The End of Meteorological winter

It been a rather unusual winter with above normal snowfall and below normal temperatures. This is not what was anticipated based on the fact that there was an on going EL Nino for much of winter. Abnormally warm waters in the Pacific typically leads to an active southern branch of the jet stream. This is exactly what unfolded but a persistant northwest flow in the northern branch of the jet stream across the eastern two thirds of the country brought in cold air from Canada. When these two jet streams merged they produced some prolific snow storms especially in the Mid-Atlantic states.

 What's interesting is that while we saw temperatures average below normal we never saw any frigid weather. The lowest temperature all winter was only -1° back in early January.

Meteorological winter is considered December through February. Now that we are heading into meteorological spring we do see some significant pattern changes. A more west to east flow will lead to a nice warm up late in the week with highs getting well into the 40s as we get towards next weekend. We possible could make a run at 50° by Saturday or Sunday. The last time we made it to 50° was back on December 1st nearly 90 days ago.

Phil

Retro-Weather

...and by that, I don't mean we're heading back to the 70s!  Instead, I'm referring to a phenomenon known as retrograde motion.  At our latitude, weather systems generally move from west to east.  However, occasionally conditions in the atmosphere cause storms to move contrary to the expected flow.  Such is the case today.  The massive and powerful snowstorm making national headlines on the East Coast is actually moving to the northwest, and it's western edge is now visible in the skies over Chicagland in the form of high thin cirrus clouds this morning.  During the day, the cloud deck will thicken as the storm spirals more moisture into our area from the Atlantic.  Eventually, snow showers will accompany those clouds.  I am not expecting much accumulation, but it does appear it will be stronger than mere flurries.  An inch or snow will be possible through Saturday.  That a storm so far away can have any impact here is a testament to the intensity of this monster.  The central pressure of the storm is comparable to a hurricane, and indeed winds gusting to near hurricane force have battered the coast.  Snowfall in excess of two feet has buried parts of New York, with flooding rains in coastal New England.  Stay tuned to the ABC-7 Mothership for amazing video from the hardest hit areas, as well as our forecast.

Mike

"Oh What a Night..."

I quote from the Four Seasons hit in reference to last night's remarkable squall which blew in with seldom-seen gusto.  Just before I took to airwaves at 4pm on Wednesday, a robust lake-effect snow band was assembling pointed toward Milwaukee.  During the newscast, I mentioned how that band would lead to possible white-out conditions.  Well, as my wife, her brother and I were about to leave my house to attend my son's school play around 6:15, the snow had just begun to fall.  By the time we arrived at school, it was a raging white hammer.  Nearly 3" fell in an hour's time!  We ended up with 5-6" in Lake County, but as the squall headed south, thunder and lightning accompanied the snow.  Thundersnow, as it's known, is more common than you might imagine.  Steep lapse rates, otherwise known as a rapid drop in temperatures with height, led to the thunderous snow showers.  Whenever you have thundersnow, 2" per hour snowfall rates are likely. 

The sun's back out today, but clouds from an intense low pressure system pounding the Northeast will return from the east tomorrow. Snow showers will be possible as well starting here tomorrow night into Saturday at least.

Mike

Update on Lake Effect

The Weather Service has replaced the lake-effect snow warnings in Lake and Porter Counties in Indiana with a lake-effect snow advisory.  In fact, that advisory now stretches all the way around the lake from Milwaukee to Michigan City, including Lake and Cook Counties in Illinois.  It looks as though a single, sustained plume will NOT develop and plow into NW Indiana.  Instead, multiple bands of snow, still heavy at times, will pivot around the lake through midday tomorrow. 2" to 6" totals will be possible.  Once again, some of this snow will affect counties outside the lakeshore.  We'll have the latest starting at 4pm!

Mike

WEDNESDAY, FEBRUARY 24, 2010

Good afternoon!  That lake...friend or foe?  Well, it depends on your perspective!  If you like snow, the lake will be your friend today...especially in Lake and Porter counties in Indiana!  It is possible that you could end up with 5-10" of snow by early tomorrow afternoon.  Here in Chicago, it's very likely that 2-5" of snow may accumulate here by early tomorrow morning!

We will keep you posted!

Tracy

Lake-Effect Snow On The Way

It's the not the most ideal set up for lake-effect snow, but sometimes conditions don't have to be perfect in order to crank out some pretty hefty snowfall off the lake.  Such is the case over the next 24 hours or so.  Lake effect snow advisories are in place for Cook, Jasper, and La Porte Counties, and Lake effect snow warnings are hoisted for Lake and Porter Counties in Indiana.  At this point, I think Porter County will see the most snowfall when all is said and done tomorrow evening... perhaps more than a foot. Farther to the west on the Illinois side, totals will be less.  However, as is commonly the case with lake-effect snow, bands of heavy snow will at times reduce visibility to next to zero, and a few inches of snow could pile up in a very short time.  Snow totals will likely vary greatly over short distances, so just be prepared for travel conditions which will change from clear to treacherous quickly.  Another caveat... just because it's called lake effect, that does not mean you have to live within eyeshot of the lake in order to get it!  There will be snow in counties which don't border Lake Michigan this afternoon as well. 

Mike

UPDATE on Lake Effect

I now fully expect a Winter Storm Watch or similar to be issued for late tomorrow into Thursday for the Michiana snow belt.  Jerry & I will have the details beginning at 4pm.

Mike

Mixed Bag Today

A fairly strong arctic cold front is moving into the Chicago area this evening, and with it will come a noticeable drop in temperatures.  Recent highs in the 30s will be replaced by 2 or possibly 3 days in the 20s with overnight lows dippping into the single digits in our usual colder spots.  This afternoon, there will be occasional bursts of impressive snow. Here at the station just before noon, flakes as big as hubcaps flew through the air for all of about 5 minutes. A few towns south of Chicago where 1/2" of snow feel already this morning, might pick up another quick 1/2" before this axis of snowfall moves away.  Clearing skies are already breaking out in our western counties early this afternoon, and most of us will get at least a little bit of that sunshine today.  Then the front hits tonight. Clouds will return along with a few snow showers.  Tomorrow I expect that snow shower threat to linger, bringing an inch or so of fresh powder to the area.  The exception will be in NW Indiana, where lake-effect snow might be much more impressive.  There are no advisories for this potential as of this writing, but I wouldn't be surprised if those of you in the Indiana snow belt get more than 4" tomorrow. 

Mike

Less than Feared

As a general rule, snowfall comes in at about a 10:1 ratio to the liquid which made it.  In other words, if you had an inch of liquid in a snowstorm, you could expect 10" of snow. Thanks to an unusually low snow to liquid ratio this time, snowfall totals were mainly in the 3"-5" range.  For example, O'Hare ended up with 3.1" of snow, from .49" of liquid.  That's a 6:1 ratio.  Romeoville milked 3.5" out of .59" liquid, also 6:1.  Batavia's 2.9" snowfall came from .52" of liquid, about 5.5:1. Farther north, slightly colder conditions led to higher snow yields, Woodstock's 3.0" from .27" liquid is an 11:1 ratio.  That lower ratio, coupled with  slightly more southern track of the storm kept totals on the low end of our forecast.  What's left is plenty of slush, and the dreaded "heart attack" snow that makes shoveling a real chore.  On the other hand, this snow is terrific for snowballs and snowman construction, so the kids will love it.  Up next, a shot of arctic air which will arrive tomorrow night with a few snow showers and decidedly colder temperatures.  Highs will be in the 20s Wednesday through Friday, so for those looking for signs of Spring, the wait continues.

Mike

MONDAY, FEBRUARY 22, 2010

Good morning.  Guess what?  It snowed this morning!  And wow, it's actually pretty...pretty heavy.  I was driving to work this morning and passing under some large trees when PLOP, big globs of heavy, wet snow splattered on my windshield!  It startled me for a moment, until I realized what had happened.  Many tree branches are bending from the weight of our recent snow storm.  From most of the totals which I have seen, widespread amount of 2-5" accumulated throughout the area.  Had this been a drier snow with a much higher water equivalent ratio, we could have ended up with 10" of snow. 

This particular storm was certainly far different from the snowstorms we have seen so far this season.  It is much more typical later in the winter season for us to get these heavier, wetter snows.  And while the snow paints the trees beautifully, it is definitely more difficult to shovel.  And when you use the snowblower, this is the type of snow that clogs it up more readily. 

So we're off to an active start this week, but that should be all for snowstorms...for now.  Tomorrow we will get some light snow showers with nothing more than one inch, followed by COLD for the mid-end of the week.

Tracy