Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 160927
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
327 AM CST Tue Jan 16 2018

.SHORT TERM...(Today and tonight)
Issued at 325 AM CST Tue Jan 16 2018

Dangerous wind chills and cold conditions associated with the arctic
high pressure system highlight the short term.

The arctic high axis extended from near Winnipeg into northeastern
ND, to between Bismarck/Jamestown to central SD/NE. Temperatures
across western and central ND ranged mainly between -26F to -10F
with wind chills mainly in the -20F to -40F range.

Today the arctic high continues moving southeast into the
central/southern plains. Warming begins in western ND with the upper
level western ridge edging eastward into the western Dakotas. This
mild Pacific air begins scouring out the dome of arctic air with
good southwest flow at h850. We are still expecting a slow warm-up
with late afternoon temps mainly from around 5 above in the James
Valley to the teens in the west. Warm advection continues tonight
with the approach of a small-scale clipper system emerging out of
the southern Canadian Rockies. Temps tonight should dip just below
zero in parts of south central ND and remain in the single digits
above zero in the west and north central.

.LONG TERM...(Wednesday through Monday)
Issued at 325 AM CST Tue Jan 16 2018

Highlights in the long term include a warming trend Wednesday
through Friday, then turning colder again Saturday through Monday.
With temperatures rising to above freezing during the day and then
below freezing at night, expect icy conditions each evening/night
and through the early morning hours Wednesday through Friday.

Wednesday:

Tuesday night the global models develop an upper level shortwave
emerging from a large low pressure system in the eastern Pacific.
This shortwave impulse moves east across the southern Canadian
Rockies Tuesday night. The shortwave emerges over the Canadian/US
Front Range by daybreak Wednesday morning and deepens into a smaller
scale closed low as it moves southeast across southern Saskatchewan
on Wednesday, and across southern Manitoba Wednesday night before
reaching Lake Superior by daybreak Thursday. The 00z GFS and ECMWF
are in good agreement with this scenario, but the 00z NAM depicts a
more northerly track (like yesterday`s 00z run did). More confident
regarding the GFS/EC track, and followed yesterday`s day shift
forecast with increasing winds a bit on Wednesday and Wednesday
night. The models depict strong low/mid level warming ahead/along
this system, and h850 westerly winds of 30-40 knots with h850
temperatures from +5C to +8C. Bufkit soundings indicate surface
westerly winds of around 20 mph with gust potential to over 30 mph
across northern and eastern ND. This will promote good mixing from
the surface to the warm air at h850...resulting in high temperatures
from the lower 30s in the James Valley and Turtle Mountains to the
mid and upper 30s farther west. Wednesday night there is a brief
period of weak cold advection behind the clipper, but Pacific air
edges into southwestern ND as an upper level ridge builds/expands
eastward from the Rockies into the Front Range. A mild January night
is expected Wednesday night with lows from 15 to 25 above zero. As
mentioned in the previous forecast discussion, melting during the
day will re-freeze Wednesday night, resulting in the potential for
icy roads and sidewalks, etc. Also mentioned previously, despite
melting and increased boundary layer moisture, the lower layers of
the atmosphere should remain unstable/mixed to inhibit any
widespread fog potential Wednesday night.

Thursday and Friday:

An upper level ridge over the Rockies moves east across the western
plains ahead of the next large-scale upper level low/trough over the
west coast. Warming continues with highs in the 30s central and
northwest, reaching the upper 30s/lower 40s southwest with a very
mild night Thursday night with lows in the 20s, and in the teens to
lower 20s Friday night. Again, the daytime melting and nighttime re-
freezing on roadways and walkways will make for icy conditions
during the nighttime and early morning hours.

Saturday through Monday:

The aforementioned low/trough west coast system develops into a
split flow longwave trough by Saturday. The base of the longwave
trough develops a southern/central plains storm system that
eventually moves northeast into the Great Lakes on Monday. Meanwhile
the northern stream portion moves across the Northern Plains as an
open wave, with another arctic high dropping south into ND following
the open wave. We are not expecting a strong surge of arctic air, as
warm advection commences again ahead of another shortwave in the
progressive flow, possibly bringing a chance of light snow to our
area on Monday.

&&

.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
Issued at 325 AM CST Tue Jan 16 2018

High pressure over the region will move southeast today. VFR
conditions are expected through the 06Z TAF period. Some clouds
north of the state will drop south at least into the northern TAF
sites of KISN and KMOT today, but upstream observations indicate
cloud layer remains above 10,000 ft. Light and variable winds this
morning will become southerly across all TAF sites by afternoon.

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
Wind Chill Warning until noon CST /11 AM MST/ today for
NDZ002>005-010>013-018>023-025-033>037-041-042-045>048-050-051.

Wind Chill Advisory until noon CST /11 AM MST/ today for NDZ001-
009-017-031-032-040-043-044.

&&

$$

SHORT TERM...JV
LONG TERM...JV
AVIATION...TWH


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