Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0731 AM CDT Fri Jul 17 2026

Valid 171300Z - 181200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF
THE NORTHERN ROCKIES AND HIGH PLAINS...UPPER GREAT LAKES...AND 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 gusts are possible over parts of the
Ohio Valley into parts of the Southeast.

...Northern Rockies and adjacent High Plains...
To the east of an upper low near the WA/Vancouver vicinity, an upper
ridge with a plume of monsoonal moisture will extend northward from
the Great Basin into the northern Rockies and adjacent High Plains. 
Orographic lift and heating will promote the development of
scattered thunderstorms this afternoon.  Steepened low-level lapse
rates will potentially yield storms capable of isolated severe gusts
beginning this afternoon and continuing into the mid-late evening. 
Isolated large hail may occur with the stronger thunderstorm cores,
especially over northwest MT where 0-6 km shear will be 25-35 kt.

...Upper Midwest and northern Great Lakes...
A cluster of weak thunderstorms over the MN Arrowhead will likely
move southeast this morning ahead of an amplifying upper trough
forecast to move from northern SK to the Upper Peninsula of MI
during the period.  A cold front associated with the upper wave will
push southeastward across the Upper Midwest and provide a focus for
thunderstorms later this afternoon and evening.  

A warm frontal zone draped across the northern Great Lakes will
advance northeastward as a low over western ON moves eastward into
central ON by early evening.  Forecast model guidance shows moderate
buoyancy developing today within a belt of 25-40 kt
west-northwesterly 500-mb flow.  As a result, a few of the stronger
thunderstorms will probably evolve into supercells and organized
multicell clusters.  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.  However, confidence in this scenario is lower owing to the
prior convection and uncertainties of diurnal development along the
cold front.  Still, a strengthening wind field and ample moisture
could support a risk for damaging winds into northern Lower MI
overnight.

...OH Valley to the southern Appalachians and FL...
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 TX...
A weak mid- to upper-level low over west TX will move little during
the day while a warm/moist conveyor persists across southern into
central parts of TX.  An ongoing thunderstorm cluster will likely
continue across the Concho Valley aided in part by a convectively
augmented zone of low-level warm-air advection.  Despite very moist
low levels and some enlargement of the low-level hodograph per KSJT
and KDFX VAD data, weak flow in the mid levels will likely promote
enough convective outflow to limit storm organization (i.e.,
transient storm-scale cyclonic shear) and favor a heavy rain threat.

..Smith.. 07/17/2026

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1130 AM CDT Fri Jul 17 2026

Valid 171630Z - 181200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF
THE NORTHERN ROCKIES AND HIGH PLAINS...UPPER GREAT LAKES...AND OHIO
VALLEY TO 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.

...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.

..Guyer/Thompson.. 07/17/2026

Day 1 Fire Weather Outlook  
NWS Storm Prediction Center Norman OK
1138 AM CDT Fri Jul 17 2026

Valid 171700Z - 181200Z

No significant changes to existing elevated highlights were needed.
Dry and breezy surface conditions bolstered by a mid-level low and
associated stronger flow aloft are expected across the Columbia
Basin and northeastern CA, southern OR and northwestern NV. RH as
low as 10% percent can be expected, particularly in the lee of the
Cascades where downslope drying effects will be more pronounced.
West to southwesterly winds of 10-15 mph will evolve this afternoon
as a well-mixed and dry boundary layer develops in the wake of
exiting monsoon moisture. The elevated fire weather conditions could
impact nascent wildfires in OR.

..Williams.. 07/17/2026

.PREV DISCUSSION... /ISSUED 0149 AM CDT Fri Jul 17 2026/

...Synopsis...
A midlevel low will move northward along the Pacific Northwest coast
today. Between this feature and an expansive upper ridge over the
Rockies and Great Basin, a belt of enhanced south-southwesterly
low/mid-level flow will overspread the northern Great Basin and
Northwest. Downslope-enhanced warming/drying in the lee of the
northern Cascades and Columbia Basin will result in deep
boundary-layer mixing (10-15 percent RH). These warm/dry conditions
combined with around 15 mph sustained southwesterly winds atop
receptive fuels will yield elevated fire-weather conditions during
the afternoon.

...Please see www.spc.noaa.gov/fire for graphic product...