339
FXUS63 KBIS 020810
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
310 AM CDT Sun Jun 2 2024

.KEY MESSAGES...

- Scattered severe thunderstorms today. Threats include hail up
  to the size of golf balls, damaging winds up to 60 mph, and a
  tornado or two possible.

- Chances for showers and thunderstorms continue through the
  first half of the week. Temperatures will be near to slightly
  above average, with highs in the lower 70s to lower 80s this
  week.

- Strong northwest winds are possible Tuesday through Thursday.

&&

.DISCUSSION...
Issued at 300 AM CDT Sun Jun 2 2024

Showers and thunderstorms have developed in the south central
and James River Valley. They formed in the region of the low
level jet (LLJ). A few of the storms have been strong but not
severe so far. The RAP and HRRR have the LLJ increasing in
strength before sunrise, so maybe a storm could go severe. There
is a lot of shear (55kts) and some MUCAPE around 500 J/kg at
this time.

Aloft the main wave is starting to move through eastern Montana,
with the surface low over southeast Montana. The main front is
also in Montana, moving east. The low level jet is forecast to
stay over western and central North Dakota 11z when the wave
moves further east and pushes it east. None of the CAMs have
this early morning convection so it is hard to use them for
timing later today, but there might be a break between this
convection and the main show. They still have storms firing in
Montana this morning and moving east, forming into a line around
Highway 85. With CAPE around 1000 J/kg this morning and low
level lapse rates over 7 C/km and the high shear, storms
initially could be supercells with golf ball sized hail. Then
when they form a line it should mainly be a wind threat. DCAPE
values aren`t over 1000 J/kg so we will be sticking to 60mph
winds. The low level helicity in the southwest this morning is
over 200 m2/s2 then it moves over to the east and values
increase around 400! So there is a possibility of quick spin up
tornadoes east of the Missouri River along the line, with the
highest chance looking south of the Interstate. Timing for this
looks to be late afternoon when the cold front develops the
line. SPC still has the slight risk in the east almost to the
river, and a marginal for this morning`s storms in the west.
The storms should move out by sunset.


The first half of the week will continue to be active. Another
upper low develops in the Northwest and moves across bringing
more chances for thunderstorms Monday afternoon and Tuesday.
The CSU machine learning forecast has a small hail threat in the
south central for Monday afternoon and overnight, otherwise the
severe risk is low. Monday will be the warmest day of the week
with highs in the 80s, then as the upper low leaves cooler air
filters back in. Highs will be back below average in the lower
70s for the mid week and in the mid 70s for the end of the week.
Average temperatures are in the mid 70s for the week of June.
Wednesday night is when the upper low will start to spin away,
putting us in cyclonic northwest flow, with a big ridge building
in the west over a Four Corners high. So the weather will be
quiet except for breezy northwest winds Tuesday through Thursday
with low pressures moving through. Wednesday we may need a wind
advisory in the southwest, we`ll see.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 300 AM CDT Sun Jun 2 2024

VFR conditions with chances of scattered storms now through the
period. Showers and thunderstorms have started to pop up north
of KBIS and around KJMS moving northeast. Winds are light but
could increase around 20kts when a cold front moves through
today, and changes winds to the north. Scattered severe
thunderstorms are likely late this morning through this evening.

&&

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

&&

$$

DISCUSSION...Smith
AVIATION...Smith