351
FXUS63 KBIS 311442
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
942 AM CDT Sun May 31 2026

.KEY MESSAGES...

- Widespread showers with scattered thunderstorms continue today
  into tonight.

- Marginal (level 1 out of 5) severe weather threat this
  afternoon and evening over much of south central North
  Dakota.

- Medium to high precipitation chances continue in the forecast
  from Monday night through Wednesday. Low to medium chances
  through the remainder of the week.

- Marginal (level 1 out of 5) to Slight risk (level 2 out of 5)
  of severe weather on Tuesday.

&&

.UPDATE...
Issued at 942 AM CDT Sun May 31 2026

Showers have become quite isolated this morning, with some
clearing observed in the west. The next round of showers and
thunderstorms will develop this afternoon and push spread
eastward through the evening. Made some minor adjustments to
PoPs based on the latest radar trends.

UPDATE
Issued at 641 AM CDT Sun May 31 2026

Going forecast remains on track with only minimal changes needed
at this time.

&&

.DISCUSSION...
Issued at 321 AM CDT Sun May 31 2026

Current surface analysis places low stretching from eastern
Montana into western South Dakota, with high over the Great
Lakes. Upper level analysis places trough stretching through
Montana into Wyoming, with ridge through the Midwest. Over our
area, areas of showers continue to lift northward ahead of the
aforementioned upper through, with thunderstorms now mainly
confined to the southern James River Valley where the higher
instability (~500 J/Kg) is now noted.

For today, aforementioned upper trough closes off over Montana
with a variety of short waves continuing to wrap around bringing
continued rain showers to the area. Instability will be on the
increase this afternoon, thus an increasing chance for
thunderstorms. Greatest instability (~1000-1500 J/Kg) looks to
reside mainly over southwest into south central North Dakota
later this afternoon into this evening. Although deep layer
shear appears to still be a bit on the low side (though higher
than yesterday), still think the potential for a few marginally
severe storms exists with hail up to one inch in diameter and
wind gusts to 60 mph. A frontal boundary pulling into the area
Sunday night into early Monday will sustain additional
precipitation chances.

Monday may see a brief break in precipitation over most
locations except possibly north central North Dakota where
aforementioned front stalls out. As we go through Monday,
aforementioned Montana low wraps itself northward and even
retrogrades a bit over southern Saskatchewan towards the Alberta
border. The next in a series of waves push into the area late
Monday, with increasing precipitation chances gradually sliding
through our area through late Tuesday, even lingering into
Wednesday. NBM probabilities of seeing over an inch of
additional precipitation with this system have gone up a bit,
now at about 20 to 40 percent for a notable portion of western
North Dakota. In addition, there will be a severe threat on
Tuesday as instability will be on the increase later in the day
with 0-6km shear around 35 to 45 kts. Thereafter the flow
pattern remains generally westerly and active, bringing
continued low to medium precipitation chances to close out the
work week.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 641 AM CDT Sun May 31 2026

Periods of rain showers will continue moving through the area
through this evening before gradually dissipating from southwest
to northeast late tonight. Mainly MVFR ceilings are forecast,
though there will be a period of IFR ceilings over various
locations this morning, and again over the James River Valley
late tonight. Periods of thunderstorms will also be in the mix
through the forecast period, mainly addressed with separate
PROB30 groups.

&&

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

&&

$$

UPDATE...Anglin
DISCUSSION...JJS
AVIATION...JJS