ACUS02 KWNS 200525
SWODY2
SPC AC 200523

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1223 AM CDT Fri Sep 20 2024

Valid 211200Z - 221200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
EASTERN NEW MEXICO AND WESTERN TEXAS...

...SUMMARY...
Isolated severe thunderstorms are possible on Saturday afternoon to
early evening in New Mexico and the southern High Plains, the mid
Missouri Valley to upper Mississippi Valley, and central
Appalachians region.

...Southern High Plains vicinity...

A southern stream upper low and attendant trough will progress east
across the Four Corners and southern Rockies on Saturday. An area of
enhanced southwesterly flow aloft associated with the ejecting
trough will become oriented over eastern NM into the OK/TX
Panhandles by 00z/Sun. While strong heating will result in some
boundary layer mixing, south/southeasterly low-level flow will
result in persistent theta-e advection, and dewpoints from the upper
50s to low 60s F are expected. Steepening midlevel lapse rates will
contribute to modest destabilization, with 1000-1500 J/kg MLCAPE
forecast across parts of eastern NM into the TX Panhandle/South
Plains vicinity. Vertically veering wind profiles amid strengthening
midlevel flow will support isolated supercell thunderstorms. Large
hail and sporadic strong/severe gusts are possible. Given increasing
consistency in forecast guidance, a Slight risk (level 2 of 5) has
been included for parts of the eastern NM Plains into west Texas.

Additional strong storms are possible to the north and west across
northeast NM into south-central CO beneath the core of mid/upper
low. Instability will be weaker across this area, but isolated
strong gusts and marginal hail will still be possible with the
strongest storms.

...Western PA into northern/central VA...

A low-amplitude mid/upper shortwave trough is forecast to move
across the Northeast on Saturday. Northwesterly deep-layer flow will
overspread the Upper OH Valley toward the Mid-Atlantic coast. A
corridor of low to mid 60s F dewpoints and pockets of stronger
heating will support weak destabilization. Modest vertical shear
(around 20-25 kt effective shear) will aid in at least transient
organized updrafts. Elongated/straight hodographs and cool
temperatures aloft suggest marginally severe hail will be possible
with the stronger cells. Locally strong gusts also will be possible
where stronger heating and steepening of low-level lapse rates
occurs.

...Central Plains to Mid-MO/Upper MS Valley...

The forecast for this region remains quite uncertain for Saturday.
Most guidance depicts some degree of convection ongoing across parts
of IA/MO Saturday morning. The evolution of this activity will
impact how the airmass destabilizes/recovers late in the afternoon
across the region. Nevertheless, large-scale ascent will increase
over the Upper Midwest as a northern stream upper trough traverses
the Canadian Prairies and the international border vicinity.
Southerly low-level flow will maintain 60s dewpoints ahead of a cold
front tracking southeast across MN and the Mid-MO/Upper MS Valley
from late afternoon into the evening. Isolated strong to severe
thunderstorms producing hail and gusty winds will be possible, but
the overall risk remains uncertain.

..Leitman.. 09/20/2024

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