Special Weather Statement, NWS Birmingham, AL

Area Forecast Discussion
National Weather Service Birmingham AL
103 PM CDT Sun Oct 3 2021

.UPDATE...
Midday Update and 18Z Aviation.

&&

.SHORT TERM...
/Updated at 1241 PM CDT Sun Oct 03 2021/

High pressure will continue to move east today as a low pressure
and trough develops and strengthens over the lower MS Valley.
With placement on the right side of this trough...plenty of
consistent winds out of the south and southwest will allow for a
steady stream of moisture. A frontal boundary will develop today
and move slowly south and east overnight. This combined with upper
level divergence will allow for plenty of shower and thunderstorm
development this afternoon across the entire state. Winds in the
mid and upper levels are decently strong...though low levels
remains weak. Instability is around 1000 - 1500 J/kg this
afternoon. PW values are around the Max for climatology for this
time of year. With all this said...would expect plenty of showers
and a few strong thunderstorms. Not expecting much in the way of
severe weather...though a flooding threat is definitely a concern
with so much moisture available. High temperatures will be in the
upper 70's and lower 80's.

Tonight...activity should become more isolated to scattered in
nature with instability dropping to below 1000 J/kg. Any areas not
experiencing any rain could see locally dense fog...though
overcast skies and light winds should limit any fog development
from becoming widespread. Low temperatures will be in the 60's.
Monday...scattered to widespread showers and thunderstorms will
continue. There will be plenty of instability with CAPE values
around 2000 J/kg and high PW values. Winds will be weak in the mid
levels. Concern is once again for flooding with strong storms
producing heavy rainfall rates...as well as storms training or
moving over the same areas continuously. Highs will be in the
upper 70's and lower 80's.

24

.LONG TERM...
/Updated at 0355 AM CDT Sun Oct 03 2021/

Tuesday and Wednesday.

If you're watching trends with the advertised upper-level system for
the upcoming week you may have noticed a shift westward with its
positioning in recent model guidance. This has impacted forecast
considerations, mainly in the rainfall department, through mid next
week. The overall forecast picture remains somewhat the same in that
a disturbance is expected to dive southward and eventually become a
cutoff low. This process will become more evident by Tuesday with
the low occluding and centering generally near the ArkLaMiss.
Through this time the overall trough axis should swing from a
positive to neutral tilt, with the primary vort max progged to kick
northeastward across the Tennessee Valley by Tuesday afternoon. As
this process is underway, forcing for ascent will become quite
strong across the Deep South both from upper-level jet dynamics and
warm, moist advection along and south of a residual, loosely defined
surface front. 20-30 kt southerly 925-850 mb flow is expected to
provide a corridor of anomalously high PWs for this time of year
(1.7-1.8") mainly along and south of the I-59 corridor.
Additionally, MLCAPE could range from 500-1,000 J/kg. This will
support embedded thunderstorms. These considerations suggest periods
of rainfall, some heavy at times in embedded thunderstorms, from
early Tuesday morning through Tuesday night. Some stronger storms
are possible if the mesoscale variables come together. Various
forecast soundings suggest enough wind shear (eff. bulk shear 30-40
kts) and hodograph curvature to keep an eye on things.

The upper-low is expected to hang back to our northwest through
Wednesday night. Confluent low-level flow should persist across our
area as a result. Another period of elevated rain chances is
expected on Wednesday, especially as diurnal heating occurs during
the afternoon. Forcing will not be as robust, but some locally heavy
rainfall could linger. Confidence is too low for a severe weather
threat at this time. However, heavy rainfall on Tuesday and
Wednesday could lead to flooding or flash flooding, particularly in
low-lying or poor drainage areas. This will be messaged in the HWO
accordingly.

Thursday through Saturday.

By Thursday the synoptic feature is forecast to begin lifting to our
north. A drier, stable airmass is expected to move into the area
from the west through this time. Flow aloft will transition to a
more northwesterly direction by Friday. Nice, mild weather is
forecast across the area by the end of the period.

40/Sizemore

&&

.AVIATION...
18Z TAF Discussion.

Scattered to widespread showers and thunderstorms will continue
through the TAF period. Between showers...VFR ceilings are
expected...but convection over any TAF site could cause IFR
visibilities.

24

&&

.FIRE WEATHER...

Elevated moisture content will lead to widespread rain chances
today with southerly surface and transport winds at 5-10 mph. A
weak frontal boundary will pass through the area later tonight.
The front will linger in the region for the next few days and will
interact with another disturbance on Tuesday. Thus, rain chances
will remain quite high through at least Wednesday. Rainfall could
be heavy at times as thunderstorms are expected throughout the
period. KBDI values remain 200-400 and will likely decrease.

&&

.PRELIMINARY POINT TEMPS/POPS...
Gadsden     65  78  63  75  63 /  70  60  40  90  80
Anniston    66  78  65  76  65 /  70  70  50  90  80
Birmingham  67  78  64  76  64 /  70  60  40  80  70
Tuscaloosa  68  80  65  77  64 /  70  50  30  70  50
Calera      67  77  65  75  64 /  60  70  50  80  70
Auburn      66  77  65  75  65 /  60  80  70  90  80
Montgomery  68  79  67  76  66 /  50  80  70  90  70
Troy        66  80  67  78  66 /  50  80  70  90  70

&&

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

&&

Hazardous Weather Outlook
National Weather Service Birmingham AL
409 AM CDT Sun Oct 3 2021

ALZ011>015-017>050-041215-
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-
409 AM CDT Sun Oct 3 2021

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

.DAY ONE...Outlook through Tonight.

No hazardous weather is expected at this time.

.DAYS TWO THROUGH SEVEN...Monday through Saturday.

Locally heavy rainfall is possible across Central Alabama Monday
afternoon through Wednesday evening. This could lead to flash
flooding of low lying or poor drainage areas.

.SPOTTER INFORMATION STATEMENT...

Activation of storm spotters and emergency management may be needed
Monday through Wednesday.

Special Weather Statement
National Weather Service Birmingham AL
248 PM CDT Sun Oct 3 2021

ALZ039-032030-
Marengo AL-
248 PM CDT Sun Oct 3 2021

...A strong thunderstorm will impact portions of northern Marengo
County through 330 PM CDT...

At 247 PM CDT, Doppler radar was tracking a strong thunderstorm over
Pin Hook, or near Linden, moving northeast at 25 mph.

HAZARD...Winds in excess of 40 mph.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects.

Locations impacted include...
Demopolis, Linden, Jefferson, Faunsdale, Dayton, Pin Hook, Chickasaw
State Park and Old Spring Hill.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 3238 8798 3253 8773 3248 8772 3248 8752
      3237 8753 3222 8787
TIME...MOT...LOC 1947Z 234DEG 22KT 3234 8786

MAX HAIL SIZE...0.00 IN
MAX WIND GUST...40 MPH