Special Weather Statement, NWS Omaha, NE

Area Forecast Discussion
National Weather Service Omaha/Valley NE
1221 AM CDT Fri Sep 17 2021

...Updated Aviation Forecast Discussion...

.DISCUSSION...
Issued at 349 PM CDT Thu Sep 16 2021

Today and Tomorrow:
Clear skies, warm temperatures, and strong south winds are
dominating the area today. As of 3 pm, many areas have reached 90
degrees or are inching toward it. Temperatures are expected to
peak in the low 90s. The warm temperatures won't continue into
tomorrow as a cold front will move through the area tonight.

Storms are expected to develop behind the front with initiation
near 1 am. This is a bit later than what was forecast from the
morning forecast package. Any storm development won't fully be
able to take advantage of the instability enhanced by today's
plentiful sunshine. ML CAPE values this afternoon are expected to
top out near 2000 J/kg. By time of storm initialization, that ML
CAPE should have dropped below 1000 J/kg. Storms are expected to
be elevated, but with high LCL and LFC heights, it may be
difficult for strong storms to develop. If any strong storms do
develop, the shear profile could support severe criteria hail
initially. The hail potential should drop off quickly after
midnight. The HRRR and RAP show DCAPE values between 1000 to 1500
J/kg before midnight which is supportive of a severe wind gust
threat. If storms can be sustained, strong winds would be the
primary concern after midnight.

The front will slow, and perhaps even stall out over southern
Nebraska and Iowa tomorrow morning. Shear vectors parallel to the
boundary and precipitable water values near 1.5" support a
marginal risk for excessive rainfall. CAM models suggest a
secondary line of precipitation will develop across southern
Nebraska and travel along the stalled boundary into southwest
Iowa. This secondary line of precipitation could linger into the
late afternoon.

For tomorrow, outside of early day precipitation, expect strong
northerly winds behind the front with gusts up to 25 mph. Those
winds should begin to diminish in the early afternoon. Depending
on your location, temperatures should be 10 to 15 degrees cooler
tomorrow than today.

Saturday and Sunday:
A ridge is forecast to build over the Plains this weekend leading
to clear skies, no precipitation, and warming temperatures. Highs
on Saturday are forecast to be in the mid 80s while Sunday should
see temperatures in the low 90s.

Monday through Wednesday:
The primary weather concern in this period will be a deep upper
level trough that is expected to impact the northern Plains on
Monday. The GFS/ECMWF/Canadian are in good agreement on timing,
but do differ in precipitation placement. The best lift for
precipitation appears to be to the north and east, but there is
about a 55% chance for rain across the area. The attendant cold
front will result in cooler temperatures. Though, that will be
cooler relative to the previous few days, as the cool down will
result in temperatures right around the climatic normal.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1221 AM CDT Fri Sep 17 2021

Main question remains storm potential and related timing as a cold
front slides through. With most guidance suggesting at least
scattered showers and storms around each TAF site, included VCTS
mention for each site, though exact timing will likely need to be
updated. Expect brief MVFR conditions with any storm that directly
impacts a site along with gusty winds.

Otherwise, expect a period of LLWS early in the period followed by
at least a couple hours of MVFR ceilings following any
precipitation. Also could see some northerly wind gusts in the 20
to 25 kt range behind the front before they taper off and become
more northeasterly by Friday evening.

&&

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

DISCUSSION...Fajman
AVIATION...CA

Hazardous Weather Outlook
National Weather Service Omaha/Valley NE
948 PM CDT Thu Sep 16 2021

IAZ043-055-056-069-079-080-090-091-NEZ034-044-045-050>053-065>068-
078-088>093-171700-
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-
948 PM CDT Thu Sep 16 2021

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

.DAY ONE...Tonight and Friday

Strong thunderstorms north and west of the area tonight will
continue to slip south and east overnight and may affect parts of
eastern Nebraska and western Iowa before sunrise. These storms
will be weaker as they continue south and east. Isolated
thunderstorms are possible through the day on Friday as the front
slips south.

.DAYS TWO THROUGH SEVEN...Friday night through Thursday

More thunderstorms are forecast Monday night into Wednesday when a
deep low pressure system drifts through the region.

.SPOTTER INFORMATION STATEMENT...

Spotters should not be needed tonight or tomorrow.

NEZ011-012-015>018-030>033-042-043-171700-
Knox-Cedar-Thurston-Antelope-Pierce-Wayne-Boone-Madison-Stanton-
Cuming-Platte-Colfax-
948 PM CDT Thu Sep 16 2021

This Hazardous Weather Outlook is for portions of northeast
Nebraska.

.DAY ONE...Tonight and Friday

Severe thunderstorms with large hail and damaging winds are
possible overnight in northeast Nebraska and west central Iowa,
generally along and north of a line from Columbus to West Point
and Onawa.

Most of the thunderstorms will be trailing behind the cold front
sweeping through the area. Large hail and damaging winds are the
primary threats. These storms will weaken as they push south and
east.

.DAYS TWO THROUGH SEVEN...Friday night through Thursday

More thunderstorms are forecast Monday night into Wednesday when
a deep low pressure system drifts through the region.

.SPOTTER INFORMATION STATEMENT...

Spotters should not be needed tonight or tomorrow.

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Special Weather Statement
National Weather Service Omaha/Valley Nebraska
1138 PM CDT Thu Sep 16 2021

NEZ011-170515-
Knox NE-
1138 PM CDT Thu Sep 16 2021

...A strong thunderstorm will impact portions of northern Knox County
through 1215 AM CDT...

At 1138 PM CDT, Doppler radar was tracking a strong thunderstorm near
Niobrara, or 22 miles south of Tyndall, moving northeast at 40 mph.

HAZARD...Winds in excess of 40 mph and half inch hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Locations impacted include...
  Santee.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

&&

LAT...LON 4284 9769 4286 9761 4285 9757 4258 9799
      4270 9814 4278 9807 4276 9804 4277 9795
      4279 9791 4282 9788 4286 9788 4287 9786
TIME...MOT...LOC 0438Z 223DEG 36KT 4268 9803

MAX HAIL SIZE...0.50 IN
MAX WIND GUST...40 MPH

Kern

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