Special Weather Statement, NWS Birmingham, AL

Area Forecast Discussion
National Weather Service Birmingham AL
749 PM CDT Thu Aug 31 2017

.UPDATE...
For 00Z Aviation.

&&

.SHORT TERM...

Risk for isolated tornadoes continues across our western and
central counties late this afternoon and into early this evening.

The post-tropical center of Harvey is now analyzed near Oxford, MS
with a synoptic scale warm front extending from the circulation
center east to between Tupelo and Columbus, MS and extends further
east into western Alabama to near Jasper in Walker County. The
pressure troughing has been the most evident indicator of this
feature for much of the day but a weak gradient is now showing up
in Theta-E analyses that indicates some change in temperature and
dew point along this boundary. Low level wind fields are starting
to show some vector differences along the boundary. Additionally,
a trough is now analyzed from east-central Mississippi south of
Columbus, MS that extends southeast into Sumter and Marengo
Counties and extends further south into interior southwest
Alabama. A convergence signature in the low level wind fields has
become evident with this feature over the past hour or two.

These features may help prolong a tornado threat across our west-
central and northwest counties over the next few hours as low-
level surface winds may become locally enhanced enough to support
rotation descending through the lower levels toward the surface.

As surface instability weakens with the loss of daytime heating
the overall trend of gradual weakening of convection is expected
despite an anticipated increase in wind shear across our west and
northwest counties as post-tropical Harvey continues moving across
north Mississippi into west-central Tennessee late tonight.

JH/05

Previous short-term discussion:
The post-tropical center of Harvey is now analyzed south of Tunica,
MS. A synoptic scale warm front was located via surface pressure
field analysis from the surface low center east to just south of
Tupelo, MS. Across the state of Mississippi, surface winds generally
shift across this front but as this feature extends into Alabama, it
is primarily defined by a pressure trough with little in the way of
a wind shift or change in the thermodynamic environment.

Sounding data along with upper air guidance suggests drier air aloft
is present in greater magnitude to the east and the north while
profiles are more moist to the south and the west.

Rotating storms remain likely across our south-central, southwest
and western counties with a limited tornado risk. While
conditions had become somewhat calmer in the short- term,
additional development across our south and west counties continue
to be monitored closely. Tornadoes remain possible as we remain
in the synoptically favored right front quadrant of a former
tropical cyclone.

Breaks in cloud cover continue across our eastern, southeast and
south-central counties and solar insolation continues to result in
surface heating that is increasing instability values. Wind shear is
most prominent off the surface at this time, supporting broad storm
rotation. Wind shear values will increase across our western and
northwest counties for the remainder of this afternoon and evening
as the remnants of Harvey move into western Tennessee.

Radar imagery indicates storms that we are closely watching in
Pickens, Perry and Marengo Counties with more activity to the
southwest. Our southwest and west-central counties continue to have
the greatest potential for rotating storms and possible tornadoes.

JH/05

.LONG TERM...

Rain chances will drop significantly for Friday as much drier air
aloft moves into the region around the southern periphery of
Harvey's remnant low. The weekend looks dry for most if not all
of our forecast area with the arrival of northwesterly flow. The
next chance of rain may not come until Tuesday as southerly flow
develops in advance of an approaching upper-level trough.

&&

.AVIATION...
00Z TAF Discussion.

The remnants of Harvey over north Mississippi will continue to
produce gusty low level winds, even overnight generally from the
south. This will help discourage fog development but low clouds
will continue to affect most sites. SHRA with a few TSRA will
remain possible overnight and into early on Friday before
conditions begin to improve through the day on Friday.

JH/05

&&

.FIRE WEATHER...

High rain chances are expected through tonight with tropical
moisture in place. A drying trend will follow for Friday and the
weekend. There are no fire weather concerns at this time.

&&

.PRELIMINARY POINT TEMPS/POPS...
Gadsden     69  80  60  81  60 /  90  50  20  10  10
Anniston    70  82  63  83  62 /  90  40  20  10  10
Birmingham  70  82  64  83  64 /  90  30  20  10  10
Tuscaloosa  70  84  66  86  64 /  90  20  10  10   0
Calera      70  82  65  85  65 /  90  20  10  10  10
Auburn      71  84  66  84  65 /  70  30  20  10  10
Montgomery  73  88  67  88  67 /  70  20  10  10  10
Troy        72  87  68  87  66 /  40  20  10  20  10

&&

.BMX WATCHES/WARNINGS/ADVISORIES/...
Wind Advisory until 4 PM CDT Friday for the following counties:
Blount...Calhoun...Cherokee...Etowah...Fayette...Jefferson...
Lamar...Marion...St. Clair...Walker...Winston.

&&

Hazardous Weather Outlook
National Weather Service Birmingham AL
1101 AM CDT Thu Aug 31 2017

ALZ011>015-017>050-011915-
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-
1101 AM CDT Thu Aug 31 2017

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

.DAY ONE...Outlook through Tonight.

The remnants of Harvey will approach Alabama and is expected to
bring a threat for brief tornadoes to the forecast area. The threat
could continue until 10 PM. The best chance for brief tornadoes
should generally be along and northwest of a line from Selma to
Clanton to Wedowee, though a brief tornado cannot be ruled out
farther south and east.

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

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Activation of storm spotters and emergency management may be needed
through tonight.

Special Weather Statement
National Weather Service Birmingham AL
541 PM CDT THU AUG 31 2017

ALZ031-032-039-312315-
Greene AL-Hale AL-Marengo AL-
541 PM CDT THU AUG 31 2017

...SIGNIFICANT WEATHER ADVISORY FOR NORTHWESTERN MARENGO...
SOUTHEASTERN GREENE AND SOUTHWESTERN HALE COUNTIES UNTIL 615 PM
CDT...

At 541 PM CDT, Doppler radar was tracking a strong thunderstorm near
Demopolis, moving northeast at 45 mph.

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

Locations impacted include...
Demopolis, Linden, Jefferson, Myrtlewood, Pin Hook, Duffys Bend,
Arcola, Chickasaw State Park, U.S. 80 and AL 28, Old Spring Hill,
Gallion, Birdine, Cedarville, Laneville, Demopolis Municipal Airport
and Demopolis Lock And Dam.

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

LAT...LON 3214 8804 3218 8801 3228 8802 3231 8798
      3231 8795 3228 8793 3231 8793 3237 8804
      3239 8804 3252 8792 3252 8784 3254 8787
      3258 8788 3274 8773 3255 8752 3253 8752
      3209 8804
TIME...MOT...LOC 2241Z 228DEG 37KT 3246 8782

75

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PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE BIRMINGHAM AL
811 PM CDT THU AUG 31 2017

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0709 PM     TSTM WND DMG     2 WSW EOLINE            32.99N 87.27W
08/31/2017                   BIBB               AL   EMERGENCY MNGR

            TREES AND POWER LINES DOWN ACROSS PORTIONS
            OF WARD SCHOOL ROAD, WEST EOLINE ROAD AND
            BEAR CREEK ROAD. POSSIBLE TORNADO. REPORT
            RELAYED BY SOCIAL MEDIA. LOCATION
            APPROXIMATE.

&&

JH/05

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