761
FXUS63 KBIS 261917
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
217 PM CDT Sat Apr 26 2025

.KEY MESSAGES...

- Breezy to windy conditions at times today through Monday.

- Patchy fog possible west late tonight into Sunday morning.

- Showers and thunderstorms are expected Sunday evening through
  Monday for the southern half of the state, as well as in the
  east. There is a 30 to 50 percent chance of showers in the far
  north central and far northwest.

- Isolated to scattered severe storms possible Sunday evening
  into Sunday night for all but north central and northeastern
  North Dakota. The best chances are in the southwestern quarter
  of the state.

&&

.DISCUSSION...
Issued at 217 PM CDT Sat Apr 26 2025

Gusty winds will diminish this evening through tonight, though
will remain breezy over most areas that are along and east of
Highway 83, while also along and south of Highway 200. Breezy
conditions are expected to persist at those locations through
the day Sunday as well. Patchy fog may also develop over western
ND tonight into Sunday morning.

For Sunday, fairly broad surface low pressure will start out
along the High Plains before gradually organizing through the
day. By around 1 am CDT Sunday night, tightening low pressure is
progged to reach the vicinity of western Nebraska/South Dakota.
By 7 am CDT, it`s expected to become tightly wound over South
Dakota. What does this mean for severe weather? Well, as the low
approaches western Nebraska/South Dakota, southerly surface
flow will likely advect boundary layer dewpoints in excess of 50
degrees into at least southern North Dakota. This will enhance
instability with the HREF mean suggesting just over 1000 J/kg
of MUCAPE in southwestern North Dakota and lower amounts further
north and east. Similarly, the HREF mean brings around 30 to 35
kts of wind shear as well. This generally aligns well with
deterministic guidance, although the RAP brings much higher
instability to the southwest and south central near the ND/SD
border. Deterministic guidance is also closer to 35 to 45 kts of
0 to 6 km shear.

Despite instability that isn`t exactly the highest, 0 to 6 km
wind shear of 35 to 45 kts over the most unstable areas is
sufficient to produce severe weather. As such, the expectation
remains the possibility of isolated to scattered severe storms
producing hail up to the size of golf balls and winds up to 60
mph. In the area in the far southwest where higher low level
shear is forecast, an isolated tornado is possible Sunday
evening as well.

One thing to point out is that a stout cap should prevent
convection during the day Sunday. In addition, most models
suggest it never fully erodes for most of the area, except
potentially the far southwest with the isolated tornado threat.
Therefore it seems convection is favored to remain more
elevated. If that turns out to be the case, large hail will be
the primary threat over anything else.

Regardless of how the severe weather threat plays out Sunday
evening/night, widespread showers and thunderstorms are expected
Sunday night through the day Monday, especially in southern and
eastern portions of the state. For southern and eastern
portions of the state, probabilities of more than an inch of
rain are in excess of 50 percent. Even higher amounts are
possible on a localized basis, especially where any
thunderstorms develop. The severe weather threat will have
primarily moved off to the east by Monday. Though there remains
a low severe threat mainly Monday morning in the James River
Valley.

Behind this system, expect dry conditions Tuesday before a weak
shortwave passes through sometime Tuesday night through
Wednesday. This wave may produce a few more showers, though
indications are of relatively light rain with this system. Dry
conditions are then currently anticipated to finish out the
week. Temperatures Tuesday will range from the mid 50s to mid
60s, then increase into the 60s for Wednesday and Thursday.
Highs in the upper 60s and 70s are then possible to finish out
the week.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 116 PM CDT Sat Apr 26 2025

Gusty southeasterly winds are expected to persist this afternoon
before gradually diminishing this evening and overnight. While
winds in the west and north are expected to become light, breezy
conditions will likely persist in the south central through the
period. Light rain is occurring in the north central and parts
of the northwest, with returns over parts of the south central.
Returns over the south central are mostly virga at this time.
Overall, rain should gradually end through the afternoon,
although isolated showers may develop and linger in the James
River Valley through the night. MVFR ceilings are present in
parts of western North Dakota. These will gradually expand
eastward across the state tonight, becoming IFR at times, before
beginning to improve from west to east Sunday morning.

&&

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

&&

$$

DISCUSSION...Telken
AVIATION...Telken