Severe Thunderstorm Warning 449, NWS Birmingham, AL

Area Forecast Discussion
National Weather Service Birmingham AL
1105 PM CST Sat Dec 9 2023

...New AVIATION...

.MESOSCALE UPDATE FOR SEVERE WEATHER THREAT OVERNIGHT...
Issued at 858 PM CST SAT DEC 9 2023

The threat for severe storms and tornadoes continues overnight for
all of Central Alabama. Currently, a line of strong to severe
storms stretches from Chattanooga to Cullman to Columbus MS. Ahead
of the line, a couple clusters of storms have developed, including one
near Demopolis. Counties across the west and far northeast remain
in tornado watches.

Currently, dewpoints are in the 60s areawide, with temperatures in
the mid 60s to lower 70s for much of the area. Looking at the 00Z
ROAB from BMX, surface based CAPE was around 1100J/kg with 45kts
of 0-6km shear. Little to no cap was noted on the sounding.
Current meso analysis shows surface CAPES from 500 to 1000 J/kg
with bulk shear values of 45-55kts ahead of the line. Do not see
much change in airmass over the next few hours, and expect the
Tornado watch to be expanded eastward.

Looking closer to sunrise,the latest CAM guidances shows a surge
of moisture into the southeast after 3AM with a restrengthening
low level jet. This would maintain the severe threat through the
early morning hours across the southeastern counties.

14

&&

.SHORT TERM...
(This afternoon through Sunday)
Issued at 1254 PM CST SAT DEC 9 2023

All eyes are on convection developing off to our north and west as
a dynamic system dives toward the Southeast states. Looking at
mesoscale conditions, it appears the break in the activity
advertised yesterday is in fact materializing. We're certainly
realizing more surface-based instability than was being
advertised at this point yesterday. Breaks in the clouds are being
observed across much of western and southwestern Alabama as of
midday, with cloud streets visible across southern Mississippi and
southwestern Alabama. Current SBCAPE values based on RAP analysis
are being analyzed at 1500 J/kg within these locations.
Temperatures have already risen into the 70s at Tuscaloosa and
Demopolis, with the record high of 76 at Tuscaloosa at risk of
being broken. As 0-6km bulk shear values increase close to 50
knots late this afternoon and into this evening, we'll have to
closely watch for convective development in central and southern
Mississippi that will move into western Alabama between 4pm and
6pm. Due to higher instability values, cores will likely form
within any discrete cell that is able to develop, with 500mb
temperatures between -14C and -16C. Therefore, we've added large
hail as a potential threat, especially for locations within the
Slight Risk area. Locations included are roughly along and
northwest of the I-59 corridor especially between 6pm and 10pm
tonight. Although mostly unidirectional deep-layer flow is still
expected as the cold front moves across Central Alabama overnight
tonight, SRH values will remain high enough to favor rotating
updrafts.

We'll continue to watch for discrete cell formation out ahead of
what will become the main convective line/QLCS that forms across
central and northern Mississippi later this afternoon. All types
of severe weather will be possible across the far western and
northwestern counties through this evening, while a damaging wind
and tornado threat will continue as the QLCS moves southeastward
through Central Alabama overnight. Severe storm chances should end
between 8 and 10am in the far southeastern counties Sunday morning
with much colder and drier air advecting into the state. Most
locations will see temperatures actually fall through the day with
very cold northwesterly winds between 15 and 20mph. Temperatures
shouldn't make it out of the 40s for many locations across the
north and northwest counties Sunday afternoon.

56/GDG

&&

.LONG TERM...
(Sunday night through next Friday)
Issued at 207 PM CST SAT DEC 9 2023

No significant changes to the extended forecast.

58/rose

Previous long-term discussion:
(Sunday night through next Friday)
Issued at 253 AM CST SAT DEC 9 2023

Quieter weather expected next week as high pressure builds in across
the Southeastern CONUS under generally zonal flow aloft. Morning
lows Monday and Tuesday mornings will be in the upper 20s to near 30
for much of the area. We'll then see a gradual warm-up Wednesday
through Friday. There could be increasing rain chances on Friday,
but model guidance is highly variable on the evolution of the next
system. Therefore, we'll keep low-end rain chances in the forecast
for now.

25/Owen

&&

.AVIATION...
(06Z TAFS)
Issued at 1105 PM CST SAT DEC 9 2023

Line of showers and storms are now push through the north and
west. As of 5z the line was at TCL and BHM and will impact the
rest of the north through 9 to 10z. Left over periods of rain
will then impact the area through 18 to 20z along with MVFR
conditions. MGM and TOI see the line of showers and storms begin
between 10 and 11z with the left over periods of rain through 23
to 00z. Winds will be switching from the SW to NW as the line goes
through the area. Winds later this morning and through the
afternoon will be 10 to 15 kts with higher gusts.

16

&&

.FIRE WEATHER...

Showers and thunderstorms will overspread all of Central Alabama
tonight. 20-foot winds will be from the south-southwest at 8-12
mph through the evening hours. A strong cold front will track
southeast across the area after midnight, producing gusty
northwest winds. Min RHs on Sunday will be 55-65% west of I-65 and
65-75% east of I-65. The rain will end across west Alabama by the
early afternoon hours on Sunday and across east Alabama by sunset
Sunday.

&&

.PRELIMINARY POINT TEMPS/POPS...
Gadsden     49  50  25  51 / 100  70   0   0
Anniston    52  54  27  51 / 100  80   0   0
Birmingham  49  51  29  51 /  90  70   0   0
Tuscaloosa  49  50  29  54 / 100  60   0   0
Calera      51  52  28  52 / 100  70   0   0
Auburn      58  60  30  51 /  90  90  10   0
Montgomery  57  60  31  53 / 100  80   0   0
Troy        60  62  31  54 /  90  90  10   0

&&

.BMX WATCHES/WARNINGS/ADVISORIES...
None.
&&

SHORT TERM...14
LONG TERM....58
AVIATION...16

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Preliminary Local Storm Report
National Weather Service Birmingham AL
1224 AM CST Sun Dec 10 2023

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1207 AM     Tstm Wnd Dmg     2 NNW Hoover            33.43N 86.82W
12/10/2023                   Jefferson          AL   Public

            Trees down at several locations in the
            Vestavia Hills, Bluff Park area.

&&

GMS

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