Area Forecast Discussion

FXUS63 KLBF 152309
Area Forecast Discussion
National Weather Service North Platte NE
509 PM CST Fri Dec 15 2017
.SHORT TERM...(This evening through Saturday)
Issued at 310 PM CST Fri Dec 15 2017
Latest vis and IR satellite imagery shows high clouds moving into 
the Panhandle and western NEB. Latest water vapor imagery shows an 
mid-level trough moving onshore the Pacific Northwest and an ridge 
that's deamplifying extending from southern CA/Southwest US into the 
Northern Rockies. Surface analysis shows an surface trough extending 
across the western Dakotas into far western NE from a sfc low in 
Saskatchewan. Currently light westerly breezes are occurring, some 
gusting to 20 MPH in the eastern Panhandle and far southwest NEB.
Current thinking is scattered to broken high clouds will continue to 
affect the forecast area much of tonight. Meanwhile, winds will 
lessen as well. As such, fair radiational cooling conditions are 
expected given the sky cover combined with light winds. Albeit, lows 
should still read above seasonable normal values with low forecast 
largely in the upper teens to near 30. The aforementioned surface 
low is expected to weaken as it evolves and moves into the eastern 
Dakotas overnight. Of which a weak cold front will advance across 
the area late tonight-tomorrow morning. Meanwhile, the short wave 
trough will continue to move southeastward while undergoing 
amplification. The upper trough should be positioned across the 
Northern Rockies to Baja California Saturday. Clouds will spread 
across the forecast area from the small hours-late morning. While 
cooler air will sink in the area aloft at low-levels, near to 
slightly above seasonable normal highs are expected – coolest in the 
northeast Panhandle and northwest NEB. 
.LONG TERM...(Saturday night through Friday)
Issued at 310 PM CST Fri Dec 15 2017
Upper level trough will continue to dig southwest and eventually 
split over the Desert Southwest and into far northern portions of 
Mexico.  Still, as the northern piece of energy swings through early 
Sunday enough low and mid moisture will combine with northeast 
upslope flow to produce some light precipitation.  At this point 
northwestern portions of the forecast area seem to have the best 
shot at accumulating a half inch or an inch of snow with lesser 
amounts to the south and east.  Deep moisture is scarce and there 
continues to be a freezing drizzle signal for much of the Sandhills 
and portions of southwest Nebraska including I80 possibly as far 
east as Lincoln County.  Bufkit soundings show the moist layer 
extended up to just shy of minus 10C in areas, so ice nucleation 
seems unlikely save for our far northwestern portions of the CWA. 
QPF amounts are projected to be light with models trending lesser 
and lesser with each run.  Significant icing is not expected.
Will see increasing subsidence and drying conditions behind the 
shortwave for early next week.  Southwest flow returns in advance of 
the next western trough on Wednesday, which should prove to be the 
warmest day of the work week.  Will have to watch humidity values 
and wind speeds on Wednesday as I would expect guidance to be too 
low on speeds and too high on TDs.  The pattern is a quasi ridge 
breakdown, so we'll monitor.
Late next week the significant trough digs into the southwestern US 
and potentially cuts off a low while the northern stream advances 
across the Canadian border.  There seems to be some agreement with 
today's 12z run that precipitation would be realized over much of 
the forecast area Thursday of next week. In addition, the CIPS 
analogs are showing increased probability of above normal precip in 
the day 6-8 time period for much of my northwest and central 
Sandhills which increases our confidence some.  Temperatures during 
that time period will support snow as a Arctic airmass dives south. 
Light accumulations would be possible. All in all, late next week we 
should trend cooler and have some chances at precipitation. 
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 509 PM CST Fri Dec 15 2017
A cold front will move through most of western Nebraska overnight.
This will bring surface winds to the north and northeast for
Saturday as wind speeds remain below 12 kts. A broken deck of high
cloudiness overnight into Saturday, with a lowering of ceilings to
MVFR at KVTN after 21z. 
LONG TERM...Jacobs