Severe Thunderstorm Warning 155, NWS Omaha, NE

Area Forecast Discussion
National Weather Service Omaha/Valley NE
324 AM CDT Mon Aug 10 2020

...Updated Forecast Discussion...

.DISCUSSION...
Issued at 210 AM CDT Mon Aug 10 2020

A surface cold front is currently draped across the area starting
from northeast Colorado extending northeastward to to just east
of Minneapolis, Minnesota. A nocturnal 850mb jet is oriented
parallel to the cold front and becomes westerly as it reaches far
eastern Nebraska/western Iowa.

These two factors are combining to force some modest convection
along NE/SD border, with more convection beginning to sprout up,
extending westward into south-central South Dakota. The
orientation of the low-level jet is providing some convergence
along the front, but since it is oriented parallel to it, that
convergence is not overly strong. Surface CIN values are lowest
just ahead of the front at around 140 J/kg in far northeast
Nebraska and increase along the front as you go southwestward.
Surface based CAPE values associated with the CAPE minimum have
slightly declined to around 3500 J/kg but still allow for strong
convection to occur. The latest runs of the HRRR, ESRL HRRR, and
RAP suggest that a cluster of storms may move eastward along with
the zonal flow aloft, but if robust convection does get going a
strong cold pool may allow for a more southeastward propagation to
occur with the primary hazard being damaging wind gusts.

As the today continues, the cold front is expected to march
southeast and is expected to make its way to northwest Missouri by
00z Tuesday, and will bring cooler temperatures ranging from the
upper 70's in the northwestern CWA to the mid to upper 80's in
the far southeastern corner. Isolated to scattered showers and
storms will be possible as the front passes through the area but
with limited development in the model solutions, limited activity
is expected.

Looking beyond today's forecast, Tuesday is expected to be dry
after any lingering precipitation from the frontal passage exits
the area early in the morning. Highs in the mid to upper 80's are
expected throughout eastern Nebraska as southeasterly surface flow
returns. Global deterministic models are currently hinting at the
possibility of a nocturnal MCS that could begin in western NE/SD
and propagate ESE forming an MCV and bringing overnight and early
morning rain chances to eastern Nebraska. This scenario is also
depicted once again Wednesday evening/Thursday morning with the
main difference being the propagation of the nocturnal MCS, with
the GFS keeping it north of the area and the ECMWF passing it
through southeastern Nebraska.

Beginning Wednesday, mid-level ridging begins building over
southern New Mexico and will slowly begin shifting the mid-level
flow northwesterly. Beyond the Wednesday and Thursday nights'
storm chances, the bulk of any activity is expected to stay more
into Iowa as different shortwave impulses push through the mid-
level flow. High temperatures are expected to stay in the upper
80's to around 90, with no real scorchers expected. Model
solutions begin to diverge Sunday, with the ECMWF depicting a cold
front to pass through the area, while the other global solutions
depict a very limited response in surface temperatures and wind
direction. If this front comes to fruition, we could enjoy
another trip into the lower 80's for highs to start off next week.

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1143 PM CDT Sun Aug 9 2020

Convection has developed along the NE/SD border, moving quite
slowly, but should remain north of the KOFK TAF. Additional
thunderstorms are expected north of both KOFK and KOMA, although
KOFK could see an isolated shower 11-14z. There is a cold front
coincident with this activity, and this front will shift winds to
the north and increase to 12-14 knots with the initial surge, then
settling back into the 9-12 knot range by 16z. Otherwise, VFR
through the period.

&&

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

DISCUSSION...Petersen
AVIATION...DeWald

Hazardous Weather Outlook
National Weather Service Omaha/Valley NE
434 AM CDT Mon Aug 10 2020

IAZ043-055-056-069-079-080-090-091-NEZ011-012-015>018-030>034-
042>045-050>053-065>068-078-088>093-102345-
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-
434 AM CDT Mon Aug 10 2020

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

.DAY ONE...Today and Tonight

Isolated showers and storms are possible this morning and today
as a cold front continues to move southeast through the area. The
front is expected to reach far southeast Nebraska by 7pm and may
stall out after the it crosses into northeast Kansas/northwest
Missouri. While an isolated storm or two may become severe,
widespread severe activity is not expected at this time. The best
chance for any severe activity will be in far southeast Nebraska,
extending into KS/MO.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday

Periodic showers and storms continue to be possible into this
weekend. Severe storm potential is uncertain at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.