Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 131200 AAA
AFDLBF

Area Forecast Discussion...UPDATED
National Weather Service North Platte NE
600 AM CST Fri Jan 13 2017

.SHORT TERM...(Today and tonight)
Issued at 352 AM CST Fri Jan 13 2017

Mid level wave moving east this morning with snow ending across the
north central zones. Little additional accumulation expected. 1047mb
surface high centered over Minnesota early this morning keeping
western Nebraska in southerly flow. Brisk winds over northern
Nebraska where gradient is tighter. Clouds to continue over western
Nebraska today and will inhibit solar insolation. Temperatures
expected in the 20s with some 30s over southwest Nebraska. Upper
closed low off the west coast continues southward through the day on
Friday and Friday night, This pushes a ridge north into western
Nebraska. Moisture increases into western Nebraska with southerrly
flow. Temperatures fall into the low teens.

.LONG TERM...(Saturday through Thursday)
Issued at 352 AM CST Fri Jan 13 2017

The main concern in the extended forecast remains the potential for
accumulating mixed precipitation Sunday through Monday.  The
probability of ice accumulations is increasing, especially for our
southeastern zones.

12z Saturday the system will largely be off the coast of Northern
Baja, but over the next 24 hours the system will move east reaching
far southwest New Mexico.  Sunday night into Monday the low will
move north northeast across western Kansas then exit to the east of
the forecast area by early Tuesday.  The track of the low will allow
for several periods of qpf.  Pops increase early on Sunday from
south to north as large scale lift increases with the approaching
low.  However the highest chances arrive around 12z Monday as the
low lifts north across western Kansas, placing eastern and southern
portions of the cwa in a well defined deformation band.

The models continue to wobble with the track of the h5 low.  This
wobbling lowers forecast confidence as even the slightest shift
impacts the thermal profiles greatly. That being said, considering
tonight`s runs and with the the previous model trends, we felt it
was time to include freezing rain into the forecast.  The warm nose
supports melting with T/s of greater than 0C in a 3-4ft layer while
surface T`s are at minus 1C or colder.  In addition, periods of
sleet are possible as near sfc T`s fall below 0C at about 1k feet
AGL.  For now will keep snow and freezing rain as the primary
precipitation type as the difference with impacts between snow and
sleet are minimal. The best chances of freezing rain comes Sunday
through early Monday with the WAA in advance of the system, snow is
primarily favoured in the deformation beyond 12z Monday.

Accumulation amounts of snow and/or freezing rain are still largely
up for debate, but what is certain is that several consistent model
runs have shown the potential of moderate snow in the deformation
zone.  The deformation favours southwest through north central
Nebraska, including much of I80 and Highway 83.   Our northwestern
zones will largely miss out on this action unless the trend
continues west. The freezing rain forecast is much more
questionable, but the general consensus indicates the greatest
potential for icing is generally east of a KOGA to KANW line with
the heaviest and potentially most impactful over our southeastern
zones.

No changes are planned to our current watch, but now considering the
potential of freezing rain, the start time of any upgrade may need
to be upped some 12 hours.  Bottom line, this system has the
potential to make someone`s day really bad, but uncertainty remains.
Any wobble could make a big difference.  Given the current track
much of our CWA will be impacted by this storm with the potential of
major travel disruptions. Stay up to date on the forecast.

Once the system lifts northeast a modified Pacific airmass will be
in place leading to average and above average temperatures.  The
next shot at QPF comes late in the extended, but confidence is low
due to poor model continuity.

&&

.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
Issued at 559 AM CST Fri Jan 13 2017

Mainly mid and high clouds are expected over western Nebraska
today and tonight. Southerly winds will become light and variable
tonight. Visual flight rules expected.

&&

.HYDROLOGY...
Issued at 352 AM CST Fri Jan 13 2017

Frazzle ice continues to impact area streams and rivers.  The North
Platte River above Lake Mcconaughy has seen fluctuations due to
minor ice jamming the past several days, most notably at Lewellen
and Lisco.  Warmer temperatures helped alleviate some of the ice
issues early this week, but colder temperatures have returned.  Will
continue a RVS for both sites until the ice issues are fully
resolved and upgrade if needed.

&&

.LBF WATCHES/WARNINGS/ADVISORIES...
Winter Storm Watch from Sunday evening through Monday afternoon
for NEZ007>010-025>029-036>038-057>059-069>071.

&&

$$

SHORT TERM...Power
LONG TERM...Jacobs
AVIATION...Power
HYDROLOGY...Jacobs



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