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

- Coastal and Marine Hazards Continue. Minor Tidal Flooding for St. Johns River Basin through at least Tuesday Night. High Rip Current Risk and High Surf (Northeast FL beaches) through Tuesday. Small Craft Advisories for Our Local Atlantic Waters through Tuesday night

- Locally Heavy Downpours Possible for Coastal Northeast FL Rest of Today

- Isolated TStorm Potential through Thursday Night

NEAR TERM /THROUGH TONIGHT/

Main Highlights:

- Periods of Heavy rainfall and localized Minor Flooding possible for northeast FL through late this evening

- Minor tidal flooding within the St Johns River basin continues

- Rough surf and dangerous rip currents continue

Though mid to upper level forcing is weakening a bit, fairly strong pressure gradient exists which is continuing breezy easterly low level flow. East to northeast surface winds will be up to 15-20 mph with a few gusts of around 30 mph today. Max temps will be held to the 70s most areas, but further inland some areas will reach 80 or lower 80s for a brief time. Plenty of low to mid level moisture and low level convergence to produce scattered to numerous showers across the southern 2/3rds of the area this afternoon and evening. There is some chance of locally heavy rainfall especially for the coastal northeast FL area and maybe as far inland as Highway 301 corridor in northeast FL. Otherwise, limited instability (MLCAPE at or below 700 J/kg) will keep the t-storm chances fairly low at 20 percent or less through mid evening, but the overall rain/shower chances are elevated at about 40-70 percent, highest for east coast of northeast FL, and much lower chance for inland southeast GA at about 15-25 percent. Moving into the tonight period, still elevated rain chances persist for the coastal areas and inland northeast FL, and we are advertising 40-60 percent there and down to 10-20 percent from parts of the Suwannee Valley to Jesup GA to locations northwestward. Heaviest rainfall amounts rest of today through tonight will be over northeast FL, with deterministic amounts of 0.25 to 0.8 inches or so, highest east coast areas. Probabilities of 1-2 inches are fairly low estimated to be 15-25 percent across St Johns, Flagler and Putnam counties.

SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/

Main Highlights This Period:

- High Risk for Rip Currents Continues at Area Beaches through Midweek.

- Isolated Thunderstorms Possible at Inland Locations, Mostly on Wednesday Afternoon and Evening.

- Areas of Locally Dense Fog Possible Late Wednesday Night.

Troughing will shift eastward from our area on Tuesday, allowing narrow ridging to build along the southeastern seaboard. Meanwhile, a deep trough progressing across the Plains states and the Upper Midwest will reach the Great Lakes, Ohio and Tennessee Valleys by Wednesday night as ridging pushes offshore of the southeastern seaboard. Otherwise, strong high pressure situated along the Mid- Atlantic coast tonight will slowly shift offshore on Tuesday, maintaining breezy easterly winds across our area, with winds then shifting to east-southeasterly on Tuesday evening, southeasterly on Wednesday and then southerly towards sunrise on Thursday.

Breezy easterly winds may drive isolated showers onshore along the I- 95 corridor on Tuesday morning, with activity then migrating inland and increasing in coverage slightly across northeast and especially north central FL on Tuesday afternoon. An isolated embedded thunderstorm cannot be ruled out across north central FL on Tuesday afternoon. Breezy onshore winds will keep highs in the mid to upper 70s for locations east of I-95, while rising heights aloft will boost highs to the low and mid 80s for locations west of I-95. Any shower or thunderstorm activity that develops south of I-10 on Tuesday afternoon should dissipate by sunset, with fair skies on Tuesday evening potentially yielding to an increasing cirrus shield from west to east during the predawn and early morning hours on Wednesday. Mild and unseasonably humid conditions should foster low stratus cloud cover to develop at inland locations, with patchy fog possible for locations north of I-10 towards sunrise. Lows will only fall to the mid and upper 60s inland and the lower 70s at coastal locations, where an onshore breeze will continue overnight.

A lengthy cold front associated with the deep trough progressing eastward across the Plains states, Upper Midwest, and Ohio/Tennessee Valleys will enter the southeastern states by Wednesday evening. Ridging aloft over our area will shift offshore by late afternoon, allowing low and mid level flow to veer locally, and PWATs will climb to the 1.5 - 1.75 inch range for locations west of I-95. Southeasterly low level winds will drive the Atlantic sea breeze quickly onshore on Wednesday afternoon, with this boundary potentially colliding with the Gulf sea breeze boundary near I-75 in the Suwannee Valley and north central FL during the late afternoon hours. This warm, moist, and increasingly unstable environment should produce scattered showers and isolated embedded thunderstorms for areas west of I-95 on Wednesday afternoon and evening, while coastal locations remain mostly dry through Wednesday night. Onshore winds should again keep coastal highs in the upper 70s to around 80, while inland locations solidly climb to the mid 80s. Low level flow will then weaken on Wednesday night as the frontal boundary slows its forward progress upon approach to our region. Fog and low stratus cloud cover should be more widespread during the overnight hours into early Thursday morning, with dense fog possible, likely dependent on the thickness of mid and higher altitude cloud cover associated with the approaching trough and cold front. Lows will again only fall to the 65-70 range inland and the lower 70s at coastal locations.

LONG TERM /THURSDAY THROUGH MONDAY/

Main Highlights This Period:

- Warm and Unseasonably Humid Weather Continues through at Least Thursday Night.

- Isolated Afternoon Thunderstorms Possible on Thursday and Friday.

- Slightly Cooler and Drier Conditions Expected this Weekend.

- Strong Cold Front Possibly Approaches Our Area on Sunday Night.

Troughing aloft progressing into the southeastern states towards midweek will get deflected northeastward by a ridge that will briefly build over the Gulf on Thursday. This weather pattern will result in a cold front slowing its forward progress and weakening as it moves across our area late this week. However, a southern stream trough that will move onshore across central and northern California on Tuesday will progress quickly eastward during the remainder of this work week, reaching the southeastern states on Friday. This system will flatten the ridge across the Gulf this weekend, creating fast zonal flow across our area in advance of a deeper northern stream trough that is poised to dig quickly southeastward from the northern Plains this weekend, with this trough likely pushing a stronger cold front across our area by Sunday night and next Monday.

The initial frontal boundary that will be slowing its forward progress across the FL panhandle on Wednesday night will limp through our area on Thursday night and Friday morning, with a warm and unseasonably humid air mass continuing through Thursday evening locally ahead of this boundary. Highs soaring to the mid 80s again on Thursday and PWATs remaining above 1.5 inches should allow for isolated to widely scattered convection to develop during the afternoon hours, with southwesterly low level steering flow potentially allowing for a sea breeze collision near or east of the U.S. Highway 301 corridor. Activity should largely remain diurnal in nature, with fog and low stratus cloud cover possibly developing ahead of the decaying front during the predawn and early morning hours on Friday, especially across northeast and north central FL and possibly coastal southeast GA as well. Lows on Thursday night will likely remain in the 60s area-wide, possibly around 70 for portions of coastal northeast FL.

Longer term model guidance begins to diverge on Friday as the decaying front potentially lingers over our area. Model blends keep only isolated diurnal convection along the I-95 and U.S. Highway 341 corridors at this time, but the latest 12Z operational GFS indicates a wetter scenario into Friday evening as the aforementioned southern stream trough quickly reaches the southeastern U.S. Highs will likely climb to at least the lower 80s again for much of our area, with a slightly cooler and drier air mass then advecting across our region beginning late Friday night and through the upcoming weekend, as highs generally remain in the mid to upper 70s, with lows falling to the 50s at most inland locations on Friday night and then area- wide by Saturday night. The approaching strong upper trough and cold front may advect enough moisture off the Gulf on Sunday night for at least isolated showers to develop across our area.

AVIATION /18Z MONDAY THROUGH 18Z TUESDAY/

A mix of flight conditions over the area with periods of MVFR and brief IFR cig/vsby for the northeast FL TAFs due to showers and isolated tstorms, but likely prevailing just above VFR cigs at around 3500-5000 ft this afternoon and evening. Gradual improvement in the chance of showers and storms by mid to late evening, but not completely done with showers coming in off the Atlantic so have VCSH or a PROB30 group after 02z. The PROB30 group for late evening is noted for SSI and SGJ, but may also be needed at some point for CRG. Toward early morning on Tuesday, some potential for lower cigs for inland TAFs at VQQ and GNV down to IFR. Mainly isolated showers expected for Tuesday for first half of the day with VCSH denoted in the TAFs. For sfc winds, east to northeast winds around 10-15 kts with gusts around 20 kts and continue through around 23z. A coastal trough in place will back winds NNE overnight with speeds falling to 5-10 knots.

MARINE

Strong high pressure wedged along the coast will continue elevated seas and small craft advisory conditions through Tuesday. Though winds will begin to decrease Tonight, lingering elevated seas will remain through Tuesday night. High pressure will remain to the north but with a weaker influence through the second half of the week resulting in lighter winds and lowering seas. Bouts of showers and heavy downpours will be possible through the middle of the week, especially for the rest of today through Tuesday as coastal troughing develops. A cold front will approach from the west Wednesday and pass across the local waters Friday.

Rip Currents / High Surf:

Dangerous surf zone conditions continue with a High rip current risk at all area beaches rest of today and elevated to high surf for the entire coast. The highest breakers, around 5-7 feet will be from Ponte Vedra south through late evening. Improving surf zone conditions are expected late this week.

FIRE WEATHER

- Elevated nighttime dispersion values tonight for coastal northeast FL

Scattered showers and isolated thunderstorms will be possible across our region through Thursday night. A few heavier downpours will be possible through this evening for coastal northeast Florida. Otherwise, breezy northeasterly surface and transport winds this afternoon and tonight will shift to easterly on Tuesday morning and then southeasterly by Wednesday and Wednesday night. Breezy speeds at coastal locations through late this evening will create elevated nighttime dispersion values for coastal northeast FL tonight. Fair to good daytime dispersion values will continue through Wednesday throughout our region. Surface and transport winds will gradually diminish on Wednesday night and will shift to southerly by early Thursday morning. Surface and transport winds will then shift to southwesterly on Thursday afternoon, with onshore surface winds developing along the I-95 corridor. Lighter speeds will yield fair daytime dispersion values at inland locations on Thursday afternoon, with poor values forecast at coastal locations.

FOG POTENTIAL AND OTHER WEATHER REMARKS: Patchy to areas of fog formation are possible for inland locations along and north of the Interstate 10 corridor. Areas to widespread fog will be possible during the predawn and early morning hours on Thursday across our area.

TIDES/COASTAL FLOODING

Due to the persistent onshore wind, tidal levels within the St Johns River basin and it's tributaries have remained steady, reaching minor flood levels at high tides over the last 24 hours. Recent peak water levels in this area have been roughly 1.55 to 1.85 feet MHHW. This is likely to continue through Tuesday night before decreasing Wednesday onward as winds diminish. Water levels are likely to remain in the 1.5-2.0 feet MHHW (mean higher high water) range until midweek. A Coastal Flood Advisory remains in effect for the entire middle and lower St Johns River zones. One caveat is that the additional recent rainfall over central FL may allow elevated water levels to linger in the St Johns river basin late this week from Satsuma northward Mayport.

PRELIMINARY POINT TEMPS/POPS

AMG 65 82 66 84 / 10 10 0 40 SSI 67 78 67 78 / 40 20 10 10 JAX 67 80 67 82 / 40 20 10 20 SGJ 70 79 71 79 / 50 10 0 10 GNV 68 83 68 85 / 40 20 10 50 OCF 69 84 68 85 / 30 40 10 50

JAX WATCHES/WARNINGS/ADVISORIES

FL...Coastal Flood Advisory until 4 AM EST Wednesday for FLZ038-125- 132-137-225-325-633. High Risk for Rip Currents through late Tuesday night for FLZ124- 125-138-233-333. High Surf Advisory until midnight EST tonight for FLZ138-233- 333. GA...High Risk for Rip Currents through late Tuesday night for GAZ154- 166. MARINE...Small Craft Advisory until 11 PM EST Tuesday for AMZ452-454. Small Craft Advisory until 4 AM EST Wednesday for AMZ470-472- 474.