674
FXUS63 KBIS 050408
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
1008 PM CST Wed Dec 4 2024

.KEY MESSAGES...

- A cold night is on tap tonight with wind chills down to 25
  below zero. Temperatures will then increase through the
  weekend.

- Mainly dry conditions are expected Thursday through Saturday,
  with widespread low to medium chances (20 to 60 percent) for
  precipitation returning Sunday into early next week.

&&

.UPDATE...
Issued at 1001 PM CST Wed Dec 4 2024

Quiet weather remains over the area, though a little light snow
still looks like it could develop later tonight over southwest
North Dakota. Chances are low (20 percent), and any accumulation
would be minimal at best.

UPDATE Issued at 647 PM CST Wed Dec 4 2024

Winds continue to gradually diminish, and with that the end of
almost all blowing snow with only some patchy spots around the
Turtle Mountains. Therefore, have let Winter Weather Advisory
expire. Other than that, other change was for later tonight
adding some low snow chances over the southwest as a modest
short wave drops through and mid-level warm air advection starts
to develop.

UPDATE
Issued at 429 PM CST Wed Dec 4 2024

Have trimmed off another tier of counties on the western edge of
the Winter Weather Advisory, as winds have diminished some over
this area. With that said, can not rule out a little drifting
snow in spots as winds continue to gust in the 30 to 35 mph
range, but the threat for blowing snow has diminished.

&&

.DISCUSSION...
Issued at 202 PM CST Wed Dec 4 2024

Our main concern early on is the ongoing winter weather advisory in
effect until 6 PM for the Turtle Mountains area into the James River
Valley.

Latest observations have shown some improvement in visibilities
compared to this morning. However, we are still into the wind
advisory criteria and certainly not cancel a winter weather advisory
and issue a wind advisory for only a few hours. Most likely will let
the advisory ride through the afternoon. The next shift would be
able to cancel early if warranted. If we would do any cancellations,
it would again be the western tier counties.

Next in line is wind chill temperatures tonight and overnight lows
early Thursday morning. Wind chills currently bottom out around 25
below zero, which if this verifies, would be below Cold Advisory
criteria. Forecast lows early Thursday morning are expected to drop
below zero for many areas in northern and eastern portions of the
forecast area. The surface high pressure center behind the exiting
clipper system is quick moving but does propagate southeast across
the forecast area tonight and at 12 UTC Thursday is forecast to be
roughly along the ND/SD border between Bismarck and Aberdeen. This
is an excellent location for cold low temperatures over south
central ND, including Bismarck. A look at the RAP moisture profiles
shows there may be some lingering low level stratus over eastern ND
and possibly into the James River Valley. Mid level moisture (700mb)
has pushed into western ND, approaching the  Missouri River. There
may be a short window around 12 UTC, where temperatures would be
able to bottom out. This is roughly along and just east of the
Highway 83 corridor. A fresh and plentiful snowpack would have
really helped temperatures bottom out, but the warm
temperatures yesterday ate up a lot of our latest fresh snow.
Still think there is enough of a snowpack to help a little. How
quickly and efficiently the low clouds exit to the east and how
quickly the mid clouds approach from the west will be the
determining factor. We did use a blend of some of the cooler
guidance to lower temperatures a bit over central ND.

The approaching mid clouds from the west is due to a southerly
return flow and warm advection on the back side of the Arctic High.
Latest NBM guidance has backed off a bit with the PoPs over
western and into south central ND. Will keep some slight chance
pops for consistency but overall, the threat for snow amounts
greater than a trace to a few tenths seems limited. The latest
NBM probabilities of 24 snow amounts of a tenth of an inch or
more, ending at 18Z Thursday are highest over west central into
southwest ND and max out only around 30 percent.

Although we start off cold on Thursday morning, and we will likely
remain mostly in the teens over eastern portions of central ND, the
western half of ND is forecast to see high temperatures climb into
the 20s with some mid and even upper 30s possible in the far
southwest.

We remain in a northwest upper air pattern late in the work
week and into the weekend. Strong west coast upper level ridging
will result in building heights pushing into the northern
Plains. This will push most of the waves propagating through the
upper level ridge to the north and east of the forecast area.
In addition, NBM ensemble temperatures indicate rather
significant warm-up over the forecast area, from Thursday
through Saturday. Although these is some spread, in both the
forecast highs and lows, it`s not all that large (5 to 7
degrees). Currently it looks like a nice period of moderating
temperatures and mostly precipitation free, from Thursday
through Saturday. It may be a little breezy on Saturday, but our
current forecast high temperatures range form the mid 30s
around the Turtle Mountains, to the middle 50s in the southwest.


We do see increasing ensemble spread Sunday and early next week as
the western North America ridge breaks down, at least temporarily. A
northeast Pacific upper low moves onshore and brings widespread low
to medium (30% to 60%) chances of precipitation to all of western
and central ND (based on the latest NBM guidance). Currently,
although the precipitation looks to be widespread across the
forecast area in the late Sunday through early Tuesday
timeframe, the latest long range ensemble guidance is indicating
mainly light precipitation amounts. The probability of over an
inch of snow in a 24 hour period is maxed out at around 25 to 35
percent. We`ll see if this changes as head into the upcoming
weekend.

&&

.AVIATION /06Z TAFS THROUGH 06Z FRIDAY/...
Issued at 1001 PM CST Wed Dec 4 2024

Mainly quiet weather is expected, though localized light snow
may develop late tonight over southwest North Dakota. This may
result in a spot or two of MVFR visibility, but overall most
locations should remain VFR.

&&

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

&&

$$

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