393
FXUS63 KBIS 260239
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
939 PM CDT Fri Apr 25 2025

.KEY MESSAGES...

- Near normal temperatures on Saturday, followed by well above
  normal on Sunday.

- Low to medium chances (20 to 40 percent) for hit or miss rain
  showers on Saturday.

- Medium to high chances (50 to 90 percent) of rain across most
  of western and central North Dakota late Sunday through
  Monday night. Low to medium chances (20 to 40 percent)
  northwest and north central.

- Low to medium chances for thunderstorms Sunday evening through
  Monday, mainly across the southern half of the state. Isolated
  strong to severe storms possible Sunday evening.

- Breezy to windy conditions at times Saturday through Monday.

&&

.UPDATE...
Issued at 938 PM CDT Fri Apr 25 2025

Only change to the forecast was to lower sky cover this evening.
Otherwise no changes were needed.

UPDATE
Issued at 559 PM CDT Fri Apr 25 2025

No significant changes to the forecast needed early this
evening. Generally light winds and clear to partly cloudy skies.
Clouds will be on the increase though late tonight.

&&

.DISCUSSION...
Issued at 258 PM CDT Fri Apr 25 2025

It`s a beautiful afternoon across western and central North
Dakota this Friday with generally light winds and plenty of
sunshine. Today`s temperatures are near to slightly above normal
with highs ranging from the upper 50s to mid 60s. Tonight`s
lows are forecast to be in the mid 30s to lower 40s.

Clouds will be on the increase overnight across the south,
spreading north through the day on Saturday as we transition
back into southwest flow aloft and moisture return starts to
kick in. A weak embedded shortwave will move across the state
from southwest to northeast through the day on Saturday, leading
to some hit or miss showers (20 to 40 percent). RAP soundings
suggest that most of the instability will remain south of the
state, but we could see some MUCAPE values around 100 to 200
J/kg along the South Dakota border across the far south central
and southeast. Thus, a rumble of thunder or two here cannot be
completely ruled out, but the probability is low at the moment.

With the increasing cloud cover and showers, temperatures on
Saturday are forecast to be just a touch cooler, with highs in
the mid 50s to lower 60s. Additionally, a tightening pressure
gradient and steep low-level lapse rates may lead to some
breezy/windy conditions (winds out of the south southeast).
While widespread cloud cover and warm air advection may limit
mixing to some extent, the NAEFS does continue to hint at
anomalously strong 850mb meridional flow for this time of year.
Thus, we could see some sporadic stronger gusts (up to 45 mph)
at times through the day, especially under any of the hit or
miss showers that are forecast to move across the state.

We will remain in southwest flow aloft on Sunday but neutral to
slightly rising heights are forecast, so most of the day will
remain dry as the atmosphere remains capped. Cloudy conditions
are likely to hang on across the central and east but we may
clear out some in the west. Breezy conditions will also move off
to eastern portions of the forecast area, in and around the
James River Valley. Temperatures will be well above normal on
Sunday with NBM highs ranging from the mid to upper 60s over the
Turtle Mountains, to the mid to upper 70s across the southwest.
As we approach Sunday evening, a western CONUS longwave trough
will start to nudge closer. Subsequently, we will also start to
see some mid-level height falls across western North Dakota as a
surface low deepens somewhere over eastern Wyoming or western
South Dakota/Nebraska. Showers and thunderstorms may be ongoing
over southeast Montana and northwest South Dakota and this
activity should start to move in after 00z Monday along a cold
front. New development is also likely to spread north northeast
across the state from the southwest and south central in the
evening and into the overnight hours, becoming widespread
statewide with medium to high chances (50 to 90 percent). The
one area that may not see much activity will be the northwest
and portions of the north central.

Regarding the strong to severe thunderstorm potential,
confidence has decreased a little bit. The highest probabilities
in the CSU Machine Learning guidance continue to dip a little
bit further south and the EFI has also backed off a bit on the
anomalous CAPE signal. Some scenarios continue to suggest MUCAPE
values in the 700 to 1500 J/kg across portions of the south but
some scenarios keep the best instability limited to the far
southwest and portions of the far south central. Either way,
deep layer shear should be sufficient for organized convection
and some risk of marginally severe hail or severe wind gusts
seems reasonable through around 06z Monday or so. Widespread
showers and embedded thunderstorms will continue through Monday
night (thunderstorms chances will be diminishing to the
southeast through the day on Monday). It is looking more and
more likely that we will see some widespread beneficial rainfall
totals Sunday evening through Monday night. NBM probabilities
(for 48-hour rainfall) now suggest medium to high chances (50
to 90 percent) for a half inch of rain or more along and south
of a line from southern Golden Valley county, northeast through
far western McLean county, and up to the greater Devils Lake
Basin. The highest probabilities will be across the south
central and southeast with the lowest probabilities northwest
and north central. Increasing the threshold to one inch and we
still see much of the same area ranging from 40 to 70 percent.
Due to the convective nature, some in the higher probability
areas may not see near as much as others and some may see
amounts even higher. These details will likely not present
themselves until the showers and storms have already developed.
Finally, it will be windy and cooler behind the front on Monday
as strong cold air advection overlaps strong pressure rises and
steep low-level lapse rates. Strong northerly winds to around
30 mph with gusts to 45 mph will be possible, with the strongest
winds favored over the southeast. Highs on Monday will range
from the lower 50s northwest, to the low to mid 60s southeast.

Rain will move out to the southeast Monday night, giving way to
a mostly dry Tuesday and warmer temperatures west as we
transition into zonal flow aloft. Highs will be in the lower 50s
east, to the lower 60s west. A weak shortwave may then move
through Tuesday night, leading to low to medium rain chances (20
to 40 percent) Tuesday night through Wednesday. West coast
ridge then pops up and nudges closer on Thursday, leading to a
gradual warmup through the rest of the week with highs mainly in
the 60s.

&&

.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 559 PM CDT Fri Apr 25 2025

VFR conditions are expected tonight, with low VFR ceilings
spreading south to north on Saturday. Areas of MVFR ceilings are
possible over western ND Saturday, but at this time kept the
only mention at KDIK, as lower ceilings will be more probable
over the southwest. Scattered showers will also spread from
south to north Saturday over central ND. Included a PROB30 at
KBIS and VCSH at KDIK and KMOT. Strong southeast winds will
develop Saturday across western and central North Dakota. By
Saturday afternoon most areas will see southeast winds 20 to 35
knots.

&&

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

&&

$$

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