197 
FXUS63 KBIS 181811
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
1211 PM CST Thu Jan 18 2024

.KEY MESSAGES...

- Dangerously cold wind chills as low as 35 below zero are 
  possible across much of western and central North Dakota 
  through Friday morning. 

- Light snow is possible across portions of central and eastern
  North Dakota tonight into Friday morning, with minimal
  accumulations.

- Areas of blowing snow are expected today through tonight, 
  with the highest potential across portions of southwest and 
  south central North Dakota.

- Wind gusts up to 45 mph are possible today and tonight across
  portions of southwest and south central North Dakota.

- Highs for the remainder of the work week will generally be in
  the single digits. Saturday will mark the start of a warmup,
  with above normal temperatures likely next week.

&&

.UPDATE...
Issued at 1208 PM CST Thu Jan 18 2024

The forecast continues to remain on track. Winds have started to 
pick up across the area, bringing about some reduced visibilities 
due to blowing snow, with the strongest impacts in the southwest. 
Snow is likely to continue tapering off through the day, as the main 
impulse of energy slides off to the southeast. The Winter Weather 
Advisory and Wind Chill Advisories remain on track as well. We also 
added in some PoPs (mostly 15 to 20 percent) to the northeast 
tonight into tomorrow morning, as a somewhat weak wave is expected 
to descend south from Canada, bringing just enough energy and 
saturation for some snow crystal growth. Otherwise, just blended the 
current observations into the forecast.

.UPDATE...
Issued at 941 AM CST Thu Jan 18 2024

Snow is continuing to be observed on radar transitioning
southeast this morning. Lowest visibilities are around 2 miles
at stations south of Bismarck. Blowing snow remains a concern
into this afternoon, especially in the southern part of the
state. Forecast remains on track. 

Issued at 611 AM CST Thu Jan 18 2024

Snow has expanded a bit further northeast than expected, with
the north/eastern extent of observed snow from Williston, to 
Stanley, to Denhoff, to Medina. The most impactful snow is in 
southwest North Dakota, where NDDOT road reports show snow-
covered roads. So far, visibilities have stayed in the 1 to 3 
mile range across the south, and slightly higher to the north 
where snow is lighter. 

The Bowman radar shows radar returns are slowly weakening across
the southwest part of the state, as the strongest forcing moves
off further to the east. Light snow or flurries could linger if
stratus doesn't exit to the south as fast as expected. Upstream
satellite observations show a decent swath of low stratus 
across the southern Canadian Prairies, so we might not get as 
much of a break in low clouds as expected. 

Main concern today is still the blowing snow potential, 
especially seeing the extent of falling snow so far this 
morning. Visibilities could drop decently low in any areas of 
blowing snow, with the highest potential of impacts in the 
southwest into the south central, and moreso in open country. 
Updated POPs in line with current radar trends. Winter Weather
Advisory and Wind Chill Advisory continue as planned.

&&

.DISCUSSION...
Issued at 352 AM CST Thu Jan 18 2024

Early this morning, the base of a shortwave trough was entering
northwest Montana, with the attendant surface trough and low 
pressure almost directly underneath. A stationary front extended
southeast of the low, connecting to an additional surface low 
in northern Wyoming. Light snow was ongoing this morning across
eastern Montana and into western and parts of central North 
Dakota, with the right entrance region of an upper jet analyzed 
over southwest North Dakota and a small band of mid- level 
frontogenesis. The remainder of the early morning hours is when
we are expecting the bulk of snow to fall in the southwest, as 
the synoptic forcing is rather progressive. Snow ratios are 
forecast to be close to 20:1, with soundings advertising both a 
very deep DGZ and relatively light surface winds. With around a 
tenth of QPF, we could end up with a quick 2-3 inches of snow, 
depending on if snow ratios end up a bit higher than 20:1. 

Snow chances taper off quickly through the morning across our 
southern tier of counties. The main concern then becomes blowing 
snow, with the fresh snowpack and surface winds increasing to be 
sustained around 25 mph and gusting to 40 mph. The highest potential 
for areas of blowing snow is in the southwest, where highest 
accumulations are expected. However, a separate, shallow upper 
wave will drop south from Canada this evening and overnight, 
bringing a 20-30% chance of snow to much of the north and 
central. With breezy winds continuing through the night, we 
could see patchy blowing snow across much of the forecast area, 
especially as light snow is falling. We did nudge winds down 
tonight from the deterministic NBM, with a known high bias for 
nocturnal events that have warm air advection. 

A Wind Chill Advisory was already in effect for most of 
northern North Dakota through the morning for wind chills as low
as 35 below. Since sustained winds will be elevated through 
today and tonight, there will not be much recovery in wind 
chills. Therefore, we elected to extend this advisory through 
Friday morning. We also went ahead and issued a Wind Chill 
Advisory for remaining counties across central North Dakota that
are not included in the Winter Weather Advisory, valid at 6 PM 
CT tonight and continuing through Friday morning. The Winter 
Weather Advisory mentions the dangerous wind chills so did not 
add on another advisory to these counties. 

Temperatures will stay cold on Friday as the upper wave brings in 
one last reinforcing shot of Arctic air, with highs staying in the 
single digits. Friday night into Saturday will be one last night of 
highs well below zero, before an upper ridge building to our west 
will start a more significant warm up through the weekend. Saturday's
highs will range from the single digits east to lower 20s west,
although paired with breezy southerly winds. 

As the ridge flattens and upper flow turns more zonal, we start to 
warm up more substantially next week, with the NBM 25/75th spread 
showing a small but consistent warming trend through Thursday, 
paired with small spread that indicates high confidence in 
temperatures. Average highs for this period are in the lower to mid 
20s across the forecast area, with high (>70%) confidence in all 
areas seeing a max temperature above freezing by Wednesday. Chances 
for precipitation next week look relatively low, with potentially 
some weak shortwaves moving through the mean zonal flow, but NBM 
probabilities for anything more than a few hundreths of QPF are low 
at this time.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1208 PM CST Thu Jan 18 2024

Currently, low and mid level clouds are passing through the area, 
bringing MVFR ceilings to multiple terminals. The ceilings on these 
cloud decks are raising above and below the MVFR threshold, and will 
likely continue to do so through most of the TAF period. There may 
be a brief period where ceilings lift later today, however a 
secondary push of stratus and light snow will lower ceilings once 
more through the second half of the TAF period.

Gusty northwesterly winds will bring about a concern for reduced 
visibilities due to blowing snow. Visibilities across the far 
southwest are anticipated to drop to below 2 miles, however the 
terminals likely to be affected by reduced visibilities will be KDIK 
and potentially KBIS for the next 6 to 8 hours. Brief moments of IFR 
and LIFR visibilities will be possible at these terminals as well. 
Northwesterly winds will mostly be 15 to 20 kts sustained, with 
gusts up to 30 kts, beginning to decrease near the end of the TAF 
period.

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
Wind Chill Advisory until noon CST /11 AM MST/ Friday for 
NDZ001>005-009>013-017-018.
Wind Chill Advisory from 6 PM CST /5 PM MST/ this evening to 
noon CST /11 AM MST/ Friday for NDZ019>023-025-034>037-046>048-
050-051.
Winter Weather Advisory until 6 AM CST /5 AM MST/ Friday for 
NDZ031>033-040>045.

&&

$$

UPDATE...Besson
DISCUSSION...Jones
AVIATION...Besson