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fxus63 koax 201146 

Area forecast discussion
National Weather Service Omaha/valley NE
546 am CST Mon Feb 20 2017

Short term...(today through wednesday)
issued at 322 am CST Mon Feb 20 2017

Early morning water vapor imagery indicated shortwave trough over
the Southern Plains lifting northeastward. This will phase with a
progressive trough across the northern rockies today. Deep
southerly flow ahead of the Southern Plains feature was leading
to significant low-level moisture spreading into the County Warning Area. Regional
radar mosaic indicated a corresponding band of showers and a few
thunderstorms spreading through eastern Kansas into southeast neb.
This trend should continue this morning with the highest chance of
rainfall over the eastern County Warning Area through mid morning. Surface low
pressure over western South Dakota early this morning will then move
eastward with a cold front progressing southeast through the forecast area.
Various short-term cams indicate some attempt as convection
developing this afternoon over the eastern County Warning Area along this
boundary. Although confidence in this occurring is low we will
include a small pop late this afternoon along and east of the MO
river for the potential for a little redevelopment. Otherwise
clouds will be clearing from west to east today allowing for good
mixing and another very mild afternoon.

Tuesday is still shaping up to be the warmest day of the week as
the surface to 850 mb flow turns to the southwest/west. Models are
consistent in mixing to at least 900 mb, which seems reasonable
given the wind direction, full sunshine, and dry atmosphere in
place. With 900 mb temperatures of +14 to +19 c across the County Warning Area we
should see highs climb into the mid and upper 70s with records
highs likely. A progressive shortwave trough over the northern
plains will lead to a weak front on Tuesday night, but again
cooling behind this boundary is limited and additional record
highs are possible on Wednesday with good mixing again expected.

Long term...(wednesday night through sunday)
issued at 322 am CST Mon Feb 20 2017

The vigorous shortwave trough and associated surface cyclone will
be the main focus in the extended range of the forecast. Models
continue to struggle with the evolution of this system, although a
bit better agreement was seen in the 00z suite of global models.
The Gem continues to be slow and deep, the ec was closer to the
GFS timing this cycle but was still a bit deeper with the trough
and surface reflection, and the GFS continues to be the most
progressive and weakest solution.

Regardless of the model it appears that much cooler weather will
return to the region starting on Thursday as heights fall and
cooler air filters into the region. Precipitation will likely
start during the day on Wednesday as thermal gradient increases
leading to mid-level frontogenesis increasing. As large-scale
forcing for ascent increases on Thursday night precipitation will
increase in intensity and coverage over the forecast area. Precipitation
will end west to east on Friday as the deformation band pulls off
to the east. Consistent with previous forecasts it appears that
initial precipitation will start as rain with a transition from
northwest to southeast of snow on Thursday night. Accumulations
do appear likely, especially north of i80 though specific amounts
remain unclear. We also expected north winds of 20 to 30 mph,
which could lead to some blowing and drifting, but we do
expect a fairly wet snow that could limit that threat to some
degree. Another system is expected later in the weekend, but a
good deal of uncertainty remains during this time period.


Aviation...(for the 12z tafs through 12z Tuesday morning)
issued at 541 am CST Mon Feb 20 2017

Variable conditions will be across the area early in the period
through about 18z as bands of showers lift northeast from eastern
Kansas in southeast Nebraska and western Iowa. A cold front over
central Nebraska will move east and reach the eastern Nebraska
border between 18z and 23z with conditions becoming VFR.


Oax watches/warnings/advisories...
NE...Fire Weather Watch Tuesday afternoon for nez016-030>032-042>044-



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