SPC Jul 17, 2026 1630 UTC Day 1 Convective Outlook

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


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


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SPC Jul 17, 2026 1300 UTC Day 1 Convective Outlook

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


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


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SPC Jul 17, 2026 0600 UTC Day 1 Convective Outlook

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


Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1258 AM CDT Fri Jul 17 2026

Valid 171200Z - 181200Z

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

...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 and southern Appalachians.

...Northern Rockies and Adjacent Plains...
An upper low over the Pacific Northwest is forecast to lift slowly
northward as an expansive upper ridge continues to build across the
western US. East of the low, a broad area of monsoon moisture will
persist over much of the Rocky Mountains. Weak ascent on the
periphery of the upper low and diurnal heating across the higher
terrain should allow for scattered thunderstorm development through
the afternoon. While displaced from the core of the stronger flow
aloft as the upper low drifts to the north, sufficient effective
shear of 25-35 kt will exist for occasional storm organization.
Isolated hail and severe gusts could accompany the strongest storms
into the evening across ID and western MT.

...Upper Midwest and northern Great Lakes...
An upper trough initially over AB/SK will move southward into the
northern Great Lakes by early Saturday. A belt of stronger mid-level
flow accompanying the upper trough will aid in deepening a surface
low as it moves into western ON. A warm front will lift north with
the deepening low over the Upper Midwest. A cold front trailing the
surface low will provide a focus for thunderstorm development over
northern MN, WI and the UP of MI this afternoon and evening.

A cluster of elevated thunderstorms is likely to be ongoing early in
the period near or just across the international border. These
storms could reinvigorate with a risk for some damaging gusts and
hail, though confidence in the convective evolution is low. Later in
the day ahead of the cold front, moderate buoyancy and sufficient
deep-layer shear will conditionally support a threat for isolated
supercells or organized multicell clusters, with a threat of hail
and damaging winds. Any persistent supercell may also pose at least
a brief tornado threat, especially in closer proximity to the
surface low and warm front where low-level shear will be maximized.

As the main upper trough continues to southeast 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...
A warm and seasonably moist air mass will support moderate to
locally strong buoyancy beneath the upper ridge from the OH valley
toward the Southeast and southern Appalachians. A weak, convectively
enhanced sub-tropical disturbance moving northward and the higher
terrain should focus more widespread diurnal thunderstorm activity
from portions of IN/OH, into eastern KY/TN, the western Carolinas
and northern GA. Despite weak deep-layer shear below 20 kt, moderate
to strong MLCAPE (2000-3000 J/kg) and PWATS exceeding 2 inches may
allow for sporadic damaging gusts with any stronger multicell
clusters.

...FL...
CAM guidance shows vigorous storm development just offshore of the
FL Gulf Coast Friday morning, in association with a weak midlevel
trough/low. Additional storm development is expected by afternoon
across much of the peninsula. Large buoyancy and high PWATs suggest
localized strong to severe gusts cannot be ruled out near the coast
and inland this afternoon.

..Lyons/Weinman.. 07/17/2026


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SPC Jul 17, 2026 0100 UTC Day 1 Convective Outlook

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


Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0759 PM CDT Thu Jul 16 2026

Valid 170100Z - 171200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
WESTERN MONTANA AND EASTERN NORTH DAKOTA INTO WESTERN MINNESOTA...

...SUMMARY...
Severe thunderstorms capable of producing large hail and gusty winds
remain possible across parts of the northern Rockies this evening.
Severe storms with hail and a tornado or two are also expcted over
parts of the Upper Midwest into tonight.

...Northern Rockies...
Evening water vapor imagery showed a very large upper ridge centered
over the CONUS, with a broad plume of monsoon moisture east of an
upper low off the coast of the Olympic Peninsula. Numerous
thunderstorms are ongoing over the Intermountain West and northern
Rockies this evening and should persist for several more hours
tonight.

The strongest of these storms, including some supercells, should
persist over parts of the eastern ID panhandle and western MT this
evening. Here, moderate buoyancy and 40+ kt of effective shear will
continue to favor storm organization. Hail is likely, along with
some potential for severe gusts given steep lapse rates in the lower
and middle troposphere.

...Eastern into western MN...
At the crest of the expansive upper ride, several weak vorticity
maxima and jet streak were migrating along the Canadian/ND border.
An effective warm front/modified outflow boundary was observed from
near the international border into western MN. South of the front,
surface temperatures in the 90s and dewpoints in the lower to middle
70s F are supporting a very unstable air mass with MLCAPE of
4000-5000 J/kg. Veering wind profiles along and south of the warm
front will favor supercells or organized clusters this evening into
tonight as developing convection spreads southeastward toward the
Red River Valley. Despite only modest mid-level lapse rates, strong
to extreme buoyancy and 35-40 kt of deep-layer vertical shear will
support a risk for large hail (some 2+ in) with dominant supercells.
Backed low-level flow and enhanced ESRH along the cool side of the
boundary could support a tornado or two as well.

The primary focus for the severe storms will be along the warm front
where convergence is maximized, though isolated storms ongoing
farther southwest are possible with a localized threat for hail and
damaging winds in the more strongly mixed air mass. A Level 2 Slight
Risk has been introduced to cover the increase in severe risk
through this evening from eastern ND into western MN.

...Elsewhere...
Strong to severe storms have largely exited the eastern seaboard
this evening. Additional disorganized storms over the southeastern
US and southern Plains should linger into the overnight hours while
steadily weakening. Waning buoyancy and meager deep-layer vertical
shear should limit severe potential.

..Lyons.. 07/17/2026


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