Severe Thunderstorm Warning 117, NWS Birmingham, AL

Area Forecast Discussion
National Weather Service Birmingham AL
130 PM CDT Fri May 22 2020

.UPDATE...
For 18Z Aviation.

&&

.SHORT TERM...
/Updated at 1057 AM CDT Fri May 22 2020/
This Afternoon through Tomorrow.

Stronger storms continue to move through northern AL/GA this morning
along an effective warm front which has been slowly lifting
northward through the overnight hours with additional lifting from a
weak mid-level shortwave. The majority of activity has remained
north of our forecast area with observed storm motions indicating a
slight northeastward trend. The upper-low which as been parked to
our northeast for the past two days has begun rapidly ejecting
towards the Northeastern CONUS. At the same time, low-level ridging
is building to our east, and south-southwesterly flow will drive an
increase in warm, moist air across Central AL. We're already
beginning to see a surge in moisture across the south with dewpoints
in the 70s, a developing cumulus field, and remnant outflow,
observed on satellite imagery, surging southward from the storms to
our north. Temperatures are expected to reach the upper 80s to near
90F in our southern counties. Destabilization during peak heating,
in tandem with leftover mesoscale boundaries, may trigger scattered
thunderstorm development, particularly south of I-20/59. The 12Z BMX
RAOB measured a 500mb temperature of -12.5 degrees C with 700-500mb
lapse rates of 7.2C/km. Latest hi-res guidance indicates 500mb
temperatures across the south may be a degree or two cooler with
moderately steep lapse rates, SBCAPE around 2500J/kg, and 0-6km
shear around 15-20kts this afternoon. This would suggest the
potential for hail development and accompanying gusty winds in any
stronger storms that can sustain a strong enough updraft despite
uncertainties including the somewhat less than favorable shear and
lack of synoptic-scale forcing. Although severe storms are not
anticipated, a couple stronger storms are not completely out of the
question. Some activity will linger after dark, but will gradually
decrease with the loss of daytime heating.

Southerly flow becomes more prominent tomorrow as the ridge
continues to amplify over the Southeast. Temperatures will be a
couple degrees warmer throughout the area with a repeat of isolated
to scattered showers and thunderstorms during the afternoon.

86

.LONG TERM...
/Updated at 333 AM CDT Fri May 22 2020/
Sunday through Thursday.

Overall large scale ridging will take hold over the southeast on
Sunday. conditions will become more summer-like, with highs in the
upper 80s to low 90s and the typical afternoon airmass scattered
convection. As this ridge builds stronger across the south and east
coast through the remainder of the forecast period, a strengthening
shortwave trough will begin to eject out of the Southern Rockies and
stall across the Southern Plains, thanks to the strong ridging in
the east. Despite the stalling of this low, southerly flow will
continue to pump in gulf moisture into the area through mid week.
This will increase the precipitation chances through each afternoon,
and slightly lower afternoon highs due to the somewhat increase in
clouds. By Thursday the upper low in the west begins to retrograde
to the southwest as the ridging builds in the east. This looks to
change the upper level flow to the east and could bring in a
slightly drier airmass on Thursday and into Friday.

16

&&

.AVIATION...
18Z TAF Discussion.

TSRA development is currently ongoing across southern portions of
Central Alabama and will affect MGM and TOI through the remainder
of the afternoon. Gusty winds will be likely within any storm that
passes over a terminal location along with rapid reductions in vis
due to heavy rainfall. SHRA has been included for northern
terminals (BHM, EET, TCL, ASN, ANB) due to reduced coverage of
showers, but an isolated storm can't be ruled out that may venture
close to the vicinity of those locations. Shower and storm
activity will decrease through the overnight hours tonight with
another chance for low cloud development by early Saturday
morning, especially for the southern terminals of MGM and TOI.
We've gone ahead and trended toward lower cigs for all terminals
by 12z Saturday morning, with higher confidence of IFR cigs at
TOI.

56/GDG

&&

.FIRE WEATHER...

A more summer like pattern with daily isolated to scattered showers
and thunderstorms is expected through the weekend and into the first
of next week. Minimum RH values are forecast to remain above 40
percent through the upcoming weekend with generally light winds
outside of any thunderstorm activity.

&&

.PRELIMINARY POINT TEMPS/POPS...
Gadsden     65  88  64  89  65 /  20  40  20  30  30
Anniston    66  88  65  89  66 /  20  40  20  40  30
Birmingham  69  89  68  91  69 /  20  40  20  30  30
Tuscaloosa  70  90  68  91  69 /  20  30  20  30  20
Calera      68  88  67  90  68 /  20  30  20  30  30
Auburn      66  88  66  89  66 /  30  20  20  30  30
Montgomery  67  91  68  92  68 /  30  30  20  30  30
Troy        68  91  67  92  67 /  30  30  20  30  30

&&

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

&&

Hazardous Weather Outlook
National Weather Service Birmingham AL
308 PM CDT Fri May 22 2020

ALZ011>015-017>050-232315-
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-
308 PM CDT Fri May 22 2020

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

.DAY ONE...Outlook through Tonight.

Strong thunderstorms are possible across Central Alabama through 8
pm. Storms will be most numerous south and east. The strongest storms
will produce isolated damaging wind gusts to 60 mph and nickel size
hail.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Activation of storm spotters and emergency management should not be
necessary. Please follow all local, state, and CDC guidelines in
regards to travel.

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