Severe Thunderstorm Warning 147, NWS Birmingham, AL

Area Forecast Discussion
National Weather Service Birmingham AL
155 PM CDT Sat Jul 9 2022

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

&&

.SHORT TERM...
/Updated at 1220 PM CDT Sat Jul 09 2022/

A frontal boundary will continue to move to the south towards
Alabama from the MS River Valley through the afternoon and
evening. Scattered convection is possible ahead of this boundary.
Instability will be between 4000 and 4500 J/kg and DCAPE values
between 1200 and 1500 J/kg. LI around -7 and PW values around 2.22
inches. Any thunderstorms that can develop could become strong to
severe with damaging winds up to 60 mph the main threat from
downburst or microburst winds. With such a high air moisture
count...localized flooding is also possible in areas that receive
training thunderstorms.

The boundary is expected to produce clusters of storms with the
main activity moving into the northern counties between 4 pm and
6 pm...moving south to Birmingham between 7 pm and 9 pm...and
finally reach I85 between 10 pm and 12 am. A mid level weak jet
will move through with this boundary and allow for stronger
midlevel winds into the 30-40kt range. Once the actual front moves
into the area...getting into the northern counties between 7 pm
and 9 pm and moving south...sounding profiles become completely
saturated with widespread showers possible through the late
night/early morning. Localized flooding is possible with the
storms produced from this boundary...and showers that remain along
the boundary. By the time the boundary reaches areas between I65
and I85...the boundary will stall somewhat with showers and
occasional thunderstorms possible through the night and early
morning.

Sunday...the boundary will slowly move to the south through the
day...settling over areas around I85. Areas north of this boundary
will have north to northwesterly flow...while areas sough of this
boundary will have south to southwesterly low level flow. With
this band of convergence set up...can expect showers and
thunderstorms through the day. Instability will be around 3000
though DCAPE should remain at or below 1000 J/kg. A few storms
could become strong with damaging winds the main threat...as well
as localized flooding with PW values remaining around 2.2 inches.

High temperatures this afternoon will be upper 80s in the far east
where storms slowly worked through the area today...to the upper
90s in the west with skies remaining mostly clear throughout the
day. Heat indices have remained between 102 and 107 across much
of the state and will let the Heat Advisory continue through 7 PM
tonight. Tonight...low temperatures will be in the low to mid 70s.
Fog development is possible overnight in areas that receive late
rainfall. Sunday...high temperatures will be in the mid 80s to
lower 90s. With temperatures several degrees lower on
Sunday...heat indices only reach the upper 90s.

24

.LONG TERM...
/Updated at 0330 AM CDT Sat Jul 09 2022/

Monday through Friday.

A changing synoptic pattern will bring heat relief to the Southeast
this weekend, and this trend will continue into the long-term
forecast period with forecast high temperatures remaining at or
below average.

Generally speaking, deep-layer ridging and anticyclonic flow aloft
is progged to move west and strengthen, encompassing a broad area
centered near the Four Corners region. Meanwhile, a slow-moving
negative height anomaly is progged to remain in our area through at
least Tuesday. This disturbance aloft will coincide with a tropical
airmass now suppressed to our south, fostering clusters of convection
focused across the northern Gulf of Mexico and along the Gulf Coast.
Nonetheless, diurnal rain chances will favor our southern zones for
Monday where PWs approach 2.0" south of I-85. PWs likely remain 1.5"
or less north of I-20 where only isolated coverage is forecast.
Increasing southerly flow will favor moisture advection across
Central Alabama on Tuesday. This led to an increase in diurnal rain
chances.

Medium-range continues to suggest the disturbance/low to our
southwest becoming more cohesive on Tuesday, before advancing
northeast toward the southern Appalachians as an open wave mid-level
trough on Wednesday. Showers and thunderstorms are likely across all
of Central Alabama Wednesday afternoon and evening as PWs could
increase to 2.3" south of I-20. Wednesday will continue to be
watched as rain chances will probably need an increase amidst this
tropical airmass/storm system. Furthermore, wind shear sufficient
for a few severe thunderstorms could manifest for areas south of I-
20 as a ~30 kt low-level jet could coincide with the advancing
disturbance. By Thursday this system will have exited our area to
the east as an upper-level shortwave moves east across the OH and TN
Valleys. Thus, a more subsident environment will be in place on
Thursday with PWs decreasing from the northwest. Regardless, at
least isolated showers and thunderstorms are forecast Thursday and
Friday afternoons, with scattered coverage possible south of I-20
where better moisture quality remains.

40/Sizemore

&&

.AVIATION...
18Z TAF Discussion.

Scattered convection is possible this afternoon ahead of clusters
of storms moving through the state along an outflow boundary. Due
to uncertainty in timing and coverage...VCTS has been included in
every TAF through the early afternoon. Any thunderstorm that moves
over a TAF site could reduce visibilities to IFR due to the heavy
rainfall and high moisture content. Fog development is possible at
each TAF site overnight...but have left mention out of the TAFs
for now due to uncertainty in intensity and coverage. Sunday...
scattered showers and thunderstorms are possible again through the
day as the frontal boundary lays across the middle of the state.

24

&&

.FIRE WEATHER...

Hot and humid conditions will persist through this afternoon with
heat indices above 105 at times. Fairly widespread showers and
thunderstorms are expected this afternoon and evening with soaking
rainfall. Some convection could be strong to severe with locally
heavy rainfall. Southwesterly surface and transport winds at 5-10
mph are forecast today. Winds will veer behind a front later
tonight, and slightly drier air will advect from the northwest for
Sunday.

&&

.PRELIMINARY POINT TEMPS/POPS...
Gadsden     70  87  69  88  70 /  80  60  20  30  10
Anniston    69  86  71  87  71 /  90  70  20  40  20
Birmingham  72  88  72  89  73 /  90  60  20  30  10
Tuscaloosa  74  89  73  93  73 /  90  50  10  30  10
Calera      72  86  72  89  72 /  90  60  20  40  20
Auburn      71  86  72  86  72 /  80  80  50  60  30
Montgomery  74  91  74  91  73 /  80  80  40  60  30
Troy        73  88  72  89  72 /  60  80  50  70  30

&&

.BMX WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 7 PM CDT this evening for the following
counties: Autauga...Barbour...Bibb...Blount...Bullock...
Calhoun...Chambers...Cherokee...Chilton...Clay...Cleburne...
Coosa...Dallas...Elmore...Etowah...Fayette...Greene...Hale...
Jefferson...Lamar...Lee...Lowndes...Macon...Marengo...Marion...
Montgomery...Perry...Pickens...Pike...Randolph...Russell...
Shelby...St. Clair...Sumter...Talladega...Tallapoosa...
Tuscaloosa...Walker...Winston.

&&

Hazardous Weather Outlook
National Weather Service Birmingham AL
338 PM CDT Sat Jul 9 2022

ALZ011>015-017>050-102345-
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-
338 PM CDT Sat Jul 9 2022

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

.DAY ONE...Outlook through Tonight.

Heat indices are expected to be near or above 105 degrees this
afternoon, with some locations approaching 109 degrees.

Strong to severe thunderstorms are possible through midnight across
all of Central Alabama. Damaging wind up to 65 mph is the primary
threat.

Showers and thunderstorms will produce locally heavy rainfall through
this evening. A few inches of rain may fall in a short period of
time. Flooding of low lying or poor drainage areas may result.

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

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Activation of storm spotters and emergency management may be needed
through this evening.

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