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FXUS63 KFGF 221937
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
137 PM CST Fri Nov 22 2024

.KEY MESSAGES...

- Snow is expected Sunday and Monday mainly north of HWY 200 with
the highest chances for 1" or more along the Canadian border.

- Colder air for next with sub zero wind chills.

&&

.DISCUSSION...
Issued at 137 PM CST Fri Nov 22 2024

...Synopsis...

A stark pattern shift is in store for the coming week with a
continental polar airmass expected to slide south into the
northern plains. Prior to this arctic intrusion however a couple
waves traverse the international border and bring chances for
accumulating snow through Monday. Precip chances diminish for
the remainder of the week though intermittent flurry chances
remain through the course of the week with a cold Thanksgiving
weekend anticipated.

-Snow Chances

A weak 500mb wave is traversing southern Manitoba and western
Ontario today producing some elevated echos on radar this
morning around 10k ft but dry air below has prevented anything
from reaching the surface. Not to say zero flakes have been
observed but they are likely few and far between amounting to no
more than a quick dusting as echos scoot east at 50kts leaving
little time for accumulations. Cloudy skies tonight as a
stubborn inversion traps a humid airmass, via melting snow,
near the surface keeping stratus in place for most of northwest
Minnesota especially along the eastern gradient of existing
snowpack. Another 500mb wave then tracks from near Calgary into
the Winnipeg area by the late weekend bringing another shot at
precipitation. This wave may bring a chance for freezing
drizzle Sunday morning as the low levels saturate between -4C
and -8C with dry air in the DGZ preventing ice crystal
formation above. This highest chances for any nonfreezing
drizzle would be across the Devils Lake Basin and into northeast
North Dakota. The main uncertainty is how deep sfc saturation
can develop with the top of the layer near the -8C to -10C
mark, right at the threshold of where crystal formation would
begin. By Sunday afternoon a saturating DGZ would end any threat
for non snow ptypes with a 40% for 1" north of HWY 2 and up to
70% chance along the Canadian border through Monday evening.

-Colder Airmass

Behind these weekend snow chances we shift from progressive
shortwave troughing amid zonal flow to a northwest flow pattern more
typical of mid winter. As evidenced this morning by lows in northern
British Columbia, Alberta, and the southern Yukon Territory in
the minus 10s to minus 20s, a cold airmass already exists to
tap into in North America and northwest flow across the
Canadian prairies is the ideal way to quickly and effectively
transport it south. Digging troughing out of the arctic circle
moving into the Hudson Bay region will provide sinking via
negative vorticity advection on its backside helping to prevent
modification (warming) of the airmass on its way south. Current
probabilities of sub 0 lows are 40% for any given morning
beyond Tuesday with the highest chances in central North Dakota.
Through this period we remain on the eastern periphery of 850mb
ridging keeping winds from going calm especially later in the
period past Wednesday. Unfortunately we all know it wouldn`t be
so bad without the wind but factoring it in we arrive at wind
chills potentially as low as the minus teens by the end of the
week.

Thankfully aside from the colder temperatures there does not appear
to be any notable precipitation chances to disrupt Thanksgiving
travel in the immediate region. Considering having an extra blanket
or two in the car just for good measure is never a bad idea however.
Winter has arrived at least for the near term.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1123 AM CST Fri Nov 22 2024

IFR to LIFR in MN taf sites through next couple hours with
improvement to MVFR/VFR tonight. VFR for ND sites through the
period with IFR expanding again in the form of low stratus over
MN taf sites for the overnight into morning hours Saturday with
a current forecast for BJI to stay IFR through 12z. Winds
variable and hold low confidence on direction but struggle to
crest 10kts.

&&

.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.

&&

$$

DISCUSSION...TT
AVIATION...TT