Flooding and Damaging Winds in Nebraska, May 26 to 27, 2019

Area Forecast Discussion
National Weather Service Omaha/Valley NE
624 PM CDT Sun May 26 2019

.SHORT TERM...(Tonight through Wednesday)
Issued at 330 PM CDT Sun May 26 2019

Main concerns in the short term and potential for severe storms
and heavy rain this evening into tonight. Also concerned about
Tuesday but mesoscale details may change a lot compared to what
model output shows for that period.

Upper air analysis from 12Z this morning had the following
features of note. At 850 mb there was an axis of higher dewpoints
in the teens C from west TX up into much of KS. Warm pocket was
over NM with cold pocket in MN. At 700 mb a thermal ridge extended
from TX back into CO. At 500 mb, we were in west/southwest flow
with a very strong closed low dropping south from northern CA. 12
hour height falls in excess of 200 meters were noted with that
feature. There was also a trough located from southern CA down
into the Baja region. Winds were 50-60 knots over parts of AZ and
NM. At 300 mb, a jet streak of around 120 knots was over the Great
Lakes and another was off the CA coast on the west side of the
previously mentioned closed low at 500 mb. Strongest winds at the
200 mb level were about 120 knots near the Mexico/NM border. 20Z
surface analysis showed our area in south/southeast flow with
dewpoints mostly in the lower or mid 60s across the southern part
of the forecast area and drier air to the north. There was a weak
boundary extending from northern MO northwest toward Albion.

Short range CAMs show that thunderstorm coverage will increase for
the evening and overnight hours. Storms this evening may be strong
to severe with some hail and wind threat. Later tonight it appears
that a linear MCS will move from west to east through the area
with mainly a wind and heavy rain threat. SPC has a slight or
marginal risk for our area and that seems reasonable. We issued a
flash flood watch for about the southeast 2/3 of the forecast area
when there wettest ground and higher rain amounts should coincide.

On Monday, much of the afternoon may be dry after morning
showers/ storms move out. A lot will depend on what happens
tonight. For Monday night, we should see some storms but models
are not in very good agreement. Highest probabilities may be up
over northeast NE at least in the evening, north of a nearly
stationary front.

Enhanced risk of severe for the overall pattern Tuesday looks on
track, as we will be in a favorable synoptic pattern. There will
be strong mid/upper level divergence, decent CAPE and shear.
Details of any boundaries will be important for storm scale
structures/threats.

Closed low at 500 mb is currently expected to be back over the
panhandle of NE at 7 pm Tuesday, then that will only move slowly
to the east through Thursday will gradually weakening. This is a
slower trend than the past few days and further slowing of this
system moving away from our area is possible with future model
runs.

.LONG TERM...(Wednesday night through Sunday)
Issued at 330 PM CDT Sun May 26 2019

The longer term period does not look completely dry but storm
threat will be less. Lows should be mostly 50s to around 60 and
highs in the 70s to lower 80s. Highest rain chances look to be
Saturday into Saturday night.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 611 PM CDT Sun May 26 2019

VFR conditions are expected through much of the TAF period however
scattered thunderstorms overnight could hit the TAF sites with
strong winds the main hazard in addition to heavy rain. Variable
conditions will be possible in and around thunderstorms.

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...Flash Flood Watch from 10 PM CDT this evening through Monday
     morning for NEZ034-044-045-050>053-065>068-078-088>093.

IA...Flash Flood Watch from 10 PM CDT this evening through Monday
     morning for IAZ043-055-056-069-079-080-090-091.

&&

SHORT TERM...Miller
LONG TERM...Miller
AVIATION...Kern

Hazardous Weather Outlook
National Weather Service Omaha/Valley NE
829 PM CDT Sun May 26 2019

IAZ043-055-056-069-079-080-090-091-NEZ011-012-015>018-030>034-
042>045-050>053-065>068-078-088>093-271530-
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-
829 PM CDT Sun May 26 2019

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 Monday

Some strong to severe storms will continue to develop across
across parts of eastern Nebraska this evening. The main hazards
are expected to be large hail and strong winds, but there is also
a small chance that isolated short lived tornadoes could develop.
Some storms could also produce heavy rain. Later tonight, storms
will continue to spread eastward. These storms could also be
severe. A flash flood watch is in effect for parts of eastern
Nebraska and most of western Iowa.

Storms may linger until a few hours after sunrise. Storm chances
in the afternoon look fairly low at this time.

Minor to moderate river flooding will continue along the Missouri
River from Plattsmouth south to Rulo.

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

Storm chances will return for Monday evening into Monday night.

Forecaster confidence in a potentially significant severe weather
event Tuesday afternoon and evening continues to increase. At
this time all hazards appear to be on the table, including very
large hail, damaging winds and a few tornados.

Minor to moderate river flooding will continue along the Missouri
River from Plattsmouth south to Rulo.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will probably not be needed this evening or
tonight, but if you observe any severe weather or flooding, please
give us a report or a call. Spotter activation is not expected at
this time for Monday.