Flash Flooding and Damaging Wind in Alabama, June 19 to 20, 2021

Area Forecast Discussion
National Weather Service Birmingham AL
357 PM CDT Sat Jun 19 2021

.SHORT TERM...
/Updated at 0213 PM CDT Sat Jun 19 2021/

Through This Evening.

Tropical Storm Claudette is centered southwest of Demopolis in
Marengo County with gusty winds at times from Meridian east to
Selma and south into Interior Southwest Alabama. Expect breezy
winds within 30 to 50 miles of the circulation center.

Thankfully, most of the forecast area has remained fairly stable
and that has kept thunderstorm activity very limited. We will,
however, continue to monitor our southeast counties, generally
areas along and southeast of Interstate 85, as this area continues
to have the best potential for strong winds and a few tornadoes
over the rest of the afternoon. Low-level instability values are
expected to decrease overnight, reducing the risk later this
evening into the overnight hours.

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/Updated at 0330 PM CDT Sat Jun 19 2021/

Tonight and Tomorrow.

Tropical Depression Claudette will move northeastward tonight,
with its center of circulation tracking along the I-59 corridor.
Expect moderate to heavy rainfall to continue across portions of
the north and east, where an additional 1-2 inches is possible.
Will need to watch locations closer to the Georgia state line,
where 2-3 inches, with locally higher amounts are possible. Drier
air has worked around the southern side of Claudette, limiting
rain activity across our southwest. The Flash Flood Watch will be
allowed to expire at 4PM for the southwestern counties.

Model guidance indicates a limited amount of instability but
enhanced wind shear across the southeast through the evening and
into the overnight period. For that reason, cannot rule out an
isolated tornado, and will leave the marginal threat for tornadoes
near and south of I-85 through at least 10pm tonight.

Tomorrow, Claudette's circulation will move into Georgia, with
ridging building in her wake. This will limit the amount of rain
for much of the area. Will leave likely pops across the east
tomorrow morning, for any convergent areas lingering on the
southern side of Claudette. There is a chance of scattered showers
during the afternoon, as moisture remains high across the area.
Highs tomorrow will warm into lower 80s east to around 90 degrees
west. This will push heat indices toward 100 degrees in the west.

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.LONG TERM...
/Updated at 0322 PM CDT Sat Jun 19 2021/

Did not many changes to the extended this afternoon. Pattern
remains active and wet through mid week, with moisture lingering
behind the exiting tropical system and an approaching trough/front.

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Previous long-term discussion:
/Updated at 0354 AM CDT Sat Jun 19 2021/

Monday through Friday

Plentiful Gulf moisture will linger across the Deep South in the
wake of the exiting tropical system as we head into the next work
week. This is primarily the result of a subtropical ridge positioned
to our east which will promote a broad region of southerly to
southwesterly low-level flow across the Gulf Coast region northward
into the TN Valley. With the muggy airmass and sufficient diurnal
heating, an expectation of scattered to numerous showers and
thunderstorms would be reasonable. PoPs were kept in the 55-70%
range as a result. Meanwhile a longwave trough is progged to advance
from the Central and Northern Plains toward the Great Lakes and OH
Valley. This will continue eastward into Tuesday morning. The
surface low is forecast to quickly propagate northeastward from the
Great Lakes into Quebec. However, the associated surface front will
stretch all the way from Quebec to the Big Bend. This frontal
boundary will approach our area Tuesday morning. Rather than show
a diurnal decrease in PoPs overnight, I had to keep rain chances
quite elevated as this feature nears the area. Widespread rain
chances will move from northwest to southeast throughout the day
on Tuesday as the front moves across Central AL. Medium-range
guidance suggests a low-amplitude deep-layer ridge settling across
the Southern Plains mid week. Somewhat drier air will remain
across our area but moisture could slowly recover each day toward
the weekend as a result of weak southerly flow. Despite weak flow
aloft, this will foster the usual afternoon rain chances (20-30%
PoPs) as warm humid conditions prevail toward next weekend.

40/Sizemore

&&

.AVIATION...
18Z TAF Discussion.

Rainfall associated with Tropical Storm Claudette continues to
rotate across the area. Most persistent and heavy rainfall is
currently across the north and east, with mainly scattered
activity across the southwest portion of the area. While
widespread rainfall will continue to move to the north and east,
expect continued shower development across the area as Claudette
moves through the region, which will leave rain chances in the
forecast through the period.

Main aviation concerns are low cigs and vis. Cigs will lower
through the afternoon, to IFR, and remain low overnight. Within
heavier showers, vis will drop to 2 miles or less. Wind gusts up
to 25kts are possible, mainly through sunset today due to the
tightened pressure gradient associated with the tropical system.

Conditions improve somewhat Sunday, with cigs improving to
VFR/MVFR and winds becoming westerly.

Note: AMD NOT SKED until further notice at KASN due to ongoing
equipment issues.

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&&

.FIRE WEATHER...

Widespread soaking rains are expected across Central Alabama
through tonight due to a tropical system. Locally heavy rainfall
is possible mainly across eastern locations overnight. Low
ceilings and fog will be possible early Sunday. High moisture
content remains across the area after this system departs to the
east as surface and transport winds remain southwesterly at 5-10
mph through Monday evening. A frontal boundary is expected to pass
across the area on Tuesday which will bring another period of
widespread rain chances.

&&

.PRELIMINARY POINT TEMPS/POPS...
Gadsden     67  87  70  86  68 /  80  50  20  70  90
Anniston    69  85  72  85  71 /  90  50  20  70  80
Birmingham  69  87  73  85  70 /  80  50  20  70  90
Tuscaloosa  69  88  73  87  70 /  70  40  10  70  90
Calera      70  86  72  85  71 /  90  50  20  70  80
Auburn      70  84  72  85  71 /  90  60  30  60  60
Montgomery  72  88  73  88  72 /  80  60  20  70  70
Troy        72  87  73  86  72 /  80  60  20  70  60

&&

.BMX WATCHES/WARNINGS/ADVISORIES/...
Flash Flood Watch through Sunday evening for the following
counties: Autauga...Barbour...Bibb...Bullock...Calhoun...
Chambers...Chilton...Clay...Cleburne...Coosa...Elmore...
Jefferson...Lee...Lowndes...Macon...Montgomery...Pike...
Randolph...Russell...Shelby...St. Clair...Talladega...
Tallapoosa...Tuscaloosa.

Flash Flood Watch until 4 PM CDT this afternoon for the
following counties: Dallas...Greene...Hale...Marengo...Perry...
Sumter.

&&

Hazardous Weather Outlook
National Weather Service Birmingham AL
416 PM CDT Sat Jun 19 2021

ALZ011>015-017>050-210030-
Marion-Lamar-Fayette-Winston-Walker-Blount-Etowah-Calhoun-Cherokee-
Cleburne-Pickens-Tuscaloosa-Jefferson-Shelby-St. Clair-Talladega-
Clay-Randolph-Sumter-Greene-Hale-Perry-Bibb-Chilton-Coosa-Tallapoosa-
Chambers-Marengo-Dallas-Autauga-Lowndes-Elmore-Montgomery-Macon-
Bullock-Lee-Russell-Pike-Barbour-
416 PM CDT Sat Jun 19 2021

This Hazardous Weather Outlook is for the counties served by the
National Weather Service office in Birmingham.

.DAY ONE...Outlook through Tonight.

There is a risk of localized flooding along and south of Interstate
20 along and along and east of Tuscaloosa County as a tropical system
moves across the region.

There is also a low risk for tornadoes into this evening hours
associated with an inland tropical system. The threat area is
generally along and south of Interstate 85.

.DAYS TWO THROUGH SEVEN...Sunday through Friday.

There is a low risk for localized flooding along and south of
Interstate 20 and along and east of Tuscaloosa County on Sunday as
the remnants of a tropical system moves out of the area.

.SPOTTER INFORMATION STATEMENT...

Activation of storm spotters and emergency management may be needed
today through Sunday.

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