Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 101804
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
1204 PM CST Sat Dec 10 2016

.SHORT TERM...(Today and tonight)
Issued at 322 AM CST Sat Dec 10 2016

A band of snow associated with an upper disturbance crossing the
Central Plains was working east across northern Nebraska during the
predawn hours. Short term models are consistent with the brunt of
the snow affecting northern Nebraska with our northern counties on
the southern edge of the snow band. The Ord and Greeley areas could
see a brief period of light snow with some flurries possible
farther south but with the progressive nature of the system, the
snow will be moving out by mid morning with little if any
accumulation.

While the arctic airmass has been dislodged, extensive cloud cover
will keep temperatures in check today with readings only forecast to
edge close to the freezing mark in Nebraska, with some mid 30s
possible in north central Kansas. Southerly winds will increase
during the day as a surface trough deepens along the front range of
the Rockies.

Heading into tonight models indicate a corridor of low cloud cover
developing ahead of an approaching surface trough and cold frontal
boundary. Along the edge of the low cloud cover, the potential
exists for fog development along our western zones. If fog does
develop, visibilities are expected to improve early Sunday with
the advancing boundary.

.LONG TERM...(Sunday through Friday)
Issued at 638 AM CST Sat Dec 10 2016

...A Brief Interruption to the Cold Still on the Table Mon then
Bitter Cold Returns...

Aloft: Low amplitude W or WNW flow will prevail thru Fri. A low
amplitude shortwave trof will move thru Sun followed by another Mon.
Heights will then rise and become anticyclonic Thu or Thu night as a
more vigorous shortwave trof moves in from the Pac. This trof will
arrive here Fri or Fri night.

Surface: A weak cool front will move thru early Sun with weak
high pres briefly building over the region Sun. Return flow will
develop Sun night into Mon as the high heads E into the Midwest.
Meanwhile ...the next arctic cold front will be surging S. The
trend in the GFS/EC is for a faster arrival Mon afternoon. A small
high will drop into Neb by daybreak Tue and then depart to the E.
The next arctic front will press S thru the fcst area Tue night
with Nrn Plains high pres quickly following Wed. Return flow
develops Thu with lee cyclogenesis beginning. Newly formed low
pres is then fcst to eject into the Srn Plains Fri with an
inverted trof extending N into KS/Neb. As this low heads NE toward
the OH valley...it will yank a bitterly cold arctic air mass
S...reinforcing the cold air already in place.

A few sensible wx highlights...

As mentioned yesterday...this fast/low amplitude flow is fraught
with uncertainty as models generate light precip from a variety of
subtle vort maxima that may be on one run and not on the next...in
one model and not the other. While models may agree on the large
scale...there are significant and important diff`s in the mesoscale
details that impact the sensible wx (i.e. precip and clouds).
Regardless...this pattern does not lend itself to anything other
than minor or insignificant precip.

Fcst confidence is below average in precip/clouds. Some snow we have
mentioned may not pan out. Sun is a good example. The fcst is now
dry for Sun...where a couple days ago it looked like there was
potential for a minor snowfall. There may be other periods we
currently have dry that may need snow mentioned as those time
periods get closer. The fcst is dry for Mon...but we may need to
insert a mention of sprinkles in later fcsts.

Temps/Cold: Fcst init was raised svrl degs for high temps Mon. Used
W-model which is a blend of the 3 best-verifying guidance sources
over the last 30 days. The highest confidence portion of the fcst is
more bitter cold...with high temps averaging 20F below normal Tue-
Fri. Highs Tue will be 20-25F colder than Mon.

Expect a 3-6 hr burst of windy conditions immediately behind the
arctic front Mon afternoon/eve. The fcst doesn`t full reflect how
windy it could be just yet...but we`ve trended winds upward.

The last 5 runs of the GFS ensemble mean suggest we have 5 to
possibly 7 consecutive days with high temps in the Tri-Cities 20F
or less...starting Tue.

&&

.AVIATION...(For the 18Z KGRI/KEAR TAFS through 18Z Sunday afternoon)
Issued at 1133 AM CST Sat Dec 10 2016

Stratus is expected to linger across the local area through much
of the period...possibly briefly touching MVFR levels
occasionally through the late afternoon hours. Gusty
southeasterly winds will also continue through the afternoon
hours...before diminishing some around sunset...and then becoming
gusty and northwesterly behind a cold front tomorrow. Could see
some low level stratus...below MVFR levels...behind this front
tomorrow...but confidence is low enough so did not include it in
the 18Z TAFs.

&&

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

$$

SHORT TERM...Fay
LONG TERM...Kelley
AVIATION...Rossi


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