217
FXUS63 KBIS 232009
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
309 PM CDT Sun Jun 23 2024

.KEY MESSAGES...

- Isolated to scattered severe thunderstorms are possible late
  this evening through Monday morning along and north of
  Interstate 94. The highest chances will be from around Highway
  2 to the International Border.

- Monday morning thunderstorms may re-intensify by late morning
  or early afternoon across the Devil`s Lake Basin or James
  River Valley. These storms could pose a brief severe threat
  before moving off to the east.

- Monday will be very warm with highs mainly in the lower 80s to
  lower 90s. It will also be quite humid across the south
  central and east with dewpoints approaching 70 in the
  afternoon.

- We mostly dry out Tuesday and Wednesday with chances for
  showers and thunderstorms returning Wednesday night through
  the rest of the week and into the weekend.

&&

.DISCUSSION...
Issued at 309 PM CDT Sun Jun 23 2024

An upper level ridge axis is currently located over western
North Dakota and will continue to move east through the day. The
location of the ridge axis is fairly apparent on satellite
imagery given the cloud free sky across the western third of
the state and fair weather cumulus over portions of the central
and east. This pattern is leading to much warmer temperatures
than in previous days and we will see highs rise into mid 70s
northeast to the upper 80s southwest.

By late this evening, the ridge will flatten a bit as a compact
shortwave starts to move across Saskatchewan and eventually into
Manitoba by early Monday morning, interacting with a low level
thermal ridge. While most of the forcing will remain well north
of the International Border, several CAMs continue to suggest
that we will see some potential supercell development across the
northern third of the forecast area (some even bringing storms
as far south as Bismarck). That being said, the HRRR/RAP has
trended towards keeping these supercells well into Canada until
they dip down into eastern North Dakota in a weakening phase
early Monday morning. Thus, the HRRR/RAP are a bit of an
outlier at the moment but it is also important to note that
these models also have access to the latest data and
observational trends. More showers and storms should develop
late tonight behind this initial wave but it remains unclear if
this activity will pose much of a severe risk.

Much of where these initial storms are going to track will
depend on where the MUCAPE gradient sets up as storms will
likely ride along and just north of that boundary. If storms can
sustain themselves across northern North Dakota tonight, they
will have a favorable environment for severe weather given
plenty of MUCAPE and shear. With DCAPE also forecast to be
around 1000 J/kg here and strong 0-3 km shear, will continue to
advertise the potential for damaging winds up to 70 mph. Will
also continue to advertise hail to the size of quarters but if
any supercells can sustain themselves and remain isolated, there
is a scenario where larger hail is possible. A low level jet
will also be on the increase through the night which will likely
lead to additional thunderstorm development late tonight
through early Monday morning. Instability will be a bit lower
with this warm air advection convection but shear will remain
strong. Thus a strong to severe storm cannot be ruled out but
the magnitude of the threat remains a bit unclear.

Convection will be ongoing through the morning hours on Monday
across portions of the north central and into portions of the
Devil`s Lake Basin and James River Valley. We will see rapid
warming on Monday so some re-intensification of this activity
is likely by late morning and into the early afternoon along a
surface trough/effective cold front. By 18z, some forecast
soundings suggest these areas may see around 2000 to 3000 J/kg
MLCAPE and deep layer shear up to 50 knots. Thus, if we do get
severe thunderstorms Monday afternoon, they will likely come
from strengthening morning convection right before they move
east and out of our area. Still, if a storm can get established
before moving out, the environment will be primed for severe
weather. Hail up to the size of golf balls and damaging winds to
70 mph would be the most likely hazards.

Monday will be very warm with most seeing highs in the lower
80s to lower 90s. It will also be very humid to the east of the
boundary with dewpoints potentially approaching 70. Dewpoints
will dip back into the 40s and 50s behind the advancing
boundary. Overnight lows will then range from the lower 50s to
lower 60s.

Tuesday and Wednesday will see mainly dry conditions with
slightly cooler temperatures. Highs will range from the mid 70s
to mid 80s both days. Precipitation chances then return to the
forecast Wednesday night through the rest of the week and into
the weekend. While it remains a long way out, CSU Machine
Learning guidance continues to increase the severe weather
threat in the Thursday/Friday time frame. The general pattern
also continues to look favorable in the various ensembles. So,
while it`s a bit too far out for specifics, it will be the next
main system to watch.

Some precipitation may linger into the weekend with some
guidance suggesting a brief cooldown.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1223 PM CDT Sun Jun 23 2024

VFR conditions are generally expected at all sites through the
period. The one exception could be tonight and into Monday
morning when a few isolated thunderstorms may track across the
northern half of the state. Considerable uncertainty remains
about how many thunderstorms will be able to form south of the
International Border, but low to medium chances (20 to 40
percent) seem reasonable north of Interstate 94 (best chances
across the northern third of the state). Will advertise some
VCTS at KISN and KMOT but all other sites are too far south to
include with confidence at this time. If any stronger storms
move overhead, brief IFR to MVFR conditions will be possible
along with gusty and erratic winds.

&&

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

&&

$$

DISCUSSION...ZH
AVIATION...ZH