Area Forecast Discussion
Issued by NWS Grand Forks, ND

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FXUS63 KFGF 061604

Area Forecast Discussion
National Weather Service Grand Forks ND
1004 AM CST Tue Dec 6 2016

Issued at 948 AM CST Tue Dec 6 2016

Blizzard warning now in effect across the all of eastern ND minus
Sargent, Ransom and Richland counties as winds are slowing
increasing with the center of the low pressure system now between
Thief River Falls and Roseau. Gusts 50 to 55mph have been measured
from Cando to Langdon down to Devils Lake, Cooperstown and Valley
City airports. Winds will continue to strengthen to the east of
this corridor with widespread white out conditions. Def zone snow
band will continue all day in the northern valley and slowly
weaken gradually expanding to the east. Did extend the end time
for winter headlines until midnight with MAV/MET guidance trending
higher and longer on winds this evening.

UPDATE Issued at 718 AM CST Tue Dec 6 2016

Blizzard conditions have now reached an area including Devils
Lake...Cooperstown...and Valley City. The latest RAP/HRRR/NAM
guidance suggests the SFC low should begin to slowly propagate
east/southeast. Timing of current blizzard headlines in good
shape...along with overall forecast. Interesting that snow ratios
from overnight have been around 20:1...and this snow fell with
minimal wind so sampling should be mostly pure.

Where the heaviest snow has fallen...and in addition to the
blowing snow concerns...significant drifting snow will be a major
impact...and may start to mention this in our statements.


.SHORT TERM...(Today and tonight)
Issued at 418 AM CST Tue Dec 6 2016

Main concern will be the high impact winter storm/blizzard ongoing
or developing. Incoming model guidance...including CAMS...are in
excellent agreement. Round 1...heavy snow...has unfolded as
expected. Round 2...blizzard...looks to be on track. The main
challenge will be timing and track of the sfc low and exact timing
of the stronger winds moving in from the west. Strong upper
low...and associated sfc low continues to deepen and will stall
near Hallock (northern valley)...then slowly propagate
east/southeast after 15z. The associated strong deformation zone
will become oriented north to south...and then slowly propagate
east. Already high snow ratios will become higher as a colder
airmass advects into the region. The steep mid-level lapse rates
that led to the 1 to 2 inch per hour snowfall rates overnight no
longer exist...but given the deformation zone along with high snow
ratios should lead to at least a couple more inches of snow area
wide...and likely up to 6 or 7 more inches of snow where forcing
is strongest (near or just east of the valley?).

Anyway...blizzard/whiteout conditions the main impact today.
Strong winds combined with falling snow and what is already on the
ground will lead to whiteout conditions...especially in open
areas. Kept the same timing which still should be close...but may
adjust some minor details if/when conditions warrant.

Extended winter weather advisory to the south of the blizzard
warning with strong winds combined with falling snow leading to
some visibility issues in open areas.

Details that might change with future updates...With the surface
low stalling and propagating east a tad slower...areas near the
northern valley and adjacent portions of Minnesota may experience
a slight delay in blizzard onset. Also...current headlines expire
at 6pm which may need to be extended into the evening hours.
Last...blizzard warning may need to be extended to cover the
southern valley or Fergus Falls area if snow rates become heavy
enough that far south.

.LONG TERM...(Wednesday through Monday)
Issued at 418 AM CST Tue Dec 6 2016

Zonal flow develops with quick moving shortwaves. The strongest
model signal for accumulating snow is around the Saturday/Sunday
period...although confidence in details are low. Temperatures
definitely colder...although near normal the main highlight. With
the baroclinic zone near the region...confidence with winter
storms may be lacking until a day or two beforehand.


.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
Issued at 718 AM CST Tue Dec 6 2016

EXPECT IFR conditions in either ceilings or visibilities through
the period. Northwest winds will increase in GFK/FAR today to
20-35 kts with DVL seeing gusts to 45 kts. BJI and TVF will be
near the surface low and see a south to southwest wind gradually
shift to the west later today.


ND...Winter Weather Advisory until midnight CST tonight for NDZ049-

     Blizzard Warning until midnight CST tonight for NDZ006>008-

MN...Winter Weather Advisory until midnight CST tonight for MNZ017-

     Winter Weather Advisory until noon CST today for MNZ002-003-022-

     Blizzard Warning until midnight CST tonight for MNZ001>004-007-

     Winter Storm Warning until midnight CST tonight for MNZ005-006-

     Winter Storm Warning until noon CST today for MNZ001-004-007-008-



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