Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000
FXUS63 KOAX 201733
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
1233 PM CDT Tue Jun 20 2017

.SHORT TERM...(Today through Thursday night)
Issued at 330 AM CDT Tue Jun 20 2017

Forecast concerns in the short term will be multiple chances for
thunderstorms as a warm front lifts north of the forecast area
later this afternoon and tonight....a cold front pushes into
northeast Nebraska Wednesday afternoon...however stalls...then
settles southward Thursday.

Temperatures today were near or above normal mostly from 85 to 90
degrees...with the sprinkles exiting the area early in the day and
plenty of sunshine in the afternoon. Once again, the 00Z OAX
sounding showed a well-mixed profile...to 630mb. Tonight...clear
skies dominate with calm to light and variable winds and
temperatures in the 50s and 60s...with dewpoints in the 50s.

Water vapor satellite imagery highlights the closed low over the
Gulf of Alaska with northwest flow and mid level moisture
streaming into the Northern Plains. A broad h5 ridge prevails over
much of the western U.S. with a trough over the Great Lakes/Ohio
River Valley.  Height rises were spotted across much of the
southwest U.S. into the Central Plains.

A shortwave trough over the Dakota is forecast to slide into Iowa
today with a strengthening low level jet from western Kansas into
southern Nebraska with and h85 boundary lifting toward the
Nebraska/Kansas border. Moisture is forecast to be pooled in this
area with a narrow instability area from 1000-2000j/kg near the
boarder that broadens over southwest Nebraska into western Kansas
with 2-4K j/kg and K-index values of 40 to 50.

The RAP/HRRR/SPC HRRR and operational NAM12/GFS/EC/CMC keep the
precip to the west through 00z...with some spotty storms into
southeast Neb by 06z...possibly others farther north...then storms
skipping over much of the area...but clipping northeast Nebraska
into western Iowa between 06z-12Z. Since we are uncapped...and
moisture is returning...seems prudent to include isolated to
scattered pops for this feature as the warm front lifts north.
The day one SPC outlook has us in the general thunder area with
parts of SD Marginal and western KS in the slight risk.
Instability is not too high in our area, however a band of
stronger winds aloft with 0-3km bulk shear of 40 to 50kts could
enhance the storms across the northeast Nebraska into Iowa.
The 06Z nam12 came in a bit more aggressive with the storms late
tonight and wednesday morning across the northeast third of the
forecast area. If this trend persists...will need to add in more
thunderstorms and extra clouds would affect highs for Wed.

Wednesday...much warmer temperatures build into the forecast area
(+22-6 deg C at H85 and 14deg C at h7) and the next shortwave in
the flow aloft is forecast to drop southeast. How the storms
evolve Wednesday is a bit more uncertain as there will be decent
instability of 2000-4000 j/kg and moisture along with convergence
along the front. To what extent will the storms develop. for now
have chance pops in northeast Nebraska...and bring those southward
during the evening and overnight. The slight risk for severe
weather is over area especially north of the Platte River into
west central Iowa.  The surface boundary will be push south with
the convection...however due to the flow aloft should somewhere
between east central Nebraska and west central Iowa or a little
farther north as the flow aloft becomes more westerly and faster
aloft.

Thursday afternoon and Thursday night...there is good agreement by
the models that along the front...storm will increase in coverage
and continue to push southward overnight as the shortwave pushes
through the trough. Have fairly high likely pops.  The day 3
outlook for Thursday has a slight risk for severe storms all along
the front. CAPE of 2000-3000J/kg is forecast along the
front...along with a belt of stronger 40-50kt 0-3km bulk
shear...which would promote damaging winds.

Highs today would be a touch warmer in the 80s and 90s. The
dewpoints rise for Wednesday, so more humid with highs in the 90s
most places. Thursday as the front slips south...highs in the 80s
near the SD border to the lower 90s near the KS/MO borders

.LONG TERM...(Friday through Monday)
Issued at 330AM CDT Tue Jun 20 2017

...Much cooler weather heading to our area for the weekend...

The pattern will see a trough over the upper Mississippi Valley
into the Great Lakes that affect our area with much cooler h85
temperatures and a prevailing north flow. Highs Friday through
Monday should mostly be in the 70s with more 80s by Monday.
Lows are expected to be in the 40s and 50s after Friday morning.

Friday through Saturday night, we still have some periodic
chances for showers and thunderstorms, however the models are a
bit varied on their timing, but do agrees with the chance
Saturday. Sunday and Monday are looking mainly dry.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1232 PM CDT Tue Jun 20 2017

No aviation concerns this forecast cycle as VFR conditions
will dominate. There are a number of TAF lines due to expected
changes in wind direction.

&&

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

$$

SHORT TERM...Zapotocny
LONG TERM...Zapotocny
AVIATION...Pearson


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