Special Marine Warning 143, NWS Mobile, AL

Area Forecast Discussion
National Weather Service Mobile AL
1246 PM CDT Sat Jun 12 2021

.NEAR TERM /Now Through Sunday/...An upper level trough continues
to reside over the southeastern U.S. today into Sunday. This helps promote
northwesterly flow aloft today, becoming northerly by Sunday as
upper level ridging to the west shifts slightly east. A surface
trough over the southeastern U.S. may gradually attempt to close
off into an area of low pressure by Sunday over GA or just
offshore the GA coastline, and a weak/diffuse surface boundary
dropping south across the CWA today helps to shift surface winds
from westerly to northwesterly by the evening hours.

The aforementioned boundary should serve as a focus for
convective development this afternoon and evening. Ahead of this,
we already have isolated shower and thunderstorm activity popping
up across the region. Expect these to continue to exhibit a more
pop up nature with storms generally lasting an hour or so before
collapsing and repeating the cycle. Our environment is ripe for
strong updrafts and downdrafts in storms this afternoon and
evening. Latest mesoanalysis shows generally 3,500 to 4,500j/kg of
SBCAPE has developed over the region amidst surface temperatures
in the upper 80's and lower 90's, and surface dewpoints in the
middle 70's along with steep low level lapse rates over 8C/km.
Generally anticipate SBCAPE to build to around 4,000 to 5,000j/kg
by peak heating this afternoon into early evening. Likewise, our
MLCAPE is high generally between 2,500 to 3,500j/kg, with the
higher values becoming more widespread through peak heating. Shear
is rather marginal, with around 15 to 20kts effective shear
present, however may eventually support some local organization of
convection into loose linear segments by this evening
(particularly when shear is "maximized" closer to sunset as the
LLJ picks up in intensity). PWAT's remain in the 1.7 to 2.0 inch
range, and as such strong precip loading should be expected with
any storms today. DCAPE values generally range in the 1,000 to
1,200j/kg range this afternoon and evening, supporting the notion
for wet microbursts with any storms. Main hazards today continue
to be locally damaging wind gusts, heavy rainfall, and frequent
lightning. A marginal risk for severe thunderstorms remains in
place for all of the CWA by the SPC.

By tonight, convection should gradually fade in intensity and
coverage to isolated to perhaps scattered showers and
thunderstorms at times. By daybreak Sunday, at best isolated
showers and storms should remain. Temperatures overnight tonight
will bottom out in the lower to middle 70's. Sunday will feature
generally a similar evolution to Saturday, with convection
increasing in coverage during the afternoon and evening hours and
another shot at some wet microbursts. There may be some slightly
increased shear to around 20 to 25kts Sunday, which may help with
storm organization a bit. Generally the same thermodynamic
environment remains, but could be modified some if enough
convective overturning can occur Saturday. Same hazards are
expected with storms Sunday, including locally damaging wind
gusts, heavy rainfall, and frequent lightning. High temperatures
Sunday should top out in the upper 80's to lower 90's. A MODERATE
risk of rip currents remains in place today, becoming LOW risk on
Sunday. MM/25

&&

.AVIATION...
18Z issuance...Generally VFR conditions prevail today through
Sunday, with MVFR ceilings and visibility possible in any showers
and thunderstorms. This is particularly the case this afternoon
into mid-evening, and like-wise Sunday afternoon into mid-evening.
Surface winds have been a bit gusty at times, with generally
northwesterly winds around 10kts gusting to 15 to 20kts at times,
particularly over far southwestern AL and the FL panhandle. Expect
this to continue through this evening, before ramping up again
tomorrow mid-morning to similar values. MM/25

&&

.MOB WATCHES/WARNINGS/ADVISORIES...
AL...None.
FL...None.
MS...None.
GM...None.
&&

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