Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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997
FXUS63 KOAX 200922
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
322 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 CWA. Regional
radar mosaic indicated a corresponding band of showers and a few
thunderstorms spreading through eastern KS into southeast NEb.
This trend should continue this morning with the highest chance of
rainfall over the eastern CWA through mid morning. Surface low
pressure over western SD early this morning will then move
eastward with a cold front progressing southeast through the FA.
Various short-term CAMs indicate some attempt as convection
developing this afternoon over the eastern CWA 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 CWA 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 FA. 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 06Z TAFS through 06Z Monday night)
Issued at 1115 PM CST Sun Feb 19 2017

Low clouds are slower to move into the area, but should still move
in overnight. Showers and isolated thunder should spread up over
southeast Nebraska and into western Iowa late tonight. The MVFR
ceilings should continue into Monday morning, then conditions will
improve to VFR. Winds will shift to the northwest as a front moves
through, but had too many groups to include all details of wind
shift for KOMA and KLNK.

&&

.Fire Weather...
Issued at 322 AM CST Mon Feb 20 2017

With the very warm temperatures expected on Tuesday coupled with a
dry boundary layer we expect afternoon minimum relative humidity
values AOB 20%. This along with southwest winds of 15 to 25 mph
will lead to potentially critical fire weather conditions. Thus we
have issued a fire weather watch for Tuesday afternoon. Similar
fire weather conditions are possible again on Wednesday afternoon
with highs again climbing into the 70s and relative humidity
values dropping to near 20%. A fire weather watch may need to be
considered later for this time period as well.

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...Fire Weather Watch Tuesday afternoon for NEZ016-030>032-042>044-
     050>053-065>068-078-088>090.

IA...None.

&&

$$

SHORT TERM...Boustead
LONG TERM...Boustead
AVIATION...Miller
FIRE WEATHER...Boustead



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