661
FXUS63 KBIS 071955
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
255 PM CDT Mon Jul 7 2025

.KEY MESSAGES...

- Isolated to scattered strong to severe thunderstorms (40 to 70
  percent chance) are possible this afternoon over south
  central and parts of eastern North Dakota.

- Temperatures trend warmer through the middle of this week,
  peaking on Wednesday when widespread 90s are expected for
  daytime highs.

- A chance for strong to severe thunderstorms increases across
  the region Wednesday and again Thursday and Thursday night,
  followed by cooler temperatures to end the work week.

&&

.DISCUSSION...
Issued at 255 PM CDT Mon Jul 7 2025

A mid to upper level shortwave is traversing the near zonal
flow found over the northern Plains this afternoon. An inverted
surface trough associated with this wave, along with a low level
jet draped across central North Dakota, has promoted the
development of scattered showers and thunderstorms earlier this
morning and afternoon. While conditions in south central North
Dakota into the James River Valley are marginally supportive of
strong to severe thunderstorms, with model MUCAPE values falling
into the 1000-2000 J/KG range and dewpoints peaking into the
lower to mid 60s, these earlier storms have somewhat worked
over the environment. Also to consider is that somewhat poorly
sheared environment, with 0-6KM bulk shear values only peaking
into the 25 to 35 knots range. Overall, the potential for
strong to severe storms this afternoon has decreased. That
being said, there still remains the possibility for a severe
storm to develop in the James River Valley, especially in the
northern section which has remained out of the showers and
convection earlier in the day. Large hail up to the size of
ping pong balls and wind gusts up to 60 MPH are possible with
any severe storm that does end up developing. The most recent
SPC update has pulled the marginal much further east than
before, mostly to the west of Highway 3, though the Slight
(level 2 of 5) risk remains draped across the southern James
River Valley. Better shear is progged to develop later this
evening, but the inverted surface trough quickly exiting to the
east of the forecast area, and thus chances for shower and
storms in the James River Valley diminish rapidly by the late
afternoon. With high pressure building in from southeast
Saskatchewan today, skies are anticipated to clear from west to
east through this afternoon and overnight into Tuesday. High
temperatures this afternoon are broadly forecast in the lower
70s north, up to the lower 80s south.

With flow over the forecast area turning northwesterly ahead of
an incoming, transient upper level ridge, quiet conditions are
anticipated on Tuesday. Generally dry weather is expected
though a minor shortwave cutting across the far southwest
overnight, along with the redevelopment of a LLJ, could allow
for isolated showers and a few rumbles of thunder (10 to 15
percent chance). Otherwise, some partially to mostly cloud skies
are expected to build back in from the northeast on the
backside of the closing off mid level trough Tuesday morning,
though cleaning skies are anticipated through the PM Tuesday.
High temperatures Tuesday afternoon are forecast from the mid
70s in the Turtle Mountains, up to the upper 80s in the
southwest, though a few locations tickling the lower 90s is not
out of the question.

With the upper level ridge moving overhead Tuesday night into
Wednesday, warming temperatures and dry conditions are expected
to continue. With the thermal axis penetrating into western
North Dakota, and with generally clear to partly cloudy skies
through the afternoon, Wednesday is currently anticipated to be
the warmest day of the week with highs broadly in the 90s.
Highs peaking into the 100s is very achievable Wednesday
afternoon, especially across the west and north central, though
low humidity currently keeps apparent temperatures below 100 at
this time. Then, similar to Tuesday, the redevelopment of a LLJ
in the PM Wednesday will allow for the development of showers
and thunderstorms (20 to 40 percent chance), though somewhat
more widespread over central North Dakota. In fact, a moderate
to strongly unstable environment is expected late Wednesday
afternoon and evening, with model MUCAPE values as high as 3000
to 4000 J/KG at the time of this forecast update, could allow
for the development of a few severe storms. However, the lack
of a strong forcing mechanism or sufficient shear (0-6KM bulk
shear values modeled up to around 25 knots at most), indicates
that such storms would be more isolated in scope. As such, SPC
has placed much of western and central North Dakota under a
Marginal (level 1 of 5) risk for isolated severe thunderstorms
on Wednesday. Regarding hazards, the imbalance between explosive
CAPE and lackluster shear will probably help keep the hail
threat to around half dollars in size, while gusts up to 60 MPH
are also possible.

Now on to Thursday. Similar to the day before, an explosively
unstable environment with MUCAPE values well above 3000+ J/KG
cape is modeled over central North Dakota. Dewpoint values
Wednesday afternoon are also expected to peak into the upper 60s
to 70s by the late afternoon, early evening period. This time
around, however, the passage of a cold front across the northern
Plains Thursday afternoon and evening, associated with an
positively tilted upper level trough crossing across the
southern Canadian Prairies, will provide more than enough
forcing for CI. The only question that remains at this time is
the quality of the sheared environment. Current model trends
keeps bulk shear values relatively low - sub 30 knots - through
much of the afternoon and evening, though shear then increases
on the backside of the cold front. Without better understanding
how the sheared environment aligns with the other convective
environment, the evolution and scope of potential storms on
Thursday remains hazy at this time. Both the CSU machine
learning algorithm and SPC continue to highlight central North
Dakota for Thursday afternoon and evening. Otherwise, high
temperatures on Thursday are in the 80s and lower 90s.

The passage of the closing off trough over the northern Plains
Friday will again promote showers and thunderstorms through the
day. Cooler temperatures, with highs broadly in the 70s, are
also anticipated on the backside of the cold front the day
before. The ensemble becomes increasingly discordant behind this
upper level low, though a general trend back toward
northwesterly flow aloft is captured through the weekend and
into next week. With such a pattern, near daily low chances for
showers and possible some thunderstorms are possible, though
exactly when and where is nebulous at this time. A general trend
back into warm weather, with highs in the 80s and 90s, is
expected through the weekend and into next week.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 255 PM CDT Mon Jul 7 2025

VFR ceilings and visibility are mainly expected at all TAF sites
throughout the 18Z TAF period. Pockets of low stratus linger
over north central North Dakota at the time of this update, and
may occasional coalesce into MVFR ceilings over KMOT through the
early afternoon. Scattered showers and thunderstorms are moving
eastward over south central North Dakota, with more development
possible across the James River Valley later this afternoon. The
confidence in the location of this development is too low to
include mentions of storms at any given TAF site at this time,
though have included a PROB30 -SHRA at KJMS with this update. Some
storms may become strong to severe, with large hail and gusty
winds possible with whatever severe storms that do develop.
Otherwise, patchy fog may be possible across the James River
Valley tomorrow morning. This fog may be restricted to shallow
areas, and thus confidence remains too low to include visibility
reductions at any given TAF site at this time. Northwesterly
winds this afternoon are expected to remain somewhat gusty, with
speeds up to 15 knots and gusts up to 25 knots, through the
late afternoon, before diminishing overnight and turning
anticyclonically around high pressure moving in across the
forecast area through the end of the TAF period.

&&

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

&&

$$

DISCUSSION...Adam
AVIATION...Adam