Small Craft Advisory 10, NWS Mobile, AL

Area Forecast Discussion
National Weather Service Mobile AL
1142 AM CST Mon Jan 20 2025

...New AVIATION...

.AVIATION...
(18Z TAFS)
Issued at 1142 AM CST Mon Jan 20 2025

While VFR conditions are expected to prevail through the period,
scattered to potentially numerous patches of snow are anticipated
to spread into the area from the west Tuesday morning, with
reductions in visibility to MVFR possible. Northerly winds around
10 knots this afternoon diminish this evening, then pick up to
10-15 knots Tuesday morning. /29

&&

NEAR TERM...
(Now through Tuesday night)
Issued at 417 AM CST Mon Jan 20 2025

...A rare winter storm is becoming increasingly likely across the
area Tuesday through Tuesday night...

Forecast uncertainty still exists, and if I'm being honest, my
confidence has dropped a bit from this time yesterday for the
northern part of our area. Global ensembles have sharpened the
gradient of precip, shifting the axis of heavier snow south. In
fact, some of the guidance keeps the bullseye of max snowfall over
the Gulf, with lessening amounts further north. This axis will
depend heavily on a number of things that global models are likely
not handling very well. Based on potential impacts, and the rarity
of this type of an event, have erred on the side of caution and a
Winter Storm Warning is now in effect for the entire area
beginning at 6 AM Tuesday morning.

Now for the forecast details.... What a difference a day makes!
This time yesterday, portions of the area were in the 60s and
now, we've dropped into the upper 20s with cooling expected to
continue through the remainder of the overnight hours. Broad
troughing will encompass much of the CONUS, with high pressure
building southward through the central CONUS through the day.
Highs today will be as much as 30 degrees below normal for
January, with bitter cold expected to settle into the region for
the next couple of days. Wind chills are still expected to dip
into the single digits the next few nights, with wind chills only
rising into the 20s during the day. Temps won't be much warmer,
with max temps only warming into the 30 to lower 40s this
afternoon.

A shortwave is expected to round the base of the trough beginning
tonight and move through the Southern Plains and Lower Mississippi
Valley on Tuesday. Surface cyclogenesis is expected to occur off of
the southeast Texas coast, as the shortwave strengthens early
Tuesday morning. Despite strong CAA bringing much drier air into the
area, mid and upper level moisture will increase rapidly Tuesday
morning as southwest flow aloft strengthens. Now that we are within
the 48 hour window, the available hires guidance points to a rather
sharp gradient in snowfall amounts, with the heaviest axis generally
along and south of I-10, like mentioned above. This makes sense, as
the strongest forcing will be in this area, where the surface low
will be closer and a convergence boundary sets up. Being 24+ hours
out, there's plenty of room for this axis to shift, which will play
a key role in determining specific totals. The precip type for much
of the area is a bit more clear, with the consensus among guidance
pointing to all snow for much of the area. Though some mixed
precipitation is possible, hires and global ensembles have come in
colder aloft, with the full vertical column likely remaining below
freezing through much of the event. While surface temps may increase
briefly during the day, fully saturated profiles aloft, as well as
quite a bit of forcing in the saturated layer (all in the dendritic
growth zone between -12 and -17 degrees) points to the likelihood
of us cooling a bit faster than what models are indicating due to
wet bulbing as snow begins to fall aloft. Another point of
contention that may be impacting snow totals is how guidance is
handling the dry lower levels. Which, again, if we wet bulb
quicker that will be overcome quite easily.

Based on the latest guidance, the most likely snow accumulations
remain between 1 and 3 inches for much of the area. Some of our
northernmost locations may be hard pressed to see 0.5 inch of snow,
but these scenarios have a tendency of overperforming. Highest
confidence exists for the southern half of the area, which is kind
of unbelievable. There is still a low (10%) chance for 3 to 5
inches. Regardless, subfreezing temperatures leading up to the
event, as well as the potential for heavy snow at times, make it a
bit easier for snow to begin accumulating on roads, and especially
bridges/overpasses. Therefore, the Winter Storm Watch was upgraded
to a Warning with this issuance (as stated above). /73

SHORT AND LONG TERM...
(Wednesday through Sunday)
Issued at 417 AM CST Mon Jan 20 2025

Snow will come to an end by early Wednesday morning, with the
remainder of the forecast period staying dry. How cold we get will
depend on how much snow is realized, with a higher amount meaning
colder temps than what we are currently forecasting. Either way,
dangerously cold temperatures are anticipated Tuesday night and
Wednesday, as overnight lows fall into the teens and daytime highs
remain in the upper 30s to lower 40s. Wind chills will Tuesday night
will drop into the single digits. /73

Upper troughing persists across the eastern CONUS through Friday
in the wake of our winter weather event, with upper ridging
gradually starting to build in Saturday into Sunday. Some
residual impacts to area roads and bridges may be possible each
morning through Friday associated with black ice as any melting
of snow could refreeze on surfaces as overnight lows remain
bitterly cold in the upper teens and lower 20's. Highs will only
be topping out in the lower to middle 40's Thursday and Friday,
which could be on the generous side depending on the magnitude of
snow cover across the area. We warm up into the lower to middle
50's for highs Saturday and potentially even middle 60's by
Sunday. Morning lows only finally make it above freezing by the
time we get to Saturday night into Sunday morning with lows in the
lower to middle 30's over the interior and upper 30's and lower
40's nearer the coast. Cold Weather Advisories may continue to be
needed Thursday night as overnight wind chills fall into the
middle teens areawide. MM/25

&&

.PRELIMINARY POINT TEMPS/POPS...
Mobile      25  31  15  40  20  45  24  50 /   0  90  30   0   0   0   0   0
Pensacola   28  33  20  38  25  44  29  49 /   0  90  70   0   0   0   0   0
Destin      31  36  23  41  28  47  32  51 /  10  90  90   0   0   0   0   0
Evergreen   21  32  14  42  17  46  21  51 /   0  80  40   0   0   0   0   0
Waynesboro  21  31  11  41  17  47  21  50 /  10  80   0   0   0   0   0   0
Camden      20  31  13  40  17  44  21  48 /   0  70  10   0   0   0   0   0
Crestview   23  33  17  40  16  45  22  50 /   0  90  80   0   0   0   0   0

&&

.MOB WATCHES/WARNINGS/ADVISORIES...
AL...Extreme Cold Watch from 9 PM CST this evening through Wednesday
     morning for ALZ051>060-261>266.

     Winter Storm Warning from 6 AM Tuesday to 6 AM CST Wednesday for
     ALZ051>060-261>266.

FL...Extreme Cold Watch from 9 PM CST this evening through Wednesday
     morning for FLZ201>206.

     Winter Storm Warning from 6 AM Tuesday to 6 AM CST Wednesday for
     FLZ201>206.

MS...Extreme Cold Watch from 9 PM CST this evening through Wednesday
     morning for MSZ067-075-076-078-079.

     Winter Storm Warning from 6 AM Tuesday to 6 AM CST Wednesday for
     MSZ067-075-076-078-079.

GM...Small Craft Advisory from 3 AM Tuesday to 9 AM CST Wednesday for
     GMZ630>636-650-655.

     Small Craft Advisory until noon CST today for GMZ631-632-650-655-
     670-675.

     Small Craft Advisory from 3 AM to 9 AM CST Tuesday for GMZ670-
     675.

     Gale Warning from 9 AM Tuesday to 9 AM CST Wednesday for GMZ670-
     675.

&&

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