453
FXUS63 KBIS 100859
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
359 AM CDT Mon Jun 10 2024

.KEY MESSAGES...

- Widespread showers and thunderstorms (80 percent chance) are
  expected today through tonight. Isolated to scattered severe
  thunderstorms are possible across western and south central
  North Dakota (level 1 out of 5 risk; level 2 out of 5 in
  Bowman and Adams counties).

- Near normal temperatures expected today and Tuesday. Highs on
  Wednesday will be warmer, in the 80s, possibly reaching 90 in
  the southern James River Valley.

- Chance for showers and thunderstorms (30 percent) return
  Wednesday evening, before higher chances for precipitation at
  the end of the week and through the weekend.

&&

.DISCUSSION...
Issued at 359 AM CDT Mon Jun 10 2024

This morning, a shallow ridge aloft was moving into western
North Dakota, while a shortwave trough was in place over the
Northern Rockies, moving east. A surface low associated with the
trough was beginning to deepen in northwest Montana, with low-
level warm air advection spreading across eastern Montana and
western North Dakota ahead of the approaching system. Scattered
thunderstorms were ongoing in eastern Montana and southwest
North Dakota as a low- level jet strengthened, but in an
environment of very little bouyancy and weak bulk shear.
Additional showers were visible on radar across the rest of
Montana and into Wyoming. Southeast surface winds were beginning
to strengthen in response to the low deepening.

The expectation for today is for showers and thunderstorms to
become more widespread as the surface low deepens and approaches
from the west. High-res guidance is painting a relatively
consistent picture in convection spreading northeast, initially
along the warm air advection before additional development along
a cold front as it pushes east through the afternoon and
evening, following the trough axis. This afternoon into the
early evening is the most likely time we would see strong to
severe thunderstorms develop, when instability is maximized, as
that is the primary limiting factor. The 00Z HREF did back off a
bit on forecast MUCAPE, keeping values maxed out around 1000
J/kg in southwest North Dakota. Bulk shear still looks quite
sufficient for severe thunderstorms, in the 40 to 50 knot range,
while mid- level lapse rates are marginal. The tornado
potential is low but non-zero, as forecast soundings continue to
show high SRH, although this would be for a narrow window of
time this afternoon in western North Dakota. Otherwise, main
hazards are large hail up to the size of ping pong balls and
damaging wind gusts up to 60 m. Uncertainty also comes from how
earlier showers and thunderstorms, as well as widespread cloud
cover, will impact the environment later in the day and
potentially put a ceiling on storm strength. Some CAMs are
advertising isolated storms developing in western North Dakota
after the front moves through this evening, so something to keep
an eye on.

Heavy rain is also a possibility, with forecast PWATs on the
upper end of climatology, especially if some locations get
multiple rounds of heavy precipitation in a short amount of
time. Northwest North Dakota has a high probability of at least
0.50" through tonight, with a 20-40% chance of at least 1" of
rain.

Precipitation chances taper off late tonight in our eastern
counties as upper ridging begins to build into the western Canadian
Prairies, starting a modest warming trend for the Dakotas.
Tuesday should be a pleasant June day with highs in the mid 70s
to lower 80s and mostly sunny skies, with a bit of a breeze east
behind the exiting system. We warm up further still on Wednesday
as a low-level thermal ridge extends into the region, bringing
forecast highs to the 80s, with potentially some upper 80s in
the James River Valley. Our next shortwave also comes through on
Wednesday, and the timing of the wave and attendant cold front
could impact how warm temperatures get if it moves through
faster than expected. Right now, the timing of the front/wave
keeps shower and thunderstorm development just east of the
forecast area, but if this slows up, the James River Valley
could have potential for some stronger thunderstorms.

Dry and seasonable on Thursday before a more active pattern is
projected to set up this weekend, as a closed low deepens over
the Four Corners region before moving northeast through the
central CONUS. Blended POPs increase across the area Friday
afternoon and evening, continuing through the weekend and into
Monday. Southerly return flow Friday and Saturday is hinting at
increasing instability, so another window to watch for some
potentially stronger storms. Temperatures through the weekend
look to be near to slightly above normal for mid June.

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 1255 AM CDT Mon Jun 10 2024

VFR conditions to start the TAF period ahead of increasing
clouds, lowering ceilings, and widespread precipitation chances
through the period as a storm system moves through the area.
Chances for showers and thunderstorms move into western North
Dakota by 09Z, first impacting KDIK then KXWA, with
precipitation moving into central North Dakota (KMOT/KBIS)
around 18Z, and finally the James River Valley (KJMS) by 00Z.
Some strong to severe thunderstorms are possible across portions
of western and south central North Dakota during the day Monday.
MVFR ceilings are likely across northwest and north central
North Dakota Monday afternoon and evening. Additionally, MVFR
conditions are possible around heavier showers and
thunderstorms.

&&

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

&&

$$

DISCUSSION...Jones
AVIATION...Jones