Special Weather Statement, NWS Birmingham, AL

Area Forecast Discussion
National Weather Service Birmingham AL
115 PM CDT Tue Jul 9 2019

.UPDATE...
For 18Z Aviation.

&&

.SHORT TERM...
Through tonight.

The heat is on for most locations as of noon, with temperatures in
the low to mid 90s and very humid dewpoints in the low to mid 70s.
Heat indices have already risen above Heat Advisory criteria in
Tuscaloosa and Montgomery, hitting 106 and 107 degrees. At this
time, we're not planning on extending the area of the Heat
Advisory, and will remain across roughly the western half of
Central Alabama through 7pm.

Meanwhile, convection is developing along the NW periphery of the
trough/area of low pressure centered over southern Georgia and
the Florida Panhandle. This is the same area of low pressure that
the National Hurricane Center will be monitoring as it moves into
the Gulf of Mexico. The convection is developing within a
convergence zone as was mentioned in the previous discussion this
morning. The 12Z KBMX sounding this morning indicated much warmer
conditions aloft today than yesterday due to the upper height
rises and 592 decameter upper ridge centered over much of the
southeast. Even though mid-level lapse rates are weak due to the
higher temperatures aloft, conditions at the surface are very
unstable. RAP analysis indicates SBCAPE values of 4000-4500 J/KG
across our southern tier of counties where the most showers and
storms are expected to develop. In addition, microburst composite
parameters are higher today than they have been over the past
several days mostly due to drier air aloft. Therefore, we'll have
to keep a close watch on these storms this afternoon, as Troy
measured a wind gust of 37 knots with a storm that wasn't able to
get very tall or organized on radar. In addition, torrential
downpours could lead to some localized flooding and ponding in
isolated locations as some storms will be training at times as
they move from northeast to southwest this afternoon. We'll expect
at least scattered storms to persist in areas along and south of
the I-85 corridor through late this evening.

56/GDG

.LONG TERM...
/Updated at 0348 AM CDT Tue Jul 09 2019/
Wednesday through Tuesday.

By Wednesday the low pressure system is situated to our south and
has just entered the Gulf of Mexico. As the low drifts southwestward
into the western Gulf, upper level ridging will amplify over our
area. Afternoon thunderstorm activity won't be quite as prominent as
we have seen in previous days. The best chances will be in our
southeast counties due to more of an influence from the exiting low
pressure. Temperatures will are expected to reach the mid 90's
Wednesday afternoon. Heat indices have the potential to reach at or
above 105 degrees particularly in areas of southern and southwest
Central Alabama.

An upper level trough and associated surface low pressure system
will move into the Great Lakes region on Wednesday afternoon. A
frontal boundary associated with this upper level system will push
southeast into the northern Mississippi Valley region Wednesday
night. By Thursday, the surface front will have entered the northern
part of our CWA increasing rain chances. While temperatures are
still expected to be in the low/mid 90's with mid 70-degree
dewpoints, cloud cover from increasing rain chances could prevent
heat advisory criteria from being met. I will continue to mention
heating impacts in the HWO as there is still some uncertainty. The
low pressure system in the Gulf is expected to become a tropical
disturbance by the end of this week. There is still plenty of
uncertainty with regards to timing and track. Guidance has struggled
with the handling of the frontal boundary approaching from the north
and the interaction with the low in the Gulf. At this point, most
guidance seems to be tracking the low more westward. Either way, an
increase in tropical moisture from this system will allow for an
increase in shower and thunderstorm activity for much of Thursday,
Friday and Saturday. The forecast for the remainder of the period
solely depends on the evolution of this low pressure system. At this
time I have capped PoPs at 30% for Sunday afternoon and gradually
trending down to the end of the period.

&&

.AVIATION...
18Z TAF Discussion.

Diurnal convection has already started today. The best coverage
will be across generally along and south of the I-85 corridor.
I have TSRA mentioned at MGM/TOI at times this afternoon into the
evening to account for this. I also have a mention at ASN/ANB with
still scattered coverage possible. Otherwise, TCL/EET/BHM should
remain VFR generally with some afternoon fair weather cumulus.
Since we have already had some heavy rain at TOI, I have included
an initial MVFR fog mention for late tonight.

08

&&

.FIRE WEATHER...

Expect lower chances for showers and storms across the north and
west through Wednesday. However, scattered to numerous showers
and storms can be expected in the south and east during mainly the
afternoon hours. Relative humidity values should bottom out in
the 40 to 50 percent range during the afternoon hours before the
overnight recovery. Showers and storms will remain in the forecast
for good portion of the forecast period.

&&

.PRELIMINARY POINT TEMPS/POPS...
Gadsden     72  92  73  91  72 /  20  30  20  50  30
Anniston    73  91  74  90  73 /  30  30  20  50  30
Birmingham  76  94  75  93  74 /  20  30  20  50  30
Tuscaloosa  76  96  76  94  74 /  10  30  20  50  30
Calera      74  92  74  92  73 /  20  30  20  50  30
Auburn      75  90  74  88  73 /  40  50  30  50  40
Montgomery  75  95  76  92  74 /  40  40  30  50  40
Troy        74  92  74  90  73 /  40  50  30  60  40

&&

.BMX WATCHES/WARNINGS/ADVISORIES/...
Heat Advisory until 7 PM CDT this evening for the following
counties: Autauga...Bibb...Blount...Chilton...Coosa...Dallas...
Elmore...Fayette...Greene...Hale...Jefferson...Lamar...Lowndes...
Marengo...Marion...Montgomery...Perry...Pickens...Shelby...St.
Clair...Sumter...Talladega...Tuscaloosa...Walker...Winston.

&&

Hazardous Weather Outlook
National Weather Service Birmingham AL
342 AM CDT Tue Jul 9 2019

ALZ011>015-017>050-101145-
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-
342 AM CDT Tue Jul 9 2019

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

.DAY ONE...Today and Tonight.

Heat indices will exceed 105 degrees this afternoon for counties
along and west of Blount to Talladega to Montgomery line.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

Heat indices will be near or above 105 degrees again on Wednesday
and Thursday afternoons. Counties along and west of Blount to
Talladega to Montgomery line will experience the greatest heat due
to the temperature and humidity combination. All other locations will
experience heat indices in the lower 100s.

.SPOTTER INFORMATION STATEMENT...

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

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