Area Forecast Discussion
Issued by NWS Hastings, NE

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019
FXUS63 KGID 211957
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
157 PM CST Sat Jan 21 2017

...Significant Uncertainty on Precip Potential with the System
Fcst Next Tue-Wed but For Sure Turning Colder Behind It...

.SHORT TERM...(This evening through Sunday)
Issued at 157 PM CST Sat Jan 21 2017

Aloft: A very complex trof was over the Cntrl/Wrn USA with
multiple embedded shortwave trofs. A shortwave ridge was over the
Cntrl Plns between the small low that moved thru yesterday...and
the next one in the process of forming over TX. This low will
remain well S of the region thru tonight...leaving the fcst area
in quiet wx.

Surface: It`s highly unusual...but broad low pres was over the
Plns. There really was no high pres in the wake of yesterday`s
system... just a hint of a ridge across MO/KS/NE. Cyclogenesis was
underway over the TX Panhandle. This low will head E across OK and
into AR tonight...remaining safely to the S.

Tonight: Increasing clouds. Becoming p-m/cloudy. Another night of
low temps about 15F above normal.

Sun: p-m/cloudy in the morning...then clearing in the afternoon.
Another mild day...similar to today but a little cooler over
S-cntrl Neb.

NW winds will gust 18-24 kts.


.LONG TERM...(Sunday night through Saturday)
Issued at 157 PM CST Sat Jan 21 2017

Aloft: NW flow will gradually strengthen Sun into Sun night as a
shortwave ridge approaches ahead of a new trof moving onshore in
the W. The ridge will move thru Mon. The Wrn trof will be complex
with multiple embedded vort maxima...one of which will induce
cyclogenesis Tue and the formation of a new low. This low will
head E across Neb/KS Tue. A broad trof will be left in its wake
Wed-Fri. Fri its axis will pass thru the fcst area followed by N
flow as a Wrn ridge/Ern trof evolves.

Surface: Weak/small high pres will build in Sun and then cross
the fcst area Sun night. Lee cyclogenesis will commence over CO
Mon along with warm frontogenesis down into the Srn Plns. There
are still substantial timing and intensity diff`s in the last 2-3
runs of the NAM/EC/GFS/CMC and the 09Z SREF mean...but the basic
idea is that this low will eject ENE across KS Tue. Colder air
will be drawn S into the region Wed as this low heads into the
GtLakes...and high pres expands from N-S thru the Plns. Another
cold front will probably move thru Thu followed by high pres Fri-
Sat.


Some Sensible Wx Details...

Mon: Quiet. Another nice day. Probably averaged p/cloudy most
locations. Temps still 10-15F above normal.

Tue-Wed: Kept the fcst pretty generic. There is significant
uncertainty on where/when/how much pcpn will fall and what type(s)
of pcpn will fall.

Models: The 00Z/06Z/12Z GFS are faster and weaker. The 06Z/12Z
NAM were Srn outliers...ejecting the low into the OK Panhandle.
The 00Z/12Z EC/CMC were deeper and slower...with the CMC the
slowest outliers. 460 mi separate the fastest GFS run and slowest
CMC run at 06Z/Wed. Interestingly...the 12Z run of each model was
consistent with its prvs runs...maintained separate camps.

QPF: Models are all over the board...ranging from little or
nothing...to a light or moderate winter storm for parts of the
fcst area. This system is not occurring in a completely cold
environment. Some areas will probably see some rain.

This system will struggle to produce pcpn...especially in the
warm sector. It will be moisture-starved and most if not all of
the pcpn will be collocated with the strongest lift N of the low.

Bottom line is don`t take our fcst literally yet. The models need
to line up better and converge on a solution.

There are a couple things that we do have higher confidence on:

1) It will be windy with this storm...probably windier than we
currently have in the fcst...especially if the deeper EC/CMC
verify.

2) Turning colder Wed-Sat behind this low...but not excessively
so. Temps return near or slightly below normal.

Can`t rule out some flurries or a brief snow shwr or two...
especially as the upr trof comes thru Fri.

&&

.AVIATION...(For the 18Z KGRI/KEAR TAFS through 18Z Sunday)
Issued at 1128 AM CST Sat Jan 21 2017

Significant Wx: None.

This Afternoon: VFR with just a few shreds of cirrostratus off in
the distance. Lgt W winds will become vrbl. Confidence: High

Tonight: VFR with increasing 20-25K ft clouds...possibly becoming
CIGs for a time. Lgt and vrbl winds eventually become NW 8-12 kts.
Confidence: High

Sun thru 18Z: VFR with decreasing high clouds. NW winds increase
to around 15 kts after 15Z. Confidence: High

&&

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

$$

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



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