A low pressure system was slowly working its way into and through the Upper Plains, while high pressure lingered over the Ohio Valley. As a result, a tightening surface pressure gradient was seen across the western half of Iowa that resulted in widespread gusts into the 40 to 50 mph range.
Every event with a place to put it; 1 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.
A low pressure system was slowly working its way into and through the Upper Plains, while high pressure lingered over the Ohio Valley. As a result, a tightening surface pressure gradient was seen across the western half of Iowa that resulted in widespread gusts into the 40 to 50 mph range. A single site recorded a 50 knot gust and the same site nearly recorded sustained winds of 40 mph for an hour or more.
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 Feb 18, 5:36 AM CST, 5 hours 24 minutes earlier.
Area Forecast Discussion National Weather Service Des Moines IA 536 AM CST Sun Feb 18 2018 .SHORT TERM.../Today through Tonight/ Issued at 405 AM CST Sun Feb 18 2018 A low pressure area is developing from eastern Wyoming into central South Dakota, while broad high pressure moves away from our area over the Ohio River valley. As the low pressure trough approaches today our winds will turn south and increase, then tonight as broad forcing aloft and low-level moisture advection increase we will see development of light precipitation across much of the forecast area. Multiple potential hazards are present in the short term forecast period and will be outlined individually below. Early this morning areas of fog have developed across eastern and northeastern Iowa, due to nearly calm winds and clear skies associated with the aforementioned departing high pressure center. Thus far dense fog has remained just east of our forecast area, with a few stations from Waterloo over to Webster City reporting brief visibility below 1/4 SM before rebounding. However, in the next few hours is is likely that these dense fog observations may become a bit more numerous. Given their isolated and transitory nature, have handled this threat with a special weather statement rather than a very short dense fog advisory. Conditions should improve rapidly around sunrise as daytime warming begins and southerly winds increase. As the high moves away and the trough approaches from the northwest today we will see a significant tightening of the low-level pressure gradient. Forecast soundings at 18Z today show top of the mixed layer winds around 40 to 45 knots across most of the area, excepting the southeast, and all signs point toward windy conditions for a relatively brief period. The tightening of the pressure gradient will be more or less concurrent with enhanced daytime mixing, supporting strong winds by late morning. The winds should then decrease noticeably around mid to late afternoon as the trough approaches and the gradient begins to slacken. Have issued a targeted wind advisory from 9 am to 2 pm to account for this hazard. Finally, late tonight we will see development of light precipitation as the column gradually saturates from the surface upward and broad lift slowly increases ahead of the approaching system. Forecast soundings after 06Z tonight are unanimous in their depiction of a shallow saturated layer around 5-8 kft deep and entirely without ice crystal introduction. This will lead to a drizzle/rain scenario, with northwestern areas below freezing experiencing ice accumulations. The predicted freezing line placement has been pretty consistent over the last couple of days and confidence in the area of freezing rain/drizzle is high. Therefore, a winter weather advisory has been issued for our northwestern counties beginning at midnight tonight. Icing may not begin until more like 2 or 3 am, but once it does start impacts may be almost instantaneous, so prefer to play it safe with a slightly early start time at midnight. More freezing rain is expected from Monday into Tuesday as discussed in the long term section below, and additional headline considerations exist in that period as a result. .LONG TERM.../Monday through Saturday/ Issued at 405 AM CST Sun Feb 18 2018 Complex meteorological situation through Tuesday evening with broad southwest upper flow across the central United States. A surface front nearly parallel with this flow will move only gradually from Monday into Tuesday as ample moisture flows north into the boundary with large elevated warm layer above a shallow cold layer leading to extensive freezing precipitation over a good portions of central Iowa. Light precipitation will be ongoing Monday morning as surface wave passes through the state as moisture surges northward. The surface wave is forecast along a boundary which will stretch from near Bedford to Des Moines and Waterloo around daybreak. Will see freezing drizzle/light freezing rain northwest of the front with little ice introduction and a robust warm layer above the shallow polar air. There will be a very sharp temperatures gradient along the boundary with readings climbing from the mid 20s to mid 40 over a short distance and light rain is forecast near the front and to the south/east. A dry slow will arrive with the wave and will cut off precipitation from southwest to northeast during the day, except near the front where deeper forcing where deeper forcing on warm side of dry slot will allow precipitation to linger in the southeast. A second shortwave will begin to influence the weather by Monday night with renewed warm advection/moisture transport north of the boundary into central Iowa. This event likely shaping up to be the more problematic of the two as heavier QPF is expected in areas behind the front. Impressive broad expanse of isentropic lift will be in place across much of the upper Midwest during this time, supporting widespread precipitation. Unfortunately for the forecast area, thermal profiles indicate a broad area of freezing rain from southwest through central into northeast Iowa Monday night into Tuesday with ice accumulations that could be upwards of a few tenths of an inch possibly approaching or exceeding ice warning criteria, therefore a Winter Storm Watch has been issued for these areas. Meanwhile, in the far southeast CWA, temperatures will remain relatively warm with rain and even thunder during this time. Rainfall amounts of an inch to inch and half are certainly not out of the question given the moisture transport into the state and this may lead to some decent rises on streams over the southeast. The system will finally drop southeast of the state on Tuesday night with large Canadian high pressure approaching. However, both GFS and Euro indicate that the western trof will remain in place through the week with various waves traversing through the base of the mean trof an into the central United States. Therefore, there will continue to be additional threats of precipitation through the week with timing and placement problematic as GFS and Euro disagree with the specifics of the individual shortwaves. && .AVIATION.../For the 12Z TAFS through 12Z Monday morning/ Issued at 536 AM CST Sun Feb 18 2018 A fog bank affecting much of northeast Iowa will produce intermittent IFR or lower conditions at ALO and MCW in the next couple of hours before moving away. Winds will turn to south and increase substantially by late morning, resulting in crosswinds of 20 KT or greater on some east-west runways into the afternoon before diminishing. Late tonight, between 06Z and 12Z, conditions will deteriorate as very low clouds and drizzle/light rain develop across the area. This will lead to IFR or lower conditions from near the end of the current TAF period well into Monday. && .DMX WATCHES/WARNINGS/ADVISORIES... Wind Advisory from 9 AM this morning to 2 PM CST this afternoon for IAZ004>007-015>017-023>028-033>039-044>049-057>061-070>073- 081>083-092>094. Winter Storm Watch from Monday evening through Tuesday morning for IAZ027-028-037>039-048>050-059>062-072>074-082>084-093-094. Winter Weather Advisory from midnight tonight to 3 PM CST Monday for IAZ004>007-015>017-023>026-033>036-044>047-057-058. && SHORT TERM...Lee LONG TERM...Cogil AVIATION...Lee
Hazardous Weather Outlook National Weather Service Des Moines IA 359 AM CST Sun Feb 18 2018 IAZ004>007-015>017-023>026-033>036-044>047-057-058-191200- Emmet-Kossuth-Winnebago-Worth-Palo Alto-Hancock-Cerro Gordo- Pocahontas-Humboldt-Wright-Franklin-Sac-Calhoun-Webster-Hamilton- Crawford-Carroll-Greene-Boone-Audubon-Guthrie- 359 AM CST Sun Feb 18 2018 This Hazardous Weather Outlook is for portions of central Iowa. .DAY ONE...Today and tonight Strong south winds are expected late this morning into the early afternoon. A Wind Advisory is in effect for the area today. Please refer to the National Weather Service website at weather.gov/desmoines for further details. Freezing drizzle and light freezing rain are expected by late tonight. A Winter Weather Advisory is in effect for the area late tonight. Please refer to the National Weather Service website at weather.gov/desmoines for further details. .DAYS TWO THROUGH SEVEN...Monday through Saturday Additional freezing drizzle and light freezing rain are expected on Monday. A Winter Weather Advisory is in effect for the area through mid afternoon Monday. Please refer to the National Weather Service website at weather.gov/desmoines for further details. .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed, however icing reports would be appreciated. IAZ070-071-081-092-191200- Cass-Adair-Adams-Taylor- 359 AM CST Sun Feb 18 2018 This Hazardous Weather Outlook is for portions of central Iowa. .DAY ONE...Today and tonight Strong south winds are expected late this morning into the early afternoon today. A Wind Advisory is in effect for the area today. Please refer to the National Weather Service website at weather.gov/desmoines for further details. .DAYS TWO THROUGH SEVEN...Monday through Saturday Light freezing rain and freezing drizzle will likely impact the area Monday night into Tuesday with light to moderate ice accumulations possible. .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed, however icing reports would be appreciated. IAZ027-028-037>039-048-049-059>061-072-073-082-083-093-094-191200- Butler-Bremer-Hardin-Grundy-Black Hawk-Story-Marshall-Dallas-Polk- Jasper-Madison-Warren-Union-Clarke-Ringgold-Decatur- 359 AM CST Sun Feb 18 2018 This Hazardous Weather Outlook is for portions of central Iowa. .DAY ONE...Today and tonight Strong south winds are expected late this morning into the early afternoon. A Wind Advisory is in effect for the area today. Please refer to the National Weather Service website at weather.gov/desmoines for further details. .DAYS TWO THROUGH SEVEN...Monday through Saturday A few non severe thunderstorms will be possible on Monday into Monday evening, especially south of Interstate 80. Freezing rain and freezing drizzle will likely impact the area Monday night into Tuesday with significant icing. A Winter Storm Watch is in effect for the area Monday night into Tuesday. Please refer to the National Weather Service website at weather.gov/desmoines for further details. .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed, however icing reports would be appreciated. IAZ050-062-074-084-191200- Tama-Poweshiek-Marion-Lucas- 359 AM CST Sun Feb 18 2018 This Hazardous Weather Outlook is for portions of central Iowa. .DAY ONE...Today and tonight Strong south winds are expected today at 20 to 25 mph with gusts to 40 mph. .DAYS TWO THROUGH SEVEN...Monday through Saturday A few isolated non severe thunderstorms will be possible on Monday. Freezing rain and freezing drizzle is expected to impact the area Monday night into Tuesday with significant icing. A Winter Storm Watch is in effect for the area Monday night into Tuesday. Please refer to the National Weather Service website at weather.gov/desmoines for further details. .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed, however icing reports would be appreciated. IAZ075-085-086-095>097-191200- Mahaska-Monroe-Wapello-Wayne-Appanoose-Davis- 359 AM CST Sun Feb 18 2018 This Hazardous Weather Outlook is for portions of central Iowa. .DAY ONE...Today and tonight Southerly winds of 20 to 25 mph, with gusts to 40 mph are expected today. .DAYS TWO THROUGH SEVEN...Monday through Saturday A few isolated non severe thunderstorms will be possible on Monday into early Tuesday. In addition, heavy rainfall will be possible with an inch to an inch and a half possible by Tuesday evening. .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed.
The national radar mosaic for the moment the first event began.
1 high wind. Local standard time, as filed.
AWOS recorded a 58 mph or 50 knot wind gust, as well as sustained winds around 40 mph.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2018Every state in 2018This day in weather historyWarnings in Iowa, February 2018
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: 740127.