Unrated tornado, Berkley to Ogden, Iowa, May 26, 2020

Area Forecast Discussion
National Weather Service Des Moines IA
1246 PM CDT Tue May 26 2020

.DISCUSSION.../Today through Monday/
Issued at 420 AM CDT Tue May 26 2020

Summary...

Wet and stormy conditions will continue over the next couple of
days, with the best opportunity for strong to severe storms later
today. Of growing concern may be hydrologic issues with the
potential for additional periods of moderate to heavy rainfall in
areas that have already received around 2 to 4 inches over the last
48 hours. Drier and cooler conditions will move in at the end of the
week, though a few showers/storms may scoot through Saturday into
Sunday.

Today and Tonight...

While it is a different day, the story appears to remain relatively
the same with another round of storms associated with a surface low
and associated MCV riding northward within the mean flow. As such,
we will also have another opportunity for strong to severe storms by
the afternoon and evening. Initial wave of storms this morning
should remain sub-severe with current widespread convection/precip
limiting organization within a marginally supportive environment.
Environment becomes more supportive by the afternoon though as the
surface low approaches NE/IA/MO border areas including, MUCAPE
values 1500-2000 J/kg, roughly 30-40 kts 0-3km and 0-6km shear, 150-
200 m2/s2 SRH, 0-3km CAPE around 100 J/kg, backing low level winds
resulting in better veering hodographs of varying degrees (model of
choice dependent), etc... All in all, not a slam dunk for severe,
but given recent results, another fair setup for some low level
turning/stretching resulting in the SPC 5% tor threat. Cannot rule
out other severe modes, but suggestions are that long lived
organization may be difficult to come by to achieve severe hail or
prolonged wind threats.

On top of that, moderate to heavy rainfall will also be a threat
once again with PWats remaining around 1.50 to 1.75 inches with the
sustained Gulf moisture stream. With antecedent conditions being on
the wet side across much of southern and central IA, river and
overland flooding risks do increase. Fortunately, this system will
be progressive and will not setup the wettest areas of the state for
prolonged training storms. Another 1 to 2+ inches may be possible,
but believe southern and central Iowa can handle it without much
consequence. As such, have shied away from a flood watch, though
western and southern neighbors have done so. Northwest IA where
surface boundary will set up will also be of concern for heavy
rainfall, but those areas have only seen around an inch to inch and
a half or less over the last 2 days, setting them up to handle
additional rainfall well. WPC has a slight risk for excessive
rainfall along the MN/IA border, which makes sense with the
potential for heaviest rainfall/longer training of storms into MN
versus IA.

Wednesday through Thursday...

Additional storms will be likely as the upper level trough cuts off
and meanders in the TX/OK/AR/LA region for a couple of days before
becoming absorbed into the broader flow. As that occurs, portions of
Iowa will see a lingering surface boundary that will act as a focus
for continued shower/storm activity. With Gulf moisture remaining,
expect conditions to remain quite wet. SW and C Iowa will likely
need to be monitored for flooding threats though, as well as other
portions of the state as heavy rainfall threat area continues to be
honed in. Obviously boundary location will play a major role as to
which areas will see the most rain within this time frame, and best
estimates right now are roughly the southeast half of the state.

Friday through Monday...

As the cutoff upper level low fills in NW flow will prevail,
yielding drier and cooler conditions Friday. While the cooler
conditions will continue, the dry conditions may not as synoptic
guidance is in fair agreement of a shortwave moving through Saturday
into Sunday producing a few shower chances. Expect temperatures to
fall back into upper 60s to lower 70s through the weekend before
rising back into the 80s early next week as ridging returns.

&&

.AVIATION.../For the 18Z TAFS through 18Z Wednesday afternoon/
Issued at 1246 PM CDT Tue May 26 2020

Numerous showers and embedded thunderstorms are expected this
afternoon into the early evening across central Iowa. Anticipate
MVFR to IFR conditions in and around the thunderstorms with
southeast winds in most locations. Lower ceilings and areas of
light fog are expected late tonight with MVFR to IFR ceilings,
especially along and west of Lamoni (KLWD) to Mason City (KMCW).

&&

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

&&

DISCUSSION...Curtis
AVIATION...Cogil

Hazardous Weather Outlook
National Weather Service Des Moines IA
424 AM CDT Tue May 26 2020

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-
081>086-092>097-270930-
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-
424 AM CDT Tue May 26 2020

This Hazardous Weather Outlook is for portions of central Iowa.

.DAY ONE...Today and tonight

A round of non-severe showers and thunderstorms will cross the
region this morning. Strong to severe thunderstorms are expected
this afternoon with damaging winds, a few quickly forming tornadoes
possible and locally heavy rainfall that may lead to localized
flooding.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday

Several more rounds of showers and thunderstorms are forecast
through Thursday. Isolated heavy rain is still possible and may
again lead to localized flooding.

.SPOTTER INFORMATION STATEMENT...

Spotters might be needed this afternoon and early evening.

REV

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
129 PM CDT TUE MAY 26 2020

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0120 PM     TORNADO          4 W WAUKEE              41.62N 93.93W
05/26/2020                   DALLAS             IA   TRAINED SPOTTER

            BRIEF 10 SECOND TOUCHDOWN.

&&

AK

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
131 PM CDT TUE MAY 26 2020

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0126 PM     FUNNEL CLOUD     3 ESE DALLAS CENTER     41.66N 93.91W
05/26/2020                   DALLAS             IA   TRAINED SPOTTER

            FUNNEL CLOUD CLOSE TO GROUND, COULD NOT SEE
            THE SURFACE DUE TO BUILDINGS.

&&

AK

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
132 PM CDT TUE MAY 26 2020

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0128 PM     TORNADO          2 ESE DALLAS CENTER     41.67N 93.93W
05/26/2020                   DALLAS             IA   LAW ENFORCEMENT

            POLICE REPORT TORNADO ON GROUND.

&&

AK