438
FXUS63 KBIS 240604
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
104 AM CDT Mon Jun 24 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.

&&

.MESOSCALE...
Issued at 102 AM CDT Mon Jun 24 2024

At 1 AM CDT, two long-lived supercells were nearing the Canadian
border, about to cross into Burke and Renville Counties. Environment
Canada has relayed a report of golf ball size to  2-inch
diameter hail covering the ground in Estevan, Saskatchewan.
These storms` intensity have long outlasted 00Z CAM simulations,
though more recent runs of the HRRR are beginning to catch on.
Current storm motion on the right-moving Bunkers vectors takes
the storms away from the analyzed MUCAPE gradient. However,
that gradient is forecast to shift eastward with the storms as
elongated 850 mb moisture transport vectors turn to the
northeast. Should the more unstable environment continue to
translate downstream, these storms are likely to remain severe
as they cross far north central North Dakota into the Turtle
Mountains and Devils Lake Basin given effective bulk shear of at
least 50 kts. The Storm Prediction Center has issued a Severe
Thunderstorm Watch for Burke, Renville, Ward, Bottineau,
Rolette, McHenry, and Pierce Counties until 5 AM CDT.

&&

.UPDATE...
Issued at 950 PM CDT Sun Jun 23 2024

Limited updates needed this evening. Strong storms from an upper
level shortwave remain in southern Canada, while much of the
state remains capped. The storms in Canada will be worth
monitoring through the overnight hours. The Bunkers right moving
vector is east southeast which could slowly bring them closer
to the International Border. As the storms move eastward they do
enter into decreasing instability, although shear will remain
high. Thus severe weather is possible if these storms can enter
into ND. Meanwhile, later tonight into Monday morning a cold
front will move across the state. This could be the next focus
of showers and thunderstorms, and perhaps some isolated severe
weather. Instability along this front will not be as high as it
is currently, although should be less capped. Abundant shear and
a strong low level jet could help overcome this lowering
instability. Thus an isolated severe storm will be possible with
passage of this front. For now made minimal changes to the
forecast and will continue to monitor if any strong to severe
storms can develop.

UPDATE
Issued at 650 PM CDT Sun Jun 23 2024

Little needing updating at this point. The shortwave that may
bring thunderstorms tonight has developed thunderstorms in
southern Saskatchewan. Most CAMS have these placed correctly
currently, however, half of them keep storms in Canada while the
other half want to bring storms into ND. Part of this wave is
starting to bring isolated thunderstorms in northeastern MT as
well. As this wave moves eastward it will meet a strengthening
low level jet in western ND, which could help promote
thunderstorm development. At this point the uncertainty remains
moderate to high so left PoPs as is. With the nocturnal
potential for storms tonight, all want to make sure they have
multiple ways to receive severe weather updates at night.

&&

.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 /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 102 AM CDT Mon Jun 24 2024

Showers and thunderstorms are possible across western and central
North Dakota overnight into Monday morning before shifting off to
the east. A few storms could be strong to severe, with the highest
chance of a severe storm north of KMOT. VFR conditions are otherwise
expected through the forecast period. Southeast winds overnight will
turn to the northwest on Monday, increasing to 10-15 kts with a few
20-25 kt gusts during the afternoon.

&&

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

&&

$$

MESOSCALE...Hollan
UPDATE...Anglin
DISCUSSION...ZH
AVIATION...Hollan