SPC Dec 18, 2025 0100 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 0100Z Day 1 Outlook


Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0621 PM CST Wed Dec 17 2025

Valid 180100Z - 181200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Isolated thunderstorms are possible along portions of the TX/LA Gulf
coasts tonight.

...01z Update...

Weak, southern-stream short-wave trough is advancing off the south
TX coast early this evening. A few thunderstorms linger near the
center of a weak midlevel circulation around the Corpus Christi
region; however, the most concentrated deep convection is now
focused offshore and should continue to be shunted east ahead of the
short wave.

Isolated thunderstorms may eventually develop ahead of this feature
downstream across southeast LA later tonight, but negligible
buoyancy currently exists on the 00z sounding from LIX. By the end
of the period, adequate destabilization should materialize across
this region such that lightning is possible with deep convection,
primarily after 08-09z.

..Darrow.. 12/18/2025


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SPC Dec 17, 2025 1630 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 1630Z Day 1 Outlook


Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1022 AM CST Wed Dec 17 2025

Valid 171630Z - 181200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
SOUTHERN IDAHO AND NORTHERN UTAH...

...SUMMARY...
While strong to locally severe winds may occur with low-topped
convection through early afternoon across parts of southern Idaho
and northern Utah, the overall threat for organized severe
thunderstorms appears low.

...Interior Northwest and Northern Great Basin/Rockies...
A powerful mid-level shortwave trough and associated sub-980 mb
surface low will move quickly eastward today across the interior
Northwest/northern Rockies and adjacent western Canada. A strong
surface cold front will likewise translate east-southeastward over
the northern Intermountain/Great Basin region late this morning into
the afternoon. Widespread cloud cover remains prevalent ahead of the
front across southern ID into northern UT and vicinity, with cool
surface temperatures and very limited low-level moisture also
present. MUCAPE is expected to remain only barely sufficient to
support convection. But, given the enhanced flow at low levels noted
on recent VWPs from KCBX/KSFX, it is not entirely out of the
question that convectively augmented gusts may exceed the already
strong background gradient winds on a localized basis. The Marginal
Risk has therefore been maintained for parts of southern ID/northern
UT and vicinity, even though the overall threat for organized severe
thunderstorms will remain low.

..Gleason/Weinman.. 12/17/2025


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SPC Dec 17, 2025 1300 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 1300Z Day 1 Outlook


Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0655 AM CST Wed Dec 17 2025

Valid 171300Z - 181200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE NORTHWEST AND NORTHERN INTERMOUNTAIN REGION...

...SUMMARY...
Sporadic severe wind gusts may accompany low-topped convection
across parts of the Northwest and northern Intermountain region this
morning into midday.

...Northwest/Northern Intermountain region...
A progressive/vigorous shortwave trough will continue to modestly
amplify and otherwise race east-southeastward from the
Washington/British Columbia border vicinity this morning to the
northern Plains tonight. Intense deep-tropospheric flow (highlighted
by 55-85 kt at 700 mb) will accompany this wave, yielding widespread
high winds across much of the Northwest to the northern Great
Plains.

Low-topped convection, occasionally capable of lightning and
semi-organized line segments, will continue in association with the
east/southeastward-advancing cold front, with convection potentially
expanding by late morning towards the Snake River Plain/Yellowstone
vicinity and potentially other parts of the northeast Great Basin by
afternoon. Surface-based instability will be very limited, but some
convectively enhanced wind gusts may occur.

..Guyer/Lyons.. 12/17/2025


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SPC Dec 17, 2025 0600 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 1200Z Day 1 Outlook


Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1145 PM CST Tue Dec 16 2025

Valid 171200Z - 181200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS IN PARTS OF THE
NORTHWEST...

...SUMMARY...
Sporadic severe gusts may accompany low-topped convection across
parts of the Northwest this morning into midday.

...Northwest...
A vigorous shortwave trough will move quickly east along the
Canadian border from WA to the northern Great Plains by evening.
Intense tropospheric flow will accompany this wave, yielding
widespread high winds across much of the Northwest to the northern
Great Plains. Deep lee surface cyclone over southern AB should reach
the Red River Valley of the North. Attendant Pacific cold front will
sweep east with a tight pressure gradient in its wake.

Low-topped convection may be ongoing at 12Z along the Columbia Basin
portion of the front. Most guidance also suggests an increase in
low-topped convection should occur towards late morning across parts
of the Snake River Plain as the front pushes east. Surface-based
instability will remain scant in both regimes with morning
temperatures in the 40s to low 50s. Despite the cool temperatures,
this may be sufficient for sporadic lightning flashes amid strong
large-scale ascent. With very strong surface winds accompanying the
front, both regimes could be coincident with severe wind gusts.

The bulk of sustained severe wind speeds should become primarily
confined along/east of the Rockies in MT to the CO Front Range this
afternoon per HREF/REFS guidance. However, potential for severe
convective gusts appears too conditional with negligible
surface-based buoyancy anticipated.

..Grams/Wendt.. 12/17/2025


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