Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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FXUS63 KOAX 310439
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
1139 PM CDT MON MAY 30 2016

.SHORT TERM...(tonight through Thursday)
Issued at 329 PM CDT Mon May 30 2016

Chance for thunderstorms through Tuesday early evening is the
primary forecast concern in the short term.

Main driver for thunderstorms later tonight and Tuesday is a short
wave diving into northern Montana this afternoon and associated cold
front that will swing through our warning area late tonight and
Tuesday. Ahead of those features, a weak perturbation was noted on
water vapor imagery and RAP analysis from eastern Nebraska into
eastern Oklahoma. More pronounced forcing was well to our south
where storms had bubbled up in Kansas and Missouri earlier this
afternoon. But several runs of various short range hi-res model
output have suggested convection will fire this afternoon farther
north in our southeast CWA, and indeed that has happened. Mixed-
layer CAPE from RAP analysis indicated 3000 j/kg bullseye in far
northwest Missouri with CAPE ridge noted along middle Missouri
River valley region. Shear profiles are pretty tame in this area,
with a slow northeastward drift to activity. Expect storms in
southeast Nebraska and southwest Iowa to continue to bubble up
late this afternoon, and given high CAPE environment, could see a
few strong storms with hail the primary threat, though a brief
strong wind gust could happen with collapsing storms. HRRR/RAP
show storms diminishing with loss of daytime heating, so have a
decrease in activity represented in grids this evening.

Attention then turns to storms along approaching cold front. That
front is slated into northeast Nebraska by around 06Z as short wave
rolls into the northern plains. Forecast soundings from NAM/GFS show
1500 j/kg of elevated CAPE will be in place ahead of this boundary,
but shear profiles are lacking across eastern Nebraska with stronger
mid level flow closer to short wave well to the north. While there
will still be some severe risk past midnight, chances will become
increasingly lower as storms become more and more elevated with
time.

Front will lose its southeast momentum late tonight and Tuesday and
only slowly drift through our southeast CWA by late afternoon.
Scattered showers and storms will continue along and behind the
front through the day, with best, albeit slight, chance for severe
in the afternoon over southeast Nebraska and southwest Iowa where
highest theta-e surface air will reside. Again mainly vertical storm
structures are expected given low shear environment, thus hail and
downbursts are possible.

Front should sweep precip chances to our south and east Tuesday
evening. Much of the rest of the short term period will be dry as
heights slowly rise in wake of exiting northern plains short wave.
There is a small chance for convection Thursday as a weak impulse
induces mid level warm advection regime over returning surface
moisture in northeast Nebraska. Have included a slight chance for
storms there on Thursday.

Otherwise temperatures should average the 70s for highs through
Thursday, with Tuesday and Wednesday favoring the low to mid 70s
when clouds/precip/colder airmass are in place, then mid to upper
70s Thursday as south to southwest winds return.

.LONG TERM...(Thursday night through Monday)
Issued at 329 PM CDT Mon May 30 2016

Another short wave and cold front moving through the region Friday
will bring our next chance for thunderstorms, with the rest of the
weekend looking dry.

A quasi-zonal flow regime will be in place to begin the longer term
period before an impulse emerges from the northern Rockies and moves
across the northern plains on Friday. This wave will push another
weak cold front into the central plains on Friday, providing a focus
for storms then. Again better forcing will reside nearer short wave
in the Dakotas, but modest moisture return and heating ahead of
front will provide plenty of fuel for at least scattered storms. GFS
indicates surface based CAPE over 2000 j/kg with 35kt of 0-6km bulk
shear. Will maintain our chance for storms Friday into Friday night
before front sweeps southeast. Then northwest mid level flow takes
over for the weekend, bringing a mainly dry forecast.

Temperatures will likely surge well into the 80s on Friday before
moderating into the 70s or lower 80s for the weekend.

&&

.AVIATION...(06Z TAFS for KOMA...KLNK...KOFK through 06Z Wednesday)
Issued at 1138 PM CDT Mon May 30 2016

Mainly VFR conditions are expected through the TAF cycle.
Thunderstorms may bring short-lived vis/ceiling reductions to MVFR
category, affecting KOFK imminently and KLNK/KOMA overnight.
Potential for showers and thunderstorms will linger at KOMA/KLNK
this afternoon, but with low confidence in timing, duration, and
coverage, have continued to use a PROB30 mention for now. Winds
will shift to northwesterly behind the overnight line of
thunderstorms but should remain at or below 10kt.

&&

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

$$

SHORT TERM...Dergan
LONG TERM...Dergan
AVIATION...Mayes



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