Jamestown, North Dakota 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

841
FXUS63 KBIS 120030
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
730 PM CDT Sat Apr 11 2026

.KEY MESSAGES...

- Areas of dense fog could develop along and east of Highway 83
  this evening through early Sunday morning.

- Isolated to scattered showers will move across the state from
  southwest to northeast this evening through Sunday morning. A
  few thunderstorms are possible in southwest North Dakota this
  evening.

- Above normal temperatures for the most part through the middle
  of next week, with additional medium to high chances for rain
  on Monday.

- Significant cool down possible for the end of next week, with
  medium chances for both rain and snow.

&&

.UPDATE...
Issued at 729 PM CDT Sat Apr 11 2026

Already seeing signs of visibility lowering in the James River
Valley. Have increased and expanded the coverage of fog across
central and into eastern North Dakota this evening through early
Sunday morning. Webcams have also shown signs of drizzle in the
southern James River Valley, where a patchy mention has been
added to the forecast through mid evening. RAP guidance suggests
the depth of the near-surface saturated layer will become less
favorable for drizzle overnight.

Scattered showers and isolated thunderstorms were entering
southwest North Dakota at the time of this writing. No notable
wind gusts have been observed upstream in southeast Montana and
northwest South Dakota, and there have only been brief spikes in
reflectivity with a couple of storms to the southeast of Miles
City. SPC mesoanalysis shows increasing surface and mixed-layer
CIN, which is related in the latest lightning observations. But
downstream MUCAPE is still around 1000 J/kg, so cannot rule out
a thunderstorm or two in southwest North Dakota through the
evening. Brief downpours and perhaps some very small hail no
larger than pea-size would be the expected hazards with the
strongest storm.


&&

.DISCUSSION...
Issued at 253 PM CDT Sat Apr 11 2026

This afternoon, a deep trough and closed low were placed off the
California coast, leading to downstream southwest flow across
the Dakotas. At the surface, a broad area of low pressure was
analyzed over eastern Montana, with a moderately tight surface
pressure gradient across the forecast area that was producing
breezy southeasterly winds. There is also a large area of low
stratus that extends from the Turtle Mountains through the James
River Valley and east, and goes far enough west to be on the
edge of the Bismarck/Mandan area. Low confidence in the
progression of the western extent, but high-res guidance all
agrees on our eastern counties being socked in for the rest of
today and through tonight. Underneath this stratus are afternoon
temperatures in the 40s and occasionally some drizzle in the
eastern James River Valley. Meanwhile, western North Dakota has
plentiful sunshine and afternoon highs in the 60s and 70s.

Just upstream, we are already starting to see some scattered
convection develop with a shortwave and 300mb jet streak moving
through the mean southwest flow over Wyoming, with activity
expected to move into southwest North Dakota this evening before
expanding across the forecast area tonight. Carrying a broad 20
to 40 percent chance of showers and thunderstorms, with
deterministic guidance showing at most a few hundred j/kg of
instability available for some rumbles of thunder across the
west and central. The other main forecast concern tonight is fog
development across the eastern half of the state underneath the
low stratus, with patchy fog included in the gridded forecast
into Sunday morning.

Precipitation chances taper off Sunday morning as the upper
wave and attendant surface low exit to the northeast, with skies
clearing and winds turning more westerly and breezy. Sunday
looks like the warmest overall day of the period, with forecast
highs in the upper 50s north to the mid 70s south. We did opt to
skew up to NBM50 for forecast high temperatures and blended
down dew points just a touch, due to the west- northwest winds
forecast and the deterministic NBM being on the cool side of the
ensemble spread.

The next round of precipitation comes late Sunday through
Monday, as another wave ejects out of the trough base that will
be over the western CONUS. Some guidance wants to have a more
northern stream wave separate from the main trough, but
regardless, there`s decent ensemble agreement on precipitation
chances as latest NBM POPs are up to 60 to 80 percent across
western North Dakota on Monday. There are low to medium chances
for at least a quarter inch of QPF with this event, focused over
western North Dakota.

Temperatures stay seasonable Tuesday and Wednesday with not too
much wind, and low chances for rain focused on far southern
North Dakota as a few waves pass to our south. Focus then turns
to late in the week as a more substantial shortwave is progged
to move in from our west, bringing chances for rain and snow as
well as much cooler temperatures to end the work week. It is
worth noting all four ensemble clusters have at least some snow
associated with this system, and certainly more confidence in
the cooler air moving in, but plenty of details to be worked out
before then.

There are then hints of cooler than normal temperatures
continuing into the week 2 period and potentially beyond,
although average highs increase to the lower 60s by the end of
the month. The active pattern is also favored to continue at
least broadly across the region.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 729 PM CDT Sat Apr 11 2026

LIFR ceilings will prevail across the eastern half of North
Dakota through tonight, likely spreading as far west as KMOT
and KBIS. Fog is also likely to develop under the low clouds
later this evening through tonight, and may become dense. The
low clouds are forecast to gradually lift and erode from
southwest to northeast through the day Sunday.

Scattered showers and isolated thunderstorms will move into
southwest North Dakota this evening, possibly impacting KDIK.
The chance of scattered showers then spreads northeastward
overnight into Sunday morning and departs to the northeast
Sunday afternoon. A brief period of MVFR or IFR conditions
could occur with heavier showers and storms.

Southeasterly winds will gradually weaken through the evening,
then turn to the west-northwest on Sunday around 15-20 kts.

&&

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

&&

$$

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