Temps Going Above (Average) and Beyond

If you weren't a fan of November's unusual cold, December is trying to make up for those chilly temps.

Starting Friday, every day of the 7-Day Forecast will feature above average high temperatures. Granted, the average high next week sits at a cool 32°, but we are still technically above average with that high of 33° on Wednesday.

The long-term forecast shows the promise of a continued warm spell. The Climate Prediction Center says the Stateline has a 70-80% chance of warmer than average temperatures starting next week and continuing through Christmas. -BA

Chances for Above Average Temps: Dec. 19-25

Chances for Above Average Temps: Dec. 17-21

What's up with the clouds?

It's typical during the winter months to have cloudy days, but a little sunshine now and then would sure be nice.  Unfortunately, those pesky clouds we've had over the past few days may be sticking around a little longer through the weekend.

So, why is that?  Well, we have to look at what's going on in the atmosphere at the surface and above.  The image on the left is called a Skew-T diagram.  It's a 'snap shot' of the atmosphere taken from a weather balloon launched from the Quad Cities National Weather Service Wednesday evening.  Temperatures, in degrees Celsius, are located on the bottom and heights are located on the left hand side.  The green line shows the dew point temperature and the red line shows the temperature.  Something that often happens during the winter months is an inversion.  An inversion occurs when the temperature above is warmer than the temperature at the surface.  During the summer months, inversions can prevent afternoon thunderstorms.  In the winter, inversions can 'trap' clouds and fog near the surface making it hard for the clouds or fog to 'burn off'.

In order to weaken or break the inversion, you need the help of the sun.  In winter, the days are shorter and the sun angle is lower.  This doesn't allow us to maximize on heating during the afternoon.  Without that heating, inversions can last, and last, and last.  Now, if I've learned anything in my 10 years of forecasting it's that persistence is key.  We'll likely see the clouds linger into the weekend, but winds will begin to shift around to the south with an upper level ridge.  This should help allow a little more sunshine to peek through, but full sunshine may be hard to find.

Winter storm tracks: Which one favors snow

We've had a little snow here and there, but so far any big winter storms have bypassed the Stateline.  As we get further into the winter months, the likelihood of that trend continuing will go down.  So, I figured now would be a good time to look at which type of winter storm track brings rain, ice or snow to the Stateline.

First, the rain track.  Wind around low pressure flows counterclockwise and in order for rain to fall in northern Illinois and southern Wisconsin, we need low pressure to track west of us from Kansas City, MO to La Crosse, WI.  This track keeps the wind from the south keeping the colder weather in the Midwest and Plains.  Sometimes if enough cold air gets wrapped in behind the low once it passes, we can get some light snow.

The mix/icy track:  When low pressure dips into the southern Plains and then back up through Arkansas, St. Louis and Chicago we tend to see a higher likelihood of either a rain/snow mix or possibly ice.  While we're on the 'cooler' side of the storm, winds a few thousand feet above may still have a southern component to them.  This means precipitation that falls through that warmer layer can melt, but because surface temperatures are likely at or below freezing the rain will refreeze at the surface.

The snow track:  In order to get a big snow in the Stateline, we need low pressure to track out of Oklahoma/Texas and move up through southern Illinois, Indianapolis and south of Detroit.  A general rule of thumb is that the heaviest snow band will fall northwest of where low pressure travels.  With this track, we never get into the warmer side of the low and as moisture is gobbled up from the Gulf, it interacts with the cold air at the surface creating heavy snow.  This is sometimes called a 'Panhandle Hook' because it moves out of the Panhandle of Texas and forms a 'J' is it moves northeast.

Looking ahead, there doesn't appear to be any major systems on the horizon.  The southern branch of the jet stream will stay pretty active over the next couple of weeks, but if it interacts with the northern branch and cold air we could end up with some snow.

Feeling cool, but temperatures have been near average

It may have felt chilly the past week and a half, but high temperatures have actually been near average.  The beginning of the month didn't start that way, but shortly after we were in the middle and upper 30's and have been within the average of a few degrees.

Temperatures will remain above average through early next week with a return back to seasonable weather after.  Even though we'll see the thermometer dip back down, it doesn't appear as if we'll return to the deep freeze before Christmas like we were during the month of November.

East coast storm slows Great Lakes warm up

The warm up for the Stateline is something that has been advertised for the past week now, but it's just going to take a little while to get there.  The reason: low pressure developing off the east coast.  The messy system that brought us the wintry mix of rain, freezing rain, sleet & snow Monday morning will combine with low pressure in the Atlantic and bring rain, freezing rain and heavy snow from the mid-Atlantic up through New England.  That strengthening low will cause the jet stream to slow down and buckle across the middle of the country.

This will keep us locally under a cooler north wind through Thursday.  It won't be until late Thursday that high pressure in the northern Great Lakes will move south, switch our winds around to the south and allow temperatures to warm up going into the weekend.  Highs beginning Thursday will warm above average and will stay that way until the beginning of next week.  If cloud cover is able to hold off long enough and we don't receive any rainfall, temperatures have a decent shot of rising near 50 degrees.

Update: Monday morning commute

Illinois road conditions
Wisconsin road conditions

(8:15:56 AM) nwsbot: Local Storm Report by NWS DVN: 1 ESE Nora [Jo Daviess Co, IL] trained spotter reports FREEZING RAIN of E0.10 INCH at 08:13 AM CST -- glaze of ice on manmade surfaces

10:00am Update: Dense fog as really set in this morning and will continue to do so until winds shift around to the northwest behind a cold front.  This doesn't look to happen until at least early afternoon.  Use extreme caution while traveling today.  Current temperatures remain in the low 30's.

7:35am Update: Back edge of the sleet, freezing rain & rain will continue to move east of I-39.  As the radar begins to dry out, dense fog is beginning to set in.  Dense fog is found west of Rockford with visibility dropping less than a half a mile.  Temperatures range from 31° to 34°.

6:30am Update:  A few school districts will be starting on a 2hr delay this morning due to icy road conditions.  Those are: Forrestville Valley, New Glarus, Eastland Schools, Stockton & Chadwick-Milledgeville.  For a complete listing, click here.

Some roadways will be a little icy this morning with temperatures hovering between 30° and 33°.  Light freezing rain and sleet have been falling early this morning with some places reporting a thin glaze of ice on untreated surfaces.  A mixture of rain, sleet & freezing rain will occur with the back edge of the precipitation clearing the Stateline from west to east after 8am.

Salt trucks were out earlier this morning on main roads, but secondary and untreated roads, parking lots and sidewalks will be slick.  Especially for areas along and north of Highway 72.  Temperatures will remain in the low 30's through mid-morning when we begin to warm into the upper 30's by the afternoon.  A secondary disturbance swinging through this afternoon will bring the potential for light snow later today.

Slippery Monday Commute

You'll want to allow extra time Monday morning if you're headed to work or taking the kids to school. A low pressure system near the Canadian border is tracking east and will bring a wintry mix of precipitation to the Stateline. The system will bring the possibility of freezing rain, sleet, and snow starting after midnight. The best timing for this to impact the Rockford area will be between 3am and 6am making for a slick commute. Overall accumulations of ice and snow will be under an inch, but up to an inch is possible, especially to the north and east. Even though accumulations will be low, the precipitation could fall heavily at times reducing visibilities and making driving hazardous at times.

Temperatures will rise through the late morning allowing for a mixture of snow and rain through the early afternoon. Temperatures tomorrow will warm into the upper 30s, with cloudy skies. Though most of the precipitation will have moved to the east, there is a chance for light rain and scattered flurries through the early evening, and then a chance for freezing drizzle Monday evening