ACUS01 KWNS 131244
SWODY1
SPC AC 131243

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0643 AM CST Fri Dec 13 2024

Valid 131300Z - 141200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not expected through tonight.

...Synopsis/Discussion...
As heights rise in the East following the departure of a substantial
synoptic-scale trough, two strong shortwave troughs will progress
through the midlatitude westerlies upstream, and influence thunder
potential across the western/central CONUS:

1.  A leading perturbation -- now apparent over the eastern Great
Basin and southern ID -- should extend from southeastern WY across
east-central CO to eastern NM by 00Z.  By the end of the period, the
trough should reach central portions of SD/NE/KS and northwestern
OK, while deepening.  A closed 500-mb low may develop on the trough,
either then or within a few hours into day 2, over south-central/
southeastern NE.  Strong, foregoing low-level warm advection and
moisture transport will persist through the period, atop a
relatively stable near-surface layer.  Increasing thunderstorm
coverage is expected after about 06Z from the middle/upper TX Coast
to the lower Missouri Valley, as increasingly moist parcels above
that stable layer reach LFC.  This will occur in concordance with
steepening low/middle-level lapse rates and decreasing MUCINH,
mainly related to the warm advection (but also late DCVA over
northwestern parts of the outlook area).  Small hail may fall from
the strongest cells; however, forecast soundings indicate effective
shear, buoyancy and inflow-layer moisture content should be too
small for a severe threat.

2.  The trailing shortwave trough -- initially evident in moisture-
channel imagery over the North Pacific around 40N150W -- will move
rapidly eastward and amplify, with preceding large-scale ascent
reaching the CA/OR coastline after 06Z on either side of a low-level
cold front.  While lapse rates in the frontal band should be modest,
and buoyancy meager, areas of MUCAPE around 50-200 J/kg, rooted near
700 mb -- may extend deeply enough into suitable icing layers to
support isolated lightning.

..Edwards/Goss.. 12/13/2024

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