A few storms occurred through the early morning hours on the 15th with one storm producing some wind damage to a farmstead in eastern Crawford County.
Every event with a place to put it. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS DMX wrote it up.
A few storms occurred through the early morning hours on the 15th with one storm producing some wind damage to a farmstead in eastern Crawford County.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Des Moines, IA wrote its last area forecast discussion before the first event at Sep 15, 2:54 AM CST, 2 hours 41 minutes earlier.
Area Forecast Discussion National Weather Service Des Moines IA 354 AM CDT Fri Sep 15 2017 .SHORT TERM.../Today through Tonight/ Issued at 354 AM CDT Fri Sep 15 2017 A couple forecast challenges in the short term: 1)showers this morning; 2)high temperature trends today; 3)Thunderstorm potential tonight. Today...Forecast Confidence: Medium 00Z upper air analysis and water vapor imagery indicated weak upper ridging across the central CONUS with a series upstream troughs over the western states. At the sfc...MSAS analysis indicated a broad area of low pressure extending from eastern CO northward thru NE and into southern MN. Nocturnal LLJ has developed once again overnight with 09z radar mosaic showing a recent emergence of showers/tstms over far western IA. First concern this morning is the area of scattered showers/tstms over western Iowa. This activity is being driven by isentropic ascent and moisture convergence along a plume of higher low/mid level moisture. Expect this activity to gradually spread north and east thru the morning hours until the LLJ begins to wane. Any precip should remain very light...generally a tenth of an inch or less. In the wake of this morning activity a lull in precip should occur as forcing diminishes and a stout cap develops as H7 temps rise to near +10C. With breezy south/southeast winds and 850mb temps in the low 20s Celsius, high temperatures should again rise into the upper 80s to lower 90s. Like yesterday...a few CAM solutions do show an isolated shower/tstm developing in the late afternoon during peak heating, but coverage should be very minimal. Tonight...Forecast Confidence: Medium A stronger upper shortwave is expected to pivot northward across NE/SD during the evening hours. Upper forcing associated with this feature and convergence along a developing cold front should lead to scattered thunderstorm development initially over the NE/SD/MN tri- state area. A broken line of storms should then slide east/southeastward into northwest IA around 03Z. Severe parameters are not overly favorable...but modest deep layer shear /20-30kts/ and MUCAPE values near 1000 J/kg could yield a few strong to severe storms /mainly gusty winds/ per the SPC Marginal outlook. Its still unclear how far south these storms will progress by 12Z Saturday...with a number of models showing them reaching southwest/south-central IA while others keep a majority of the activity across northern IA. Will keep the highest chance for pcpn in northwest sections of the forecast area...with a slight chance in the Des Moines metro area. With the thicker cloud cover and a persistent southerly breeze expecting mild overnight lows in the 60s. .LONG TERM.../Saturday through Thursday/ Issued at 354 AM CDT Fri Sep 15 2017 Large upper low currently spinning over NE Utah will continue to push east northeast slowly into the weekend, with the associated elongated surface trough slowly marching eastward across the central US and to be oriented from NE MN southwestward through western IA and into central KS by early Saturday. May see have some ongoing showers/storms across the west/northwest early in the period, with that activity likely diminishing through the morning hours as the LLJ dissipates and focus switches to strong cold front expected to push into western IA by Saturday evening. Main upper trough and associated energy rounding the base of the rough to push into the Dakotas by early Saturday evening, with storms expected to fire in vicinity of the front during the late afternoon/early evening hours. As the front continues to push east southeast through the state, expect line of storms to progress across the forecast area as well. Instability still looking ok for possible strong to severe storms, but overall shear still somewhat marginal. Decent instability with better shear still just behind the front which NAM trying to show more post-frontal storms moving through, so still will have a severe threat with any development just behind the front as well. Temperatures to also take a dive behind the front, with the NAM soundings showing a close to 10 degree Celsius drop with H85 temps falling to around +11C for Sunday. Front to stall out across southern IA/northern MO with continued chances for storms into Sunday. Broad upper level troughing to continue across the western US with energy ejecting through the region with a southwest upper level flow pattern expected through much of next week. Shortwave energy to lift through the region Monday with the stalled cold front now expected to lift back northward Monday as a warm front with another chance for some showers/storms across much of the area. Another large trough to dig into the intermountain west toward the middle to end of next week. A series of energy will move through the trough, with one lobe lifting into central Canada toward Wed/Thu while the other lobe digs into the Pacific NW. A cold front and sfc low associated with the first wave will move through the state late next week bringing another chance for precipitation to the state. As the upper level trough across the western US continues to deepen into the end of next week/weekend an active pattern looks to continue across the region. After temperatures cool for Sunday into Monday a general warming trend is expected into Tuesday and Wednesday with another slight cool down behind the mid-week cold front for Thursday into Friday. Temperatures through the entire period will stay near or above the seasonal averages for mid September. && .AVIATION.../For the 06Z TAFS through 06Z Friday night/ Issued at 1202 AM CDT Fri Sep 15 2017 The primary concerns have not changed much since 00z. The maturing low level jet will continue to produce LLWS near KFOD/KMCW through sunrise and then likely again around KMCW this evening. Isolated high based convection has exited the forecast area, and could develop again early this morning, but confidence is not great enough to include at the moment. Better chances return north and west beyond the valid period. Thus the forecast remains VFR until trends dictate otherwise. && .DMX WATCHES/WARNINGS/ADVISORIES...NONE. && SHORT TERM...Fowle LONG TERM...Beerends AVIATION...Small
Hazardous Weather Outlook National Weather Service Des Moines IA 350 AM CDT Fri Sep 15 2017 IAZ004>007-015>017-023>025-033>036-044>047-057>059-070-071-161000- Emmet-Kossuth-Winnebago-Worth-Palo Alto-Hancock-Cerro Gordo- Pocahontas-Humboldt-Wright-Sac-Calhoun-Webster-Hamilton-Crawford- Carroll-Greene-Boone-Audubon-Guthrie-Dallas-Cass-Adair- 350 AM CDT Fri Sep 15 2017 This Hazardous Weather Outlook is for portions of central Iowa. .DAY ONE...Today and tonight There is a chance for thunderstorms mainly late tonight. An isolated strong to severe storm will be possible late tonight. .DAYS TWO THROUGH SEVEN...Saturday through Thursday Periodic thunderstorm chances are forecast Saturday through Thursday. There is a slight risk for severe storms across the area Saturday, with the strongest storms expected in the evening hours. Predictability is too low for severe weather potential Sunday into Thursday. Breezy south to southwest winds and low relative humidity may lead to fire weather concerns this afternoon into the early evening. .SPOTTER INFORMATION STATEMENT... Spotter activation may be needed Saturday night. IAZ026>028-037>039-048>050-060>062-072>075-081>086-092>097-161000- Franklin-Butler-Bremer-Hardin-Grundy-Black Hawk-Story-Marshall- Tama-Polk-Jasper-Poweshiek-Madison-Warren-Marion-Mahaska-Adams- Union-Clarke-Lucas-Monroe-Wapello-Taylor-Ringgold-Decatur-Wayne- Appanoose-Davis- 350 AM CDT Fri Sep 15 2017 This Hazardous Weather Outlook is for portions of central Iowa. .DAY ONE...Today and tonight There is a chance for a non-severe thunderstorm tonight mainly west of Interstate 35. .DAYS TWO THROUGH SEVEN...Saturday through Thursday Periodic thunderstorm chances are forecast Saturday through Thursday. An isolated strong to severe storm is possible Saturday night mainly west of I-35. Predictability is too low for severe weather potential Sunday into Thursday. Breezy south to southwest winds and low relative humidity may lead to fire weather concerns this afternoon into the early evening. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time. MJB
Special Weather Statement
National Weather Service Des Moines IA
502 AM CDT FRI SEP 15 2017
IAZ057-058-151100-
Guthrie IA-Audubon IA-
502 AM CDT FRI SEP 15 2017
...Isolated Strong Storm over Audubon County...
At 501 AM CDT, Doppler radar was tracking a strong thunderstorm 9
miles southwest of Audubon, moving northeast at 15 mph.
Dime size hail and winds in excess of 30 mph will be possible with
this storm.
Locations impacted include...
Audubon, Exira, Adair, Elk Horn, Kimballton, Brayton and Audubon
County Airport.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.
&&
LAT...LON 4179 9509 4186 9482 4186 9463 4150 9461
4151 9504 4160 9504 4160 9509
TIME...MOT...LOC 1001Z 242DEG 12KT 4165 9510
MFSpecial Weather Statement National Weather Service Des Moines IA 616 AM CDT FRI SEP 15 2017 IAZ044-151215- Crawford IA- 616 AM CDT FRI SEP 15 2017 ...SPECIAL WEATHER STATEMENT... At 616 AM CDT, Doppler radar was tracking a strong thunderstorm near Denison, moving northeast at 25 mph. Half inch hail will be possible with this storm. Locations impacted include... Denison, Manilla, Dow City, Vail, Westside, Deloit, Arion, Buck Grove, Aspinwall and Denison Municipal Airport. LAT...LON 4220 9509 4186 9509 4186 9546 4203 9553 TIME...MOT...LOC 1116Z 241DEG 20KT 4195 9536 Martin
The Des Moines radar (KDMX), 122 km away, was scanning. The volume nearest the first event began at 11:35 UTC.
1 thunderstorm wind. Local standard time, as filed.
Damage was done to outbuildings and trees on the farmstead.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2017Every state in 2017This day in weather historyWarnings in Iowa, September 2017
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 722001.