Special Weather Statement, NWS Birmingham, AL

Area Forecast Discussion
National Weather Service Birmingham AL
1247 PM CDT Thu Aug 8 2019

.UPDATE...
For 18Z Aviation.

&&

.SHORT TERM...
/Updated at 0413 AM CDT Thu Aug 08 2019/

Today and Tonight.

For a fairly quiet morning, it has been quite active in regards to
forecast impacts across the area. First in the wake of the rain from
yesterday, dense fog has developed across the northern counties.
Therefore have added in a dense fog advisory through 9 am. Now
attention shifts to the heat. Temperatures are expected to climb
quickly and dewpoints will not mix out before the heat advisory
criteria, heat index of 105 degrees, is met. Looks like the warmest
locations will be in the south from Pickens county through Russell
county. Areas in the northwest will also get close to, or just
exceed criteria, so included Shelby and Jefferson and counties to
the west as well.

As we shift into the afternoon, another impulse will slide into the
west. With the very warm temperatures and plenty of instability, fat
cape profiles and dry air aloft, straight line wind damage will
be possible. Will be including a marginal risk for severe weather
across the west through 9 pm. Will do an update this morning once
the sounding comes in to adjust the risk area if needed. Activity
dissipates this evening and then we will watch another possible
MCS develop to our NW and slide into the area, as we remain in the
northwest flow. Looks like the bulk of the activity will move in
after sunrise but the northwest may see activity as early as 4 am.
Highs today will be in the mid to upper 90s and lows in the 70s.

16

.LONG TERM...
/Updated at 0413 AM CDT Thu Aug 08 2019/

Friday through Wednesday.

The northwest flow MCS train continues on Friday as an upper low
near James Bay moves into Quebec and a mid-level anticyclone remains
over Texas. Meanwhile a cold front will be located over the Ohio
Valley with a pre-frontal trough over the Mid-South. One shortwave
could trigger some showers/storms across the north during the
morning, but CAMs are focusing more on a shortwave/MCV further west
over Arkansas with convection/a potential MCS moving into/developing
across the western half of the state by afternoon. Assuming
convection holds off until afternoon, heat indices will likely reach
105 degrees across the area by midday, and an extension to the heat
advisory may become necessary. Will have to monitor again for the
potential for an isolated severe storm. However, soundings will be
transitioning to more tropical-like profiles as PWATs increase,
resulting in less dry air aloft/DCAPE and weaker lapse rates, which
could potentially mean a shifting threat from damaging winds to
still gusty but sub-severe winds and locally heavy rainfall. Will
hold off on any severe mention in the HWO due to this uncertainty,
while continuing to mention heat impacts. Another MCS could impact
the area sometime overnight Friday night into Saturday morning, but
confidence in this remains low. Current thinking is that cold pool
from this MCS will keep heat indices below criteria on Saturday but
will continue to monitor.

Flow aloft will transition to northerly Saturday afternoon/Saturday
night as the deep upper low/trough push eastward towards the
Canadian Maritimes and the upper ridge begins to build eastward.
This should allow for some drier air aloft to work into the area,
which along with the increased subsidence associated with the ridge
should have a generally suppressive effect on convection Sunday into
early next week. There are still some differences in the guidance as
the ECMWF continues to have a much stronger push of drier air both
aloft and at the surface with lower dew points, potentially due to a
stronger wave of low pressure developing along the front due to
convective feedbacks. Meanwhile in the GFS solution moisture gets
trapped under the ridge, which could allow for isolated to widely
scattered showers/storms with any weak disturbances moving through,
and much higher dew points. Either solution results in very hot
conditions with highs in the mid to upper 90s, and a few 100F
temperature readings are not out of the question. But the difference
in dew points will have a big impact on potential heat indices. A
compromise solution yields heat indices reaching 105 in many areas,
and will continue to advertise heat impacts in the HWO. Rain chances
will begin to increase by mid-week ahead of another approaching cold
front.

32/Davis

&&

.AVIATION...
18Z TAF Discussion.

Scattered storms will continue to develop through the afternoon,
with the best coverage along/south of the I-22/Hwy 280 corridor.
Therefore, have TEMPO TSRA at most sites for several hours, with
the exception of ASN/ANB (VCTS). Coverage will decrease thru the
evening as most of the activity gradually shifts southward. Some
patchy fog is possible late tonight, so may need to refine
visibility forecasts for some locations in future forecasts.

19

&&

.FIRE WEATHER...

Additional development of showers and thunderstorms by this
afternoon is expected across the entire area. Best chances will
be in the south and west as another storm complex rolls through
during the afternoon. On and off shower and thunderstorms chances
continue Friday and Saturday. No critical fire weather conditions
are anticipated due to a humid air mass, however portions of
central Alabama will remain in slight drought conditions.

&&

.PRELIMINARY POINT TEMPS/POPS...
Gadsden     71  91  71  92  69 /  20  40  40  40  10
Anniston    72  92  73  91  71 /  20  30  40  40  10
Birmingham  74  93  74  93  73 /  30  40  40  40  10
Tuscaloosa  74  94  75  93  74 /  20  60  40  50  20
Calera      72  93  72  92  71 /  30  40  40  50  10
Auburn      73  92  74  92  73 /  30  40  30  40  20
Montgomery  74  95  75  94  74 /  30  50  30  50  20
Troy        73  94  74  92  73 /  30  50  30  50  20

&&

.BMX WATCHES/WARNINGS/ADVISORIES/...
Heat Advisory until 9 PM CDT this evening for the following
counties: Autauga...Barbour...Bibb...Bullock...Chilton...
Dallas...Elmore...Greene...Hale...Jefferson...Lowndes...Macon...
Marengo...Montgomery...Perry...Pickens...Pike...Russell...
Shelby...Sumter...Tuscaloosa.

&&

Hazardous Weather Outlook
National Weather Service Birmingham AL
120 PM CDT Thu Aug 8 2019

ALZ011>015-017>050-092130-
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-
120 PM CDT Thu Aug 8 2019

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

.DAY ONE...This Afternoon and Tonight.

Isolated severe storms are possible through 9 PM this evening,
mainly along and south of a line from Haleyville to Birmingham to
Phenix City. Damaging winds up to 60 mph will be the main threat.

Heat indices of 105 to 107 degrees are expected today along and
south of a Birmingham to Wetumpka to Phenix City line.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday.

Isolated severe storms are possible on Friday from noon to 9 PM
across all of Central Alabama. Damaging winds up to 60 mph will be
the main threat.

Hot and humid conditions with heat indices reaching or exceeding 105
degrees are possible on Friday and again Monday through Wednesday of
next week.

.SPOTTER INFORMATION STATEMENT...

Activation of storm spotters and emergency management may be needed
through this evening and again on Friday afternoon and evening.

Special Weather Statement
National Weather Service Birmingham AL
1217 PM CDT Thu Aug 8 2019

ALZ037-043-081745-
Tallapoosa AL-Elmore AL-
1217 PM CDT Thu Aug 8 2019

...SIGNIFICANT WEATHER ADVISORY FOR EAST CENTRAL ELMORE AND SOUTH
CENTRAL TALLAPOOSA COUNTIES UNTIL 1245 PM CDT...

At 1217 PM CDT, Doppler radar was tracking a strong thunderstorm over
Martin Dam, or 9 miles north of Tallassee, moving southeast at 15
mph.

Wind gusts around 40 mph will be possible with this storm.

Locations impacted include...
Tallassee, Southern Lake Martin, Martin Dam, Reeltown, Yates
Reservoir and Yates Dam.

LAT...LON 3267 8603 3273 8588 3264 8571 3254 8591
TIME...MOT...LOC 1717Z 305DEG 11KT 3267 8588

89^GSatterwhite

Special Weather Statement
National Weather Service Birmingham AL
103 PM CDT Thu Aug 8 2019

ALZ047-081830-
Lee AL-
103 PM CDT Thu Aug 8 2019

...SIGNIFICANT WEATHER ADVISORY FOR WESTERN LEE COUNTY UNTIL 130 PM
CDT...

At 103 PM CDT, Doppler radar was tracking a strong thunderstorm near
Auburn University, or near Auburn, moving east at 20 mph.

Wind gusts around 40 mph will be possible with this storm.

Locations impacted include...
Auburn, Opelika, Notasulga, Beauregard, Auburn University,
Loachapoka, Robert G. Pitts Airport, Chewacla State Park and Mount
Jefferson.

LAT...LON 3247 8537 3249 8544 3250 8544 3250 8545
      3256 8564 3271 8563 3271 8561 3272 8561
      3273 8532
TIME...MOT...LOC 1803Z 279DEG 17KT 3260 8557

89^GSatterwhite

Special Weather Statement
National Weather Service Birmingham AL
121 PM CDT Thu Aug 8 2019

ALZ047-048-081915-
Lee AL-Russell AL-
121 PM CDT Thu Aug 8 2019

...SIGNIFICANT WEATHER ADVISORY FOR LEE AND NORTHWESTERN RUSSELL
COUNTIES UNTIL 215 PM CDT...

At 120 PM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from near Oak Bowery to near Society Hill. Movement
was east at 20 mph.

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

Locations impacted include...
Auburn, Opelika, Smiths, Smiths Station, Beulah, Beans Mill, Ladonia,
Beauregard, Bleecker, Griffen Mill, Robert G. Pitts Airport, Monterey
Heights, Chewacla State Park, Ladonia Sports Complex, Marvyn, Phenix
Drag Strip, Mount Jefferson and Parkmanville.

LAT...LON 3238 8543 3250 8544 3250 8550 3273 8547
      3274 8511 3271 8512 3269 8512 3265 8509
      3265 8511 3263 8509 3259 8508 3237 8507
TIME...MOT...LOC 1820Z 268DEG 18KT 3272 8542 3249 8544

89^GSatterwhite