Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 181445
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
945 AM CDT Mon Mar 18 2024

.KEY MESSAGES...

- Much warmer and windy today, with near critical fire weather
  conditions.

- Well below normal temperatures Wednesday through the weekend,
  with daily chances for snow.

- Medium to high chances (60 to 80 percent) for at least one
  inch of snow across northwest, central, and southeast North
  Dakota Wednesday evening through Thursday.

- Low to medium chances (30 to 50 percent) for a more impactful
  winter weather system this weekend.

&&

.UPDATE...
Issued at 945 AM CDT Mon Mar 18 2024

Quiet weather this morning, with southwest winds already
becoming breezy across the area as the surface pressure gradient
tightens. Main update was to freshen up cloud cover, with a
thicker swath of cirrus moving into north central North Dakota,
and satellite imagery shows this extending upstream into the
southern Canadian Prairies. Otherwise, going forecast looks good
for the warmest day of the next week.

.UPDATE...
Issued at 639 AM CDT Mon Mar 18 2024

The forecast for today remains on track. Current observations
and trends were blended in for this update.

&&

.DISCUSSION...
Issued at 439 AM CDT Mon Mar 18 2024

Surface high pressure lies underneath northerly flow aloft over the
Northern Plains early this morning, with highly amplified downstream
troughing and upstream ridging. As the upper air pattern begins to
deamplify later today, a shortwave/surface low will cross central
Canada, bringing a warm front across the state. With all of western
and central North Dakota expected to reside in the warm sector for
peak diurnal heating, afternoon temperatures are likely to reach the
50s east to 60s west. But it will also become windy today as the
Canadian low pushes the Northern Plains high to the southeast. For
most of the afternoon, winds will primarily be southwest to west
around 20 to 25 mph, gusting to 35 to 40 mph. Even though the warmer
air mass will increase atmospheric moisture, the warmer surface
temperatures will force relative humidity into the 25 to 35 percent
range this afternoon. The combination of the lower humidity and
stronger winds is expected to create near critical fire weather
conditions this afternoon across much of southern and central North
Dakota, extending into the Devils Lake Basin.

The cold front attendant to the Canadian low is forecast to move
across the state from northwest to southeast late this afternoon
through the evening. It will likely remain breezy behind the front
through the night, with winds turning to the northwest. However, the
stronger boundary layer winds and antecedently warmer air mass will
actually keep temperatures relatively mild overnight, with lows
generally around 30 degrees.

A strong thermal gradient is forecast to set up from northwest to
southeast on Tuesday underneath cyclonic northwest flow. There is a
small chance (around 10 percent) that diurnal heating could generate
some afternoon flurries or light snow showers, mainly in the Turtle
Mountains area. Otherwise, it is likely to remain windy on Tuesday,
especially from central into eastern North Dakota. Highs on Tuesday
will be cooler across the north (30s) but remain closer to average
across the south (40s).

Strong surface ridging extending southeast from high pressure over
central Canada will build into the region on Wednesday, marking the
beginning of a prolonged period of well below normal temperatures.
Despite the departure of the surface high later on Wednesday, an
increasingly active pattern defined by a transition from northwest
flow to mean central CONUS troughing will keep the colder air mass
mostly in place. Except for southwest parts of the state on
Wednesday and Thursday, highs are unlikely to rise above freezing
from Wednesday through the weekend and into next week.

There continues to be strong model agreement on a shortwave ejecting
off the Northern Rockies on Wednesday. Some lighter snow could fall
over southwest North Dakota during the day Wednesday, but the
highest chances for accumulating snow will arrive with the vort max
later Wednesday night, lasting through the day Thursday. The NBM has
taken a slight shift to the south with the corridor of highest snow
probabilities compared to yesterday, now lying from near Williston
to Wahpeton. Confidence in the occurrence of lower amounts remains
high, with a 70 to 90 percent chance this system will produce a
swath of at least 2 inches. However, there is still a potential for
a mesoscale banding event, with several ingredients forecast to be
present. The big question is whether these ingredients will line up.
We should be able to get a better idea on the banding potential once
CAMs` forecast time range begins to cover the event.

At least low to medium chances for snow remain in the forecast from
Thursday night through the weekend. However, the late Saturday
through Sunday time period is worth paying close attention to. While
ensemble cluster analysis reveals numerous outcomes, a common theme
is for southwest/zonal flow aloft preceding a progressive trough,
with Colorado low potential. Ensemble low tracks show very large
spread, but it is interesting to note that NBM probabilities for
exceeding 6 inches of snow over a 48-hour period from Saturday
evening through Monday afternoon are already as high as 40 to 60
percent over much of western and southern North Dakota. Other
ensemble data, such as WPC probabilistic QPF and the ECMWF EFI, seem
less bullish. But ensemble mean QPF across all systems does exceed
half an inch, and there are non-zero, but very low probabilities for
extravagant amounts of snow. It is far too early to have any level
of confidence in what will transpire this weekend, but it is
becoming clear that it will be a period to monitor for potentially
impactful winter weather.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 639 AM CDT Mon Mar 18 2024

VFR conditions are expected through the forecast period. Winds
will begin to increase out of the southwest later this morning
and continue increasing through the afternoon while gradually
turning to the west and northwest. Sustained speeds around 20
kts and gusts to around 30 kts can be expected at most terminals
during the afternoon. Gusty northwest winds will then continue
through tonight.

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

UPDATE...Jones
DISCUSSION...Hollan
AVIATION...Hollan


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