Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 172030

Area Forecast Discussion
National Weather Service North Platte NE
330 PM CDT Wed May 17 2017

.SHORT TERM...(This evening through Thursday)
Issued at 316 PM CDT Wed May 17 2017

The first of two upper level lows is currently tracking northeast
across the region. Rain is covering much of the Sandhills and
north central NEB this afternoon in deformation area on immediate
west side of the upper low which is centered in eastern Nebraska.
As the low tracks northeast away from the area this evening,
drier air in the mid levels will end the precipitation early.
Elsewhere, isolated showers and thunderstorms are ongoing in a
corridor of modest instability across far southeast WY-far
northeast CO. There is potential that these showers/thunderstorms
could move onto far southwest NEB this afternoon. However, no
strong or severe storms are anticipated.

Otherwise, the next upper low will be centered across northern
Utah by early Thursday morning and will move slowly to near the
the CO/UT border by late afternoon. Low/mid level warm air
advection will aid development of scattered showers across western
Nebraska during the day Thursday, otherwise farther east it
should remain dry. A surface low will be deepening across the
TX/OK panhandle during this time. This will keep the surface flow
from the northeast, which will advect cooler air in from the
northern plains. Most areas will not get out of the 50s for highs
Thursday as a result.

.LONG TERM...(Thursday night through Wednesday)
Issued at 316 PM CDT Wed May 17 2017

The main sensible weather highlights in the long term period are
below normal temperatures, coolest Friday and Saturday, and wet
conditions early on. Friday`s highs will be around 20-30 degrees
below seasonal normal values then only rebound some on Saturday,
still about 15-20 degrees below normal.

The large scale pattern will feature a long wave trough that will
be affecting the western and central CONUS as it moves
northeastward through the weekend. The trough will initially
extend from the Northern Rockies south through the Four Corner
region with a closed low near/just east of the Central Rockies
then gradually lift into the Central High Plains by Friday.
Thereafter the trough and closed low will lift into the Upper
Mississippi Valley by Saturday. Cool and wet conditions are
expected to prevail in the beginning of the period through
early/midday Saturday as the large scale trough lifts
northeastward. Precipitation chances ramp-up tomorrow night into
Friday as large scale forcing for ascent combines with low-level
isentropic ascent and moisture transport. A few rumbles of thunder
cannot be ruled out Friday as well given marginal elevated
instability. Precipitation chances then decrease gradually late
Friday night into Saturday. Otherwise, a switch over to snow or
rain/snow mix will be possible Friday night in northwest NEB and
the eastern NEB Panhandle. Beginning Friday through Friday night
much cooler air will be drawn around the system with sub-zero 850
hPa temperatures spreading into western NEB Friday night. While
sky cover will be ample, temperatures will be approaching freezing
thus there will be concerns for frost headlines Saturday morning.
Beyond Saturday, a ridge will be building in the Pacific offshore
waters through Monday. Meanwhile, large scale troughing will
affect much of the remaining portion of the CONUS through the
remainder of the long term period. Increased chances for
precipitation are expected largely late Sunday through Tuesday
with temperatures expected to stay on the cool-end.


.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1229 PM CDT Wed May 17 2017

Light to moderate rain will continue to affect much of western
and north central NEB through the afternoon. Hourly rainfall
rates at the top of the hour range from a few hundredths of an
inch to 0.15" (Gordon, NE). Latest surface plot shows sub-VFR
ceilings, as low as IFR, across much of the area with a few
isolated sites reporting low-end VFR (less than 7 kft). While
visibilities are generally 6SM or greater, higher rates at times
have reduced visibilities down to MVFR, sometimes IFR. Otherwise,
windy conditions are present with gusts between 20-30 MPH being

Rain is expected to taper off between late afternoon-mid evening
over much of the local forecast area. Ceilings are expected to
improve to low-end VFR across portions of southwest NEB to
central NEB this afternoon. Elsewhere, largely MVFR ceilings will
prevail. Overnight, generally dry conditions are expected across
central NEB with low chances across western NEB. Ceilings are
expected to deteriorate overnight, MVFR-IFR, mainly after
midnight. Winds will lessen some overnight, however, they will
remain elevated and out of the north.




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