483
FXUS63 KBIS 200515
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
1215 AM CDT Sun Apr 20 2025

.KEY MESSAGES...

- Near-critical fire weather conditions from the Missouri River
  south of Lake Sakakawea to the James River Valley Sunday
  afternoon through early evening.

- High chances (70 to 90 percent) for rain Monday afternoon
  through Tuesday, with low to medium chances for exceeding
  half an inch.

&&

.UPDATE...
Issued at 1152 PM CDT Sat Apr 19 2025

Clear skies across all but the far northwest early in the
overnight period. Besides some increasing high clouds here
through early Sunday morning, it will remain clear and cool. No
updates planned.

UPDATE
Issued at 907 PM CDT Sat Apr 19 2025

Winds have decreased a bit across the forecast area with the
vast majority of observations now under 15 mph, and around half
under 10 mph. In addition, relative humidity values have
recovered to more than 20 percent, with most locations in excess
of 30 percent. Therefore, as planned, have ended mentions of
near-critical fire weather conditions in the far northwest for
this evening. Otherwise, the forecast remains on track.

UPDATE
Issued at 646 PM CDT Sat Apr 19 2025

Southerly winds winds around 10 to 15 mph with gusts up to 25
mph, along with clear skies, persist across the area. Sustained
winds and direction should remain relatively stable for most
locations through the night, though gusts may diminish in some
areas as the sun sets. All in all, the ongoing forecast remains
on track.

&&

.DISCUSSION...
Issued at 242 PM CDT Sat Apr 19 2025

A positively-tilted synoptic wave pattern covers North America this
afternoon, with a trough axis from Hudson Bay to the Desert
Southwest and an upstream ridge axis from the California coast to
the Canadian prairie provinces. Surface flow over the Northern
Plains is southerly in response to low pressure over southern
Saskatchewan. Aside from a few cumulus clouds across south central
and southeast North Dakota, the sky remains clear this afternoon
with temperatures rising into the 50s and lower 60s. While most
areas are currently seeing wind speeds around 10 to 15 mph, the
northwest corner of the state is forecast to increase to sustained
winds around 20 mph with gusts up to 30 mph late this afternoon.
This smaller area of enhanced winds combined with humidity forecast
to fall to around 15 percent will create near-critical fire weather
conditions across Divide, Williams, and into Burke Counties. This
concern will end around sunset time. A light southerly breeze will
continue through tonight. The lightest overnight winds are expected
along the favored corridor for cold low temperatures from Beulah-
Hazen to Hettinger, where the forecast for tonight is in the mid to
upper 20s. Elsewhere, expecting lower to mid 30s for lows tonight.

On Sunday, an approaching mid level shortwave combined with a
surface trough attendant to the Saskatchewan low will bring medium
chances for light rain into western North Dakota throughout the day.
A very dry low level layer of air could be a prohibiting factor in
both rain reaching the ground and amounts overall, especially
earlier in the day prior to the column becoming more fully
saturated. High resolution guidance carries higher QPF threshold
probabilities than global ensembles, but the HREF probability of
exceeding just a tenth of an inch is still mostly less than 30
percent. To the east of these features, a warm and dry southerly
flow will prevail, with high temperatures forecast to reach the mid
to upper 60s. Breezy conditions are also expected in the southeast
quadrant of our forecast area, generally along and east of Highway
83 and along and south of Highway 200, with sustained winds around
20 to 25 mph and gusts to around 30 mph. This area is also forecast
to see humidity fall into the 20 to 25 percent range Sunday
afternoon, and these lower values do also extend westward beyond the
area of stronger winds. Near-critical fire weather conditions are
expected Sunday afternoon through early evening in the
aforementioned areas of strongest winds.

A transitory upper ridge is forecast to be located over the Northern
Plains early Monday between a downstream shortwave that originates
from the base of the current Desert Southwest trough and an upstream
shortwave that is forecast to land on the Pacific Northwest coast on
Sunday. Ensembles are becoming more unified in a dry start to the
day Monday, followed by increasing chances for rain from west to
east during the afternoon through the night as the upstream wave
digs into the region. With precipitation and associated clouds not
reaching central parts of the state prior to peak heating, the high
temperature forecast for Monday is similar to Sunday with mid and
upper 50s northwest to mid and upper 60s central and east. The
chance of rain at any given location across the western two thirds
of the state is maximized from 70 to as high as 90 percent. There
are also signals in ensemble guidance for an appreciable amount of
moisture with this system, with NBM-derived chances for at least a
quarter of an inch around 40 to 70 percent. There is even at least a
50 percent chance of exceeding half an inch of rain from areas
around Bismarck to Minot, with these odds decreasing slightly to the
west and much more so to the southeast. There is a low probability
for a few thunderstorms in the southwest Monday afternoon and
evening, but there does not appear to be enough CAPE to support
strong to severe convection. There is also a very low chance that
snow could briefly mix with rain in northwest parts of the state
late Monday night into early Tuesday morning. Little to no
accumulation or impacts are expected at this time.

The low pressure system responsible for the high rain chances Monday
night is forecast to lift northeast into southern Manitoba on
Tuesday. Northern parts of the state could see rain continue through
the day (50 to 70 percent chance per NBM), and southern North Dakota
also maintains lower chances for showers through the day Tuesday on
account of westerly cyclonic flow aloft. Tuesday is also looking to
be the windiest day of the week, with west-northwest winds forecast
around 20 to near 30 mph and gusts as high as 35 to 40 mph. All
locations are expected to see cooler temperatures on Tuesday, with
forecast highs ranging from the upper 40s northwest to lower 60s
southeast.

Longer range guidance generally projects an active quasi-zonal flow
pattern from the middle to end of next week. After a dry Wednesday,
the NBM generally maintains a 20 to 30 percent chance of rain
through the remainder of the extended forecast period. The
temperature outlook projected by the NBM from mid to late week is
near average for late April, with highs in the 50s and 60s and lows
in the 30s.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 1152 PM CDT Sat Apr 19 2025

VFR ceilings and visibilities are expected through the early
overnight hours across western and central North Dakota. Sunday
morning an area of light rain associated with a weak cold front
is forecast to push into western ND with lower VFR ceilings
pushing as far as KXWA and KDIK. It`s possible a brief period of
MVFR ceiling/vsby could be reached in an isolated to scattered
rain shower. This activity is forecast to dissipate before
reaching KMOT and KBIS, and will only include a mention of -RA
at KXWA as confidence of precip reaching KDIK is less than 30
percent. Southerly surface flow tonight across western and
central ND. Stronger winds aloft around KJMS will necessitate a
mention of LLWS 06-12 UTC. Breezy south winds are expected
Sunday afternoon over south central ND into the James River
Valley. Surface flow will turn north to northwest today over
western and north central ND, but should remain southerly at
KBIS and KJMS through 06Z Monday.

&&

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

&&

$$

UPDATE...TWH
DISCUSSION...Hollan
AVIATION...TWH