Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1250 AM CDT Thu Jun 12 2025
Valid 121200Z - 131200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS TODAY INTO
TONIGHT ACROSS PARTS OF THE GREAT PLAINS...THE UPPER
MIDWEST...SOUTHEASTERN TEXAS INTO THE LOWER MISSISSIPPI VALLEY AND
PARTS OF THE NORTHERN MID ATLANTIC...
...SUMMARY...
Scattered areas of strong thunderstorm development are possible
today into tonight, accompanied by potential for severe hail and
wind across parts of the Great Plains, the Upper Midwest, the Texas
coastal plains into lower Mississippi Valley and a small portion of
the northern Mid Atlantic.
...Discussion...
Split westerlies across the mid- and higher latitudes of the eastern
Pacific into North America include broad, weak troughing across the
northeastern Pacific into British Columbia and the Pacific
Northwest. Models suggest that this cyclonic flow may undergo some
amplification later today through tonight, as an embedded short wave
perturbation pivots into the Pacific Northwest, to the south of a
slow moving low near/offshore of the northern British Columbia
coast.
Downstream, short wave ridging is forecast to shift across the
Canadian Prairies and east of the northern U.S. Rockies. However,
it appears a residual belt of (relatively) stronger flow will linger
above a stalled frontal zone across parts of the middle Missouri
Valley, into a confluent regime across the northern Mid Atlantic, to
the south of large-scale mid/upper troughing across the eastern
Canadian provinces.
It appears that seasonably high moisture content will largely remain
confined to the southern mid- and subtropical latitudes, where
ridging will remain suppressed, but westerlies will remain modest to
weak. One larger-scale trough within this regime is forecast to
slowly shift east of the southern Great Plains and northwest Gulf
coast, toward the Mississippi Valley today through tonight.
...Northern Rockies into Upper Midwest...
Despite seasonably modest boundary-layer moisture, models indicate
that lower/mid-tropospheric lapse will become sufficiently steep to
support at least pockets of mixed-layer CAPE in excess of 1000 J/kg,
along/south of the stalled frontal zone across the Big Horns and
Black Hills vicinity into the Upper Midwest, and within lee surface
troughing across/northeast of the Cheyenne Ridge. Aided by forcing
for ascent and shear associated with a couple of smaller scale
mid-level perturbations/speed maxima (40-50+ kt at 500 mb)
progressing through the belt of westerly flow, the environment may
become conducive to organized convective development this afternoon
and evening. This may include widely scattered supercells and small
upscale growing clusters posing a risk for severe hail and wind.
...Northern Mid Atlantic...
The development of mixed-layer CAPE on the order of 1000-2000 J/kg
also appears possible with daytime heating of a moistening
boundary-layer, along the southern slopes of the higher terrain of
north central through northeastern Pennsylvania by late this
afternoon. Although forcing for ascent to support thunderstorm
initiation remains unclear, deep-layer shear beneath the southern
fringe of seasonably strong westerlies will likely be conditionally
supportive of organized convection capable of producing severe hail
and wind, before the instability wanes late this evening.
...Southern Rockies into adjacent Great Plains...
Downstream of the large-scale mid/upper troughing developing inland
of the Pacific coast, models indicate a generally weak but difluent
downstream flow will prevail across the southern Rockies. There is
a notable signal within the model output that forcing for ascent
will become supportive of widespread thunderstorm development along
the Front Range and Sangre de Cristo Mountains by mid to late
afternoon. Although propagation off the higher terrain will
probably be initially slow, due to modest downstream
destabilization, model forecast soundings indicate that a warm and
deeply mixed boundary layer will become supportive of a few strong
downbursts to the lee of the higher terrain. Consolidating and
strengthening outflow may support strengthening surface cold pools
with a continuing risk of strong to severe gusts into portions of
the adjacent high plains through this evening.
...Texas Coastal Plains into lower Mississippi Valley...
An increase in thunderstorm development gradually continues across
and east of the I-35 corridor of central Texas, aided by forcing for
ascent associated with a short wave impulse progressing through the
weak larger-scale mid-level trough. It appears that this will
continue into the Texas coastal plain, where inflow of seasonably
high moisture content characterized by sizable CAPE may support
considerable gradual further intensification through 12Z.
To differing degrees, the various model output suggests that this
may be accompanied by a developing lower/mid-tropospheric cyclonic
circulation, and associated augmentation of the wind fields, that
will tend to advect north-northeastward toward the Ozark Plateau/Mid
South today. Preceded by a developing corridor of moderately large
CAPE with daytime heating, it is possible that the environment could
become conducive to organizing convection with potential to produce
strong to severe surface gusts, and perhaps potential for a couple
of brief tornadoes.
..Kerr/Squitieri.. 06/12/2025
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