606
FXUS63 KBIS 092041
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
341 PM CDT Sun Mar 9 2025

.KEY MESSAGES...

- Very strong winds gusting as high as 65 mph are expected
  across the state on Monday.

- Enhanced critical fire weather conditions are expected across
  the southern half of the state on Monday.

- Medium chances for impactful winter weather Friday through
  Saturday, including accumulating snow, blowing snow, and mixed
  precipitation.

&&

.DISCUSSION...
Issued at 340 PM CDT Sun Mar 9 2025

The Northern Plains sit under northwest flow aloft this afternoon,
with upstream ridging over the Rockies. High clouds streaming off
the mountains in the anticyclonic flow regime are not being picked
up by guidance, and therefore have had to rely on observed trends
for the sky cover forecast. Despite more clouds than expected, dry
westerly low level flow has promoted strong diurnal mixing of the
boundary layer, allowing afternoon temperatures to climb into the
mid 50s to mid 60s over much of the state, with 40s across parts of
the far north where some appreciable snow pack remains. West-
northwest winds have increased to around 20 mph, with gusts as high
as 30 mph. Relative humidity has fallen to around 20 percent across
most areas south and west of the Missouri River, which combined with
the winds has led to near-critical fire weather conditions. Periods
of high clouds may continue to stream over the region through
tonight as winds turn southwesterly around 10 to 15 mph. Lows
tonight are expected to remain above freezing for most of the area.

A powerful shortwave trough will eject off the Norther Rockies early
Monday morning and quickly move along the international border
through the day, reaching western Ontario by Monday evening.
Confidence remains high that the attendant cold front will bring
very strong winds across the region throughout the day, as forecast
parameters across all deterministic guidance consistently include
surface pressure rises on the order of 10-15 mb per 3 hours, cold
air advection on the order of 40 degrees Celsius per 12 hours, and
steep low level lapse rates with 50-60 kt winds in the top half of
the mixed layer. The only possible mitigating factor is that there
are times when BUFKIT profiles show little to no downward vertical
motion until the cold front moves through, and when it does there is
a mid level inversion. Feel that this is unlikely to greatly limit
maximum surface gust potential given all other ingredients are at
the higher end of the spectrum. Additionally, numerous model
soundings show up to 100 J/kg SBCAPE which could result in sprinkles
or virga (south) to scattered rain/snow showers (north) that could
also enhance surface wind gusts through the evaporative cooling
process. All said, forecast confidence is high enough to upgrade to
a High Wind Warning for all of western and central North Dakota. The
forecast timing of the highest gusts is mid morning to mid afternoon
in the northwest, late morning to late afternoon southwest and north
central, and early afternoon to early evening south central and
James River Valley.

Temperatures across all but far northern parts of the state are
forecast to rise into the mid 50s to mid 60s prior to the cold
frontal passage. Areas immediately downstream of the front through
the afternoon, which are most likely to include south central North
Dakota and the James River Valley, could see a boost above our high
temperature forecast due to compressional heating. Behind the front,
temperatures will begin falling, rapidly so across the north where
sub-freezing values are forecast by early evening. Circling back to
the potential for rain/snow showers across the north as the
mid/upper level wave passes by in closer proximity, there is a low
probability for a snow squall with the cold frontal passage across
the far north Monday afternoon that will need to be monitored
closely as the time approaches, as current deterministic guidance is
showing most of the requisite ingredients. In contrast, there is
concern for a potentially dangerous fire weather setup across the
southern half of the state where a Red Flag Warning is in effect.
See the FIRE section below for a detailed discussion.

Tuesday will be colder, but still near to above normal with highs in
the mid 30s northeast to lower 50s southwest. A much weaker
shortwave passing through the region could provide some light rain
or snow showers Tuesday afternoon, but the chance of anything
measurable is only 5 percent south to 20 percent north. An
amplifying upper ridge from the Rockies to High Plains is then
forecast to bring another warming trend for Wednesday and Thursday,
with forecast highs mostly in the 50s on Wednesday and mid 50s to
mid 60s on Thursday.

Not much has changed regarding forecast thinking and probabilities
for the winter storm potential later this week. Ensemble clusters
continue to present two distinct scenarios of a stronger, slower
system (dominant solution in the GEFS) and a more progressive,
slightly weaker system (dominant solution in the ECMWF ensemble).
But there are clear differences in QPF/snowfall within each of those
two scenarios, and additional underlying uncertainty with how a
northern stream wave could interact with the Colorado low.
Probabilities for the stronger and slower solution, which in turn
have higher snow amount probabilities, have fallen to 40 percent
with the 12Z ensemble runs. However, accumulating snow is only one
aspect of this system. There is still potential for impacts from
mixed precipitation, although all latest ensemble data has shifted
this more into eastern North Dakota. More concerning though is the
potential for very strong winds combining with any amount of snow to
create significantly reduced visibility. All ensemble clusters show
850 mb winds in the 40-55 kt range (with varying northward extent)
over a strong MSLP gradient through central North Dakota. Therefore,
we will continue to mention slightly higher odds (55 vs. 45 percent)
for impactful winter weather for central North Dakota Friday through
Saturday, even though snow probabilities themselves are trending
slightly lower.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1257 PM CDT Sun Mar 9 2025

VFR conditions are expected through the forecast period. Expect
westerly winds around 15-20 kts this afternoon, with some higher
gusts. This evening through tonight, winds will become
southwesterly around 10-15 kts, with low level wind shear
impacting the western half of the state. By late Monday morning,
a very strong cold front will begin entering the state from the
northwest. As the front sweeps through, west to northwest winds
are expected to gust as high as 50-55 kts. Outside of northwest
North Dakota, these higher gusts will likely be delayed until
Monday afternoon.

&&

.FIRE WEATHER...
Issued at 340 PM CDT Sun Mar 9 2025

Near-critical fire weather conditions will continue across southwest
and south central North Dakota through this afternoon, with west-
northwest winds around 20 mph and relative humidity as low as 20
percent.

Monday is looking very concerning from a fire weather perspective.
Strong westerly winds will increase up to 40 mph with gusts as high
as 65 mph as a cold front moves across the state from northwest to
southeast from mid Monday morning through Monday afternoon. A wind
shift from west to northwest is also anticipated with the frontal
passage. Before the front arrives, relative humidity is forecast to
fall into the 20 to 30 percent range, lowest along the South Dakota
border. Humidity will begin to recover quickly behind the wind
shift, but the overlap of lower humidity with the very strong winds
is expected to last for several hours across the southern half of
the state during the late morning through early evening. Aside from
cold ground and near-surface soil temperatures, fuels have been
reported as readily burnable. Any fires that ignite on Monday will
spread rapidly and could become very difficult to control.

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
High Wind Warning from 9 AM CDT /8 AM MDT/ to 7 PM CDT /6 PM
MDT/ Monday for NDZ001>004-009>011-017.
High Wind Warning from noon CDT /11 AM MDT/ to 10 PM CDT /9 PM
MDT/ Monday for NDZ005-012-013-018>023-025-031>037-040>048-050-
051.
Red Flag Warning from 11 AM CDT /10 AM MDT/ to 8 PM CDT /7 PM
MDT/ Monday for NDZ017>023-025-031>037-040>048-050-051.

&&

$$

DISCUSSION...Hollan
AVIATION...Hollan
FIRE WEATHER...Hollan