Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 100029

Area Forecast Discussion
National Weather Service North Platte NE
629 PM CST Mon Jan 9 2017

.SHORT TERM...(This evening through Tuesday)
Issued at 258 PM CST Mon Jan 9 2017

Upper level shortwave ejects out of the Central Rockies tonight,
pushing a strong lee side trough off of the Front Range and through
the forecast area. The HRRR has been suggesting some light QPF as
the system moves through, however the advection of a dry mid-level
airmass off of the mountains will make it difficult for any
precipitation to reach the ground. Strong 850mb winds in the wake of
the front will help promote some degree of boundary layer mixing
overnight and a moderation to temperatures at the surface. The
inherited low temperature forecast looked good and made minimal
changes. The only notable adjustment would be in the Platte River
Valleys of southwest Nebraska where models have shown some
decoupling toward the early morning hours. In that situation, light
drainage westerly drainage winds down the valley and snow pack would
likely lead to cooler lows than surrounding areas.

Guidance was too aggressive with temperatures today, which leads to
lower confidence in the warmer MEX/MAV output for Tuesday that has
much of the area into the upper 40s and low 50s. Although more
sunshine is expected tomorrow, 850mb temperatures will only be in
the 0C to 5C range. Have elected to remain conservative with the max
temperature forecast for now, especially in areas with snow cover
where diurnal boundary layer mixing may be limited.

.LONG TERM...(Tuesday night through Monday)
Issued at 258 PM CST Mon Jan 9 2017

00z Wednesday and beyond.  Surface high pressure will build south
behind a cold front on Wednesday.  The strongest CAA associated with
the high will target northern Nebraska where highs in the lower
teens are likely Wednesday afternoon.  Southwest Nebraska is
expected to rise into the lower 30s with the arrival of the front
expected mid-morning.  The models continue to key on a light qpf
signal across our northern zones Wednesday as weak easterly upslope
works in conjunction with a disturbance and upper level jet support.
The general consensus suggests a few hundreths qpf, which would
yield a half inch or so light fluffy snow.

A re-enforcing shot of Arctic air arrives on Thursday which will
continue the below average trend of temperatures, but the forecast
is largely dry.  Highs in the teens and 20s are probable with lows
in the single digits and low teens.  We develop southeast to
southerly flow in the lower levels on Friday, which will promote a
slight warm-up, but in the upper levels the models diverge some on
the handling of the next weather system.  The general idea is that
west to southwest flow will develop with a shortwave bringing
accumulating snow to the central Sandhills Friday.  At this point an
inch or two snow accumulations are possible.  Beyond Friday
uncertainty in the forecast amplifies.  The Euro camp brings a solid
wave just south of the cwa late Saturday and Sunday.  This solution
accumulates light snow across our southern and southeastern tier.
The GFS is largely dry with the system well south of the area.
Ensembles support the southern track, but the uncertainty warrants
at least a slight chance, will leave the blended builder forecast as
is for now.  The Arctic airmass will be replaced with a airmass of
Pacific origin.  Warming temperatures are expected for the weekend
and early next week.


.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 628 PM CST Mon Jan 9 2017

Abundant mid and high level clouds will continue to stream into
western and north central Nebraska over the next 24 hours.
Ceilings will generally range from 10000 to 20000 FT AGL. Some
precipitation aloft is possible with the cloudiness, but none is
expected to reach the surface.


Issued at 258 PM CST Mon Jan 9 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 will help alleviate some of the ice
issues through mid-week, but colder temperatures late week are
forecast. Will continue a RVS for both sites until the ice issues
are fully resolved.




LONG TERM...Jacobs
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