River Flood Warning 3, NWS Birmingham, AL

Area Forecast Discussion
National Weather Service Birmingham AL
552 AM CST Wed Feb 2 2022

.UPDATE...
For 12Z Aviation.

&&

.SHORT TERM...
/Updated at 0355 AM CST Wed Feb 02 2022/

Through Thursday.

Wet and mild conditions will be in place through the short term.
Overall not much of a change to the ongoing trends with flooding
being the main concern. We are already seeing light rain work into
the area and will see additional increase in the precipitation
through the day and into the afternoon as round one moves through
the area. This round will serve as more of a primer to the larger
scale rainfall on Thursday. As we move into the overnight period,
we will begin to see the cold front itself begin to slowly move into
the area Thursday morning. There will be a large amount of rain on
the front and backside of the front. By the time rainfall totals are
added up, we are looking at 2 to 4 inches in the northwest from
today through Friday morning and 1 to 3 inches for areas north of I-
85. South of I-85 1 to 1.5 inches can be expected. A flash flood
watch has been issued.

Several surface lows will develop along the front with main surface
low developing in norther Louisiana by Midnight and sliding along
the front. This low will try to pick up a marine front and swing it
northward as a warm front. Question is how far north will the front
make it. This would determine the severe threat Thursday afternoon.
some of the more robust models take the low along an north of a
Tuscaloosa to Calera line, thus increasing the threat for a few
strong to marginally severe storms through early Thursday evening
or until the warm front is absorbed by the cold front. We are going
to include the marginal threat for the south during the afternoon,
with very low confidence. As for the HWO will continue to use
flooding as the primary threat with the low end marginal severe
storms as secondary. Addition concerns will be discussed in the long
term section as the front moves out of the southeast.

16

.LONG TERM...
/Updated at 0355 AM CST Wed Feb 02 2022/

Friday.

A solid anafrontal system and widespread rainfall will be working
across Central Alabama Thursday night/Friday morning. Lingering
rainfall could be heavy at times along with associated
embedded/elevated thunderstorms. This overall activity will continue
an east/southeast progression into Friday morning. Lighter rainfall
will linger for some time after frontal passage as parcels rise over
the shallow frontal surface amidst southwesterly flow aloft.
Heaviest rainfall will taper off early Friday morning, though
lingering flooding could persist for a bit, especially if minor
river flooding becomes a consideration due to the widespread nature
of the rainfall across many basins. Thunderstorm activity, including
any stronger storms, should have already tapered off with loss of
surface-based instability.

Meanwhile, the shallow layer of cold air will begin working into the
area from the northwest. This will allow for a brief window of light
rain or freezing rain for our far northwest counties, Marion County
in particular. NAM/GFS/SREF BUFKIT soundings between CBN and RSL
suggest light freezing rain/drizzle and perhaps some patchy light
sleet, generally 3 AM thru 7 AM Friday morning, despite drier mid-
level air. ECMWF point forecast soundings also suggest this with sub
850 mb air remaining saturated enough to foster mentionable PoPs.
We'll watch trends here in the event a Winter Weather Advisory is
needed (any measurable accumulation of freezing rain or sleet in
this case). Forecast confidence is too low for any issuance at this
time, but will include a low-confidence mention in the HWO for now.

Saturday through Monday.

The remainder of the long-term forecast period will be best
characterized by relatively cool and dry conditions. However, we're
still trying to sort out the details of a light rain potential
associated with a lagging shortwave on Saturday. This feature is
progged to become cutoff/unphased from the northern stream trough as
it exits northeastward Friday night. I've kept some low PoPs in for
Saturday night/Sunday morning , but don't expect any meaningful QPF
after looking at drier solutions in tonight's guidance. Dry, cool
weather is forecast for the beginning of next week.

40/Sizemore

&&

.AVIATION...
12Z TAF Discussion.

Will continue low-level wind shear across the north through the
morning, despite the rain moving in. After 15 to 17z, surface
winds pick up further along with convection beginning to move in
with upper shortwaves. MVFR cigs develop first at TCL then at BHM,
spreading further as convection moves into the area for most.
Periods of showers will be on throughout the cycle. Did not
include any thunder but will need to be looked at for the next 2
sets of TAFS.

16

&&

.FIRE WEATHER...

Light to moderate rain shower activity will continue to increase
from the west today along with further moisture increases. 20 ft
winds will remain from the southeast at 5-10 mph. Rainfall becomes
more widespread with embedded thunderstorms on Thursday, and some
rain could be locally heavy at times. Cooler, drier conditions
are expected to work back into the area on Friday behind the cold
front.

&&

.PRELIMINARY POINT TEMPS/POPS...
Gadsden     61  54  70  39  45 /  90  90  90 100  30
Anniston    64  57  70  44  47 /  80  80  80 100  40
Birmingham  63  57  69  39  44 /  90  90  90 100  20
Tuscaloosa  64  59  70  38  45 /  90  90 100  90  20
Calera      65  60  70  42  46 /  90  90  90 100  30
Auburn      67  57  71  51  55 /  50  50  50 100  60
Montgomery  70  61  74  48  52 /  60  60  80  90  50
Troy        71  60  75  52  56 /  40  50  60  90  60

&&

.BMX WATCHES/WARNINGS/ADVISORIES/...
Flood Watch from Thursday morning through Friday morning for the
following counties: Autauga...Bibb...Calhoun...Chambers...
Cherokee...Chilton...Clay...Cleburne...Coosa...Dallas...Elmore...
Etowah...Greene...Hale...Jefferson...Lee...Lowndes...Macon...
Marengo...Montgomery...Perry...Randolph...Shelby...St. Clair...
Sumter...Talladega...Tallapoosa...Tuscaloosa.

Flood Watch from late tonight through late Thursday night for
the following counties: Blount...Fayette...Lamar...Marion...
Pickens...Walker...Winston.

&&

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