Tornadoes and Flash Flooding in Alabama, February 5 to 6, 2020

Area Forecast Discussion
National Weather Service Birmingham AL
1236 PM CST Wed Feb 5 2020

.UPDATE...
Afternoon Update.

&&

.SYNOPSIS...

Fast southwest flow aloft was prevalent over the area early this
afternoon with a deep longwave positive-tilted trough to our west
extending from the High Plains southwest into New Mexico. Upper-
level ridging was positioned well to our southeast off the
Atlantic coast.

Toward the surface, a stationary front extended from near Lake
Charles Louisiana northeast to near Knoxville Tennessee. A surface
low was positioned over central Louisiana while surface high
pressure was positioned well to our southeast over the Southwest
Atlantic Basin.

05

&&

.SHORT TERM...
/Updated at 1208 PM CST Wed Feb 05 2020/

Today through Thursday afternoon.

We continue to highlight a risk of strong to severe storms later
this afternoon, through the overnight hours and into Thursday
morning as a storm system moves from west to east across the area.
The strongest storms will be capable of producing damaging winds
to 60 mph, small hail and a few tornadoes. Additionally, a
prolonged period of moderate to heavy rain coupled with recent
moist ground conditions will support localized flash flooding,
especially in urbanized, low-lying and poor drainage areas.

At this time, the morning showers and storms across our northwest
have quickly lifted north into the Tennessee Valley while a
relative lull was in place across much of our forecast area.
Deeper convection was ongoing along the Central Gulf Coast region
and expect this activity to continue to push northeast into our
southern and southeast counties later this afternoon and into
early evening.

Expect the surface low over Louisiana to ride northeast along the
stationary front this afternoon while a series of impulses aloft
move across the area from the southwest. The better forcing and
dynamics will be in close proximity to the surface low lifting
northeast out of Mississippi later this afternoon and into the
evening across our western counties, however, the extent and
magnitude of this risk is highly dependent on available
instability which may be hampered to an extent by the ongoing deep
convection to our south.

This evening and overnight expect upper level forcing and support
to increase as the upper trough approaches from the west and more
organized convection is forecast to our west, gradually becoming
more linear with time over Mississippi and approaching the area
from the west as we move through the overnight hours and into
Thursday morning.

With the forced linear convection and potential isolated
convection ahead of it progressing east with time Thursday
morning, expect higher instability values potentially to reside
across our southern and southeast counties where the potential
will be best for the stronger activity. Again, the extent and
magnitude of severe weather potential will largely be governed by
the available instability. The dynamical forcing and support will
be favorable for severe weather as the Low Level Jet develops this
evening and intensifies overnight through Thursday morning as it
pushes east across our central and eastern counties.

Southerly low-level winds will become southwest later tonight and
into the day Thursday followed by a more abrupt shift to the west
and eventually northwest as a cold front arrives and pushes east
across the area. With few breaks in the clouds expected, the
destabilization will largely be dictated by low-level warm air
advection and continued positive moisture advection from the south
while height falls and cooling aloft will result as the upper
level trough nears from the west. The instability realization
remains the primary uncertainty in the forecast as overall the
area will be in a favorable position with wind shear, jet
structures in the low, mid and upper levels and forcing with
steepening lapse rates aloft with the approach of the upper
trough.

Convection will gradually taper off from west to east through the
morning hours Thursday as cooler air filters in from the
northwest. Lingering low clouds with rain showers are expected
across much of the area through midday Thursday as drier air aloft
will be slow to arrive behind the departing trough as it takes on
a more negative tilt and swings northeast over the Carolinas into
the Mid Atlantic Region.

05

.LONG TERM...
/Updated at 0320 AM CST Wed Feb 05 2020/

Thursday Night through Through Tuesday.

As we progress into Thursday night the system will begin to exit the
area. Still going to have some lingering rain that will be occurring
post-frontal, with the best chances in the east through the
overnight hours. Rain will be shifting east through the night and
should exit the region by sunrise. Will keep precipitation as liquid
through the period.

Colder and dry on Friday with the wrap around cloud cover from the
upper level system moving through. The next system will move quickly
into the region on Saturday and bring a chance of rain by the
afternoon and into the evening hours. This system moves out and then
the next system moves in Monday from the west as a front, but will
stall out by Tuesday morning across the north, before lifting slowly
northward on Tuesday. Models are indicating that this front may sit
across the north for several days and may become a flooding issue
here. Much more on this as the system draws closer. Lows will be in
the 30s and 40s through the weekend and then the 40s and 50s by
Monday and Tuesday.  Highs will be in the 50s to low 60s through the
weekend and then the 60s and 70s by Tuesday.

16

&&

.AVIATION...
18Z TAF Discussion.

Expect continued deteriorating flying conditions through this
afternoon and tonight as a storm system approaches from the west.
Cloud bases will range from MVFR to IFR with conditions worsening
from west to east later this afternoon and through the overnight
hours. SHRA with increasing potential for TSRA will expand from
west to east across the area from this afternoon through the
overnight and into early in the day Thursday. Strong to severe
storms are possible that will be capable of producing wind gusts
to 60 kts along with frequent lightning and small hail.

Low level winds will shift from the south this afternoon at 10-20
kts with breezy conditions to the southwest overnight 5-15 kts
and remaining breezy at times. Increasing wind shear will support
LLWS conditions generally after 03Z especially across the central
and eastern terminals with the intensifying Low-Level Jet
overnight and into Thursday morning.

Expect gradual improvement toward the end of this cycle as much
of the TSRA pushes east of the terminal locations through the
morning hours Thursday though low CIGs and lingering SHRA are
expected. Low-level winds will become west to northwest toward
midday with speeds generally from 7-14 kts with gradual decreasing
LLWS conditions with time.

05

&&

.FIRE WEATHER...

Rain and thunderstorm chances will increase this afternoon and
evening with some strong to severe storms possible. Additionally,
locally heavy rainfall may result in some areas. This system will
affect the area through tomorrow evening followed by decreasing
coverage of showers overnight into early Friday morning. Another
system will bring more rain chances to the area Saturday afternoon
and evening. With the wet weather forecast, expect relative
humidity values to remain elevated through at least Friday
afternoon.

05

&&

.PRELIMINARY POINT TEMPS/POPS...
Gadsden     62  63  35  50  36 / 100  90  50  10  10
Anniston    63  65  36  52  36 / 100  90  60  10  10
Birmingham  61  62  36  52  40 / 100  90  40  10  10
Tuscaloosa  57  57  36  55  40 /  90  80  20   0  10
Calera      62  62  35  52  38 / 100  90  40  10  10
Auburn      64  67  38  51  37 / 100 100  80  10   0
Montgomery  66  68  38  55  39 / 100 100  50   0   0
Troy        66  70  38  55  38 / 100 100  60   0   0

&&

.BMX WATCHES/WARNINGS/ADVISORIES/...
Flash Flood Watch through Thursday afternoon for the following
counties: Autauga...Barbour...Bibb...Blount...Bullock...
Calhoun...Chambers...Cherokee...Chilton...Clay...Cleburne...
Coosa...Dallas...Elmore...Etowah...Jefferson...Lee...Lowndes...
Macon...Montgomery...Perry...Pike...Randolph...Russell...
Shelby...St. Clair...Talladega...Tallapoosa.

&&

Hazardous Weather Outlook
National Weather Service Birmingham AL
1059 AM CST Wed Feb 5 2020

ALZ011>015-017>050-062000-
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-
1059 AM CST Wed Feb 5 2020

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

.DAY ONE...Outlook through Tonight.

Strong to severe thunderstorms are possible this afternoon through
tonight across Central Alabama. Tornadoes, damaging winds up to 70
mph, and up to golf ball size hail are the primary threats.

Periods of moderate to heavy rainfall is expected this afternoon
through tonight. This could lead to flooding of low lying or poor
drainage areas, and isolated flash flooding. The best chances of
flooding will be mainly east of a line from Oneonta to Birmingham to
Marion. Total rainfall amounts into tomorrow afternoon will generally
be two to four inches, with locally higher amounts.

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

Strong to severe thunderstorms are possible into Thursday morning
Damaging winds up to 60 mph and a brief tornado are the primary
threats.

Moderate to heavy rainfall is expected to persist into Thursday
afternoon. This could lead to flooding of low lying or poor drainage
areas, and isolated flash flooding. The best chances during this
time will likely remain along and south of a line from Lafayette to
Montgomery.

Expected rains through Thursday afternoon will allow for rises
across Catoma Creek, as well as the Tombigbee and Black Warrior
River basins. Minor flooding is forecast to occur by Friday and last
through the weekend for some locations. Please refer to river
statements for specific details.

.SPOTTER INFORMATION STATEMENT...

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

08

Special Weather Statement
National Weather Service Birmingham AL
128 PM CST Wed Feb 5 2020

ALZ032-033-052000-
Hale AL-Perry AL-
128 PM CST Wed Feb 5 2020

...SIGNIFICANT WEATHER ADVISORY FOR NORTHWESTERN PERRY AND
SOUTHEASTERN HALE COUNTIES UNTIL 200 PM CST...

At 128 PM CST, Doppler radar was tracking a strong thunderstorm over
Newbern, or 7 miles north of Uniontown, moving northeast at 45 mph.

Half inch hail and wind gusts up to 40 mph will be possible with
this storm.

Locations impacted include...
Marion, Newbern, Morgan Springs and Folsom.

LAT...LON 3248 8751 3256 8762 3281 8745 3270 8723
TIME...MOT...LOC 1928Z 216DEG 41KT 3255 8753

89^GSatterwhite

Special Weather Statement
National Weather Service Birmingham AL
141 PM CST Wed Feb 5 2020

ALZ032-033-039-052015-
Hale AL-Marengo AL-Perry AL-
141 PM CST Wed Feb 5 2020

...SIGNIFICANT WEATHER ADVISORY FOR NORTHEASTERN MARENGO...
NORTHWESTERN PERRY AND CENTRAL HALE COUNTIES UNTIL 215 PM CST...

At 140 PM CST, Doppler radar was tracking a strong thunderstorm near
Faunsdale, or 9 miles east of Demopolis, moving northeast at 60 mph.

Half inch hail and wind gusts up to 40 mph will be possible with
this storm.

Locations impacted include...
Demopolis, Marion, Greensboro, Uniontown, Newbern, Faunsdale, Dayton,
Greensboro Municipal Airport, Arcola, Heiberger, Old Spring Hill,
Morgan Springs, Gallion, Folsom, Phipps, Wateroak, Cedarville,
Laneville and Ellards.

LAT...LON 3250 8789 3254 8782 3252 8782 3258 8779
      3259 8774 3261 8775 3261 8780 3262 8779
      3264 8775 3266 8775 3265 8777 3294 8753
      3290 8742 3288 8742 3286 8732 3283 8732
      3281 8718 3233 8764
TIME...MOT...LOC 1940Z 217DEG 54KT 3249 8768

89^GSatterwhite