463
FXUS63 KBIS 220333
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
1033 PM CDT Mon Jul 21 2025

.KEY MESSAGES...

- Isolated to scattered severe thunderstorms are possible
  tonight. Main hazards will be large hail up to 2 inches in
  diameter, damaging winds up to 70 mph, isolated tornado
  possible, and locally heavy rainfall.

- Isolated to scattered severe thunderstorms possible Tuesday
  through Tuesday night, mainly in southern and eastern North
  Dakota. Main hazards include large hail up to the size of a
  golf ball, damaging wind gusts up to 70 mph, an isolated
  tornado possible, and locally heavy rainfall.

- High temperatures will remain near average through this
  weekend. Wednesday will be slightly cooler.

- Near daily chances for showers and thunderstorms continue
  through the weekend.

&&

.UPDATE...
Issued at 1031 PM CDT Mon Jul 21 2025

Just a quick update for the new Severe Thunderstorm Watch that
covers pretty much all of south central and southeast North
Dakota.

UPDATE
Issued at 944 PM CDT Mon Jul 21 2025

We made some changes to pops with the late evening update.
Otherwise no significant changes. Convection in east central MT
moving into Golden Valley and Billings counties and perhaps
McKenzie county is running into some capping. Although this
area was uncapped earlier this evening, with sunset the low
level capping is increasing. Probabilities are low to medium of
this activity surviving for any extended period of time. There
was some gusty winds with the convection as it moved into Golden
Valley county so some locally strong wind gusts to 40-50 mph are
possible with this activity through around 10 PM MDT.

Farther to the south strong convection over southern Perkins
county in northwest SD is pushing to the east northeast. With a
sustained current movement, this would put it near or just east
of the Missouri River as it pushes into ND around 11-1130 PM
CDT. Additional showers and thunderstorms are also developing
over northwest into west central SD and are expected to lift
northward as a very warm and unstable airmass lifts northward,
along with an increasing low level jet and an approaching
shortwave from the west. Would not be surprised if we see an
additional watch that runs along the ND/SD border late this
evening into the overnight hours. Cams do show this general
idea, but are varying in agreement. Will continue to monitor.

UPDATE
Issued at 608 PM CDT Mon Jul 21 2025

No significant updates since the issuance of the Watch
Notification. Convection continues over northeast Wyoming and
southeast MT. Currently the most vigorous convection is back a
bit farther west over Rosebud and Big Horn counties, south and
west of Miles City. Convection farther east is having a harder
time maintaining itself. updated text products will be
transmitted shortly.

UPDATE
Issued at 502 PM CDT Mon Jul 21 2025

Quick updated to add the severe thunderstorm watch for far
southwest ND through 11 PM MDT. Also made a few minor updates to
pops early this evening. At this time it looks like the greater
threat for ND will be this evening, rather than this afternoon
due to high convective temps and lack of forcing. Possibly
even mid-late evening. However we do have convective initiation
over northeast Wyoming and southeast Montana that is heading
this way. Initial convection may have a hard time making it into
the state though. Will continue to monitor.

&&

.DISCUSSION...
Issued at 325 PM CDT Mon Jul 21 2025

An active southwest flow pattern continues today and tonight,
leading to another round of possible severe storms overnight. At
the surface a Colorado Low slowly moves northeast through South
Dakota, with a east/west warm front. Currently the skies of the
Dakotas are quiet with a lack of forcing. Here in North Dakota,
limited diurnal cumulus have formed at 2kft, where the cap has
lifted. Without any type of forcing, and a convective
temperature around 100 degrees, no storms will even start to
form with highs today only in the mid 80s. It wont be until
that surface low and inverted trough move into the area when
storms can get going. A low level jet could nudge into the state
after midnight sparking more storms in the south central. The
inverted trough will be in western North Dakota, and lead to a
linear storm mode. In the south central closer to the low,
discrete cells could form, leading to hail and maybe a tornado
chance. All this likely will happen after 9pm CT. Currently at
3pm CT there is already 3000 J/kg of MUCAPE and 45kts in the
central and south. These values are forecast to continue through
the night.

Tuesday another chance for isolated to scattered severe storms
are possible. This time more east. SPC on their day 2 update
this afternoon, expanded the slight risk west through the James
River Valley. The marginal risk is the same as before. The
MUCAPE values looks to be high again, with 35 to 50kts of
shear, so we will expect the same hazards as today. It is almost
and copy and paste of today, just moved to the east.

The latter half of the week through the weekend the active
southwest pattern continues. The exception is Wednesday when a
quick short ridge moves in. Temperatures will dip into the 70s.
Other than that, temperatures will remain about average in the
80s with daily shortwaves leading to showers and thunderstorms.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 608 PM CDT Mon Jul 21 2025

VFR conditions to begin the 00Z TAF period. Another night
possible strong to severe convection spreading from southwest to
northeast across the forecast area. For all TAF sites brought a
4-6 hour window of a Prob30 with Thunderstorms and MVFR vsbys in
showers, beginning at 03 UTC at KDIK. After convection passes
most areas will see a period of MVFR ceilings Wednesday morning
before conditions improve late morning and afternoon. Kept any
Tuesday afternoon convection out of the TAFs for now. Generally
an easterly surface flow is expected through the TAF period
AOB 15kts.

&&

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

&&

$$

UPDATE...TWH
DISCUSSION...Smith
AVIATION...Smith