222
FXUS63 KBIS 111155
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
655 AM CDT Mon Aug 11 2025

.KEY MESSAGES...

- Near-surface smoke is expected to clear from west to east this
  morning and afternoon.

- Isolated to scattered showers and thunderstorms are expected
  this afternoon and early evening. A few storms may become
  strong, with a severe storm possible in the James River
  Valley.

- Most days this week will see highs in the mid 70s to mid 80s,
  but it could be as warm as the lower 90s in the southwest on
  Wednesday and south central on Thursday.

- Strong to severe thunderstorms could return to parts of the
  region Wednesday through Thursday.

&&

.UPDATE...
Issued at 655 AM CDT Mon Aug 11 2025

Surface observations at 630 AM CDT show the cold front has entered
the northwest corner of the state and should pass through Williston
by the top of the hour. The smoke is finally being cleared out
behind the front, and this trend should continue through the day.
Gusty winds have also been noted in northeast Montana behind the
front, mostly in the 20 to 30 mph range. Scattered light showers
well out ahead of the front on the nose of a plume of warm air
advection are passing through the Turtle Mountains area. Meanwhile,
a more persistent area of rain trails the cold front, and is
forecast to cross the northern third of the state this morning.
Forecast thinking for the strong to marginally severe storm
potential this afternoon and early evening remains on track.


&&

.DISCUSSION...
Issued at 422 AM CDT Mon Aug 11 2025

A shortwave trough moving through southern Alberta/Saskatchewan
early this morning will dig into the Northern Plains this afternoon.
An attendant surface cold front will also move across the state from
northwest to southeast this morning through the afternoon. This
combined forcing is forecast to produce isolated to scattered
showers and thunderstorms across the state during the afternoon and
early evening. Coverage of showers and storms may be greatest across
northern parts of the state where stronger forcing from DCVA and the
left exit region of an upper level jet are present, but most CAMs do
simulate a broken line of convection along the cold front as it
moves through central into eastern North Dakota this afternoon and
early evening. Forecast severe parameters look fairly similar
statewide, with CAPE on the order of 500 to 1000 J/kg and effective
bulk shear around 20 to 30 kts. However, pre-frontal mesoscale
thermodynamics could be locally modified by a pooling of moisture
and compressional heating producing a narrow corridor of higher CAPE
immediately downstream of the front. There are also some hints in
model guidance for a mesoscale enhancement of shear near the frontal
interface, which would likely be supplied by a band of stronger
westerlies rounding the base of the mid/upper level trough.
Considering all this, along with the basic fact there will be a
longer duration of solar insolation ahead of the cold front, the
environment across eastern North Dakota back into the James River
Valley looks more favorable to become supportive of isolated severe
storms this afternoon and early evening. A possible limiting factor
in this threat is that the stronger shear may lag too far behind the
surface front. The rest of western and central North Dakota could
still see a few stronger storms this afternoon and early evening
with small hail and gusty winds.

Smoke continues to reduce visibility to around 2 to 5 miles across
most of western and central North Dakota early this morning. It may
take until the passage of the cold front to fully clear out the
smoke, but it should still not be as impactful today as it was
yesterday. Gusty northwest winds will be possible along and behind
the cold front, with maximum forecast gusts around 25 to 30 mph.
High temperatures today are expected to range from the mid and upper
70s north to lower and mid 80s south. Lows tonight in the post-
frontal air mass are forecast in the 50s.

Surface high pressure is forecast to expand over the western and
central Dakotas on Tuesday under northwest anticyclonic flow aloft.
The lingering post-frontal air mass lowers the high temperature
forecast by a few degrees for Tuesday, with lower 70s northeast to
lower 80s southwest. A low-amplitude transient ridge is forecast to
eject off the Northern Rockies Tuesday night and push an elevated
warm front across the region early Wednesday. This adds around 5 to
10 degrees to the high temperature forecast on Wednesday, ranging
from the upper 70s northeast to lower 90s southwest. The warm front
could also produce some light morning showers, but deep atmospheric
moisture appears lacking. The transient ridge looks to be followed
by a compact shortwave that could reach the western Dakotas by
Wednesday evening. This feature seems likely to produce at least a
small area of showers and thunderstorms as it moves across the
region through Wednesday night, with higher probabilities across
southern North Dakota than to the north. There is some uncertainty
on the degree of moisture, instability, and shear that will be
available for convection on Wednesday, but current ensemble means
project lower to mid 60s surface dewpoints, 1000 to 2000 J/kg
MUCAPE, and 0-6 km shear around 30-40 kts by 00Z. The SPC has
introduced a Marginal Risk for severe weather across the southern
half of the state for this potential, which could carry through
Wednesday night on account of an increasing low level jet.

On Thursday, ensembles appear to be consolidating on a cold front
being driven through the Northern Plains by a strong upper low
crossing southern Canada. Depending on the timing of the front and
the strength of downstream capping, a severe risk with a higher
threat ceiling could emerge. Areas that remain ahead of the front
through peak heating will likely experience their warmest day of the
week on Thursday, with pre-frontal highs forecast to reach the mid
80s to lower 90s. A more stable and cooler post-frontal air mass on
Friday could then be followed by broad ridging building over the
region for the weekend.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 655 AM CDT Mon Aug 11 2025

A cold front approaching KXWA at the start of this forecast period
will continue to push southeastward across North Dakota this morning
and afternoon. The front is expected to clear the smoke out, but
until it arrives, visibility will continue to be reduced to MVFR/IFR
levels. South-southwest winds around 10 kts ahead of the front will
quickly turn to the northwest with the frontal passage and increase
to 15-20 kts, with gusts as high as 25-30 kts. Scattered showers and
thunderstorms are also expected throughout the day, with higher
probabilities for rain across the north this morning. A few stronger
storms are possible this afternoon and early evening, with small
hail and erratic wind gusts. Heavier showers and storms could also
briefly reduce visibility as low as IFR. Aside from smoke and
outside of heavier showers and storms, VFR conditions are
expected.

&&

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

&&

$$

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