290 
ACUS03 KWNS 201856
SWODY3
SPC AC 201855

Day 3 Convective Outlook  
NWS Storm Prediction Center Norman OK
0155 PM CDT Fri Jun 20 2025

Valid 221200Z - 231200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM CENTRAL
NEBRASKA INTO THE UPPER MIDWEST...

...SUMMARY...
Severe thunderstorms may develop on Sunday from parts of the central
and northern Plains into the upper Midwest.

...Synopsis...
A strong mid-level ridge will amplify further across the eastern
CONUS on Sunday with a weak mid-level shortwave trough traversing
the northeast. A trough across the west will start to weaken and
move into the northern Plains during the period. At the surface,
troughing will extend along a frontal zone from northern Minnesota
to the central High Plains on Sunday. 

...Great Plains into the Upper Midwest...
Very strong to extreme instability is forecast to develop across the
central and northern Plains on Sunday. However, very warm low-mid
level temperatures should keep the warm sector mostly capped for
much of the day. Therefore, thunderstorm development should be
mostly confined to the front. However, even along the frontal zone,
storm coverage may be mostly isolated given that forcing from the
mid-level trough may remain mostly northwest of the frontal zone. In
addition, the strong mid-level flow is forecast to remain mostly
post-frontal which may limit storm organization across Nebraska and
South Dakota.

Given the somewhat decoupled upper-level and low-level pattern, the
severe storm threat is more conditional across eastern South Dakota,
Nebraska, and southwest Minnesota with the higher probability storm
threat across eastern North Dakota and northern Minnesota where
cooler temperatures aloft, stronger shear, and stronger forcing
should be present. Severe wind gusts would be the most likely threat
from this activity. 

...Parts of the Northeast...
Storms may be ongoing at the beginning of the period across the
Northeast as a mid-level shortwave trough shifts southeast. These
storms could be marginally severe with some damaging wind threat. In
the wake of this convection, very strong to extreme instability is
expected to build into the Northeast, but very warm lower
tropospheric temperatures and building heights aloft should suppress
additional afternoon thunderstorms.

..Bentley.. 06/20/2025

$$


File: /home/ldm/var/data/BY_SOURCE/KWNS/ACUS03/20250620T1856.txt



892 
ACUS03 KWNS 200731
SWODY3
SPC AC 200730

Day 3 Convective Outlook  
NWS Storm Prediction Center Norman OK
0230 AM CDT Fri Jun 20 2025

Valid 221200Z - 231200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM CENTRAL NE
INTO NORTHWEST IA...THE EASTERN DAKOTAS...AND WESTERN/CENTRAL MN...

...SUMMARY...
Severe thunderstorms may develop on Sunday from parts of the central
and northern Plains into the upper Midwest.

...Synopsis...
A mid/upper-level shortwave trough and attendant jet maximum are
forecast to move from the central Rockies towards the northern Great
Plains on Sunday. A surface low will move from NE/SD northeast
toward Lake Superior, as a trailing cold front moves through parts
of the northern/central Plains. Downstream, an upper ridge will
amplify further across the eastern CONUS through the day, as a
shortwave trough initially over New England moves offshore. 

...Great Plains into the Upper Midwest...
Strong to extreme instability is again forecast to develop
along/ahead of the cold front across parts of the central/northern
Plains into the Upper Midwest. Guidance generally suggests that
stronger ascent and deep-layer flow associated with the ejecting
mid/upper-level shortwave trough may lag behind the front, resulting
in some uncertainty regarding the magnitude and coverage of the
severe threat. However, strong diurnal heating will support
potential for storm development in the vicinity of the front, and
also southward along a surface trough into the central and perhaps
southern High Plains.  

Given the magnitude of instability, deep-layer shear will be
sufficient for some storm organization, with a few strong cells or
clusters possible. A Slight Risk has been added from central NE into
MN, where confidence is currently greatest in development of widely
scattered strong to severe storms during the afternoon and evening.
Convection may persist into late Sunday night, with an isolated
severe threat spreading gradually eastward. 

Isolated severe storms will also be possible within the post-frontal
regime across the central/northern High Plains, though guidance
varies regarding the magnitude of MUCAPE in this region. High-based
storms may develop into parts of the southern High Plains, with a
threat of isolated strong to severe gusts. 

...Parts of the Northeast/New England...
Guidance varies substantially regarding the strength/timing of the
shortwave trough and related flow fields that will move across New
England Sunday morning. Depending on the strength of the system and
the evolution of convection on D2/Saturday, there is some potential
for isolated strong to severe storms Sunday across the region, given
the presence of increasing buoyancy and favorable deep-layer shear.
A slower system could result in a more robust diurnal threat, while
a faster system may confine the primary threat to the morning.

..Dean.. 06/20/2025

$$


File: /home/ldm/var/data/BY_SOURCE/KWNS/ACUS03/20250620T0731.txt