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National Weather ServiceNational Weather ServiceDes Moines, IADes Moines, IA


Iowa Weather & Flood OutlookIowa Weather & Flood OutlookIowa Weather & Flood OutlookIowa Weather & Flood Outlook

February 10, 2010February 10, 2010

Jeff Johnson & Jeff ZoggJeff Johnson & Jeff Zogg


TopicsTopicsTopicsTopics

• Outlook at-a-glanceOutlook at-a-glance• DefinitionsDefinitions• Current conditionsCurrent conditions• Latest spring food outlookLatest spring food outlook• QuestionsQuestions


Where We Stand Where We Stand Where We Stand Where We Stand


Current Weather Situation Current Weather Situation Current Weather Situation Current Weather Situation


Weather Map 6 AM Thursday, February 11th Weather Map 6 AM Thursday, February 11th Weather Map 6 AM Thursday, February 11th Weather Map 6 AM Thursday, February 11th


Weather Map 6 AM Friday, February 12th Weather Map 6 AM Friday, February 12th Weather Map 6 AM Friday, February 12th Weather Map 6 AM Friday, February 12th


Weather Map 6 AM Saturday, February 13th Weather Map 6 AM Saturday, February 13th Weather Map 6 AM Saturday, February 13th Weather Map 6 AM Saturday, February 13th


Weather Map 6 AM Sunday, February 14th Weather Map 6 AM Sunday, February 14th Weather Map 6 AM Sunday, February 14th Weather Map 6 AM Sunday, February 14th


Precipitation forecast for the weekend Precipitation forecast for the weekend Precipitation forecast for the weekend Precipitation forecast for the weekend


The Seven Day Forecast for Des MoinesThe Seven Day Forecast for Des MoinesThe Seven Day Forecast for Des MoinesThe Seven Day Forecast for Des Moines


How About Days 8-14?How About Days 8-14?How About Days 8-14?How About Days 8-14?


Upcoming Events! Upcoming Events! Upcoming Events! Upcoming Events!

Spotter Training Starts Next Week Spotter Training Starts Next Week Schedule at: Schedule at:

www.weather.gov/desmoines/?n=spotterinfo www.weather.gov/desmoines/?n=spotterinfo

Spotter Training Starts Next Week Spotter Training Starts Next Week Schedule at: Schedule at:

www.weather.gov/desmoines/?n=spotterinfo www.weather.gov/desmoines/?n=spotterinfo

Severe Weather Awareness Week Severe Weather Awareness Week April 5-9 April 5-9

Test tornado drill Test tornado drill Wednesday, April 8Wednesday, April 8thth at 10:00 AM at 10:00 AM

Severe Weather Awareness Week Severe Weather Awareness Week April 5-9 April 5-9

Test tornado drill Test tornado drill Wednesday, April 8Wednesday, April 8thth at 10:00 AM at 10:00 AM


Outlook at-a-glanceOutlook at-a-glanceOutlook at-a-glanceOutlook at-a-glance

• High risk of significant floodingHigh risk of significant flooding in northwest Iowa. in northwest Iowa.– Also concerned about flooding in southeast Iowa—Mississippi Also concerned about flooding in southeast Iowa—Mississippi

River and its tributaries.River and its tributaries.– At least near to above normal risk of flooding statewide.At least near to above normal risk of flooding statewide.

• Above normal risk of Above normal risk of flooding from ice jams.flooding from ice jams.• Higher than normal risk of flooding also in areas that Higher than normal risk of flooding also in areas that

have have little to no snow cover.little to no snow cover.• The flooding potential will be more sensitive than The flooding potential will be more sensitive than

normalnormal to the occurrence and timing of weather events to the occurrence and timing of weather events such as rapid warm ups and heavy precipitation.such as rapid warm ups and heavy precipitation.



DefinitionsDefinitionsDefinitionsDefinitions



• Stage / Gage heightStage / Gage height– The level of the water surface of a stream above an The level of the water surface of a stream above an

established datum at a given location. The established datum established datum at a given location. The established datum may be a local elevation or sea level.may be a local elevation or sea level.

• ReachReach– A section of stream between an upstream and downstream A section of stream between an upstream and downstream

location, for which the stage or flow measured at a point location, for which the stage or flow measured at a point somewhere along the section (e.g., gaging station or forecast somewhere along the section (e.g., gaging station or forecast point) is representative of conditions in that section of river point) is representative of conditions in that section of river or stream.or stream.



• Bankfull stageBankfull stage– An established gage height at a given location, above which a An established gage height at a given location, above which a

rise in water surface will cause the river or stream to rise in water surface will cause the river or stream to overflow the river bank somewhere in the corresponding overflow the river bank somewhere in the corresponding reach.reach.

• Flood stageFlood stage– An established gage height for a given location at which a rise An established gage height for a given location at which a rise

in water surface level begins to create a hazard to lives, in water surface level begins to create a hazard to lives, property or commerce. The issuance of flood (or in some property or commerce. The issuance of flood (or in some cases flash flood) warnings is linked to flood stage. Not cases flash flood) warnings is linked to flood stage. Not necessarily the same as bankfull stage.necessarily the same as bankfull stage.



• Minor floodingMinor flooding– Minimal or no property damage, but possibly some public Minimal or no property damage, but possibly some public

threat.threat.• Moderate floodingModerate flooding

– Some inundation of structures and roads near stream. Some Some inundation of structures and roads near stream. Some evacuations of people and/or transfer of property to higher evacuations of people and/or transfer of property to higher elevations.elevations.

• Major floodingMajor flooding– Extensive inundation of structures and roads. Significant Extensive inundation of structures and roads. Significant

evacuations of people and/or transfer of property to higher evacuations of people and/or transfer of property to higher elevations.elevations.



• Record floodingRecord flooding– Flooding which equals or exceeds the Flooding which equals or exceeds the

highest stage or discharge observed at highest stage or discharge observed at a given site during the period of record a given site during the period of record keeping. The highest stage on record is keeping. The highest stage on record is not necessarily above the other three not necessarily above the other three flood categories – it may be within any flood categories – it may be within any of them or even less than the lowest.of them or even less than the lowest.

Stage – flood category Stage – flood category relationshiprelationship



Current conditionsCurrent conditionsCurrent conditionsCurrent conditions


Winter average temperaturesWinter average temperaturesWinter average temperaturesWinter average temperatures


Winter precipitationWinter precipitationWinter precipitationWinter precipitation


Winter snowfallWinter snowfallWinter snowfallWinter snowfall


Snow pack—nowSnow pack—nowSnow pack—nowSnow pack—now

Snow depth—Snow depth—2/9/20102/9/2010



Snow depth vs. normal—Snow depth vs. normal—2/9/20102/9/2010



Snow water equivalent—Snow water equivalent—2/9/20102/9/2010


Snow pack—historicalSnow pack—historicalSnow pack—historicalSnow pack—historical



Snow pack—now (repeat)Snow pack—now (repeat)Snow pack—now (repeat)Snow pack—now (repeat)



Stream levels—nowStream levels—nowStream levels—nowStream levels—now

14-day average flow—14-day average flow—as of 2/8/2010as of 2/8/2010


Stream levels—historicalStream levels—historicalStream levels—historicalStream levels—historical



Stream levels—now (repeat)Stream levels—now (repeat)Stream levels—now (repeat)Stream levels—now (repeat)



Ground frostGround frostGround frostGround frost

Frost depth—Frost depth—2/9/20102/9/2010


Soil moisture—nowSoil moisture—nowSoil moisture—nowSoil moisture—now

Percentile keyPercentile key

~1: near record low~1: near record low<10: much below normal<10: much below normal10 -24: below normal10 -24: below normal

25-75: normal25-75: normal

76-90: above normal76-90: above normal>90: much above normal>90: much above normal~99: near record high~99: near record high

Soil moisture percentiles—Soil moisture percentiles—2/8/20102/8/2010


Soil moisture—recentSoil moisture—recentSoil moisture—recentSoil moisture—recent





Soil moisture percentiles—Soil moisture percentiles—January 2010January 2010


Soil moisture—recentSoil moisture—recentSoil moisture—recentSoil moisture—recent





Soil moisture percentiles—Soil moisture percentiles—December 2009December 2009



Latest spring flood outlookLatest spring flood outlookLatest spring flood outlookLatest spring flood outlook


Assumptions / notesAssumptions / notesAssumptions / notesAssumptions / notes

• This outlook assumes near normal temperatures and This outlook assumes near normal temperatures and precipitation (i.e., climatology) during the outlook precipitation (i.e., climatology) during the outlook period.period.– If conditions are not near normal then the probabilities in is If conditions are not near normal then the probabilities in is

outlook may not be valid.outlook may not be valid.• For example, if above normal precipitation is expected For example, if above normal precipitation is expected

during the outlook period, then the probabilities in this during the outlook period, then the probabilities in this outlook may be too low.outlook may be too low.

– Outlook assumes near normal through late April.Outlook assumes near normal through late April.• Official temperature outlook Official temperature outlook near to above normal. near to above normal.• Official precipitation outlook Official precipitation outlook no strong trend signal. no strong trend signal.


Assumptions / notesAssumptions / notesAssumptions / notesAssumptions / notes

• Ice jamsIce jams– Any ice jams which do occur may result in locally higher river Any ice jams which do occur may result in locally higher river

stages and rapid river rises. This outlook does not take into stages and rapid river rises. This outlook does not take into account potential flooding from ice jams. Any flooding from account potential flooding from ice jams. Any flooding from ice jams would be above and beyond the flooding potential ice jams would be above and beyond the flooding potential indicated in this outlook.indicated in this outlook.


Temp & precip outlook through late AprilTemp & precip outlook through late AprilTemp & precip outlook through late AprilTemp & precip outlook through late April


El Nino—nowEl Nino—nowEl Nino—nowEl Nino—now


El Nino—forecastEl Nino—forecastEl Nino—forecastEl Nino—forecast

Decreasing El Nino with Decreasing El Nino with timetime


Median (50% chance) flood categoryMedian (50% chance) flood categoryMedian (50% chance) flood categoryMedian (50% chance) flood category


Risk of Risk of minorminor flooding floodingRisk of Risk of minorminor flooding flooding

West 1/3 of Iowa (Missouri River basin)West 1/3 of Iowa (Missouri River basin) East 2/3 of Iowa (Mississippi River basin)East 2/3 of Iowa (Mississippi River basin)


Risk of Risk of moderatemoderate flooding floodingRisk of Risk of moderatemoderate flooding flooding



Risk of Risk of majormajor flooding floodingRisk of Risk of majormajor flooding flooding




Final thoughtsFinal thoughtsFinal thoughtsFinal thoughts



• Most homeowners’ insurance policies do not cover Most homeowners’ insurance policies do not cover flood-related losses.flood-related losses.– To cover flood-related losses, flood insurance must typically To cover flood-related losses, flood insurance must typically

be purchased. This is in addition to homeowners insurance.be purchased. This is in addition to homeowners insurance.– Disaster assistance, if it’s available, is typically a loan that you Disaster assistance, if it’s available, is typically a loan that you

must repay with interest.must repay with interest.– In most cases, flood insurance requires a 30-day waiting In most cases, flood insurance requires a 30-day waiting

period before it becomes effective.period before it becomes effective.– Visit http://www.floodsmart.gov/ for more information.Visit http://www.floodsmart.gov/ for more information.



• Will we see another “2008”?Will we see another “2008”?– A big factor in 2008 was the heavy rainfall from May-June.A big factor in 2008 was the heavy rainfall from May-June.– High-end events such as the 2008 floods typically result from High-end events such as the 2008 floods typically result from

a sequence of additive factors. While one factor by itself may a sequence of additive factors. While one factor by itself may not lead to a high-end event, the combination of factors not lead to a high-end event, the combination of factors elevates the risk of a high-end event.elevates the risk of a high-end event.

– Factors which contribute to significant flooding this spring are Factors which contribute to significant flooding this spring are lining up.lining up.

– This does NOT automatically mean that we’ll have a repeat of This does NOT automatically mean that we’ll have a repeat of 2008 though. We could luck out this spring—the flooding 2008 though. We could luck out this spring—the flooding may be less severe than our outlook indicates. But, the risk may be less severe than our outlook indicates. But, the risk of flooding is elevated so we need to watch things closely.of flooding is elevated so we need to watch things closely.



• Spring flood outlook scheduleSpring flood outlook schedule– 1st Outlook: Friday, January 29, 2010.1st Outlook: Friday, January 29, 2010.– 2nd Outlook: Friday, February 19, 2010.2nd Outlook: Friday, February 19, 2010.– 3rd Outlook: Friday, March 5, 2010.3rd Outlook: Friday, March 5, 2010.– 4th Outlook (Optional): Friday, March 26, 2010.4th Outlook (Optional): Friday, March 26, 2010.



QuestionsQuestionsQuestionsQuestions

Contact information:Contact information:[email protected] or [email protected]@noaa.gov or [email protected]

515-270-4501515-270-4501http://www.weather.gov/desmoineshttp://www.weather.gov/desmoines

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