Special Weather Statement, NWS Birmingham, AL

Area Forecast Discussion
National Weather Service Birmingham AL
1239 PM CDT Fri Jul 31 2020

.UPDATE...
Midday Update.

&&

.SHORT TERM...
/Updated at 100 PM CDT Fri Jul 31 2020/

Features.

In the upper levels, a broad trough was analyzed from upper air
sounding data over the Central and Southern Plains while broad
ridging was evident over the Southwestern States and to our east
over the Southwest Atlantic Basin.

In the mid levels, a closed low was analyzed over Southwest
Missouri with water vapor imagery also depicting this feature. A
disturbance in the flow was located over the Arklatex region and
was moving east-northeast. The mid level flow pattern was becoming
more amplified as ridging was continuing to expand over the
Southwestern States with deepening in the positive-tilt troughing
as a result over the Ohio River Valley and into the Central Plains
states.

In the lower levels aloft, the trough was well depicted from
Southeast Canada southwest over the Ohio River Valley and into
Northeast Texas. Ridging was also evident across much of the
Intermountain West region in addition to far to our southeast over
the Southwest Atlantic that extended across Central Florida and
into the Northeast Gulf of Mexico.

The surface analysis shows decreasing surface pressures across the
northwest portion of the state that extend further northwest into
the Mid South region where a cold front was analyzed across
Northeast Texas across Southeast Oklahoma and into Northwest
Arkansas. A surface low was positioned over Southwest Missouri
with a stationary front extending east into the Ohio River
Valley region.

The 31.12Z BMX sounding contains steeper lapse rates compared to
previous days, largely due to falling heights at 500 mb.
Modifying the observed sounding for forecast highs in the upper
80s yields nearly 3500 J/kg of convective available potential
energy. In addition to the instability formed by having very humid
and warm conditions near the surface along with weak cool
advection and falling heights aloft, we have winds generally from
20 to 30 kts observed in the low to mid levels aloft.

Observed soundings to our west across the Southern Plains into the
Lower Mississippi Valley region indicate winds 30-40 kts near the
base of the trough where the aforementioned shortwave was
generating convection in the Arklatex region.

Forecast.

Today.

Modeling indicates shortwave continuing to prograde east through
the day today while a slug of slightly drier air over the Northern
Gulf of Mexico moves northward into the area later today as well.
The addition of some drier air aloft would promote a wet
microburst risk with better chances south and central. Meanwhile,
the approaching storm system from the northwest, with associated
height falls aloft and weak cool advection aloft, will help
promote steeper lapse rates that would be sufficient for isolated
strong convection to develop. The presence of 30-40 kt winds
within the vertical column will further aid in storm development
and sustainment with time. Due to these factors, I did add mention
of isolated strong storms with damaging winds being the main
concern across much of the area with best potential from roughly
noon through 7 pm this evening.

Expect gradual increasing clouds with showers and storm chances
increasing with time from west to east, especially toward mid
afternoon. Convective activity is expected to continue to move
east across the area this evening through decreasing in coverage
and intensity with time. Highs will range from around 90 northwest
to the mid 90s southeast. The combination of heat and humidity
will produce heat indices near 105 degrees though the spatial
extent and duration should be too minimal to warrant an advisory
issuance.

Tonight.

Lingering showers and a few thunderstorms will persist late into
the evening though weakening with time. The better chances will be
across the north and northwest. Lows will range from the low 70s
north and east to the mid 70s south and west.

Saturday.

Expect scattered showers and storms across the area Saturday with
the best chances north and northwest. We will monitor potential
for a few stronger storms as the trough aloft will remain nearby
for another day. Highs will range from the mid 80s northwest to
the low 90s southeast.

05

.LONG TERM...
/Updated at 0346 AM CDT Fri Jul 31 2020/

Sunday through Friday.

On Sunday, a highly amplified upper-level pattern will feature a
ridge from the western CONUS into Northwest Canada and a trough
extending all the way from Hudson Bay to the Gulf of Mexico.
Meanwhile, tropical system Isaias is expected to approach the
Atlantic cost of Florida as it becomes captured by the large-scale
trough and moves northward along the East Coast. Our forecast area
will be on the subsident side of the storm, and only very isolated
shower/storm development is expected on Sunday near an old front
in our southeastern counties. The story doesn't change much for
Monday, with patches of residual drier air remaining across the
forecast area that should limit afternoon convection.

The same general upper-level pattern will continue into the
upcoming week with subsidence and high pressure persisting across
the Upper Midwest. Southward advection of this airmass is
expected which may affect moisture quality across the Deep South.
With persistent west to northwest flow, moisture recovery should
be modest. Rain chances generally range from 20 percent in the
northwest, to 30 percent in the southeast for Tuesday through
Friday. These values may be a bit too high and could be reduced if
model trends continue.

87/Grantham

&&

.AVIATION...
18Z TAF Discussion.

Expect VFR conditions at most locations to prevail through early
afternoon. Increasing chances for showers and some thunderstorms
are expected, especially across the northern and western portions
of the forecast area. Carried VCSH at all northern sites for this
issuance through sunset. Potential for TS is higher than previous
days but confidence was not quite high enough to include for any
site. Expect showers with some storms to develop and/or move in
from the west from mid afternoon through the evening hours. A few
storms may produce strong winds in addition to heavy rain.

An upper level trough will swing into the region this evening and
persist over the area through tomorrow. Expect a decrease in
convective activity after sunset but some lingering SHRA are
expected with higher potential across our northern sites. There
may be some limited reductions in CIGS and VIS in our southeast
but potential is too low to drop either significantly for this
issuance. Saturday will start with scattered to broken low to mid
level clouds followed by shower and storm development toward
midday and persisting into the afternoon hours.

05

&&

.FIRE WEATHER...

Humid conditions will continue through Saturday with high rain
chances particularly across the northern half of Alabama.
Southwest winds of 6-10 kts are expected. A front should bring
drier air to northern and central Alabama on Sunday.

&&

.PRELIMINARY POINT TEMPS/POPS...
Gadsden     72  89  67  88  66 /  30  50  20  10  10
Anniston    73  89  69  89  67 /  30  40  20  20  10
Birmingham  74  90  69  89  68 /  30  50  20  10  10
Tuscaloosa  74  90  69  89  68 /  30  50  10  10  10
Calera      73  88  69  89  67 /  20  50  20  10  10
Auburn      72  90  71  90  69 /  10  20  10  20  10
Montgomery  74  92  72  92  71 /  10  30  20  20  10
Troy        72  92  72  92  71 /  10  20  10  20  10

&&

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

&&

Hazardous Weather Outlook
National Weather Service Birmingham AL
128 PM CDT Fri Jul 31 2020

ALZ011>015-017>050-012130-
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-
128 PM CDT Fri Jul 31 2020

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

.DAY ONE...Outlook through Tonight.

There is a risk of a couple severe thunderstorms through roughly 7 PM
this evening, with the primary threat being damaging winds around 60
MPH. The risk will be greatest along and north of I-20, but storms
may still occur outside this area.

The combination of a storm system approaching from the northwest
along with some drier air that will move into the area will create
conditions that will support a few severe storms.

.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 may become
necessary this afternoon and evening.

Special Weather Statement
National Weather Service Birmingham AL
159 PM CDT Fri Jul 31 2020

ALZ015-017-024-311945-
Walker AL-Jefferson AL-Blount AL-
159 PM CDT Fri Jul 31 2020

...SIGNIFICANT WEATHER ADVISORY FOR EAST CENTRAL WALKER...CENTRAL
BLOUNT AND NORTH CENTRAL JEFFERSON COUNTIES UNTIL 245 PM CDT...

At 159 PM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from near Cullman to near Arkadelphia to Gorgas
Steam Plant. Movement was east at 30 mph.

Pea size hail and winds of 40-50 mph will be possible with these
storms.

Locations impacted include...
Gardendale, Sumiton, Cordova, Dora, Blountsville, Cleveland, Warrior,
Kimberly, Morris, Locust Fork, Trafford, Hayden, Sipsey, Nectar,
Rosa, County Line, Bangor, Strawberry, Rocky Hollow and Burnwell.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Frequent cloud to ground lightning is occurring with these storms.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

To report severe weather, contact your nearest law enforcement
agency. They will relay your report to the National Weather Service
office in Birmingham.

&&

LAT...LON 3421 8641 3405 8648 3367 8684 3367 8730
      3389 8707 3389 8701 3387 8700 3386 8696
      3387 8692 3392 8692 3397 8678 3397 8677
      3403 8670 3406 8671 3405 8668 3409 8669
      3409 8667 3412 8660 3425 8651 3426 8645
TIME...MOT...LOC 1859Z 257DEG 27KT 3417 8677 3391 8694 3366 8717

40/Sizemore

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE BIRMINGHAM AL
228 PM CDT FRI JUL 31 2020

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0154 PM     TSTM WND DMG     2 SW BARNEY             33.69N 87.18W
07/31/2020                   WALKER             AL   LAW ENFORCEMENT

            TREES WERE BLOWN DOWN ON UNDERWOOD FERRY
            ROAD.

&&

MAL

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE BIRMINGHAM AL
229 PM CDT FRI JUL 31 2020

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0124 PM     LIGHTNING        1 NNW MANCHESTER        33.91N 87.26W
07/31/2020                   WALKER             AL   LAW ENFORCEMENT

            A PERSON WAS STRUCK BY LIGHTNING. THEIR
            CONDITION WAS UNKNOWN.

&&

MAL

Special Weather Statement
National Weather Service Birmingham AL
229 PM CDT Fri Jul 31 2020

ALZ023-034-312000-
Bibb AL-Tuscaloosa AL-
229 PM CDT Fri Jul 31 2020

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHEASTERN TUSCALOOSA AND
NORTHERN BIBB COUNTIES UNTIL 300 PM CDT...

At 229 PM CDT, Doppler radar was tracking a strong thunderstorm near
Brookwood, or 13 miles east of Holt, moving east at 30 mph.

Half inch hail and winds in excess of 40 mph will be possible with
this storm.

Locations impacted include...
Lake View, Brookwood, Coaling, Vance, Woodstock, West Blocton,
Tannehill Ironworks State Park, Lake Wildwood, Abernant, Mercedes
Benz Of Alabama, North Bibb, Bucksville, East Brookwood, Camp Horne
B.S.A., Marvel, Green Pond, Caffee Junction, Hebron, I 20 Rest Area
Near Tuscaloosa and Cedar Cove.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

&&

LAT...LON 3310 8750 3339 8728 3339 8723 3337 8723
      3336 8720 3334 8720 3334 8718 3332 8718
      3332 8716 3331 8716 3331 8713 3329 8712
      3329 8709 3328 8707 3325 8706 3325 8703
      3317 8703 3316 8697 3311 8697
TIME...MOT...LOC 1929Z 264DEG 28KT 3326 8727

40/Sizemore

Special Weather Statement
National Weather Service Birmingham AL
257 PM CDT Fri Jul 31 2020

ALZ017-018-026-312045-
Etowah AL-St. Clair AL-Blount AL-
257 PM CDT Fri Jul 31 2020

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHEASTERN BLOUNT...WESTERN
ETOWAH AND NORTHWESTERN ST. CLAIR COUNTIES UNTIL 345 PM CDT...

At 256 PM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from near Snead to near Dallas. Movement was east at
30 mph.

Pea size hail and winds in excess of 40 mph will be possible with
these storms.

Locations impacted include...
Gadsden, Rainbow City, Oneonta, Attalla, Springville, Cleveland,
Dallas, Ashville, Sardis City, Locust Fork, Steele, Altoona, Snead,
Susan Moore, Walnut Grove, Reece City, Allgood, Fairview, Rosa and
County Line.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

To report severe weather, contact your nearest law enforcement
agency. They will relay your report to the National Weather Service
office in Birmingham.

&&

LAT...LON 3420 8605 3398 8605 3375 8638 3375 8654
      3377 8654 3377 8665 3382 8672 3418 8638
      3410 8630 3418 8619
TIME...MOT...LOC 1956Z 269DEG 24KT 3409 8637 3380 8661

40/Sizemore

Special Weather Statement
National Weather Service Birmingham AL
305 PM CDT Fri Jul 31 2020

ALZ025-034-312045-
Bibb AL-Shelby AL-
305 PM CDT Fri Jul 31 2020

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHWESTERN SHELBY AND BIBB
COUNTIES UNTIL 345 PM CDT...

At 305 PM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from near Tannehill Ironworks State Park to near
West Blocton to near Mertz. Movement was east at 30 mph.

Half inch hail and winds in excess of 40 mph will be possible with
these storms.

Locations impacted include...
Hoover, Alabaster, Pelham, Helena, Montevallo, Brent, Centreville,
Vance, Woodstock, West Blocton, Wilton, American Village, West
Centreville, Maylene, Oak Mountain Amphitheater, Ashby, Riverchase,
Brierfield Ironworks Park, Mertz and University Of Montevallo.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Frequent cloud to ground lightning is occurring with these storms.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

These storms may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

&&

LAT...LON 3300 8737 3301 8732 3311 8730 3313 8728
      3313 8720 3319 8720 3323 8715 3322 8710
      3325 8708 3325 8698 3333 8689 3333 8683
      3335 8683 3337 8678 3309 8681 3307 8683
      3307 8688 3301 8688 3291 8697 3289 8742
TIME...MOT...LOC 2005Z 262DEG 26KT 3322 8706 3308 8713 3291 8731

40/Sizemore