360
FXUS63 KBIS 081155
AFDBIS

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

.KEY MESSAGES...

- Dry and cooler today with highs in the mid 70s to mid 80s.

- Slight chance of a thunderstorm northwest late tonight.

- Another round of scattered to numerous severe thunderstorms
  Tuesday.

- Near normal temperatures today, above normal temperatures
  Tuesday, then cooler for the remainder of the week.

&&

.UPDATE...
Issued at 621 AM CDT Mon Jun 8 2026

Thunderstorms have ended over the area this morning. There
could be a stray shower or two glancing the southern James River
Valley through mid morning. For the most part though, dry today
with a lot less wind. Highs are expected to range from the mid
70s to mid 80s. Only a few minor tweaks to sky cover and pops
for the early morning update.

&&

.DISCUSSION...
Issued at 144 AM CDT Mon Jun 8 2026

Ongoing convection is tracking through the James River Valley
early this morning. Once convection exits eastern portions of
central ND, we expect a quiet day today. As cirrus exits to the
east, we should see a good amount of sun, although some low
clouds and patchy fog may be lingering around this morning.

Surface high pressure and drier air builds over the area today
from the west. Surface high pressure is forecast to be situated
over the western Dakotas by around midday, and propagating east
from the eastern Dakotas into Minnesota this evening. In
addition to the cooler and drier air, winds will be much lighter
across the forecast area today.

After a quiet day today we now shift our focus to Tuesday.
Another upper level low will track from just off the Pacific
Northwest Coast this morning, into the Northern Rockies by
Tuesday afternoon. An initial wave tracking through the base of
the upper level trough, combined with a modest low level jet,
may produce some late night convection over eastern Montana,
some of which could clip the northwest portion of the state just
before sunrise Tuesday. Confidence in the placement of this
convection late Monday night is low, but a stronger storm with
a marginally severe hail threat can not be ruled out in
northwest ND.

During the day on Tuesday cyclogenesis commences in the lee of
the Northern Rockies with a surface low developing in the Mondak
region around midday Tuesday, and propagating into western ND
Tuesday afternoon. Abundant warm moist air will be pulled back
into the forecast area Tuesday with steepening lapse rates and
increasing MLCAPE to 2500-3500 J/kg by afternoon. This will set
the stage for another round of scattered to numerous severe
thunderstorms from mid-late afternoon through Tuesday evening.
Generally speaking the upcoming event is similar to Sunday`s
round of severe storms (a very unstable but initially capped
atmosphere being impinged upon by an upper level system with a
north-south surface boundary). There are some differences
though. The storm mode looks to eventually become linear.
However, Tuesday`s setup look to be more favorable for
supercell development early on with a significant cross
component of 30-40 kts of bulk shear to the surface front.
Initially high based supercells over western ND will track into
a more moisture rich environment in central ND. In addition
forecast soundings indicate a more highly sheared lower level
environment than Sunday. The areal extent of high STP values,
strong 0-1km helicity and low LCL values is impressive, covering
much of northwest and central ND in the mid-late afternoon and
lingering over central ND through the evening. If we see
afternoon/early evening supercells, large to very large hail
would be possible, along with a possible tornado, with the
tornado threat increasing in the evening as storms move into
a more favorable environment. Uncertainty exists in the
predominant storm mode as the low level shear profile increases
Tuesday evening. If a more linear mode develops there will be
more of a wind threat, although any rotating updrafts within the
linear system would support tornadoes. If there is a window of
discrete supercells, before the system probably does become
linear, the threat for supercell tornadoes will be higher, with
a possible strong tornado not out of the question. We will ramp
up our messaging this morning, increasing the magnitude of all
hazards Tuesday. Definitely a day to stay weather aware!

Once we make it through Tuesday, it looks like a cooler and
quieter period through the rest of the workweek. We will see
daily chances of showers and thunderstorms as we remain within
an cyclonic upper level flow.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 621 AM CDT Mon Jun 8 2026

For the most part, VFR conditions are expected across the
forecast area through the 12Z TAF period. The exception may be
the potential for a period of MVFR ceilings over the James River
Valley this morning (including KJMS). Then late in the period as
southerly winds increase there is the potential for some MVFR
ceilings lifting north into southern ND towards 12 UTC. At this
time have kept MVFR ceilings from reaching the southern TAF
sites through 12Z Tuesday, but will need to monitor. Otherwise
only mid and high clouds expected today and tonight. Variable
winds through the period, but much lighter than Sunday.
Generally a southwest to northwest flow today 10 to 15 knots,
with some gusts up to around 25 knots possible. Winds diminish
this evening and turn southeast, then increase after midnight,
especially west.

&&

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

&&

$$

UPDATE...TWH
DISCUSSION...TWH
AVIATION...TWH