Severe Thunderstorm Warning 161, NWS Birmingham, AL

Area Forecast Discussion
National Weather Service Birmingham AL
143 PM CDT Thu Jul 21 2022

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

&&

.SHORT TERM...
/Updated at 0130 PM CDT Thu Jul 21 2022/

Through This Afternoon.

Still dealing with a tough forecast today which will be
characterized by dangerous heat conditions across the area followed
by scattered to numerous thunderstorm development late this
afternoon and evening. An east to west oriented surface front is
becoming generally parallel to the AL/TN stateline. Moisture is
pooling south of the front and resulting in widespread dewpoints in
the mid to upper 70s across Central AL with PWATs ranging from 2-2.2
inches. With temperatures in the lower to mid 90s, dangerously hot
conditions will continue through the afternoon. Unfortunately, the
only relief from the heat will come in the form of thunderstorms,
some of which could become severe. Large amounts of instability were
already in place this morning, and now upwards of 4000-4500 J/kg
of MLCAPE is collocated with 1200-1400 J/kg of DCAPE across much
of the northern half of Alabama where lapse rates have steepened
and where eff. bulk shear is ~15-20kt. There is some uncertainty
on exact location where storms will initiate, but generally
expecting development across northern portions of the forecast
area late this afternoon as the boundary slowly sinks towards the
south. Expect robust updrafts with strong storms propagating
southward capable of producing damaging straight-line winds from
downdrafts and perhaps a few cases of large hail. Heavy tropical
downpours could also result in localized flooding.

Tonight Through Friday.

Convection is expected to linger into the evening hours and
become focused near and south of the US HWY 80 corridor by
midnight with some continuing risk of strong storms until then.
Drier air will move in across our northern half on Friday with
PoPs becoming focused across our south. We could see a strong
storm or two, but appears less likely as the airmass should be
fairly worked over after the overnight convection. Temperatures
will be on the warm side again tomorrow with highs ranging from
the upper 80s east to mid 90s west. This could push heat indices
towards 105F for a couple hours west of I-65. Will continue to
evaluate the potential need for a Heat Advisory for tomorrow.

86

.LONG TERM...
/Updated at 0415 AM CDT Thu Jul 21 2022/

Saturday through Wednesday.

A low amplitude mid- to upper-level ridge is progged to encompass
much of the southern and southeastern CONUS through the long-term
forecast period. Most operational models suggest it will remain most
prominent/centered just to our west which will flow aloft out of the
north across Alabama. Ridging will coincide with a large low-level
anticyclone extending from the western Atlantic well into the lower
Mississippi Valley which will foster light southerly to
southwesterly surface/low-level flow each day. This will allow for
PWs favorable for diurnal convection to become more evenly
distributed across the forecast area by early next week, rather than
the better moisture confined to areas farther south this weekend.
This overall pattern will lead to little weather diversity over the
next several days outside of any mesoscale features. Diurnal
temperatures will run at or above average and the combination of
heat and humidity could lead to areas meeting Heat Advisory criteria
for most of the period as well. This will remain in the HWO and will
be the biggest weather headline over the next several days.

40/Sizemore

&&

.AVIATION...
18Z TAF Discussion.

Active period expected later this afternoon and through the evening
hours as convection initiates across north AL and propagates
southward. Generally expecting highest coverage around the 23-00Z
timeframe, but activity could linger near MGM/TOI as late as 06Z.
Amendments will be used as needed depending on the evolution of
storms. Behind the rain, low ceilings will develop tomorrow
morning from ~10-13Z then begin to gradually rise after 13Z.

86

&&

.FIRE WEATHER...

Increasing coverage of showers and thunderstorms is expected by mid
to late afternoon. Some storms could be strong to severe with gusty
winds and heavy rain. Soaking rainfall is expected across a good
portion if not all of the forecast area today. Southwesterly surface
and transport wind at 5-10 mph will continue. Minimum RH values
remain above 45%. Excessive heat conditions are also expected for
much of the area with heat index values 105 to 110 degrees at
times.

&&

.PRELIMINARY POINT TEMPS/POPS...
Gadsden     71  93  71  93  72 /  50  10  10  20  10
Anniston    72  91  71  93  73 /  60  30  10  30  10
Birmingham  73  92  73  94  75 /  60  20  10  30  10
Tuscaloosa  74  93  74  95  75 /  60  30  10  20  10
Calera      74  91  74  93  74 /  60  40  20  30  10
Auburn      73  88  72  90  73 /  60  60  20  30  10
Montgomery  75  92  74  95  75 /  60  60  20  30  10
Troy        73  89  72  92  73 /  60  70  20  30  10

&&

.BMX WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 7 PM CDT this evening for the following
counties: Autauga...Barbour...Bibb...Blount...Bullock...
Calhoun...Cherokee...Chilton...Coosa...Dallas...Elmore...
Etowah...Jefferson...Lowndes...Macon...Montgomery...Perry...
Pike...Russell...Shelby...St. Clair...Talladega...Tallapoosa.

Excessive Heat Warning until 7 PM CDT this evening for the
following counties: Fayette...Greene...Hale...Lamar...Marengo...
Marion...Pickens...Sumter...Tuscaloosa...Walker...Winston.

&&

Hazardous Weather Outlook...UPDATED
National Weather Service Birmingham AL
1250 PM CDT Thu Jul 21 2022

ALZ011>015-017>050-222100-
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-
1250 PM CDT Thu Jul 21 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 will reach or exceed 105 degrees across much of Central
Alabama today. Areas west of Interstate 65 could see heat indices of
110 degrees.

Strong to severe thunderstorms are possible across Central Alabama
through midnight tonight. Threats include damaging wind gusts up to
60 mph and hail up to quarter size. Localized flooding is also
possible in low lying or flood prone areas.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday.

Heat indices could reach or exceed 105 degrees across portions of
Central Alabama Friday through Tuesday.

.SPOTTER INFORMATION STATEMENT...

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

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