Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 022135
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
335 PM CST Fri Dec 2 2016

...Light Wintry Mix of Precip Possible late Tonight thru Tomorrow
Evening with Sizable Uncertainty Even within 24 hrs...

.SHORT TERM...(This evening through Saturday)
Issued at 335 PM CST Fri Dec 2 2016

Aloft: A shortwave ridge was exiting the fcst area at 19Z and
thick cirrostratus was following quickly behind. A shortwave trof
was over the Nrn Rockies. This trof will approach late in the day
and cross the fcst area tomorrow night.

Surface: High pres was over the Cntrl/Nrn Plains today. This high
will drift into the Midwest tonight with return flow developing
here tomorrow as a weak Clipper emerges into Sask.

Tonight: P-M/cloudy this evening...but becoming cloudy after
midnight. Before we even deal with next weeks potential...there is
plenty of uncertainty with this system. The NAM conts to be a wet
outlier. Just to show what we have to deal with...the 12Z NAM has
a max of 0.48" QPF over Jewell Cty while the last 2 runs of the
GFS and EC only have .10" there and along and E of a line from
Osborne KS to Geneva NE.

Believe we`ll see a semi-continuous shield of snow overtake the
area from the SW after midnight. There could be a brief period of
frzg rain at the leading edge. It`s low probability...but it`s not
zero.

My greatest concern with this system is that we chance of precip
is not properly depicting the real probability. My preference
would be to have the probability 60% or greater...as I do think
precip will fall. It`s just that amounts will be light.

Low temps were raised svrl degs above the prvs fcst due to
increasing clouds.

Sat: The batch of snow will mix with and change to rain as temps
warm. The potential for frzg rain will end by midday as temps
climb above frzg. A little snow could mix back in Sat eve as the
low-lvl temp profile cools. Most of the precip will be E of hwy
183.

High temps were lowered a few degs from the prvs fcst.


.LONG TERM...(Saturday night through Friday)
Issued at 335 PM CST Fri Dec 2 2016

...Turning Bitterly Cold for Wed-Thu with Current Indications for
Low Snowfall Amts Tue night into Wed...

Aloft: WNW flow Sun will transition to SW flow Mon as an
anomalously deep trof developing over the W Mon-Tue and out over
the Plains Wed-Thu. 500 mb Heights will be very low...nearly 2
standard deviations below normal Wed-Thu. This will coincide the
the core of the coldest air. Heights will rise Fri as a shortwave
ridge arrives.

Surface: Weak high pres will move thru KS/OK Sun with
strengthening return flow into Mon. The polar front will be
plunging S and will cross the fcst area Mon eve. The arctic front
will plow thru late Tue night or Wed morning. Very strong arctic
high pres will then build in with the BL flow becoming
increasingly anticyclonic Wed-Thu. A piece of this high will break
off and drifts E of the region Fri with return flow developing.

Snow: we cont to closely monitor this situation Tue night into
Wed. The trend over the past couple days and multiple models and
model runs is for less/low snowfall amts. Based on past experience
...this makes sense. Most of the time we need the leading edge of
the cold air to be quasi-stationary just to our S for us to get
hvy snow. When cold air surges far S of the fcst area...it is
very hard to get heavy snow here because the sfc low is forced S
along the main front. Even if the EC is right...the weak low fcst
to move along the front will be over SE OK Wed. The GFS/CMC don`t
even have it and that`s why they output little or no QPF.

All this being said...this potential event is still 4.5 days away.
The spread seen in the GFS ensemble shows there are several
features that the GFS member results are sensitive too. The main
ones are the magnitude of the height falls over the Wrn USA and
the magnitude of the ridge over the E Pac. As the models resolve
these uncertainties...the fcst could still change. So stay tuned.

A quick look at all 51 EC ensemble members show a decreasing
number fcstg warning-level snowfall.

Cold: temps will start in the teens Wed morning and will probably
go nowhere over S-cntrl Neb (i.e., remaining in the teens). Wind
chills will be sub-zero Wed and Thu mornings on blustery N winds.

&&

.AVIATION...(For the 18Z KGRI/KEAR TAFS through 18Z Saturday)
Issued at 1157 AM CST Fri Dec 2 2016

Significant Wx: MVFR CIGs expected after 15Z/Sat. There is a
chance for IFR -SN after 12Z.

This Afternoon: VFR with invading cirrostratus CIGs from the SW.
Lgt and vrbl winds. Confidence: High

Tonight: VFR. Multi-layered mid-high CIGs gradually descend to
around 10K ft. Lgt and vrbl winds. Confidence: High

Sat thru 18Z: CIGs will gradually lower thru 5K ft down to 2K ft
after 15Z. A couple fcst models are indicating -SN will move
in...but others are not. Lgt and vrbl winds will become SW and
gradually increase close to 10 kts. Confidence: High in MVFR CIGs
but confidence is low on potential for SN.

&&

.GID WATCHES/WARNINGS/ADVISORIES...
NE...None.
KS...None.
&&

$$

SHORT TERM...Kelley
LONG TERM...Kelley
AVIATION...Kelley


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