Acute short term dryness continued to lead to worsening drought conditions over portions of central Iowa during August 2017.
Every event with a place to put it; 15 filed by county or forecast zone are drawn at its center, in a lighter ring. 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.
Acute short term dryness continued to lead to worsening drought conditions over portions of central Iowa during August 2017.
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 Jul 31, 9:54 PM CST, 2 hours 6 minutes earlier.
Area Forecast Discussion National Weather Service Des Moines IA 1054 PM CDT Mon Jul 31 2017 ...Updated for 06z Aviation Discussion... .SHORT TERM.../Tonight through Tuesday/ Issued at 326 PM CDT Mon Jul 31 2017 Surface high pressure will continue to provide dry and quiet weather tonight into Tuesday. Another decent night of radiational cooling to set up across the forecast area and leaned toward going slightly cooler for minimum temperatures. Leaned toward the MET MOS guidance for lows tonight. Weak shortwave embedded within the 500mb flow looks to enter the state by late Tuesday afternoon providing enough forcing for thunderstorm potential across far northern Iowa. .LONG TERM.../Tuesday night through Monday/ Issued at 326 PM CDT Mon Jul 31 2017 There is little change to the going forecast overall but I did attempt to better define precip timing Tuesday night through Thursday. Beginning Tuesday evening, a weak cold front will sag into northern Iowa then fall apart as it stalls or slowly inches across the rest of the state. The GFS is way too bullish on PoPs during this time given the lack of instability, moisture and forcing. I did leave low end slight chance PoP's in areas where forcing appeared better but have little confidence we'll see more than a sprinkle. As suggested yesterday, the models continue with weak short wave ridging ahead of a more potent wave late Wednesday night and Thursday. We will be in between the parting Tuesday wave to the east and the incoming wave to the northwest. As a result, I left slight chances far southeast and northwest with low confidence we'll see anything. Just can't rule precip out entirely because instability does increase in these areas with daytime heating even though shear is weak. Wednesday evening a surface low develops in response to the aforementioned short wave moving in. A cold front associated with the surface low will shift across the state slowly from mid to late Wednesday evening through Thursday. At this point in time it appears that the front will enter the forecast area towards midnight and push across all but eastern Iowa by 18Z Thursday. There is still some question as to the coverage and intensity of showers/storms based on model discrepancy regarding where exactly the surface low will track and how much instability and shear there will be. The GFS has been consistent with moving the low into northern Iowa while the Euro and the NAM put the surface low in MN and the Canadian doesn't even hint at a surface low in the area, which is the odd model out. All models only have weak to modest instability for Wednesday night and while the shear does improve late Wednesday night, even the GFS puts the better shear in MN and dribbles pockets of better shear along the front. Bottom line is that there should be areas of precip...not as widespread as I thought yesterday, and some showers with isolated storms. At this point the severe potential looks better over south Dakota and Nebraska but even at that it would be a marginal threat for wind and hail. Northern Iowa into MN may continue that marginal threat in the areas of better shear but overall confidence for anything robust at this point is low. Going forward, the upper trough deepens as it passes east Thursday which may linger east into Thursday. We remain in northwest flow Friday keeping temps rather cool. On Saturday another shortwave will drop down the northwest flow as a ridge builds over the Rockies spreading precip chances from west to east through the day. The combination of deep northwest flow, cloud cover and rain on Saturday will keep temps on the cool side again. Models are now suggesting deepening the shortwave on Saturday over Iowa which then slows the progression of the trough and keeps precip chances going through Sunday. Finally dry conditions Sunday into next week but northwest flow will remain and as a result temps will only show a modest bump on Monday. Even though there appear to be several chances for precip, the precip will be light keeping drought concerns going across southern Iowa and there does not appear to be any large chances for severe storms. && .AVIATION.../For the 06Z TAFS through 06Z Tuesday night/ Issued at 1054 PM CDT Mon Jul 31 2017 As has been the challenge the last two TAF issuances is the concern for patchy fog development. The most consistent area for patchy fog has been over the northeastern terminals and have continued to show MVFR visibility restrictions. Outside of any fog that impacts those terminals, VFR conditions should prevail through the TAF period. A cold front approaching from the north may bring a few isolated showers or thunderstorms towards the northern TAF sites late tomorrow, but confidence not high that it will impact a terminal at this time. && .DMX WATCHES/WARNINGS/ADVISORIES... NONE. && SHORT TERM...Podrazik LONG TERM...FAB AVIATION...Ansorge
Hazardous Weather Outlook National Weather Service Des Moines IA 334 PM CDT Mon Jul 31 2017 IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075- 081>086-092>097-012045- 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- 334 PM CDT Mon Jul 31 2017 This Hazardous Weather Outlook is for portions of central Iowa. .DAY ONE...This afternoon and tonight No hazardous weather is expected at this time. .DAYS TWO THROUGH SEVEN...Tuesday through Sunday Isolated non-severe thunderstorms are forecast between Tuesday evening and Wednesday evening. More scattered to widespread thunderstorms are expected late Wednesday night into Thursday and there is a very low probability of severe weather with these storms. Additional thunderstorm chances come over the weekend with a low severe threat. .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed. FAB
The national radar mosaic for the moment the first event began.
15 drought. Local standard time, as filed.
Dryness led to severe drought conditions for a couple of weeks across much of Pocahontas county.
Lack of precipitation led to severe drought conditions across portions of Calhoun county in the middle of August.
Extreme drought conditions developed in far southern Madison county in August with large rainfall deficits.
Extreme drought conditions developed in far southern Warren county due to acute short term dryness.
Severe drought conditions developed in Marion county due to acute short term dryness.
Severe drought conditions developed in southern Mahaska county due to acute short term dryness.
Severe to Extreme drought conditions developed in much of Union county due to acute short term dryness.
Extreme drought conditions developed across Clarke county due to acute short term dryness.
Extreme drought conditions developed in much of Lucas county due to acute short term dryness.
Severe drought conditions developed across Monroe county due to acute short term dryness.
Severe to extreme drought conditions developed across Wapello county due to acute short term dryness.
Severe drought conditions developed in far northeast Ringgold county due to acute short term dryness.
Severe to extreme drought conditions developed across central and northern Decatur county due to acute short term dryness.
Severe drought conditions developed in much of Appanoose county due to acute short term dryness.
Severe drought conditions developed in much of Davis county due to acute short term dryness.
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, August 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: 765996, 765997, 766000, 766001, 766002, 766003, 766005, 766006, 766007, 766008, 766009, 766010, 766011, 766012, 766013.