Fog & Rain... Tricky Wednesday Travel?

Moderate to heavy rainfall is occurring in central Illinois and southeast Iowa as of this writing, and indications are that this rain will soon be in the Stateline. Indications are that 1.5 to 2" of rain will fall across much of the area before all is said and done late Wednesday night and Thursday morning.

In addition to the rain causing ponding on the roadways tomorrow morning, motorists will want to keep an eye out for fog. Fog is already forming around Rochelle and DeKalb this evening, and will quickly spread northward tonight as rain continues to saturate the low levels of the atmosphere. Fog will be a problem through early afternoon tomorrow, and will probably thin-out later in the day as southerly winds and a warm frontal passage help temperatures separate from the dewpoint. Rain, however, will continue into the evening making travel a little slower than normal.

Lacking in the snowfall, but we'll be getting the rain

What has happened to our snow this season?  The past several Decembers have produced accumulating snowfall the first week and a half into the month but this year has turned out to be just a little different.

The general track of storms has been, for the most part, southwest to northeast - putting northern Illinois and southern Wisconsin on the warmer side of storm systems.  The one developing in the southwestern U.S. will be no exception.  It's hard to believe that New Mexico has seen accumulating snow before Rockford!  We have entered into a La Nina pattern, but we have to look a little deeper into what's causing this lack of snow and cold.  It wasn't but just a couple months ago signs were pointing to a snowy and cold start to winter, and that may still be the case later in the winter season, but there's one factor that we also have to look at: the North Atlantic Oscillation (NAO).  Discovered by Sir Gilbert Walker back in the 1920's, the NAO is basically the difference in atmospheric pressure patterns in the middle and high latitudes over the North Atlantic Ocean.  Last year we spent a majority of the winter in the 'negative' phase.  This featured a blocking high pressure over Greenland which helped  push the jet stream south across the U.S. allowing for cold, arctic air to surge over a good portion of the country.  For the past several weeks the NAO has been in its 'positive' phase which features an area of low pressure over Greenland and as a result keeps the jet stream further north across the U.S.

Taking us into the present time and the storm that brought rain and snow in the southwest Monday will track to our west from Kansas through north-central Iowa Wednesday before lifting into the upper Great Lakes Thursday.  High pressure over the southeastern U.S. will allow moisture from the Gulf of Mexico to be in full swing and strong southerly winds both at the surface and a few thousand feet above will help transport the moisture northward.  Rainfall totals reaching an inch or more remain possible heading into Wednesday night. 

Once that system has passed the weather should remain quiet until early next week when another low develops and could possibly take a similar track as the one moving in tonight.  The difference between the two is we might not have as strong of high pressure in the southeast pushing the low to our west.  After that passes another looks to develop around the 22nd of December and this one could yield a little snow just in time to make it a white Christmas.  We'll have to wait and see, but climatology tells us the later we get into the winter months without adding on the snow we may be running below our average snowfall.  Keep in mind, though, that all it takes is one storm to put you right back at or above.

Snow... A Dozen Days into December

Thanks to a mild weather pattern featuring southwest flow aloft, the first 12 days of December have only produced 0.1" of snowfall in Rockford. This is in sharp contrast to the last five years -- all of which have seen over 8" of snow in the first 12 days of the month. But considering our average snowfall for the entire month of December is 10.8", one could argue that we were due for a dry 12th month.

It still might feel a little odd, however, to be this snow-free at this point in the winter. After all, December is our snowiest month on average. Our snowiest December occurred back in 1951 when 33.3" of the white stuff fell. Needless to say, we're not on-track to even come close to that record! At this point, I'm just hoping for a little snow on Christmas and enough shortly after that to take my cross country skis out of the attic!  --TS

Weather pattern could get a little more active next two weeks

The next weather system forecast to move in looks to bring mild, but wet, weather into the Great Lakes towards the middle of this week.  As with previous systems, it appears as though we'll remain on the warm side of the next low forecast to move north from the southern Plains and pulling in a decent amount of gulf moisture with it.  Precipitation may start as early as Tuesday evening as a warm front lifts through Illinois.  With temperatures Tuesday night close to freezing the precipitation may start off as a mix before changing to all rain Wednesday.  With the amount of moisture expected to be pulled north, it's possible close to an inch of rainfall may be seen; the majority of it falling Wednesday into Wednesday evening.  A few showers may be leftover Thursday morning before colder air moves in Thursday afternoon.

After that system the weather will quiet down until early next week when another system looks to develop late Sunday into Monday.  Again, it looks like we'll stay on the warmer side resulting in mainly rain.  That system clears out by the middle of next week only to be followed by another one which could move in around December 22nd.  While it's not great, we may be able to squeeze a little snow out of it by the end of next week.  The chance of that looks low, however, so I wouldn't get too excited just yet.

Slick travel north this morning

A Freezing Rain Advisory will continue for about another hour for counties in southwestern and western Wisconsin.  A weak upper level disturbance moving out of the Plains this morning has provided enough lift to generate a few light showers.  However, temperatures overnight have been holding steady right around the freezing point which may cause a little freezing drizzle to mix in with the showers.  There is not threat for the immediate Stateline but if your travel takes you west of Monroe or north of Madison you may encounter a few slick spots on the roads.

Drizzle or even a light shower will remain possible for our western counties today while the mostly cloudy skies will stick around for the rest of us.

A Mild Week on the Way... Significant Rains Mid Week...

High pressure is sitting over New Jersey this evening. It is very large, and continues to dominate Stateline weather overnight. Skies will be clear to mostly clear this evening, but the southerly wind flow on the back side of the high will keep temperatures from dropping too much. The southerly winds will bring more moist air, and some clouds in from the southwest later tonight. The low temperature overnight will be in the middle 20's. Clouds will continue to increase, lower and thicken, on Monday, and there could be some very light rain showers or sprinkles on Monday. The high on Monday will be around 38 degrees, and the low on Monday night near 31 degrees. Stratus low clouds will shroud the area on Tuesday as the atmosphere continues to moisten up with a continued southerly air flow across the area. Temperatures will  moderate with a high in the low 40's.  Rain will spread across the area on Tuesday night as low pressure begins to develop over the Texas panhandle. The temperature overnight is expected to hold in the middle 30's.   Low pressure will be over southeastern Colorado by early Wednesday, and a warm front will be poised east-west across southern Illinois westward across northern Kansas. The low will intensify as it moves rapidly northeast on Wednesday. The track will take it well to the west of the Stateline so all of the precipitation with this system will be rain. It will be cloudy, rainy and mild on Wednesday with a high in the middle 40's. The warm front will push across northern Illinois on Wednesday night with more rain showers, and possibly even a thunderstorm. The low on Wednesday night will be near 40 degrees, but a cold front will sweep across the area on Thursday morning. Temperatures will reach the low 40's before brisk northwesterly winds cause the temperatures to drop slowly for most of the day. Canadian high pressure will bring colder air, and clearing skies to the area on Thursday night. The low will be near 23 degrees early Friday morning. Friday will be mostly sunny and colder with a high only around 30 degrees.

Sunny Sunday

That large cold area of Canadian high pressure has slipped off to the south and east of the Stateline. It is still close enough that skies will be clear overnight, but it will not be as cold as last night when the temperature dropped to 10 degrees.  That 10 degree low was the coldest temperature recorded at the Rockford Airport since February 11th, when it dropped to 2 degrees.  Tonight, with southerly winds the low will be in the upper teens.  On Sunday it will be sunny, breezy, and warmer with a high temperature in the upper 30's.  The wind will be south to southwest between 10 and 20 mph, with some afternoon gusts to 25 mph.  The southwesterly winds will continue on Sunday night, and temperatures will continue to moderate.  It will still be mostly clear on Sunday night with a low around 27 degrees.  Moisture from the Gulf will reach the Stateline on Monday.  The skies will cloud over holding temperatures in the upper 30's for highs, and there could be some patchy drizzle or light rain showers in the afternoon.  The drizzle may last through the night Monday night, and with temperatures dropping to freezing or just below, there could be some freezing drizzle .  So, look out for the possibility of slippery roads and sidewalks on Monday night.  On Tuesday it will continue to be mostly cloudy, and with a weak front sliding though the Stateline, temperatures will be in the 30's, and there could be some light rain or light snow showers.  No significant precipitation is expected on Tuesday.  On Wednesday a warm front will be located across central Illinois.  It will be cloudy and warmer with a high in the low 40's.  With moisture over-running the front there will be a good chance of showers.  The warm front will approach the Wisconsin-Illinois stateline on Wednesday night.  Rain will be likely, and there could be some significant rainfall totals.  Estimates at this time range from .50" to around 1.50". A cold front will sweep across the area by daybreak on Thursday.  High temperatures on Thursday, in the low 40's, will occur in the morning, and temperatures will fall in the afternoon.  It will be mostly cloudy, and there could be some lingering showers.  Colder air will move in on Thursday night dropping temperatures into the middle 20's.  It will be partly cloudy on Friday, and chilly, with a high only around 30 degrees.