Special Weather Statement, NWS Birmingham, AL

Area Forecast Discussion
National Weather Service Birmingham AL
1254 PM CDT Thu May 24 2018

.UPDATE...
For 18Z Aviation.

&&

.SHORT TERM...
Today and Tonight.

The overall pattern has not changed much over the past 24 hours with
a low level circulation over central Georgia and a trof axis
extending westward into south Alabama. Light winds and minimal cloud
cover has produced conditions conducive for fog this morning. A few
places are already below one-half mile across west Alabama, and a
dense fog advisory may become necessary. Precipitable water values
are still above normal with values around 1.75 inches. The majority
of the convection today will be near and south of the low level trof
axis, but thunderstorms possible anywhere this afternoon due to
higher than normal PW's and little or no capping inversion.
Convection will wane after the loss of daytime heating.

58/rose

.LONG TERM...
Friday through Wednesday.

Trailing vorticity from a shortwave moving through the Midwest
will result in falling 500mb heights on Friday as an upper-level
trough strengthens over the Gulf and adjacent states. A weak
frontal boundary will have dissipated, allowing moisture to return
northward. Cyclonic mid-level flow, daytime heating, and the moist
air mass will result in numerous showers and storms that will be
maximized during the afternoon hours.

Upper-level troughing over the region will be a persistent feature
of the forecast period due to a tilted omega block pattern at
500mb with ridging over the Plains flanked by the Gulf trough and
a closed low over the Great Basin. A developing surface low near
the Yucatan will be lifted northward by the trough. NHC indicates
that this low is likely to develop into a tropical or subtropical
depression. The GFS remains east of the guidance consensus but has
trended westward closer to the other model guidance. Will continue
to rely on the ECMWF which has support from the NAM and Canadian
as well as its ensembles. The ECMWF has trended slower in the last
couple of runs. Shear from the trough will prevent significant
strengthening, with the main impacts for the Gulf states
continuing to be heavy rainfall and flooding, as is often the
concern with slow-moving weak tropical systems. Saturday looks to
be the "least wet" day of the holiday weekend, as the low and
deep tropical moisture remain south of the area, but there will
still be enough forcing from the trough and moisture to warrant
likely PoPs for diurnally enhanced convection. By Sunday,
southerly flow aloft will over-run strengthening low-level
southeasterly flow likely resulting in more widespread/steady
tropical rains lifting up from the southeast. This will result in
cooler high temperatures, and will only mention a slight chance of
embedded thunder due to limited instability.

Sticking with the ECMWF solution, the low pressure system will
become vertically stacked and stall out somewhere just southwest
of the forecast area for the first half of next week. Continued
850mb moisture transport east of the low will result in wet
conditions continuing across the area, modulated by any patches of
dry air aloft that wrap around the system. Rainfall will likely
contract closer to the center at night while expanding in coverage
through the day. Greatest potential for flooding will be closest
to where the low stalls, but confidence is low exactly where that
will be. There will likely be some hefty rainfall totals somewhere
across the Gulf states and especially near the coast, but
confidence in placement is low. Will continue to highlight the
flooding potential in the HWO. More organized flooding chances
look to hold off until Sunday, but isolated flash flooding remains
possible Friday and Saturday due to the moist air mass and weak
flow through the column.

32/Davis

&&

.AVIATION...
18Z TAF Discussion.

Similar to yesterday scattered to numerous showers and
thunderstorms will persist through the afternoon hours. For all
sites except KANB and KASN added in a TEMPO group to account for a
greater likelihood of thunderstorm activity associated with peak
heating. Activity should taper off around 00Z this evening due to
loss of daytime heating. Due to rainfall at most sites this
afternoon and continuity did mention the possibility of fog/low
clouds developing with reduced visibilities tomorrow morning.
Further amendments could be made later in the period.

07/Wyatt

&&

.FIRE WEATHER...

A moist pattern is expected over the next seven days and should
result in daily rain chances. Patchy fog and low clouds will be
possible each morning particularly where rainfall occurs during
the prior afternoon and evening.

&&

.PRELIMINARY POINT TEMPS/POPS...
Gadsden     67  83  66  84  66 /  20  50  40  60  40
Anniston    68  83  66  84  66 /  20  60  40  60  40
Birmingham  69  85  69  85  69 /  20  60  40  60  40
Tuscaloosa  69  86  68  86  68 /  20  70  40  60  40
Calera      68  84  67  84  67 /  20  60  50  60  40
Auburn      68  81  67  81  67 /  50  60  50  60  40
Montgomery  69  86  68  85  69 /  40  70  50  60  40
Troy        68  85  68  84  68 /  50  70  50  60  50

&&

.BMX WATCHES/WARNINGS/ADVISORIES/...
None.

&&

Hazardous Weather Outlook
National Weather Service Birmingham AL
944 AM CDT Thu May 24 2018

ALZ011>015-017>050-251745-
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-
944 AM CDT Thu May 24 2018

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

.DAY ONE...Today and Tonight.

No hazardous weather is expected at this time.

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

A very moist air mass will continue across Central Alabama through
the weekend and into next week, and there is a potential for
localized areas of heavy rainfall each day. A tropical disturbance
moving northward across the Gulf of Mexico will bring an enhanced
threat for heavy rainfall Sunday through Wednesday.

.SPOTTER INFORMATION STATEMENT...

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

Special Weather Statement
National Weather Service Birmingham AL
208 PM CDT THU MAY 24 2018

ALZ033-241930-
Perry AL-
208 PM CDT THU MAY 24 2018

...SIGNIFICANT WEATHER ADVISORY FOR NORTHERN PERRY COUNTY UNTIL 230
PM CDT...

At 207 PM CDT, Doppler radar was tracking a strong thunderstorm over
Heiberger, or 9 miles north of Marion. This storm was nearly
stationary.

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

Locations impacted include...
Marion, Heiberger, Morgan Springs, Folsom and Ellards.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 3283 8742 3287 8742 3287 8732 3283 8732
      3283 8725 3274 8713 3261 8738 3277 8747
      3283 8747
TIME...MOT...LOC 1907Z 329DEG 2KT 3277 8732

25/Owen

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