753
FXUS63 KBIS 070316
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
1016 PM CDT Sun Sep 6 2026

.KEY MESSAGES...

- Moderate to high chances for showers and thunderstorms will
  remain tonight through Labor Day. Isolated to scattered severe
  thunderstorms are possible.

- Unseasonably warm and humid through the Labor Day, then
  trending cooler.

- Windy on Tuesday, with near-critical to critical fire weather
  conditions across southwest and south central North Dakota.

&&

.UPDATE...
Issued at 1009 PM CDT Sun Sep 6 2026

Water vapor energy shows a wave moving across northwestern North
Dakota. This wave is causing showers and thunderstorms across
the northwest into the north central. Heavy rain and lots of
lightning are possible with these storms. There is a chance that
one of these cells could become slightly stronger leading to
large hail and strong winds but the chances remain low at this
time. The current forecast remains on track.

UPDATE
Issued at 716 PM CDT Sun Sep 6 2026

A large supercell continues in McKenzie County and is likely
producing hail larger than golf balls at times, otherwise most
thunderstorm activity has ended over the forecast area for the
meantime. 0Z sounding at KBIS shows a stout cap after convection
from earlier today, which along with the SPC mesoanalysis page
indicates further initiation unlikely in the south central this
evening. Thunderstorm development remains possible in the
southwest this evening, though increasing CIN appears to be
winning out. Despite this, increasing LLJ, WAA, and a strong
shortwave will likely bring another round of showers and
thunderstorms initially tonight and through much of the day
Monday.

&&

.DISCUSSION...
Issued at 332 PM CDT Sun Sep 6 2026

A general unsettled pattern to bring isolated to scattered
thunderstorms, possibly severe, through tonight. High amounts of
instability, mostly elevated, will continue through tonight.
Meanwhile a weak pseudo warm front near a developing low will
be draped across much of the state through tonight. Aloft sees
falling heights as the upper level ridge moves east and
southwest flow takes its place. Models also indicate a low level
jet may return this evening through tonight. All this combined
will return widespread chances for showers and thunderstorms
through tonight. Today`s storms have left plenty of remnant
boundaries across the state, How these interact with each other
could influence severe weather tonight as well. Overall the
stronger severe weather will be located to anywhere with higher
shear which currently analyzed in the north and west. Elsewhere
has less shear, although high amounts of instability may be just
enough for stronger pulse like storms. Overall a hail threat up
to golf ball size will be possible with any stronger storm
through tonight, with rotating storms in the higher sheared
areas having the better potential for the bigger hail. The wind
threat is modest through tonight. DCAPE is high, although 0 to 3
km shear is lacking as are low level lapse rates. Thus winds 60
to perhaps 70 mph are possible. There still remains a low
tornado threat through tonight. This is highly dependent on
boundary interactions, although there is some increased SRH and
0 to 1 KM shear through tonight. Of note are some increased non
supercell parameters through this evening. Overall confidence in
surface based storms through tonight is low, yet a tornado is
possible along any boundary interactions. High pwats over 1.5
inches will continue to bring a heavy rain and localized
flooding threat. If confidence in any one area for heavy rain
increase then perhaps a flood watch may be needed tonight and
perhaps again on Monday. Otherwise look for mild lows in the 60s
tonight. Patchy fog may also return tonight to areas without
thunderstorms and some clearing. Confidence was not high enough
to include fog at this time.

Surface low then moves across the state on Labor Day bringing
more isolated to scattered severe thunderstorms. Timing wise,
severe storms could be ongoing in the morning as a low level jet
continues ahead of the low in the morning. As the low pushes
through following by a cold front, thunderstorms could continue
through the day from west to east through the day. A few
thunderstorms could then develop along a trailing front tomorrow
evening, although this may be more uncertain depending how much
the daytime convection impacts the atmosphere. All hazards
remain possible. Increased shear and instability will support
large hail to golf ball sized. Meanwhile, the potential for line
development could bring strong winds to 70 mph. There also
remains a conditional tornado threat for Monday as dewpoints
remain high and a weak warm front lifts ahead of the low.
Storms would have to be surface based to increase the tornado
threat. Currently SPC has a Marginal Risk for severe weather.
CSU-MLP severe outlooks shown all threats possible for Monday.
Thus anyone with outdoor plans for Monday should continue to be
weather aware on Monday. Highs for Labor Day will continue to be
warm with 80s for most of the area, and 70s north. Breezy
southerly winds will be found until a breezy westerly wind moves
in behind the low. Precipitation diminishes Monday night, with
lows cooling in the 50s to near 60.

The main concern for Tuesday remains strong winds. Both the NBM
and ECMWF EFI support advisory criteria winds of sustained
speeds between 30 and 40 mph and gusts of 45 to 55 mph. Tuesday
will be much cooler with highs from the upper 60s northwest to
lower 80s southeast, but also drier with minimum humidity
falling to around 25 to 35 percent. The combination of strong
winds and lower RH will likely bring near- critical to critical fire
weather conditions to all of southwest and some south central
North Dakota, with critical conditions especially possible in
the far southwest where RH could fall closer to 20 to 25
percent. A few showers may also be found Tuesday, mainly in the
north. Cooler temperatures remain in the forecast on Wednesday,
but with winds not nearly as strong yet still breezy at times.
Ensembles have now trended toward a quick warmup on Thursday due
to a transient ridge, followed by a distinct cooling trend
heading into next weekend, but with increasing spread due to
synoptic scale wave phasing uncertainty. There could be an
increased fire weather threat on Thursday, especially in the
southwest. Limited chances for precipitation also look to be
Wednesday through Friday.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 716 PM CDT Sun Sep 6 2026

Scattered showers and thunderstorms are expected at times
through the period and all terminals may be impacted. A few
storms may be severe with large hail, torrential rain, and
erratic winds. Coverage through the remainder of this evening
will likely be limited. However, the next wave may develop in
western and possibly north central North Dakota overnight before
moving east across the state on Monday. In addition, MVFR/IFR
ceilings are expected along, north, and east of the Missouri
River Monday morning.

&&

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

&&

$$

UPDATE...Johnson/Telken
DISCUSSION...Anglin
AVIATION...Telken