Special Weather Statement, NWS Birmingham, AL

Area Forecast Discussion
National Weather Service Birmingham AL
902 AM CDT Mon Aug 2 2021

.UPDATE...
Morning Update.

&&

.SHORT TERM...
/Updated at 0902 AM CDT Mon Aug 02 2021/

Features of Interest.

A broad trough across much of the Midwest into the Ohio River
Valley while ridging is located over Northern Mexico into the
Desert Southwest. In the mid levels, a shortwave trough was
analyzed from sounding data over Central Arkansas with shortwave
ridging over the Central Tennessee Valley. The lower levels show
the persistent ridging off the Southeast U.S. Coast with the most
defined troughing along the Northeast and Mid Atlantic regions.

Toward the surface, a cold front extended across the southern
third of the forecast area while an area of low pressure was
analyzed near Shreveport, LA.

Hazard Assessment.

The wet microburst assessment yields a moderate risk across the
forecast area. This is primarily due to residual dry air aloft,
though the magnitude is less compared to yesterday. Conditions
aloft yesterday ended up greatly limiting convective development.
Today the magnitude of drier air is less and should permit more
development across the area.

Heavy rainfall may produce localized flooding in urban and poor
drainage areas with rain rates over one inch an hour.

Near Term.

Showers and thunderstorms associated with a mid level impulse will
continue to slowly move east-northeast around 30 mph out of East-
Central Mississippi and into Western Alabama now through late
morning. This activity has been slowly weakening with time and
that trend is expected to continue through late morning. Some
shower activity is expected to develop with time across our
southern counties, where instability values will be highest south
of the front.

05

05

Previous short-term discussion:
/Updated at 0318 AM CDT Mon Aug 02 2021/
Through Tuesday.

The main cold front is now along the US 80/I-85 corridor this
morning and will slowly slide south before stalling later today.
High pressure will slide into the area on Tuesday and push the front
a little bit further south by Tuesday afternoon. Rain chances will
be highly dependent on the exact placement of the front over the
next 2 days. At the same time a secondary front is sliding east
southeast into the TN Valley. This front is basically moisture
starved as the original front is not allowing any moisture to the
north. There have been a few echoes with it this morning, but do not
expect much. With these two features in place along with
temperatures in the 80s north to near 90 south rainfall has the
potential to be widespread south and isolated to scattered across
the north today. Activity will shift further south and east
tonight and Tuesday. A few stronger storms are possible in the
south but widespread severe weather is not expected and heat
indices will remain below 100 degrees in the south. Lows tonight
will be in the 60s for most areas with the southeast in the upper
60s to low 70s. A very big change to what we have been seeing.

16

.LONG TERM...
/Updated at 0318 AM CDT Mon Aug 02 2021/
Tuesday night through Sunday.

Central Alabama will remain under cyclonic flow aloft around the
base of an amplified trough over the eastern CONUS Tuesday night
through Wednesday, with some guidance indicating a closed low
developing over Kentucky. Isolated to scattered showers and storms
will probably be ongoing early Tuesday evening, weakening with
the loss of daytime heating. An inverted trough will move in from
the east ahead of a weak back door wedge front Tuesday night. A
small increase in winds and dew points could keep lows a little
milder in the eastern counties than would otherwise occur, but
still much more pleasant than recent nights. Will also keep a
slight chance of showers going overnight in the east with weak
convergence. On Wednesday, another shortwave rounds the base of
the trough with a continued convergence zone across the area.
However models continue to differ regarding how far west
sufficient moisture for convective development will make it into
the area as waves of low pressure ride along the stalled front to
our southeast. Highest rain chances will be in the southeast.

The eastern CONUS trough lifts out of the area Thursday with weak
shortwave ridging developing ahead of another shortwave over the
central CONUS. Chances of showers and storms will continue to
depend on how far west the axis of deep layer moisture along the
stalled front and possible weak surface low makes it, with
relatively highest chances southeast. A mid-level trough moves
through the area Friday and Saturday. Moisture with the actual
trough is limited with rain chances dependent on its interaction
with the moisture axis to our southeast. By Sunday the Bermuda
high begins to strengthen over the southeast CONUS with hot and
humid conditions returning. There will be some weaknesses in the
ridge with enough moisture for more typical scattered diurnal
convection to return.

32/Davis

&&

.AVIATION...
12Z TAF Discussion.

An MCS is moving through MS this morning and will move into
Central Alabama this morning and may provide TCL, EET, and MGM.
Have adjusted TAFs to account for the increase in coverage that
may occur now. There is a lower confidence that this activity will
hold together but it is possible. Additional showers and storms
will occur in the afternoon and into the evening. Look for
amendments through the day.

16

&&

.FIRE WEATHER...

Scattered to numerous showers and thunderstorms will develop
over Central Alabama again today with the highest chances in the
south. An overall decrease in rain chances can be expected
Tuesday through Friday, with the highest chances in the southeast
and very limited chances in the northwest. Low level moisture
remains very high through Monday with minimum RH values over 50
percent. Some drop is expected the remainder of the week but only
into the 40s. As is typical of the summer pattern, transport winds
remain rather light.

&&

.PRELIMINARY POINT TEMPS/POPS...
Gadsden     84  67  87  65  86 /  20  30  20  10  30
Anniston    85  68  86  67  85 /  30  40  30  20  40
Birmingham  84  68  87  67  88 /  50  30  20  10  20
Tuscaloosa  83  69  88  67  88 /  80  40  20  10  20
Calera      83  69  85  68  86 /  60  40  20  10  20
Auburn      86  70  83  69  84 /  80  60  60  30  50
Montgomery  87  72  87  70  88 /  90  70  50  20  40
Troy        90  71  85  69  88 / 100  70  60  30  50

&&

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

&&

Hazardous Weather Outlook
National Weather Service Birmingham AL
319 AM CDT Mon Aug 2 2021

ALZ011>015-017>050-031130-
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-
319 AM CDT Mon Aug 2 2021

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

.DAY ONE...Outlook through Tonight.

No hazardous weather is expected at this time.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Activation of storm spotters and emergency management is not
expected at this time.

Special Weather Statement
National Weather Service Birmingham AL
1137 AM CDT Mon Aug 2 2021

ALZ030>032-039-021715-
Greene AL-Hale AL-Sumter AL-Marengo AL-
1137 AM CDT Mon Aug 2 2021

...SIGNIFICANT WEATHER ADVISORY FOR NORTHERN MARENGO...SOUTHEASTERN
GREENE...SOUTHWESTERN HALE AND SOUTHEASTERN SUMTER COUNTIES UNTIL
1215 PM CDT...

At 1136 AM CDT, Doppler radar was tracking a strong thunderstorm near
Demopolis, moving northeast at 15 mph.

Winds in excess of 40 mph will be possible with this storm.

Locations impacted include...
Demopolis, Linden, Jefferson, Forkland, Faunsdale, Pin Hook, Duffys
Bend, Arcola, Dug Hill, Chickasaw State Park, U.S. 80 and AL 28, Old
Spring Hill, Belmont, Demopolis Lock And Dam, Gallion, McDowell,
Whitfield, Birdine, Cedarville and Laneville.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with this storm, and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.

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.

&&

LAT...LON 3269 8784 3255 8752 3247 8752 3229 8778
      3237 8817
TIME...MOT...LOC 1636Z 222DEG 13KT 3246 8788

86/Martin