599
FXUS63 KBIS 201150
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
650 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 this
  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 643 AM CDT Sun Apr 20 2025

Clear skies continue ovr all but the far northwest. No
significant changes to the forecast other than adding Sioux,
Morton and Grant counties to the near-critical fire weather
wording today. Latest bufkit soundings indicate stronger surface
winds may hang on a little longer than forecast this afternoon.
With lowest humidities forecast to be along and west of the
Missouri, decided to add these counties. Otherwise no
significant changes to the forecast.


&&

.DISCUSSION...
Issued at 420 AM CDT Sun Apr 20 2025

Early Sunday morning high pressure was situated over the Great
Lakes region with low pressure over southern Saskatchewan and a
weak cold front extending southwest into south central Montana.
This was producing a broad area of southeast surface flow across
the Dakotas. Aloft, an upper level ridge extended from the
Desert Southwest, northeast through the Northern Plains and into
the Hudson Bay region of Canada. A broad upper level trough
extended from the eastern Pacific into western Canada and the
Pacific Northwest.

Today, the aforementioned cold front from Saskatchewan into
Montana will progress slowly eastward into western North
Dakota. This may bring isolated to scattered showers to western
ND today. The northwest portion of the state will be the most
likely area to see a few hundredths, up to a tenth of an inch of
rain. Most of the Cams are not too impressive, but the HREF did
increase the probabilities of a tenth of an inch from around 30
percent yesterday afternoon to around 50-60 percent this
morning, over far northwest ND. Farther east, over portions of
southwest and much of central North Dakota, much drier air will
remain in place, with increasing south to southeast winds as you
head east of the Highway 83 corridor. The lowest humidities
look to be just ahead of the front from south central ND, along
and west of the Missouri River, northeast into the Turtle
Mountains area. Here the lowest humidities drop into the upper
teens to lower 20s. Farther east, over the James River Valley,
afternoon humidities are in the 20 to 25 percent range, but
winds are also stronger with sustained winds of 15 to 20 mph,
with gusts to around 30 mph. The area of overlap of stronger
winds and lower humidities hasn`t changed from yesterday, thus
will keep this same area of near critical fire weather
conditions this afternoon into early this evening.

Tonight is expected to be quiet as any precipitation in western
ND dissipates as it moves into drier air over the central
portion of the state. Temperatures are expected to be in the
lower 30s to lower 40s.

On Monday the western U.S trough tracks across the Northern
Rockies and into the northern High Plains. Monday should be
another seasonable to mild day with highs in the upper 50s to
upper 60s. Precipitation chances will be on the increase though
over western ND Monday afternoon. It still looks like there will
be a low probability for thunderstorms Monday afternoon into the
early evening over western North Dakota. However, the severe
potential remain low. There is a surface trough along the MT/ND
border Monday afternoon with an approaching mid level wave.
Bulk shear is moderate, but at this time instability looks to
be quite meager. CAMS that do go out this far do show some
convective elements along the MT/ND line Monday afternoon.

As for the rain chances Monday afternoon through Tuesday, little
has changed with with 70 to over 90 percent chances for precip
spreading across the forecast area Monday afternoon through
Monday night. On Tuesday an upper level low closes off over the
area and lifts north into Canada. Medium to high precipitation
chances (60 to 80) percent will remain north of the Highway 200
corridor, with low to medium chances (20 to 40) south of Highway
200. Mainly light precipitation amounts are expected Tuesday.
It is possible the a little snow could mix in with the rain
Tuesday night.

As for the total precipitation amounts with this system, NBM-
derived chances for at least a quarter of an inch range from
around 30 to 70 percent. There is around a 50 percent chance of
exceeding half an inch of rain along the Highway 83 corridor
from around Bismarck to Minot. These odds decrease slightly to
the west and more so to the southeast.

Tuesday looks to be the coldest and windiest day of the week.
Highs will struggle to reach the 50s across the north. The
strongest winds on Tuesday will be across the south with west to
northwest winds of 20 to 30 mph and gusts up to 45 mph.

Mostly dry conditions are expected Tuesday night into Wednesday
with another system potentially brushing the southern forecast
area Wednesday night into Thursday. Current NBM PoPs increase
to around around 30 percent south to 20 percent central and
north by Thursday, then diminish Thursday night. Temperatures
from mid to late in the week are expected to remain near normal
with highs in the 50s and 60s and low in the 30s.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 643 AM CDT Sun Apr 20 2025


VFR ceilings and visibilities are expected through the TAF
period. An area of rain associated with a surface trough 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 Prob30 at
KXWA as confidence of precip reaching KDIK is less than 30
percent. Breezy south winds are expected this 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 12Z Monday.

&&

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

&&

$$

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