Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 252021

Area Forecast Discussion
National Weather Service North Platte NE
321 PM CDT Tue Apr 25 2017

.SHORT TERM...(This evening through Wednesday)
Issued at 315 PM CDT Tue Apr 25 2017

Latest water vapor imagery showed cyclonic flow prevailing over
the western and central CONUS with a mid-level closed low evident
over eastern WY. A dry slot linked to a positive pv anomaly is
evident over southwest SD into the NEB Panhandle. Visible and IR
satellite imagery showed convective clouds over far northeast CO,
far southeast WY, and the southwest NEB Panhandle with radar and
lightning data showing convective cells and some lightning. This
convective activity has developed in an area of marginal
instability with mid-level lapse rates about 7-8 C/km. As such,
introduced slight chance of thunderstorms to southern portion of
the eastern NEB Panhandle and far southwest NEB based on trends
and hi-res guidance with thunderstorm potential expected to
diminish by early/mid evening.

Precipitation chances were largely decreased this evening and
overnight given the expected progression of the aforementioned
positive pv anomaly. Areal coverage of any precip should be
confined to isolated/scattered coverage with the best chances this
evening over northern NEB. Upper level trough over WY to the Four
corners will move east to the Upper Midwest-Southern Plains
tomorrow. Surface high pressure will build into western NEB from
the Northern Plains overnight and slide east tomorrow over the
eastern Central Plains. Mostly sunny skies will develop tomorrow
during the late morning-afternoon, however, highs are forecast to
be 10 to 18 degrees below seasonal normal values as cold air will
be in place after dropping into the region tonight.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 315 PM CDT Tue Apr 25 2017

A cool and unsettled period will prevail in the Wednesday night
through Friday time period. A mid-level long wave trough will
dominant the western CONUS as it amplifies through Thursday with
cyclonic flow prevailing aloft. Meanwhile, a closed circulation is
anticipated to deepen and be over the Upper Mississippi Valley
Wednesday night and then track into Ontario by Thursday. This
feature will continue to lift northeastward Friday with a broad
trough remaining over the western CONUS. Large scale forcing for
ascent in the way of disturbances embedded within the large scale
flow will contribute to increased chances for precipitation
Thursday through Friday. However, QPFs remain modest within the
unsettled period with liquid amounts expected to be largely light.
Of note, thermal profiles support rain/snow to all snow at times
in this period late Thursday night-early Friday morning wherein
the best chances for snow is across northwest NEB and the northern
half of the eastern NEB Panhandle. Snowfall amounts are forecast
up to 1 inch with impacts expected to be on the low-end at this
time. Below normal highs are expected with high temperatures
coldest on Friday (lower 40s  lower 50s), about 15 to 20
degrees below seasonal normal values.

Beyond Friday, the upper level trough in the large scale pattern
will move from the Northern Plains-Four Corners region into the
Plains Sunday. A closed low is expected to develop within that
time frame that will deepen Sunday over the eastern Central and
Southern Plains then lift northeast into the Upper Great Lakes
Monday. However, deterministic guidance is showing apparent
differences in phase and amplitude with the evolution of this
feature thus confidence is below normal Sunday and beyond. Chances
for snow or rain/snow present Friday night into Saturday across
the eastern NEB Panhandle and far western NEB, however, forecast
snowfall amounts remain light  generally less than one half
inch. Cool conditions are expected to continue with slight
chances/chances for precipitation returning Monday-Tuesday. Below
seasonal normal high temperatures are expected Saturday into the
new work week with the coolest conditions expected on Saturday and
Sunday with highs 10 degrees or less below normal values.


.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1209 PM CDT Tue Apr 25 2017

Main swath of rain has exited north central NEB with isolated-
scattered rain showers confined mostly to the Sandhills to the
SD border. Low ceilings are widespread across western and north
central with IFR conditions prevailing at most sites, however,
LIFR ceilings are present in portions of north central NEB.
Otherwise, breezy conditions are present with winds generally
sustained around 10-15 kts out of the north.

Isolated to scattered showers possible across northern NEB rest of
today and this evening. Sub-VFR conditions are expected to
prevail largely through early tomorrow morning with MVFR or IFR
ceilings, lower ceilings over the Sandhills on north. Ceilings
will improve gradually, along with decreasing cloud cover,
tomorrow morning into the afternoon from southwest NEB to north
central NEB. Dry conditions expected on Wednesday.




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