Special Weather Statement, NWS Birmingham, AL

Area Forecast Discussion
National Weather Service Birmingham AL
642 PM CDT Wed May 27 2020

.UPDATE...
For 00Z Aviation.

&&

.SHORT TERM...
/Updated at 0210 PM CDT Wed May 27 2020/

Today through Thursday.

Features:

An expansive upper low is positioned near Fort Smith, Arkansas
with a mid level disturbance swinging into the region from the
southwest. Tropical Storm Bertha developed earlier this morning
off the South Carolina Coastline and has since moved inland. A
stationary front extended from Western Wisconsin south into
Eastern Arkansas and through Western Louisiana. A surface low was
analyzed along the Mississippi Gulf Coast along a dissipating
stationary front that extended south across the Western Gulf of
Mexico.

Forecast:

A line of showers and thunderstorm activity was positioned from
near Jasper in Walker County south through Tuscaloosa and extended
southwest to near Selma in Dallas County and stretched further
south toward the Northern Gulf Coast.

Expect this activity to continue to move northeast this afternoon
and evening. Persistent cloud cover along with residual wedging
across our Eastern Counties will result in the convection
gradually decreasing in intensity as this activity moves into our
Eastern Counties this evening.

A few showers and storms may develop behind the line of storms
later this afternoon and through the evening, but the activity
will be more sparce in nature.

We have trimmed back the marginal risk area out of portions of our
northeast area. Otherwise, a few strong storms remain possible
with best potential across portions of our Southern and Central
Counties through this evening. The heaviest activity today will
be capable of producing strong winds, frequent lightning strikes
and torrential downpours. Localized ponding of water will be
possible in urban and poor-drainage areas.

Expect this activity to push northeast across the rest of the
forecast area this evening with gradual weakening in intensity
with time. Lows will be in the 60s tonight with winds out of the
south becoming light after sunset. Showers overnight will become
increasingly confined to our eastern and northeast areas while
there will remain potential for some showers to affect our
northwest and western counties early Thursday morning.

We are maintaining a risk for a few strong to severe storms on
Thursday as another disturbance will move across the area. Drier
air aloft is expected to slide into the area which could help
support more of a microburst risk with damaging winds in the
stronger convection. There looks to be more of a risk for small
hail in addition to damaging winds with the storms tomorrow. Highs
are forecast to be in the 80s areawide with more of a southwest
wind 5-10 mph.

05

.LONG TERM...
/Updated at 210 PM CDT Wed May 27 2020/

Thursday night through Tuesday.

The longer term forecast only needed some minor adjustments with PoP
timing as this pesky upper low finally decides to open up and build
further east.  This will leave lingering showers areawide on Friday
and perhaps further southeast on Saturday.  For the remainder of the
period, a dry high pressure will dominate the Southeast with little
in the way of rain chances and temperatures slowly building towards
the low 90s by Wednesday afternoon.

KL

We will continue to have elevated pops for Friday (best across the
east part of Central Alabama) as the trough continues to weaken
and exit to the northeast. At the same time, upper ridging will be
building across Western Conus. This will set up northwest upper
flow across the Central U.S. on Friday and into Alabama on
Saturday. As a result, a surface front should work across Conus
and into Central Alabama on Saturday. Isolated to scattered storms
are possible along and ahead of the front, but coverage should be
less than much of this week so far.

Drier air and clearing skies are expected behind the front thanks
to a 1024mb ridge that will build over the Upper Plains, Great
Lakes, and into the Mississippi River Valley by early Sunday. We
should see cooler overnight readings with lower dew points.
Readings should still warm sufficiently during the day into the
80s during the days for Sunday through the beginning of next week.
However, humidity values will be lower. The ridge will move east-
southeast across Eastern Conus for the first part of next week
toward the Atlantic Seaboard by Tuesday allowing for a rain-free
Sunday through Tuesday to end our forecast.

08

&&

.AVIATION...
00Z TAF Discussion.

An broad closed upper low over the AR-LA-Tex region was producing
bands of showers and tstms over the Central Gulf States. One band
over east MS was tracking northeast, but will likely weaken once
it enters west Alabama due to loss of daytime heating. Another
band over east Alabama should exit Alabama by 02z. Showers with
VCTS will impact KASN and KANB thru 01z, producing MVFR conds due
low cigs. Another cluster of MVFR cigs has developed on back side
of exiting rain shield, impacting KMGM and possibly KEET for a few
hours early in the period. Widespread MVFR cigs will develop by
06z, with IFR cigs likely by 09z. With clearing skies and light
winds overnight, fog will likely form, but confidence is low in
which areas will see fog and how low vsbys will fall. Overall,
expect widespread IFR conds either due to cigs or fog. Mid level
dry air will overspread the area on Thursday, and hinder convective
development. After low clouds and fog erode, VFR conds expected
after 16z. An impulse from the upper low will likely bring an
increase in tstm activity over far west Alabama after 21z.

58/rose

 &&

.FIRE WEATHER...

Moisture remains elevated through late week with higher chances of
wetting rains including thunderstorms through Friday. Some storms
may be strong today on Thursday. Minimum relative humidity values
are forecast to remain above 50 percent through Friday. On Saturday,
a surface front may bring a few showers and storms but then some
drier weather and lower humidity values for the second half of the
weekend and into the first part of next week.

&&

.PRELIMINARY POINT TEMPS/POPS...
Gadsden     64  82  61  83  60 /  80  20  30  50  10
Anniston    65  83  63  84  61 /  80  20  30  50  20
Birmingham  65  83  65  84  63 /  40  20  40  40  10
Tuscaloosa  65  85  64  84  63 /  40  30  30  30  10
Calera      65  83  64  84  63 /  40  20  30  40  10
Auburn      66  83  65  84  64 /  50  20  20  50  20
Montgomery  67  86  66  86  65 /  30  20  30  40  20
Troy        67  88  66  86  65 /  40  20  20  60  20

&&

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

&&