771
FXUS63 KBIS 091725
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
1225 PM CDT Sun Jun 9 2024

.KEY MESSAGES...

- High temperatures the next few days near normal for early
  June (normal is mid 70s). Above normal temperatures are
  expected with increasing confidence for Wednesday (80-85
  degrees).

- Widespread showers and thunderstorms (80 percent chance)
  expected Monday through Monday night. Isolated severe
  thunderstorms are possible across most of western and central
  North Dakota (level 1 out of 5 risk).

- Chance for showers and thunderstorms (30 percent) return late
  Tuesday night through Wednesday, before higher chances for
  precipitation at the end of the week.

&&

.UPDATE...
Issued at 1225 PM CDT Sun Jun 9 2024

The forecast remain on track at this time. High clouds linger
over the south central, while scattered mid level clouds have
spread over the west. Winds across the west have begun to turn
to the east northeast while as a weak high pressure center
continues to intrude into the northwest.

UPDATE
Issued at 830 AM CDT Sun Jun 9 2024

Other than minor edits to the sky grids in accordance to the
latest satellite trends, the forecast remains on track at this
time. The bank of scattered to broken mid level clouds that
will continue expanding across western and central North Dakota
through the early afternoon has begun to intrude into the west.
Winds remain light across the area.

UPDATE
Issued at 642 AM CDT Sun Jun 9 2024

Quiet weather continues this morning with surface high pressure
pushing into northwest North Dakota. A few midlevel clouds
continue over the south central and James River Valley, with
additional clouds slowly approaching from Montana. Keeping POPs
as is for this afternoon for now, with CAMs painting a similar
picture of isolated to scattered showers across southwest North
Dakota, with forecast soundings still showing cloud decks around
8-10k feet and a very dry layer below that. Tweaked sky cover
with this update otherwise no changes to the forecast needed.

&&

.DISCUSSION...
Issued at 414 AM CDT Sun Jun 9 2024

This morning, the synoptic pattern was characterized by
northwest flow aloft, with one closed low over southern
Saskatchewan and a second low over eastern Ontario. Broad
surface high pressure is building in over the Canadian Prairies,
while a weak stationary front is draped west-east across the
forecast area. Nighttime satellite imagery shows a swath of
mid-level clouds in this same area, and although there were some
light radar returns earlier in the night, these have all
diminished. Additional, more widespread cloud cover is visible
upstream.

Highs today will be a touch cooler than yesterday, with highs in
the upper 60s north to mid 50s south. We are carrying a mention
of isolated showers in the southwest this afternoon, with many
CAMs advertising precipitation chances as a vort max embedded in
northwest flow moves through. Similar to yesterday, cloud bases
are expected to be relatively high (around 9-10k feet), so
unless these showers become heavier we would expect the majority
of precipitation to remain as virga.

A brief upper ridge will build in overnight before a shortwave
trough approaches from Montana, with an attendant surface low
progged to deepen in Wyoming and move east. Strong low-level
warm air advection ahead of the low and trough axis is expected
before a cold front sweeps west to east across the forecast area
late Monday. With this warm advection and upper ascent, showers and
thunderstorms are expected to become widespread, with blended
POPs starting early Monday morning and increasing to 70 to 90%
Monday afternoon and evening. Most of western and central North
Dakota has been upgraded to a Marginal Risk (level 1 of 5) for
isolated severe thunderstorms on Monday, with a sliver of level
2 out of 5 (Slight Risk) in southern Bowman and Adams Counties.
One main area of concern regarding severe potential is how
early widespread cloud cover and scattered showers and
thunderstorms are expected to begin on Monday morning, and if
that will limit instability later in the day. For now,
deterministic guidance is advertising MLCAPE around 1000 J/kg
and strong 0-6km shear of 35-45 knots, with marginal mid level
lapse rates. Of note is rather high SRH, which is also shown in
CSU Machine Learning probabilities highlighting a low but non-
zero tornado threat across western North Dakota. However, we are
thinking the main threats are large hail up to the size of half
dollars and damaging wind gusts up to 60 mph.

Updated rainfall probabilities for Monday through Monday night
are similar to the previous shift, with generally a 30-50%
chance of exceeding at least 0.50" of rain across most of
western and central North Dakota, with the exception of the
southwest and southeast. The highest probabilities are currently
in the northwest part of the state. We will have to keep an eye
out for any areas that get multiple rounds of heavier
precipitation, with forecast PWATs at the high end of
climatology. Precipitation chances end early Tuesday morning as
the trough axis moves through, with a bit of a breeze in the
east but otherwise a pleasant day with highs in the 70s.

Rain chances return on Wednesday as an embedded shortwave moves
through zonal flow, while a surface low and associated front
moves through the Dakotas. Current model guidance has shifted
Wednesday`s severe potential slightly to the southeast, with a
quicker front and limited instability in our forecast area.
Timing changes could lead to a short-lived threat in the James
River Valley area but for now, the highest potential is outside
of our forecast area. Highs on Wednesday are forecast to be in
the upper 70s north to mid 80s south, although the timing of the
front could impact how warm we get.

Ensemble guidance is in good agreement on a southwest flow
pattern dominating the end of this week and into the weekend,
with a more active pattern expected. Blended POPs are already
showing widespread 30 to 40 percent chances of precipitation
late Friday night through Saturday night. NBM temperature ranges
keep highs near to slightly above average through the weekend,
in the lower 70s to lower 80s.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1225 PM CDT Sun Jun 9 2024

VRF conditions are expected to begin to 18Z TAF period. Isolated
showers are possible across the southwest, but there is not
sufficient confidence in it impacting any terminals at this
time. Winds will become breezy across the west this afternoon,
but will then diminish through the evening. Overnight into early
Monday, chances for showers will push into the west, first
impacting the terminals of KXWA and KDIK then spreading to KMOT
and KBIS by 18Z tomorrow. Beyond the end of the TAF period,
showers and eventually thunderstorms will become widespread,
with strong to severe thunderstorms possible Monday afternoon
and evening.

&&

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

&&

$$

UPDATE...Adam/Jones
DISCUSSION...Jones
AVIATION...Adam