618
FXUS63 KBIS 220242
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
942 PM CDT Mon Sep 21 2026

.KEY MESSAGES...

- A gradual warming trend is forecast through the week, with
   highs in the 60s today increasing to the 70s and lower 80s
   by Thursday and Friday.

- Best chance (60-90%) for showers and thunderstorms will be
  late Tuesday night through Wednesday night. Outside of this
  period will be mainly dry till late next weekend.

&&

.UPDATE...
Issued at 940 PM CDT Mon Sep 21 2026

Low level stratus has moved into the far southwest. In the south
central where there could be patchy fog later, dew points in the
40s have been advecting in. Low temperatures are forecast in the
low 40s as well. Confidence however is still fairly low for
fog based on models.


UPDATE
Issued at 625 PM CDT Mon Sep 21 2026

Little updates to make this evening. Added fog to the southern
Missouri River valley and parts of the southeast for tonight.
Confidence is low as now with the forecast wind speed.

&&

.DISCUSSION...
Issued at 250 PM CDT Mon Sep 21 2026

Currently, slow moving mid level low over the Upper Mississippi
Valley continues to push east, with weak upper level ridging
over the Rockies and south central Canada. Lingering boundary
layer moisture continues to result in diurnally driven CU over
some areas of the local region, which has been on the decrease
the past few hours. Comfortable temperatures in the 60s this
afternoon with light winds.

Will see increasing southerly return flow for tomorrow as a lee
side sfc low develops across the Northern High Plains in
response to a decent mid level S/WV moving northeast out of the
Desert Southwest into the Wyoming Rockies. The increased
pressure gradient will see breezy south/southeasterly winds
during the day Tuesday, though lack of WAA results in similar
temperatures as today (60`s).

This wave continues northeast and moves over the Northern Plains
from late Tuesday night before exiting Wednesday night. This
feature brings the best chances for precipitation this week, and
also may result in a few thunderstorms.

S/WV ridging on Thursday brings the better WAA into the region
for the week, with forecast high temperatures closer to normal
if not above, well into the 70s to mid 80s. Thereafter, a
quasi-southwesterly flow develops supporting near normal highs
and lows, and mainly dry weather. NBM and ensembles then suggest
another increase in POPs later next weekend/early next week,
when the base of a western CONUS trough is projected to move
through.

&&

.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 940 PM CDT Mon Sep 21 2026

VFR this evening, before becoming MVFR or possibly IFR with low
CIGs in the southern half of the state overnight. There is a
chance of fog near the Missouri River and east, although
confidence as of now is low. Included a VCFG at KBIS. Tuesday
afternoon winds will gust to 20-30kts from the south.

&&

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

&&

$$

UPDATE...Smith
DISCUSSION...NH
AVIATION...Smith