Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 261154

Area Forecast Discussion
National Weather Service North Platte NE
654 AM CDT FRI AUG 26 2016

...Updated Aviation Section...

.SHORT TERM...(Today and tonight)
Issued at 349 AM CDT Fri Aug 26 2016

Main concerns this forecast package in the short term were
precipitation and thunderstorm chances, temperatures, and fog
potential overnight. A broad mid-level long wave trough currently
extends from the Canadian Prairies down into the central Rockies and
Intermountain West/Central Great Basin while a broad high remains
positioned across the SE CONUS. Western and north central NE will
undergo weak mid-level height falls today as the aforementioned
trough moves into the Central Plains. A short wave trough and
associated vort max will move from eastern CO into central NE this
afternoon with current guidance in decent agreement with this
feature. The window where this disturbance will provide better large
scale ascent to the forecast area appears to be late this morning
and afternoon. Meanwhile, a surface lee side low will develop near
the Front Range as the upper trough moves east today. In that
interval, surface high pressure currently in the eastern portion of
the Central Plains will be shifting to the Upper Great Lakes. Winds
will be turning from light and easterly early in the morning to more
southerly by mid morning with an increase in speed.

Current thinking is the best chances for precipitation will begin in
western NE mid-late morning. This will be followed by increased
chances for precipitation spreading eastward into central NE in the
early-mid afternoon. As moisture gets transported into western and
north central NE, precipitable water will increase to 1.0-1.3 inches
in the afternoon. Similarly, moisture advection will result in dew
points rising into the mid 50s to near 60 by early-mid afternoon
across southwest and central NE. This combined with the timing of
best lift should result in showers developing and becoming more
numerous near mid morning across western NE with showers then
starting to spread into central NE in the early afternoon. In regard
to thunderstorm potential, best chances are in the far western
portion of the forecast area near the NE Panhandle. Wherein, the
transported moisture will combine with better instability, though
low, to produce a favorable environment for some thunderstorm
development. Current thinking is that thunderstorms will be more
multicells for storm mode, with 0-6 km bulk shear around 35 kts, and
will likely be moving out of the NE Panhandle based on winds aloft
and anticipated storm motion. A strong or severe storm may be
possible, with gusty winds or hail the primary threats. Showers will
be moving east across the eastern half of the forecast area by mid-
late afternoon given eastward progression and are anticipated to
start to exit the forecast area near midnight CDT. Of note, hi-res
guidance appears to be in decent agreement in the beginning of the
short-term with the various flavors of wrf that are available and
HRRR depicting similar evolution of showers and their movement
today. This, combined with the environment and synoptic set-up,
increases confidence in the short-term.

A cooler day is expected attributable to clouds and wet conditions.
Highs are expected to be 10 to 15 degree below normal near the NE
Panhandle portion of the forecast area. Elsewhere, areas of north
central NE will see highs 3 to 8 degrees below normal. Fog becomes a
concern in the early morning/late tonight given the wet conditions
expected. Following today`s rainfall, fog potential will be decent
early Sat morning that could be attributable to light winds
developing late tonight combined with decent radiational cooling
that`s expected and the amount of boundary layer moisture that will
be in place.

.LONG TERM...(Saturday through Thursday)
Issued at 349 AM CDT Fri Aug 26 2016

After a fairly active few days, high pressure will begin to
build into the high plains on Saturday. This high will remain over
the central US through much of the next several days and dry weather
will continue for the most part through mid-week. The only chance of
precipitation that looks to impact the forecast area occurs on
Sunday night as a disturbance moves across central Nebraska.
Precipitation chances with this system is only around 30 percent as
confidence in the development and track is low at this time. Even if
some showers can develop, high pressure still situated to the
northwest of the CWA will keep precipitation confined mainly south
and east of an Imperial to O`Neill line. With a a decent stable
airmass over the region, severe potential is low with any showers
and thunderstorms that occur on Sunday night.

Small disturbances are projected to move across the central plains
in the afternoon each day from Monday through Thursday, however, the
waves appear to be much weaker than Sunday`s wave. If showers can
make it into central Nebraska and overcome the stable airmass from
the high pressure system, only the extreme southeast portion of the
forecast area will be impacted. Confidence in these afternoon
showers is extremely low and therefore less than 20 POPs are in the
forecast at this time.

For the temperature forecast... high temperatures rise into the low
80s on Saturday before we return to the upper 80s and low 90s
through Thursday. Low temperatures from Saturday night through
Wednesday night will generally range from the upper 50s in the west,
where terrain influences are present, up to the low 60s across the


.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
Issued at 654 AM CDT Fri Aug 26 2016

KLNX and neighboring radars depict an area of convection that has
developed across the NE Panhandle early this morning. More
recently, within the last hour, weak convection has developed
across portions of our local forecast area in the far west.
Current thinking is that through mid morning showers and
thunderstorms will continue to develop and fill in across western
NE. This will be followed by increased chances spreading eastward
into central NE in the early-mid afternoon. In regard to
precipitation chances, confidence in showers and storms are
higher across central NE compared to far north central NE this
afternoon/evening. Showers and storms are expected to be east of
KLBF and KVTN by mid evening.

Concerns turn to fog potential late tonight-Saturday morning. Fog
will be favorable, especially across southwest to central NE, as
light winds combined with a moist boundary layer. Wherein, MVFR-
IFR visibilities with low ceilings will be possible across
portions of central and north central NE.


.LBF Watches/Warnings/Advisories...


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