463
FXUS63 KBIS 210520
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
1220 AM CDT Thu Aug 21 2025

.KEY MESSAGES...

- Isolated severe thunderstorms possible in the east Thursday.

- Much cooler temperatures, lower humidity, and mainly dry
  weather is expected Friday through Tuesday.

- Breezy northwest winds may be found Thursday through Saturday.

&&

.UPDATE...
Issued at 1215 AM CDT Thu Aug 21 2025

No significant changes needed for the early overnight update.

UPDATE
Issued at 929 PM CDT Wed Aug 20 2025

A cold frontal boundary has entered far northwestern ND and will
pass through the state tonight and during the day Thursday. A
few showers and thundershowers have developed ahead of the
frontal boundary mainly in the far southwest. However, storms
have failed to take off and it`s looking even less likely that
they will. In addition, nothing of significance has developed
near the ND and Canadian border to this point, with the latest
CAMs backing off earlier afternoon runs. In fact, the latest
HRRR run now keeps thunderstorms almost entirely in southern
Canada through most of tonight, and this is looking like the
most likely solution. That said, a separate round of showers,
along with a few thunderstorms, is likely to develop late
tonight and during the day Thursday as the frontal boundary
continues progressing eastward. These are also unlikely to
become strong to severe through at least Thursday morning.

UPDATE
Issued at 706 PM CDT Wed Aug 20 2025

Heat index values will continue to gradually decrease as the sun
sets, therefore allowed the Heat Advisory to expire on time.
Otherwise, a few showers, along with a few rumbles of thunder,
have developed in southeastern Montana and south central Canada
near the ND border. So far, however, there has been enough
residual capping to prevent any solid thunderstorms from
developing. Still, a few CAMs still suggest storms remain
possible this evening, especially in the north central near the
Canadian border as the LLJ strengthens. Should storms manage to
take off, the ingredients remains for a few severe
thunderstorms to develop.

&&

.DISCUSSION...
Issued at 427 PM CDT Wed Aug 20 2025

Warm and breezy conditions will continue into this evening ahead
of an approaching cold front. Heat Advisory criteria will be
found across western and much of central North Dakota during
this time, thus have maintained the Heat Advisory. Some other
central portions not in the advisory may get close to advisory
level criteria, although these reports are expected not to be
widespread enough for advisory expansion. SPC has maintained a
Marginal Risk (Level 1 of 5) for severe weather across northern
and western North Dakota through tonight. This risk is highly
conditional on thunderstorm development along a capped warm
front in the north, or along the cold front that will move
through this evening through tonight. CAPE values remain high,
yet are fairly capped with the abundant warm air aloft. Shear is
also modest and would promote multicells to supercells along the
warm front, and multicells to linear along the cold front. Given
the uncertainty left the messaging of main hazards being hail up
to ping pong ball size and winds to 60 mph. Supercells would
bring larger hail size, while linear mode could bring higher
winds. SPC does have 2% tornado risk in the north. There is
decent low level shear in this area and forecast hodographs do
support this threat. LCLs may be a bit high and the storms would
have to be surface based and supercell storm mode which also
remains uncertain. So an isolated tornado is possible this
evening, although confidence is not high enough to message. The
threat for severe diminishes overnight tonight, although showers
and thunderstorms may linger as the front continues to move
through. There may also be some patchy fog in the more humid air
in the east, although increase winds should limit the fog
threat. Cold front finishes push through during the day
Thursday. Cooler temperatures will be found, with chances for
showers and thunderstorms along the front. SPC has a Marginal
Risk (Level 1 of 5) in the east. Here high instability and
modest shear will be found. There may still be some capping
concerns, and the shear vector would imply multi cluster to
linear storm mode is favored. Thus similar hazards to today
would be found, with limited tornado threat. Winds will change
to the north and may be breezy in some areas. After a cool and
mainly dry night Thursday night, Friday looks to be more a post
frontal day. Mainly dry, cool, and breezy conditions will be
found. Morning lows are forecast in the 50s with highs in the
70s.

Saturday through early next week will see mainly dry northwest
flow aloft. This could bring some breezy conditions, although
most will more notice the much cooler temperatures. Highs each
day will be in the 60s to 70s. Lows will also be cooler and may
be in the 40s each night. With broad ridging upstream, limited
chances for precipitation will also be found during this time
period.

&&

.AVIATION /06Z TAFS THROUGH 06Z FRIDAY/...
Issued at 1215 AM CDT Thu Aug 21 2025

A cold frontal boundary currently pushing into western ND will
pass through the forecast area by late Thursday afternoon.
Showers and a few thunderstorms are expected with this passing
frontal boundary. However, confidence remains low in the exact
placement and timing of any precipitation. Thus left out
mentions in all TAFs for the time being, except KJMS where
probabilities are a little higher. A few hours of LLWS are
expected across central ND ahead of the frontal passage.

&&

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

&&

$$

UPDATE...TWH
DISCUSSION...Anglin
AVIATION...TWH