118
FXUS63 KBIS 070946
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
446 AM CDT Fri Jun 7 2024

.KEY MESSAGES...

- Scattered showers will move into the northwest (Williston
  area) this morning and advance east and south. This afternoon,
  along and east of a line from Hettinger to Garrison to Rugby,
  thunderstorms will be possible (as high as a 45 percent
  chance). Storms are expected to be below severe limits.

- Isolated showers (20 percent chance for rain) are forecast for
  Saturday, mainly north and east of Minot, and then on Sunday
  (20 percent) over central and eastern North Dakota.

- With high confidence it is expected to be cooler Sunday and
  Monday, the question is how much cooler, and then warmer for
  the middle of next week with high temperatures into the 80s.

&&

.DISCUSSION...
Issued at 430 AM CDT Fri Jun 7 2024

The surface analysis as of 4 AM showed weak high pressure
centered near Bismarck with a clear sky and winds that were
light, under 10 mph, and variable in direction. An inverted
trough extended north through eastern Montana. Low pressure
aloft was drifting south through central Saskatchewan with
pockets of energy (short waves) passing through the cyclonic
flow and heading toward the international border. Clouds in
association with the waves were both moving through southern
Saskatchewan and developing there. Radars showed an increase in
reflectivity north of Glasgow, Montana, with movement to the
east and south.

For today that first wave, and the cyclonic flow, will bring
increasing weak ascent of air parcels into the forecast area.
Guidance shows an abundance of 0-6km shear forecast to be over
the area but little in the way of CAPE, at least until later
this afternoon, and mostly along and south of Interstate 94.
Because of this CAMS bring showers into the northwest this
morning and intensify them as they move south and east, but only
slightly (the intensification). By intensification we mean
going from showers to thunderstorms. Looking at the HRRR fields,
a pocket of higher MUCAPE, on the order of 300 J/kg, is forecast
to move from southwest of Bismarck to south of Jamestown during
the late afternoon and into the evening. That would be the
highest chance and most likely location for a stronger storm. In
discussion with my shift partner we are concerned on one hand
of a storm there being able to produce some small hail, but on
the other hand, with strong shear, concern goes to the updrafts
not being able to gain much altitude before being sheared off.
We`ll have to watch to see how convective parameters change
through the short term to have more confidence in the risk of
small hail.

Another wave brushes the northeast on Saturday with chances for
showers, maybe a storm, mainly east and north of Minot. Then on
Sunday, the upper low advances into the state with cooler air
and shower chances in the cyclonic flow, over the central and
east.

Sunday should be the coolest day over the next seven with that
upper low over the state, followed by warming then through
at least Wednesday. The NBM 1D Viewer shows a wide range in
possible high temperature outcomes on Sunday, but all lower than
70. The question then becomes, cool Sunday, but just how cool,
especially north. 60s at this point would be a high
expectation, but lower, mid or upper 60s will need to be
determined. The Viewer then shows narrower ranges (higher
confidence) for high temperatures for the middle of the week,
basically 80 to 85. It does look like the 80s could be
accompanied by unsettled weather as the mean H5 ridge is broken
down every 24 hours or so by short wave troughs passing through
it, and bringing chances for rain. By Thursday the ridge could
be replaced by cyclonic flow troughing (cooler and more
unsettled).

&&

.AVIATION /12Z TAFS THROUGH 12Z SATURDAY/...
Issued at 430 AM CDT Fri Jun 7 2024

Surface high pressure near KBIS at 07/09Z will drift east and
allow an inverted trough to push in from Montana. Light and
variable winds to start the TAF valid period will shift
northwest and increase with the trough passage. Expect
scattered -SHRA at KXWA through 07/18Z to move east and south
and grow into isolated -TSRA around KBIS after 07/18Z and around
KJMS after 07/20Z. If a stronger storm is able to form it would
be south of Interstate 94. Showers and any storms will end at
KBIS by 08/02Z and at KJMS by 08/06Z.

&&

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

&&

$$

DISCUSSION...JPM
AVIATION...JPM