Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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526
FXUS63 KOAX 220859
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
359 AM CDT Thu Jun 22 2017

.SHORT TERM...(Today through Saturday)
Issued at 330 AM CDT Thu Jun 22 2017

Forecast concerns in the short term will be thunderstorm
chances/coverage as the cold front pushes southward through this
evening.

Thunderstorms have struggled to get going over the forecast area
with isolated storm near SUX/SD border where the is a pocket of
upper level divergence/theta-e advection/low jet forcing...and
over central Nebraska.northern KS. Storms that form weaken as
they move into the hot air. Height falls were greatest around 110m
ht falls over Manitoba with broad height falls over the central
part of the country with the flattening of the h5 pattern. The h7
thermal ridge was over much of the forecast area at 12 to 14 degC
and this led to highs in the 90s with 100 the hot spot at Albion.
H85 dewpoints were 16-18deg C near the front...however much drier
toward FNB.

Per the GOES-16 satellite loops/WSR-88D radar...there has been an
uptick in the storms across parts of the Northern Plains, with
more of a diurnal decrease across the southern Plains. The storms
over Kansas have been maintaining themselves as they drift
east-southeastward. At 08Z, the cold front was north of FSD and
near CDR and the warm front was near southern MN. The more
organized storms were across northern Iowa and also post-frontal
across parts of SD.

The h5 closed low pressure system over Saskatchewan travels east
into Ontario through 06Z...with 60 to 80m ht falls making their
way into SD/MN as the h5 trough deepens. This will push the cold
front southward toward Omaha/Lincoln by 00Z and northwest MO by
06Z.

We are starting out quite mild in the 70s and 80s with the brisk
south winds. High clouds could affect temperatures ahead of the
front, however they should warm into the 90s, with readings in
the 80s behind the front. As the trough builds in...there is
cooling aloft and isentropic lift saturating areas to the north
with the chance for thunderstorms.

There is a shortwave pushing across the forecast area this morning
with upper level support and something isolated could
develop...however, the most recent cams/nam12/gfs/ec are mainly
dry thru 18Z when we start to see increasing chances from 18z-22Z
in northeast Nebraska...with chances settling southward 22z-06Z.
Will monitor the latest radar and possibly include some pops with
the morning convection near KS...otherwise will bring increasing
chances along and behind the front.

Instability increases ahead of the front today to 2000-3000j/kg,
however the 0-3km 35-45kt bulk shear is displaced north of this
area. SPC has areas in the vicinity of the front in the marginal
risk for severe storms with hail and damaging winds possible. The
trends have been for the organized storms to be northeast of the
forecast area. Forecast soundings support at least some strong to
severe where storms form along with heavy downpours of rain.

Reinforcing cold air with a shortwave trough in the
northwest flow could spark some showers, however for now with the
mid level moisture just included instability cu. Highs Friday are
forecast to be in the 70s

Another deeper area of low pressure rotates through the flow
across MN Saturday and this cold core system could have some
showers and thunderstorms with it, however it should remain to the
north of the forecast area. Highs again for Saturday are expected
to be in the 70s with morning lows in the 50s.

.LONG TERM...(Saturday night through Wednesday)
Issued at 330 AM CDT Thu Jun 22 2017

The extended forecast still has the high pressure aloft anchored
over the desert southwest. The northwest flow aloft and cooler
highs in the 70s Sunday and Monday moderate for Tuesday and
Wednesday with highs in the 80s. There are a few chances for
showers/storms and although the medium-range models have timing
differences, we have included scattered thunderstorms
Wednesday/Wednesday night.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1143 PM CDT Wed Jun 21 2017

VFR conditions are indicated through the TAF cycle. Shower/storm
threat tonight has not materialized, so should see a few high-
level clouds and winds decreasing, along with increasing wind
shear. Mid-level clouds likely will increase for a time on
Thursday around frontal passage, but confidence in showers/storms
is too low to include yet. Wind shift will arrive in the 22-00Z
time frame. Speeds in the afternoon both before and after the wind
shift will be around 10-15kt.

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...None.
IA...None.
&&

$$

SHORT TERM...Zapotocny
LONG TERM...Zapotocny
AVIATION...Mayes



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