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647
FXUS63 KFGF 130554 AAC
AFDFGF

Area Forecast Discussion...UPDATED
National Weather Service Grand Forks ND
1154 PM CST Thu Dec 12 2019

.UPDATE...
Issued at 1152 PM CST Thu Dec 12 2019

Warm air advection nosing into south central ND will prompt snow
to spread into southeast ND a bit sooner than previously
anticipated, so adjusted precipitation chances to account for
that.

UPDATE Issued at 1021 PM CST Thu Dec 12 2019

Latest radar data and surface observations show scattered flurries
across portions of the forecast area late this evening. A broad
area of light snow continues to progress east through western and
central ND. Adjusted precipitation chances slightly to better
align with latest CAM timing.

UPDATE Issued at 711 PM CST Thu Dec 12 2019

Added a chance for flurries this evening in the northern RRV,
associated with a weak mid level shortwave moving through and weak
WAA developing ahead of the approaching system. Low level stratus
will continue to spread across northwest MN this evening as well.

&&

.SHORT TERM...(This evening through Friday night)
Issued at 254 PM CST Thu Dec 12 2019

Cold front is dropping south into central Saskatchewan mid
afternoon with light snow with it. This is associated with a
stronger short wave moving southeast around the western Hudson Bay
low. There is a short wave moving thru western Montana with light
snow developing ahead of it over parts of Montana and southern
Saskatchewan. The northern system will track southeast and
eventually meet up with the eastern moving system but this will
occur not in our area but in NW Ontario where heavier snow is
possible.

In our area, we will be focused on track and strength of upper
wave to the west and associated surface low. Both upper wave and
sfc low will move east-southeast and be near the ND/SD/MN border
area by 18z Fri. Overall trends from operational GFS/NAM is for a
bit weaker forcing, upper level divergence than the prev day. Some
frontogenetical forcing is present for a brief time in the 850 mb
warm advection in the 12-15z time period. Other than this a
general light snow will fall into the evening.

Main issue will be impact from north winds as they develop on the
backside of the system Friday late aftn and evening and continue
Friday night. Snowfall will be mainly over with and wind potential
is not huge, but gusts 30-35 mph is possible in the Red River
valley. Drifting more of an issue, but blowing maybe too if winds
are stronger and able to lift fresh snow. Something to monitor as
if advisory is needed it will be for this aspect and not snow
amounts.

.LONG TERM...(Saturday through Thursday)
Issued at 254 PM CST Thu Dec 12 2019

12Z Sat - 00Z Mon

Concerns in this period will be winds Sat morning and drifting snow
issues. Departing system will still affect the region Sat morning.
Increased winds a bit for Sat morning as pressure gradient remains
up. Main impact is the potential for drifting snow which could make
some roads slippery. Winds will slowly settle down Sat morning. Cool
air will remain across the Northern Plains for Sat. Another cold
night is expected Sun morning with lows around 20 below with high
pressure overhead. Some moderation in temps is expected Sun but
mainly for the western zones.

Mon - Thu

Split flow is forecast across North America with northern stream
over southern Canada/northern states and southern flow across the
southern states.

Long wave trough across central Canada and the Central Plains will
shift over southwest Hudson Bay with the rest of the trough shifting
north and east as long wave ridge builds over the western US by Thu.
The ECMWF ensemble was a slightly faster than the GEFs.

Concern this period are weak short waves moving through the flow for
late Sun, Mon, and Wed. Little or no snow expected with the short
waves. However some light snow is indicated for the northeast zones
on Wed. Ensemble means bring in cooler air for late Mon/early Tue.
Temperature moderation may be possible for late in the period.
Little impacts are expected at this time.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1152 PM CST Thu Dec 12 2019

Ceilings will deteriorate overnight, becoming MVFR to IFR
ceilings and visibilities by 12z as snow spreads eastward into the
region, starting at DVL and FAR early this morning. Low
confidence in the duration of IFR ceilings and visibility, but do
expect at least MVFR (or lower) ceilings to prevail through
much of Friday, beginning to improve by Friday evening at all but
KBJI.

Winds will be light and southeasterly through mid morning Friday,
turning northwest as a cold front passes through by Friday
evening. Could see some reduced visibility from blowing snow with
gusty winds behind the front, especially at KFAR Friday evening.

&&

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

$$

UPDATE...BP
SHORT TERM...Riddle
LONG TERM...JH
AVIATION...BP