860
FXUS63 KBIS 222004
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
304 PM CDT Sat Jun 22 2024

.KEY MESSAGES...

- Isolated to scattered showers and storms (20 to 50 percent
  chance) are expected this afternoon and into the early
  evening. A few storms could become strong to severe. Quarter
  size hail and 60 mph wins will be the primary hazard.

- The next round of isolated strong to severe thunderstorms may
  come Sunday night into Monday morning across the northwest and
  north central, followed by a more conditional severe weather
  threat in the afternoon across the east.

- Temperatures continue to warm through the weekend with the
  warmest day on Monday. Highs will range from the lower 80s to
  lower 90s. We will then cool slightly through the rest of the
  week (mainly upper 70s to upper 80s).

- Thunderstorm chances return mid to late week.

&&

.DISCUSSION...
Issued at 304 PM CDT Sat Jun 22 2024

An upper level shortwave continues to move off into Minnesota as
the parent trough moves overhead. A surface trough is currently
the focus for scattered shower development as noted on radar,
roughly along a line from Rolette county, down through Rugby,
eastern Sheridan and Burleigh counties and arcing back to the
east over McIntosh county to the South Dakota border.

SPC mesoanalysis does suggest the presence of 500 to 1000 J/kg
MLCAPE in place across all of western and central North Dakota
so these showers should continue to increase in coverage and
intensity as daytime heating increases. That being said, shear
is currently weak where activity is developing and it should
remain weak for the next few hours. Later this afternoon, we
could have some more isolated development across the west which
will have a similar instability environment, but much better
shear. SPC mesoanalysis trends suggests effective shear could
ramp up into the 35 to 45 knot range by the 22z to 01z time
frame. Thus, there may be a window for a few isolated strong to
severe storms later this afternoon and into the early evening
hours. Any storms that do become organized will likely weaken
quickly with the loss of daytime heating. We will continue to
advertise hail to the size of quarters and winds to 60 mph as
the primary threats, but larger hail may be possible if we can
get any sustained rotating updrafts. After showers and storms
fizzle, most of western and central North Dakota will see a
mostly clear to partly cloudy sky overnight with lows in the
50s.

Sunday will be dry for most of the day as an upper level ridge
axis moves overhead. This will mean warmer temperatures for all
of western and central North Dakota, with highs ranging from the
mid to upper 70s over Rolette county, to the upper 80s and maybe
even some lower 90s across the southwest. The ridge will then
start to flatten as the axis moves off to the east and a subtle
shortwave starts to skirt northwest part of the state by late
evening. While most of the forcing will remain north of the
International Border, there should be enough of a glancing blow
to lead to some showers and storms across the northwest and
eventually north central late Sunday evening and into the early
Monday morning hours. While the magnitude of strong to severe
thunderstorms is currently unclear, there will be favorable
parameters in place with MLCAPE ranging from 500 to 1500+ J/kg
and 40 to 50 knots of deep layer shear. If convection can tap
into the favorable shear, some organization can be expected,
probably in some sort of cluster or linear mode. For now, will
continue to advertise hail to the size of quarters and wind
gusts to 60 mph as the primary threats.

Monday looks like it may end up being the warmest day of the
forecast period for most with highs forecast to range from the
lower 80s northwest to the lower 90s across the southeast.
Monday could also see a conditional severe weather threat in the
afternoon. The parameter space may end up being impressive
across portions of the central and into the James River Valley.
Some models suggest an environment characterized by 2500 to 3500
J/kg MLCAPE and deep layer shear ranging from 40 to 50 knots.
That being said, confidence of seeing any storms is fairly low.
Capping should keep the warm sector free of convection through
the early to mid afternoon and most guidance suggests that a
surface cold front will already be out of the area to our east
before storms initiate. If these trends continue, it would not
be surprising to see Monday completely dry for western and
central North Dakota. Any western trend will need to be watched.

Tuesday is then a bit cooler behind the cold front with highs in
the mid 70s to mid 80s. Highs will be similar through the rest
of the week until maybe Friday when some cooler temperatures
potentially return. Various chances for showers and
thunderstorms return Wednesday night through the rest of the
week and into the weekend. CSU Machine Learning guidance
suggests at least low chances for some severe storms on Thursday
and Friday but we have a long ways to go before we get into
specifics that far out.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1214 PM CDT Sat Jun 22 2024

Rain will hang on at KJMS for the next hour or so before moving
out. Ceilings will also continue to improve from west to east
this afternoon, eventually giving way to VFR conditions at all
sites. That being said, expect at least a couple more hours of
IFR to MVFR ceilings at most sites before lifting. We are
expecting some isolated thunderstorms this afternoon and evening
across western and central North Dakota but too much uncertainty
exits at the moment to pinpoint the exact locations these storms
will track. Thus, will not include mention at any specific TAF
site at this time. If a stronger storm moves overhead, it will
have potential for some hail to the size of quarters and winds
up to 60 mph.

&&

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

&&

$$

DISCUSSION...ZH
AVIATION...ZH