area today. Sea breeze driven thunderstorms this afternoon and then a passing wave of low pressure this evening and overnight may lead to periods of heavy rainfall across areas that have already received 3 to 7 inches over the last three days, mainly locations along and north of I-10. Additional rainfall amounts of 1 to 3 inches with localized amounts of 4 to 5 inches may result in flash flooding, especially in urban areas today and tonight. A Flood Watch is in effect through Monday morning for Southeast GA and portions of Northeast FL along the I-10 corridor.

Next week, a local nor'easter and high astronomical tides will combine and result in minor and potentially moderate coastal flooding during times of high tide along the Atlantic coast, beginning with the late evening high tide on Tuesday and likely continuing through Thursday during each high tide. Minor to moderate flooding may also become possible within the St. Johns River basin from Wednesday morning through next weekend around times of high tide.

TIDES/COASTAL FLOODING

Astronomical higher than normal tides will continue into this evening with Minor Flooding occurring during times of high tide within the St. Johns River Basin and possibly along the NE FL Atlantic coast/ICWW. Recent water levels today (e.g., Dames Point) have peaked at around 1.6 feet above Mean Higher High Water (MHHW). This may continue into the evening for the St Johns River Basin.

PRELIMINARY POINT TEMPS/POPS

AMG 74 65 74 62 / 80 40 50 20 SSI 79 70 79 68 / 80 70 90 70 JAX 79 69 76 68 / 80 70 90 70 SGJ 82 71 79 71 / 90 90 90 80 GNV 82 70 77 68 / 90 80 90 60 OCF 85 72 80 70 / 80 80 90 60

JAX WATCHES/WARNINGS/ADVISORIES

FL...Flood Watch until 8 PM EDT this evening for FLZ023-024-120-124- 125-220-225-322-325-425. High Risk for Rip Currents from Tuesday afternoon through late Wednesday night for FLZ124-125-138-233-333. GA...Flood Watch until 8 PM EDT this evening for GAZ132>136-149- 151>154-162-163-165-166-250-264-350-364. High Risk for Rip Currents from Tuesday morning through late Wednesday night for GAZ154-166. MARINE...Small Craft Advisory from 2 AM to 5 PM EDT Tuesday for AMZ450- 470. Gale Watch from Tuesday afternoon through late Wednesday night for AMZ450-452-470-472. Small Craft Advisory from 8 AM to 5 PM EDT Tuesday for AMZ452- 472. Small Craft Advisory from 5 PM Tuesday to 5 AM EDT Thursday for AMZ454-474.