Severe Thunderstorm Warning 66, NWS Omaha, NE

Area Forecast Discussion
National Weather Service Omaha/Valley NE
634 PM CDT Mon May 15 2017

.SHORT TERM...(Tonight through Thursday)
Issued at 320 PM CDT Mon May 15 2017

WV imagery this afternoon showing a deep longwave trof over the
western CONUS with a closed off low/potent vort max currently
digging southward through southern CA heading toward Baja.
Meanwhile...surface low pressure was centered in eastern CO with
attendant thermal boundary extending northeastward into south-
central MN. Good moisture advection into the central Plains
continues per VWPs showing anywhere from 20-30kts just off the
deck. This, along with daytime heating has allowed quick
environmental destabilization with MLCAPE ranging 1500-2500 J/kg
over the region. Strong CAP though remains in place.

For tonight...appears that another round of convection will develop
this evening west of the CWA on the nose of strengthening low
level jet. Both HRRR/RAP13 show a small cluster of thunderstorms
initiating in western KS late this afternoon/early evening along
axis of boundary layer theta-E convergence/steep mid-level lapse
rates 8C/km. Activity is progged to push into the CWA then shortly
before midnight. And at this point...it appears the brunt of
activity will push across the northern CWA.

Tuesday afternoon...western shortwave trof eventually bottoms out
just south of the 4-corners region with leeside cyclogenesis
ensuing. Both the NAM/GFS prog impressive thrust of gulf moisture
into the central Plains culminating in PWS increasing to 1.75".
Convection...once CINH weakens...will likely form on the edge of a
dry line extending from north-central Neb to western KS and
increase in areal coverage heading into the evening hours.

With impressively steep lapse rates over top stout low level
moisture...seems quite probable several storms will be large hail
producers during the early evening hours. In addition...a heavy rain
threat is on the table as well. Precipitation efficiency will be
relatively high given deep warm cloud layer/strong low level
inflow/high environmental moisture content coincident to 20-30
microbars of omega. Interestingly enough...both HIRES ARW/NMM show
storms transitioning to a bowing line over the CWA toward mid
evening.

Lingering wrap around precip looks possible on Wednesday as the
central Plains vort max pivots and lift through the CWA into the
upper Midwest.

.LONG TERM...(Thursday night through Monday)
Issued at 320 PM CDT Mon May 15 2017

Precip chances continue Thursday afternoon through at least Saturday
morning in association with a large and relatively slow moving
system ejecting out of the central Rockies before lifting into the
Dakotas then the upper Midwest. A cooler air mass is then progged to
push southward into the region in the wake of the exiting system.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 628 PM CDT Mon May 15 2017

VFR conditions are indicated at all sites through the TAF cycle.
That said, VCTS is mentioned at KOFK and KLNK as the potential for
showers/storms skirts near both sites this evening. Should storms
pass over either site, short-lived MVFR to IFR conditions are
possible. Low-level wind shear potential follows later tonight
into the early morning at KOFK and KLNK. Winds will increase at
all sites in the mid-morning.

&&

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

SHORT TERM...DEE
LONG TERM...DEE
AVIATION...Mayes

Hazardous Weather Outlook
National Weather Service Omaha/Valley NE
425 PM CDT Mon May 15 2017

IAZ043-055-056-069-079-080-090-091-NEZ011-012-015>018-030>034-
042>045-050>053-065>068-078-088>093-161130-
Monona-Harrison-Shelby-Pottawattamie-Mills-Montgomery-Fremont-
Page-Knox-Cedar-Thurston-Antelope-Pierce-Wayne-Boone-Madison-
Stanton-Cuming-Burt-Platte-Colfax-Dodge-Washington-Butler-
Saunders-Douglas-Sarpy-Seward-Lancaster-Cass-Otoe-Saline-
Jefferson-Gage-Johnson-Nemaha-Pawnee-Richardson-
425 PM CDT Mon May 15 2017

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHWEST
IOWA...WEST CENTRAL IOWA...EAST CENTRAL NEBRASKA...NORTHEAST
NEBRASKA AND SOUTHEAST NEBRASKA.

.DAY ONE...TONIGHT AND TUESDAY

Thunderstorm chances will increase overnight as activity develops
on the nose of a strengthening low level jet. A cluster of storms
are expected to increase in areal coverage this evening in central
Nebraska before shifting into mainly eastern Nebraska by late
evening, continuing overnight. There is just a small chance of
storms across southwest Iowa. A few of these storms may be
accompanied by hail up to one inch and strong wind gusts in
northeastern Nebraska.

Severe storms will again be possible by Tuesday mid to late afternoon,
especially across eastern Nebraska. Large hail and damaging winds,
along with locally heavy rainfall can be expected with these storms.

.DAYS TWO THROUGH SEVEN...TUESDAY NIGHT THROUGH MONDAY

Severe thunderstorm activity will likely persist through Tuesday
night. Large hail and damaging winds are the main threats. In
addition to this...a moisture rich environment will create
favorable conditions for locally heavy rainfall during the
overnight hours.

Thunderstorms will be possible again Wednesday as well as
Thursday evening.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will probably not not be needed tonight, but
may be needed Tuesday afternoon and night.

Special Weather Statement
National Weather Service Omaha/Valley Nebraska
1012 PM CDT MON MAY 15 2017

NEZ050-065-078-160330-
Seward NE-Butler NE-Saline NE-
1012 PM CDT MON MAY 15 2017

...Significant Weather Advisory for SEWARD...NORTHERN SALINE AND
BUTLER COUNTIES UNTIL 1030 PM CDT...

At 1010 PM CDT, Doppler radar was tracking an outflow boundary from
strong thunderstorms along a line extending from 3 miles north of
Osceola to 4 miles south of Utica to near Milligan. Movement was
east at 50 mph.

Winds in excess of 40 to 45 mph will be possible with this outflow
boundary.

Locations impacted include...
Seward, Crete, David City, Milford, Friend, Utica, Dorchester,
Bellwood, Beaver Crossing, Rising City, Brainard, Staplehurst,
Garland, Dwight, Bee, Ulysses, Goehner, Cordova, Octavia and Bruno.

This includes the following highways...
 Highway 92 IN Nebraska between mile markers 409 and 430.
 Interstate 80 IN Nebraska between mile markers 366 and 385.

LAT...LON 4055 9737 4135 9737 4139 9692 4060 9695
TIME...MOT...LOC 0310Z 255DEG 50KT 4122 9756 4084 9737 4054 9740

DEWALD

Special Weather Statement
National Weather Service Omaha/Valley Nebraska
1025 PM CDT MON MAY 15 2017

NEZ016-030-160400-
Boone NE-Antelope NE-
1025 PM CDT MON MAY 15 2017

...Significant Weather Advisory for SOUTHWESTERN ANTELOPE AND
NORTHWESTERN BOONE COUNTIES UNTIL 1100 PM CDT...

At 1025 PM CDT, Doppler radar was tracking a strong thunderstorm 11
miles east of Bartlett, or 38 miles northeast of Ord, moving
northeast at 40 mph.

Nickel size hail and winds in excess of 40 mph will be possible with
this storm.

Locations impacted include...
Neligh, Elgin and Clearwater.

This includes Highway 275 IN Nebraska between mile markers 31 and 41.

LAT...LON 4227 9818 4214 9798 4195 9797 4180 9829
      4210 9830
TIME...MOT...LOC 0325Z 233DEG 35KT 4192 9833

DEWALD

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