688
FXUS63 KBIS 121445
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
945 AM CDT Wed Jun 12 2024

.KEY MESSAGES...

- Highs today will be the warmest of the week for most of
  central North Dakota, including the James River Valley, with
  temperatures ranging from the upper 70s to upper 80s. Some
  locations in the southern James River Valley of ND could reach
  the low 90s.

- Isolated showers and a thunderstorm or two is possible today.
  Higher chances for more widespread precipitation, along with
  the potential for severe weather, is forecast Friday night
  through the weekend.

&&

.UPDATE...
Issued at 940 AM CDT Wed Jun 12 2024

Mostly clear skies continue across the area, with very weak
radar returns across the southwest and south central. Given how
dry the layer below these clouds are, its unlikely that any
precipitation is reaching the ground with these. As such, we`ve
reduced the PoPs for the next hour and a half across the south.
Winds are increasing slightly, but are generally increasing a
bit slower than anticipated, so we`ve decreased them a bit over
the next few hours as well. Otherwise, the forecast remains on
track.

.UPDATE...
Issued at 653 AM CDT Wed Jun 12 2024

Isolated showers continue across southwest and north central
North Dakota, with lightning activity significantly diminished
over the past hour. Our thought is that what convection did
manage to develop overnight is dying out as it outruns the low-
level jet. Meanwhile, the SPC mesoanalysis page shows cold air
advection spreading into western North Dakota, with a cold front
through our western tier of counties. Warm air advection is
widespread over eastern North Dakota into Minnesota where the
severe risk is much higher later today. A few isolated showers
have developed behind the front but in an area with cloud bases
around 10k feet. We expanded POPs with this update, especially
in southern North Dakota where an area of showers continues
slowly moving east. The most robust showers are in the far north
central, and should be out of the forecast area within the next
hour or so. Some of the latest high-res models have a low
chance of a thunderstorm or two returning to the Turtle
Mountains area this evening, so will have to see if this trend
continues.

&&

.DISCUSSION...
Issued at 354 AM CDT Wed Jun 12 2024

This morning, zonal flow aloft was in place over the Dakotas,
with a closed low and shallow shortwave trough moving through
Saskatchewan. An associated surface low was analyzed over south
central Saskatchewan, with showers and thunderstorms ongoing
around the low and to the south of the low along an ahead of a
cold front extending into eastern Montana. SPC mesoanalysis also
shows the nose of a low-level jet in eastern Montana where
convection is a bit more robust, with 850mb cold air advection
right behind this. Deterministic guidance is showing strong
bulk shear but very marginal instability this morning into the
early afternoon. We will keep the mention of isolated
thunderstorms primarily along our far northern and southern
counties, but with a lack of strong forcing aloft (especially
after the LLJ diminishes late morning), not expecting too
widespread of development.

The timing of the cold front passage will be critical to both
high temperatures and the severe weather potential today.
Current forecast highs range from the upper 70s in northwest
North Dakota, where the front moves through first, compared to
around 90 degrees in the southern James River Valley. If the
cold front slows up at all, the concern becomes higher
temperatures across the south central, and potential for strong
to severe thunderstorms in our far eastern counties. We continue
to carry a Marginal Risk (level 1 out of 5) in LaMoure and
Dickey Counties. There is a small window of favorable
conditions, with bulk shear around 40 knots and MLCAPE of
1000-2000 J/kg, but our current thinking is that the potential
in this area is low due to the front moving through early enough
in the afternoon. Breezy west to northwest winds will develop
behind the front, with the strongest winds of 20 to 25 mph in
northwest North Dakota.

An upper ridge begins building across the Northern Rockies
tonight into Thursday, with mostly dry conditions expected.
Various impulses are likely to move through the northwest flow,
with precipitation chances skimming the South Dakota border late
tonight, and a 30% chance for a few showers and thunderstorms in
the Turtle Mountains region on Thursday afternoon. In the post-
frontal regime we will see continued breezy northwest winds and
highs in the lower 70s to lower 80s.

The synoptic pattern in the long term is favored to be dominated
by southwest flow aloft, developing due to a deep closed low and
trough starting off the coast of British Columbia and sinking
south over the Northern Rockies to start next week.

As the ridge axis moves overhead on Friday, temperatures will
warm back up into the upper 70s to mid 80s. Meanwhile to our
south, a trough is progged to dig into the Four Corners region,
sending a deepening surface low into the central CONUS. Ahead of
this system, a shortwave is forecast to move through the mean
southwest flow over Montana, producing increasing chances of
showers and thunderstorms through the day Friday. Our far
southwest is included in the Day 3 Marginal Risk (level 1 out of
5), with sufficient buoyancy and bulk shear in a corridor
across western South Dakota into western North Dakota, although
there is uncertainty in how far north this environment will
extend. Machine learning probabilities have actually decreased
moderately for Friday, with only low probabilities for severe
hail across the forecast area.

There will likely be a break in precipitation at some point on Saturday
ahead of another embedded shortwave, with blended POPs
increasing again Saturday night before tapering off again on
Sunday. The main question then becomes when does a more
substantial trough move through and how long does this synoptic
pattern persist. Ensemble cluster analysis shows there are
still a few different scenarios regarding the evolution of this
pattern, but the commonality is the active pattern continuing
through the start of next work week. High temperatures are
generally near normal through Saturday before a cooling trend
begins, with below normal temperatures and highs bottoming out
on Monday before we begin a gradual warmup.

&&

.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...
Issued at 653 AM CDT Wed Jun 12 2024

VFR conditions expected through the TAF period. A few showers
are continuing across far southwest and north central North
Dakota this morning, but not expected to impact any terminals.
Winds will shift west to northwesterly as a cold front continues
moving through the area today, becoming breezy with sustained
winds up to 25 mph and gusts up to 35 mph. Winds will diminish
this evening.

&&

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

&&

$$

UPDATE...Besson
DISCUSSION...Jones
AVIATION...Jones