Mild Days Ahead, Before Winter Returns

Enjoy the mild temperatures while they last, because change is on the way as we head into the winter season.  (FYI: Meteorological winter begins Dec. 1, while astronomical winter [solstice] begins Dec. 21 at 10:28 AM this year).

Temperatures will be in the upper 30s to mid 40s across eastern Iowa through Wednesday.  It’s late Wednesday into Thursday that we see a strong trough dig into the southwestern United States. An area of low pressure develops at the base of the trough, and will begin to track northeast.

At this point in time (Saturday evening), there’s still a spread in guidance as to where the low pressure will track, which will be crucial in forecast how much rain/snow/mixture we receive, and the amounts. The Weather Prediction Center has out probabilities of seeing a quarter of an inch of snow/sleet (melted).  The greatest chance for that is across northern Iowa (click the image to make larger).

 

It will also determine how warm temperatures will get before colder air moves in behind.  We are a bit more confident in the cold air behind the system.  How cold?  That’s where confidence is lowered again.  It will all depend on the track of the storm and how much (if any) snow is on the ground.  Stay tuned for further updates.

In fact, the Climate Prediction Center has much of the center of the nation with a good chance of having below average temperatures through the end of the year.

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Posted under Climate, Temperatures, Winter Weather

This post was written by Kyle Kiel on December 16, 2017

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Probability of a White Christmas

The question on many people’s mind these days, “Are we going to have a white Christmas.”  Well, we can tell you that some of the computer model guidance goes out to Christmas, and the data is all over the place, so it is too early to have a definite ‘yes’ or ‘no.’  The best we can do right now, is show the historical probability of a white Christmas for Iowa.  This information is coming from the NOAA and NCEI (National Center for Environmental Information).  This is data pulled from 1981-2010.

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Posted under Climate, Holiday, Stats, Winter Weather

November 2017 Review & December Preview

It was a drier than normal month as far as rain and snow went across eastern Iowa.  And, despite the warm second half of the month, the cooler start to the month caused the monthly average temperature to be at, or just below average.  The only exception is Iowa City, which was 0.2° above the average.

    

The Storm Track 7 forecast calls for a warm start to the first few days of December, but we are certainly in for a reality check as we head into next week.  Here is how a typical December shapes up for Waterloo and Dubuque (where official records are held at the airports).

 

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Posted under Climate, Precipitation Totals

This post was written by Kyle Kiel on November 30, 2017

Not Too Often

High temperatures are forecast to reach 60° or warmer Friday. The chart below shows the number of times each day has had high temperature of 60 degrees or higher. The outlined area shows just a couple times during this time of the month.

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Posted under Climate, Temperatures

This post was written by Schnack on November 23, 2017

La Niña Advisory

The Climate Prediction Center (CPC) issued a La Niña Advisory in early November. There is a 65-75% chance of La Niña conditions this winter in the Northern Hemisphere.

So…what is La Niña?

La Niña occurs when surface temperatures near the equator, in the Pacific Ocean, become cooler than normal.

 

Sea surface temperature anomaly (difference from normal temperatures) for the week centered on November 1, 2017

 

The deeper blue shades near the equator in the photo above indicate cooler than normal temperatures.

Sea surface temperatures fluctuate from year to year in a natural cycle, with some years cooler and some warmer. This year, CPC expects a weak La Niña to influence the North American weather pattern.

In general, a La Niña pattern brings cooler and wetter conditions to northern parts of the United States. This winter’s La Niña is forecast to continue through early 2018.

For the current sea surface temperatures in the Pacific, click here.

For NOAA’s winter outlook, click here.

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Posted under Climate, NOAA

This post was written by Rachael Peart on November 15, 2017

Smallest Antarctic Ozone Hole in Decades

According to NASA, the ozone hole in the Antarctic saw its lowest peak level since the late 1980s. The ozone hole reached a maximum size of over 7 million square miles on September 11 of this year. That is more than twice the size of the United States.

This decline in the ozone hole size is due to “natural variability” and not a sign of healing, according to NASA and NOAA scientists. While yes, the size of the ozone hole is smaller than it has been, it is still larger than in the 1980s.

The ozone hole on September 11, 2017. Purple and blue colors indicate the least amount of ozone.

Antarctic weather conditions played a major role in the size of the ozone hole this year. The Antarctic vortex, a low pressure system above Antarctica (which rotates clockwise due to its location in the Southern Hemisphere), was warmer and unstable and that decreased polar stratospheric cloud formation. Having those clouds in the stratosphere promote chemical reactions that lead to ozone destruction.

The ozone hole over the Antarctic was first identified in 1985. It forms during winter in the Southern Hemisphere as the sun’s rays force reactions that deplete ozone molecules.

For more information, visit NASA’s site by clicking here.

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Posted under Climate, NASA, NOAA

This post was written by Rachael Peart on November 5, 2017

November Normals and Records

Welcome to November. This is the last full month of meteorological fall. As a reminder, we set the clocks back one hour on November 5 to mark the end of Daylight Saving Time.

Here are some records and normals for Waterloo and Dubuque for the month of November.

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Posted under Climate, Stats

This post was written by Rachael Peart on November 1, 2017

Halloween Extreme Weather

While it will be chilly this Halloween, it will not be a record cold holiday.  Here are some weather extremes from the “Big 4” through the years.  Have a safe and happy Halloween!  Eat all the candy you want.

 

 

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Posted under Climate, Holiday, Weather History

This post was written by Kyle Kiel on October 31, 2017

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Hard Freeze This Weekend

No doubt about it, this weekend is forecast to be the coldest weekend, so far, this fall season.  This weekend will likely mark the end of the growing season as well, with low temperatures Saturday night falling well below freezing.

The map below shows the areas that have/have not experienced a hard freeze.  The areas in gray have already experienced a hard freeze (temperatures <28°), the areas of green area regions that have not had a hard freeze yet, and the areas in brown have had no reports.

The map below shows the average first day of a hard freeze (28° or colder) across the United States.

In eastern Iowa, we generally see our first hard freeze between October 1st and October 20th, so we are a little behind.

Temperatures are forecast to be in the middle and upper 20s Saturday night and into Sunday, which will put an end to the growing season.

The Climate Prediction Center has a good chance of at or just below normal temperatures through the first week of November.

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Posted under Climate, Temperatures

This post was written by Kyle Kiel on October 26, 2017

Winter Outlook 2017-2018

The National Oceanic and Atmospheric Administration (NOAA) has released the 2017-2018 winter outlook.  Right now, a La Niña pattern is setting up.  This means that the waters of the Pacific Ocean, near the Equator, have colder than normal temperatures.

So, what does that mean in Iowa?  NOAA is predicting that portions of eastern Iowa have a chance of above average precipitation, whether that is in the form of rain or snow.

As for the temperatures, we have equal chances of a colder than average, warmer than average, or “average” winter.  This basically means there are no strong signs pointing one way or the other.

The bottom line here — yes, we will have cold and we will have snow.  Also, expect some bouts of warmer temperatures, and some bouts of very cold temperatures.  After all, it is winter in Iowa.

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Posted under Climate

This post was written by Kyle Kiel on October 19, 2017

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