Marine Weather and Tide Forecast for St. Augustine, FL

NEAR TERM /THROUGH TONIGHT/
Main Highlights through Tonight:

- Strong Storms and Locally Heavy Downpours Possible This Afternoon and Early Evening from I-95 to US Highway 301

- Heat Advisory in effect from Noon to 7PM for Northeast FL and portions of Southeast GA

Last of remaining showers from Brunswick west southwest to Live Oak have diminished with mid and high level debris clouds from the prior evening's convection remaining over the area with mostly clear skies over north central FL. Temperatures are cooling slowly inland into the upper 70s and low 80s along the coast with a trend to mid 70s inland and the upper 70s along the coast with very light south winds becoming southwesterly by sunrise 3-5 mph. Shallow ground fog may form over inland areas early this morning which received briefly heavy rainfall yesterday.

Today, a ribbon of shortwave energy between a strong mid/upper level western ridge and a trough over the Mid Atlantic states will move east southeastward across the southern Appalachians to the Carolina Piedmont through the course of today. This energy will remain just north of the area, but serve to sharpen the trough to the north further southward over the southeast states and begin to nudge a nearly stalled cold frontal boundary south and east from north GA into central GA and SC. Ahead of the front, very high PWATS shifting over SE GA by midday and over NE FL late in the afternoon hours with values ranging 2.0-2.4 inches. West to northwest flow will slow the progress of the convectively active Atlantic seabreeze across I-95 to near or just past US-17 where scattered showers and thunderstorms will become more numerous by mid afternoon as outflow collisions spur additional updraft growth amid strong diurnal heating. The favored coverage area for numerous afternoon thunderstorms will be between I-95 and highway 301 with the Gulf seabreeze arriving late over Ocala National Forest. West to northwest winds 5-10 mph will turn southeasterly 8-12 mph with gusts to 20 mph behind the Atlantic seabreeze.

Stronger storms will be possible along cell mergers and outflow interactions with the Atlantic seabreeze. An increase in shear late in the afternoon and Water loading will support a threat for isolated strong to locally severe gusty downburst winds 40-60 mph.
Storm motions will slightly increase as well from the west or west northwest, so a localized flood threat is in play with storms affecting the urban areas along I-95 and other low lying areas.

Most thunderstorms will begin to fade after 10PM with isolated storms through midnight, then a few showers may roll into inland SE GA as shortwave energy filters into the area late overnight with the front still north of the Altamaha river.

Highs today will rise to the mid and upper 90s along and west of I- 95 with mid 90s at the coast. Expecting a little higher humidity values today compared to yesterday which should keep our inland dewpoints in the low/mid 70s with upper 70s at the coast. These conditions will lead to peak heat indices 108-110 with isolated values up to 112 and therefore will post a Heat Advisory for NE FL the SE GA coast and portions of inland SE GA near the FL/GA state line including Echols, Clinch, and southern Ware county. Lows tonight will be muggy in the mid 70s inland and the upper 70s to near 80 along the coast

SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/
Main Highlights This Period:

- Coverage and Intensity of Afternoon and Evening Thunderstorms Increases Sunday.

- Strong Storms and Locally Heavy Downpours Possible.

Frontal boundary still on track to sag southward into SE GA on Sunday which will increase PWATs to over 2 inches across the local area before frontal boundary dissipates across NE FL on Monday. This will bring numerous to widespread showers and storms on Sunday which will interact with the East Coast sea breeze and expect isolated strong to severe storms with gusty winds to 40-60 mph along the I-95 corridor along with heavy downpours which could bring localized flooding in the more intense, slow moving storms, mainly impacting urban areas. Slightly drier air mass builds in aloft across SE GA on Monday, with only isolated convection during the afternoon, while lingering deep moisture across NE FL will interact with sea breeze fronts during the afternoon and evening to still help produce scattered to numerous afternoon showers and storms with locally heavy rainfall still possible in slow moving storms, mainly along the I-95/US-301 corridors once again. Isolated strong/severe storms will continue to be possible with gusty downburst winds of 40-60 mph across NE FL. Flood watches still not likely due to the recent drier stretch of weather this past week.

Despite the higher rainfall chances, still expect Max Temps into the lower/middle 90s both days, which will combine with dew point temps into the mid/upper 70s to produce Heat Index values into the 105- 110F range for coastal SE GA/most of NE FL and Heat Advisory headlines are still possible, but may not be required due to the earlier start to convection both days. Heat Indices generally peak out around 105F across inland SE GA.

LONG TERM /TUESDAY THROUGH FRIDAY/
Main Highlights This Period:

- Heat Advisory Conditions Possible Across Much of Our Area During the Early to Middle Portions of Next Week.

- Increasing Coverage of Afternoon and Evening Thunderstorms Possible Late Next Week into next weekend.

Long range models still suggesting ridging aloft will build over the region and suppress convection Tuesday and Wednesday which will support Max Temps into the upper 90s and heat indices pushing close to 110F area-wide and expect Heat Advisory headlines both days. Only isolated to widely scattered showers and storms are expected Tuesday with some increase to scattered storms on Wednesday. Isolated strong to severe storms still possible both days due to the extreme heating in the lower levels and convection getting a later start both days.

Next frontal boundary pushes into the region late in the week and stalls and dissipates into next weekend. This will increase rainfall chances and PWATs back above 2 inches with at least numerous showers and storms expected each day in the breezy SW flow, with best coverage closer to the I-95 corridor and across NE FL with locally heavy rainfall threat and isolated strong/severe storms with gusty winds to 40-60 mph expected. Max temps drop back down into the lower to middle 90s with peak heat indices around 105F and heat advisory headlines are not expected.

AVIATION /12Z SATURDAY THROUGH 12Z SUNDAY/

VFR conditions will remain through Saturday morning with light west to west northwest winds 5-8 knots turning southeast at the coastal sites including JAX from 17-19Z. Thunderstorms will develop across the area Saturday afternoon, which will likely affect area TAF sites. Restrictions and gusty winds up to 30 knots in and near afternoon storms 20-24Z can be expected. Storms will diminish after 02Z with broken to overcast mid and high level clouds through the end of the period with very light southwest winds.

MARINE

A stationary frontal boundary extending from the Carolina coast westward across the deep south will begin to drift south towards the Georgia waters today through Sunday, pushing the axis of Atlantic high pressure southward. This change in the weather pattern will create a prevailing offshore wind flow this weekend and early next week, with scattered to numerous afternoon and evening thunderstorms expected across our local waters each day. A few stronger storms will be possible during the late afternoon hours, with briefly strong wind gusts, frequent lightning strikes, and torrential downpours possible. Another front will approach the waters next week with offshore southwest winds increasing to near advisory levels by midweek.

Rip Currents:

Rip Currents: A moderate risk of rip currents is expected today through the weekend at Northeast FL and Southeast GA beaches due to onshore winds from the southeast this afternoon with surf heights 2 to 3 feet.

FIRE WEATHER
- Areas Of High Daytime Dispersion Values Inland This Weekend

Coverage and intensity of showers and thunderstorms will increase during the afternoon and evening hours area-wide this weekend. A gradual decrease in afternoon and evening shower and thunderstorm activity is then expected during the early to middle portions of next week. Very hot and seasonably humid conditions will otherwise prevail, with heat advisory conditions possible across portions of our area this weekend and next week. Surface and transport winds from the southwest and west are expected this morning, with transport winds shifting to northwesterly during the afternoon at inland locations. Elevated mixing heights will generally yield good daytime dispersion values at inland locations, while fair values prevailing at coastal locations. Northwesterly surface and transport winds will then prevail on Sunday, with marginally high daytime dispersion values possible at inland locations before thunderstorm activity increases during the afternoon hours.

Fog Potential and Other Remarks: Significant fog development is not expected during the next several mornings.

PRELIMINARY POINT TEMPS/POPS
AMG 94 75 94 73 / 30 20 70 40 SSI 96 78 94 75 / 60 40 70 50 JAX 97 76 95 74 / 70 40 80 60 SGJ 95 77 93 75 / 40 30 70 40 GNV 96 76 95 75 / 50 30 70 40 OCF 96 77 95 75 / 50 20 70 40

JAX WATCHES/WARNINGS/ADVISORIES
FL...Heat Advisory from noon today to 7 PM EDT this evening for FLZ021-023-024-030-031-035-038-120-124-125-132-136>138- 140-220-225-232-233-236-237-240-322-325-333-340-422-425- 433-522-533-633.
GA...Heat Advisory from noon today to 7 PM EDT this evening for GAZ152>154-162-163-165-166-264-350-364.
MARINE...None.