Special Weather Statement, NWS Birmingham, AL

Area Forecast Discussion
National Weather Service Birmingham AL
608 AM CDT Sat Apr 14 2018

.UPDATE...
For 12Z Aviation.

&&

.SHORT TERM...
Today through Sunday.

Confidence continues to increase in the threat for severe storms
this afternoon into tonight. Models have been trending slightly
slower and more toward a neutral and eventually negative tilt with
the upper-level trough as it moves toward the Mississippi River
Valley. These small changes should result in lower surface pressures
along the cold front with stronger backing of surface winds as a
QLCS approaches from the west. The slower timing should also allow
SBCAPE values to increase into the range of 1500-2500 J/kg across
the western half of Alabama before storms arrive. A QLCS with a
sizable damaging wind and tornado threat appears likely particularly
west of a line from Gadsden to Montgomery. A couple of strong
tornadoes (EF2-EF3) cannot be ruled out along and northwest of a
line from Demopolis to Birmingham, where forecast hodographs
indicate 0-1km shear of 30-40kt with clockwise curvature. This
potential may be associated with a couple of isolated supercells
ahead of or embedded within the QLCS. The threat should gradually
diminish across our eastern areas as the convective line loses
forward momentum and moves into weaker instability during the
evening and overnight hours. The severe threat will probably end
around 2 AM in our southeastern counties.

The passage of a cold front will bring cooler conditions for Sunday.
Rainfall should exit into Georgia during the morning hours, leading
to a somewhat breezy and cool afternoon.

87/Grantham

.LONG TERM...
Sunday Night through Saturday

Drying conditions will be in place Sunday night as cold air
advection again returns to the area. Temperatures will be in the 30s
and low 40s again with the coldest temperatures in the north. Lows
on Tuesday morning will be chilly as well with 30s and 40s possible.
Will need to watch the trends for frost potential each morning, but
right now Tuesday morning looks to be the better chance with lighter
winds.

An extended period of dry and tranquil weather is expected through
the upcoming workweek. The only slight chance of rain may come
Wednesday afternoon and evening as a moisture-starved front moves
through. Models are indicating a little bit more moisture now, so
will stick with 20 to 30 PoPs. Our next weather system should arrive
the following weekend. Models are not as impressive with this
system, but it will be one to watch as we get closer to the time
frame.

16

&&

.AVIATION...
12Z TAF Discussion.

Deteriorating conditions over the next 6 to 12 hours from west to
east as the line of showers and storms work into the area. Plenty
of moisture around the morning has led to mainly MVFR cigs across
the north with IFR at TOI. Timing of this line of showers and
storms is a little tricky but gave it the best shot. Winds will be
strong ahead of the line as well as the line itself. Additional
tweaks will be done to the TAFS as the line gets closer.
Improvement really is not expected until 24 hours later. There
could be a window this afternoon in MGM and TOI that cigs rise to
VFR but this would only allow for additional heating and stronger
storms this afternoon and evening.

16

&&

.FIRE WEATHER...

Showers and storms will slide through the area today, tonight, and
Sunday morning. Strong to severe storms are possible during the
afternoon and evening as the system progresses from west to east.
Drier Monday and Tuesday. There are no fire weather concerns at this
time.

&&

.PRELIMINARY POINT TEMPS/POPS...
Gadsden     80  54  59  37  60 /  80 100  50  10   0
Anniston    81  56  61  37  60 /  60 100  60  10   0
Birmingham  79  53  60  40  62 / 100 100  30   0   0
Tuscaloosa  77  50  61  39  64 / 100 100  10   0   0
Calera      79  52  61  39  62 /  90 100  30   0   0
Auburn      82  60  62  40  61 /  20 100  90   0   0
Montgomery  83  55  64  40  65 /  60 100  50   0   0
Troy        83  57  64  41  65 /  30 100  70   0   0

&&

.BMX WATCHES/WARNINGS/ADVISORIES/...
Flash Flood Watch through late tonight for the following
counties: Autauga...Bibb...Blount...Chilton...Dallas...Fayette...
Greene...Hale...Jefferson...Lamar...Lowndes...Marengo...Marion...
Perry...Pickens...Shelby...Sumter...Tuscaloosa...Walker...
Winston.

&&

Hazardous Weather Outlook
National Weather Service Birmingham AL
422 AM CDT Sat Apr 14 2018

ALZ011>015-017>050-151230-
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-
422 AM CDT Sat Apr 14 2018

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

.DAY ONE...Today and Tonight.

Severe storms are likely today into tonight across the forecast area.
The highest threat appears to be along and west of a line from
Montgomery to Gadsden, with a lower threat to the east. The threat
will begin around 11 AM in the West and continue until 2 AM Sunday in
the Southeast. Damaging winds and tornadoes will be the main threats,
and a couple of stronger tornadoes cannot be ruled out along and
northwest of a line from Demopolis to Birmingham.

Rainfall amounts of 3 to 4 inches could lead to isolated flash
flooding this afternoon into tonight. The best chance of flash
flooding will generally be across the western half of the area, or
along and west of the Interstate 65 corridor.

.DAYS TWO THROUGH SEVEN...Sunday through Friday.

Due to heavy rainfall, minor river flooding is expected Sunday
through Wednesday in the Tombigbee and Sucarnoochee River basins.

.SPOTTER INFORMATION STATEMENT...

Activation of storm spotters and emergency management may be needed
from late this morning into early Sunday morning.

Special Weather Statement
National Weather Service Birmingham AL
737 AM CDT SAT APR 14 2018

ALZ011-141315-
Marion AL-
737 AM CDT SAT APR 14 2018

...SIGNIFICANT WEATHER ADVISORY FOR MARION COUNTY UNTIL 815 AM CDT...

At 737 AM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from near Littleville to near Hackleburg to Detroit.
Movement was east at 35 mph.

Winds in excess of 40 mph will be possible with these storms.

Locations impacted include...
Hamilton, Winfield, Haleyville, Guin, Hackleburg, Brilliant, Gu-
Win, Brinn, Weston, Lake Buttahatchee, Bear Creek, Twin, Tucker,
Tessner, Pearces Mill, Rankin Fite Airport, Upper Bear Creek
Reservoir, Byrd, Marion County Public Lake and Piney Grove.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

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.

&&

LAT...LON 3422 8796 3431 8790 3430 8763 3400 8764
      3394 8772 3395 8795 3402 8795 3402 8799
      3405 8799 3406 8821
TIME...MOT...LOC 1237Z 267DEG 29KT 3461 8765 3423 8788 3402 8819

JH/05