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

- Scattered Showers along the Northeast Florida Coast Today. Brief Heavy Downpours Possible Along the I-95 Corridor

- Strengthening Onshore Winds and Increasing Marine and Coastal Hazards Expected through Saturday. High Rip Current Risk at All Area Beaches. Frequent Wind Gusts of 30-35 mph at Coastal Locations through this Evening. Small Craft Advisories through Friday Night for the Atlantic Waters. High Surf Advisories at Area Beaches through at Least Friday Night. Minor Coastal Flooding Around Times of High Tide from Thursday Evening through Friday Morning Along the Atlantic Coast. Minor Tidal Flooding Around Times of High Tide within the St. Johns River Basin Possible from Friday through the Weekend and Early Next Week.

- Much Cooler and Drier Conditions Expected on Friday and Saturday Nights as Winds Diminish at Inland Locations.

- Warming Trend Takes Shape Next Week, But an Unseasonably Dry Air Mass Persists Across Our Region Sunday through Monday.

NEAR TERM /THROUGH TONIGHT/

Main Highlights:

- Scattered Coastal Showers with brief heavy downpours along Portions of the Northeast FL Coast.

- Breezy onshore winds and dangerous rip current/surf conditions.

Breezy winds 10-20 mph with gusts to 25 mph along the coast early this morning have backed from northeasterly to northerly as a cold front has pushed south of the area into central FL. Dewpoints are lowering slowly into the upper 60s along the SE GA coast and inland NE FL north of Gainesville with mid 60s over inland SE GA. With the drier airmass and northerly surface winds continuing through sunrise, moisture levels will continue to gradually fall to the low/mid 60s over inland SE GA to low 70s along the NE FL coast with temperatures lowering into the upper 60s along and north of I-10 away from the coast, low 70s along the SE GA coast and mid 70s along the NE FL coast. Low stratus will also sink southward from the SE GA coast and Altamaha river into I-10 and the NE FL coast to the St Johns river.

Today, a mid to upper level trough over the southern Appalachians will dig southeastward through this evening as an Omega ridging over southeastern Canada persists. At the surface, breezy northeast onshore flow will increase as strong high pressure extending from Quebec and New England wedges down the southeast US coast while low pressure deepens east of the Outer Banks of NC to our northeast. Scattered coastal showers, due to coastal convergence, will move onshore the NE FL coast mainly from the JAX beaches southward into Flagler Beach and the southern St Johns river basin. Cloudy, cool flow will limit highs to the upper 70s over SE GA and the NE FL coast from the JAX beaches northward with broken, mostly cloudy skies will allow highs to reach the low to mid 80s near I-75 over inland NE FL. Winds will be very breezy 15-25 mph gusting to 30-35 mph along the coast and into the St Johns river basin, diminishing slightly inland to 12-18 mph with gusts to 25 mph.

Tonight, drier air will continue to filter into the area from the north with lower dewpoints and mostly cloudy along the coast and partly cloudy inland. Winds will remain very breezy 15-20 mph with gusts to 30 mph along the immediate coast and 10-15 mph inland. Lows will fall to below normal levels in the low 60s over inland SE GA, moderating to near normal levels in the low 70s along the NE FL coast.

SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/

Main Highlights This Period:

- Gusty North to Northeasterly Winds Will Maintain Marine and Coastal Impacts on Friday and Saturday.

- Minor Coastal Flooding Likely Around Times of High Tide Along the Atlantic Coast Beginning through Friday. Tidal Flooding Possible within the St. Johns River Basin Beginning on Friday.

- Much Cooler and Drier Conditions Expected on Friday and Saturday Nights as Winds Diminish at Inland Locations.

An intense shortwave trough diving southeastward across the Carolinas on Thursday night will pivot off the Carolina coast on Friday, resulting in an increasingly negatively tilted long wave trough positioned along the U.S. eastern seaboard that will strengthen surface low pressure off the Mid-Atlantic coast. Meanwhile, strong high pressure building over the Great Lakes region will expand southeastward, keeping a tight local pressure gradient in place locally and driving a cold front southward through the FL peninsula towards Cuba. A few showers over the Atlantic waters may brush the northeast FL coast on Friday morning, mainly for locations from around St. Augustine southward. An unseasonably dry air mass already in place across inland portions of southeast GA will advect across the rest of our area on Friday afternoon and evening, with dewpoints forecast to fall into the 40s across most of interior southeast GA, with values falling into the 50s for locations along the I-10 corridor and the lower 60s south of I-10 by late afternoon. Skies will also clear from northwest to southeast as the day progresses, allowing inland highs to range from around 80 across inland southeast GA to the mid 80s for north central FL. Lingering marine stratocumulus through early afternoon and north-northeasterly winds sustained at 15-20 mph and frequently gusting to 25-30 mph will keep coastal highs in the upper 70s.

The strengthening coastal storm off the Mid-Atlantic coast will nudge northward towards the coastal New England on Friday night and Saturday, allowing our local pressure gradient to gradually loosen. Winds at inland locations will decouple after midnight on Friday night, with radiational cooling dropping lows to the low and mid 50s across inland southeast GA, with values generally falling to the 55- 60 degree range for inland locations in northeast and north central FL, which could approach daily record low temperatures for Sept. 26 (see "Climate" section below for details). Northerly winds will remain sustained at 10-15 mph overnight at coastal locations, which will add an extra chill to the air, but will keep lows in the low to mid 60s.

Dry northwesterly flow will prevail across the southeastern states on Saturday and Saturday night. Our local pressure gradient will continue to gradually loosen, but breezy northeasterly winds will continue at coastal locations on Saturday that will keep highs in the upper 70s to around 80 despite full sunshine. Heights aloft will begin to rise from west to east on Saturday, with a very dry air mass featuring dewpoints in the 40s and 50s again allowing highs to climb to the low and mid 80s inland. Winds will decouple early on Saturday evening at inland locations, and radiational cooling may extend to coastal locations by the predawn hours on Sunday as weakening high pressure shifts over our region. Lows will fall to the 50s at inland locations, ranging to the lower 60s at area beaches.

LONG TERM /SUNDAY THROUGH WEDNESDAY/

Main Highlights This Period:

- Minor Tidal Flooding is Likely Around Times of High Tide within the St. Johns River Basin through Early Next Week.

- Warming Trend Takes Shape Next Week, But an Unseasonably Dry Air Mass Persists Across Our Region Sunday through Monday.

Flow aloft will become zonal across our region on Sunday, with a moisture starved shortwave trough potentially increasing high altitude cloud cover somewhat through Sunday night. An unseasonably dry air mass will otherwise linger through Monday area-wide, with slowly rising heights aloft allowing highs to rebound to the low and mid 80s on Sunday and the mid to upper 80s on Monday. The dry air mass, generally fair skies and weak high pressure over our area will allow for additional nights of radiational cooling on Sunday and Monday, with inland lows falling to the upper 50s and lower 60s on Sunday night, moderating slowly to the low to mid 60s on Monday night. Coastal lows will generally fall to the 65-70 degree range.

High pressure will then shift offshore on Tuesday, allowing for gradually increasing moisture levels from south to north as low level flow becomes southeasterly and flow aloft veers to southwesterly. This weather pattern will allow PWATs to climb back towards the 1.5 inch range, and a few afternoon showers cannot be ruled out, especially across southeast GA as some isentropic lift develops. Widely scattered afternoon showers and possibly a few thunderstorms could develop by midweek as moisture values continue to slowly increase, especially for locations south of the I-10 corridor. Highs will nudge back to the upper 80s to around 90 at inland locations on Tuesday and Wednesday, with onshore winds keeping coastal highs in the mid 80s. Lows will also rebound to the mid and upper 60s inland by Tuesday night, with lower 70s forecast at coastal locations.

AVIATION /06Z THURSDAY THROUGH 06Z FRIDAY/

A mix of VFR and MVFR will continue 12Z as northeasterly elevated onshore flow brings in low level moisture with isolated to widely scattered coastal showers southeast of SGJ over the east central FL coastal waters, though a few quick showers may move onshore through 14Z near SGJ, but dry elsewhere inland. Ceilings will lower to MVFR from as a cold front has moved south of the area terminals with stratus clouds lowering the ceilings to 1.0 kft to 2.0 kft by 09Z and to IFR levels below 1.0 kft at SSI after 11Z, persisting there into midday Thursday. Northerly winds will remain near 10 knots inland and 10-15 knots along the coast with gusts to 20 knots at SSI, SGJ, and CRG through sunrise.

Winds will increase after 12-14Z as strong high pressure ridging builds south along the southeast US coast as the strong pressure gradient and some mixing both lifts ceilings to 2.0-2.5 kft and brings north to northeasterly winds 15-20 knots with gusts to 25-30 knots at SSI and SGJ and near 15 knots gusting to 25 knots at JAX, VQQ, and GNV. Ceilings at SSI will lower to IFR levels near the end of the period as low stratus resettles in from the Atlantic in the onshore flow. Have a Prob30 group for convergent coastal showers intruding at SGJ after 14Z Thursday with VCSH thereafter until 01Z. VFR ceilings expected at GNV after 18Z Thursday as some drier air arrives from the north inland and scatters clouds near 2.5 kft. Winds will decrease to 10-15 knots after 00Z, except at SGJ remaining 15-20 knots with gusts to around 25 knots through 06Z Friday.

MARINE

Low pressure will strengthen well to the northeast of the region through the end of the week, tracking further to the north of the area through the weekend. High pressure will build down the eastern US coastal states Today pushing a backdoor cold front south of the waters. The gradient between the high, and the front trailing from the low to the northeast, will result in enhanced northeasterly winds and waves lasting through at least Friday. A prolonged period of Small Craft conditions will continue through at least Saturday. There is also potential for occasional gusts to near Gale force today into this evening. These conditions ease this weekend as high pressure weakens and the aforementioned low pulls further away from the area.

Rip Currents: There will be several days of strong and dangerous rip currents with as elevated risk through the upcoming weekend. Additionally, strong northeasterly winds will increase breakers to 6-8 feet this afternoon through Friday, increasing the surf danger.

FIRE WEATHER

- ELEVATED NIGHTTIME DISPERSION VALUES AT COASTAL LOCATIONS ON THURSDAY NIGHT...

Scattered showers will be possible for locations along and east of the Interstate 95 corridor through around sunrise on Friday. Otherwise, a drier air mass will gradually overspread our region from Friday through the weekend. Minimum relative humidity values will fall to around 30 percent on Friday afternoon for locations north of Waycross in southeast Georgia, with these lower values then expanding to inland locations throughout our region from Saturday through Monday. Otherwise, gusty north-northeasterly surface and transport winds will counter abundant low cloud cover and low mixing heights today to create fair to good daytime dispersion values. Surface speeds will remain sustained around 20-25 mph at coastal locations through this evening, with frequent gusts of 30-35 mph expected. These gusty conditions will continue overnight tonight for locations east of I-95, creating elevated nighttime dispersion values at coastal locations. Gusty northerly surface and transport winds will continue on Friday area-wide, with decreasing cloud cover and rising mixing heights yielding good daytime dispersion values. Surface and transport winds will then shift to northeasterly on Saturday, with breezy conditions persisting at coastal locations. Fair to good daytime dispersion values are forecast area-wide.

Fog Potential...Significant fog formation is not expected during the next several days.

TIDES/COASTAL FLOODING

Astronomical tides will continue rising through the start of the weekend due to the upcoming Full "Harvest" Moon that occurs on Saturday. Very breezy north northeasterly onshore winds along coastal locations will persist into Friday evening and combine with these increasing astronomical tides to create minor coastal flooding along the Atlantic coast and then into the St. Johns River This evening through at least Saturday. Minor coastal flooding will be possible along the Atlantic coast beginning with this evening's high tide, where water levels of 1.5 - 2 feet above Mean Higher High Water (MHHW) are preliminarily forecast. Minor flooding will then likely expand to the St. Johns River basin by Friday and will then be possible around times of high tide through the weekend and possibly into next week, as rising astronomical tides beyond the date of the Full Moon result in a "trapped tide" situation, keeping water levels elevated, generally at 1-2 feet above MHHW during each tide cycle for most locations within the basin.

CLIMATE

Near record low temperatures are possible at a few of our designated climate sites in northeast and north central FL during the weekend:

Saturday, September 26:

KJAX: 55/1940 KGNV: 57/1975 KCRG: 59/1987

Sunday, September 27:

KJAX: 54/1940 KGNV: 53/1940 KCRG: 57/1982

PRELIMINARY POINT TEMPS/POPS

AMG 77 60 80 52 / 0 0 0 0 SSI 78 64 79 60 / 10 10 0 0 JAX 77 65 80 57 / 10 10 0 0 SGJ 82 70 79 65 / 40 30 20 0 GNV 84 66 83 60 / 0 0 0 0 OCF 87 68 85 61 / 0 0 0 0

JAX WATCHES/WARNINGS/ADVISORIES

FL...High Risk for Rip Currents through late Saturday night for FLZ124- 125-138-233-333. High Surf Advisory from 8 AM this morning to 2 AM EDT Saturday for FLZ124-125-138-233-333. Coastal Flood Advisory from 5 PM this afternoon to 11 AM EDT Friday for FLZ124-125-138-225-233-325-333. GA...High Risk for Rip Currents through late Saturday night for GAZ154- 166. High Surf Advisory from 8 AM this morning to 2 AM EDT Saturday for GAZ154-166. Coastal Flood Advisory from 5 PM this afternoon to 11 AM EDT Friday for GAZ154-166. MARINE...Small Craft Advisory until 2 AM EDT Saturday for AMZ450-470. Small Craft Advisory until 8 AM EDT Saturday for AMZ452-454- 472-474.