679
FXUS63 KBIS 060208
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
908 PM CDT Sat Oct 5 2024

.KEY MESSAGES...

- Very windy conditions continue through this evening,
  especially north. Sustained west northwest winds up to 45 mph
  and gusts up to 70 mph are expected. Wind headlines are in
  effect.

- 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 908 PM CDT Sat Oct 5 2024

Winds are starting to diminish late this evening, while cooler
temperatures are starting to improve relative humidity values.
There still could be some near critical fire weather conditions
for the next hour or two in southern portions of North Dakota,
although overall improving conditions are expected. Thus the
Red Flag Warning across much of western and central North Dakota
has been allowed to expire at 9 PM CDT..8 PM MDT this evening.
Next update will take a closer look at the ongoing wind
highlights.

UPDATE
Issued at 650 PM CDT Sat Oct 5 2024

Limited updates needed at this time. Strong winds remain across
much of the CWA. Gusts have come down only slightly, and
generally remain in the 50s and 60s. Thus will maintain current
wind highlights. Some areas in the Wind Advisory could see an
isolated wind gust to 60 MPH, although confidence is not high
enough to upgrade at this time given winds should start to
diminish shortly after sunset. Critical fire weather conditions
will also remain through this evening given these strong winds
and low RH. Winds will diminish tonight with mainly clear skies
expected. The colder air behind today`s cold front could return
low temperatures in the 30s across many areas. Perhaps some
freezing to below freezing temperatures are possible, especially
given the low dewpoints in place. Freeze conditions are
possible, especially across the west, and may have to be
monitored for later updates this evening into tonight.

UPDATE
Issued at 425 PM CDT Sat Oct 5 2024

Quick update to add in some NBM90th percentile for current winds
and wind gusts, which closer matches some of the stronger winds
being observed across the north. Currently the Highway 2
corridor is seeing wind gusts of 70 to 75 mph. South of this
area, gust of 55 to 65 mph are currently being report. These
strong winds are forecast to remain into the early evening.
Winds should start to diminish shortly after sunset. Dry
conditions combined with low RH is currently making critical
fire weather conditions across much of western and central ND.
Updated the Red Flag Warning to include the latest observations.

&&

.DISCUSSION...
Issued at 233 PM CDT Sat Oct 5 2024

Upper level troughing is currently moving through western and
central North Dakota with a closed upper low centered over
western Manitoba. The initial cold front that brought intense
winds to the northwest last night has now moved off into western
Minnesota. However, the latest SPC mesoanalysis suggests that
an intense secondary push of low level cold air advection is
starting to move into the northwest. This cold air is moving
into a very favorable regime for strong to very strong synoptic
winds given the tight pressure gradient and very steep low level
lapse rates (8 to 8.5 C/km) that have developed per
mesoanalysis.

With inverted-V soundings present, it is not taking much to mix
the higher velocity air at the top of the mixed layer down to
the surface. As of early this afternoon we have seen several
sites with sustained west northwest winds in the 35 to 50 mph
range and gusts in the 60 to 78 mph range (mainly over the
northwest and north central). These values at times have been a
touch higher than originally forecast but the Extreme Forecast
Index (EFI) had been hinting at the possibility for some
sporadic extreme values given a large shift of tails area of
greater than one. Looking at soundings, it seems the most
favorable window for the highest winds will generally be from
around now (early afternoon) through 22z or so. After that,
there will be a slow decrease through sunset, and then a more
substantial decrease from west to east overnight. High Wind
criteria (more Advisory criteria) has not really developed
across areas further south yet and may not, but we will hold
onto the Warning in all locations for now since we still have
several hours ahead for winds to increase. Either way, it is
windy across all of western and central North Dakota and wind
headlines look to be in good shape with no changes planned at
the moment.

The other big story today, of course, is the critical fire
weather conditions ongoing or expected across most of western
and much of central North Dakota. High temperatures will be
around or slightly above normal this afternoon, mainly in the
60s (maybe some lower 70s south). Combine those temperatures
with dewpoints in the mid 20s to lower 30s, and relative
humidity values will bottom out in the 15 to 25 percent range
for most of the forecast area except for the far north. This
dry atmosphere will remain collocated with the very strong winds
for several hours, keeping critical fire weather conditions a
concern through at least early evening. The Red Flag Warning
remains in good shape with no changes planned.

As noted above, winds will really start to relax in earnest late
evening and into the overnight. Breezy conditions may hang
around through early Sunday across the James River Valley but
most of the west and central will see relatively calm winds by
about 12z Sunday or so. Sunday will see similar temperatures as
today (maybe just a touch cooler) but winds will be fairly
light (5 to 10 mph) with a surface high moving into the region.

On Monday an upper ridge to our west will amplify slightly as
the axis nudges closer to western North Dakota. This ridge will
be slow to make it`s way across the northern Plains this week as
it flattens and builds back up, the axis finally moving off to
the east mid to late week. This will mean a warmup with highs
returning to well above average for this time of year. Highs on
Monday will range from the mid 60s northeast to the upper 70s
southwest. We will then see some low to mid 80s mix in across
the west on Tuesday with widespread 80s back in the forecast
Wednesday and Thursday. As we approach the weekend, we could see
a little bit of a cool down. That being said, NBM temperature
spread is quite large on Friday, suggesting some uncertainty
regarding the timing of the eventual cooldown/pattern evolution.
Looking, ahead we could see our next low chances of rain over
the weekend depending on how the pattern evolves. Otherwise, the
dry trend continues.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 650 PM CDT Sat Oct 5 2024

VFR conditions are expected through the forecast period. Strong
west northwest winds will be found through this evening, then
diminish overnight tonight. Some MVFR clouds could enter into
northern portions this evening and linger through tonight,
although are not expected to impact any TAF sites at this time.
Mainly clear skies with a light westerly wind is then expected
for Sunday.

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
High Wind Warning until 10 PM CDT /9 PM MDT/ this evening for
NDZ001-002-009-010-017-018-031>033-040-041-043-044.
High Wind Warning until 1 AM CDT /midnight MDT/ Sunday for
NDZ003>005-011>013-019>023-025-034>037-042.
Wind Advisory until 1 AM CDT /midnight MDT/ Sunday for
NDZ045>048-050-051.

&&

$$

UPDATE...Anglin
DISCUSSION...ZH
AVIATION...Anglin