306 
FXUS63 KBIS 091356
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
856 AM CDT Sat Apr 9 2022

.UPDATE...
Issued at 854 AM CDT Sat Apr 9 2022

For this update, just tweaked precipitation chances across the
northwest as some stronger radar echoes have developed across far
northeastern Montana. Precipitation has been observed under some
of these echoes, so expanded the mention of isolated showers
across the northwest as they continue to make their way into North
Dakota.

UPDATE Issued at 620 AM CDT Sat Apr 9 2022

A dry cold front was about to move into western North Dakota at 
11 UTC this morning. Winds will shift to the west northwest from
west to east through the day. Made some minor adjustments to sky
cover based on latest satellite imagery. 

&&

.SHORT TERM...(Today and tonight)
Issued at 209 AM CDT Sat Apr 9 2022

Strong west to northwest winds behind a cold front with fire
weather concerns highlight the short term forecast.

Currently, a cold front was situated over eastern Montana. The
cold front will move to the ND border around 12 UTC and then into
central ND around midday and into the JRV by late afternoon/early
evening. Currently we are carrying a slight chance of showers 
over the northwest, behind the front. Elsewhere you might see a 
sprinkle or some virga, but the main impacts will be the west to
northwest winds and much drier air filtering into the state 
behind the front. We will continue to mention

The main area for concern will be western ND as there is a push of
higher humidity directly behind the cold front before the drier
air works in behind. Think this area will see the highest
potential for sustained 20 mph winds with 20 percent RH this
afternoon, and most likely mid to late afternoon. 

Once winds diminish tonight, it looks to be quiet with lows in the
mid 20s to mid 30s.

.LONG TERM...(Sunday through Friday)
Issued at 209 AM CDT Sat Apr 9 2022

A mid to late week storm system will be the focus for the long
term period.

The weak dry cold front associated with a Canadian low pressure 
system that moves through the forecast area today is the first 
signal of a significant change in our weather pattern. A building 
upper ridge over the Gulf of Alaska and the aforementioned upper 
low over western Canada will help to develop a broad upper level 
trough over the western and central U.S. by early next week. 

The lead shortwave coming off the Pacific will produce an area of
rain and snow over southeast North Dakota very late tonight and
into Sunday. This area has trended a little farther east and
lighter in qpf, thus at this time impacts look to be minimal over
the southern James River Valley. This will be followed by some
isolated to scattered diurnally driven mainly rain showers over 
the forecast area Sunday afternoon within a cyclonic flow aloft.
Highs Sunday will be in the mid 40s to mid 50s. 

A much stronger wave moves onto the Pacific Northwest coast late
Sunday night into Monday. We could see a passing shower on Monday
but overall this should be a quiet day as the Canadian low tracks
off to the east and the western U.S wave digs south, with upper 
level ridging over the forecast area Monday afternoon and evening.
While we are quiet here Monday, a Colorado low develops in the 
lee of the central Rockies in the Monday and then pushes out into 
the Central Plains on Tuesday. Back here in the Northern Plains we
will see the initial wave of precipitation ahead of the upper low
that moves into the Northern rockies. 

From here, we'll get a little less specific as uncertainties
increase in specifics. However we will focus more on the impacts. 

Again, there are still a lot of uncertainties, but it does look
like a the upper low moves into the Dakotas as the surface low
lifts from the Central Plains into Minnesota. In general, the GFS
and GEFS ensembles are more progressive in swinging the system
through the forecast area, while the EC/CMC are slower. However,
this far out, it is really a moot point, so lest looks at some
impacts. 

From the ensembles, the probability of a half inch of liquid qpf
from 12Z Tuesday through 12Z Friday is greater than 50 percent
across the entire CWA. The ECMWF ensemble is nearly 100 percent
while the GEFS has a thinner band of 100 percent from southwest ND
into northeast ND. The probability of an inch or greater total qpf
is above 50 percent during the same timeframe over a good portion
of the forecast area. Moisture wise, this looks to be quite
beneficial for us. 

As we mentioned yesterday, critical temperatures with this system
look to be cold, with a good possibility of more snow than rain, 
especially as we get beyond Tuesday daytime over most of the 
forecast area. Warmer temperatures may hold on a little longer 
over the far south central and into the James River Valley Tuesday 
night. At this time it appears that thereafter, there will be 
enough cold air pulled into the system that precipitation type 
will be all snow. The latest NBM4.1 ensembles are showing a high
probability (greater than 70 percent) of at least 8 inches of snow
over most of the forecast area. This could produce significant
impacts to travel.

It appears the main differences between the GFS/GEFS and the
EC/CMC deterministic and ensembles models is the extent to which
the system wraps up after Tuesday night. The EC/CMC would likely
yield higher precipitation amounts as well as an extended period
of strong winds through Thursday and possibly into Friday.

From the latest from the cluster analysis realm, unfortunately 
the Day 4 period was unavailable at press time so we'll have to do
with what we have. We think the main takeaway compared to 
yesterday is that on Day 3, ending 00Z Wednesday, there appears to
be some trending of the EC/CMC towards the GEFS ensemble solution
in that the EC/CMC do not track the upper level system as far 
south as they did yesterday, and they also have more of a double 
barrel look with a second low trailing behind. The EC/CMC grouping
still remains relatively high (above 50 percent) while the GEFS 
favored cluster (53%) is more of an elongated trough from the 
Pacific Northwest into the Northern High Plains. By Day 5 (00Z 
Friday) the GEFS favored grouping (77%) has lifted through North 
Dakota. The EC/CMC favored solution shows the upper low also east 
of the area, in the upper Great Lakes region but much deeper than 
the GEFS, and also there is some support from both ensembles for 
strong and an even slower solution, which would keep wind and 
precip lingering even longer over the area. There are still 
uncertainties in both the timing/placement as well as the strength
of this strong system. One thing that hasn't changed is that both
solutions do still bring a significant swath of precipitation 
across the forecast area.

For messaging today, we will introduce a graphic depicting the
risk of 8 or more inches of snow from Tuesday through Thursday
night (72 hours), indicating our continued high confidence in a 
significant storm system. Yet we can not emphasize enough the lack
of specifics this far out. Whether you end up being significantly
impacted by this system, or not, you have a few days to prepare 
before a potentially very impactful storm system beginning next 
Tuesday.

&&

.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
Issued at 620 AM CDT Sat Apr 9 2022

LLWS expected at KMOT and KBIS through around 15Z this morning.

VFR conditions are expected through the 12Z TAF period. A 
southerly flow across the forecast area at 12 UTC will shift 
westerly from west to east through the forecast period, beginning 
around 12-14 UTC at KXWA and KDIK. Through around 16 UTC this 
morning strong south winds aloft will be observed over central ND 
with light surface winds. We have added LLWS at around 1300 ft at 
KBIS and KMOT for this period. Strong west to northwest winds will
develop at KDIK and KXWA, and possibly into KMOT this afternoon 
into early evening.

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...ZH
SHORT TERM...TWH
LONG TERM...TWH
AVIATION...TWH