Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 180541 AAB
AFDLBF

Area Forecast Discussion...UPDATED
National Weather Service North Platte NE
1141 PM CST Fri Nov 17 2017

.SHORT TERM...(This evening through Saturday)
Issued at 325 PM CST Fri Nov 17 2017

A cold front moved through early in the day, shifting winds to the
north and holding temperatures a few degrees cooler than they could
have been given the warm nose that showed up on the morning
sounding. North Platte could have easily seen highs approaching 70
if we could have fully mixed out.

Tonight, a reinforcing cold front will drop in from the north. Gusty
north winds will return along with the front and will continue
through the night.

The main forecast problem will be precipitation type and snow amount
this evening and tonight. It is relatively warm and the surface is
relatively warm so there will be a long period of rain and rain/snow
mix and there will be an eventual changeover to snow in most areas
but the snow will have trouble sticking unless a good band sets up.
The fact that most of the precipitation will be falling in the
overnight hours increases our chance for snow accumulation a bit.

The models are all bringing in a good band of frontogenesis moving
from the northwest to the southeast late this evening. There will
also be a healthy amount of QG forcing along the front side of an
upper level trough as it swings through from 00z through 12z. So any
moisture that we do have will be maximized in this environment.
Another challenge is model inconsistency. For example, the latest
NAM puts a storm total of 6 inches of snow over North Platte while
most of the other models place the most snow in the Sandhills and
they seem to max out at 4 inches which is still on the high end
given how warm it is. The most reasonable scenario would be for 2
inches of snow or less across the sandhills...Cherry, Sheridan,
Brown, Rock, and Keya Paha Counties with less than an inch
elsewhere. The changeover to snow is less certain as you go south of
the Interstate so little to no accumulation is expected there.

The back side of the trough swings through tomorrow with downward
forcing expected to keep the wind machine going for much of the day.
However, this will cut off any remaining precipitation chances.

.LONG TERM...(Saturday night through Friday)
Issued at 325 PM CST Fri Nov 17 2017

The forecast is dry Saturday night through Friday with just one cold
front Monday night and Tuesday. Upper level energy continues to
huddle over Nrn Canada and Ern Siberia and this anomalous pattern
should continue to steer storm systems through Canada.

The model guidance has come in cooler with lows Sunday Morning. A
blend of Guidance plus bias correction produced lows in the teens
and 20s. Bias correction raised lows a couple of degrees. The SREF,
NAM and GFS show precipitable water near or below 0.20 inches with
light west winds and clear skies supporting strong radiational
cooling.

The other cold morning would be next Wednesday. The models came in
slightly west and a bit slower with the track and progression of a
1033 mb arctic high pressure system moving through the Upper
Missouri valley. The ridge axis Wednesday morning is over ern Neb
which supports lows in the teens across ncntl Neb. Wrn Neb gets
south winds around the periphery of the ridge with warmer lows.

The slower progression of the high would keep Wednesday cool with
highs in the 50s west and 40s east. Tuesday is the coolest day with
arctic high pressure backing into wrn and ncntl Neb. Highs Tuesday
are expected to rise into the upper 30s east and upper 40s west
which is a degree or two cooler than the previous forecast.

Overall, the temperature forecast continues to use is a model blend
plus the previous forecast plus bias correction. Warming trends are
obvious Sunday and Monday and again Thursday and Friday. Highs these
four days are expected to rise into the 50s and 60s.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1137 PM CST Fri Nov 17 2017

Scattered showers over western Nebraska through the early morning
hours may mix with or change over to snow. Cigs generally in the
VFR categories over southern Nebraska with no restrictions to
visibility. Some MVFR cigs over the north with precipitation
ending from the northwest to southeast through the early morning
hours. Northwest winds will increase after sunrise and gust to
near 30kts through the afternoon with skies clearing.

&&

.LBF WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

SHORT TERM...Allen
LONG TERM...CDC
AVIATION...Power



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