Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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FXUS63 KOAX 132337

Area Forecast Discussion
National Weather Service Omaha/Valley NE
637 PM CDT Fri Oct 13 2017

.SHORT TERM...(Tonight through Monday)
Issued at 257 PM CDT Fri Oct 13 2017

Clouds and showers are around the area, with increase in coverage of
both expected this evening and tonight. Subjective 12Z upper-air
analysis indicates an upper-level trough in the Pacific Northwest,
with weak shortwaves rippling ahead of it through the southwesterly
flow across the central US. A 125-140kt upper-level jet streak
extended from northern NV/northern UT through SD/MN. At 850mb, a low
was analyzed in north central KS/south central NE, with an 8C+
moisture axis extending into southeast NE/southwest IA ahead of the
low. A warm front was noted from the low eastward near the I-80
corridor into central IA. Surface lows at 19Z were analyzed in the
lee of the Rockies in central CO, in northeast NM, and in east
central KS, with a surface front extending northeastward from KS
through southeast IA toward southern Lake Michigan. Between the
surface and 850mb fronts, a bank of low stratus extended across
KS/NE/IA/northwest MO.

The main forecast concern for the upcoming week is the potential for
rain and isolated storms tonight through Sunday evening. As the
upper-level trough moves eastward toward and across the northern
Plains, it will first reinforce the surface to mid-level boundary,
then drive the front southward as it moves east. A few showers are
possible this evening and tonight, especially in the southern half
of the CWA, but think activity will wait to really ramp up until
late tonight, around the 09-12Z time frame. Once that begins, with
upper-level support from the approaching trough and with an
adequately moist low- to mid-level environment, believe rain will
expand fairly quickly, especially south of I-80. Point forecast
soundings and plan view guidance indicates very little instability
reaching NE/IA, with MUCAPE maybe peaking around 500-1000 J/kg in
far southeast NE and maybe around 500 J/kg in far southwest IA.
Think isolated thunder is the most appropriate wording, as thunder
is not likely to be as widespread as the rain in which it is
embedded. Did bump up QPF a bit in southeast NE/southwest IA, with
persistent rain for several hours along a well-forced frontogenetic
band. Showers should decrease rather quickly from west to east from
late Saturday afternoon through the evening, with increasing
northwest winds as cold air advection arrives and pushes the front
southward. Exception may be in northeast NE/northwest IA, with some
potential lingering wraparound showers into the evening to overnight
hours. Given persistent/expanding clouds and showers through the
day, have lowered forecast max temps quite a bit on Saturday, with
little rise at all in the northern CWA as highs linger in the 50s,
highs around 60 near the I-80 corridor, and highs in the lower to
mid 60s for most of the southern CWA.

Behind the Saturday system, weather will become much quieter through
the rest of the week. Cold air advection will keep temperatures on
the cool side on Sunday, with highs remaining in the upper 50s to
around 60 degrees. Mid-level warm air advection on Monday should
allow highs to reach the upper 60s to around 70 degrees, despite a
weak shortwave and frontal passage in the afternoon/evening.

.LONG TERM...(Monday night through Friday)
Issued at 257 PM CDT Fri Oct 13 2017

Quiet and fair weather will continue through the work week, with
upper-level flow transitioning from northwesterly to zonal to
southwesterly through the week. A weak frontal passage around
Wednesday should be dry, though it may temporarily tip temperatures
a bit lower before rising again through the end of the work week.
Temperatures should linger above normal throughout the week, and
skies should be largely clear to mostly clear, providing some much
needed drying time for ground conditions.


.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 633 PM CDT Fri Oct 13 2017

Fairly complex set of TAFs with numerous weather features to
contend with. MVFR at KLNK, becomes LIFR by 08-12z, with scattered
showers, then back to MVFR by 22z with a wind shift to the
northwest. VFR at KOMA, but becoming MVFR within the next hour,
then to LIFR by 08-12z with scattered showers, then back to MVFR
by 22-23z with a wind shift to the northwest. VFR at KOFK becoming
MVFR by 08z, then LIFR by 09-11z, but but to MVFR with a wind
switch to the northwest by 21z. Could be Thunder at KLNK/KOMA
10-14z, but latest Hires short term models suggest thunder could
be just south of these TAF locations, but will continue to monitor
later model trends.




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