Area Forecast Discussion
Issued by NWS Hastings, NE

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198
FXUS63 KGID 042311
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
511 PM CST Sun Dec 4 2016

.SHORT TERM...(This afternoon through Monday)
Issued at 330 PM CST Sun Dec 4 2016

Aloft: Heights were rising in the wake of the departing shortwave
trof that brought the snow to the area yesterday. Heights were
already falling over the Pac NW. This was the leading edge of the
blast of bitter arctic cold on the way. A low- amplitude shortwave
ridge will move thru tonight with SW flow developing tomorrow as
strengthening shortwave trof swings out of the Nrn Rockies and
into the Dakotas by evening. This trof will effectively carve out
the longwave trof that will deliver the arctic cold.

Surface: High pres was over NM/TX and will race E into the OH Vly
by daybreak Mon. Meanwhile...the fcst area will remain in return
flow and strong WAA ahead of the first strong cold front. It was
currently making its way thru the Pac NW. It will arrive here and
cross the fcst area from NW-SE 12pm-6pm.

Rest of This Afternoon: Beautiful. The swath of snow from
yesterday was melting but it won`t be totally gone by tomorrow.
This will cont to impact temps. It was 36F at HJH at 2 pm while
HSI was 47.

Tonight: Mostly clear this eve...then increasing clouds after
midnight...especially over S-cntrl Neb. Low temps will be about 8F
above normal.

Main concern for tonight...does fog form where snowmelt has
occurred? Am concerned that winds will drop off early this eve and
temps will rapidly radiate past the cross-over temps. So included
patchy fog from K82 over to JYR and HJH.

Mon: P-M/cloudy. The GFS/EC suggest a few sprinkles are possible
after midday N and W of the Tri-Cities. It`s not in the fcst yet
...but something for the next shift to consider. The last mild
day for quite a while. Just as today most locations will be 10F
above normal.

It`s always hard to know how much to acct for snow cover and wet
ground. So high temps are low confidence S and E of the Tri-
Cities.

.LONG TERM...(Monday night through Saturday)
Issued at 330 PM CST Sun Dec 4 2016

Aloft: A low-amplitude shortwave trof will move thru Tue within
the larger broad trof. A shortwave trof and strong 130 kt jet
streak will be diving down the backside of the trof. The flow will
become increasingly cyclonic until this trof moves thru KS Wed
afternoon/ eve. The flow will turn NW in its wake Thu-Fri with
gradually rising heights...and Fri it will turn anticyclonic until
a low-amplitude ridge is fcst to move thru Fri night. Low
amplitude will prevail Sat- Sun with the next shortwave trof fcst
to come out of the Pac NW and arrive here Sat.

Surface: High pres will build in Mon night and Tue while the
arctic air begins draining into the Nrn Plains. Lee cyclogenesis
will begin Tue night over CO...but the first cold front will be
along the OK/KS border by dawn Wed...and cont dropping S. This
will overwhelm the low and force it S away from the forcing aloft.
The arctic air arrives Wed. Stronger high pres will build in Thu
night into Fri. Return flow develops Fri and we should have a weak
system moving thru Sat...but chances for precip are minimal with
no moisture to work with.

A few sensible wx details...

Not much to say that hasn`t been said the last few days. No big
changes.

1) The coldest air of the season thus far arrives Wed-Thu. The
last time it was as cold as we are fcstg...Feb 13th.

2) Winds will not be as bad as they could be with this kind of air
mass. But any wind with this kind of cold will be too much. The
strongest winds will occur 3am-3pm Wed.

3) Still looking at a light snow event Tue night into Wed. As of
now the model consensus offers 2-4" S and W of the Tri-Cities and
a trace to 1" N and E. The map is on our website in the Top News
of the Day. This will be updated every 12 hrs around 4 AM/PM.

The last 5 runs of the EC ensemble mean have averaged 2-4" along
and S of Hwy 136 with the highest amts over Nrn KS.

A suppressed sfc low is usually not good for big snowfall here.
Just too much cold air overwhelming.

Uncertainty is high next Sat-Sun...but the lack of moisture and
zonal flow means any precip that might occur would be minor with
many places seeing little or nothing.

The CPC 6-10 day outlook suggests temps will remain colder than
normal into next week (10th-14th).

&&

.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Monday evening)
Issued at 507 PM CST Sun Dec 4 2016

VFR conditions are forecast through the taf period. A period of
low level wind shear is expected overnight and look for an
increase in mid level cloud cover.

&&

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

&&

$$

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



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