304
FXUS63 KBIS 092317
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
617 PM CDT Thu Oct 9 2025

.KEY MESSAGES...

- Mild and dry weather continues this afternoon through Friday.

- Sub-freezing temperatures are expected across parts of
  northwest and central North Dakota tonight into Friday
  morning.

- Windy with increasing chances for rain this weekend. Some snow
  could mix in with the rain in northwest North Dakota.

- Temperatures remain slightly to well above normal through
  Sunday afternoon, before turning much cooler next week.

&&

.UPDATE...
Issued at 606 PM CDT Thu Oct 9 2025

Quiet weather continues across the state as a front has moved
through the region. Surface high pressure is forecast to move
in behind the front tonight across the northwestern half of the
state leading to freezing temperatures. No updates are needed
at this time as the forecast remains on track.

&&

.DISCUSSION...
Issued at 259 PM CDT Thu Oct 9 2025

This afternoon, quasi-zonal flow was in place across the Dakotas
upstream of a deep closed low off the coast of the Pacific
Northwest. A surface high was analyzed in southwest Saskatchewan
and was providing mostly sunny skies, besides a few cirrus
drifting through. Afternoon highs are in the mid 60s to mid 70s
across the area with a touch of a breeze across the north.

A surface high is progged to slide south from the Canadian Prairies
tonight, becoming centered over the state early Friday morning. The
placement of the low combined with expected dry near-surface air,
clear skies, and decreasing winds favors strong radiational cooling.
We did lower temperatures from the deterministic NBM, which
produced lows mainly in the upper 20s to mid 30s north and west,
and the mid 30s to lower 40s in the south central and James
River Valley. A Freeze Warning has been issued for northern
North Dakota and the area around Lake Sakakawea, including
Dunn/Mercer/Oliver Counties, as Beulah and Hazen areas are normal
cold spots. There was some consideration into expanding this to
include the southwest, but confidence was lower in reaching the
32 F threshold.

Friday will be quiet as the high pressure continues drifting
through, while a shallow ridge aloft keeps mostly sunny skies
and highs in the 60s in the forecast. Later in the day we do
develop a breeze across far western North Dakota where the
surface pressure gradient tightens a bit on the backside of the
exiting high.

A deepening trough in the western CONUS turns flow aloft
southwesterly this weekend, with strong southeasterly low-level
winds. Low chances for precipitation begin on Saturday as a weak
wave ejects from the main trough base, before chances increase
Sunday as a much more compact and potent shortwave trough
pushes through the state, along with an attendant surface low
and cold front. On the warm side of the system, forecast bulk
shear looks quite strong with the developing low, although
instability is marginal at best across central and eastern North
Dakota. CSU machine learning guidance does highlight low
probabilities for severe weather central and east on Sunday, so
although low-level moisture and subsequent buoyancy looks a bit
lacking, still something to monitor.

The most confidence regarding the Sunday and Sunday night
system is with very strong winds, as the low wraps up as it
moves across the state. Deterministic guidance is consistent in
strong cold air advection and stout pressure rises behind a cold
front associated with the surface low. There are some
differences in timing which could potentially influence the
upper extent of wind speeds, but the current projections have
winds quickly increasing Sunday afternoon and becoming more
northwesterly from west to east as the low pushes through,
continuing through Sunday night and Monday morning. GFS forecast
soundings have the top of the mixed layer anywhere from 40 to
50 knots Sunday afternoon and evening, and as previous shift
noted, the base NBM NBM likely isn`t high enough if the low
develops as currently forecast. The EFI highlights forecast wind
gusts across state, which local research has shown does
correlate well with wind headline issuance.

The biggest questions with this system is how do the timing of
the front and strongest forcing line up, when does the cold air
really surge in, and when do we end up seeing a switch to snow? The
GEFS continues to be colder and producing more snow compared to
the EC and Canadian ensembles. The 12Z GEFS also seems to have
sped up just slightly, which would favor a slightly weaker
scenario, although there is still overall a broader spread in
the placement of the low amongst GEFS ensemble members compared
to the EC ensemble suite. The ECMWF EFI highlights a shift of
tails but no shading in the snow section, signaling that there
are a few outlier members with climatologically unusual snow
amounts, but overall most members are close to the reforecast
climatology. The latest NBM gives around a 50 percent chance of
measurable snow in the northwest, with decreasing probabilities
to the south and east. The probability of exceeding one inch of
accumulation has increased from the previous forecast, around
30 to 40 percent, although this will be influenced by when rain
changes to snow and what sort of snow rates we end up with,
since soil temperatures in this area are generally around 50
degrees per NDAWN measurements. Regarding QPF amounts overall,
the northwest is favored for the highest precipitation, with
medium to high probabilities of at least half an inch of rain
focused in the far northwest corner. The southwest and south
central have trended drier, with ensemble guidance honing in on
these areas ending up in the dry slot of the system.

Next work week overall is favored to have temperatures closer to
normal and a few chances for precipitation. Monday will feel brisk
after the seasonably mild temperatures we`ve been having, with
cooler air behind the front dropping highs into the mid 40s to mid
50s, paired with a northwest breeze. Expect these temperatures to be
relatively consistent through the week as the synoptic pattern is
dominated by ridging to our east and a deep trough over the western
CONUS. Monday and Tuesday look mostly dry before precipitation
chances increase for the rest of the work week, with CIPs analogs
and ensemble clusters advertising at least some precipitation, just
with differences in how much and when that ends up being.

&&

.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/...
Issued at 606 PM CDT Thu Oct 9 2025

VFR conditions continue across the state through the latest TAF
cycle. Winds will veer out of the southeast late tonight with
afternoon gusts tomorrow across the west.

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
Freeze Warning from midnight CDT /11 PM MDT/ tonight to 9 AM
CDT /8 AM MDT/ Friday for NDZ001>005-009>013-018>021.

&&

$$

UPDATE...Johnson
DISCUSSION...Jones
AVIATION...Johnson