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

- Minor Tidal Flooding for NE FL Atlantic beachfront and the St. Johns River basin through this evening

- Moderate Risk of Rip Currents at local beaches

- Isolated Thunderstorm Activity Returns Mid Week. Greater chances of thunderstorms starting Thursday through the weekend.

NEAR TERM /THROUGH TONIGHT/

Main Highlights Today and Tonight:

- Moderate rip current risk at Atlantic beaches

- Minor flooding along the St. Johns River Basin during times of high tide through this evening

Weak low level troughing oriented from the northeast Gulf to coastal southeast GA along with increasing atmospheric moisture levels will continue to support isolated convection (POPs about 10- 20 percent) across parts of northeast FL well to the south of I-10. Dewpoints and moisture are much lower as one goes into southeast GA. Meanwhile, the mid to upper level trough across the area from central GA to the central FL panhandle will allow for mid to high clouds to stream across northeast FL through tonight. This trough is expected to weaken overnight. Max temps expected to be in the lower 90s for most of southeast GA while northeast Fl in more of the high clouds will be in the upper 80s to about 90 degrees. These max temps are not too far from the record highs especially for JAX and CRG climate sites. Low temps will continue to trend back closer to normal values with lower/middle 60s over inland SE GA and middle/upper 60s over inland NE FL and lower 70s along the Atlantic Coast. Expecting at least some patchy fog and low stratus clouds late tonight into early Wednesday morning as boundary layer winds remain light and skies will tend to be mostly clear. This fog and stratus potential is most favorable for southeast GA.

SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/

Main Highlights through Tonight:

- Return to summer like pattern: Scattered thunderstorms Wednesday and Thursday, mainly NE FL, with highs in the upper 80s to low 90s.

Wednesday, an upper level closed mid level low will drift southward from the FL panhandle into the eastern Gulf waters as mid/upper level ridging moves east from the central Appalachians to the Mid Atlantic coast. Surface high pressure near the Delmarva peninsula will move into the Atlantic waters NE of the region as a weak surface front lifts north of the area with deep southeast flow increasing moisture levels across NE FL with PWATs (Precipitable Water levels) up to 1.75 - 2.00 inches. The Atlantic seabreeze will press well inland with isolated showers along the boundary moving inland across SE GA from the coast and bit higher coverage of showers across southern zones (Flagler county, southern St Johns river basin, Marion county) where widely scattered thunderstorms will develop and pulse during the afternoon. A few storms may be briefly strong over north central FL as 500 mb temperatures remain cool (-8 to -9C) which may support brief gusty downburst winds to 40- 50 mph as lingering dry air may enhance downdrafts. Otherwise the scattered showers and T'storms across portions of NE FL will end by sunset having shift west of I-75 while isolated showers will weaken before sunset over SE GA. Atlantic seabreeze will keep coastal highs in the mid 80s with near 90 readings west of highway 301.

Wednesday night, closed mid level low will shift away to the SW as mid/upper level ridging strengthens over southern Appalachians. Surface high pressure will strengthen a bit east of the Outer Banks of NC with a weak inverted trough developing over the coastal waters in the southeasterly flow as shortwave energy shifts in from the ESE with isolated overnight coastal showers moving onshore the NE FL coast. While mid to high level clouds will remain over the coastal waters, coast and north central FL, mostly clear skies and near calm winds over inland areas will develop low stratus and and patchy fog, locally dense, over inland SE GA. Light onshore ESE winds will keep lows above normal in the mid 70s while less clouds inland allow lows to fall near normal in the upper 60s to near 70.

Thursday, the weak inverted trough will shift to the NW from the coastal waters as the surface high shifts eastward between the Outer Banks and Bermuda. Deeper flow aloft will become more southerly with PWATs rising above 2.00 inches across NE FL and 1.75 - 2 inches across SE GA. The increased moisture, inverted trough and inland moving Atlantic seabreeze will create scattered showers becoming numerous across NE FL. Strong heating with interior highs in the low 90s will also help support scattered T'storms, but slightly warmer 500 mb temperatures near -6C should help limit potential for gusty winds. However, the much higher moisture content will allow for briefly heavy downpours which may create localized pocket of half in to one inch totals. Showers and storms will end near sunset with loss of daytime heating.

Thursday night, patchy fog and low stratus will return over inland SE GA as winds become calm while remaining ESE 5-10 mph along the coast. Similar to Wednesday night, Thursday night lows will be in the upper 60s to near 70 inland the mid 70 along the coast.

LONG TERM /FRIDAY THROUGH TUESDAY/

Main Highlights This Period (Friday through TUESDAY):

- Above normal thunderstorm chances with strong to marginally severe storms possible Sunday.

- Local Nor'easter Conditions potential next week.

Friday, mid/upper level ridging just off the SE US coast remains as a closed mid level shortwave trough moving east of the central plains merges with a broad northern trough over the Midwest/Great Lakes. This pattern will keep high pressure NE of the area bringing a moist ESE onshore flow to the area as a surface low well to the west moves eastward from the Ozarks into the TN valley Friday. A weak warm front along the Gulf coast will extend eastward into the area. This front will become a focus for increasing coverage of showers with numerous shower coverage Friday for much of the area. A very moist airmass and strong heating will support scattered T'storms forming in the afternoon.

Saturday, ridging aloft northeast of the region will extend SSW to the northern Bahamas while strong shortwave trough diving SE from Manitoba into the northern plains pushes shortwave energy through the mid south and southern Appalachian mountains. This will cause the surface low to move eastward through the TN Valley Saturday to our north. A Gulf coast warm front will lift north of the area with numerous showers and scattered T'storms for most of the area as a very moist airmass remains with light southeast surface winds veering to southerly in the mid levels.

Sunday through Tuesday, there remains uncertainty in the timing and development of what may be one or more waves of low pressure develop over the northern Gulf waters along a stalling cold frontal boundary and moving eastward through the area with numerous to widespread showers and embedded T'storms. At this time, the GFS and ECMWF both keep the frontal boundary across NE FL Monday and Tuesday, with the latter indicating some drier air filtering into portions of SE GA Tuesday, but keeping numerous to widespread showers scattered T'storms over NE FL. The 90th percentile (high end) rainfall amounts are 4-6 inches of rain along and north of I- 10, but appears most likely that 1-2 inches amounts will be common totals.

Strong high pressure will build to the north on Tuesday with a strong pressure gradient over the region and increasing NE winds that may bring a return dangerous Marine and Surf zone conditions into Wednesday. Temperatures will begin above normal with low 90s inland and near normal along the coast in the mid to upper 80s. High temperatures will trend to near normal by Monday with highs in the low to mid 80s over SE GA and the mid to upper 80s over NE FL, then below normal on Tuesday in the mid to upper 70s for most areas and low 80s over north central FL as the front remains stalled near or just south of NE FL. Lows will be above normal low 70s inland and the mid 70s along the coast through Monday, then trend below normal by Tuesday night as drier air arrives north of the front over inland SE GA and the Suwannee Valley.

AVIATION /18Z TUESDAY THROUGH 18Z WEDNESDAY/

VFR conditions prevail. Light south to southwest winds except for a sea breeze wind shift expected at SSI, SGJ, CRG, and JAX this afternoon. Rainfall chances remain low at about 10-20 percent for the northeast FL TAFS, but sufficient chances for either VCSH or VCTS for GNV this afternoon. Patchy fog and some stratus will be possible for VQQ, JAX, and GNV late tonight. IFR probabilities, though too low for the TAFs, are highest for GNV and VQQ late tonight/early Wednesday.

MARINE

High pressure over the region early this week brings light winds with afternoon onshore breezes developing along nearshore waters due to the Atlantic sea breeze. As the high pressure system shifts northeast mid to late week, a predominant east to southeast wind pattern takes over and persists into the weekend. This onshore flow will draw in higher moisture levels, resulting in scattered showers and embedded thunderstorms Thursday and Friday through the weekend.

Rip Currents: A combination of long period east swells near 1-2 ft, onshore flow, and prior surf conditions suggest a low-end moderate risk of rip currents through Wednesday.

FIRE WEATHER

- LOCALLY LOW DISPERSION FOR INLAND SE GA THIS AFTERNOON. - CRITICALLY LOW AFTERNOON HUMIDITY FOR INLAND SE GA THIS AFTERNOON.

Very light transport winds and a sea breeze slowly moving inland this afternoon will lead to low inland dispersion for Southeast Georgia and into the Suwannee Valley as gradual mixing will drop humidity down to near critical. A few showers will develop south of I-10 through sunset with a few T'storms over north central Fl and the Ocala National Forest, but will be dry northward into Southeast Georgia.

Through the second half of the week, transport flow will shift southeasterly leading to an upward trend in moisture and afternoon dispersions. With the return of moisture over the area, chances of showers and storms increase with highest chances over north central FL as scattered showers and isolated storms will Wednesday and Thursday. By the end of the week, coverage expands but highest thunderstorm chances remain focused across northeast FL.

Fog Potential...Patchy fog over inland locations Tonight, mainly for inland southeast GA where cooler temps, calm conditions, and clear skies are likely.

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.

CLIMATE

Near record high temperatures today for JAX and CRG Climate sites. Probably falling just short of the records here:

September 29th: KJAX: 92/1936 KCRG: 92/2016

PRELIMINARY POINT TEMPS/POPS

AMG 66 90 68 90 / 10 0 0 20 SSI 73 84 74 85 / 10 10 10 10 JAX 70 87 71 87 / 10 20 10 30 SGJ 72 85 74 86 / 10 20 20 30 GNV 68 89 70 90 / 10 20 0 60 OCF 69 90 70 92 / 20 30 10 60

JAX WATCHES/WARNINGS/ADVISORIES

FL...Coastal Flood Advisory until 8 PM EDT this evening for FLZ125- 132-137-138-225-233-325-333-633. GA...None. MARINE...None.