357
FXUS63 KBIS 180554
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
1254 AM CDT Tue Aug 18 2026

.KEY MESSAGES...

- Low to medium chances (20 to 40 percent) for scattered showers
  and thunderstorms on Wednesday, then mainly dry Thursday
  through Saturday afternoon.

- Mainly seasonable temperatures this week, with above normal
  high temperatures on Thursday.

&&

.UPDATE...
Issued at 1253 AM CDT Tue Aug 18 2026

Isolated showers continue across the region, with two main
clusters from the southern James to southern Red River Valleys
and in far northeast Montana, respectively. No lightning has
been observed with these showers recently, but an occasional
thunderstorm cannot be ruled out. Effective bulk shear is high,
but there does not appear to be enough CAPE to support any
severe convection. The northeast Montana cluster, which appears
to be tied to low level frontogenesis, could slide
southeastward into northwest and central North Dakota through
the night.

UPDATE
Issued at 1013 PM CDT Mon Aug 17 2026

Latest guidance continues to show various areas of convection
possibly developing overnight. Thus, will continue to generally
keep low precipitation chances in through the night over most
locations. With that said, instability has waned back some, so
think the severe threat has diminished, but cant rule out a
little small hail or a modest wind gust over far southern
portions of the area.

UPDATE
Issued at 628 PM CDT Mon Aug 17 2026

Isolated thunderstorms continue over southern portions of our
area as a short wave continues to swing around broad upper low
centered over far southwest Hudson Bay. Additional short waves
wrapping around the low continue to produce additional storms
upstream in eastern Montana. So far the overall trend has been
that some storms get a little strong for a bit, but have mainly
remained sub-severe. With that said, instability and shear
continue to be high enough for a storm to possibly become
severe, mainly over our far southern areas. Therefore, will
continue to monitor through the evening.

&&

.DISCUSSION...
Issued at 250 PM CDT Mon Aug 17 2026

Currently, quasi-zonal/west-northwest flow aloft with a large
area of upper level low pressure over Hudson Bay and an upper
level ridge of high pressure extending from the Southern Rockies
back north-northwest into the Intermountain West. Cold front
situated roughly from southwest North Dakota northeast into the
Northern Red River Valley. Embedded mid level impulses
contributing to two areas of precip activity this afternoon. The
first is over northwestern ND where scattered showers are moving
into, and the second area is over southwestern ND along and
ahead of the frontal boundary aided by left exit region jet
dynamics aloft. There is enough effective wind shear (35-40
knots) for a few stronger/more organized updrafts over the past
couple hours, with one severe storm firing up just across the
border in northwest South Dakota. I opted to mention the entire
far south in the HWO, with the Marginal (level 1 of 5) outlook
near or over this area. Threat for severe weather should
decrease with time as we lose daytime heating and as the front
moves farther to the south.

Jet streak moving through aloft along with additional mid level
impulses will maintain chances for showers and perhaps a few
thunderstorms tonight across the local area. Threat for severe
weather will be very low after peak heating as the more robust
storms remain more to our south.

Surface high pressure builds into western and central North
Dakota tonight into tomorrow, and will result in the weather
trending dry, lowering dewpoint temperatures, and cooler
temperatures mainly in the 70s to around 80.

Increasing return flow Tue night west as sfc high pressure
slides off to the east, with models depicting a mid level wave
also approaching Tue night through early Wed, resulting in the
next chance for precipitation. Despite northwest flow aloft,
temperatures will warm mid-week back into the 80s on Wednesday,
then well into the 80s and lower 90s for Thursday as the
aforementioned upper ridge broadens and nudges east (increasing
southerly mid level flow). Mainly dry weather and seasonal
temperatures to end the week as the upper ridge continues to
develop east into the Great Plains. Ensembles then show the
ridge breaking down later in the weekend into early next week,
with shower and thunderstorm chances returning to the forecast
and continued seasonal temperatures.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1253 AM CDT Tue Aug 18 2026

VFR conditions are expected to prevail through the forecast
period. Isolated showers are possible through the night, but
the probability of one passing over a terminal is low. Winds
will remain light and variable, with 5-10 kt northwest winds
Tuesday afternoon.

&&

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

&&

$$

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