Small Craft Advisory 16, NWS Mobile, AL

Area Forecast Discussion
National Weather Service Mobile AL
1142 AM CST Thu Mar 2 2023

...New AVIATION...

.AVIATION...
(18Z TAFS)
Issued at 1122 AM CST Thu Mar 2 2023

General MVFR or higher conditions were noted across most of the
forecast area at 17z, except for rain showers streaming onshore
over our coastal counties bringing low end MVFR to IFR conditions
to these areas. The heaviest showers were noted east of Mobile
Bay. Am expecting these showers to affect operations through the
afternoon, then ease into the evening hours. General MVFR
conditions will return to the area tonight, but with increasing
southerly flow ahead of an approaching system, LLWS may be a
problem after 06z into Friday. Southerly flow 10-15kts this
afternoon will rise to around 15-25kts and gusty tonight and last
into Friday. Showers and thunderstorms are expected to spread east
over the forecast area beginning around sunrise Friday and move
east of the area by 18z.
/16

&&

.NEAR TERM...
(Now through Friday)
Issued at 1122 AM CST Thu Mar 2 2023

Some light returns are being shown by radar at present. Isolated
showers will remain possible through the day today. Currently,
temperatures across the local area are fairly warm, ranging from
the upper 60s to lower 70s. A few surface observation stations
have reported patchy fog in the last hour or so as well. Any fog
is expected to lift with the sunrise this morning.

The main topic of focus for the near term, and for the entire
forecast period through the extended really, is the potential
severe threat very late tonight through the first part of the
afternoon on Friday. This is discussed in detail below.

Zonal flow aloft this morning will eventually give way to
southwesterly flow as an upper shortwave trough pivots from Texas
later this evening to be centered over Illinois and western
Kentucky by Friday afternoon, taking on a negative tilt as it
does. Taking a look at upper jet dynamics, much of the better
forcing remains to our north and northwest. Although, the fairly
stout upper jet (around 120 kts) will graze the northern portion
of our area from early Friday morning through the early part of
the afternoon. Coincident with this is a 50-60 knot low level jet
as well. Meanwhile, a surface low pressure system looks to
progress in a similar pattern as the upper shortwave trough, up
from Texas towards the Ohio Valley from this evening through
Friday afternoon. Model PWAT values range from around 1.3-1.5
inches, with potentially pockets of higher values periodically
from today through Friday (ahead of the aforementioned surface
front).

Sensible weather will consist of a few isolated showers this
evening, but a bit of a lull is anticipated overnight until a line
of showers and potential storms approaches by late tonight into
early Friday morning. This line is expected to push east of our
local area by mid to late afternoon. As for storm potential, the
severe risk continues to trend downward. While shear and SRH
remain abundant, guidance is not so optimistic about instability
Friday morning. Values between 500-1000 J/kg of CAPE are suggested
for most areas, with higher values to around 1000 J/kg over
coastal counties towards late morning/early afternoon. Overall,
instability will likely be one of the limiting factors, along with
the position of the upper forcing (to our north and northwest);
although, as mentioned above, some of that forcing via the upper
jet does clip our northern zones. The other factor will be whether
a capping inversion, still present in model soundings between
700-850 mb late tonight, will be able to erode through the morning
on Friday to allow storms to take shape. At this time, the area
with the higher probability of storms is expected to be north of
Highway 84 from early Friday morning through the early afternoon.
While strong storm development is possible for areas south,
confidence in occurrence is lower. This follows the Storm
Prediction Center, who has outlooked areas generally north of
Highway 84 on Friday in a Slight Risk of severe storms, with a
Marginal Risk for areas south. Ultimately, damaging winds will
remain the primary threat with any strong to severe storms that
may form, but a tornado or two cannot be ruled out.

As the day shift yesterday mentioned, outside of storms, the
tightening pressure gradient between the deepening surface low to
our northwest and strong high pressure over the western Atlantic
will allow for winds to increase late tonight into Friday morning.
Southerly sustained southwest winds between 20 to 30 mph and
gusts to around 40 mph are possible ahead of the cold front. A
Wind Advisory has been issued and is in effect from 3 AM until 3
PM CST Friday area-wide to account for this. Winds are expected to
quickly decrease from late Friday afternoon into the early
evening as the gradient weakens.

Additionally, a HIGH RISK of rip currents remains in effect
starting this evening and will persist through at least Sunday
afternoon. Large, breaking waves between 6 to 9 feet, with locally
higher waves to around 10 feet are also forecast due to increased
south to southwest winds and swell. A High Surf Warning was
therefore issued for our Alabama and Florida coasts from 3 AM
tonight through 12 AM CST Friday. /26

&&

.MOB WATCHES/WARNINGS/ADVISORIES...
AL...Wind Advisory from 3 AM to 3 PM CST Friday for ALZ051>060-
     261>266.

     High Rip Current Risk from 6 PM CST this evening through Sunday
     afternoon for ALZ265-266.

     High Surf Warning from 3 AM Friday to midnight CST Friday night
     for ALZ265-266.

FL...Wind Advisory from 3 AM to 3 PM CST Friday for FLZ201>206.

     High Rip Current Risk from 6 PM CST this evening through Sunday
     afternoon for FLZ202-204-206.

     High Surf Warning from 3 AM Friday to midnight CST Friday night
     for FLZ202-204-206.

MS...Wind Advisory from 3 AM to 3 PM CST Friday for MSZ067-075-076-
     078-079.

GM...Small Craft Advisory from 9 PM this evening to midnight CST
     tonight for GMZ630>632-650-655-670-675.

     Gale Watch from late tonight through Friday morning for
     GMZ630>632-650-655-670-675.

     Small Craft Advisory from midnight tonight to noon CST Friday
     for GMZ633>636.

&&

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