RSS Mesoscale Discussions from Storm Prediction Center
No watches are valid as of Sat Dec 21 12:55:01 UTC 2024.
No Mesoscale Discussions are in effect as of Sat Dec 21 12:55:01 UTC 2024.
SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0650 AM CST Sat Dec 21 2024
Valid 211300Z - 221200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
...SUMMARY...
Isolated thunderstorms are possible this morning into early
afternoon across parts of coastal Oregon and northern California.
...Coastal OR/northern CA...
A potent mid to upper-level shortwave trough will move ashore the
northern CA/OR coast and continue northeastward into the southern
Canadian Rockies/northern Rockies vicinity through late tonight.
Weak thunderstorm activity embedded within a warm-air advection rain
shield will continue moving into the coastal range mountains this
morning before outrunning the inland penetration of scant
instability. The corridor of thunderstorms will probably shift
north along the coast into OR by midday into the early afternoon in
association with the mid-level cold pocket encroaching on the OR
coast. Elsewhere, quiescent weather or stable conditions will
preclude thunderstorm development over the remainder of the
contiguous United States.
..Smith/Goss.. 12/21/2024
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SPC 0830Z Day 3 Outlook
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0222 AM CST Sat Dec 21 2024
Valid 231200Z - 241200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
...SUMMARY...
Severe thunderstorms are not expected on Monday.
...Discussion...
A shortwave trough is expected to amplify over the Rockies and High
Plains in advance of a more prominent upper trough approaching the
California coast Monday night. Modest low-level moisture return will
occur across Texas in advance of a southeastward-moving cold front
crossing the southern High Plains and parts of Texas. The potential
for elevated thunderstorms should increase Monday night particularly
across North Texas and south-central/eastern Oklahoma to the
ArkLaTex. This will be as forcing for ascent and elevated moisture
transport increase regionally. Severe thunderstorms are not
currently expected given access to only weak elevated buoyancy.
..Guyer.. 12/21/2024
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Day 4-8 Outlook
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0322 AM CST Sat Dec 21 2024
Valid 241200Z - 291200Z
...DISCUSSION...
A more active southern-stream pattern is expected next week with
several lower latitude troughs crossing the southern tier, along
with some northward increase in low-level moisture across parts of
Texas to the Lower Mississippi Valley and Gulf Coast. On Tuesday/Day
4, one such shortwave trough should influence increasing
thunderstorm potential across south-central to east/southeast Texas.
Some severe risk could materialize Tuesday, but it appears that
overall buoyancy will be weak with the severe potential currently
expected to be relatively marginal and isolated in nature.
An additional focus for increasing deep convective potential will be
into the Thursday/Day 6, Friday/Day 7, and Saturday/Day 8 time
frame. This will be as a secondary upper trough emerges from the
Southwest deserts and moves toward the Deep South. This could lead
to a severe risk in a corridor from east/southeast Texas and the
ArkLaTex to Lower Mississippi Valley. While some severe storms will
be possible, perhaps especially Thursday/Day 6, there is lingering
risk magnitude uncertainty related to moisture/destabilization given
the potential influences of the preceding shortwave trough and cold
front. Forecast uncertainties at this time frame precludes any 15%
outlook areas.
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