Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 182121
AFDLBF

Area Forecast Discussion
National Weather Service North Platte NE
321 PM CST Sat Nov 18 2017

.SHORT TERM...(This evening through Sunday)
Issued at 301 PM CST Sat Nov 18 2017

The dry northwest flow pattern will persist through tonight and
tomorrow as upper ridging continues over the western Conus.
Increasing subsidence and westerly downsloping winds will allow
for a warming trend with highs well into the 50s if not lower 60s
for most locations Sunday. The dry conditions will however allow
for a good radiational event overnight. As winds go light,
guidance suggests reading in the teens and lower 20s.

A deepening lee trough will begin to stack the pressure gradient
across western portions of the CWA on Sunday. Mixing however
will be kept below h85, thus not looking overly gusty. Peak wind
gusts should remain at or below 20 mph Sunday afternoon, which is
good as the westerly downsloping flows advects some drier air
across southwest Nebraska. The latest guidance suggests afternoon
minimum relative humidity nearing 20% west of highway 61 across
southwest Neb. The latest NAM and GFS indicates an increase of
high level clouds across the CWA during the afternoon hours. Right
now will maintain PC skies, but BKN or OVC may be possible.

.LONG TERM...(Sunday night through Saturday)
Issued at 301 PM CST Sat Nov 18 2017

Minimal sensible weather concerns in the long term period. The
main stories include: moderate breezes Monday with elevated fire
weather conditions, cooler temperatures Tuesday with highs near
15 to 20 degrees colder than Monday, and well above-normal
temperatures area-wide Thanksgiving Day and Friday. Otherwise,
scant chances for any precipitation through Saturday.

The large scale pattern early Sunday night will feature a broad
mid-level ridge extending from the Southwest CONUS into the
Canadian Prairie provinces with west northwest flow overhead. An
upper level shortwave trough will track Sunday night-Monday from
Alberta to far southern Manitoba. The associated surface low will
move into Ontario Monday night and will drag a cold front across
the area. The pattern then becomes fairly amplified Monday night
and Tuesday. An amplified upper-level ridge will be in place over
the western CONUS Tuesday with a trough located from Ontario to
the western/central Gulf Coast.

High temperatures continue to rise with warmer highs forecast on
Monday compared to Sunday ahead of a frontal passage. Modest
downsloping winds are anticipated. BUFKIT soundings depict 850 hPa
temperatures rising generally to 8-13 C, along with sufficient
mixing which should combine with adequate insolation. This should
promote highs in the lower-mid 60s (about 14-18 degrees above
normal). In addition, the combination of modest breezes and drying
will be conducive for elevated fire weather conditions. However,
fire weather conditions are expected to be sub-critical given
marginal afternoon humidity at this time. Conditions will need to
be monitored nonetheless.

While no precipitation is forecast, cloud cover is expected to
increase Monday night. Cooler air will push into the region Monday
night. 850 hPa temperatures ranging largely 5 to -6 C from west-
east Tuesday. Resultant forecast highs are mostly near seasonable
values, except for the lower-mid 30s anticipated in far north
central NEB.

The large scale pattern Tuesday night through Thursday will be
characterized by an upper-level ridge dominating the pattern over
the western CONUS. Thereafter the 500 hPa ridge will flatten
Thursday night-Friday as a shortwave trough moves across the top
and into the Upper Great Lakes. Well-above normal temperatures are
expected by Thursday and Friday area-wide, about 16-20 degrees
above seasonable normal values. Cooler temperatures are then
expected Saturday attributable to another cold front Friday
night.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1141 AM CST Sat Nov 18 2017

Post frontal northwest wind will continue to be breezy until
sundown, but then subside and back to westerly overnight.
Thereafter winds should remain light through the remainder of the
forecast period. Skies are forecast to be mostly clear outside of
some streaming high clouds at 25000 feet or above. Overall
forecast confidence is high due to solid short term model
agreement.

&&

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

$$

SHORT TERM...Jacobs
LONG TERM...ET
AVIATION...Jacobs



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