Special Weather Statement, NWS Birmingham, AL

Area Forecast Discussion
National Weather Service Birmingham AL
357 AM CDT Mon Mar 23 2020

.SHORT TERM...
/Updated at 0353 AM CDT Mon Mar 23 2020/

Today through Tuesday.

An ill-defined surface front and temperature gradient, which has
been present for the last couple of days, continues to linger across
the Deep South. A low-amplitude shortwave moving through the Ohio
Valley this morning is providing a lifting mechanism for elevated
showers and thunderstorms across northern Mississippi and
northwestern Alabama. This activity will move eastward and mostly
affect locations near and north of Interstate 20 through noon.
Though the bulk of the rain should be confined to the morning hours
as the shortwave moves into the Mid-Atlantic Region by early
afternoon. However, rain chances should increase south of I-20 for
the afternoon as the effective front continues to move slowly
southward. A few afternoon thunderstorms may develop with the help
of daytime heating.

A quick transition is expected to occur tonight as a stronger low-
amplitude shortwave moves across Oklahoma, leading to cyclogenesis
and pressure falls along the I-40 corridor. The effective front
across Alabama should return northward as a warm front on Tuesday
morning. Some showers may accompany this transition as the warm
sector surges northward, with warm temperatures expected Tuesday
afternoon. As the front approaches our northwestern counties,
moisture quality and instability could be sufficient for some
stronger storms and perhaps a couple of severe storms within a
strengthening low-level jet axis. The threat for isolated damaging
winds and quarter size hail should be confined to our northern
counties beginning around 4 PM.

87/Grantham

.LONG TERM...
/Updated at 0353 AM CDT Mon Mar 23 2020/

Tuesday night through Sunday.

A broad shortwave trough will be situated over the Ohio Valley
Tuesday night producing unsettled weather across the region and a
chance for strong to severe storms, as detailed in the short term
discussion above. Meanwhile, a 1004mb surface low is progged to
track from Tennessee towards the Mid Atlantic early Wednesday
morning while an associated cold front reaches our northwest and
passes through the state during the day.

Initially, the threat for pre-frontal strong to severe storms will
continue at the start of this period for areas generally north of a
line from Anniston to Tuscaloosa. Although available instability
(SBCAPE ~500-1000 J/kg) will quickly decrease after dark, there will
remain a brief window through at least 10PM where strong deep-layer
shear will provide some support for updraft organization.
Uncertainties still remain, such as weak forcing along the pre-
frontal convective line, a pocket of dry/warmer air around 700mb
which may weakly cap any thunderstorm development, and the rapid
eastward exit of favorable dynamics. These factors continue to limit
the overall threat, so will stay with a low-confidence Marginal Risk
for now. Better mesoscale details will be resolved in following
updates.

A few days of dry and anomalously warm weather will develop across
the Southeast by midweek as a highly amplified ridge builds over the
Gulf of Mexico and produces strong height rises and subsident
conditions Wednesday through Friday. I removed any mentionable PoPs
for these days and continued to lean on the warmest guidance for
temperatures with Thursday and Friday appearing to be the two warmest
days. Area-wide highs in the 80s are expected and potentially a
few readings in the low 90s which would break some daily high
records if this were to occur.

An upper-level low ejects across the upper Plains on Friday and
drives another front into the region this weekend while the ridge
to our south shifts to the Western Atlantic. There are some
signals for the potential of strong storms with this system, but
there is way too much uncertainty, temporally and spatially,
between guidance to mention anything above 40 to 50 percent PoPs
at this point. Will continue to monitor this system and make
forecast adjustments as necessary as models come in to better
agreement over time.

86

&&

.AVIATION...
06Z TAF Discussion.

Subsidence behind a departing upper wave broke up the cloud cover
early this evening. The clouds have just begun to redevelop over
Central Alabama. The main trend of the previous forecast remains
intact. A warm front was located just south of Central Alabama.
Warm air advection over the top of this boundary will produce
cloud cover and ceilings into MVFR by 09z or so. Additionally, the
rain and embedded thunderstorms developing Mississippi should
expand and move into areas near the terminals before 12z. Rain,
possible thunder, reduced vis and ceilings will rule the northern
sites through late afternoon. Southern sites may see some
improvement after 18z as the warm front moves northward.

75

&&

.FIRE WEATHER...

Low clouds and high humidity values will continue through Tuesday
morning for many locations. Showers and storms are expected across
the northern half of the area today. Tuesday appears warm and
breezy with southerly winds ahead of an approaching front which
will bring more showers and storms. Wednesday through Friday
should be dry and warm with RH values above critical values.

&&

.PRELIMINARY POINT TEMPS/POPS...
Gadsden     69  56  78  60  75 /  90  30  80 100  10
Anniston    69  59  78  62  77 /  80  30  60  90  10
Birmingham  69  60  79  64  78 /  90  30  70  90  10
Tuscaloosa  71  61  82  64  80 /  80  20  50  90   0
Calera      70  61  80  64  79 /  80  20  40  90  10
Auburn      73  62  79  64  79 /  60  40  20  70  10
Montgomery  78  64  84  65  83 /  50  40  20  60  10
Troy        80  63  83  65  84 /  40  40  10  40  10

&&

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

&&

Hazardous Weather Outlook
National Weather Service Birmingham AL
347 AM CDT Mon Mar 23 2020

ALZ011>015-017>050-241200-
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-
347 AM CDT Mon Mar 23 2020

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

.DAY ONE...Today and Tonight.

No hazardous weather is expected at this time.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday.

A few severe storms are possible from 4 PM until 10 PM on Tuesday.
The strongest storms will be capable of producing damaging winds up
to 60 miles per hour and quarter sized hail. It appears that the
threats will be limited to areas north of a line from Tuscaloosa to
Birmingham to Anniston.

.SPOTTER INFORMATION STATEMENT...

Activation of storm spotters and emergency management may be needed
Tuesday afternoon and evening.

Special Weather Statement
National Weather Service Birmingham AL
420 AM CDT Mon Mar 23 2020

ALZ012-013-230945-
Fayette AL-Lamar AL-
420 AM CDT Mon Mar 23 2020

...SIGNIFICANT WEATHER ADVISORY FOR NORTHWESTERN FAYETTE AND CENTRAL
LAMAR COUNTIES UNTIL 445 AM CDT...

At 419 AM CDT, Doppler radar was tracking a strong thunderstorm over
Bedford, or near Vernon, moving east at 35 mph.

Pea size hail and winds up to 40 mph will be possible with this
storm.

Locations impacted include...
Vernon, Sulligent, Belk, Beaverton, Blooming Grove, Lamar County
Airport, Crews, Bedford, Bluff, Cody, Lamar County Public Lake, Star,
Pine Springs and Hightogy.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 3395 8822 3396 8795 3392 8795 3392 8791
      3365 8788 3365 8826
TIME...MOT...LOC 0919Z 271DEG 32KT 3378 8820

86/Martin

Special Weather Statement
National Weather Service Birmingham AL
444 AM CDT Mon Mar 23 2020

ALZ011>013-015-231030-
Fayette AL-Walker AL-Marion AL-Lamar AL-
444 AM CDT Mon Mar 23 2020

...SIGNIFICANT WEATHER ADVISORY FOR WESTERN WALKER...SOUTHEASTERN
MARION...FAYETTE AND SOUTHERN LAMAR COUNTIES UNTIL 530 AM CDT...

At 444 AM CDT, Doppler radar was tracking a strong thunderstorm near
Bluff, or near Fayette, moving east at 45 mph.

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

Locations impacted include...
Winfield, Fayette, Carbon Hill, Vernon, Berry, Oakman, Glen Allen,
Kansas, Belk, Beaverton, Gu-
Win, Eldridge, Bankston, Bluff, Boley Springs, Blooming Grove, Cody,
Wayside, Richard Arthur Field and West Corona.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 3393 8800 3396 8739 3360 8739 3363 8823
TIME...MOT...LOC 0944Z 270DEG 37KT 3378 8788

86/Martin