Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000
FXUS63 KOAX 180913
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
413 AM CDT Tue Jun 18 2019

.SHORT TERM...(Today through Thursday)
Issued at 345 AM CDT Tue Jun 18 2019

Forecast concerns in the short term include rain and
thunderstorms especially through Wednesday morning and how storms
today will affect overnight convection and placement of heavy
rain...need for flash flood/flood headlines...potential for severe
weather.

Water vapor satellite imagery generally shows a broad trough from
Quebec southwest toward the Northern Plains and the southwest U.S.
with shortwave troughs over western Kansas toward Texas and another
trough from Missouri toward Louisiana.  Several clusters of
convection were noted especially ahead over these troughs over the
Ohio/Tennessee/Carolinas area and from Nebraska south across
Kansas into Oklahoma and Texas. Through the overnight hours, the
convection across Kansas has trended weaker diurnally.

Locally, the 00Z OAX sounding showed 1.25 precipitable water with
around 1500 J/kg SBCAPE.  Of note on the upper air charts was the
pocket of 2-4deg h7 dewpoints over Neb/southwest Neb and the 10-12
deg h85 dewpoints across the northwest 2/3rd of Neb.  At the
surface, a cold front was sinking south with dewpoints in the 50s
across northern Nebraska.  Based on the surface pressure...the
boundary would extend from low pressure over north central Kansas
into southeast Nebraska into central Iowa.  The wind flow is weak
and the surface dewpoints are in the lower to mid 60s.   The latest
WSR88D radar imagery shows a band of showers in northern Nebraska
and northwest Iowa and this is near the h85 front. Other showers
were noted along I80 near the diffuse surface boundary, and the
well- organized convection was over western Kansas.

The shortwave trough over western Kansas will continue to move
eastward toward eastern Nebraska and eastern Kansas during the day
with 20 to 40m ht falls and a speed max noted at h5. With the
support of upper level divergence/vorticity advection/increasing
mid level warm advection, look for the showers and thunderstorms
to continue with this shortwave. The CAMs show and uptick in
rainfall rates as the storm system progresses east into the
forecast area. PWAT values increase to 1.5 to 1.75 inches today
and continue into Wednesday morning across southeast Nebraska and
southwest Iowa. The storm motion of 10 to 20 mph decreases tonight
to around 10 mph. There is some thickness diffluence, but with a
secondary diffluent area farther south where additional storms are
expected over Kansas.

Southeast Nebraska and southwest Iowa have had more rain recently
with 150 to 300% of normal over the past month include higher
amounts this past week. The high efficiency and slow movement, low
level jet feeding into southern Nebraska, along with some
convective signals of heavy rain, not the classic FFA situation,
but merits heavy rain potential. As a result, included southeast
Nebraska and parts of southwest Iowa in a flood watch today into
Wednesday morning. Some severe weather potential with CAPE values
of 500 to 1500 j/kg, but it appears limited, thus the marginal
risk for severe trimmed to near the Kansas border.

The rain will gradually moves out Wednesday, but takes a while in
far southeast Nebraska.

.LONG TERM...(Thursday night through Monday)
Issued at 345 AM CDT Tue Jun 18 2019

Thursday, lead shortwave trough energy will be lifting across the
Dakotas and some isolated storms may develop southward into
northeast Nebraska/toward the Missouri River into western Iowa as
the wave tops the ridge.  Highs look to be in the 80s.

Later Thursday night into Friday, southwest flow aloft with
strengthening low level flow should increase thunderstorm chances
across parts of Nebraska into Iowa along a front. The front then
settles southward Friday night into Saturday with multiple rounds
of storms between Thursday night and Saturday morning.

Surface high pressure builds in later Saturday. Some isolated pops
through the weekend, although organized convection is more to the
south or east of the forecast area. Highs in the 70s/80s Saturday
through Monday.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1129 PM CDT Mon Jun 17 2019

VFR conditions will transition to MVFR through the period with
scattered showers affecting the TAF sites. Could even see
temporary IFR at KOFK 11-14z. And could even become prevailing IFR
at KLNK by 19/00z. Thunder seems possible at KLNK 16-19z, but not
confident enough to include elsewhere.


&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...Flood Watch from 10 AM CDT this morning through Wednesday
     morning for NEZ065>068-078-088>093.

IA...Flood Watch from 10 AM CDT this morning through Wednesday
     morning for IAZ079-090.

&&

$$

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



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