Area Forecast Discussion
Issued by NWS North Platte, NE

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000
FXUS63 KLBF 061203
AFDLBF

Area Forecast Discussion
National Weather Service North Platte NE
603 AM CST Wed Dec 6 2017

.SHORT TERM...(Today and tonight)
Issued at 332 AM CST Wed Dec 6 2017

Latest water vapor imagery shows an upper level ridge just
offshore the West Coast extending across British Columbia.
Elsewhere, a deep upper level trough is downstream affecting the
central and eastern CONUS with a closed low by southern James Bay.
Latest regional radar display shows isolated to scattered flurries
or light snow showers upstream in southwestern SD and across parts
of the Sandhills. Of which, scant to no accumulation is occurring
with very minimal restrictions to visibility if any given surface
obs and web cams.

Northwest flow will prevail aloft today then become more northerly
tonight as the large scale pattern evolves over the next 24 hours.
The ridge upstream is expected to build slightly with the pattern
remaining highly amplified. Another breezy day is expected with
winds out of the northwest to north with sufficient mixing
anticipated. Strongest gusts forecast over the southeast
Panhandle and southwest NEB with gusts up to 40 MPH.

Increased chances for precip spread across the local forecast area
south towards I-80 today, albeit low-end PoPs, late morning on.
P-type will be mainly snow with areas near the I-80 corridor
seeing a mix to possibly sprinkles at times this afternoon. Best
chances for light snowfall, up to 1 inch, is across the northern
half of the local forecast area/roughly north of NEB highway 2.
Wherein an modest zone of lower tropospheric deformation and
frontogenesis sags and moves southward this afternoon. There
appears to be fair agreement, though some uncertainty spatially,
with deterministic hi-res guidance and SPC HREF. Otherwise, trace
precip more likely near and south of the Interstate 80 corridor
today. Current thinking is near/by midnight the threat for
precipitation will have ended. Otherwise, below seasonable
normal highs are expected today with a cooler air mass in place
and due to the lack of insolation. Highs forecast about 30 in far
northern NEB to upper 30s in far southwest NEB. Lows are expected
to read near 10 degrees to the teens across the forecast area
tonight.

.LONG TERM...(Thursday through Tuesday)
Issued at 332 AM CST Wed Dec 6 2017

Thursday through Friday Night: A limited threat for precipitation
Thursday in the northwest is the main forecast challenge in the
mid range. The latest superblend guidance for Thursday had
initialized with a small threat for light pcpn in the northwest on
Thursday. Looking at the latest GFS and NAM12 solutions, mid
level warm air advection approaches the northern Panhandle and
northwestern Sandhills on Thursday increasing mid level lift.
Aloft, a h300 Jet streak is forecast to be oriented from southern
Canada south into the Four Corners Thursday. Western and north
central Nebraska lie in the left front quadrant of the jet streak
Thursday, adding additional lift. The limiting factor for
precipitation Thursday will be moisture as dry mid layer conds
precede the arrival of the mid and upper level dynamics. Even with
the lack of moisture, it is hard to ignore the mid and upper
level dynamics, and will leave a mention of low precipitation
chances in the northwestern CWA Thursday. The jet will continue to
lift east into Thursday night, ending the threat for
precipitation and allowing warmer air to push into the forecast
area from the west. After highs in the 30s for Thursday, highs
Friday will reach the 40s with a 50 reading possible in the far
southwest.

Saturday through Tuesday: Low pressure aloft, over Ontario, will
track northeast into Quebec this weekend. This will allow the
associated arctic airmass to retreat east of the forecast area,
with the leading edge of the coldest arctic air generally east of
the Missouri river on Saturday and east of the Mississippi river
on Sunday. Highs Saturday will reach the middle 40s in the
northeast to the middle 50s in the southwest. By Sunday, highs
will reach the 50s across the entire forecast area. A shortwave
trough of low pressure, rotating around the western periphery of
the Quebec low, will force a back door cold front into the
forecast area Sunday night into Monday. Highs will reach the 40s
on Monday with 40s to the lower 50s for Tuesday. There is some
decent model differences between tonight`s GFS and ECMWF
solutions. The GFS solution is more aggressive with its west ward
surge of arctic air early next week as it develops low pressure
over south central Ontario Tuesday morning. The ECMWF is around
500 miles further east with this feature. The differences with
these two features, and the resultant west ward surge of arctic
air, will be problematic for the temperature and precipitation
forecast early next week. The GFS ensemble, MEX and ECE
statistical guidance spells this out tonight, as all three have a
wide range in temperatures, especially in the northeastern
forecast area. That being said, chose to stick closely to the
superblend temperature forecast early next week. In addition to
temperatures, there will be a small threat for precipitation,
especially in the vicinity of the back door cold front. The
forecast initialized with some small pops in the northeastern
forecast area for Monday and Tuesday and this is plausible, if the
GFS solution verifies. If the EC were to verify next week, we
would see dry conditions carry over from the weekend.

&&

.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 515 AM CST Wed Dec 6 2017

Regional radar display shows isolated flurries-very light snow
showers occurring across parts of southwest SD to northwest NEB
and parts of the Sandhills. Largely no accumulations are expected
early this morning.

Conditions will be breezy today with gusts 25-35 kts in the
afternoon across the forecast area, strongest in the eastern
Panhandle and far southwest NEB. Otherwise, light snow will be
possible at times across northern Nebraska with the best chances
for light snowfall accumulations occurring in the afternoon, up
to one inch. Further, MVFR ceilings will be possible at times
across northern NEB late morning-afternoon. Elsewhere, less
confident in precip occurring along and south of the Interstate
80 corridor. Of which, trace precip, flurries/sprinkles, will be
possible in the afternoon-evening. Thus not expecting much in
terms of impacts at the KLBF terminal. Thereafter threat for
precip tapers off during the evening hours across western NEB.
Light breezes will persist tonight.

&&

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

$$

SHORT TERM...ET
LONG TERM...Buttler
AVIATION...ET



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