Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 272027
AFDLBF

Area Forecast Discussion
National Weather Service North Platte NE
327 PM CDT Thu Apr 27 2017

.SYNOPSIS...
Issued at 327 PM CDT Thu Apr 27 2017

H5 analysis had a longwave trough of low pressure across
the lower 48 this morning. Several embedded shortwaves were noted
within this trough. These shortwaves were located over northeastern
Iowa, northern Minnesota, northern Wyoming, eastern Alberta and
eastern Washingtion state. Southwest of the trough, high pressure
was anchored around 750 miles off the coast of southern California.
The northern Wyoming shortwave has pushed south southeast into
central Wyoming this afternoon. In advance of this feature, showers
were present from eastern Wyoming into western Nebraska and the
Nebraska Sandhills. Some rumbles of thunder were also present over
eastern Wyoming and eastern Colorado this afternoon. Skies were
partly to mostly cloudy this afternoon with some limited clearing
noted in northeastern portions of the forecast area. Temperatures as
of 3 PM CDT ranged from 49 at Thedford and O`Neill to 55 at
Ogallala.

&&

.SHORT TERM...(This evening through Friday)
Issued at 327 PM CDT Thu Apr 27 2017

 surface low becomes more organized and deepens over eastern
Colorado as the upper low moves out into the plains this evening and
provides some more support. Fairly strong moisture advection
continues across the southern plains out ahead of the system. Kept
mention of thunderstorms into the evening hours given the amount of
mid level instability developing, especially across the eastern
panhandle and south of the interstate.

The main show will start tonight as the low moving out of Colorado
becomes more organized and pushes north. The models are advertising
a few areas of frontogenesis that try to focus the precipitation
tonight along with a secondary deformation axis first oriented north
to south from the panhandle into eastern Colorado, rotating north
into areas south of Interstate 80. The stronger frontogenetic
forcing will be north of the Interstate...somewhere...There are some
minor differences in where the models place the areas of heavier
rain and snow but most of them have it between the Interstate and
the South Dakota border after midnight.

Given the cold airmass, there will be some areas of mixed
precipitation north again tonight after midnight with some
changeover to all snow. The snow will be very wet and the ground is
relatively warm so it will have a difficult time accumulating unless
you happen to fall underneath one of the areas with better
forcing...then you could receive a couple of inches of snow,
especially on the grassy or raised surfaces. Accumulations will not
be widespread and will be less than an inch over most areas.

.LONG TERM...(Friday night through Thursday)
Issued at 327 PM CDT Thu Apr 27 2017

Mid range...Friday night through Sunday...Precipitation chances in
this weekend will be the main forecast challenge in the mid range. A
closed low will retrograde to the southwest Friday night, closing
off over southern Colorado and northern New Mexico by Saturday
morning. This feature will then lift east into the northern Texas
panhandle, crossing Kansas on Sunday. The latest NAM12, GFS and EC
solutions from this morning vary widely in their speed of the H5 low
this weekend. The NAM12 is most aggressive, while the EC solution
being the slowest. As of 00z Monday, the H5 low is located over
central Iowa (NAM12), Nebraska City Nebraska (GFS) or northeast of
Wichita Kansas (ECMWF). Compromising between the 3 solutions, favors
a Blend of the GFS and EC solutions for this forecast. That being
said, conditions along and  north of Interstate 80 should see fairly
dry conditions Friday night into Saturday. By Saturday night into
Sunday, the threat for precipitation will increase from southwestern
into northeastern portions of the forecast area as the upper level
low tracks across Kansas into southeastern Nebraska. The models have
a nice deformation zone on the northern and northwestern portion of
the upper level low Saturday night into Sunday with this
precipitation pivoting west and northwest into eastern and southern
portions of Nebraska.

Sunday night through Thursday...Precipitation will linger in the
eastern forecast area Sunday night before clearing the forecast area
on Monday morning. Temperatures on the back side of the exiting low
may be cold enough Sunday night for light snow and will mention it
in the latest forecast. The forecast area will remain under the
influence of the longwave trough of low pressure through midweek.
Precipitation chances will increase on Tuesday and Wednesday as a
couple of embedded disturbances drop south from the northern Rockies
onto the central plains. Even with the increased precipitation
chances, temperatures will rise back into the 50s to lower 60s as
the core of the cold air aloft pushes into the Great Lakes. By
Thursday, a ridge of high pressure will begin to push east into the
Rockies. Warmer h85 air will push into western Nebraska on Thursday,
followed by the remainder of the area on Saturday. Readings will
climb back to seasonal levels by Thursday with even warmer
temperatures on track for Friday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1227 PM CDT Thu Apr 27 2017

There will continue to be increasing mid and high clouds today
across western Nebraska. Showers and possibly some isolated
thunderstorms are starting to develop across the southwest and
will continue to move northeast into early afternoon as a surface
low pressure deepens over southeast Colorado. Showers will become
more widespread this evening with ceilings lowering into IFR
categories over southwest Nebraska. Periods of moderate rain
showers were also introduced into the KLBF TAF late in the
period. It will be a cold rain with some snow possibly mixed
in...especially as you move further north of the Interstate.
Southeast to east winds are expected around 10kts today and
tonight.


&&

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

$$

SYNOPSIS...Buttler
SHORT TERM...Allen
LONG TERM...Buttler
AVIATION...Allen



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