National Weather Service Raw Text Product

Displaying AFOS PIL: AFDBIS Received: 2021-11-09 12:13 UTC


942 
FXUS63 KBIS 091213
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
613 AM CST Tue Nov 9 2021

.UPDATE...
Issued at 607 AM CST Tue Nov 9 2021

GOES Nighttime Microphysics shows extent of fog in southwest North
Dakota, possibly nudging into the south central this morning.
Based on cameras and coverage depicted on satellite imagery,
coverage is somewhat patchy, but has lowered visibility at
Hettinger down to 1/4 mile. An SPS was issued to address fog this
morning for this area. Fog will gradually dissipate mid-morning 
as boundary layer mixing increases after sunrise.

&&

.SHORT TERM...(Today through Wednesday) 
Issued at 427 AM CST Tue Nov 9 2021

Warm and mostly sunny today. Then a front will bring a chance of
rain tonight and tomorrow, with light snow mixed in possible far 
north.

A shortwave ridge crosses the region today, with a surface high 
giving way to pressure falls in the west. This morning, relatively
higher surface dew points and the surface high in place have 
contributed to fog developing in the southwest. High-res guidance 
has fog spreading into the south-central with the eastward 
progression of the surface high this morning, which seems 
reasonable and was added to the forecast grids. 

Mostly sunny and warm today, with breezy southeast winds west and
central. Highs in the low to mid 50s expected, and upper 40s in
the Turtle Mountains. Upper level clouds will be on the increase 
from the west this evening as a trough and front approach. Light
rain can be expected along the front as it moves through late
tonight through Wednesday, with some snow mixing in over the
north. Accumulations will be light if any, though up to around an
inch will be possible in the Turtle Mountains. West/northwest
winds pick up behind the front on Wednesday as well, as post-
frontal boundary layer mixing and increased low level flow combine
to produce winds of 15 to 25 mph and gusts to around 40 mph.

.LONG TERM...(Wednesday night through Monday)
Issued at 427 AM CST Tue Nov 9 2021

A deep upper low will bring colder temperatures, strong winds, and
good chances for rain and snow to start the long term forecast
period. The best chances for accumulating snow will be in the far
north-central including the Turtle Mountains.

Wednesday night, the aforementioned trough will deepen and close
off with the influence of an upstream upper level jet streak
nosing towards the trough axis. Theta-e advection wrapping around
the cyclone will likely produce snow for much of the state
Wednesday night through Thursday night (tapering off west to
east), while strong low level flow and a tight pressure gradient 
will create likely advisory criteria winds through the day 
Thursday. 

The challenge with forecast snowfall totals lies in surface 
temperatures as well as the synoptic development of the upper
level trough, as notable differences in guidance continue to 
exist in how progressive the upper low will be. The deterministic ECMWF
continues to depict stronger theta-e advection further west and 
later into Thursday night and Friday morning compared to other
global guidance, which would potentially produce more notable 
accumulating snow further south. However among its own ensemble 
members and the other deterministic models, there is a healthy 
spread of solutions depending on the eastward progression of the
low that keep uncertainty high at this time. Based on the most 
likely location of stronger upper level forcing and cold air at 
the surface, as well as analysis from a probabilistic blend of 
guidance, the northeast including the Turtle Mountains will be the
most likely areas for accumulating snow, with several inches 
possible in the Turtle Mountains. Further south and west the 
spread between percentiles grows rapidly after the low-end 25th 
percentile, indicating strong clustering of solutions that keep 
snow accumulation low for most of the area, but does indicate the 
higher end potential for more accumulating snow from the northwest
through the southern James if the westward solution becomes 
reality. Blowing snow will also be a concern, especially while
falling in areas of higher snowfall rates. At this time this also
is most likely in the far north central. 

Friday will feature colder temperatures while snow lingers in the
east. Strongest winds will shift central and east, and daytime
highs are forecast to remain from the upper 20s to low 30s. In the
far west winds should taper off with clearing skies as high
pressure builds, and highs may push into the upper 30s. Northwest
flow sets up through the weekend, with decent agreement in an
embedded wave and chance of precipitation on Saturday. 

&&

.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
Issued at 607 AM CST Tue Nov 9 2021

Fog this morning has lowered visibilities in the far southwest,
and has gradually spread into the south central. As of 12Z this
has remained south of KDIK-KBIS, but may briefly impact these
areas still this morning. Included VCFG in these TAFs due to high
uncertainty of fog impact on visibility. VFR today with breezy
southeast winds west and central. A front will approach from the
west late tonight which should bring MVFR ceilings and light rain.
This should arrive at KXWA-KDIK after 09Z, and KMOT-KBIS by around
the end of the 12Z TAF period, but the impacts of this front more
likely after 12Z. 

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...AE
SHORT TERM...AE
LONG TERM...AE
AVIATION...AE