291
FXUS63 KBIS 011133
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
633 AM CDT Sat Jun 1 2024

.KEY MESSAGES...

- Dry today, then chances for showers and thunderstorms tonight
  through the first half of next week. Near or slightly above
  average highs in the 70s and 80s through much of the work
  week.

- Isolated to scattered severe storms will be possible Sunday, with
  hail up to golf ball size, 60 mph winds, and a tornado or
  two.

&&

.UPDATE...
Issued at 629 AM CDT Sat Jun 1 2024

The upper level wave axis and surface trough axis have passed,
and so have the showers. The rest of the day will now be mostly
sunny under slightly high pressure and northwest flow.


&&

.DISCUSSION...
Issued at 420 AM CDT Sat Jun 1 2024

Currently light showers are moving through the eastern half of
the state, riding a surface trough and an upper level wave. The
surface trough is in the Devil`s Lake Basin and the upper wave
is in the north central. These showers should be east out of our
area by sunrise as the subsistence on the backside of the wave
moves over. With this, a mostly sunny day with highs in the 70s
is forecast today. Flow aloft will be mostly zonal today with a
warmer thermal ridge moving in ahead of a shortwave trough for
Sunday. As the wave opens up over the state, a slight chance of
showers and maybe thunderstorms are possible over the south
central tonight.


Isolated to Scattered Severe Storms Sunday:

A quick moving northern Rockies wave will move through Sunday,
with a surface low in southern South Dakota. This will also
carry a very warm 850mb layer over. The wave will also have a
lagging surface cold front moving west to east Sunday afternoon
and evening. With around 35kts of shear and 1500-2300 J/kg of
CAPE storms will likely first fire as scattered supercells
before all the convection lines up on the cold front. The shear
vector is parallel to the front, supporting a line of storms as
the main storm mode. Another concern will be a tornado or two.
Helicity values are well over 150 m2/s2, depicting the chance of
a quick tornado along the line or right away when the isolated
storms form. The CAMs have these isolated cells forming in the
west late morning, then forming into a line in the afternoon
closer to the Missouri River when more CAPE is available along
the front. They should all move east and out by sunset.

SPC has a marginal risk from around Highway 85 to the Missouri
River about, and a slight from there east. For now we are
messaging golf ball sized hail for the supercell potential early
on, then 60 mph winds and a tornado or 2.

After Sunday, the flow goes back southwest as another bigger
trough forms in the Pacific Northwest. A very warm thermal ridge
moves in Monday ahead of this. Highs Monday will be actually
above average for once with highs in the upper 70s and lower
80s. Tuesday as the wave moves in, the chances of showers and
thunderstorms increase. The backside of the wave will bring in
cooler temperatures, back below average. A surface low with this
will tighten the pressure gradient making the southwest breezy,
but sub-advisory level Tuesday. The rest of the week we will be
under a large omega looking ridge with another low forming in
the ocean. Temperatures should be around average in the low to
mid 70s with the southwest maybe around 80.

&&

.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/...
Issued at 629 AM CDT Sat Jun 1 2024

VFR through the period. Mostly clear skies and winds from the
west today. Slight chance of showers tonight, put vcsh where
confidence is higher for now. Winds will shift to the south
overnight.

&&

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

&&

$$

UPDATE...Smith
DISCUSSION...Smith
AVIATION...Smith