Severe Thunderstorm Warning 166, NWS Omaha, NE

Area Forecast Discussion
National Weather Service Omaha/Valley NE
620 PM CDT Sat Sep 21 2019

.SHORT TERM...(Tonight through Tuesday)
Issued at 344 PM CDT Sat Sep 21 2019

The main hazards during the short term are severe weather and
flooding.

Vigorous upper level shortwave trough moving across the Dakotas
will cause a cold front to move southeast across eastern Nebraska
and southwest Iowa this evening. Model guidance slows the front
as it moves into Southeast Nebraska tonight. At this time
southwesterly low level flow is limiting the convergence along the
front and not allowing for convective development. However, the
lull in thunderstorm development is only temporary.Expect by
23-00Z convection is forecast to develop along the front in
southeast Nebraska where ML CAPE values are presently between
2000-2500 J/KG along with 45-50 knots of effective shear. Some
Supercell storms may develop and eventual evolve into a line
along the front. Large hail and damaging winds are the primary
hazards. There is slight possibility of an isolated tornado in
southeast Nebraska. As the night progresses, more thunderstorms
are forecast along and north of the front. With some training of
storms along the front and Precipitable Water values around 1.5
inches in southeast Nebraska, have left the Flash Flood Watch for
southeast Nebraska and Fremont and Page Counties in Iowa.

Precipitation lingers into Sunday midday in the southeast.
Precipitation an clouds will start clearing out as upper trough
moves across the Northern and Central Plains during the day.
Surface high pressure then spreads across the area, bring dry
weather through Monday.

Surface return flow comes back into the area on Tuesday with weak
surface warm front in northern Kansas, Isentropic lift north of
the front is expected to develop showers and thunderstorms across
southeast Nebraska and southwest Iowa through Tuesday night.

.LONG TERM...(Tuesday night through Saturday)
Issued at 344 PM CDT Sat Sep 21 2019

Precipitation continues across the area on Tuesday night as
another shortwave trough and associated jet max moves across the
Northern and Central Plains. This drives another cold front south
across the area Tuesday night into Wednesday morning. After that,
another brief dry period is expected until Thursday afternoon and
Friday when another shortwave trough moves across the area
producing more storms.

&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 609 PM CDT Sat Sep 21 2019

Main concern for this TAF period will be storm development this
evening along and south of of a frontal boundary. LNK has the
highest chance of being impacted by evening storms. OMA also may
see evening storms, although higher chances will remain south of
the TAF site. Evening storms could be strong to severe, but
severe threat should diminish after midnight. Shower and
thunderstorms chances may continue into the morning Sunday at OMA
and LNK but are not expected to be severe.

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...Flash Flood Watch through Sunday morning for NEZ068-089>093.

IA...Flash Flood Watch through Sunday morning for IAZ090-091.

&&

SHORT TERM...Smith
LONG TERM...Smith
AVIATION...HB

Hazardous Weather Outlook
National Weather Service Omaha/Valley NE
555 PM CDT Sat Sep 21 2019

NEZ011-012-015>018-030>033-042-043-221300-
Knox-Cedar-Thurston-Antelope-Pierce-Wayne-Boone-Madison-Stanton-
Cuming-Platte-Colfax-
555 PM CDT Sat Sep 21 2019

This Hazardous Weather Outlook is for portions of northeast
Nebraska.

.DAY ONE...Tonight and Sunday

Minor to locally moderate flooding will continue along the
Missouri River above Lewis and Clark Lake, and from near Decatur
southward past Rulo.

.DAYS TWO THROUGH SEVEN...Sunday night through Saturday

Missouri River levels will continue to rise south south of
Brownville through Monday, then begin to fall through the week.
North of Brownville river levels should be on the decline. Minor
to moderate river flooding will continue along most of the
Missouri River in Nebraska/Iowa through next week.

There will be a couple chances for thunderstorm activity next
week, with the most likely period for stronger storms occurring
between Thursday and Saturday.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will not be needed tonight and Sunday.

IAZ043-055-056-069-079-080-090-091-NEZ034-044-045-050>053-065>068-
078-088>093-221300-
Monona-Harrison-Shelby-Pottawattamie-Mills-Montgomery-Fremont-
Page-Burt-Dodge-Washington-Butler-Saunders-Douglas-Sarpy-Seward-
Lancaster-Cass-Otoe-Saline-Jefferson-Gage-Johnson-Nemaha-Pawnee-
Richardson-
555 PM CDT Sat Sep 21 2019

This Hazardous Weather Outlook is for portions of southwest
Iowa...west central Iowa...east central Nebraska and southeast
Nebraska.

.DAY ONE...Tonight and Sunday

A Flash Flood Watch remains in effect over parts of southeastern
Nebraska and southern Iowa from 7 PM this evening through 10 AM
Sunday. Some thunderstorms will be capable of producing high
rainfall rates culminating in 1 to 3 inches of rainfall with
locally higher amounts possible.

Severe thunderstorms are possible tonight generally along and
south of Interstate 80. The primary threats are large hail and
damaging winds. There is also a slight chance of a tornado in
southeast Nebraska.

Minor to moderate flooding will continue along the Missouri River
above Lewis and Clark Lake, and from near Decatur southward past
Rulo.

Thunderstorms will be possible on Saturday.

.DAYS TWO THROUGH SEVEN...Sunday night through Saturday

Missouri River levels will continue to rise south south of
Brownville through Monday, then begin to fall through the week.
North of Brownville river levels should be on the decline. Minor
to moderate river flooding will continue along most of the
Missouri River in Nebraska/Iowa through next week.

There will be a couple chances for thunderstorm activity next
week, with the most likely period for stronger storms occurring
between Thursday and Saturday.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is likely tonight over southeast Nebraska and
southwest Iowa.

Smith

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