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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SPC May 28, 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 Thu May 28 2026

Valid 281200Z - 291200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE PACIFIC NORTHWEST...

...SUMMARY...
Thunderstorms with severe wind gusts, large hail and an isolated
tornado threat are expected across parts of the Pacific Northwest
this afternoon and evening.

...Pacific Northwest...
An upper-level low will remain over central California today. On the
northern periphery of the system, bands of large-scale ascent will
move westward across the Pacific Northwest, providing support for
thunderstorm development. At the surface, a low will deepen and move
northwestward from eastern Oregon into southern Washington. A
surface trough will extend southward from the low into north-central
and west-central Oregon. Thunderstorms are forecast to first develop
across southern Oregon around midday, with convective coverage
gradually increasing over much of Oregon during the afternoon. A
larger-scale line segment is expected to organize and move
northwestward across Oregon late this afternoon and into southern
Washington early this evening.

As surface temperatures warm today, instability will increase along
the surface trough with MLCAPE expected to peak in the 1200 to 1500
J/kg range. The instability combined with 30 to 40 knots of
mid-level east-southeasterly flow, along with low to mid-level lapse
rates in the 8 to 8.5 C/km range, will support severe thunderstorm
development. This environment will be favorable for severe wind
gusts and isolated large hail within the stronger parts of an
extensive line segment. Near the surface trough, 0-3 km
storm-relative helicity is forecast to increase into the 200 to 250
m2/s2 range by late afternoon, which could also support an isolated
tornado threat. Any tornado threat would mainly be associated with
rotating elements embedded in the line. As the line moves
north-northwestward and expands, a severe threat is expected to move
into southern Washington by early evening. A marginal severe threat
could impact parts of central and northern Washington later in the
evening.

...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.

..Broyles/Chalmers.. 05/28/2026


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SPC May 28, 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
0756 PM CDT Wed May 27 2026

Valid 280100Z - 281200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE MID-ATLANTIC...

...SUMMARY...
Thunderstorms will severe wind gusts and hail will be possible this
evening from parts of the Mid-Atlantic into central Appalachians.
Isolated severe gusts and hail may also occur in central Wisconsin
and in parts of the Northwest.

...Mid-Atlantic/Central Appalachians...
An upper-level trough, evident on water vapor imagery, is moving
southeastward through the Great Lakes. At the surface, a cold front
is advancing southward across the Ohio Valley and central
Appalachians. To the south of the front, surface dewpoints are in
the upper 60s to lower 70s F. The RAP has MLCAPE in the 1000 to 1500
J/kg range from eastern Kentucky eastward into southern Virginia and
across much of North Carolina. Within this area, scattered
thunderstorms with an isolated severe threat are ongoing. Forecast
soundings in the Mid-Atlantic early this evening have moderate
deep-layer shear and steep low-level lapse rates. This suggests the
potential for severe wind gusts will continue for a couple more
hours with the more organized clusters.

...Central Wisconsin...
At the surface, a pocket of moisture and instability is located over
central Wisconsin early this evening, where the RAP has MLCAPE in
the 500 to 1500 J/kg range. Forecast soundings near the instability
max have 0-3 km lapse rates near 7.5 C/km and sufficient deep-layer
shear for a marginal severe threat. Isolated severe gusts and hail
will be possible for another hour or so.

...Northwest...
At mid-levels, a low is evident on water vapor imagery over central
California, and flow is from the southeast and east over much of the
northwestern U.S. Thunderstorms are ongoing ahead of a band of
strong large-scale ascent from far northern California into
south-central Oregon. The environment is characterized by moderate
deep-layer shear and steep lapse rates, suggesting a threat for
isolated severe wind gusts will continue. Additional storms are
ongoing near a pocket of moderate instability in northern Idaho and
western Montana, where a few severe wind gusts will also be
possible.

..Broyles.. 05/28/2026


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SPC May 27, 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
0745 AM CDT Wed May 27 2026

Valid 271300Z - 281200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE MID-ATLANTIC...

...SUMMARY...
Scattered severe thunderstorms are possible across parts of the
Mid-Atlantic states this afternoon into the early evening. Strong
to severe gusts (50-65 mph) capable of wind damage will be the
primary hazard with the stronger thunderstorms.

...Mid-Atlantic/Ohio Valley...
An upper-level trough over the Great Lakes will move southeast
towards the upper OH Valley/Mid-Atlantic states during the period.
Water-vapor imagery this morning shows a lead disturbance over
southern OH moving east across the central Appalachians. In the low
levels, an analyzed frontal zone has been modulated by ongoing
showers/thunderstorms and it will move southeast today. A moist
airmass ahead of the front, featuring dewpoints in the upper 60s to
lower 70s F, will gradually destabilize through early afternoon.
East-southeastward moving clusters are forecast to evolve by later
this afternoon. Scattered strong to severe gusts (50-65 mph)
capable of wind damage will be the primary risk with the stronger
thunderstorms, although marginally severe hail may accompany the
stronger cores this afternoon.

...Southern ID into eastern OR...
A belt of strong easterly mid-level flow will remain over southwest
ID into southeast OR to the north of a stationary, deep-layer
cyclone over the Sierra Nevada. Heating of an adequately moist
boundary layer will steepen low-level lapse rates by early
afternoon. Widely scattered to scattered thunderstorms are forecast
to develop this afternoon. Forecast hodographs show 20-45 kt
700-500 mb flow (strongest over southeast OR) and mean storm motions
35-45 kt. These flow fields coupled with evaporatively cooled
downdrafts will likely result in a mix of quickly moving cells and
smaller-scale linear clusters. This activity will potentially be
capable of severe gusts (60-75 mph) before diminishing by mid-late
evening.

...Western Great Lakes...
Northwesterly mid-level flow will be in place across the western
Great Lakes today, as a shortwave trough moves southeastward across
the region. At the surface, a pocket of maximized low-level
moisture will be located over Wisconsin, where MLCAPE is expected to
peak in the 1500 to 2500 J/kg range. An isolated risk for large
hail/damaging gusts are possible with the stronger thunderstorms.

...Southern Texas Panhandle/West Texas/Far Western Oklahoma...
Somewhat displaced from an expansive overnight MCS along the TX
coast, an airmass featuring upper 50s to lower 60s F dewpoints will
destabilize beneath a weak mid- to upper-level trough. Widely
scattered to scattered storms are forecast to develop by late
afternoon and aggregate into small clusters this evening. Isolated
large hail/severe gusts are the primary severe hazards.

..Smith/Weinman.. 05/27/2026


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