933
FXUS63 KBIS 050514
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
1214 AM CDT Sat Oct 5 2024

.KEY MESSAGES...

- Saturday continues to look very windy, especially north.
  Sustained west northwest winds up to 45 mph and gusts up to
  65 mph are expected. Wind headlines have been issued.

- Critical fire weather conditions are also expected on Saturday
  due to the strong winds and dry conditions. A Red Flag
  Warning has been issued.

- After a windy and cool weekend, we will warm back into the 80s
  by next week with relatively calm winds. The forecast should
  remain pretty much dry.

&&

.UPDATE...
Issued at 1205 AM CDT Sat Oct 5 2024

No changes to the going forecast at this time. Will be
monitoring front as it moves towards western ND. Just recently a
gust to 92 mph at GGW, which may have bee convectively enhanced,
or not. Otherwise quite a few gusts in the 40-50 knot range over
northeast Montana. HWW already in effect northwest and west
central, but may need to start it a bit earlier. Will need to
decide on what to do with the watch in the southwest. Think we
have an hour or two to see obs in northeast and east central MT.

UPDATE
Issued at 945 PM CDT Fri Oct 4 2024

At the time of this evening update, generally quiet conditions
are found across western and central North Dakota. Breezy south
winds continue, with speeds generally from 10 to 15 MPH with a
few, more isolated locations up to 20 MPH. While skies across
remain generally clear in the south, a deck of mid to high
levels clouds continues to push in across our northern counties.
Have made a few minor tweaks to the sky grids to account for
these slightly denser clouds across the north central, but
otherwise the forecast remains on track at this time.

UPDATE
Issued at 645 PM CDT Fri Oct 4 2024

Generally breezy conditions are found across western and central
North Dakota this evening as an Alberta low pressure center
approaches the northern Plains and the surface pressure gradient
tightens. Winds are out of the south, generally from 15 to 20
MPH along with gusts up to 30 MPH. Skies remain mostly clear,
though some wispy high clouds have begun to push in across the
International Border and from northeastern Montana. No
adjustments were needed at the time of this update, as the
forecast remains on track.

&&

.DISCUSSION...
Issued at 315 PM CDT Fri Oct 4 2024

Western and central North Dakota sits under the influence of
broad ridging aloft. A surface low was located over Alberta and
a surface high over the Great Lakes Region. Ridging will slowly
move off to the east this evening as the surface low approaches
and the gradient increases. This will keep breezy southerly
winds in the forecast through the rest of today and into the
evening. These breezy winds could lead to some near critical
fire weather conditions across portions of the southwest and
south central for the remainder of the afternoon. For more
information on fire weather, see the Fire Weather section
below.

A strong surface cold front will move into the northwest in the
06z to 09z Saturday time frame. Much of the previous thinking
regarding the winds remain the same. There will likely be an
initial strong wind push behind the front overnight, especially
across the west where we could see some short duration High Wind
Warning criteria gusts. Even with the less than favorable
diurnal timing, the isallobaric component should lead to a few
sporadic gusts over 58 mph (warning criteria). This front will
wash out a bit as it moves into the central. Thus, there could
be a little bit of a lull in the stronger winds Saturday morning
before a secondary push of cold air moves in later in the
afternoon. This secondary push of strong cold air advection will
accompany very steep low level lapse rates, and pressure rises.
Forecast sounding illustrate the lapse rates well with
impressive inverted V structures. The best signal for very high
winds continues to be focused across the north, where the EFI is
pegging a large area of 0.90 or greater (which would suggest a
warning level event). The shift of tails has not been as
consistent but we do have some values across the north of one or
greater. Thus, a warning event seems likely but an extreme
event, maybe not as likely. Given all of this information, we
elected to trend towards the NBM 90th percentile for winds
across the northern third of western and central North Dakota
and the NBM 75th for winds elsewhere. All in all, we elected to
keep the timing the same as the previous High Wind Watch
segments but we did decide to upgrade northern portions of of
the Watch to a Warning. All counties along and north of
McKenzie, Dunn, McLean, Sheridan, Kidder, and Stutsman counties
have been upgraded to a High Wind Warning. Areas further south
could still see high wind criteria, but too much uncertainty
exits here to upgrade at this time. Will leave Watch as is for
the southern areas. For areas in the warning, we could see
sustained winds up to 45 mph and gusts to 65 mph. For areas in
the watch, sustained winds will range from 30 to 40 mph with
gusts in the 55 to 60 mph range.

With the winds and dry atmosphere, we are also expecting
critical fire weather conditions and a Red Flag Warning has
been issued. For more on the fire weather threat, please see the
Fire Weather section below.

Winds will gradually diminish through Saturday evening and into
the overnight. By Sunday morning, surface high pressure should
start to move in with some breezy northwest winds hanging on
east through the first part of the day. Highs on Sunday will be
in the upper 50s to the upper 60s but we will see the 80s
return to the forecast in the Tuesday through Thursday time
frame. The forecast also looks to mainly be dry except for a
very slight chance of a shower or two across the far north on
Saturday.

&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 1205 AM CDT Sat Oct 5 2024

VFR ceilings and visibility are expected at all terminals
throughout the 06Z TAF period. Breezy to strong southerly winds
are generally from 15 to 25 knots and gusts up to 35 knots will
shift west to northwest as a strong cold front passes through
from northwest to southeast through this morning. Enhanced low
level wind shear is anticipated at all sites ahead of the cold
front passage. Probably a brief lull after the initial frontal
passage, then from late morning through the early evening look
for sustained winds of 35 to 40 knots and gusts up to 55 knots
possible this afternoon, especially across the northwest and
north central. Winds will begin to diminish this evening,
though the north central and eastern North Dakota is expected to
remain breezy through the end of the TAF period.

&&

.FIRE WEATHER...
Issued at 229 PM CDT Fri Oct 4 2024

For the rest of this afternoon, we could still see a few hours
of near critical fire weather conditions across portions of the
southwest and south central. Highs here will range from the
lower 70s south central to the upper 70s southwest and minimum
afternoon relative humidity should generally range from 20 to 30
percent. Southerly winds have trended a bit lower than
previously forecast but we should see some periodic sustained
winds in the 15 to 25 mph range so we will continue messaging
near critical fire weather potential.

Looking ahead to tomorrow. A strong cold front will cross the
state tonight from northwest to southeast, shifting the winds to
out of the west northwest. Behind this front, winds will
increase Saturday morning and especially in the afternoon. We
should see widespread sustained winds in the 35 to 45 mph range
with gusts in the 55 to 65 mph range for much of the area. These
winds will be the driving force for critical fire weather
conditions across most of western and much of central North
Dakota mid to late Saturday morning through Saturday evening.
While highs will mainly be in the 60s and humidity will only
bottom out in the 20 to 30 percent range, winds should be plenty
strong enough to compensate. For these reasons, we went ahead
and issued a Red Flag Warning for most of western and central
North Dakota (11 AM CDT to 9 PM CDT). The only exceptions will
be across the far north and Devil`s Lake Basin, where humidity
should be quite a bit higher and we could see some more cloud
cover. That being said, near critical fire weather conditions
will be possible here as the strongest winds should be across
the north. Winds will gradually diminish through Saturday
evening and humidity will recover into the 70 to 100 percent
range overnight.

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
High Wind Warning from 4 AM CDT /3 AM MDT/ early this morning
to 10 PM CDT /9 PM MDT/ this evening for NDZ001-002-009-010-
017-018.
High Wind Warning from 7 AM this morning to 1 AM CDT Sunday
for NDZ003>005-011>013-021>023-025-036-037.
Red Flag Warning from 11 AM CDT /10 AM MDT/ this morning to 9
PM CDT /8 PM MDT/ this evening for NDZ009>012-017>022-031>037-
040>048-050-051.
High Wind Watch from 7 AM CDT /6 AM MDT/ this morning through
late tonight for NDZ019-020-034-035-042-045>048-050-051.
High Wind Watch from 3 AM MDT Saturday through Saturday
evening for NDZ031>033-040-041-043-044.

&&

$$

UPDATE...TWH
DISCUSSION...ZH
AVIATION...TWH
FIRE WEATHER...ZH