Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 140841
AFDLBF

Area Forecast Discussion
National Weather Service North Platte NE
341 AM CDT Sat Apr 14 2018

.SYNOPSIS...
Issued at 339 AM CDT Sat Apr 14 2018

Very strong upper low slowing its forward progression early this
morning and becoming slightly more negatively tilted. Warm sector
ahead of the main low indicative of expansive thunderstorm
development from IL to TX along the associated cold front. Further
north, along and north of the warm front, primarily snow or a
wintery mix from the Great Lakes westward into the Plains. Closer to
home, well defined snow band continues to exist across much of
western and north central NE. Blizzard conditions ongoing
and widespread.

&&

.SHORT TERM...(Today and tonight)
Issued at 339 AM CDT Sat Apr 14 2018

Overview: short range model guidance suggests well defined snow band
will gradually weaken through the morning hours, though not before
adding to significant accumulations of snow across the area. Winds
will remain strong through the day as the upper low stalls briefly,
then begins to slide southeastward and out of the state by late
tonight. Clouds will also clear accordingly from west to east as
high pressure settles in.

Temperatures will struggle through the day today under significant
cloud cover and snow, topping out still some 30 degrees below where
we should be this time of year. As skies clear out tonight low temps
will be similarly anomalous, ranging from 20 to 25 degrees below
average for this time of year.

Detailed discussion for blizzard area: Classic mature mid-latitude
cyclone evolving across the Plains. Well defined, deep warm conveyor
belt located from the Gulf of Mexico on the 290K through 300K
surfaces. This now primarily feeding into large LEWP across the
southeastern states, though a small bifurcated portion working into
the northwest side of the upper low. North of the warm front an
equally impressive cold conveyor belt stretching across the Great
Lakes and upper midwest and feeding directly into the well defined
mid level frontogenetic (FGEN) zone across NE. Upper air sounding
from LBF this evening showing a deep, nearly isothermal layer
indicative of the associated TROWAL airstream. This layer ranges
from near -12C at the bottom to -10C at the top. All this is
suggestive of a highly efficient dendrite growth zone. Along the
eastern edge of the FGEN band throughout the day and into the
overnight has also shown the classic progression of upright
convection on the eastern edge then more slantwise convection as one
moves westward. Several instances of lightning and thunder in this
EPV reduction zone helping to continually redevelop the snow band
eastward with time.

This area of mid level instability will eventually be worked over as
the upper low drifts southeast today and some signs of this
happening already. This will allow a marked decreasing in heavy snow
through the morning, though strong winds will likely keep ground
blizzard conditions and reduced visibilities through much of the
day.

.LONG TERM...(Sunday through Friday)
Issued at 339 AM CDT Sat Apr 14 2018

The pattern over the next week remains active with a quick
succession of low pressure systems across the Plains. The current
low treks into the Great Lakes by Monday, the second low impacts
Nebraska Tuesday into Wednesday, and a third low lines up for next
weekend (of course). In between the lows, small ridges build aloft
and areas of high pressure settle in at the surface.

Sunday and Monday... In the wake of this weekend`s blizzard,
temperatures remain seasonably cool. The upper low slowly works into
IA/IL by Sun. afternoon, which is close enough to keep Nebraska in
northerly flow. H85 temps struggle to reach 0C and with a potential
snowpack still in place, kept highs well below guidance. Forecast
ranges from around 30F north central to mid 40s far SW, which is
about 20 degrees below normal. Return flow resumes Monday, but with
modest WAA at best and the core of coldest air hanging just east of
the state, kept highs below guidance. Far SW Neb may fare better as
H85 temps push 10C, resulting in mid/upper 50s.

Tuesday and Wednesday... The stronger push of warm air arrives
Tuesday as the H85 thermal ridge crosses the area ahead of the next
low pressure. However, different track and timing of the low result
in the MEX about 10F warmer than ECE. Regardless, this appears to be
a progressive system with relatively little moisture and overall
mild temps aloft. A brief changeover from rain to snow overnight may
produce a dusting across the far north.

Thursday and beyond... Despite another brief return to southerly
flow on Thursday, no real temp recovery takes place. Temps begin to
fall again Friday with upslope flow and moisture advection
(increased cloud cover) ahead of the third low pressure. As per
previous discussions, this system bears watching. The GFS and ECM
have been somewhat consistent with cutting a deepening low right
across the central Plains. Compared to this weekend`s blizzard,
temps aloft are warmer, but still cool enough to present a snow
threat. Wind may also be a hazard as H85 winds approach 50 kts.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1137 PM CDT Fri Apr 13 2018

Widespread IFR/LIFR is expected overnight through 18z Saturday.
Improvement to MVFR/IFR is possible but not certain along and
west of highway 61 Saturday morning.

VFR/MVFR is expected Saturday afternoon along and west of highway
183.

MVFR/IFR is expected Saturday afternoon and evening east of
highway 183.


&&

.LBF WATCHES/WARNINGS/ADVISORIES...
Blizzard Warning until 1 PM CDT /noon MDT/ this afternoon for
NEZ004-005-022>025-035-056>058-069-094.

Blizzard Warning until 7 PM CDT this evening for NEZ006>010-
026>029-036>038-059-070-071.

&&

$$

SYNOPSIS...Stoppkotte
SHORT TERM...Stoppkotte
LONG TERM...Snively
AVIATION...CDC



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