Area Forecast Discussion
Issued by NWS Hastings, NE

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804
FXUS63 KGID 151745
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
1145 AM CST Sun Jan 15 2017

.SHORT TERM...(Today and tonight)
Issued at 336 AM CST Sun Jan 15 2017

The winter storm system will make itself known today with periods of
freezing rain and sleet. Satellite imagery placed the center of the
upper low pressure system in Mexico early this morning with moisture
streaming north ahead of the system into the southern and central
Plains. An area of freezing rain developed during the late evening
in our southern zones and is lifting northeast from north central
Kansas into southern Nebraska early this morning. Slick outdoor
surfaces were reported in Rooks County between Stockton and
Plainville.

Forecast models are in good agreement with the upper low pressure
system tracking into eastern New Mexico today and then lifting to
the Oklahoma/Kansas stateline overnight. In isentropic lift ahead of
this system, we will see periods of freezing rain and sleet develop
and spread northeast. Currently the main area of widespread freezing
rain is located across southern Kansas and it will take some time
for this to work northward and it will mainly be this evening and
tonight when the brunt of the icy wintry precipitation becomes
widespread across our area. Precipitation chances increase from
south to north with time today/tonight and have kept precipitation
type as freezing rain and sleet. Short term guidance suggests temps
may edge above freezing this afternoon but have kept temps near or
below freezing given the cloud cover and increasing precipitation
potential.

It will not take much precipitation to make outdoor surfaces slick
and we have already had reports of this overnight where there was
freezing pcpn. Ice amounts of a few hundredths to two tenths of an
inch are possible today, with the highest icing expected across
north central Kansas. Additional similar ice amounts are forecast
again tonight leading to 24 hour amounts in the quarter to half inch
range possible across north central Kansas. Farther north into
Nebraska the potential for more sleet may ultimately result in lower
ice accumulations but we are still looking for totals of a tenth to
a quarter of an inch and impacts of the icing are still expected to
be significant.

For headlines, there have been no changes to what we have ongoing at
this time with an ice storm warning for the majority of cwa where
the highest ice totals are forecast (one quarter to around three
quarters of an inch) and a winter storm warning is in effect for our
western zones due to lesser ice accumulations and a combination of
wintry weather of freezing rain/sleet/snow.

In summary, the wintry precipitation will come in a few rounds with
the brunt of the wintry weather/icing moving in tonight as the
deformation band lifts north as the upper low moves into southern
Kansas.

.LONG TERM...(Monday through Saturday)
Issued at 336 AM CST Sun Jan 15 2017

Aloft: A low will be over the KS/OK border at 12/Mon...embedded with
a larger trof from the Can Prairies SW to Baja CA. This low will
move NE and be over SE Neb by 00Z/Tue...and near DVN at 12Z/Tue.
Meanwhile...the mean trof axis will move thru here Tue with another
small low possibly closing off over Neb or KS. There is uncertainty
on this. There is terrible run-to-run and model-to-model continuity
with this 2nd low. The NAM has no low...and the EC/CMC/GFS are all
in diff locations at 00Z/Wed. The 12Z/14 EC is over SW KS...CMC near
ICT and GFS near FNB. A shortwave ridge will move in Wed ngt-Thu. SW
flow then develops late Thu as a new/expansive trof moves into the
Wrn USA with multiple embedded shortwave trofs.

Surface: At 12Z/Mon model consensus has a weak sfc low over N-cntrl
OK. This low will head NE thru Ern KS into NW MO by 00Z/Tue. High
pres will quickly overtake the Cntrl Plns Mon night as the low heads
for the GtLakes. This high will drop into the Srn Plns Tue and
weaken. The Plns will be in return flow Wed-Thu until cyclogenesis
occurs and low pres emerges into KS. This low is fcst to lift N thru
Neb Fri night into Sat. Evolution of this low is low confidence due
to model uncertainty.

Some Sensible Wx Details...

Mon: at dawn a large/mature comma-shaped mass of pcpn will be over
the Cntrl/Srn Plns. A solid shield of comma head pcpn comprised of
frzg rain (ZR) and some ice pellets (IP) will be over the entire
fcst area. Between 10 am and 1 pm...the warm nose around 800 mb
should cool allowing the NW fringe of the pcpn shield to change over
to snow from Beaver City-Lexington-Ord. There could be a little IP
before complete transition to S. That cooling should progress SE to
that point that most of the pcpn should changed to S in the
afternoon.

Dry slot: with the vort max tracking just SE of the fcst area...
expect precip will end over the SE fringe of the fcst area from N-
cntrl KS up into the HJH area...and possibly as far N as JYR.
However...there could be some spotty drzl/frzg drzl as deep mstr
will remain up to 10K ft.

The snow band that evolves and curls around the Nrn/Wrn quadrants of
the low during the afternoon should fall apart and/or lift NE of the
fcst area in the 6-9 pm (00Z-03Z) time frame.

The 00Z/06Z NAM both have no lift in the DGZ by 00Z...suggesting sig
pcpn will be over by sunset. Any left over pcpn will be light.

Ice: another 1-2 tenths of ice accretion should occur mainly along
and E of Hwy 281 before changeover to S. W of Hwy 281 should be a
tenth or less as changeover will occur earlier.

Snow: Accums really depend on how quickly changeover occurs. Current
expectations are for 1-2" W of a line from Plainville KS-Hastings-
Genoa NE. Areas E of that line less than 1 inch. Best chance for 2"
Beaver City-Lexington-Ord.

Mon night into Tue AM: the fcst is currently dry. Am concerned we
may see a touch of light S if the 00Z GFS and 12Z/00Z CMC are right
about this second upr low fcst to develop. The 00Z EC came into the
NAM camp with no low. Something to watch.

Tue: Clearing. With all the ice/snow...we may be too high with temps
by 5-7F.

The rest of the week...daytime and nighttime temps much warmer than
normal as the Plains are flooded with downslope-warmed air.

The 00Z EC came in and cast more uncertainty Wed and it has support
from the 84 hr NAM.

The 146 am Extended Fcst Dscn from WPC has a good summation of what
is currently expected along with a deeper model disc.

Given the uncertainty...will not make any comments other than the
fact that this will be the warmest period we`ve seen so far in what
has been a very cold month. Odds favor any pcpn that falls Fri-Sat
being rain. Would not be surprised if we need to include some
thunder.

&&

.AVIATION...(For the 18Z KGRI/KEAR TAFS through 18Z Monday afternoon)
Issued at 1144 AM CST Sun Jan 15 2017

Ceiling/visibility/precipitation:
Confidence is high that the majority of the period will feature
either IFR or LIFR conditions, especially ceiling but with periods
of at least IFR visibility as well. In addition, off-and-on
freezing rain, possibly eventually mixing with some sleet will
continue throughout the period, with at least 10-20 hundredths of
an inch of ice accrual anticipated (possibly more). Would normally
not include so much prevailing -FZRA, but chances of it falling
the majority of the time are fairly high and want to maintain
consistency with previous issuance as well. In other words, this
looks to be a very poor aviation period overall. Right off the bat
these first few hours will probably favor MVFR ceiling before
lower ceilings prevail through especially the latter 16-20 hours.

Winds:
Surface winds should not be a major issue through the period,
especially the first 18-21 hours or so with prevailing speeds
expected to hold below 10kt and gradually turning from
southeasterly to more northerly. By the last few hours on Monday
morning, a steadier north wind will start kicking in with gusts
15+kt.

&&

.GID WATCHES/WARNINGS/ADVISORIES...
NE...Ice Storm Warning until midnight CST Monday night for NEZ062>064-
     074>077-083>087.

     Winter Storm Warning until midnight CST Monday night for NEZ060-
     061-072-073-082.

     Winter Storm Warning until midnight CST Monday night for NEZ039-
     040-046-047.

     Ice Storm Warning until midnight CST Monday night for NEZ041-048-
     049.

KS...Ice Storm Warning until noon CST Monday for KSZ005>007-017>019.

&&

$$

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



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