Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000
FXUS63 KOAX 300445
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
1145 PM CDT MON AUG 29 2016

.UPDATE...
Issued at 1005 PM CDT MON AUG 29 2016

A north to south area of heavy rain fell across parts of the
forecast area this evening. Reports of 1.5 inches in Lincoln,
almost 2 inches near Chalco, another 1.31 inches at Kennard, and 1
to 3 inches were estimated per dual pol across parts of
Pottawattamie Co. Additional storms continue to develop as
shortwave trough energy slowly moves across Kansas and Nebraska
the rest of tonight and Tuesday. The moisture plume with 1.88
inches of PWAT on the 00Z OAX sounding remains in place and
gradually is pushed south later Wednesday. Upper level divergence
remains in place and h5 moisture increases with 80 to 90 percent
rh over a broad area through Tuesday. The low level forcing signal
is weaker, thus more difficult to define threat area and have a
general flash flood risk.  Expanded the flash flood watch to
included areas that received locally heavy rains again tonight and
will be prone to flash flood should these highly efficient storms
develop as the h5 trough slowly swings through Tuesday. The FFA
may need to be extended in time, however later shifts can asses
this.

&&

.SHORT TERM...(tonight through Thursday)
Issued at 241 PM CDT MON AUG 29 2016

Conditions are primed in some areas for additional flash flooding
tonight, primarily for those areas that received from 1 to 5
inches of rain last night in slow moving thunderstorms. Thus a
flash flood watch was issued for portions of southeast NE and
southwest IA where flash flood guidance was lowered as a result.

Environmentally, things are not that different from last night.
The atmosphere remains tropically moist being fed by a moist water
vapor plume that can be traced to the western coast of Mexico. PW
values this morning were around 1.8", which climatologically is
right at the maximum moving average for this time of year. This
moisture is also 1-2 standard deviations above normal based on
NAEFS climatological means, thus we have a lot of water to work
with. The upper low across the central Rockies will continue to
very slowly fill then lift across the plains through Tuesday. The
main westerlies are well north of the region, thus storm motions
are quite slow, only 10-15 mph at times. Due to the abundant
moisture, rainfall rates could easily reach 1-2" per hour. Storms
have begun to fire with the heat of the day with surface based
CAPE ranging 2000-3500 J/kg. Effective shear is very marginal
though, generally less than 20 knots. While freezing levels around
13300 could be conducive for hail, wet bulb zero levels are
extremely high around 12650. With the lack of higher storm scale
rotation and very marginal mid level lapse rates, hail will be a
struggle, but there does appear some wet microburst potential for
any storms that can develop a cold pool.

The wet pattern continues into Tuesday with conditions nearly
identical, but perhaps more coverage of storms as the upper trough
axis remains in place across the region, then slowly drifts south
of the area by early Wednesday. Will maintain likely Pops
along/south of I80 late tonight into Tuesday, then end precip from
north to south Wednesday morning, then go dry and mild for
Thursday.

.LONG TERM...(Thursday night through Monday)
Issued at 241 PM CDT MON AUG 29 2016

Dry conditions continue Friday with an upper ridge remaining in
place across the central US, but rain chances return for the
holiday weekend as the ridge shifts east, and a series of upper
level weather disturbances move into the area Saturday and Sunday,
along with a cold front on Labor Day.

&&

.AVIATION...(06Z TAFS for KOFK...KLNK and KOMA.)
Issued at 1130 PM CDT MON AUG 29 2016

Variable conditions through the period with thunderstorms
weakening at KLNK/KOMA and a westward developing area of storms
near KOFK and another cluster of storms southeast of KLNK.
Shortrange models have a variety of solutions with scattered
showers and thunderstorms through the TAF period. The TAF
locations are in between two fronts...a cold front to the north
and a stationary front to the south, however favorable moisture
and upper level patterns favor periodic showers and thunderstorms.
For now will include showers at KOMA/KLNK/KOFK and added tsra
mention as needed. Did include TSRA mention at all site Tuesday
afternoon. Vfr conditions prevail, however mvfr/ifr clds/vsbys
possible with precipitation and also with light winds and any
thinning in the higher clouds through Tuesday morning.

&&

.OAX Watches/Warnings/Advisories...
NE...Flash Flood Watch through Tuesday afternoon for NEZ045-052-053-
     066>068-078-088>093.

IA...Flash Flood Watch through Tuesday afternoon for IAZ069-079-080-
     090-091.

&&

$$

UPDATE...Zapotocny
SHORT TERM...DeWald
LONG TERM...DeWald
AVIATION...Zapotocny



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