Severe Thunderstorm Warning 384, NWS Birmingham, AL

Area Forecast Discussion
National Weather Service Birmingham AL
430 PM CDT Wed Aug 9 2023

...New LONG TERM...

.SHORT TERM...
(This evening through Thursday)
Issued at 111 PM CDT WED AUG 9 2023

This afternoon and evening...an area of thunderstorms is expected to
move across northern Alabama through the early evening.
Instabilities will start off around 3000 to 4000 J/kg this
afternoon, with PW values around the 90th percentile. Though
shear will start off low, values are expected to increase to
around 50 or so knots by mid afternoon as the area of storms
approaches the northern counties. High res models bring activity
into the northwest around 3 pm and moving through mainly the
northern half of central Alabama the rest of the afternoon and
evening. Any of this activity could produce strong storms with
rotating storms possible from so much shear expected. Damaging
winds would be the main threat. In the southern half of the area
this afternoon, in areas away from the influence of the cluster
of storms across northern Alabama, diurnally driven isolated to
scattered showers and thunderstorms could move through the area.
With instabilities so high, a few storms could be strong to
severe, though the chances are lower. Damaging winds would again
be the main threat.

Models show a break late this evening through around midnight.
Another wave of storms is expected to move from western TN into
northwest central Alabama between midnight and 2 am. From here,
the line will move very quickly east and move out of the state by
3 or 4 am. Shear will be very high, though instabilities will be
limited. The strength of these storms highly depends on what
activity occurs across the northern counties this afternoon and
how much the area can be worked through. Damaging winds will be
possible with any strong to severe storms overnight.

A boundary will then move into the state bringing a chance for
more convection through the rest of the day on Thursday. Exact
timing and location of the boundary and storm development could
change, but for now, scattered showers and thunderstorms will be
possible through the morning and afternoon across the northern
half of the state. There will be enough shear, moisture, and
instabilities remaining for a few severe storms to be possible.
The boundary is expected to continue to weaken through the day,
with more isolated storms possible in the southern half of the
area through the afternoon.

Heat indices will again be in the triple digits across the south
today, with a Heat Advisory to remain in effect. Tomorrow, heat
indices will be 105 in several counties in the south, south of the
boundary. Will continue the Heat Advisory for now through the
evening, though depending on cloud cover tomorrow, a few of the
northern counties in the Advisory may need to be cancelled early.

24

&&

.LONG TERM...
(Thursday night through next Tuesday)
Issued at 406 PM CDT WED AUG 9 2023

No major changes were made to the extended. Scattered storms will
remain possible for Friday night with NW flow around the N Gulf
upper ridge. NW flow continues for the weekend but with a tad less
low level moisture with the upper ridge expanding N and NW.
Diurnal storms will remain possible over the weekend. A front is
progged to move into AL Mon into Tue with continued storms chances
along and ahead of the boundary. Depending on how far S the
boundary gets, extended guidance tries to bring some drier air at
the least into the NRN counties for the middle of next week
across the N half of C AL. This should help the humidity at the
least.

08

Previous long-term discussion:
(Thursday through Tuesday)
Issued at 345 AM CDT WED AUG 9 2023

Thursday and Friday.

Mid-level ridging will begin to build over Central Gulf of Mexico
to begin the long-term forecast period while a more zonal flow
pattern aloft will allow more disturbances to move east from over
the Central Plains to over the Mid-South and Tennessee Valley
Regions through the day Thursday. Expect chances for showers and
thunderstorms to be highest across the far northern counties with
lower chances further south. A shortwave trough will move east
over the Southern Appalachians on Friday, resulting in the better
chances for shower and thunderstorm activity being across the
northern and eastern counties.

Saturday through Tuesday.

The mid-level ridging will continue to gradually amplify further
on Saturday, resulting in a more isolated coverage of shower and
thunderstorm activity each day through the weekend. Global model
solutions begin to diverge significantly toward Monday with regard
to ridge strength over our area along with the amplification of
an upper low over Northeast Canada and potential compact mid-level
low over the Northern Plains. General trends are for the ridging
over us to weaken to an extent, permitting some increase in PoPs
across the south/southeast counties by Tuesday.

Hazard assessment... heat concerns continue.

Heat will remain the story through the extended forecast period
with heat indices around 105 expected across the southern half of
the area on Thursday, followed by all but the far north/northeast
on Friday with potential for values near 100 south. Values will be
around 105 degrees for most of the area Saturday and Sunday with
values again near 110 far south. Some limited relief may
materialize across the far north/northeast counties Monday while
the rest of the area will continue to experience values over 105
degrees with readings close to 110 possible far southeast and far
west. Some reduction in the heat indices across the northern half
of the area may materialize on Tuesday, but it is good to remain
cautious given the aforementioned spread in guidance solutions
this far out.

05

&&

.AVIATION...
(18Z TAFS)
Issued at 111 PM CDT WED AUG 9 2023

An area of storms is expected to move across the northern half of
Alabama through the evening. Activity should remain just north of
KBHM, KANB, and KASN, though a few stray showers and thunderstorms
could move to each site. Exact movement and timing of any
activity over any TAF site is low confidence for now so included
VCSH and will update when needed. At KMGM and KTOI this afternoon,
isolated diurnally driven convection is possible. Included VCSH
again for uncertainties in timing and location of any activity.
Overnight through Thursday, a boundary will move south with waves
of activity expected. Timing and coverage of activity overnight
will depend on how much the environment is worked through from
each wave before that.

24

&&

.FIRE WEATHER...

Chances for showers and thunderstorms will remain higher across
the northern counties through Friday, followed by isolated to
scattered activity expected across the area over the weekend and
into early in the next work week. Minimum relative humidity
values will be in the 45 to 65 percent range on Thursday and Friday.

&&

.PRELIMINARY POINT TEMPS/POPS...
Gadsden     70  90  70  92 /  50  50  50  40
Anniston    72  91  72  92 /  50  50  50  50
Birmingham  74  91  74  92 /  50  50  50  50
Tuscaloosa  75  91  74  93 /  40  40  40  50
Calera      75  92  75  92 /  40  40  50  50
Auburn      75  91  75  91 /  20  30  30  50
Montgomery  77  96  76  96 /  20  30  30  50
Troy        75  97  76  97 /  10  20  20  50

&&

.BMX WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 9 PM CDT Thursday for the following
counties: Autauga-Barbour-Bibb-Bullock-Chilton-Dallas-Elmore-
Greene-Hale-Lowndes-Macon-Marengo-Montgomery-Perry-Pickens-Pike-
Russell-Sumter-Tuscaloosa.

&&

SHORT TERM...24
LONG TERM....08
AVIATION...24

Hazardous Weather Outlook
National Weather Service Birmingham AL
217 PM CDT Wed Aug 9 2023

ALZ011>015-017>050-102230-
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-
217 PM CDT Wed Aug 9 2023

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

.DAY ONE...Outlook through Tonight.

Severe thunderstorms, with damaging winds and large hail, are
possible across Central Alabama into the evening hours. Additional
severe storms are possible after midnight.

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

Severe thunderstorms are possible across portions of Central Alabama
on Thursday. Storms will pose a threat of damaging wind gusts.

Heat indices will approach 105 degrees across southern portions of
Central Alabama through Tuesday.

.SPOTTER INFORMATION STATEMENT...

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

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