Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 191126 AAA
AFDLBF

Area Forecast Discussion...UPDATED
National Weather Service North Platte NE
526 AM CST Fri Jan 19 2018

.SHORT TERM...(Today and tonight)
Issued at 345 AM CST Fri Jan 19 2018

Very low mixing heights Thursday limited high temperatures to the
40s in most areas. This was the result of high cloudiness blocking
the sun. The models show high clouds continuing today and the
temperature forecast undercuts guidance by several degrees. The
forecast is for highs in the 50s to near 60 across Swrn Neb and this
forecast could be optimistic given the affect of cloud cover on
mixing observed Thursday. There may be breaks in the cloud deck
along and south of Interstate 80.

Lows tonight fall into the 20s using a blend of bias corrected
guidance. High cloudiness will continue and the models show a
baroclinic leaf forming across Nrn Neb and SD.

.LONG TERM...(Saturday through Thursday)
Issued at 345 AM CST Fri Jan 19 2018

Not much change from 24 hours ago, the models still suggest that a
western conus trough will move across the southwest on Saturday and
deepen rapidly.  A closed low is shown to form which the models
track into western Kansas on Sunday.  Strong Q-G forcing and fgen
banding with the system will result in widespread accumulating snow
fall across the forecast area.  The models also suggest jet coupling
and indicate influence from a TROWAL with areas of slantwise or
upright convection in the fgen banding.  All this sets the stage for
the potential of heavy snowfall.  Complicating the forecast is that
the models show a zone of EPV reduction/slight mid level drying as
the northwest Nebraska FGEN band begins to falter and the new band
begins it/s genesis.  An argument can made for an area of freezing
drizzle across the Sandhills and our east in advance of the
accumulating snow.   While the models have a rather good grasp on
the large scale, some of the finer details still need to be
addressed.  That being said, the most likely locations of the
heaviest snowfall appear to come first across northwest Nebraska and
later over our eastern zones, basically tied to the fgen banding.
Confidence has increased sufficiently that we felt the need to issue
a winter storm watch for these areas. The watch had to be broken
into several segments to attempt to time the finer features of when
the banding or potential freezing precip will occur/end.  A somewhat
glaring "headline hole" is seen across our southwest.  We debated
keeping things simple and including those southwest Neb counties in
the watch, but after collaboration with our neighbors from the
west/southwest, we deemed that confidence was not sufficient for the
inclusion into the watch at this time.  Note that any slight wobble
could place SW Neb in the prime spot for banded snow, so don`t
discount this area.

The rapidly deepening low will promote areas of blowing snow Sunday
afternoon through Monday as north wind gusts in excess of 25 mph
develop.  The blowing snow and the potential impacts will be
considered in any upgrade to an advisory or warning.

Snow totals, will continue to follow the overall blended model
guidance for this forecast cycle since the system is still basically
offshore.  This suggests a general 3-7" of snow accumulations across
the CWA.  These values will change.  Areas will see less, areas
under the strong FGEN where convective influences are strong would
certainly see more.

The system will pull east of the CWA by Monday afternoon, with
mainly dry conditions forecast.  We did trend  temperatures for next
week downward from the guidance as we expect widespread snow
cover.

&&

.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
Issued at 526 AM CST Fri Jan 19 2018

A developing storm system across the Wrn U.S. will continue to
spread high cloudiness across Wrn and Ncntl Nebraska today and
tonight. VFR is expected all areas during this time.

&&

.LBF WATCHES/WARNINGS/ADVISORIES...
Winter Storm Watch from Saturday evening through Sunday evening
for NEZ004-005-094.

Winter Storm Watch from Sunday morning through Monday morning
for NEZ006>010-025>029-037-038-059-070-071.

&&

$$

SHORT TERM...CDC
LONG TERM...Jacobs
AVIATION...CDC



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