653
FXUS63 KBIS 080555
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
1255 AM CDT Mon Jun 8 2026

.KEY MESSAGES...

- Scattered to numerous severe thunderstorms over much of
  western and central North Dakota late this afternoon and
  tonight.

- There is a Marginal Risk (threat level 1 of 5) of severe
  thunderstorms over portions of western North Dakota Monday
  night.

- Another round of scattered to numerous severe thunderstorms is
  possible on Tuesday.

- Above normal temperatures through Tuesday, then trending
  cooler for the remainder of the week.

&&

UPDATE
Issued at 826 PM CDT Sun Jun 7 2026

** Mesoscale Discussion **

The peak intensity of this severe thunderstorm even is beginning
and is expected to be maximized through about 10 pm CDT/9 pm
MDT. A severe-storm risk will linger thereafter, but the peak
of the event is expected in the next two hours.

As of 01z, multiple linear convective segments are evolving in
western ND, with one prominent and developing bowing segment in
southwest ND from near Belfield to Mott, Hettinger, and south to
near Bison, SD. The environment downstream of this developing
bow echo is characterized by moderate to strong bouyancy and
sufficient low- and midlevel wind shear to support damaging to
destructive winds downstream in southwest and parts of south
central ND. WoFS guidance continues to support this corridor as
having the highest probability of damaging winds, particularly
in parts of Dunn, Stark, Hettinger, Adams, western Sioux, Grant,
western Morton, Oliver, and Mercer Counties through 10 pm CDT.

The storms in northwestern ND, extending southward into the west
end of Lake Sakakawea, have begun to take on a more organized
and linear appearance in the last 30 minutes as well. These
storms are also in a sufficient CAPE-shear setting to support
both large hail and damaging winds.

The 00z Bismarck sounding displayed steep lapse rates and large
MLCAPE, but week deep-layer shear, as long-forecast by guidance.
While middle and upper-level winds are forecast to increase in
time, the developing QLCS is apt to outpace the stronger flow
aloft by late evening. Once that occurs and the QLCS moves into
weaker low- and deep-layer shear, roughly along and east of the
Highway 83 corridor, it may become outflow dominant and the
magnitude of damaging winds is apt to gradually decrease. WoFS
guidance supports this evolution as well, with peak gusts mainly
in the 55 to 65 mph range once the storms pass roughly east of
the Highway 83 corridor.

CJS

UPDATE
Issued at 616 PM CDT Sun Jun 7 2026

** Mesoscale Discussion **

The severe storm risk is rapidly increasing in western North
Dakota, including initially the potential for large to very
large hail of 1.5 to 2.5 inches in diameter. The potential for
damaging to destructive straight-line winds will also increase
the next few hours, with the previously-advertised corridor of
peak gusts of 85 to 100 mph still in the forecast.

As of 23z, supercells have formed along the surface front and
wind shift in western ND, notably in southern McKenzie and
Golden Valley Counties. These supercells have formed in an
environment characterized by strong bouyancy with MLCAPE on the
order of 3000 J/kg and effective-layer shear around 50 kt, which
is favorable for large to very large hail. Hodographs do display
a relatively straight geometry in this area, suggesting cells
may continue to undergo splitting and merging in this area.
Right-moving supercells are slightly favored over left-moving
supercells in this region given modest low-level curvature in
the hodographs. Eventually, if sufficient mergers and clustering
occurs, the dominant hazard with these initial supercells may
also become more damaging-wind-related. Recent WoFS cycles do
suggest these supercells may indeed merge and begin propagating
downstream toward the west end of Lake Sakakawea in the next few
hours, favoring that increase in damaging winds.

Low-level convergence along the wind shift further north in
western Mountrail and Burke Counties and vicinity appears to be
weaker, and visible satellite imagery suggests fewer attempts at
deep convective initiation in that part of northwestern North
Dakota at this time. Nonetheless, a low to medium probability of
a supercell or two forming in northwest ND continues.

Upstream supercells in southeastern Montana are in a favorable
CAPE-shear setting for continued maintenance, and their motion
is expected to continue taking them near the frontal zone and
into southwestern North Dakota in the next few hours. We expect
that once significant upscale growth begins, and a potential bow
echo takes shape from these storms, that they will begin to take
a more north-northeast forward motion (following forecast Corfidi
vectors) rather than the east-northeast motion that the right-
moving supercell motion vectors have favored thus far. As a
result, even the supercell in far southeast Carter County, MT,
and northwestern Butte County, SD, may become part of a larger
bowing complex that moves into southwest and south central ND.
WoFS runs continue to signal potential for high-end wind gusts
with these expected bowing structures in the coming hours.

CJS

UPDATE
Issued at 409 PM CDT Sun Jun 7 2026

Quick update for issuance of Severe Thunderstorm Watch number
285 for western and much of central North Dakota. The Storm
Prediction Center has opted for a PDS (Particularly Dangerous
Situation) Severe watch due to the likelihood of damaging winds
this evening.

&&

.DISCUSSION...
Issued at 325 PM CDT Sun Jun 7 2026

Currently, southwest flow aloft ahead of a dynamic upper level
trough advancing east into the Rockies. Quasi-stationary/slowly
east moving surface trough/frontal boundary stretches from far
western South Dakota north-northeast across far western North
Dakota this afternoon. Very warm and humid weather across
western and central ND, with current afternoon temperatures
well into the 80s to lower 90s, along with sfc dewpoint
temperatures in the 60s to near 70. This results in mixed layer
CAPE of 2-3K J/KG west into north central. Effective/bulk shear
remains mainly along to west of the sfc boundary, 35-50kts far
west. Elevated echos over central ND at the moment, and not
expecting anything from this with a stout low level capping
inversion here.

Some storms may initiate between 20-22Z across the western
Dakotas looking at the latest CAMs/WoFS runs, with some models
closer to 23Z. Have not seen anything out of the Black Hills
yet, but there have been a few towers and orphan anvils there
the past hour. Nothing within the CU field over western ND, but
latest mesoanalysis indicates CIN eroding. Anything developing
across western ND would be discrete and would pose a threat for
very large hail considering the lapse rates we`ve sampled via
the BIS 18Z sounding. Will be monitoring this area closely. A
bigger threat for severe winds will materialize as convection
developing over the higher terrain of the Big Horns and
southeastern Montana push northeast and congeals into a linear
line/bow echo. Last several WoFS runs are indicating a damaging
wind swath from southwest North Dakota northeast into north
central areas of North Dakota, including Beach and Bowman,
northeast through Dickinson, Killdeer, Hazen, Garrison, and
possibly Minot. Winds of 85-100 mph will be possible in this
swath. Latest SPC Day 1 did upgrade this area to a Moderate
Risk (level 4 of 5) with elevated likelihood of occurrence,
with much of the remaining area outside of the James Valley
still in the Enhanced Risk (level 3 of 5) area.

Storms will end west to east tonight behind the FROPA, with
winds becoming more west/northwest and clouds diminishing.
Cooler and less humid for Monday behind the front.

WAA and southwest flow aloft increases Monday night into
Tuesday, as a subtle mid level S/WV ridge moves across the area
ahead of another mid level trough. Marginal (threat level 1 of
5) Risk for severe storms over western North Dakota Monday
night as lead energy ejects out of the trough and low level
moisture increases again, followed by another Slight/Enhanced
Risk (2/3 of 5) for much of the area on Tuesday as the
aforementioned trough pushes into the Northern Plains and drives
another frontal boundary east across the region.

Afterwards, we will remain in an active pattern with the general
flow dominated by upper level lows or troughing. This will
maintain daily chances for showers and thunderstorms, along with
temperatures trending cooler and closer to early/mid June highs
and lows (highs mid 60s to mid 70s...lows 45-55).

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 1250 AM CDT Mon Jun 8 2026

Convection has exited all but KJMS...have activity arriving
there 07-08Z with some variable and gusty winds up to around
35-40kt. Showers will persist for a couple hours behind the
convection, mainly at KBIS and KJMS. All precip should be out of
the area by dawn, leaving the rest of the forecast period dry.

Sites should be MOSTLY VFR, though there is a few hour window
for mainly MVFR stratus at KMOT, KBIS, and KJMS this morning.
Should be all VFR by midday through this evening.

Winds are a bit strong behind the departing convection out of
the W-NW...esp. for KDIK, KXWA, and KMOT, with gusts of 25-35kt
possible. Winds will gradually decrease through the morning, but
still remain breezy (G15-25kt) rest of the daytime hours. Winds
should light and variable late in the forecast period.

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

UPDATE...CJS
DISCUSSION...NH
AVIATION...Thies NWS Hastings