007
FXUS63 KBIS 101358
AFDBIS

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

.KEY MESSAGES...

- Showers and thunderstorms, presently in the west and expanding
  east, will persist 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 average temperatures expected today and Tuesday. Highs
  on Wednesday will be warmer, in the 80s, possibly reaching 90
  in the southern James River Valley of North Dakota.

- 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.

&&

.UPDATE...
Issued at 858 AM CDT Mon Jun 10 2024

A boomerang shaped line of showers, with thunderstorms on the
backside, is present on an axis from approximately Williston to
Hazen to New Salem. These showers and thunderstorms will
continue pushing east northeast through the morning hours. Based
on any instability persisting more to the south and west of the
line, expect any thunderstorms to remain on the backside,
though lightning activity may diminish as the line heads north
and east into a more stable environment. The next wave of
showers and thunderstorms is then expected to move from west to
east through the area early this afternoon. Adjusted PoPs based
on the latest radar trends.

UPDATE
Issued at 646 AM CDT Mon Jun 10 2024

A large area of showers and thunderstorms are ongoing from
Watford City, to Elgin, and back to Dickinson and just north of
Beach as of 1130 UTC, with some isolated showers developing
east of this area. The NDAWN station south of Beach reported
about half an inch of rain in one hour, so even these smaller
thunderstorms are producing modest rain amounts. This will be
something to watch later today if we get stronger storms and
either training or multiple rounds of rain in a short amount of
time.

SPC mesoanalysis page shows a swath of 850mb warm air advection
across most of western North Dakota in line with the current
convection, with a low-level jet analyzed over this same region.
We expect this to continue pushing northeast through the
morning, with a break in precipitation before the surface low
and attendant cold front currently analyzed in central Montana
move closer. CAMs are still in relatively good agreement on
showers and storms continuing to develop in the warm air
advection regime, in addition to along and potentially behind
the front as it moves through. Updated POPs a bit in line with
current trends otherwise going forecast looks good for now.

&&

.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 /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 646 AM CDT Mon Jun 10 2024

Showers and thunderstorms are ongoing across much of western and
into south central North Dakota, with multiple rounds of
precipitation expected across most of the area today as a storm
system moves through. There will likely be some breaks between
precipitation at western and central terminals, but tried to
time out storms as best as possible. KJMS will be the last
terminal impacted, most likely not until late this afternoon.
Some strong to severe thunderstorms are possible across portions
of western and south central North Dakota during the day today.
MVFR ceilings are likely across northwest and north central
North Dakota this afternoon and evening. Additionally, MVFR
conditions are possible around heavier showers and
thunderstorms. Southeast winds will be breezy through the day
today, sustained up to 20 knots, before switching to
northwesterly from west to east this afternoon through tonight
as a front moves through.

&&

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

&&

$$

UPDATE...Telken
DISCUSSION...Jones
AVIATION...Jones