SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0257 PM CDT Fri Jun 13 2025
Valid 132000Z - 141200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FOR PARTS OF
CENTRAL AND SOUTHERN MONTANA...
...SUMMARY...
Scattered severe thunderstorms are expected this afternoon and
evening across parts of Montana, extending southward across portions
of the central/southern High Plains. The greatest concentration of
severe thunderstorms should occur across central/southern Montana,
where large to very large hail, severe winds, and a couple tornadoes
will be possible.
...20z Update...
The forecast largely remains on track with only minor adjustments
required for this update.
...Lower MS River Valley...
Wind probabilities have been trimmed behind a broken line of
convection spreading eastward into far eastern MS. Behind this line,
an expansive cold pool/convective overturning has sufficiently
reduced buoyancy to limit the potential for additional severe
convection. Ahead of the cold pool to the northeast, the convective
environment remains supportive of at least an isolated wind threat
(see MCD #1272 for additional details).
...Southern High Plains...
Wind probabilities have been expanded westward closer to the higher
terrain across NM. Early attempts at sustained convection are
ongoing from south-central CO into southern NM per latest visible
imagery. Although moisture quality immediately off the terrain
remains very limited (dewpoints in the upper 40s/low 50s), deep
boundary-layer mixing denoted by 40-50 F dewpoint depressions may
promote downdraft accelerations with an attendant severe wind risk.
The past several HRRR/RRFS solutions have consistently shown a
signal for at least sporadic severe gusts with this early
convection. Severe gusts should become more probable with eastward
extent later this evening as convection migrates into the deeper
moisture along the NM/TX border.
...Central Oklahoma to western Arkansas...
Early-morning convection has largely eroded across OK and far
western AR; however, surface observations and visible imagery reveal
a residual outflow boundary/differential heating zone draped from
north-central OK to western AR. Some building cumulus is noted as
temperatures warm into the upper 80s within a very moist air mass.
The KSRX and KINX VWPs continue to sample 30-35 knot mid-level flow,
which may be sufficient for organized cells if convection can
develop along this boundary later this afternoon/evening.
Additionally, increasing isentropic ascent between 925-850 mb late
tonight may support additional thunderstorms across OK.
..Moore.. 06/13/2025
.PREV DISCUSSION... /ISSUED 1126 AM CDT Fri Jun 13 2025/
...Central/southern MT this afternoon/evening...
Embedded speed maxima will progress east-northeastward over the
northern Rockies, with associated bands of ascent denoted by weak
convection now over ID. Surface heating along and southwest of a
baroclinic zone oriented from north central into southeast MT, and
arrival of the bands of ascent from ID will contribute to
thunderstorm development by early afternoon over the higher terrain
of southwest MT. Storms will then spread eastward through the
afternoon/evening, in an environment supportive of supercells on the
northeast edge of the steeper midlevel lapse rates, in a corridor
with long hodographs/effective bulk shear in excess of 50 kt. The
strong deep-layer shear and moderate buoyancy (MLCAPE near 1500
J/kg) will favor large hail production, some greater than 2 inch
diameter with the supercells, as well as damaging outflow gusts that
could reach or exceed 75 mph. A couple of tornadoes will also be
possible, though relatively deep mixing and relatively straight
hodographs cast some doubt on the tornado threat.
...High Plains this afternoon into early tonight...
Despite being near the crest of the midlevel ridge, sufficiently
moist, low-level upslope flow and steep midlevel lapse rates will
support thunderstorm development near and east of the lee trough
from eastern WY to eastern CO/western KS and the northern TX
Panhandle later this afternoon/evening. Deep mixing, steep lapse
rates, and relatively weak vertical shear all support initial storms
growing upscale into clusters through outflow interactions, and the
clusters will spread southeastward into tonight. Isolated large
hail will be possible with the stronger embedded storms, while
severe outflow gusts will become the main concern with storm
clusters this evening into early tonight.
...MS/AL to KY this afternoon...
East of a weak midlevel trough from east TX to MO, modest
enhancement of midlevel flow (to roughly 30-35 kt) and daytime
heating of a moist air mass will contribute to scattered
thunderstorm development through the afternoon from southeast LA/MS
across northwest AL, TN and KY. MLCAPE of 1500-2500 J/kg and the
aforementioned enhancement to midlevel flow will support storm
clusters/line segments with some potential for isolated wind damage
this afternoon.
...Mid-Atlantic this afternoon...
Strong surface heating is underway to the south of a slow-moving
front from DE into northern MD, which will steepen low-level lapse
rates and boost MLCAPE to 1000-1500 J/kg this afternoon. Scattered
thunderstorm development is possible along the front and the Blue
Ridge, and storms will spread eastward through late
afternoon/evening. The moderate buoyancy, steep low-level lapse
rates and modest deep-layer vertical shear (effective bulk shear of
25-30 kt) will support some storm/cluster organization and the
potential for isolated wind damage.
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