Damaging Winds and Heavy Rain in Iowa, June 2, 2018

Area Forecast Discussion
National Weather Service Des Moines IA
1228 AM CDT Sat Jun 2 2018

.DISCUSSION.../Tonight through Friday/
Issued at 300 PM CDT Fri Jun 1 2018

Much of the region remains under the influence of an amplified
pattern, with hot conditions present underneath a building ridge
and a deep upper level low over the northern Rockies. Much of the
state is experiencing another day in the low to mid 90s with
relatively weak and disorganized flow at the surface. Strong
southerly flow ahead of the upper level low has advected a highly
unstable airmass northward over much of the central and northern
Plains. Severe weather is likely as deep convection initiates
this afternoon and evening in a zone of enhanced frontal
convergence in central NE/SD. The threat for severe weather shifts
eastward toward the Missouri River Valley late this evening
and overnight as the storms track southeast along an instability
axis and congeal into an organized linear structure. Uncertainty
remains as to the extent of the severe weather threat in our area
overnight. Most HREF members keep the favored corridor of
instability down through southeast NE into northwest MO.
Meanwhile, the NAM/HRRR/ESRL HRRR bring the strong instability and
potential for severe weather further north into southwest Iowa.
Steep mid-level lapse rates and enhanced deep layer shear would
support a threat of some hail and damaging wind gusts, especially
if the system can remain surface based and maintain a balanced
cold pool.

Regardless of the severe weather threat showers and storms are
likely across much of the area overnight through tomorrow morning
as deep layer ascent increases with the approaching upper level
trough. Another round of showers and storms materialize Saturday
afternoon as a cold front is forced through the state. Cloud cover
and recovery issues behind the morning convection raise questions
with respect to the strength and spatial extent of the later day
activity, but at this time areas east of east of I-35 stand the
best chance to see precipitation.

Sunday looks quiet pleasant as surface high pressure settles into
the area and highs closer to seasonal normals in the 70s to low
80s. Above normal temperatures expected to return by Tuesday and
through much of next week as another ridge builds over the
Plains. Increasing moist southerly flow over the latter half of
the week will promote daily slight/low chance PoPs, but these
some of these periods should be dry as models get a better handle
on the timing of weak waves rounding the top of the ridge. Some
degree of severe weather risk will likely exist during this
period, but weak flow aloft will be a mitigating factor as the
ridge aloft forces the main jet stream north of the area.

&&

.AVIATION.../For the 06Z TAFS through 06Z Saturday night/
Issued at 1228 AM CDT Sat Jun 2 2018

A line of storms will pass through central Iowa tonight into
Saturday morning. There will be restricted visibilities and
ceilings in and around thunderstorms, otherwise generally VFR
conditions. The storms may redevelop east of the I35 corridor on
Saturday afternoon before quickly exiting the area. Widespread VFR
conditions are expected behind the front as it moves across the
state on Saturday with increasing west to northwest winds after
passage of the boundary.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...NONE.

&&

DISCUSSION...Martin
AVIATION...Cogil

Hazardous Weather Outlook
National Weather Service Des Moines IA
315 PM CDT Fri Jun 1 2018

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-
081>086-092>097-022015-
Emmet-Kossuth-Winnebago-Worth-Palo Alto-Hancock-Cerro Gordo-
Pocahontas-Humboldt-Wright-Franklin-Butler-Bremer-Sac-Calhoun-
Webster-Hamilton-Hardin-Grundy-Black Hawk-Crawford-Carroll-Greene-
Boone-Story-Marshall-Tama-Audubon-Guthrie-Dallas-Polk-Jasper-
Poweshiek-Cass-Adair-Madison-Warren-Marion-Mahaska-Adams-Union-
Clarke-Lucas-Monroe-Wapello-Taylor-Ringgold-Decatur-Wayne-
Appanoose-Davis-
315 PM CDT Fri Jun 1 2018

This Hazardous Weather Outlook is for portions of central Iowa.

.DAY ONE...This afternoon and tonight

Scattered to widespread thunderstorms are likely late tonight
into early Saturday morning. Some strong to severe storms are
possible in southwest Iowa, capable of damaging winds, hail, and
heavy rainfall.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday

Additional storms are possible Saturday afternoon and evening,
mainly east of Interstate 35. The threat for severe weather looks
low at this time.

Chances for thunderstorms return to the forecast on Wednesday and
Thursday, but the threat for severe weather remains uncertain for
that time period.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not likely at this time.

Special Weather Statement
National Weather Service Des Moines IA
148 AM CDT SAT JUN 2 2018

IAZ057-070-020745-
Audubon IA-Cass IA-
148 AM CDT SAT JUN 2 2018

...Line of Storms in Western Iowa With Strong Winds...

At 146 AM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from 7 miles northeast of Walnut to near Griswold to
near Red Oak. Movement was east at 35 mph.

Half inch hail and winds in excess of 40 mph will be possible with
these storms.

Locations impacted include...
Atlantic, Griswold, Anita, Exira, Elk Horn, Lewis, Massena,
Kimballton, Cumberland, Brayton, Marne, Wiota, Lake Anita State Park,
Griswold Park, Cold Springs State Park, Atlantic Municipal Airport
and Anita Municipal Airport.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with these storms, and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.

&&

LAT...LON 4150 9515 4151 9504 4160 9504 4160 9509
      4168 9509 4169 9475 4160 9474 4160 9470
      4116 9470 4116 9516
TIME...MOT...LOC 0646Z 272DEG 28KT 4156 9514 4127 9516 4105 9524

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