Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 192130
AFDLBF

Area Forecast Discussion
National Weather Service North Platte NE
330 PM CST Thu Jan 19 2017

.SHORT TERM...(This evening through Friday)
Issued at 330 PM CST Thu Jan 19 2017

Tonight...Forecast challenge is fog. Today the stratus field and
dense fog became more widespread than expected, and the stratus has
been slower to erode this afternoon. Forecast is trended toward the
NAM solution with the expectation that while the surface high
pressure over the area weakens areas of fog will redevelop tonight
question becomes how far west and how dense. Across the north
central from Custer through Boyd the temp and dewpoint spread is low
with not much to go to saturate. Winds will remain light overnight
and will go with a Dense Fog Advisory from Midnight CT to 10 am CT
Friday for areas generally east of a line from Oconto to Naper.

Tonight the cloud coverage will range from mostly clear in the far
northwest where temps will drop into the teens to mid 30s east into
the north central where widespread clouds are expected. As temps
fall impacts from the fog and patchy drizzle over the north central
may lead to slick roads again in the morning. There is the potential
the fog advisory may need to be extended into the southwest as
well.

.LONG TERM...(Friday night through Thursday)
Issued at 330 PM CST Thu Jan 19 2017

The primary focus in the extended periods is centered on the snow
chances early next week. The models continue to prog the potential
for heavy snow accumulations within the region.  Light snow chances
remain tomorrow night and early Saturday morning as well.

First the light snow chances.  The latest projections suggest a
closed low will lift northeast from western Kansas Friday.  The
lifting low will help induce two areas of precipitation.  The first
will be tied to an area of mid-level fgen across eastern portions of
the cwa, the other is in an area of mid-level q-vector convergence
across our west and southwest.  For both areas dry layers will need
to be overcome before precipitation is realized at the surface.  The
latest projections suggest trace to as much as a few hundreths qpf
with the system, which would translate to a dusting to possibly as
much as a few tenths of an inch of snow with most of that over our
eastern and northwestern zones.  It needs to be stated however that
PWATS tomorrow evening are on the order of four tenths to as much as
a half of an inch, which is high this time of year, will need to
keep monitoring. The system pulls northeast of the cwa early
Saturday leaving just a slight chance of light snow across our north
through the morning hours.

Early next week a longwave trough will move into the western conus.
A strong jet will induce the formation of an area of low pressure,
which the models show to impact the forecast area with rain and
snow.  The recent GFS trend of the formation and track of the h5 low
is north.  The heaviest accumulations now look to impact those
communities mainly along and north of highway 2 with much lesser
amounts for areas south.  The ECMWF has slightly trended north as
well and is slightly weaker, but still shows good snow accumulations
for the heart of the cwa. The ensembles are all over the place. This
latest curve lowers confidence greatly, especially since the track
of the low is much more nebulous than yesterday.  That being said
there`s still enough confidence to keep high end chances or likely
pops across much of the cwa early Tuesday, but with lighter forecast
snow amounts for most places.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1245 PM CST Thu Jan 19 2017

Forecast challenge is areal coverage of fog tonight. Model
differences creates low confidence in spacial coverage of the fog
with higher confidence along and east of a line from North Platte
to Ainsworth. A boundary will move southeast with the eventual
placement to create LIFR conditions to the east or southeast.
Further northwest to include Valentine VFR conditions will
continue. The LIFR conditions over the southeast half of the area
will begin to lift between 15Z to 18Z.

&&

.LBF WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory from midnight tonight to 10 AM CST Friday for
NEZ007-009-010-026>029-038.

&&

$$

SHORT TERM...Keck
LONG TERM...Jacobs
AVIATION...Keck



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