Area Forecast Discussion Issued by NWS Bismarck, ND
000
FXUS63 KBIS 182345
AFDBIS
Area Forecast Discussion
National Weather Service Bismarck ND
645 PM 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.
- 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 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/quasizonal 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 /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 623 PM CDT Mon Mar 18 2024
A cold front is currently moving south through the forecast
area. Southwest winds at KBIS and KJMS will shift west to
northwest this evening. Winds have already shifted at KXWA, KDIK
and at KMOT. Wind speeds generally 15 to 25 knots early evening,
diminishing west pretty quick, but gusty winds may continue
central a bit longer, especially at KJMS. Northwest surface flow
is expected Tuesday generally 15 to 30 knots.
VFR conditions are expected through tonight. On Tuesday, cloudy
skies are expected to develop over central and eastern North
Dakota as colder air drops south behind the cold front. KJMS,
KMOT will likely be impacted with MVFR ceilings. It`s possible
KBIS could see a period of MVFR ceilings late morning into early
afternoon Tuesday as well, but will keep it out of the KBIS TAF
for now.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...TWH
DISCUSSION...Jones
AVIATION...TWH