Severe Thunderstorm Warning 125, NWS Tallahassee, FL

Area Forecast Discussion
National Weather Service Tallahassee FL
319 PM EDT Tue Apr 4 2017

.NEAR TERM [Tonight Through Wednesday]...

***Key Points***

SPC Outlook: The Storm Prediction Center has all but the Valdosta
region, a small portion of the Florida Panhandle, and most of the
Florida Big Bend outlooked in a Moderate Risk for Wednesday. The
remainder of the Tri-state region is outlooked for either enhanced
or for a slight risk.

Current Timing: The latest model guidance suggests that most
thunderstorms will develop after daybreak with initial development
likely over our western zones by mid to late morning with the
main threat in the afternoon in the moderate risk area. Conditions
are expected to clear late Wednesday night.

Threats: Current parameters suggest that all modes of severe
weather will be possible. Some strong (EF2+), long tracked
tornadoes are not out of the question. Destructive wind gusts of
70 mph, large hail the size of golf balls or larger will also be
possible. Additionally, high surf is expected along the Florida
Gulf Coast, with life threatening rip currents.

***Forecast Discussion***

The stalled front across the northern gulf this afternoon will lift
north tonight as a warm front in response to a developing low
pressure system ejecting eastward from the southern Plains. There
will be scattered showers and thunderstorms accompanying the front
but QPF is expected to be low. Overnight min temps will generally be
in the upper 60s.

On Wednesday we are looking at a very active day with the surface
and upper level low deepening as they translate across the Missouri
Valley and into the Midwest. The southward trailing cold front will
approach our westernmost zones toward evening. This will be a very
dynamic system with operational and hi-res models showing several
parameters working together to bring a significant organized
severe weather event for our entire CWA. Latest guidance indicates
Mean CAPE 2000-3000 J/KG, 50+ Kts of bulk shear, mid-level lapse
rates ~ 7.5 C and impressive updraft velocities. The ECAM is also
showing several long updraft helicity tracks, especially across SE
AL and our northern GA zones. Convection is expected to increase
in coverage after daybreak Wednesday, with the vigorous storm
initiation expected to the west and northwest of the CWA. These
storms will move eastward into the CWA during the mid to late
morning hours and continue into the evening across our easternmost
zones.

.SHORT TERM [Wednesday Night Through Thursday Night]...

A residual severe weather threat may continue into effect
Wednesday night. Thunderstorms with the potential for large hail
and damaging winds cannot be ruled out. The cold front will
continue to move eastward and be out of the region by Thursday
morning. Behind the front, high pressure begins to build into the
area. A dry, cool airmass will move in lowering temperatures
throughout the region. Highs will be in the upper 60s and lows in
the 40s.

.LONG TERM [Friday Through Tuesday]...

Surface high pressure will dominate most of the long term allowing
for quieter weather throughout the region. The dry, cool airmass
will also remain in place. Late in the period, upper level ridging
is expected to keep the next potential frontal passage at bay
further keeping the region dry. Cooler temps begin a warming trend
on Sunday with highs rising into the low 80s and lows rising into
the upper 50s.

&&

.AVIATION [Through 18Z Wednesday]...

MVFR/IFR conditions are expected to redevelop overnight in the
moist environment. An isolated shower or TSTM is also possible as
a warm front lifts across the area. VFR returns after daybreak but
the threat of thunderstorms, some severe, will increase as we
move into the late morning for DHN and afternoon for the remaining
TAF sites. Southerly winds will be breezy on Wednesday even
outside of areas of convection.

&&

.MARINE...

Calmer conditions are expected across coastal waters today.
However, winds and seas will increase late tonight ahead of another
powerful storm system, reaching advisory levels Wednesday morning.
Expect advisory level conditions to last through at least Friday,
with elevated winds and seas persisting into the weekend before
calming. Severe storms are expected across coastal waters during the
day Wednesday. High winds, hail and waterspouts will be possible
with this activity.

&&

.FIRE WEATHER...

Rain chances will be elevated Wednesday as storms move in. Dry air
will move into the region on Thursday and will remain in place for a
few days. The lowest RH values will be on Saturday and Sunday. High
dispersion indices are expected Wednesday and Thursday afternoons.

&&

.HYDROLOGY...

Significant heavy rainfall over the past 24 hours was located to
coastal areas of the Florida Big Bend with the heaviest amounts
across Eastern Taylor and into Lafayette County where up to 12
inches of rain fell overnight. Some of the faster responding rivers
have been rising quickly this afternoon, notably the Sopchoppy
River and Steinhatchee River

There is some potential for the Steinhatchee River to reach flood
stage by early Thursday morning, however much of the heaviest rain
fell just north of the river basin.

The next event is expected to only produce 1-2 inches of rain with
isolated heavier totals. Given that the bulk of the heaviest rain
was near the coast, the overall river flood threat remains low for
the larger-stem river systems.

&&

.PRELIMINARY POINT TEMPS/POPS...

Tallahassee   68  81  57  71  46 /  30  50  50  10   0
Panama City   69  78  60  69  52 /  30  70  30   0   0
Dothan        67  80  53  66  45 /  30  70  40   0   0
Albany        67  81  54  66  45 /  30  80  60  10   0
Valdosta      68  84  57  68  46 /  20  40  60  10   0
Cross City    67  84  60  71  47 /  30  20  60  10   0
Apalachicola  71  78  61  70  52 /  20  40  40   0   0

&&

.TAE WATCHES/WARNINGS/ADVISORIES...

FL...High Rip Current Risk until 7 PM EDT /6 PM CDT/ this evening for
     Coastal Bay-Coastal Gulf-South Walton.

GA...None.
AL...None.
GM...None.

&&

NEAR TERM...Barry
SHORT TERM...Barry/CHANEY
LONG TERM...Barry/CHANEY
AVIATION...Barry
MARINE...Barry
FIRE WEATHER...McDermott
HYDROLOGY...Godsey

Special Weather Statement
National Weather Service Tallahassee FL
647 PM EDT TUE APR 4 2017

FLZ014-015-114-115-042330-
Inland Franklin FL-Inland Gulf FL-Coastal Franklin FL-
Coastal Gulf FL-
647 PM EDT TUE APR 4 2017

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHERN GULF AND WEST CENTRAL
FRANKLIN COUNTIES UNTIL 730 PM EDT/630 PM CDT/...

At 646 PM EDT/546 PM CDT/, National Weather Service doppler radar
indicated a a strong thunderstorm 11 miles southwest of Port St. Joe,
moving northeast at 35 mph.

Nickel size hail and winds in excess of 40 mph will be possible with
this storm.

Locations impacted include...
Port St. Joe, Apalachicola, Nine Mile, Highland View, Eleven Mile, St
Joseph State Park, Thirteen Mile, Odena, Cape San Blas, Indian Pass,
Tilton, Jones Homestead, Ward Ridge, Milltown, Bay City, Howard
Creek, Apalachicola Airport, Simmons Bayou, Beacon Hill and Dalkeith.

LAT...LON 2973 8548 2988 8549 3005 8514 2987 8504
      2985 8503 2983 8503 2983 8501 2972 8495
      2960 8529 2959 8537
TIME...MOT...LOC 2246Z 238DEG 30KT 2968 8542

04-MCDERMOTT