Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 100530 AAB

Area Forecast Discussion...UPDATED
National Weather Service North Platte NE
1130 PM CST Sat Dec 9 2017

.SHORT TERM...(This evening through Sunday)
Issued at 327 PM CST Sat Dec 9 2017

Persistent ridging across the western CONUS will continue through
Sunday, with dry northwest flow aloft on the eastern side of the
ridge across the central and northern plains. Northwest winds
continue to persist at the surface as well. Winds will actually
increase a little tonight as a Pacific cold front crosses the area.
Mild Pacific air in the wake of this front will keep low
temperatures mild, in the upper 20s to lower 30s. Where winds
decouple in lower spots like river valleys, it will be a bit colder
in the lower 20s.

Full sunshine Sunday, plus a surge of warmer air aloft, with 850mb
temperatures rising to between 8C and 10C, will boost highs into the
lower 60s across portions of the area. Did shave a few degrees off
highs across northern Sheridan county where there is some lingering
snow cover. Winds Sunday will remain northwest, and with deep mixing
gusts to 20 to 25 mph are likely.

.LONG TERM...(Sunday night through Saturday)
Issued at 327 PM CST Sat Dec 9 2017

The main forecast concern revolves around a potential high wind
event Monday. This is the result of a cold front and upper level
support from a low diving through the upper midwest. The model
consensus continues to show 65-85kt winds at 700mb and mixing
heights to around 800mb. The strongest winds aloft precede the cold
front moving through early Monday morning.

The latest guidance and 500m AGL winds are 25 to 30 kts. Bufkit
suggested gusts to 45-55 mph. The feature of interest is 1.5 PV
anomaly swinging through ncntl Neb Monday afternoon. The pressure of
that surface lowers to 600 mb which could be sufficient to mix the
stronger winds aloft surface-ward. It is also evident that the
corridor of strong winds aloft is collocated with the lowest PV
pressure which approaches nctl Neb late in the aftn.

The models tend to miss these types of high wind events and in fact,
only the HRRR model and occasionally the RAP model have shown
consistent success forecasting the wind gusts. Since these models
only run 18 to 24 hours in advance, the predictability of a high
wind event at this time is speculative. The forecast is for 25 to 30
mph winds with gusts to around 50 mph. NAM and GFS Bufkit was the
basis for the wind gusts.

A second cold front will move through either Wednesday or Wednesday
night followed by a third Friday night. These fronts and the one
Monday may have sufficient moisture for isolated rain or snow
showers...mainly across ncntl Neb.

The temperature forecast uses the model blend plus the previous
forecast plus bias corrected guidance for highs in the 40s and 50s.
Bias correction had little impact on high temperatures and lowered
min temperatures a degree or two.

None of the models indicate any kind of direct arctic air moving
into ncntl and wrn Neb. Mostly pacific air is indicated with a
chance for brief arctic influence late next week. Thus the
temperature forecast is for above normal highs and lows.


.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1127 PM CST Sat Dec 9 2017

Low level wind shear will be main concern for aviation across
western Nebraska. As winds at the surface decouple and become
light winds at 2kft AGL will continue at 40 to 50kts out of the
north. Winds will increase across the surface after 12z on the
10th. Skies will be mostly clear with VFR cigs.


Issued at 327 PM CST Sat Dec 9 2017

Conditions for range fire development Sunday will be elevated across
most of wrn and ncntl Nebraska. Conditions will be elevated across
Frenchman basin Monday.

15 percent or less relative humidity develops for 2 hours across the
Frenchman basin Sunday and around 20 percent across areas generally
along and west of highway 183. Winds gusts 20 to 25 mph Sunday
afternoon and nearly full sun are expected with highs in the upper
50s to lower 60s.

Strong winds with gusts to 45 mph and humidity near 20 percent
develop for a few hours Monday afternoon across the Frenchman basin.
Temperatures rise into the mid 50s and nearly full sun is expected.
This represents an elevated condition for range fire development.




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