822
FXUS63 KBIS 171955
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
255 PM CDT Thu Jul 17 2025

.KEY MESSAGES...

- Medium chances for showers and thunderstorms tonight through
  Friday morning, and again Saturday night through Sunday. A
  few strong to severe storms are possible both tonight and
  Saturday night.

- Temperatures warm back closer to average this weekend into
  early next week.

- Daily chances for showers and thunderstorms through next week.

&&

.DISCUSSION...
Issued at 255 PM CDT Thu Jul 17 2025

Well below average temperatures continue from this morning,
especially under areas with cloud cover. A surface low and small
shortwave is setup in central Montana, with a warm front
extending east and south from it. Strong to severe storms are
possible as that front and wave slowly move east tonight (more
on that below). Lows tonight will be warmer than last night,
with the warm front entering and the high pressure leaving the
state. Expect lows in the upper 40s to upper 60s.


Severe storm potential tonight:

SPC has the southwest and south central in a marginal (level 1)
risk, with a slight (level 2) in a portion of four southwest
counties. Timing is about midnight to 6am CT, as the front and
wave move in. The MUCAPE over 1000 J/kg stays in Montana and
South Dakota, but we do have around 500 J/kg in most models.
Some of the CAMs have the 1000 J/kg contour close to the
southwest. The shear however is very high, we are looking at
50kts of shear. So if a storm can get an organized updraft it
should be able to sustain and produce hail up to ping pong size.
A challenge with this event is confidence and location. Most of
the CAMs have similar storm mode (multi-clusters) but the
locations are varying by about 2 counties north or south. Timing
is also slightly different but only by 1 hour. The average
consensus is storms moving in from Montana after midnight,
either grazing the southwest, or moving across the west into the
south central. Then these storms could linger in the central
and east until the wave fully moves out and into Minnesota by
late morning.

Friday will be warmer with highs in the 70s as zonal flows
allows the cooler air to move east. Friday will also be mostly
dry with light and variable winds as the surface low pressure
moves through the state. This weekend another shortwave and
upper level low sets up leading to more chances for strong to
severe storms Saturday evening and Sunday. Saturday again looks
like most of the 1000+ J/kg of CAPE stays west and south of our
area, but shear is around 40kts. SPC has the western part of the
state in a marginal for the time being. Saturday will also be
warmer with highs in the upper 70s.

Sunday the machine learning guidance has a level 1 risk across
most of the state. This time the CAPE axis is in the state. The
potential is there for CAPE to be over 2000 J/kg with 30-40kts
of shear. SPC has no day 4 outlook yet for this. Sunday in the
far west could reach the upper 80s which would add to the severe
threat. Dew points look to be in the low to mid 60s, which
would make sense that the CAPE could be that high then.
Sunday`s threat is from the diffluent flow over the state off
the shortwave to our west, and surface flow from the south. The
rest of the forecast looks to stay active with southwesterly
flow aloft and temperatures staying in the 80s. Sunday and
Monday could be a longer stretch of showers and thunderstorms so
QPF could be around 1 inch in the central and east.


&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 255 PM CDT Thu Jul 17 2025

VFR this afternoon and most of the evening. MVFR is possible in
thunderstorms (mainly west and east). Thunderstorm confidence is
less in the north including KMOT, and around KDIK so used
PROB30 there. Erratic winds are possible with these storms.
Otherwise winds will be easterly, switching to northeast Friday
late morning. Late in the period south central and east will
likely have IFR to LIFR CIGs.

&&

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

&&

$$

DISCUSSION...Smith
AVIATION...Smith