566 
FXUS63 KFGF 211220
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
620 AM CST Tue Dec 21 2021

.UPDATE...
Issued at 610 AM CST Tue Dec 21 2021

Clipper continues its fast push across the area this morning.
Snowfall amounts here in Grand Forks are between 1.6" at the
airport and 2.5" here at NWS FGF with Fargo receiving 1.7" with
all observations valid at 6am. Michigan ND CO-OP reported 3 inches
which is the most amount reported so far this morning. Will
continue to see intensity tapper off across eastern ND and the RRV
as mid level forcing has shifted over west central MN. Snow
amounts on track and adjustments to the forecast were minimal with
pockets of clearing working into NW ND and flurries diminishing. 

&&

.SHORT TERM...(Today through Wednesday)
Issued at 336 AM CST Tue Dec 21 2021

Concern and impacts in the short term will be on ending time of
snowfall this morning. System continues to evolve and quickly 
track east this morning. Mid level warm air advection forced 
snowfall is currently impacting most of the area with obs 
indicating Vsby mainly in the 1 to 3 mile range with western areas
already seeing 4 to 6 mile ranges as snow is beginning to taper 
off there with the 700mb WAA waning. Will see the back edge 
quickly push to the east with an end time in the valley in the 6am
to 8am time frame. Snowing in GF over the past 3 hours with a 
total around 1.5" reinforces the idea that the strongest returns 
in the progressive warm air regime are capable of about a half an 
inch an hour once saturation occurs. Given the thermal profile 
from a sounding at GFK earlier this evening, snow formation is 
occurring in the dendritic growth zone aiding to high snow to 
liquid ratios or a light and fluffy snowfall. Forecast on track 
for a widespread 1 to 3 inches with some higher amounts in the 
west central MN where residence time is a bit longer as 850mb WAA
persists. Thus will keep the winter weather advisory as is wrt to
placement and time with 2 to 4 inches there.

Behind the clipper system there will be some westerly winds that 
increase this afternoon to near 20mph across eastern ND west of 
the valley where some patchy blowing and drifting of snow is 
possible. A reduction of visibility is not expected. A clearing 
line will work into eastern ND this afternoon but highs will still
hold in the low teens today. 

SFC high passes south of the area with ridge axis sliding across
the CWA this evening which will allow a drop in temps quickly
after sundown with temps then rising as winds and clouds increase
overnight. Lows across the area will be near zero then with weak 
warm advection Wednesday temps will climb into the teens north and
low 20s south. 

.LONG TERM...(Wednesday night through Monday)
Issued at 336 AM CST Tue Dec 21 2021

For the extended period, look for continued unsettled weather as H5 
flow shifts from northwesterly to southwesterly over the course of 
the next week. Clipper systems will traverse the baroclinic zone, 
with ensembles indicating chances for snow on Thursday, then once 
more on Sunday. The confidence in exact timing and impacts of these 
systems remains quiet low, as run to run variation is rather 
pronounced.  

Wednesday night into Thursday, look for a chance for light snow as a 
weak shortwave pushes across the area. Accumulations will be light, 
generally less than one inch; however, slick roadways are likely 
Thursday morning across much of the area. The remainder of the day 
will be quiet, with warmer temperatures advecting into the region.

Christmas Eve: Another fast moving shortwave is indicated by a 
limited number of ensemble members, as well as the main global 
deterministic models. Confidence remains very low, however, as there 
is much run to run variation in solutions regarding precipitation. 
Current guidance brings light snow into west-central and northwest 
Minnesota, with little accumulation potential; however, other, less 
likely, solutions bring heavier impacts across much of the region. 
In either case, much colder air returns to the CWA Christmas Eve 
into Christmas Day.

Christmas Day: Weather related impacts across the forecast area will 
be minimal headed into Saturday. Much colder air encompasses the 
Northern Plains as highs only reach the single digits to lower 
teens. Winds will be out of the north through much of the day at 10 
to 15 mph, gusting to near 20 mph. The primary concern Christmas Day 
will be frigid wind chill values.

Heading into Monday, unsettled weather prevails as the H5 flow 
pattern becomes southwesterly. There remains much uncertainty at 
this time, however, confidence is slowly increasing regarding a 
potentially impactful system that works across the Northern Plains 
during the first half of next week.

&&

.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
Issued at 541 AM CST Tue Dec 21 2021

Lingering light snow and VSBY restrictions along with timing of
clearing today will be the main aviation concerns. MVFR conditions
ongoing with clouds and snow associated with passing clipper will
improve this morning from west to east with VFR conditions
expected for most of the TAF period thereafter. Winds will turn to
the west for the afternoon and southwest overnight. 

&&

.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...Winter Weather Advisory until noon CST today for MNZ022>024-027-
     028-030>032.

$$

UPDATE...JK
SHORT TERM...JK
LONG TERM...Lynch
AVIATION...JK