Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000
FXUS63 KOAX 190454
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
1154 PM CDT THU AUG 18 2016

.SHORT TERM...(Tonight through Sunday)
Issued at 330 PM CDT THU AUG 18 2016

The primary forecast concerns are still in regards to potential for
severe weather and heavy rain Friday afternoon and Friday evening.

A fairly robust mid tropospheric trough was noted in the 12z upper
air data moving across Canada into parts of the Rockies and Plains.
12 hour height falls estimated at up to 100 meters were over central
Manitoba this morning. Weaker height falls extended farther south.
A couple of jet segments were noted at 300 mb...one ahead of the
trough and one behind the trough (both around 85 knots). At 850 mb
a cold front was noted extending from northeast to southwest over
the northern Plains.

Water vapor satellite imagery early this afternoon showed several
disturbances in the flow to our west and northwest. Surface analysis
early this afternoon had a cold front from northern Minnesota
back into the Nebraska panhandle. That front will be moving east
or southeast tonight...pushing into northeast Nebraska this
evening. By sunrise Friday that front will likely stretch from
northwest Iowa into northwest Kansas. Main precipitation tonight
should be mostly along or behind that front...can kept POPs
confined to areas northwest of Omaha and Lincoln overnight.

As the front pushes to the southeast on Friday...rain chances will
increase. The threat of storms through mid day or so should remain
mostly across northeast Nebraska...but at least scattered storms are
likely to increase by mid afternoon. Precipitable water (PW) values
reach near two inches by 00z Saturday in the GFS output and over two
inches in the NAM. So there does appear to be some heavy rain
threat. ML CAPE values are likely to reach 1500-3000 j/kg with decent
0-6 km shear. So the SPC Day 2 outlook seems on track. NAM point
forecast sounding for the Omaha and Lincoln areas seemed more
representative than those from the GFS (except the PW may be over
exaggerated Friday evening). Have very high POPs going for the late
afternoon and evening...mostly 40 to 90 percent.

Rain chances across eastern Nebraska should decrease dramatically
after midnight Friday night but linger in southwest Iowa. There is
pretty good consensus now that Saturday will be dry for our area
as high pressure at the surface build from the Dakotas into Kansas
through Saturday night. Highs over the weekend will be around 5 to
10 degrees below normal.

.LONG TERM...(Sunday night through Thursday)
Issued at 330 PM CDT THU AUG 18 2016

500 mb pattern should feature a ridge from the central Rockies up
into Saskatchewan...which should move east through Monday night.
Then there will likely be several shortwave troughs embedded in
the fast west/southwest flow moving across the region.

Temperatures will moderate to the lower and mid 80s early in this
period with thunderstorm chances returning as southerly flow
increase Monday night or Tuesday morning. Then it remains somewhat
unsettled through mid week.

&&

.AVIATION...(06Z TAFS for KOFK...KLNK and KOMA.)
Issued at 1151 PM CDT THU AUG 18 2016

Scattered showers and thunderstorms will increase across eastern
Nebraska through the TAF period as a cold front settles into the
area. The front should reach KOFK before 12Z, with MVFR cigs
settling in behind. Scattered thunderstorms are possible through
16Z, with another round developing in the early afternoon. Storms
will likely hold off at KLNK and KOMA until after 18Z when a line
of storms moves in from the west. Attendant MVFR to IFR cigs/vsbys
will accompany any storms. Then MVFR cigs in scattered showers are
forecast behind the main batch of storms, generally from about 02Z
to the end of the TAF period.

&&

.OAX Watches/Warnings/Advisories...
NE...None.
IA...None.
&&

$$

SHORT TERM...Miller
LONG TERM...Miller
AVIATION...Dergan



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