Glen Ullin, North Dakota Weather Forecast Discussion

580
FXUS63 KBIS 140644
AFDBIS
Area Forecast Discussion
National Weather Service Bismarck ND
144 AM CDT Sun Sep 14 2025
.KEY MESSAGES...
- Several rounds of scattered showers and thunderstorms through
  the middle of next week.
- Isolated severe thunderstorms possible Sunday afternoon and
  evening, mainly across central North Dakota.
- Temperatures favored to remain near to above average through
  the middle of next week.
&&
.UPDATE...
Issued at 143 AM CDT Sun Sep 14 2025
At 130 AM CDT, the only showers across the area were moving north
through the Badlands, with occasional lightning detected. The main
concern for the overnight period will be whether low clouds build
down to the surface to produce dense fog. Already seeing some half
mile visibility along the western peripheries of the stratus
deck.
UPDATE
Issued at 1010 PM CDT Sat Sep 13 2025
Thunderstorm coverage has diminished this evening, but a few
storms continue to develop and move through western North Dakota
with the next wave making its way over the area. A few of the
CAMs have this noted, and continue to move these storms to the
north. Not expecting severe at this time, but cant rule out some
small hail.
UPDATE Issued at 653 PM CDT Sat Sep 13 2025
For early evening update, main concern continues to be
thunderstorms over northwest North Dakota. A line of storms
developed more or less from Watford City northward in an area of
elevated instability and plenty of low level moisture to deal
with. These storms continue to hold in place and even back-build
some, in some places over areas that already had heavy rain.
Therefore, a pair of flood advisories have been issued.
Otherwise, some scattered showers continue to lift through
various parts of the area.
&&
.DISCUSSION...
Issued at 253 PM CDT Sat Sep 13 2025
A deep upper trough continued to dig over the Rockies this
afternoon, with surface low pressure analyzed in southwest North
Dakota. A swath of mid-level warm air advection on the
northeast side of this low has supported showers and
thunderstorms across south central and southeast North Dakota
early this afternoon, with additional weak convection across the
northwest. In between these two areas, very isolated showers
have continually developed but have not persisted for very long,
and lightning activity has been overall low. Afternoon highs
will be in the upper 60s to mainly mid 70s, with widespread
cloud cover in place over the forecast area.
We are still mentioning isolated severe thunderstorms possible
this afternoon and evening, but thinking the overall likelihood
is pretty low. 18Z RAOB at Bismarck reveals a modest capping
inversion still in place, with only around 500 J/kg of buoyancy
and around 25 knots of bulk shear. Deterministic guidance has
instability increasing marginally this afternoon but similar
shear, and with how much cloud cover has been lingering around
with the scattered showers and thunderstorms, much additional
destabilization seems unlikely. The latest CSU machine learning
output has removed virtually all probabilities of severe weather
for this afternoon and evening, with only a small area of low
chances in eastern Montana. The primary hazard to be concerned
with for any thunderstorms would be heavy rainfall and localized
flooding potential, especially in any areas that have already
received heavy rain over the past day or two. After the current
showers and thunderstorms move through, there is relatively good
agreement on a modest break in precipitation chances through
much of this evening and the overnight hours, with the exception
of an isolated shower or storm here and there.
As the upper trough base tilts further into the central CONUS, a
more pronounced wave with an attendant closed low ejects north
early Sunday morning. High-res guidance is consistent in
bringing in showers and thunderstorms to the ND/SD state line
around sunrise, which is when blended POPs start to increase
more significantly. Expect widely scattered showers and
thunderstorms through the day and night Sunday, with the highest
chances across central North Dakota. We again have a mention of
isolated severe thunderstorms, but NSSL and CSU machine learning
guidance is even less convinced of tomorrow compared to today,
so overall low probability of seeing anything strong to severe.
There is a bit more agreement among ensemble clusters regarding
the synoptic pattern to start the work week, with a general
consensus of a longwave trough base extending from the Rockies
to northwest Minnesota on Monday. Another wave propagating
through will continue chances for showers and thunderstorms
through Monday and Monday evening, with a short-lived break
before additional precipitation chances continue through
midweek. There are some hints that an upper ridge that tries to
build to our west will get pinched off by a trough digging back
in from the east, eventually producing cyclonic flow across the
Dakotas for the back half of the work week. The main outcome
from this will be a cooling trend to get temperatures back
closer to normal, with highs from Thursday onward mainly in the
mid 60s to lower 70s. On and off precipitation chances linger
but are lower than the current pattern, with less moisture
present from the drier northwest flow aloft.
&&
.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 143 AM CDT Sun Sep 14 2025
IFR to LIFR ceilings are expected to spread across most of western
and central North Dakota through tonight. Visibility could also be
reduced to IFR/LIFR levels at many locations by fog/mist. Ceilings
are expected to improve to at least MVFR levels, but perhaps VFR,
Sunday afternoon. Central North Dakota could then see prevailing
MVFR ceilings return this evening.
Only a few isolated showers and thunderstorms are expected across
western and central North Dakota overnight into early Sunday
morning. Showers and embedded thunderstorms should then become more
widespread from south to north late Sunday morning through the
evening. The highest chances for rain are at KBIS during the late
morning and afternoon, and at KMOT during the late afternoon and
evening. MVFR to IFR visibility from rain can be expected at times,
and a few stronger storms could produce gusty winds. Otherwise,
winds should remain light and variable.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Hollan
DISCUSSION...Jones
AVIATION...Hollan

NWS BIS Office Area Forecast Discussion