Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 172124

Area Forecast Discussion
National Weather Service North Platte NE
324 PM CST Tue Jan 17 2017

.SHORT TERM...(This evening through Wednesday)
Issued at 324 PM CST Tue Jan 17 2017

Temperatures remain the main forecast challenge over the next 24
hours, although, the very slight chance of ground fog south of
Interstate 80 is a minor concern.  For tonight, the temperature
forecast is a blend of bc data with the inherited forecast and
latest numerical data. Clear skies are expected as a broad area of
high pressure settles to the southeast.  Light winds from the west
will have little mixing effects on the atmosphere as the earth
radiates. Lows are forecast to fall into the teens for most
locations, but single digits should prevail over Sheridan and Garden
Counties as lighter winds are forecast for the higher eastern
panhandle.  For Wednesday, we continue to see west to southwest flow
over much of the CWA as as weak lee surface trough deepens.  Like
today, temperatures will be above average.  The warmest readings
will be over the drier central Sandhills and northern Nebraska where
highs in the lower 50s are forecast.  Elsewhere mid to upper 40s
will prevail.  The latest guidance may not be warm enough, we did up
the forecast values several degrees, but after the lower 50s today,
there may be room for improvement yet.  We didn`t want to go too
warm as the thermal profiles over the cwa remain largely similar
Wednesday afternoon.

There are hints of patchy ground fog south of Interstate 80
overnight tonight where evaporation and snow melt is underway today.
Given the soundings suggest marginally supportive saturation at KLBF
and KIML and the fact that unfavorable southwest to west winds of 5-
7 mph are expected overnight, we felt that fog development is
unlikely, but will be watched.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 324 PM CST Tue Jan 17 2017

The model consensus continues to show h850mb temperatures between 5C
and 7C Thursday. The caveat is that return moisture will be hanging
out across Ern Neb and this could present an opportunity for morning
fog or stratus east of along or east of highway 83 as indicated in a
very low cloud forecast procedure. Sfc winds are south in this area
also which would limit vertical mixing. Thus the temperature
forecast Thursday has been marked down a few degrees east of 83 to
accommodate a disruption in the heating cycle.

There is little change with the track of a weak upper level
disturbance lifting through the Ern Neb Friday night and
Saturday...perhaps a slight shift west toward highway 83 but rain
and snow chances are still mostly east of 83. The GFS has backed off
on the chance for freezing rain and now suggests rain changing to
snow but the rain is falling at night on ground that is frozen. So
there is still some chance for freezing rain. The forecast is for
rain changing to snow because that is the most likely outcome at
this point in the forecast. The GFS model sounding near Ainsworth
supports this forecast.

30kt-40kt h850mb winds develop Sunday in the wake of a strong storm
moving through the Srn Plains. This would equate to sfc winds of 15
to 25 mph across Wrn and Ncntl Neb.

A strong storm system will move through the Cntl Plains Tuesday.
The 06z and 12z GFS model runs now split the system in two showing a
strong lead nrn stream wave across the Nrn Plains and the second
wave moving through KS. The result is a 150 mile shift southeast
with the best forcing across KS and SE Neb...a glancing blow
for Wrn and Ncntl Neb.

The forecast still carries a likely or even categorical snow chance.
This is because (1) this will be a large storm system which should
produce some measureable snowfall throughout Wrn and Ncntl Nebraska.
(2) the GFS ensemble continues to show the best focus across Wrn Neb
and it is a compromise with the nrn tracking 00z and 12z ECM solns.
(3) CPC has outlooked the region for heavy snow so there is that


.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1120 AM CST Tue Jan 17 2017

VFR anticipated across the entire outlook area through the 18z
forecast period. That being said, warm temperatures today will
allow for some melting and evaporation of the recent
precipitation, there are hints that ground fog may form south of
a KIML to KBBW line overnight. Light winds and dry air aloft
would enhance the fog potential, but the westerly component of the
wind usually hinders fog formation. At this point the probability
of ground fog too low for TAF forecast consideration, but will be




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