779
FXUS63 KBIS 060223
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
923 PM CDT Sat Jul 5 2025

.KEY MESSAGES...

- Showers and an isolated thunderstorm are possible tonight through
  early Sunday morning, mainly over western North Dakota.

- Cooler temperatures are forecast Sunday, with another chance
  (40 to 60 percent) for showers and thunderstorms on Sunday.

- Temperatures will trend warmer again through the middle of
  next week, along with daily chances for showers and storms.

&&

.UPDATE...
Issued at 922 PM CDT Sat Jul 5 2025

As the most recent CAMs and instability forecasts have
indicated, the line of strong to severe storms fell apart prior
to reaching North Dakota. Now there is hardly any lightning
activity whatsoever, with mostly light rain moving across the
southwest. The northwest may also see some rain moving in over
the next few hours. Severe storm development is not expected,
though there may be an isolated stronger wind gust associated
with the storms continuing to fall apart, though those should
generally be very brief.

UPDATE
Issued at 629 PM CDT Sat Jul 5 2025

Strong to severe storms are ongoing across southeastern Montana.
At the moment, forecast instability appears to drop off a cliff
as it approaches the North Dakota border, so the current
expectation is that these storms will quickly die on approach to
Bowman and Slope counties. The majority of the stronger activity
is expected to track into South Dakota instead, though the
remnants of the line may bring some isolated stronger wind gusts
as it moves into the state. Otherwise, no major changes needed
to the forecast.

&&

.DISCUSSION...
Issued at 237 PM CDT Sat Jul 5 2025

As of early this afternoon, a weak shortwave was moving through
the mean ridge aloft. This wave has led to a narrow line of
diminishing showers across the west with an occasional rumble of
thunder south. This activity will continue to diminish over the
next couple of hours, giving way to a mostly sunny sky through
the rest of the afternoon. Highs will be cooler than the past
couple of days, ranging from the mid 70s northwest, to the lower
80s south central and southeast.

Attention then turns to tonight as chances for thunderstorms
increase in the evening across the west, especially the
southwest. Storms will develop this afternoon across the higher
terrain over western and central Montana and then track towards
the western North Dakota border. Most of the CAMs suggest an
organized line of convection (or multiple lines) approaching the
state border in the 00z to 03z Sunday time frame, weakening
fairly quickly as the move into North Dakota. Forecast RAP
soundings do suggest much weaker instability on the North Dakota
side with MUCAPE mainly ranging from 300 to 800 J/kg. That
being said, deep layer shear will be strong in the 45 to 55 knot
range so a few strong to severe storms cannot be ruled out,
especially across the southwest where instability will be
maximized. It is important to note that the threat has shifted
significantly south and west so there is some possibility that
North Dakota will end up seeing little to no severe weather.
However, given the impressive shear profile, we will continue to
advertise the potential for ping pong ball size hail and
damaging winds to 70 mph as a worst case scenario.

Several other little waves will continue moving through the
nearly zonal flow aloft through the day on Sunday, keeping
chances of showers and storms (40 to 60 percent) in the
forecast, mainly early in the day. Once again, shear will be
descent (but not as strong as tonight), but instability will be
limited. Thus a stronger storm or two cannot be ruled out but
severe weather is not anticipated. Sunday will also be cooler,
with highs in the upper 60s to upper 70s.

The next wave moves in on Monday as active zonal flow continues.
We will see low to medium chances (20 to 40 percent) for
showers and storms across much of the west and central with the
best chances in the vicinity of the Devils Lake Basin and James
River Valley. By the afternoon hours here, some guidance has
MLCAPE reaching into the 1000 to 2000 J/kg range with deep layer
shear in 45 to 55 knot range. That being said, confidence in
stronger instability is rather low given the potential for some
ongoing convection, cloud cover, and less than favorable wave
timing. A few storms could be strong to severe around the James
River Valley if everything falls into place, but the threat
appears fairly conditional at the moment.


A more substantial ridge starts to build in Monday night through
mid-week, promoting another big warmup. Highs on Monday will
range from the mid 70s to the lower 80s and then by Wednesday we
will see widespread highs back in the 90s. Another cooldown is
then possible by the end of the workweek, but large ensemble
spread suggests some pattern uncertainty still. Some more weak
waves are forecast to move through the region as the ridge axis
pushes east, only leading to low chances (20 to 30 percent) for
showers and storms here and there Tuesday night through Friday.
CSU Machine Learning severe weather guidance is starting to pick
up on some low chances for severe storms in the
Wednesday/Thursday time frame but we still have quite a ways to
go with plenty of time for things to change.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 629 PM CDT Sat Jul 5 2025

VFR conditions are present across all terminals, and for the
most part should prevail through the TAF period. A line of
showers and possible some thunderstorms will move in from the
west, bringing low to medium chances for showers across all TAF
sites, with the exception being KJMS. Generally light and
variable winds are expected through the period. There is low
confidence in some lower ceilings across the west Sunday
morning, generally around the 2.5 to 3 kft range. Overcast mid-
level clouds will generally be associated with the showers and
storms as they move through.

&&

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

&&

$$

UPDATE...Besson
DISCUSSION...ZH
AVIATION...Besson