546
ACUS03 KWNS 090730
SWODY3
SPC AC 090729

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0229 AM CDT Fri May 09 2025

Valid 111200Z - 121200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SUNDAY INTO
SUNDAY NIGHT ACROSS PARTS OF CNTRL AND NRN FL...SWRN GA...SRN/WRN
AL...SRN AND CNTRL MS...SERN LA...ERN MT...NWRN SD...WRN ND...

...SUMMARY...
Widely scattered strong thunderstorms may impact the eastern Gulf
coast region on Sunday, posing at least some risk for severe hail
and locally strong surface gusts.  Additional thunderstorms may be
accompanied by strong to severe surface gusts across parts of
eastern Montana into the western Dakotas late Sunday afternoon and
evening.

...Discussion...
Little change to the general large-scale pattern is expected from
Saturday into Sunday, with much of North America remaining under the
influence of amplified, split westerlies - stronger across the
northern mid-latitudes than across the southern mid- and subtropical
latitudes.  Within this regime, significant mid-level troughing,
with at least a couple of smaller-scale embedded perturbations, is
forecast to begin digging inland of the northern U.S. Pacific coast.
 It appears that the leading edge of broad downstream ridging across
the interior of North America will overspread the St. Lawrence
Valley and Northeast.  In lower latitudes, the center of a broad
mid-level low may begin a very slow acceleration back to the
northeast, across the lower Mississippi Valley vicinity.

In lower levels, an initial weak low may weaken further across the
Canadian Prairies into northern Ontario, as surface troughing
deepens upstream, to the lee of the Canadian and northern U.S.
Rockies.  The center of cool surface ridging, initially across the
lower Great Lakes vicinity, is likely to redevelop southeastward off
the northern Mid Atlantic coast.  Near the southwestern periphery of
this surface ridging, a broad area of lower surface pressure may
shift inland off the Gulf into the lower Mississippi Valley,
accompanied by boundary-layer moistening inland of eastern Gulf
coastal areas.

...Lower Mississippi Valley/eastern Gulf Coast...
Beneath the mid-level cold core of the low, and the downstream
modest, difluent southwesterly mid/upper flow, models suggest that
thermodynamic profiles by Sunday afternoon may become conducive to
widely scattered strong thunderstorms with potential to produce some
severe hail and locally strong surface gusts.  This is expected to
generally become focused within the weak surface troughing across
parts of the western Florida Panhandle and southern Alabama into
southeastern Louisiana and southern/central Mississippi, and perhaps
along a convective outflow boundary advancing into Florida coastal
areas north of Tampa.

...Northern Rockies/Great Plains...
Downstream of the of large-scale mid/upper troughing digging into
the Northwest, it appears that forcing for ascent could support
scattered high-based thunderstorm activity, particularly within an
evolving deeply mixed boundary layer characterize by large surface
temperature/dew point spreads, but with weak CAPE, to the lee of the
northern Rockies.  The NAM, perhaps more so than other guidance,
suggests that consolidating outflow, associated with a clustering of
storms across parts of southeastern Montana into the western
Dakotas, aided by evaporative cooling/some melting and downward
transport of momentum, may become sufficient for a few strong to
severe surface gusts by Sunday evening.

..Kerr.. 05/09/2025

$$