Tim’s Weather World: A Sunday smattering or smackdown?

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What a start to the snow season!  We have had at least flurries 8 of the last 9 days and we are forecasting at least flurries for 5 of the next 7 days.  O’Hare has seen just under 10″ of snow for the season.  That nearly doubles what we typically see through this point of winter.  Last year we only had a trace of snow so far.

After a quick shot of .5″ to 1″ of snow thi smorning the next significant snow will probably fall on Sunday.  The computer model solutions aren’t exactly in agreement at this point.  The European model (see image below) is suggesting a more robust storm with total accumulation by Sunday night at nearly 10″.  About an inch of that will fall prior to the Sunday storm.  The GFS model (see image below) is spitting out 1.7″ total accumulation through Sunday night with .4″ coming prior to the Sunday storm.

Tim Midwest - ECMWF 10 Day Snowfall Accum

Tim Midwest - GFS 10 Day Snowfall Accum

Either way, the prospects for a white Christmas are excellent.   Both models agree cold air will follow the snow so any snow that falls should stick around for several days.

Fun snow fact of the day…

As of yesterday, 46% of the contiguous US had snow cover with an average depth of 3.5″.



Tim’s Weather World: Bitter cold then sticking snow

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In the wake of the first significant snow of the season (3.1″ at O’Hare) Arctic air will strengthen its grip on the area with wind chills tonight dipping down to 5 to 15 below in our coldest spots tonight. A reinforcing shot of Arctic air will arrive Wednesday and by Thursday morning most outlying areas will see subzero lows.   It could be just the second time in the last 30 years to see temperatures dip below zero so early in the season.

High temperatures on Wednesday may not get out of the teens.  That would be the coldest day we have seen since a high of 14° on February 1st this year.

A clipper system will carry that bitterly cold air here and when it passes through early Wednesday it could lay down a fresh coating of fluffy snow.  Early indications are 1-3″ could accumulate.  Beyond that, another system late Friday into early Saturday has the potential to squeeze out 2-4″ of snow.

This has been a snowy start to winter, at least relatively speaking.  The first 1″ snowfall last winter didn’t occur until January 25th while the first 3″ snow didn’t hit until February 26th.




Tim's Weather World: Dramatic December temperature drop coming

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Meteorological winter* started Sunday with temperatures at or just above average for early December.  40° is the average high for this time of year. Today will also be at or above average for most.  Tuesday should be the warmest day of the week with highs in the lower 50s or what we typically see in early/middle November.  Check out the forecast temperatures from the GFS model for 5 PM Saturday.  Brrrrr…….


Tim Midwest Highs NAM

Enjoy it while you can because Arctic air will come crashing in by the end of the week with the coldest air of the season so far.  We will barely climb into the lower 20s for highs Friday and Saturday with wind chills dipping below zero at times.




Once the cold air arrives it looks like it will stick around for a while. The 6 to 10 day forecast from the Climate Prediction Center has us outlooked for below average temperatures (see image above) during the second week of December.  So if you still have holiday decorations to put up outside you better get to it soon.


*December, January and February are the three coldest months of the year.




Tim's Weather World: How to help tornado victims

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24 tornadoes touched down in Illinois during the outbreak of severe weather on Sunday, November 17th.  The strongest twister tore through Washington with EF-4 winds (168-199 mph).  The storms swept many homes off their foundations and caused incredible destruction.  Governor Quinn has declared at least 13 counties disaster areas.


CLTV, WGN-TV, and WGN Radio are teaming up to support McCormick foundation’s Illinois Tornado Relief Fund.   Steve Cochran will help kick-off “Relief Day” tomorrow (Tuesday) on WGN Radio starting at 5am.


The Illinois Tornado Relief Fund will support nonprofit agencies providing disaster relief and recovery efforts to those communities hit hardest by the tornado. The McCormick Foundation will match the first $500,000 raised at 50 cents on the dollar.


You can donate to the Illinois Tornado Relief Fund in one of the three following ways:


  1.        Online: http://www.wgnradio.com
  2.        Call the toll-free phone number: 1-800-931-5707
  3.        Mail a check payable to:

Illinois Tornado Relief

McCormick Foundation Processing Center

23912 Network Place

Chicago, IL 60673-1239


If you are looking for a Christmas gift….


WGN-TV is partnering again with Midland Radio and Walgreen’s and donating a portion of proceeds raised by the sale of Emergency Weather Radios to the Red Cross relief efforts.  The radios will be sold at a special promotional price until the end of 2013.  You can give a gift, possibly save a life and help out those hit by the tornadoes all at once.  A win, win, win deal!






Tim's Weather World: Turkey day travel looking good

HIST turkeys_009.JPGThe early outlook calls for smooth sailing if you plan on travelling next Wednesday for Thanksgiving.   The only real travel trouble you might experience is in the southeast.  A storm lifting north from the Gulf will bring rain to much of the Mid-Atlantic region.  It does appear the Arctic air that comes crashing in here Friday will linger through the holiday though.   We could be anywhere from 10-15° below average next Thursday.  The graphic below displays the weather for noon on next Wednesday.  That is rain in the southeast and a little snow in Montana and over Lake Superior.GFS_06_opUS_P1KS_0156

My best guess for next Wednesday and Thanksgiving:


Wednesday:  Partly cloudy, 35°

Thanksgiving:  Partly to mostly cloudy, flurries possible, 32°


Could be worse…


The high on Thanksgiving day in 1930 only got up to 14°.   It got as cold as -1° on Thanksgiving morning 1950. On Thanksgiving day in 1980 3″ of snow fell.





Tim's Weather World: How unusual are tornadoes in November?

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A Washington resident sifts through the debris from Sunday’s tornado.


There were more than 80 tornado reports yesterday from across 5 states according to the Storm Prediction Center.  While many of those reports will probably end up being multiple reports for the same tornado, the magnitude of the outbreak that occurred Sunday is rather unusual.   There have only been 12 tornadoes in Illinois during the month of November since 1950 when accurate records began.  That averages out to roughly one tornado per decade.  April, May and June are the peak months for tornadoes in Illinois (see image below).  The tornado that did damage near Coal City Sunday has been rated an EF-2 with winds between 111-135 mph.





So while tornadoes due occur in November here and elsewhere around the country,  the scale and intensity of this outbreak makes it one of November’s worst.  At one point there were more than 6 million people in the “high risk area” outlooked by the Storm Prediction Center.  “High risk” is serious stuff and is usually only issued once or twice a year.  Here is the criteria for a “high risk” of severe weather according to the SPC:


The HIGH risk area almost always means a major severe weather outbreak is expected,
with great coverage of severe weather and enhanced likelihood of extreme severe
(i.e., violent tornadoes or extreme convective wind events over a large area). Within a
high risk area, expect at least 20 tornadoes with at least 2 of them rated F3+, or an
extreme derecho causing 50+ widespread wind events (50+) with numerous higher
end wind (80+ mph) and structural damage reports.

The high risk area reached all the way to Chicago for Sunday, the farthest north since 1984 for so late in the year.


The above photo is an aerial view of the devastation wrought by Sunday’s tornado in Washington, Illinois.



Tim's Weather World: October's weather whiplash


Another case of weather whiplash…


September went down in the books as the 6th warmest for the contiguous US. , or 2.5° above the 20th century average.  Temperatures then tumbled in October.  October was the 37th coolest on record, 0.6° below average.  Locally, Chicago had an average temperature of 53.1°,  .6° below average in October.  That followed a warmer than average September here that was 2.6° average.


While it was cold for most of US it was almost balmy in Alaska.  Alaska had an average temperature 8.8°F above the 1971-2000 average making it the warmest October on record.



Here are more highlights from the National Climatic Data Center’s summary for October:


  • Below-average temperatures dominated west of the Mississippi River. Oregon had its 11th coolest October, with a monthly temperature of 46.3°F, 3.0°F below average. No state had October temperatures that ranked among the ten coolest.
  • The year-to-date contiguous U.S. temperature was 55.7°F, 0.7°F above the 20th century average, and the 32nd warmest January-October on record
  • The October national precipitation total was 2.23 inches, 0.12 inch above the 20th century average.
  • An early-season blizzard hit northeastern Wyoming and western South Dakota on October 3rd–5th, dropping up to three feet of snow with winds in excess of 70 mph. Rapid City, South Dakota received 23.1 inches of snow, breaking several October snowfall records for the city. An estimated 20,000 head of cattle died during the event in South Dakota, approximately 15 to 20 percent of the state’s entire cattle population. The storm was rated a Category 3 (Major) on the Regional Snowfall Index.
  • According to analysis by the Rutgers Global Snow Lab, the October snow cover extent across the contiguous U.S. was the fifth largest in the 46-year period of record at 132,000 square miles, more than 60,000 square miles above average. Conversely, the Alaska snow cover extent was 53,000 square miles below average, and the ninth smallest October snow cover extent on record.
  • According to the October 29th U.S. Drought Monitor report, 34.7 percent of the contiguous U.S. was in drought, down 6.5 percent compared to the beginning of the month and down 26.4 percent since the beginning of the year. Drought improved for parts of the Central Rockies and Great Plains, while drought conditions developed across parts of the Northeast.
  • On a local basis during October, there were slightly more (1.2 times as many) record cold daily highs (698) and lows (407) as record warm daily highs (242) and lows (689).




Tim's Weather World: Looking back at a sultry September

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Some warm thoughts as the coldest air of the season so far comes crashing in today….

The numbers have all been crunched and it seems this past September was a fairly warm month.    It was the sixth warmest September on record with an average temperature for the contiguous U.S. of 67.3°F, or 2.5° above the 20th century average.


Here are some other highlights from the National Climatic Data Center’s report:





Tim's Weather World: Jumping into winter next week

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We got off to a cold start this morning with wind chills dipping into the lower 20s but this could just be a taste of what is to come next week.  Flakes could fly as temps tumble by next Tuesday.  The coldest air of the season and coldest in nearly 8 months will come crashing in late Monday into Tuesday.  Computer models are suggesting that snow could stick Monday and Tuesday to the tune of nearly an inch.  The ten day accumulated snowfall from the GFS and European models both suggest our first real snow of the season is on the way.


Speaking of snow….


14.3% of the contiguous US is reporting snow cover.  That is almost quadruple the snow cover at this point last year (3.8%).


Tim Midwest - ECMWF 10 Day Snowfall Accum (2)Tim Midwest - GFS 10 Day Snowfall Accum (1)




Tim's Weather World: Mild by middle of the month?

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The first three days of November have all seen below average temperatures.  The long range forecast offers hope for warmer weather overall through the second and into the third week of the month.  The Climate Prediction Center has most of the eastern two-thirds of the country outlooked for above average temperatures overall from November 9th through the 17th.  The average high for the 9th is 52° and by the 17th the average high drops to 47°.





Meteorologists use “teleconnections” for long range forecasting.  Here is the definition of teleconnection according to the American Meteorological Society:


  • A linkage between weather changes occurring in widely separated regions of the  globe.
  • A significant positive or negative correlation in the fluctuations of a field at widely separated  points.
    Most commonly applied to variablity on monthly and longer timescales, the name refers to  the fact that such correlations suggest that information is propagating between the distant points  through the atmosphere.

The North Atlantic Oscillation Index is an example of a teleconnection that meteorologists monitor in order to get clues for longer range forecasts.  It is an index that gauges the sea-saw sea level pressure variations between the polar low and subtropical high.  NCAR (National Center for Atmospheric Research) narrows it down to “the difference of normalized sea level pressure (SLP) between Lisbon, Portugal and Stykkisholmur/Reykjavik, Iceland.”  Positive values of the NAO index usually portend milder than average temperatures here while negative values correlate to colder than average temperatures.  Most models are indicating the NAO index will remain mostly positive through the middle of the month.