197
FXUS63 KBIS 300611
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
111 AM CDT Mon Sep 30 2024

.KEY MESSAGES...

- Critical fire weather conditions expected across much of
  western and south central North Dakota tonight through Monday.

- Much cooler with strong northwest winds on Monday.

- Increasing potential for areas of frost across western North
  Dakota Monday night into Tuesday morning.

&&

.UPDATE...
Issued at 111 AM CDT Mon Sep 30 2024

At 1 AM CDT, the cold front was roughly located from near Minot
to Beulah to Hettinger. Gusts behind the front have mostly been
in the 40 to 50 mph range, with a few sporadic higher gusts.
Radar continues to detect high-based showers along the cold
front, but most of this is likely not reaching the ground, or at
the very least, is not resulting in measurable precipitation.
In addition, little to no lightning has been observed over the
past hour. We expect these trends to continue through the night,
with decreasing probabilities of rain and near-zero
probabilities for lightning downstream.

UPDATE
Issued at 1014 PM CDT Sun Sep 29 2024

It appears as if the cold front has just entered the northwest
corner of the state. Western portions of Divide county are
starting to see winds shifting to out of the northwest.
Isolated showers and thunderstorms have developed behind the
front across eastern Montana and should approach the North
Dakota border over the next hour or so. For this reason, we
decided to introduce isolated precipitation chances gradually
moving through the west and then portions of the central in the
03z to 08z time frame. RAP soundings suggest that we could see a
couple hundred J/kg of MUCAPE across portions of the west until
around 06z or so, so we did add an isolated mention of thunder
until then.

Finally, we let the Red Flag Warning expire on time for Ward,
McHenry, McLean, Sheridan, Burleigh, and Kidder counties.
Humidity values have recovered mainly into the 30 to 40 percent
range and the winds are not quite as strong as they were
earlier. Winds will increase again late tonight and tomorrow,
but cooler temperatures should lead to higher humidity values
for the counties mentioned above. Much of the south central and
portions of southwest North Dakota remain in a Red Flag Warning
through 7 PM CDT Monday and at 1 AM CDT on Monday it will also
go into effect for Bowman, Slope, Billings, Golden Valley, Dunn,
McKenzie, and Williams counties. The Wind Advisory remains in
good shape.

UPDATE
Issued at 615 PM CDT Sun Sep 29 2024

We have seen well above normal heat for the end of September
across western and central North Dakota this afternoon.
Hettinger officially hit 100 degrees and as of this evening, we
still have several sites still sitting in the mid to upper 90s.
Bismarck has shattered the record high today (we hit 97 at the
Bismarck airport, breaking the old record of 90) with Minot and
Dickinson also breaking records (Williston would have broken
the record if the reading was still at the old airport). The Red
Flag Warning remains in good shape with widespread dry and windy
conditions still going strong.

&&

.DISCUSSION...
Issued at 315 PM CDT Sun Sep 29 2024

Currently, upper ridge axis has shifted to the east as a well
defined mid level S/WV moves onshore and advances inland across
the far Pacific Northwest/Southwestern Canada. Associated
sfc/mid level low has resulted in increasing southerly flow
into the region, promoting strong WAA and unseasonably warm
temperatures across the Dakotas. Boundary layer temperatures
are at or above the 99th percentiles of climatology today, with
record high temperatures already set at several locations
across western and central ND. Coupled with strong moderate to
strong mixing, afternoon relative humidity has fallen into the
teens and 20s, resulting in critical fire weather conditions
central and across parts of southwest ND. The Red Flag warning
thus remains valid (See Fire Weather Discussion Below for more
information).

The aforementioned S/WV will continue east along far southern
Canada/Northern Plains region tonight into Monday, and will
drive a strong cold FROPA through the region later this Sunday
evening through early Monday. Resultant weather will be
northwest winds increasing west to east, along with much cooler
temperatures surging into the region (Highs Monday upper 50s
northwest - low 70s southern James Valley), around 20-35 degrees
cooler than today. The main concern with the frontal passage
remains strong wind and fire weather. Opted to issue a wind
advisory across the entire CWA from 03Z this evening through the
day Monday. Strongest winds will likely occur along and behind
the FROPA tonight-Monday morning, where winds will gust to
around 50 mph. BUFKIT soundings and ensemble probabilities are
in agreement with warning criteria winds remaining aloft, but
wouldn`t be surprised to see a few +58 mph gusts late
tonight/early Monday with the front.

Very dry air will also accompany the frontal passage, and will
result in another period of critical fire weather. Opted to
upgrade the Fire Weather Watch for tonight/Monday to a Red Flag
based on the projected Min humidity, strong northwest winds, and
in collaboration with our neighbors. The Red Flag over western
ND will start late tonight, while the Red Flag south central and
for parts of the southwest will basically remain valid now
through Monday. Again, see Fire Weather discussion below for
details.

A quasi-zonal flow pattern remains forecast for the remainder
of the work week, with mainly dry weather conditions and
temperatures more seasonal. The probabilities for morning frost
and minimum temperatures dropping to around freezing continue to
increase for Tuesday morning west, with another chance next
week Friday morning. In addition, can`t rule out more elevated
fire weather concerns next week, as fuels cure and we see
several dry and breezy days ahead.

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 111 AM CDT Mon Sep 30 2024

VFR conditions are expected through the forecast period.
However, there is a low chance for a period of MVFR ceilings in
northwest North Dakota late Monday morning into the afternoon. A
cold front moving across the state late tonight will bring
strong northwest winds gusting to around 40 kts through Monday
afternoon. Ahead of the front, significant low level wind shear
will impact south central and eastern North Dakota overnight,
including at KBIS and KJMS.

&&

.FIRE WEATHER...
Issued at 315 PM CDT Sun Sep 29 2024

Record-breaking high temperatures in the 90s reducing humidity
this afternoon into the 10 to 20 percent range across western
and most of central North Dakota. In addition, gusty southerly
winds with sustained speeds around 20 to 30 mph and gusts to
around 40 mph have been common central and east. Combination of
these conditions results in critical fire weather, thus the Red
Flag Warning remains in effect. Outside of the Red Flag
Warning, which is in effect through this evening, near-critical
fire weather conditions are expected.

A strong cold front moves across the state late tonight through
early Monday morning, bringing a reinforced shot of dry air.
This will produce a unique setup where poor to very poor
overnight RH recoveries will combine with the cold FROPA winds
to produce nocturnal critical fire weather conditions west and
sustain critical fire weather conditions south central. The
expected wind shift from south to northwest will also support
Red Flag conditions. Opted to upgrade the Fire Weather watch to
a Red Flag, starting in the west late tonight, and keeping the
Red Flag warning south central ongoing. Later shifts can adjust
as needed.

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
Wind Advisory until 7 PM CDT /6 PM MDT/ this evening for
NDZ001>005-009>013-017>023-025-031>037-040>048-050-051.
Red Flag Warning until 7 PM CDT /6 PM MDT/ this evening for
NDZ009-017-018-031-032-040-043.
Red Flag Warning until 7 PM CDT /6 PM MDT/ this evening for
NDZ019-020-033-034-041-042-044>047-050.

&&

$$

UPDATE...Hollan
DISCUSSION...NH
AVIATION...Hollan
FIRE WEATHER...NH