389
FXUS63 KBIS 201738
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
1238 PM CDT Thu Aug 20 2026

.KEY MESSAGES...

- Near average temperatures through the middle of next week,
  with highs mostly in the upper 70s to upper 80s.

- Low to medium chances (30 to 50 percent) for showers and
  thunderstorms late Saturday into early Monday.

&&

.UPDATE...
Issued at 1238 PM CDT Thu Aug 20 2026

A little diurnal cu is starting to develop in the north, and
will probably expand across more of the forecast area over the
next few hours before dissipating. Otherwise, quiet weather
continues today.

UPDATE
Issued at 844 AM CDT Thu Aug 20 2026

The forecast remains on track.

UPDATE
Issued at 640 AM CDT Thu Aug 20 2026

The forecast remains in good shape. Radar continues to show
light shower activity from near Harvey to Jamestown to Oakes,
but much of this may not be reaching the ground and is likely
only producing trace amounts at most. Quiet weather should
prevail today, with breezy northwest winds in the eastern half
of the state.

&&

.DISCUSSION...
Issued at 340 AM CDT Thu Aug 20 2026

Northwest flow pattern continues over the Northern Plains early
this morning between a Hudson Bay low and Desert Southwest
ridge. Two pockets of isolated showers from north central North
Dakota to the southern James River Valley are traveling east-
southeastward. The northern showers should remain very light,
but lightning has become consistently observed in LaMoure and
Dickey Counties. Nevertheless, these thunderstorms will soon be
departing the forecast area. Dry weather is anticipated for the
rest of the day as weak surface ridging builds down from
Saskatchewan. High temperatures this afternoon should be similar
to those observed yesterday, except a bit cooler across the far
north, ranging from the mid 70s in the Turtle Mountains to near
90 in the far southwest.

Another low-amplitude shortwave embedded in the northwest flow
is forecast to move through the state on Friday. Most guidance
produces at least some shower activity moving from northwest
North Dakota in the morning through central and into southeast
North Dakota through the afternoon, with the HRRR and NAMnest
being notably more bullish on coverage and QPF (albeit still
very light). Despite strong vertical shear, ensemble guidance
shows little to no CAPE on Friday, keeping thunderstorms out of
the forecast. The upstream ridge is forecast to become highly-
amplified over the Rockies heading into the weekend before being
shoved eastward by a potent shortwave landing on the Pacific
Northwest coast. But the eastward progression of these features
could also be stagnated by a downstream trough digging into the
Great Lakes. Saturday should remain dry during the daytime with
the Northern Plains under deep-layer subsidence. Later Saturday
night into Sunday, weaker shortwave energy preceding and loosely
associated with the more potent Pacific Northwest wave could
begin ejecting into the Northern Plains. Then from Sunday night
into Monday, the potent shortwave is forecast to eject off the
Canadian Rockies into the southern prairie provinces, with
southward extending frontal boundaries traversing North Dakota.
This gives us the highest chances for a more widespread
rainfall over the 7-day forecast period. NBM PoPs have risen
slightly, with maximum values around 30 to 50 percent at any
given location and temporally highest Sunday evening. There is
still timing uncertainty for when the strongest forcing will
cross western and central North Dakota, but a late afternoon/
evening passage on Sunday could support strong to severe
convection as models show a plume of higher mixing ratios
advecting poleward through moderate to high deep layer shear.
Confidence in the severe storm potential is quite low however,
as deterministic model soundings show a capping inversion and
CSU machine learning severe probabilities remain under 5
percent. There is also a low probability outcome that the
progression of the Canadian shortwave could be slowed enough
for a thunderstorm risk to remain in central/eastern North
Dakota through Monday afternoon.

Ensemble consensus favors the Canadian shortwave digging
southeastward toward the Great Lakes by the middle of next week
as the western CONUS ridge re-amplifies once again. Beyond that
point in time, ensembles begin to diverge on whether the ridge
axis will shift back over the Plains or remain stationed over
the Rockies through the second half of next week. Despite all
the aforementioned regional pattern shifts, the NBM shows very
small variability in day-to-day temperatures through the middle
of next week, with near average highs in the upper 70s to upper
80s and overnight lows around 50 to 60. Analysis of distribution
trend lines shows that Monday is favored to be a comparatively
warmer day at most locations.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1238 PM CDT Thu Aug 20 2026

A few showers may develop late tonight and into Monday morning,
mainly in northern North Dakota, though confidence was too low
to include in any TAFs for now. Otherwise, VFR ceilings and
visibility are expected through the period.

&&

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

&&

$$

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