SPC May 29, 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
1253 AM CDT Fri May 29 2026

Valid 291200Z - 301200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
WESTERN TEXAS...

...SUMMARY...
Scattered strong to severe storms capable of sporadic large hail and
scattered severe winds are expected this afternoon and evening
across portions of western Texas. More isolated severe thunderstorms
are likely across parts of the central High Plains, southern Utah,
and the northern Rockies.

...Synopsis...
Late-evening water-vapor imagery reveals an upper low over central
CA with a subtropic jet emanating out of Baja CA into the southern
Rockies. Over the next 24 hours both of these features will migrate
east/northeast into the central and southern High Plains. Despite
some weakening of the upper wave, 25-35 knot mid-level flow will
overspread the central and southern High Plains where low-level
moisture is gradually increasing within a weak east/southeasterly
flow regime. The combination of modest broad-scale ascent and
strengthening deep-layer shear atop a moistening low-level air mass
should support the potential for a few strong to severe
thunderstorms during and after peak heating from southern TX
northward across the southern Plains and into parts of the central
High Plains.

Elsewhere, orographic ascent within the northern Rockies will
support another day of isolated to widely scattered thunderstorms,
including a few severe storms. A migratory upper trough over the
central CONUS will continue to support scattered, but weak,
thunderstorms across the OH Valley and Southeast states this
afternoon.

...Southern Plains and central High Plains...
Thunderstorm development is expected by mid-afternoon across western
TX into eastern CO along a modestly deepening lee surface trough
where ascent should be focused and mixed-layer inhibition minimized.
Slightly stronger synoptic ascent across the southern High Plains
should promote higher thunderstorm coverage across western TX/TX
Panhandle region with more isolated coverage with northward extent.
15% wind probabilities were introduced across portions of western TX
to reflect the potential for higher storm coverage.

Across both the southern and central High Plains warm low-level
conditions/deep boundary-layer mixing combined with weak flow within
the lowest 1-3 km will likely promote outflow dominant storms with
an attendant threat for severe gusts. Stronger mid-level flow across
western TX may support a more prolonged severe threat, and possibly
a few transient supercells capable of large hail and/or organized
bands capable of gusts upwards of 75 mph. Through the late evening,
isentropic ascent near the terminus of the nocturnal jet may support
elevated, loosely organized convection across portions of northwest
OK and western KS.

...Northern Rockies/Montana...
Diurnally-driven orographic ascent within the terrain of northern ID
and southwest MT will likely support isolated thunderstorm
development by late afternoon given weak capping and northward
advection of steep mid-level lapse rates. Residual low-level
moisture across north-central MT (dewpoints in the upper 40s to low
50s) coupled with 30-35 knot southerly mid-level flow will likely
promote intensification and some degree of organization (possibly
into transient supercells and/or organized bands) through the early
evening hours. Sporadic large hail and severe gusts appear possible
with the most intense convection as it spreads north towards the
Canadian border.

...Southern Utah...
5% wind probabilities were introduced across southern to southeast
UT where weak, high-based convection may support a few strong to
severe dry downbursts. Although latest CAM ensemble guidance depicts
scant buoyancy (MUCAPE between 100-250 J/kg) and very transient
convection, a very deep boundary layer (LCL values upwards of 3 km)
featuring 25-35 knot flow will likely promote sporadic strong to
severe wind gusts.

..Moore/Marsh.. 05/29/2026


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SPC May 29, 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
0754 PM CDT Thu May 28 2026

Valid 290100Z - 291200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS NORTHERN
OREGON INTO EASTERN WASHINGTON AND NORTHERN IDAHO...

...SUMMARY...
Scattered severe thunderstorms remain possible this evening east of
the Cascades in Washington and Oregon into western Idaho and
Montana. The primary hazards will be large hail and scattered severe
wind gusts.

...Synopsis...
As of 01 UTC, scattered to widespread thunderstorms continue to
develop ahead of an inverted trough axis from central OR (where a
more focused vorticity maximum is noted in GOES imagery) into
north-central MT. More isolated and short-lived convection continues
to develop within a weak up-slope flow regime along the CO front
range. While the potential for severe convection should quickly wane
after 03 UTC across the central High Plains, a severe hail and wind
threat will persist through late evening across the Pacific
Northwest.

...Pacific Northwest...
Regional radar depicts a myriad of convective modes ranging from
broken bands across central OR to splitting supercells across
eastern WA, ID, and northwest MT. This activity will continue to
spread northwestward as the inverted mid-level trough shifts west
towards the Pacific Northwest coast through tonight. A combination
of surface dewpoints in the 50s and cool mid-level temperatures
(associated with the mid-level trough axis) continue to support
MLCAPE values on the order of 1000-2000 J/kg. This buoyancy axis
should spread northwest in tandem with ongoing storms and help
maintain some degree of intensity over the next several hours.

Per regional VWP observations, mid-level winds across WA/ID remain
near 40-50 knots with decreasing magnitudes with northward extent
into eastern WA and northern ID. Despite the weaker deep-layer wind
shear, dewpoint depressions on the order of 25-30 F hint that a
deeply-mixed boundary layer remains in place downstream of
approaching storms. The onset of nocturnal cooling should be too
shallow/insufficient to offset downdraft accelerations through the
lowest 1-2 km as convection spreads northwest and cold pools begin
to amalgamate. Recent CAM guidance shows fairly strong agreement in
a substantial wind threat spreading north/northwestward across
eastern WA and northern ID later this evening. Consequently, 15%
wind and the intensity level 1 contour have been expanded to account
for this potential.

...Colorado...
Convection across the CO Front Range has been fairly transient and
tied to the terrain over the past couple of hours, largely due to
the weak up-slope flow regime. However, latest GOES imagery
continues to show deep cumulus development in proximity to the
Denver area, and recent RAP mesoanalysis show sufficient deep-layer
wind shear for at least transient organized convection capable of a
brief large hail threat. This environment, and the overall severe
threat, should wane through 03 UTC.

..Moore.. 05/29/2026


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SPC May 28, 2026 2000 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 2000Z Day 1 Outlook


Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0300 PM CDT Thu May 28 2026

Valid 282000Z - 291200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ...

...SUMMARY...
Scattered severe thunderstorms remain possible this afternoon and
evening over western Idaho and east of the Cascades in Washington
and Oregon, capable of damaging gusts, large hail, and perhaps a
tornado.

...20Z Update...
The previous forecast (see below) remains on track.

..Squitieri.. 05/28/2026

.PREV DISCUSSION... /ISSUED 1108 AM CDT Thu May 28 2026/

...WA/OR/ID...
Morning water vapor imagery shows an upper low over central CA, with
a strong shortwave trough rotating around the low over central NV.
This feature is forecast to move into ID/OR later today, with an
associated 40-50 knot mid level jet affecting the area. Strong
heating, dewpoints in the upper 40s-lower 50s, and steepening
mid-level lapse rates will lead to moderate CAPE values over much of
western ID into central WA/OR, setting the stage for afternoon
thunderstorms. Activity is expected to first develop across
southwest ID/southern OR, where sufficient vertical shear would
support supercell structures capable of large hail and damaging wind
gusts. Morning CAM guidance suggests activity will organize into
multiple clusters by evening, tracking northwestward across the
Columbia Basin into western/central WA. These storms would continue
to pose a damaging wind threat.

...CO...
Strong heating and sufficient low-level moisture will likely result
in widely scattered thunderstorms in the foothills of the Front
Range this afternoon. The strongest cells could produce hail.

...KS...
A remnant weak vorticity max is tracking northward near the OK/KS
border. Southeasterly low-level winds to the north of the vort max
may result in sufficient shear for weak rotation in a few storms
later today. While a brief spin-up over north-central KS cannot be
ruled out, the overall threat appears too weak for outlook
probabilities today.


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SPC May 28, 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
0753 AM CDT Thu May 28 2026

Valid 281300Z - 291200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR WESTERN IDAHO
INTO CENTRAL AND EASTERN PORTIONS OF OREGON AND WASHINGTON...

...SUMMARY...
Scattered severe thunderstorms are possible over western Idaho and
east of the Cascades in Washington and Oregon. Severe gusts (60-85
mph), large hail, and perhaps a tornado are the forecast hazards
this afternoon through the late evening.

...Columbia Basin vicinity into ID/northern NV...
A mid- to upper-level low over the Sierra Nevada will move little
during the period. Water-vapor imagery this morning indicates a
disturbance over NV will move north and northwestward through
eastern NV into eastern OR by early evening. In the low levels, an
area of low pressure is forecast to develop by late afternoon and
migrate from the ID/OR border into the Columbia Basin.

A plume of steep 700-500 mb lapse rates arc around the northern
periphery of the western U.S. low and extend from the Snake Valley
westward into OR/WA. As heating of a seasonably moist airmass
occurs, initial thunderstorm activity will gradually shift from
south to north from northern NV/southern ID and southern OR. Model
forecast soundings show steep low to mid tropospheric lapse rates
favorable for evaporative cooling and the development of strong to
severe downdrafts. Slightly greater buoyancy is shown in model
guidance farther north in northern OR into western ID (1500 J/kg
MLCAPE). As storms move into this region during the late afternoon
to evening timeframe, it is possible a more extensive threat for
severe gusts develops. Regardless, severe outflow both with the
stronger cores and linearly oriented clusters appear to be the main
hazard. Large hail may accompany the stronger cells. A continued
threat for scattered severe gusts may occur into the late evening as
this activity shifts northward into interior portions of WA.

...East-central Colorado...
A mid-level trough will move northward across the central Plains
today. At the surface, upslope east-southeasterly flow will be in
place across eastern Colorado. Along the Front Range, the Denver
cyclone is expected to develop by afternoon. Topographic lift and
increasing low-level convergence will result in scattered
thunderstorm development from the Palmer Divide northward into
north-central Colorado. Forecast soundings along this corridor by
late afternoon have 0-6 km shear in the 20 to 30 knot range with
700-500 mb lapse rates around 8 C/km. This should support a hail
threat with the stronger cells.

..Smith/Weinman.. 05/28/2026


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