542
FXUS63 KBIS 052342
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
642 PM CDT Sat Sep 5 2026

.KEY MESSAGES...

- Periods of isolated to scattered showers and thunderstorms
  are expected through the holiday weekend. A few storms may be
  strong to severe. The highest chances for showers and storms
  are from Sunday night into Labor Day.

- Unseasonably warm and humid through the holiday weekend, then
  trending cooler.

- Windy on Tuesday, with near-critical fire weather conditions
  in southwest North Dakota.

&&

.UPDATE...
Issued at 614 PM CDT Sat Sep 5 2026

A line of thunderstorms continue to move across north central
South Dakota and continues to spill into south central North
Dakota. This line has produced ping pong size hail at times in
South Dakota. The North Dakota portion of the line produced
outflow weakening the storms behind the outflow. Also the anvil
cirrus continues to increase CIN upstream of the storms. There
is another lone cell moving across the International Border
that is sub severe at the moment. There is widespread
instability, but weak shear across the state which has lead to
these strong multicellular storms pulsing up quickly then
falling apart cause there is not enough shear to keep storm
organized. The CAMs do not really have much development this
evening into tonight as these storms weaken.

&&

.DISCUSSION...
Issued at 220 PM CDT Sat Sep 5 2026


Currently the western half of the CONUS is under southwest flow
thanks to a large area of low pressure/heights in the Pacific
Northwest. The ridge axis is roughly north/south over western
Minnesota. At the surface a weak low pressure sits in
southwestern North Dakota with a warm front across the South
Dakota border. Lingering storms from a low level jet (LLJ) this
morning still continue in far north central ND. These storms
produced heavy rain with very little storm motion, so several
Flood Advisories were issued. The latest one will expire at
1930z. There are some bubbling cumulus clouds, elevated, in the
south central that have some light radar returns with them.
According to our 18z sounding, there is a heavy capping layer,
then plenty of elevated CAPE.

The rest of today should be mostly quiet storm-wise as the
surface low pressure slides to the east, and there are currently
no shortwave in the southwest flow. Most CAMs have no storms in
the area until the LLJ kicks back in after 04z. There is still
a level 1 risk for the eastern 2/3rds of the state for today,
although the next round may not be until after sunset again or
until Sunday. Today will also be very warm with highs in the
mid 90s, that is roughly 20 degrees above normal. These hot
temperatures will continue through Monday, although Monday will
be in the 80s.

The severe thunderstorm risk will continue all holiday weekend
with a level 1 risk through Monday as the southwest flow and
warm temperatures continue. Sunday the surface low looks to be
in northeastern South Dakota with an area of 2000-4000 J/kg of
MUCAPE over North Dakota wrapping around the low. The shear will
be marginal with around 15kts in the east and 35kts in the
west. Most CAMs do not have much going on until after sunset
again when a possible LLJ and kick storms off using that
elevated MUCAPE. The area of concerned would be around Highway 2
between 6pm and midnight. Sunday night a strong area of
diffluence will also be over the state starting around 1am, so
there will likely be overnight storms.

Labor Day a Northern Rockies low pressure will swing up to the
Northern Plains into eastern Montana. With this, possibly a
widespread rain event could occur through the first half of the
day before North Dakota gets into the dry slot of the low.
Models have a much smaller area of severe weather, with a skinny
area of MUCAPE around 2000 J/kg in western ND. Shear will be
plenty however 40-55kts. A limitation for storms is a strong
warm layer at 850mb that will be a capping layer. CAMs otherwise
have a line of storms coming out of Montana in the morning off
the front.

The rest of the forecast will be a slow cooling trend with
cooler air wrapping into the northern Plains. As of now forecast
temperatures will reach the 60s and 70s by next Saturday. Next
week will also be breezy to windy, especially Tuesday and
Wednesday where an Advisory or High Wind Warning may be needed.

&&

.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 614 PM CDT Sat Sep 5 2026

VFR conditions will continue across the region. There are
thunderstorms near KBIS, but they continue to diminish. Winds
will remain out of the east to southeast through the night.
There are some models bringing in thunderstorms tomorrow morning
to the KJMS area and the KXWA area later in the morning.

&&

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

&&

$$

UPDATE...Johnson
DISCUSSION...Smith
AVIATION...Johnson