Heavy Rain in Florida, March 9, 2025

Area Forecast Discussion
National Weather Service Jacksonville FL
657 AM EDT Sun Mar 9 2025

...New AVIATION...

.SYNOPSIS...
Issued at 515 AM EDT Sun Mar 9 2025

Early morning surface analysis depicts weak low pressure (1009
millibars) moving eastward across coastal Louisiana, with a
frontal boundary extending east of this feature along the northern
Gulf coast and across southeast GA. Meanwhile, high pressure (1022
millibars) was building eastward from the Plains states in the
wake of this storm system. Aloft...stout ridging over the
northwestern Caribbean Sea was in the process of flattening, with
fast westerly flow remaining in place locally downstream of a
potent shortwave trough that was pivoting east-southeastward
across the Arklatex region. Increasingly diffluent flow downstream
of this potent shortwave trough was resulting in an expanding area
of convection across the FL panhandle, with a few showers
developing over southeast GA along a frontal boundary that was
poised to sink southward this morning. Multi-layered cloudiness
was thickening across our area, with lower stratus cloudiness
overspreading all of southeast GA and the Suwannee Valley.
Temperatures and dewpoints were mostly in the 60-65 range area-
wide at 09Z.

&&

.NEAR TERM...
(through Tonight)
Issued at 515 AM EDT Sun Mar 9 2025

Potent shortwave troughing will progress slowly east-southeastward
from the Arklatex region towards the lower Mississippi Valley by
this evening, with this feature then pivoting across the Deep
South late tonight and Monday. A complex weather scenario will
unfold across our area in the near term, leading to the potential
for widespread heavy rainfall and embedded strong to isolated
severe thunderstorms. The frontal boundary advancing southward
across southeast GA will create a surge of northeasterly winds
along coastal locations in southeast GA this morning, with these
gusty onshore winds then spreading southward this afternoon as our
local pressure gradient tightens. Meanwhile, the upstream
shortwave trough will gradually strengthen surface low pressure
that will be gliding eastward along the northern Gulf coast today,
with a low level southwesterly jet (around 25-35 knots at 850
millibars, or around 5,000 feet) lifting northeastward from
Apalachee Bay across the I-10 corridor this morning and into
southeast GA this afternoon. Warm air advection aloft will aid in
the development of elevated convection this morning, with a shield
of heavy downpours quickly overspreading our area during the
predawn and early morning hours. A few embedded stronger storms
could contain hail this morning due to steepening lapse rates and
west-southwesterly bulk shear values of 50-70 knots. Waves of
downpours and embedded elevated convection will persist from areas
south of Waycross and St. Simons Island to the I-10 corridor this
morning, with the southward moving frontal boundary and a
convective cold pool then shifting convection south of I-10 this
afternoon. Rainfall amounts this morning of 1-2 inches will be
possible along the I-10 corridor and for locations south of
Waycross and St. Simons Island, where a Flood Watch has been
issued.

Convection will encounter a warmer environment south of the I-10
corridor early this afternoon, where ML CAPE values will rise to
around 500 j/kg as temperatures rise into the 70s. A few strong
storms will be possible, with downburst winds of 40-55 mph and
small hail possible for locations from Gainesville to St.
Augustine and possibly points southward into north central FL.
Meanwhile, cool air advection and lingering rainfall will keep
highs in the upper 50s and lower 60s for locations north of I-10
today, setting up a rather tight temperature gradient this
afternoon across north central FL. The frontal boundary may push
into north central FL by late afternoon before gradually
strengthening low pressure begins to lift the boundary northward
this evening.

A potent low level jet of 40-50 knots will then infiltrate our
region overnight as low pressure traverses the FL panhandle and
Big Bend coasts, with this feature then moving eastward across
Interstate 10 during the predawn and early morning hours on
Monday. The presence of the lifting frontal boundary and a
strengthening low level jet will keep at least a Marginal (level 1
out of 5) threat for a few embedded severe thunderstorms that will
be capable of producing downburst winds of 45-60 mph and hail. An
isolated tornado cannot be ruled out as helicity values will rise
to the 300-400 range overnight, with instability being the
limiting factor for a larger severe weather outbreak, as ongoing
downpours and dewpoints only rising to the low and mid 60s yield
ML CAPE values to around 500 j/kg for northeast and north central
FL, with this nose of elevated instability extending into coastal
southeast GA by the predawn hours on Monday. Heavy rainfall and
the potential for training downpours will be the bigger story
overnight, as ground conditions will become saturated in the Flood
Watch area this morning, with an additional 2-3 inches expected,
with locally higher amounts possible overnight. The Weather
Prediction Center has thus increased the risk for Excessive
Rainfall to Slight (level 2 out of 4), and the main concern will
continue to be urban and normally flood prone areas. Localized
storm totals of 5-7 inches cannot be ruled out in the Flood Watch
area by noon on Monday.

&&

.SHORT TERM...
(Monday through Tuesday night)
Issued at 515 AM EDT Sun Mar 9 2025

Monday morning the surface low from the Gulf will have made its
way toward the Atlantic coast, dragging the cold frontal boundary
to just off the southeast Georgia coast and across northeast
Florida from the FL/GA line southwestward through the Nature Coast.
A mid level low will provide enough instability to create a
marginal risk (level 1 out of 5) for severe thunderstorms and
excessive rainfall. Expect scattered to numerous showers with some
embedded thunderstorms with most areas receiving another inch or
two of rain as the front pushes through. Wind gusts up to 35-40
mph will be possible, mainly over northeast Florida. High
temperatures will top out in the 60s over southeast Georgia and
northeast Florida's Suwannee Valley, with the rest of Florida
seeing temperatures in the low 70s. Overnight Monday, most of the
rain will have made its way off the Atlantic coast with some
scattered showers lingering over southeast Georgia and along
coastal northeast Florida into the late evening. Overnight lows
will dip into the 40s area wide with some coastal locations
possibly seeing temperatures in the low 50s.

Tuesday, dry high pressure builds in from the Gulf creating sunny
skies and high daytime temperatures in the low to mid 70s area
wide. overnight lows will be in the mid to upper 40s with
temperatures remaining slightly warmer along the coast. Mostly
clear night skies and calm winds will allow for radiational
cooling bringing chances for fog Tuesday night into Wednesday
morning.

&&

.LONG TERM...
(Wednesday through Saturday)
Issued at 515 AM EDT Sun Mar 9 2025

Wednesday will continue with clear sunny skies with temperatures
reaching into the upper 70s to low 80s. An upper level trough will
make its way across the area Thursday increasing cloud coverage
and chances for rain over the area to around 10% with the next
chance for rain occurring at the end of the forecast period.
Daytime highs will bounce between mid 70s to mid 80s with
overnight lows warming into the 50s and 60s.

&&

.AVIATION...
(12Z TAFS)
Issued at 650 AM EDT Sun Mar 9 2025

Showers and storms expected to increase over the next few hours for
JAX, CRG, VQQ, and SSI with vsby and cigs to IFR levels. VLIFR at
SSI currently may transition to LIFR and IFR as convection moves
over the terminal this morning. For GNV and SGJ, a bit later start
to convection, but they will have some periods of IFR vsby and
cigs. For the aftn hours, periods of showers and storms are expected
with low restrictions continuing mostly in the IFR range. There may
a lull in the intensity and coverage of storms roughly 17z to 21z,
but scattered to numerous convection will still exist. Sfc winds
are light but will start turning to the northeast for SSI by 13z/14z
and then for Duval terminals from 14z-16z. SGJ should see a switch
to some onshore flow by about 17z. Another wave of convection
will overspread the regional terminals tonight near and after 22Z,
with embedded heavy downpours and the potential for stronger
thunderstorms on this evening, extending through the overnight and
predawn hours on Monday morning. LIFR to IFR conditions will
prevail for an extended period of time at the regional terminals
tonight and Monday morning.

&&

.MARINE...
Issued at 515 AM EDT Sun Mar 9 2025

A cold front will push southward across the Georgia waters early
this morning, with this front becoming stationary over the
northeast Florida waters late this afternoon. A surge of
northeasterly winds will overspread our local waters from north to
south today, with speeds just below Small Craft Advisory levels
expected across the Georgia waters. Small Craft should Exercise
Caution across the Georgia waters today due to speeds of 15-20
knots, with seas building to 3-5 feet near shore and 4-6 feet
offshore by this afternoon. Seas of 2-4 feet will prevail across
the near shore waters adjacent to northeast FL through tonight,
while seas offshore build to 3-5 feet tonight.

Low pressure moving eastward along the northern Gulf coast today
will slowly strengthen as it approaches the Florida panhandle
and Big Bend coasts tonight, forcing the stalled frontal boundary
to lift northward across the Georgia waters late tonight. Showers
and thunderstorms will overspread our region this morning, with
strong to isolated severe thunderstorms possible across our local
waters after midnight tonight. Strengthening low pressure will
cross our area on Monday morning, with gusty south-southwesterly
winds during the morning, shifting to westerly during the
afternoon and then northwesterly towards sunset. Gale conditions
are possible offshore on Monday night, with winds and seas then
diminishing on Tuesday afternoon and evening as low pressure
accelerates towards Bermuda and weak high pressure builds along
the northern Gulf coast. High pressure will then migrate across
the Florida peninsula on Wednesday, moving offshore by Wednesday
night, with prevailing southerly winds developing locally through
Thursday.

Rip Currents: Strengthening northeasterly winds and building surf
conditions this morning at the southeast GA beaches will result in
a high risk of rip currents today. This northeasterly wind surge
will reach the northeast FL beaches later this morning and will
continue this afternoon, resulting in a higher end moderate risk.
Rough surf conditions will result in a lower end moderate risk at
area beaches on Monday as gusty offshore winds develop.
Diminishing winds and surf conditions should result in a low risk
at area beaches, with a longer period northeasterly swell arriving
towards midweek, which will increase the risk back to moderate.

&&

.HYDROLOGY...
Issued at 515 AM EDT Sun Mar 9 2025

A Flood Watch is in effect tonight along the Interstate 10
corridor in northeast FL and for portions of southeast GA,
generally for locations from Waycross southward. Widespread
rainfall amounts of 3-5 inches are expected in the Flood Watch
area through Monday morning. Localized amounts in excess of 6
inches will be possible for locations where heavier downpours
persist and train repeatedly over the same locations, creating a
potential threat for urban flooding. Rainfall amounts of 2-3
inches are expected for locations north of Waycross in southeast
GA. Totals of one half to one inch are forecast across north
central FL. Water level rises are likely on area rivers such as
the Satilla, St. Marys, Black Creek, Alapaha, Santa Fe, and
Altamaha Rivers are likely during the upcoming week.

&&

.CLIMATE...
Issued at 515 AM EDT Sun Mar 9 2025

Daily rainfall records for March 9th are in jeopardy at Alma, GA
(1.74 inches) and Craig Airport in eastern Duval County (1.98
inches). Daily rainfall records for March 10th are possible at
Jacksonville (1.69 inches) and Craig Airport (1.01 inches). A top
ten 24 hour rainfall total for the month of March is possible at
Jacksonville during this event (would have to be in excess of 3.3
inches).

&&

.PRELIMINARY POINT TEMPS/POPS...
AMG  57  50  63  42 /  90  90  80  20
SSI  60  55  68  48 /  90 100  80  30
JAX  62  57  73  46 /  90  90  80  20
SGJ  67  60  73  49 /  60  80  80  10
GNV  73  63  72  46 /  70  80  70   0
OCF  78  64  71  46 /  50  80  70   0

&&

.JAX WATCHES/WARNINGS/ADVISORIES...
FL...Flood Watch through Monday morning for FLZ021-023-024-030-031-
     033-120-124-125-132-133-220-225-232-322-325-422-425-522.

GA...Flood Watch through Monday morning for GAZ149-162-163-165-166-
     250-264-350-364.

     High Rip Current Risk through late tonight for GAZ154-166.

AM...None.
&&