Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 190559
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
1259 AM CDT Tue Mar 19 2024

.KEY MESSAGES...

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

- High chances (70 to 90 percent) for at least two inches of
  snow across northwest, central, and southeast North Dakota
  Wednesday night through Thursday night, with lower chances in
  the southwest and north central.

- Medium chances (50 to 70 percent) for a more impactful winter
  weather system this weekend, with the highest potential across
  southern North Dakota.

&&

.UPDATE...
Issued at 1258 AM CDT Tue Mar 19 2024

No major changes are needed for this update. Current
observations and trends were blended into the forecast.

.UPDATE...
Issued at 925 PM CDT Mon Mar 18 2024

A dry cold front has moved through all but the James River
Valley as of 9 PM this evening. There were a few mid clouds
associated with the front, otherwise skies were clear across
western and central North Dakota this evening with very mild
temperatures (current BIS temp is 49 degrees). It will remain
a little more breezy over northern and eastern portions of the
forecast area tonight with lighter winds southwest and south
central. Overnight lows are forecast to only drop into the mid
20s to lower 30s, much warmer than the single digits and teens
most areas last night into early this morning. The only updates
were to sky cover with the quick moving cold front moving
through the area. Updated text products will be sent shortly.

.UPDATE...
Issued at 623 PM CDT Mon Mar 18 2024

After a slow start this morning, temperatures really took off
this afternoon. 6 PM temperatures were in the mid 60s across
much of southwest and into south central ND. Readings in the 50s
covered most of the rest of the forecast area, except for a
couple upper 40s in far eastern portions of the CWA.

A dry cold front is currently pushing from northern into
central ND, and will continue to push south through the evening.
Ahead of the cold front, relative humidities were mostly in the
20 to 30 percent range. Areas over far southern ND will see
these humidities slowly rise over the next couple of hours.
Farther north, over central ND, RH values will drop quicker
with the passage of the cold front. RH values over the northern
half of the CWA are already 30 to 45%. West (south) to
northwest (north) winds will diminish slowly this evening, and
my remain gusty over eastern portions of the CWA into the
overnight hours. Only minor updates to sky cover with minimal
clouds associated with the southward moving cold front.

&&

.DISCUSSION...
Issued at 312 PM CDT Mon Mar 18 2024

This afternoon, the synoptic pattern was characterized by strong
northwest flow over the Northern Plains, downstream of a stout high
centered over southern Oregon and northern CA/NV. To our north is a
deep surface low centered in northern Manitoba, with a warm front
extending southwest that is placed in far western North Dakota. An
enhanced pressure gradient is producing windy conditions across
western and central North Dakota, with sustained southwest winds
around 20 mph and gusting to 30 mph. Winds are expected to gradually
shift more westerly as the front moves through, although the front
is moving a touch slower than forecast. We`ve nudged forecast highs
down just a touch in central North Dakota, as temperatures have not
been warming as fast as expected in these areas. A few high clouds
are drifting across the central, otherwise skies are sunny across
the forecast area.

Near critical fire weather conditions continue through the afternoon
from the combination of wind speeds and minimum relative humidity in
the 20 percent range across most of southern North Dakota.

The cold front associated with the previously mentioned low will
move south through the area tonight, shifting winds to northwesterly
and keeping them breezy with cold air advection and marginal
pressure rises. Cloud cover will also increase across the eastern
half of the state, with overnight lows generally in the mid 20s to
lower 30s.

Winds stay breezy on Tuesday in the wake of the cold front, while a
thermal gradient sets up across the state, leading to highs in the
30s north to around 50 in the far southwest. A couple of the latest
high-res runs are advertising some scattered snow showers in our far
eastern counties, but carrying a dry forecast for the moment.

The upcoming active period starts midweek, as deterministic and
ensemble guidance are in fairly good agreement on a shortwave moving
through North Dakota, bringing a shot of accumulating snow Wednesday
night through Thursday. Current expectation is for a northwest-
southeast swath of snow, with a high chance of at least 2 inches of
snow from Williston, through Bismarck, and to Jamestown, with medium
chances for at least 4 inches of snow in a similar area. As the
previous shift noted, there is some low potential for banded
snowfall, although the latest run of deterministic guidance does not
look favorable for that, besides some marginal frontogenesis lurking
around. We need to be closer in time to resolve those mesoscale
details, and we`re just starting to get into the time frame of CAMs,
with snow ramping up Wednesday evening.

Focus then turns to this weekend, with potential for impactful
winter weather. There is still a large amount of uncertainty
regarding how the synoptic pattern evolves. However, there is
increasing confidence in accumulating snow, with late Saturday
through Sunday night as the period of emphasis. The general
pattern seen in ensemble cluster analysis is for
southwest/quasi-zonal flow aloft in place before a trough moves
through the central CONUS over the weekend, but differences
emerge in the timing and strength of the trough, as well as if
it develops into a closed low or not. It`s worth noting that all
cluster solutions do have precipitation, but the amounts vary a
moderate amount. The latest NBM shows increased probabilities
of significant snow amounts, with the 48-hour probability of at
least 6 inches of snow ending Monday afternoon rising to 50-70%
across the southern half of the state. The probability for at
least one foot of snow is exceeding 30% in some areas, so there
is growing concern for higher- end snow amounts.

It`s also worth noting that temperatures will continue to be well
below average through the extended period and beyond, with high
confidence in high temperatures staying in the 20s to lower 30s, and
lows in the teens. Fresh snowpack could potentially keep these
temperatures even cooler. Below normal temperatures are favored
through the end of the month.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1258 AM CDT Tue Mar 19 2024

A period of MVFR ceilings is likely from KMOT to KJMS late
Tuesday morning into the afternoon. It is possible the MVFR
ceilings could also reach KBIS and KDIK, but confidence is lower
there. VFR conditions are otherwise expected for the forecast
period. Northwest winds will remain breezy overnight and through
much of the day Tuesday across central and eastern North Dakota.

&&

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

&&

$$

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


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