667
FXUS63 KBIS 071436
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
936 AM CDT Mon Sep 7 2026

.KEY MESSAGES...

- Numerous showers and thunderstorms expected throughout the
  day today. A few storms could be severe.

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

- Unseasonably warm and humid today, then cooler Tuesday and
  Wednesday. A brief warm up on Thursday could be followed by
  much cooler temperatures next weekend.

&&

.UPDATE...
Issued at 936 AM CDT Mon Sep 7 2026

A line of thunderstorms has developed from southern Renville
through Eastern Ward counties this morning. While the line went
directly through Minot, observed winds remained light, and no
other observations support gusty winds as of now. This line is
rapidly moving northeast into what should be a less unstable
environment. As such, severe weather associated with this
particular line remains unlikely. However, frequent lightning
and brief torrential rain are occurring. Otherwise, anything
else within the CWA remains showers at this time. With the far
southwest starting to clear and the back edge of the stratus
deck approaching the rest of western ND, will continue to
monitor for additional development through the day.

UPDATE
Issued at 729 AM CDT Mon Sep 7 2026

Forecast adjustments for this update were mainly to PoPs and
driven by observed and rapid refresh model trends. While
showers are increasing in areal coverage across western North
Dakota, coverage of thunderstorms has been much lower than
anticipated. Recent runs of the HRRR have downplayed convective
coverage with the surge of synoptic scale forcing this morning,
which so far is playing out. MUCAPE and effective bulk shear do
remain supportive of strong to severe storms this morning.

&&

.DISCUSSION...
Issued at 530 AM CDT Mon Sep 7 2026

Upper level synoptic features early this morning include a deep
longwave trough over the western CONUS with an embedded double-
circulation closed low spinning through the Pacific Northwest
and a downstream ridge tilting positively from Texas to the
Upper Mississippi River Valley. At the surface, lee troughing
is analyzed from southern Saskatchewan through the Foothills of
Colorado. A nocturnal low level jet is supplying warm air
advection and moisture transport through the western Dakotas,
which is responsible for clusters of showers and thunderstorms
early this morning. A shortwave has ejected from the base of the
longwave trough into eastern Montana, and associated height
falls should contribute to an areal increase of showers storms
along the ND/MT border by mid morning. Model guidance is in good
agreement that 700-500 mb DCVA will drive a broad corridor of
showers and thunderstorms over a stable but very moist boundary
layer from western North Dakota around mid morning to eastern
North Dakota in the mid to late afternoon. This initial round
of convection is likely to remain elevated, but steep mid level
lapse rates and modest to high deep layer RH above the base of
the EML could yield up to 1000-2000 J/kg of CAPE. Effective bulk
shear is forecast to vary over space and time, but generally
remains in the 30-50 kt range, sufficient for severe storms.
CAMs favor a cluster or linear mode with the initial round on
account of the strong forcing and lack of underlying surface
boundary. But the stable boundary layer could mitigate the risk
for damaging winds to some extent.

This afternoon, the upper low closest to the base of the
longwave trough will pivot northeastward into western Montana
and form a separate mid level double-circulation low with the
lead shortwave. This process should begin driving the lee
surface trough eastward, with a rapidly occluding cyclone over
southeast Saskatchewan by this evening. How the initial round
of storms plays out this morning and early afternoon lowers
confidence in the mesoscale environment in the western half of
North Dakota later this afternoon. But if strong diurnal heating
occurs, a corridor of up to 2000 J/kg of SBCAPE with little to
no CIN could develop along and just ahead of the surface trough.
Strong low level convergence along the trough could be
coincident with a corridor of 850 mb warm air advection. This,
with continued height falls in a southwest flow regime, could
provide enough forcing for convective initiation in the western
half of the state later this afternoon. This second round of
convection is more likely to be discrete with only isolated to
widely scattered coverage at most. But these storms would carry
a much higher threat ceiling, including a tornado risk
supported by strong low level shear and low LCLs. Model
hodographs show strong streamwise vorticity in the 0-l km layer
and would support splitting supercells. There is still a chance
though that all these ingredients will not become properly
aligned. Therefore, have not made any deviations from our
forecast hazards at golf ball size hail, 70 mph wind, and a
conditional risk for a tornado.

Any thunderstorm throughout the day could be a very prolific
rain producer with anomalously high precipitable water around
1.5-1.75". Extrapolation of early morning convection paired with
rapid refresh guidance suggests the highest probability for
training convection is across northwest and north central North
Dakota from around sunrise to midday.

One final day of unseasonably humid conditions today, with the
southwest becoming drier in the afternoon as the lee trough
pushes in. Forecast highs range from the mid 70s northeast to
upper 80s southwest. The surface trough will transition to more
of a traditional cold or occluded front this evening, and
trailing strong low to mid level dry slotting should put an end
to any isolated storms that persist beyond early evening. There
is some concern that the deepening cyclone over southern
Saskatchewan could bring a corridor of very strong winds into
northwest North Dakota late this evening through tonight, but
model soundings show just enough of a surface inversion to
prevent maximum potential momentum transfer of up to 50 kts.
The strong cyclone will spin into southwest Manitoba on Tuesday,
bringing cooler temperatures and strong westerly winds across
the state. Confidence remains high in sustained winds around 30
to 35 mph with gusts to around 50 mph. Barring any last-minute
forecast deviations, a Wind Advisory will likely be needed for
most, if not all parts of our forecast area. Forecast highs on
Tuesday are limited to around 65 to 70 in the north, but would
not be surprised to see even cooler daytime temperatures in the
northwest as a shortwave trailing the occluded low returns
chances for light rain. In southern North Dakota, highs are
still forecast to reach the upper 70s on Tuesday, bringing
minimum RH values into the 25 to 35 percent range. Near-
critical fire weather conditions are expected, and in far
southwest North Dakota, a longer duration of RH lower than 30
percent could push fire weather conditions above critical
thresholds.

High temperatures remain in the upper 60s to upper 70s on
Wednesday along with breezy conditions, but not nearly as
strong winds as on Tuesday. A transient ridge preceding a
potent southern Canadian shortwave is forecast to cross the
region late Wednesday into Thursday, and ensemble guidance is
confident that the timing of the thermal ridge will bring high
temperatures back into the 80s for most areas. Very low RH in
the 10 to 20 percent range along and to the south and west of
the Missouri River combined with west-southwest winds around 15
to 20 mph could lead to another day of near-critical fire
weather conditions. Ensembles then favor a strong cooling trend
heading into the weekend that could bring temperatures well
below normal.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 729 AM CDT Mon Sep 7 2026

Periods of showers and thunderstorms are expected across the
state throughout the day. Heavier showers and storms could
produce torrential rain reducing visibility to IFR levels. A
few storms could be severe with large hail and strong, erratic
wind gusts.

MVFR/IFR ceilings have developed across central North Dakota.
The low ceilings are forecast to retreat northward later this
morning into the afternoon. Ceilings are otherwise expected to
remain at VFR levels, aside from within showers and storms.

Winds will primarily be easterly to southeasterly around 10-20
kts this morning, although some stronger gusts are possible. A
cold front entering the state this afternoon will shift winds
to the west. Winds could remain gusty in the northwest through
tonight.

&&

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

&&

$$

UPDATE...Telken
DISCUSSION...Hollan
AVIATION...Hollan