Mesoscale Discussion 521

Issued

Apr 17, 2022, 10:09 PM CDT (03:09 UTC)

Expired

Apr 17, 2022, 11:45 PM CDT

In force

96 min

Issued by

the Storm Prediction Center

Concerning

Severe thunderstorm watch 138

The Mobile radar (KMOB), 75 km from the middle of the area, began a volume at 03:11 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

406 
ACUS11 KWNS 180310
SWOMCD
SPC MCD 180309 
FLZ000-ALZ000-MSZ000-180445-

Mesoscale Discussion 0521
NWS Storm Prediction Center Norman OK
1009 PM CDT Sun Apr 17 2022

Areas affected...far southern MS into southern AL and the FL
Panhandle

Concerning...Severe Thunderstorm Watch 138...

Valid 180309Z - 180445Z

The severe weather threat for Severe Thunderstorm Watch 138
continues.

SUMMARY...Sporadic strong/locally damaging gusts and perhaps a
tornado will be possible the next 1-2 hours. However, a gradual
weakening trend is expected with eastward extent across southern AL
into the FL Panhandle.

DISCUSSION...A QLCS across southwest AL into far southern MS will
continue to shift east/southeast around 40-50 kt over the next few
hours, mainly posing a threat for sporadic strong gusts. The line of
convection is expected to approach the eastern edge of the watch by
the 05z expiration time. Additionally, lead supercell just northeast
of Mobile also may continue to pose a threat for hail and gusty
winds in the near-term, though radar trends have indicated recent
weakening. 

The downstream environment remains weakly unstable, though low-level
inhibition is expected to continue to increase. Overall radar
presentation of the QLCS has degraded over the past 15-30 minutes
with the previously strong and tornadic bookend vortex diminishing.
This suggests that the system is being impacted by the weaker
downstream instability and increasing boundary-layer inhibition. VWP
data from EVX and EOX indicate weakening vertical shear with
eastward extent as well, further hindering maintenance of a stronger
QLCS with time. While a few strong gusts and perhaps a tornado may
be possible in the near-term, the overall threat is expected to
gradually diminish with eastward extent. As such, a new watch is not
expected downstream from WW 138 at this time.

..Leitman.. 04/18/2022

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...TAE...MOB...LIX...

LAT...LON   31648815 31528632 31418549 30878507 30218502 29808520
            29708655 29798818 30078935 30318938 30718928 31008900
            31258858 31558824 31648815

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The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.