Flash Flood Warning 19, NWS Des Moines, IA

069 
WGUS73 KDMX 050322
FFSDMX

Flash Flood Statement
National Weather Service Des Moines IA
1022 PM CDT Thu Jul 4 2019

IAC091-109-147-151-050332-
/O.CAN.KDMX.FF.W.0019.000000T0000Z-190705T0545Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Pocahontas IA-Kossuth IA-Humboldt IA-Palo Alto IA-
1022 PM CDT Thu Jul 4 2019

...THE FLASH FLOOD WARNING FOR NORTHEASTERN POCAHONTAS...SOUTHERN
KOSSUTH...NORTHERN HUMBOLDT AND SOUTHEASTERN PALO ALTO COUNTIES IS
CANCELLED...

Flood waters have receded. Flooding is no longer expected to pose a 
threat. Please continue to heed any remaining road closures and be 
aware of roads that may have been damaged from flooding.

LAT...LON 4315 9397 4269 9397 4291 9471 4318 9454

$$

Krull

Area Forecast Discussion
National Weather Service Des Moines IA
319 PM CDT Thu Jul 4 2019

.DISCUSSION.../Tonight through Thursday/
Issued at 319 PM CDT Thu Jul 4 2019

The summer doldrums continue, with persistent generally low-end
rain/thunderstorm chances for the next several days, consistent
with thinking on previous shifts. From tonight through Saturday
night Iowa will continue to reside beneath weak, roughly zonal
flow aloft, through which a series of subtle shortwave impulses
will move. In the lower levels this will translate to similarly
light and somewhat variable flow, with multiple synoptic and
outflow boundaries wobbling around the region, providing foci for
convective development at times but with no substantial
temperature gradients or wind shifts given the low wind speeds
expected. This scenario will result in a continuation of periodic
isolated to scattered thunderstorm development with little
predictability in terms of precise timing or location, thus the
persistence of slight chance/chance POPs in the forecast.

Currently one of the aforementioned weak boundaries resides across
far north/northwest Iowa and short-term model guidance supports
convective development within that area this evening. However,
there is little to no shear or organized forcing mechanism, so the
threat of severe weather is low and any storms that do form should
dissipate early tonight, after sunset, as they will largely be
diurnally driven. Elsewhere in our forecast area, any storms this
evening will be very isolated. We should then see a relative lull
overnight, from midnight into Friday morning, with again any
storms being very isolated. Meanwhile a mid-level impulse moving
off the Rockies this evening will generate one or more large MCSs
over the high plains of western Nebraska and South Dakota tonight,
which will then progress eastward across those states overnight.
As they approach Iowa from the west on Friday morning they should
gradually weaken, and there is considerable uncertainty as to
whether they will impact our forecast area or pass by to the north
and/or south, and what intensity they would have by the time they
get this far, if they do impact us. In addition, even aside from
this/these MCS/s, the shortwave that initially produced them will
also move overhead sometime late Friday and, while it will have
dampened noticeably by that time, may generate more convection
tomorrow afternoon/evening. While the overall environment is still
not terribly supportive of severe weather, with a bit better lift
and instability and with the possibility of impact by the
morning/midday MCS/s, SPC is advertising a broad marginal severe
weather risk for Friday and this certainly seems justified.

Friday night into Saturday may continue to see additional showers
and storms, depending on the timing of the forcing impulse which
is faster in the NAM but slower in the EC/GFS. Regardless, by
Saturday things should start to clear out a bit and any severe
weather threat will be even lower, and by the end of the day we
will finally start to see a subtle pattern change in wake of the
earlier shortwave trough. This will manifest as a subtle building
of weak ridging aloft, and at the surface most of the nebulous
boundaries pushing through and bringing light north/northwest flow
to most of Iowa and making for slightly, and I do mean slightly,
cooler and drier weather from Sunday into Monday.

In the extended, a mid-level thermal ridge will cross Iowa around
Monday night and bring at least a brief return of somewhat warmer
weather, though not nearly to the levels we saw last weekend.
Immediately behind the axis of the mid-level ridge, the trough
pushing it eastward will bring a return of more substantial
thunderstorm chances sometime between Monday night and early
Wednesday, though the details are muddled at this point, and then
in wake of this trough probably another relatively dry and quiet
period, though it is unknown how long that will last in the latter
half of next week.

&&

.AVIATION.../For the 18Z TAFS through 18Z Friday afternoon/
Issued at 1240 PM CDT Thu Jul 4 2019

VFR conditions will prevail through the TAF period, with a couple
of marginal exceptions. First, a field of low cumulus clouds
currently developing per satellite imagery may produce brief MVFR
ceilings in the next couple of hours, mainly at DSM/OTM, before
base heights rise above 3000 ft AGL. Second, isolated to scattered
thunderstorms are expected to redevelop late this afternoon into
early tonight. Probability of effects at a given terminal are low,
but highest at FOD/MCW where a TEMPO group for VCTS is maintained.
Amendments may be necessary if SHRA/TSRA is approaching a
particular terminal later today/tonight.

&&

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

&&

DISCUSSION...Lee
AVIATION...Lee

Hazardous Weather Outlook
National Weather Service Des Moines IA
337 PM CDT Thu Jul 4 2019

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-
081>086-092>097-051100-
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-
337 PM CDT Thu Jul 4 2019

This Hazardous Weather Outlook is for portions of central Iowa.

.DAY ONE...This afternoon and tonight

Widely scattered thunderstorms will redevelop late this afternoon
into tonight, mainly in northern and northwestern Iowa where a few
storms could produce strong wind gusts and locally heavy rain.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday

Thunderstorm chances will persist intermittently at least through
Saturday and perhaps into Sunday. Isolated severe storms and
locally heavy rain will remain possible at times. Additional
thunderstorms will return between Monday night and Wednesday. The
severe weather threat for next week will be evaluated in more
detail in later outlooks.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is possible at times through the week, but
generally unlikely.

Lee