Special Weather Statement, NWS Des Moines, IA

Area Forecast Discussion
National Weather Service Des Moines IA
645 PM CDT Tue Aug 1 2017

.SHORT TERM.../Tonight through Wednesday/
Issued at 353 PM CDT Tue Aug 1 2017

Quiet weather continues throughout the day today with a ridge of
high pressure still in place. Fairly warm this afternoon with
highs pushing into the mid to upper 80s across the state. A weak
boundary currently draped across central Minnesota will slide
south into the state this evening and tonight. Showers and
thunderstorms are possible along this line in central and northern
Iowa this evening and into tonight. Little to no shear across the
state and less than exciting CAPE values will prevent any severe
weather potential overnight tonight. As the boundary moves south,
winds will shift becoming more northerly allowing overnight
temperatures to sink into the upper 50s to lower 60s. Tomorrow a
mid-level shortwave drops into the midwest from Canada. During the
day, conditions will be warm and calm with highs again in the mid
to upper 80s despite northerly winds. Late afternoon and into the
next period a cold front associated with the mid-level low brings
with it another chance for showers and thunderstorms across the
state.

.LONG TERM.../Wednesday night through Tuesday/
Issued at 353 PM CDT Tue Aug 1 2017

The main forecast concern was focused on the system to impact the
state Thursday into Friday with winds, precip chances, and
temperatures. Leaned closer to the ECMWF/GFS for winds and
temperatures Thursday into Friday.

Wednesday Night into Friday...Upper level trough and associated
vort max pushes across the state overnight Wednesday night into
Thursday ahead of the deepening surface low over eastern South
Dakota. The trailing cold front looks to push through the CWA
during the day Thursday and much of the area will likely see early
maximum temperatures. Although not entirely confident to mention a
complete non-diurnal temp trend due to the time of year, but for
areas across the west and north, temperatures are likely to remain
fairly steady throughout the day Thursday. Decent PVA couplet and
tropopause fold, for this time of year, cut across the state
Thursday afternoon into the evening. Winds atop the mixed range
from 35 to 40 knots over central to northern Iowa during the
aforementioned time frame and thus confident to raise winds/gusts
3-6 knots across the forecast area Thursday into Friday. This
might even be too low across the north. The surface pressure
gradient finally begins to weaken towards the afternoon Friday
from west to east and thus at least Friday morning remains fairly
breezy. Lowered temperatures Thursday night and again on Friday
with the fair amount of CAA

Saturday into Monday...another upper level trough brings
additional rain chances on Sunday into Sunday night. Although
the latest ECMWF is much quicker in pushing this shortwave south
of the state Sunday. Still some questions on timing of
precipitation late in the weekend. Much cooler temperatures remain
across the CWA through next week.

&&

.AVIATION.../For the 00Z TAFS through 00Z Wednesday evening/
Issued at 645 PM CDT Tue Aug 1 2017

Mainly VFR conditions expected.  However, a cold front will settle
across central Iowa tonight and showers/storms will develop along
the boundary though will wane by 06Z due to loss of instability.
some potential for MVFR vsby late across northern TAF's due to some
low lying fog but confidence in this is low.  Still put a mention in
the TAF's at FOD, MCW and ALO for a couple hours.

&&

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

&&

SHORT TERM...Worley
LONG TERM...Podrazik
AVIATION...FAB

Hazardous Weather Outlook
National Weather Service Des Moines IA
523 AM CDT Tue Aug 1 2017

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-
081>086-092>097-021030-
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-
523 AM CDT Tue Aug 1 2017

This Hazardous Weather Outlook is for portions of central Iowa.

.DAY ONE...Today and tonight

Isolated non-severe thunderstorms are possible north and central this
afternoon and evening.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday

Isolated non-severe thunderstorms are possible Wednesday
afternoon over the far south. Scattered to widespread
thunderstorms are expected late Wednesday night into Thursday.
There is a very low threat of severe weather with these storms.
Additional thunderstorms are possible Saturday. The threat of
severe storms remains low at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not anticipated at this time.

REV

Special Weather Statement
National Weather Service Des Moines IA
647 PM CDT TUE AUG 1 2017

IAZ015-020015-
Palo Alto IA-
647 PM CDT TUE AUG 1 2017

...DIME TO NICKEL SIZE HAIL POSSIBLE ALONG WITH 40 TO 50 MPH
WIND GUSTS...

At 646 PM CDT, Doppler radar was tracking a strong thunderstorm near
Emmetsburg, moving southeast at 25 mph.

Nickel size hail and wind gusts up to 50 mph will be possible with
this storm.

Locations impacted include...
Emmetsburg, West Bend, Cylinder, Rodman and Emmetsburg Municipal
Airport.

LAT...LON 4298 9444 4291 9444 4291 9462 4309 9476
      4315 9456
TIME...MOT...LOC 2346Z 331DEG 23KT 4308 9461

Kotenberg

Special Weather Statement
National Weather Service Des Moines IA
712 PM CDT TUE AUG 1 2017

IAZ005-015-024-020045-
Humboldt IA-Palo Alto IA-Kossuth IA-
712 PM CDT TUE AUG 1 2017

...DIME TO NICKEL SIZE HAIL ALONG WITH 40 TO 50 MPH WIND GUSTS
POSSIBLE...

At 711 PM CDT, Doppler radar was tracking a strong thunderstorm 10
miles west of Algona, moving southeast at 25 mph.

Nickel size hail and wind gusts up to 50 mph will be possible with
this storm.

Locations impacted include...
West Bend, St. Joseph, Ottosen, Rodman and Stinson Prairie State
Park.

LAT...LON 4305 9454 4306 9429 4288 9409 4287 9442
TIME...MOT...LOC 0011Z 316DEG 22KT 4302 9442

Kotenberg

Special Weather Statement
National Weather Service Des Moines IA
716 PM CDT TUE AUG 1 2017

IAZ005>007-016-020045-
Kossuth IA-Winnebago IA-Worth IA-Hancock IA-
716 PM CDT TUE AUG 1 2017

...LINE OF STORMS MAY PRODUCE DIME TO NICKEL SIZE HAIL ALONG
WITH WIND GUSTS OT 40 TO 50 MPH...

At 715 PM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from 9 miles northwest of Forest City to 7 miles
north of Algona. Movement was southeast at 35 mph.

Nickel size hail and wind gusts up to 50 mph will be possible with
these storms.

Locations impacted include...
Forest City, Lake Mills, Britt, Eagle Lake, Rice Lake, Union Slogh,
Buffalo Center, Bancroft, Swea City, Burt, Thompson, Titonka, Wesley,
Fertile, Leland, Lakota, Crystal Lake, Woden, Rake and Joice.

LAT...LON 4326 9338 4326 9350 4320 9350 4299 9409
      4338 9444 4339 9444 4350 9393 4350 9359
TIME...MOT...LOC 0015Z 305DEG 30KT 4336 9377 4318 9425

Kotenberg

Special Weather Statement
National Weather Service Des Moines IA
745 PM CDT TUE AUG 1 2017

IAZ005>007-016-017-024-025-020130-
Humboldt IA-Wright IA-Cerro Gordo IA-Kossuth IA-Winnebago IA-
Worth IA-Hancock IA-
745 PM CDT TUE AUG 1 2017

...WIND GUSTS OF 40 TO 50 MPH ALONG WITH PENNY TO DIME SIZE
HAIL POSSIBLE...

At 745 PM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from 9 miles east of Algona to near Northwood.
Movement was southeast at 30 mph.

Dime size hail and wind gusts up to 50 mph will be possible with
these storms.

Locations impacted include...
Mason City, Forest City, Garner, Northwood, Lake Mills, Britt, Nora
Springs, Manly, Clear Lake, Eagle Lake, Mason City Municipal Airport,
Rice Lake, Ventura, Kanawha, Klemme, Wesley, Plymouth, Fertile,
Corwith and Leland.

LAT...LON 4315 9302 4277 9406 4310 9417 4350 9346
      4350 9302
TIME...MOT...LOC 0045Z 312DEG 26KT 4306 9404 4344 9317

Kotenberg

Special Weather Statement
National Weather Service Des Moines IA
822 PM CDT TUE AUG 1 2017

IAZ016-017-025-026-036-020200-
Hamilton IA-Wright IA-Cerro Gordo IA-Franklin IA-Hancock IA-
822 PM CDT TUE AUG 1 2017

...LINE OF STRONG STORMS MAY PRODUCE WINDS OF 40 TO 50 MPH
ALONG WITH PENNY TO DIME SIZE HAIL...

At 821 PM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from near Eagle Grove to near Mason City. Movement
was south at 35 mph.

Dime size hail and wind gusts up to 50 mph will be possible with
these storms.

Locations impacted include...
Mason City, Garner, Clarion, Eagle Grove, Belmond, Sheffield,
Rockwell, Clear Lake, Big Wall Lake, Mason City Municipal Airport,
Elm Lake, Ventura, Kanawha, Goldfield, Dows, Klemme, Latimer,
Thornton, Coulter and Meservey.

LAT...LON 4304 9302 4289 9302 4246 9393 4247 9393
      4247 9396 4282 9396 4320 9347 4323 9321
TIME...MOT...LOC 0121Z 340DEG 31KT 4271 9390 4318 9321

Kotenberg

Special Weather Statement
National Weather Service Des Moines IA
856 PM CDT TUE AUG 1 2017

IAZ017-025>027-036-037-020230-
Hamilton IA-Wright IA-Cerro Gordo IA-Hardin IA-Franklin IA-Butler IA-
856 PM CDT TUE AUG 1 2017

...LINE OF STRONG STORMS MAY PRODUCE WIND GUSTS TO 50 MPH ALONG WITH
SMALL HAIL...

At 855 PM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from 7 miles west of Marble Rock to near Webster
City. Movement was southeast at 25 mph.

Half inch hail and wind gusts up to 50 mph will be possible with
these storms.

Locations impacted include...
Webster City, Iowa Falls, Hampton, Jewell Junction, Sheffield, Big
Wall Lake, Alden, Dumont, Dows, Latimer, Stanhope, Williams, Coulter,
Blairsburg, Kamrar, Woolstock, Geneva, Bristow, Rowan and Bradford.

LAT...LON 4291 9303 4291 9295 4271 9282 4221 9390
      4242 9394 4247 9393 4247 9395 4256 9396
      4298 9303
TIME...MOT...LOC 0155Z 337DEG 20KT 4292 9301 4250 9389

Kotenberg