687
FXUS63 KBIS 040016
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
716 PM CDT Thu Apr 3 2025

.KEY MESSAGES...

- A band of snow is forecast to move across much of western and
  central North Dakota this evening through Friday afternoon.
  The highest chances for at least 2 inches of snow (around 60
  to 80 percent) are focused over central North Dakota, where
  there is also a low to medium chance (30 to 60 percent) of at
  least 4 inches of snow.

- There is the potential for narrow bands of heavier snow. If
  they would develop, higher snow amounts up to around 7 inches
  would be possible.

- Temperatures will remain below normal through early next week.

- A transition to above normal temperatures is still expected next
  week, but it could be delayed until the second half of the
  week.

&&

.UPDATE...
Issued at 715 PM CDT Thu Apr 3 2025

Heavy snow was falling in the northwest and the radar is
starting to fill in towards Minot as well. Everywhere but the
far northwest, surface temperatures are above freezing so don`t
expect snow to accumulate just yet. In the southwest,
thunderstorms moved in from Montana with the potential of 50 mph
winds and pea size hail. Temperatures around the southwest and
central will not drop below freezing until after Midnight, this
is when most of the snow could accumulate.

Updated pops with a HRRR/NBM blend to get a better hold on the
timing of this line. Fgen still looks pretty strong across the
state through this system.


&&

.DISCUSSION...
Issued at 236 PM CDT Thu Apr 3 2025

Latest surface analysis shows low pressure over south central
Montana, with high pressure in the lee of the Northern Montana
Rockies. A warm front extends east from the Montana low, with a cold
front dropping slowly south through North Dakota. Latest radar shows
convection near the warm front in southeast Montana and light
stratiform rain showers over northeast Montana. In the upper levels
of the atmosphere, a split flow pattern was observed with a broad
trough over the Western U.S. and another trough digging over the
central Canadian Prairie Provinces.

For late this afternoon and tonight, we will see shortwave energy
rotating around the base of the northern trough and through the
forecast area. This will help push the southeast MT surface low
into southwest ND and bring warm advection into western ND. In
addition, moderate to strong FGEN forcing will swing through the
forecast area, ahead of the approaching upper trough. These
forcing mechanisms are expected to produce an area of
precipitation that spreads from west central and southwest ND
into central ND this evening through Friday morning, then across
the remainder of south central ND and the James River Valley
Friday morning and into the early afternoon hours.

Although the synoptic scale forcing is not strong, it is present
over western ND this afternoon into this evening, and spreading into
central ND late this evening into mid-morning Friday. What is
impressive is the moderate to strong FGEN forcing from 925 mb
through 700 mb. In addition, at times the strong Forcing is
congruent with negative EPV and especially steep lapse rates.
Although this is a transient wave, or series of impulses, the
FG forcing is such that there could be periods of moderate to
heavy snow at times as the entire system propagates west to east
across the forecast area. The latest WPC snowband tracker shows
the potential for snow bands setting up over southwest and
south central ND. With the synoptic scale forcing not being as
strong, we could see a better potential for unorganized, or
transient bands setting up, rather than a single strong band.
This is noted in some of the higher resolution qpf signals.
Unfortunately exactly where these bands set up, is still a bit
up in the air. However, with central ND being a popular area for
bands to propagate across, we included a portion of the
southwest and south central in a winter weather advisory. This
areas has the highest potential for at least 2 inches of snow,
and with the strong signal for FG forcing and steep lapse rates,
we thought it would be best to at least start with an area to
include within an advisory.

It is certainly possible, probably expected that there may need
to be changes to the advisory. The most uncertain areas at this
time appear to be the southwest. With our given guidance, and
the expected warmer temperatures here today (currently mid to
upper 40s) snow amounts here are lighter due to more of a
rain/snow mix this evening. However, with the higher elevation
in the southwest and far west-central, could definitely see a
quicker transition to all snow, especially with the strong FG
forcing. If this would happen, it`s possible the advisory would
need to be expanded into portions of the southwest. Also, there
are some of the CAMS that show bands of higher snow amounts
poking north of the advisory. Moreso over the north central
rather than the northwest. With the orientation of the upper
trough and the FG forcing, a southwest to northeast orientation
of bands seems reasonable and a few of the CAMS do push some
heavier amounts into the north central. Overall though, we felt
the uncertainty up there was too high for an advisory at this
time. Another area of concern is the James River Valley. there
is a southern stream wave that may play a part in resulting
precipitation over the JRV Friday. However, again, uncertainty
is too high here for an advisory at this time, and it would be
late enough that the advisory could be extended to include this
area on the evening or overnight shift. Finally, the Morton and
Burleigh counties are in the advisory, but unfortunately due to
the size of the counties, and the orientation of the heavier
snow, they are right on the edge, with higher snow amounts north
and lower snow amounts over southern portions of these counties.
Due to the steep lapse rates and strong FG forcing, we felt
these counties were close enough the the higher qpf amounts to
include them in the advisory. The total QPF with this system
ranges from around a quarter to nearly a half inch from the west
central into the Garrison area of southern Mclean and into
western Sheridan county, with another band (0.20in to 0.40in)
that extends from eastern Lake Sakakawea into far southwest ND.
This is that band that includes northern Burleigh and Northwest
Morton counties.

Once the precipitation moves out of the area Friday, we see a
mainly dry period from Friday night through Monday night. Friday
night into Saturday morning looks to be quite cold for this time
of year, behind the exiting system. Forecast lows are mainly in
the teens. Highs on Saturday only climb into the 30s over
portions of central ND, with 40s west. We do finally warm up
next week but the warm-up may be delayed to mid to late week.
With a northwest upper flow a diurnally driven shower can not
be ruled out next week, but at this time the chances of any
significant precipitation look to be low. We may need to monitor
fire weather, first on Saturday, but it does look to be cool,
then next week, mainly mid to late in the work week.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 715 PM CDT Thu Apr 3 2025

VFR east to IFR west currently. A line of snow and rain is
moving through the west currently, and will continue across the
state overnight. LIFR CIGs are likely with the heavy snow
overnight. As of 00z, thunderstorms are in the southwest, might
have to add TSRA to the KDIK TAF if it continues. This system
will clear out by 18z.


&&

.BIS WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 1 PM CDT /noon MDT/ Friday for
NDZ018>022-032>035.

&&

$$

UPDATE...Smith
DISCUSSION...TWH
AVIATION...Smith