Special Weather Statement, NWS Birmingham, AL

Area Forecast Discussion
National Weather Service Birmingham AL
257 PM CDT Wed Sep 1 2021

.SHORT TERM...
/Updated at 1254 PM CDT Wed Sep 01 2021/

A shortwave and associated boundary will continue to move south
through Alabama through the afternoon where it will slow down and
remain across central Alabama from afternoon through the early
night. This boundary will finally gain momentum and move to the
south of the area by the early morning. Scattered showers and
thunderstorms will be possible beginning in the northern part of
the CWA...then moving south reaching Montgomery by mid afternoon.
In areas south of I20...showers and thunderstorms could linger
through the early night as that boundary stalls slightly...then
all activity is expected to weaken and move south following the
boundary by the early morning. Instabilities will be between 1500
and 2000 J/kg with DCAPE values between 1000 and 1500 J/kg this
afternoon. There isn't an impressive amount of wind shear...though
part of the column through the atmosphere will have unidirectional winds
at least 30 kts or greater. This could move storms fairly
quickly...especially any that get pushed along with an outflow
boundary. PW values around the 50th percentile won't pose too much
of a flooding threat...though areas experiencing river flooding
will need to keep an eye on any lingering storms. Overall...with
ample dry air in the mid levels and a large amount of DCAPE...will
advertise a damaging wind threat with any stronger storms. A few
storms may be severe...especially in the southern half of the
state where the instability and upper level forcing are stronger.

With plenty of moisture in the low levels...patchy fog could
develop in the early morning. If a lot of rain falls
tonight...especially in areas south...there could be patchy dense
fog...so will need to keep an eye on the storms through the
evening.

Thursday...high pressure over the MS River Valley will put the
area in northwesterly flow...bringing a nice change of cooler air
to the state. Mostly clear skies and light winds are expected with
lows in the morning starting in the mid and upper 60's and the
high of the day in the mid to upper 80's.

24

.LONG TERM...
/Updated at 0242 PM CDT Wed Sep 01 2021/

Drier weather and lower humidity remains the focus of the forecast
through Saturday, ahead of an approaching trough. No significant
changes needed to the extended as this trough brings the next
chances of rain. Will likely be refining timing of best rain
chances for early next week as models refine the timing of
shortwaves better.

14

Previous long-term discussion:
/Updated at 0258 AM CDT Wed Sep 01 2021/

Friday through Tuesday.

Mild conditions expected across Central AL as we reach the end of
the week and head into the holiday weekend. Ridging builds in across
the Southern CONUS as a drier air mass advects into the region.
Low temperatures Friday morning will be in the low to mid 60s for
most of Central AL with highs in the mid to upper 80s.

The ridge begins to flatten across the Southeast late Saturday as a
trough digs through the Upper Midwest. By Sunday morning, the trough
is across much of the East Coast, setting up more of northwesterly
flow pattern for our area, which will continue through early next
week. Model guidance suggests at least a couple of shortwaves
dipping through this trough that could lead to increased
rain/thunderstorm chances with the first pushing in on Sunday and
the second either Tuesday night or early Wednesday. For now, I've
trended rain/thunderstorm chances up for Sunday, Monday, and Tuesday
given there's uncertainty in the timing of any specific shortwave
impulse. We likely won't see rain every day, but there could be a
couple of waves push through.

25/Owen

&&

.AVIATION...
18Z TAF Discussion.

Scattered showers and thunderstorms will follow a boundary south
across the state through the afternoon. VFR conditions will
prevail unless convection moves over a TAF site...where MVFR
visibilities and ceilings will be possible. Overnight...plenty
of low level moisture will allow for fog development. For now
included MVFR visibilities at all TAF sites except KBHM.
Visibilities could go to IFR or lower...but with light winds
possible...confidence was too low to go lower than MVFR for now.
Thursday...high pressure and VFR conditions.

24

&&

.FIRE WEATHER...

Low level moisture will remain elevated for one more day across
Central Alabama, leading to the possibility of fog and/or low
ceilings early Thursday morning.

Drier and rain-free weather is expected tomorrow through Saturday
as a drier air mass builds into the region. Winds will be out of
the north at 6-8mph Thursday, before weakening through the
weekend. Min RHs will remain around the 45 to 55 percent range
through early next week.

&&

.PRELIMINARY POINT TEMPS/POPS...
Gadsden     64  85  62  87  63 /  20   0   0   0   0
Anniston    65  86  64  88  66 /  20   0   0   0   0
Birmingham  65  85  64  87  67 /  30  10   0   0   0
Tuscaloosa  67  85  64  87  67 /  30  10   0   0   0
Calera      66  86  65  88  68 /  30  10   0   0   0
Auburn      67  86  67  87  67 /  30  10   0  10   0
Montgomery  69  90  67  90  68 /  50  10   0  10   0
Troy        69  88  67  90  68 /  50  10   0  10   0

&&

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

&&

Hazardous Weather Outlook
National Weather Service Birmingham AL
305 AM CDT Wed Sep 1 2021

ALZ011>015-017>050-021115-
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-
305 AM CDT Wed Sep 1 2021

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

.DAY ONE...Outlook through Tonight.

Minor flooding is forecast along portions of the Tombigbee and
Sucarnoochee Rivers today. Please see the latest flood statements
for more details.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

Minor flooding is forecast along portions of the Tombigbee and
Sucarnoochee Rivers through the end of the week. Please see the
latest flood statements for more details.

.SPOTTER INFORMATION STATEMENT...

Activation of storm spotters and emergency management is not
expected at this time.

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