No watches are valid as of Fri Jul 17 22:31:02 UTC 2026.
No Mesoscale Discussions are in effect as of Fri Jul 17 22:31:02 UTC 2026.
SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0251 PM CDT Fri Jul 17 2026
Valid 172000Z - 181200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM CENTRAL
IDAHO INTO MONTANA...THE GREAT LAKES...AND THE OHIO VALLEY INTO THE
SOUTHEAST...
...SUMMARY...
Strong to potentially severe storms are possible today across parts
of western Montana and northern Idaho, and also across parts of the
Upper Midwest and northern Great Lakes. More isolated strong to
severe storms with damaging wind gusts are possible over parts of
the Ohio Valley and Southeast.
...20z Update...
The previous forecast remains largely on track based on latest
trends in ensemble guidance. Recent runs of the RRFS/HRRR
time-lagged ensemble continue to show some potential for organized
convection across northern WI and into the U.P. of Michigan later
this evening, and latest trends in GOES imagery show building
cumulus that seem to support these solutions. However, the overall
ensemble signal for widespread severe convection on the U.S. side of
the international border remains limited. Similarly, a corridor of
more focused wind potential may emerge across west-central MT this
evening, but given low ensemble probabilities for severe winds,
coupled with modest low-level lapse rates in latest RAP mesoanalyses
and forecast soundings, limits confidence in a widespread severe
wind threat. See the previous discussion below and MCD #1641 for
additional details.
..Moore.. 07/17/2026
.PREV DISCUSSION... /ISSUED 1130 AM CDT Fri Jul 17 2026/
...Northern Rockies and northern High Plains...
The region will be influenced by an increasingly progressive
shortwave trough moving northeastward from off the Washington coast
and over southern British Columbia. The preceding upper ridge will
flatten/shift eastward particularly near the international border,
with a plume of rich monsoonal moisture extending into the region,
highlighted by prevalent middle 50s to lower 60s F dewpoints along
the Continental Divide. Orographic lift and heating will promote the
development of scattered thunderstorms this afternoon, especially
across eastern/northern Idaho and western Montana. Steepened
low-level lapse rates will potentially yield storms capable of
isolated severe wind gusts beginning this afternoon and continuing
into mid-late evening. Isolated large hail may occur with the
stronger thunderstorm cores, especially over northwest Montana where
deep-layer shear may exceed 30 kt.
...Upper Midwest and northern Great Lakes...
A decaying cluster of storms continues to spread southeastward
across northern Michigan, and smoke will continue to be a factor
regionally, albeit with some west-to-east abatement later today. A
cold front associated with the upper wave will push southeastward
across the Upper Midwest and provide a focus for thunderstorm
redevelopment late this afternoon, and more so into this evening.
Forecast model guidance shows moderate buoyancy developing today
within a belt of 25-40 kt west-northwesterly 500-mb flow as upstream
shortwave trough amplification occurs.
A few of the stronger thunderstorms could evolve into supercells and
organized multicell clusters, although uncertainty persists
regarding the overall magnitude/extent of today's severe potential.
Isolated large hail and damaging gusts are the primary hazards,
although a brief tornado risk may also develop in the areas
surrounding Lake Superior. One or more clusters of strong to severe
storms may persist into the overnight along the warm front.
...Ohio Valley to the southern Appalachians and Florida...
A moist and diurnally destabilizing airmass will support scattered
to numerous storms developing by the mid afternoon. Some of the
stronger water-loaded downdrafts will potentially be capable of
50-60 mph gusts and isolated wind damage.
...West-central Texas...
A weak mid- to upper-level low over west Texas will move little
during the day while a warm/moist conveyor persists across southern
into central parts of Texas. Despite very moist low levels and some
enlargement of the low-level hodograph, weak flow in the mid levels
should limit storm organization and meaningful supercell potential,
more so favoring a heavy rain threat.
Read more
SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0229 PM CDT Fri Jul 17 2026
Valid 191200Z - 201200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE CAROLINAS INTO SOUTHEAST VIRGINIA...
...SUMMARY...
Isolated to widely scattered strong to severe thunderstorms may pose
a risk for damaging wind gusts across portions of the southern
Appalachians to the coastal Carolinas/southeast Virginia vicinity on
Sunday. Strong to severe storms may also develop across parts of
eastern Montana into North Dakota and Minnesota.
...Southern Appalachians into the Coastal Carolinas/southern VA...
A broad mid/upper-level trough will remain in place across much of
the eastern CONUS on Sunday. A weakening cold front may become
nearly stationary by afternoon somewhere across southern VA.
Scattered storm development is expected during the afternoon
along/ahead of the remnant frontal zone, and also near the higher
terrain of the southern Appalachians.
Deep-layer flow/shear will generally be weak to modest, but large
PW, steepening low-level lapse rates, and moderate to locally strong
buoyancy will support vigorous updrafts and localized downbursts. In
addition, low/midlevel flow may be sufficient for one or two
outflow-driven clusters to evolve with time and move southeastward
into the early evening, with wind-damage potential.
...Parts of eastern MT into ND/MN...
A vigorous shortwave trough may evolve into a mid/upper-level low as
it moves eastward across the Canadian Prairies on Sunday. An
attendant surface low is forecast to gradually intensify as it moves
toward Lake Winnipeg. A surface trough/weak cold front will move
into northeast MT during the day and across parts of the Dakotas
during the evening.
A conditionally favorable environment is expected to evolve across
parts of far eastern MT into ND and northwest MN during the
afternoon/evening, as a 40-50 kt midlevel jet and steep lapse rates
overspread a warm and relatively moist boundary layer. However, with
the strongest height falls and ascent expected to remain north of
the international border, capping may inhibit diurnal storm
development. Any storms that are able to develop and mature during
the afternoon and early evening could evolve into organized cells or
clusters with severe wind and hail potential.
Even if surface-based diurnal development is suppressed, there will
be some potential for elevated convection to develop Sunday evening
into the overnight. Steep lapse rates, moderate elevated buoyancy,
and sufficient effective shear could support a hail threat with the
strongest elevated storms, and severe-wind potential with any
forward-propagating clusters that can develop Sunday night.
The Level-1/Marginal Risk has been expanded westward across ND and
far eastern MT to account for the conditional threat in these areas,
though confidence in the details of storm coverage and evolution
remains low at this time.
..Dean.. 07/17/2026
Read more
SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
0245 PM CDT Fri Jul 17 2026
Valid 181200Z - 191200Z
...Southeastern Wyoming...
Elevated highlights have been added to portions of southeastern WY
for Saturday. A large scale upper ridge over the central U.S. and
Intermountain West will promote unseasonably warm temperatures and
dry surface conditions to portions of the central and northern
Plains. A surface low developing in southwestern WY will aid in
stronger easterly low-level flow of 10-15 mph across eastern WY.
These winds along with minimum RH of 15-20% will support elevated
fire weather conditions over exceptionally dry fuels (ERC values
around the 95-98th percentile) Saturday afternoon.
...Columbia Basin, Idaho Panhandle, interior Oregon and adjacent
areas of California and Nevada...
Stronger mid-level southwest flow will linger over the Pacific
Northwest as an upper trough moves northeastward into British
Columbia. Dry, downslope flow in the lee of the Cascades and
northern Sierra Nevada will support RH of 15-20 percent by
mid-afternoon Saturday. These dry conditions along with receptive
fuels will support an elevated fire weather concern for the region
with impacts to active wildfires in the Pacific Northwest expected.
Latest model guidance suggests stronger surface winds across the ID
Panhandle Saturday under the 50-55 knot mid-level jet. This should
promote sustained winds of around 15 mph (locally higher favorable
terrain gaps) across the ID Panhandle Saturday. Due to potential for
impact from lightning ignitions from Day 1/Friday, extended elevated
highlights into ID Panhandle to cover this fire weather threat.
..Williams.. 07/17/2026
.PREV DISCUSSION... /ISSUED 0150 AM CDT Fri Jul 17 2026/
...Synopsis...
Between a midlevel trough moving across BC and an expansive
large-scale ridge over the central/western CONUS, enhanced
deep-layer south-southwesterly flow will overspread a deep/dry
boundary layer (around 10-15 percent RH) in the lee of the northern
Sierra and Cascades. These dry conditions combined with around 15
mph sustained west-southwesterly surface winds will favor elevated
fire-weather conditions during the afternoon, given dry/receptive
fuels.
...Please see www.spc.noaa.gov/fire for graphic product...
Read more
SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
0442 PM CDT Fri Jul 17 2026
Valid 191200Z - 251200Z
...Discussion...
A broad mid-level ridge will dominate over much of Intermountain
West through next week as troughing across the northeastern U.S.
amplifies midweek. Monsoon moisture trapped within weak flow under
the ridge and afternoon instability will support daily afternoon
showers and thunderstorms over higher terrain across the Colorado
River Basin and eastern Great Basin. This higher RH environment and
slow moving, terrain anchored convection will mitigate ignition
potential. Mainly dry conditions will persist across the interior
portions of the Pacific Northwest and CA through Day 4/Monday. Short
wave impulses on the western periphery of the upper ridge could
bring thunderstorms back into CA as early as Monday. Longer term
model guidance suggests better chances of dry thunderstorm impacts
for the Pacific Northwest emerging for the latter part of next week
as moisture from tropical storm Elida gets wrapped up in a
mid-latitude trough.
The building ridge aloft and lack of robust surface pressure
features across the West will keep winds relatively light across the
western coastal states where fuels are more receptive. Longer term
ensemble guidance suggests a return to breezy conditions across
portions of CA and the Pacific Northwest beginning Day 7/Thursday
where 40 percent critical probabilities have been added to
northeastern CA/southern OR. Ensemble cluster analysis suggests a
more inland push of an upper-trough into the Pacific Northwest on
Day 8/Friday, with a broader 40 percent critical probability area
introduced into much of central OR, northeastern CA and adjacent
northwest NV. The thunderstorm threat across CA and the Pacific
Northwest remains very sensitive to the expected track of a
subtropical moisture plume from tropical storm Elida. Thunderstorms
could threaten central/northern CA as early as Day 5/Tuesday, moving
into the Pacific Northwest by Day 7-8/Thursday-Friday. For this
outlook, introduced a 10 percent dry thunderstorm probability for
initial surge of subtropical moisture into northern CA and southern
OR, although this could change based on future model guidance.
..Williams.. 07/17/2026
...Please see www.spc.noaa.gov/fire for graphic product...
Read more
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