SPC Jun 16, 2025 1300 UTC Day 1 Convective Outlook

SPC 1300Z Day 1 Outlook

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0754 AM CDT Mon Jun 16 2025

Valid 161300Z - 171200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE CENTRAL PLAINS AND UPPER MIDWEST...

...SUMMARY...
Scattered severe thunderstorms capable of producing severe/damaging
gusts, large to very large hail, and a few tornadoes are forecast
today across parts of the northern/central Plains into the Upper
Mississippi Valley.

...Upper Mississippi Valley...
With ongoing thunderstorms across parts of MN this morning,
confidence is lower than usual regarding severe potential and
convective evolution later today across MN into WI. A decayed MCS
over western MN this morning and a related MCV/surface low over ND
will continue to track northeastward across MN through the day. A
seasonably moist low-level airmass, with surface dewpoints generally
in the low to mid 60s, is present this morning across southern MN.
Some northward advance of this low-level moisture across parts of
central/northern MN is anticipated through the afternoon in advance
of the MCV and a convectively reinforced front/outflow. Filtered
daytime heating of this airmass should result in at least moderate
instability developing in a narrow corridor, with robust convective
development increasingly likely by 20-22Z.

There is still a fairly high degree of uncertainty regarding how far
south intense thunderstorms will develop across MN/eastern SD this
afternoon/evening. Somewhat greater confidence in severe
thunderstorms exists in closer proximity to the MCV across central
into northern MN. Have therefore expanded severe probabilities
northward a bit across this area. Initial development will likely be
supercellular given around 35-45 kt of deep-layer shear forecast,
with an associated threat for scattered large to very large hail
(isolated 2+ inches in diameter possible). Sufficient low-level
shear is also forecast with the MCV to support a threat for a few
tornadoes, especially along an effective warm front that should be
draped generally west to east across central/northern MN. By early
evening, some upscale growth/clustering may occur, with an increased
risk for severe/damaging winds into eastern MN/western WI and
vicinity. Convection should eventually weaken with eastward extent
across the Upper MS Valley tonight as it moves into a less unstable
airmass.

...Northern/Central Plains...
Modest post frontal, low-level upslope flow will occur today across
parts of the northern Rockies/High Plains. Convective initiation
should initially occur along/near the higher terrain in southern MT
and northern/eastern WY by mid to late afternoon. A subtle mid-level
shortwave trough embedded within otherwise modestly enhanced
southwesterly flow should aid in this thunderstorm development.
Steep low/mid-level lapse rates are expected to be in place across
this region, with daytime heating contributing to moderate
instability. Strong deep-layer shear around 40-50 kt is expected,
with elongated/nearly straight hodographs at mid/upper levels
supporting ample speed shear. Isolated to widely scattered
supercells will likely pose a threat for large to very large hail as
they develop east-southeastward over the northern High Plains this
afternoon and early evening. If a cluster or two can develop this
evening, then severe wind gusts would be possible given steepened
low-level lapse rates and a well-mixed boundary layer.

Additional robust thunderstorms will probably form this afternoon
along/near a convectively reinforced front that should be draped
generally northeast to southwest over NE, and separately across the
higher terrain of eastern WY/northern CO. Strong to locally extreme
instability is likely to develop along/south of this boundary with
strong diurnal heating of a moist low-level airmass and the presence
of steep mid-level lapse rates. Sufficient deep-layer shear should
also exist to support some updraft organization, with a mix of
supercells and multicell clusters possible. Initial development
should pose some threat for large to very large hail. Multiple
opportunities for clustering and swaths of severe/damaging winds
(isolated 75+ mph possible in western/central NE) remain apparent,
both with the convection that develops along the surface boundary in
NE, and with thunderstorms spreading east-southeastward from the
northern/central High Plains. A small southward expansion to the
Enhanced Risk has been made based on latest guidance trends. But,
confidence remains low in exactly how convective clusters will
evolve this afternoon/evening.

..Gleason/Kerr.. 06/16/2025

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