South Prairie North Dakota Weather Forecast Discussion

665
FXUS63 KBIS 111207
AFDBIS
Area Forecast Discussion
National Weather Service Bismarck ND
707 AM CDT Sat Oct 11 2025
.KEY MESSAGES...
- Well above normal temperatures today through tonight. Highs
  this afternoon could approach 80 in far western North Dakota.
- Strong southerly winds today, then strong west to northwest
  winds Sunday through Sunday night.
- Medium to high chances for rain across central and eastern
  North Dakota this evening through tonight.
- Rain expected across much of northwest North Dakota Sunday
  morning through Sunday evening. The rain could mix with or
  change over to snow late Sunday afternoon and evening. The
  probability of accumulating snow is low.
- Cooler for the first half of next week, with highs in the 40s
  and 50s and lows in the 20s and 30s. Medium chances for rain
  return mid to late week.
&&
.UPDATE...
Issued at 706 AM CDT Sat Oct 11 2025
A broad band of widely scattered light rain showers or sprinkles has
been progressing northeastward through the state since late last
night, and is now located from around Tioga to Devils Lake. This
very light rain will continue to move northeast and exit the
forecast area by late morning. Farther south, a strong low level jet
is initiating a meridional line of showers from just south of
Bismarck through the Missouri River Valley in South Dakota. CAMs
with an earlier initialization time had a better handle on what is
now being observed than the more recent suite. This activity may
continue to blossom and spread northeastward through the
morning.
&&
.DISCUSSION...
Issued at 517 AM CDT Sat Oct 11 2025
An upper level ridge axis is located from roughly Minnesota to Texas
early this morning. A downstream surface high pressure is shifting
over the Great Lakes, while an upstream closed upper low is spinning
into the Pacific Northwest. This upper low is embedded in a longwave
trough that is digging into northern California. Shortwave impulses
have been ejecting from the base of the trough since yesterday, and
one such piece of energy has sparked some high-based light rain
showers or sprinkles lifting northeast across western and central
North Dakota early this morning. Very little, if any measurable
rainfall is anticipated with this initial precipitation. Some models
are depicting a more organized area of showers developing from north
central South Dakota into southeast North Dakota later this morning
in response to increasing warm air advection, but confidence on
areal coverage is not high.
Western and central North Dakota will sit between the upper level
height ridge and low level thermal ridge axes by this afternoon, as
well as between the downstream surface high and a surface trough
deepening over eastern Montana. This will set the stage for an
unseasonably warm but windy day. High temperatures in far western
North Dakota, where winds will be relatively lightest, could
approach 80 degrees. Mid 60s to mid 70s are projected elsewhere.
South-southeast winds are forecast to reach sustained speeds around
20 to 30 mph this afternoon, with gusts as high as 40 mph. The
strongest winds today are favored between Lake Oahe and the James
River Valley.
A more potent shortwave that can be seen over Utah early this
morning is forecast to eject into the Northern Plains by this
evening. Model guidance has consolidated on this forcing bringing a
period of rain across central and eastern North Dakota this evening
through tonight, perhaps clipping the southwest upon entry into the
state. A few CAMs hint at embedded thunderstorms with this activity,
but MUCAPE is not projected to exceed more than a few hundred J/kg.
Western North Dakota could see some isolated showers this evening
into tonight, but for this time period they are forecast to lie in
between stronger forcing mechanisms. The surface trough is forecast
to shift into western North Dakota tonight, with the downstream
environment remaining breezy. Overnight temperatures across central
North Dakota could stay well into the 50s.
It has been well advertised that the base of the western CONUS
trough would kick into the Northern Plains on Sunday, and just prior
to doing so, induce surface cyclogenesis over southeast Montana.
Confidence on this evolution has shifted slightly, with the latest
ensemble data now trending more toward a more progressive system
with an open (but still quite potent) wave. The expectation for a
cold front surging east across the state has not changed, but the
timing has sped up. With this more likely earlier frontal passage,
wind gusts may not be as strong as previous forecast thinking.
Nevertheless, there is still a signal in deterministic data for
strong magnitudes of cold air advection and pressure rises with and
trailing the front, which could easily transfer mean mixing winds
around 30 to 35 kts to the surface. As the surface low wraps up over
southern Manitoba Sunday afternoon and evening, we still anticipate
a stronger surge of wind across northern parts of the state.
Ensembles are now favoring a slightly weaker momentum transfer
potential with this part of the system, but the mean BL winds are
still projected around 40 to 45 kts, and one lower membership
cluster (as well as the deterministic GFS) maintains +50 kts. Some
guidance is also now hinting at a stronger surge of wind through
southwest North Dakota during the late afternoon and early evening,
something that will have to be monitored as future model data arrive.
Confidence continues to increase that southwest and central North
Dakota will remain mostly dry on Sunday, with possible exceptions
being 1) showers along the cold front and 2) isolated, diurnally
driven convective showers in the cyclonic flow regime Sunday
afternoon. In the northwest though, we are still expecting 2
distinct rounds, or perhaps just one continuous round, of steady
precipitation early Sunday morning into Sunday evening. The initial
round early Sunday morning is projected to be driven by strong mid
level DCVA and intense upper level divergence from the left exit
region of an approaching jet. CAMs have been consistent in
pinpointing this as the highest, albeit still relatively low, chance
for a stronger thunderstorm in a very high shear but low CAPE
environment. There may be a break, or at least a scattering of
coverage, in the rain until the wrap-around deformation band begins
to take shape over northwest North Dakota during the afternoon. It
is clear that the timing of this precipitation has sped up, but so
too has the decrease in temperatures. While we still think there is
potential for snow during the late afternoon and early evening hours
before the precipitation lifts into Canada, the probability of
impacts has significantly lowered from previous forecast iterations.
The latest NBM only maintains a 20 to 30 percent chance of
accumulating snow, and less than a 20 percent chance for at least
one inch of snow.
The other story with this system will be the transition to much
colder temperatures. The earlier timing of the cold front is likely
to result in near-steady temperatures across most of the area from
Sunday morning through the afternoon, except falling temperatures in
the northwest from the mid and upper 40s in the morning to the mid
30s by evening. A widespread hard freeze is anticipated Sunday
night, with high chances for lows in the 20s across the west and
north central, and medium chances for 32 or colder south central.
High pressure is forecast to begin building into the region on
Monday, with afternoon highs only projected in the lower 40s to
lower 50s. Another night of widespread sub-freezing temperatures is
in the forecast for Monday night, with a greater likelihood farther
north.
The forecast for the rest of the upcoming week is focused on the
evolution of another deep western CONUS trough. There is now a low
chance that shortwave energy ejecting from this trough could bring
light rain to the region as early as Tuesday. The current model
cycle has then clearly shifted back to a wetter solution for mid to
late week as the deep trough approaches the Plains. Despite timing,
location, and QPF uncertainty for any precipitation in the upcoming
week, there is high confidence that temperatures will remain warm
enough to support only rain as a type. This is also reflected in an
emerging trend for a slight warm up from Tuesday through Thursday
that is depicted in the NBM temperatures distributions.
&&
.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/...
Issued at 706 AM CDT Sat Oct 11 2025
All terminals begin this forecast period with VFR conditions.
VFR is likely to prevail through at least this afternoon. Isolated
showers are expected across central and eastern North Dakota this
morning, but categorical restrictions are unlikely. Higher chances
for rain move into south central and eastern North Dakota this
evening, which may be accompanied by MVFR ceilings.
Strong southerly winds are expected for most areas through the
forecast period, especially across central North Dakota where gusts
to around 35 kts are possible this afternoon. Low level wind shear
will also impact much of central North Dakota through mid morning.
Later tonight, MVFR ceilings will become more likely across northern
North Dakota and down towards KJMS. More persistent rain is expected
to move into northwest North Dakota by early Sunday morning.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Hollan
DISCUSSION...Hollan
AVIATION...Hollan

NWS BIS Office Area Forecast Discussion