RSS Mesoscale Discussions from Storm Prediction Center
No watches are valid as of Wed Dec 17 18:00:01 UTC 2025.
No Mesoscale Discussions are in effect as of Wed Dec 17 18:00:01 UTC 2025.
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 1730Z Day 2 Outlook
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1125 AM CST Wed Dec 17 2025
Valid 181200Z - 191200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
...SUMMARY...
Severe potential will be limited on Thursday, but isolated strong
wind gusts are possible across portions of the Lower Ohio and
Tennessee Valleys.
...Synopsis...
A strong upper trough will move across Midwest on Thursday with low
pressure moving across the Great Lakes. A cold front will extend
south from this low with wind shift moving across the OH and TN
Valleys during the day and into the evening. Minimal destabilization
is forecast ahead of the front as clouds and early day precipitation
hamper heating. Mostly elevated instability is forecast, though
shear profiles will be strong. Despite a marginal/cool boundary
layer across the warm sector, deeper ascent along the cold front
could support shallow moist convection capable of augmenting gusts
with the frontal passage.
Elsewhere, moisture and instability will increase overnight well off
the NC Coast, but supercells developing over the water may
eventually skirt the Outer Banks of NC toward the end of the period.
At this time it appears the instability gradient will remain
offshore.
..Jewell.. 12/17/2025
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SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
1058 AM CST Wed Dec 17 2025
Valid 171700Z - 181200Z
The previous forecast remains on track with only minor expansions
made across southeast CO/southwest KS to reflect latest high-res
guidance. 16 UTC surface observations show winds beginning to
increase along the northern CO Front Range, but the strongest winds
are expected later this afternoon (mainly between 20-00 UTC) as the
mid-level jet begins to impinge on the northern Rockies. It remains
unclear exactly how severe RH reductions will be in the lee of the
immediate front range where peak winds are expected. While some
guidance shows RH minimums near 20%, morning solutions don't appear
to be accurately capturing recent satellite trends with more
widespread cloud cover noted in GOES imagery than depicted in recent
HRRR/RRFS runs. This continues to limit confidence in the potential
for widespread critical fire weather conditions, though localized
critical conditions may emerge if sufficient clearing can occur.
Regardless, the strong winds coupled with slowly increasing ERC
values (near the 70th percentile) should still support a wind-driven
fire weather risk. See the previous discussion below for additional
details.
..Moore.. 12/17/2025
.PREV DISCUSSION... /ISSUED 1150 PM CST Tue Dec 16 2025/
...Synopsis...
A potent upper trough will move through the Northwest and reach the
Plains by Thursday morning. At the surface, a cyclone will deepen in
the northern Plains with a trough extending into the
central/southern Plains.
...Central/southern High Plains...
Strong mid-level winds will be nearly perpendicular to the Rockies.
This, coupled with a strong cross-Divide pressure gradient, will
foster strong sustained winds and stronger gusts in the immediate
lee of the terrain. Sustained 20-30 mph winds will be probable in
the terrain-favored areas. A period of wind gusts to 60-70 mph are
expected in the lower foothills. Farther east and south, 15-20 mph
will become more common. RH will be above elevated criteria in many
places, but 15-25% will be possible from Wyoming into Colorado.
Farther south, RH will more likely be around 15-20%. With fuels
having continued to dry, the strong surface winds will still lead to
elevated to locally critical fire weather.
...Piedmont...
Dry and modestly breezy conditions appear possible within the region
during the afternoon. RH could fall as low as 20-25%, but there is
variability within guidance. Winds will generally be light at around
10 mph. Locally elevated conditions are possible, but the
duration/spatial extent is too limited and uncertain for highlights.
...Please see www.spc.noaa.gov/fire for graphic product...
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