Update Wednesday Morning: Winter Storm Update

Wednesday Morning Update: 

10:25am Update: Just In:
The National Weather Service has canceled the Winter Weather Advisory for Chicago and surrounding areas.  Threat for any impacting weather is really beginning to dwindle.

The Winter Weather Advisory that had been issued for DeKalb and McHenry counties Tuesday evening has been canceled.  The Winter Storm Watch that had been issued for Chicago has been canceled and replaced with a Winter Weather Advisory.

Low pressure is currently lifting northeast through western Kentucky and Tennessee.  Ongoing severe weather along the Gulf has played somewhat of a role in the slight forecast shift of the low pressure system to the east, but we're still going to feel some impacts of the storm as we go through the afternoon.  The first biggest change to the forecast is that the impact out east for heavy, wet accumulating snow has gone down.  Temperatures right now are in the mid 30's and will stay in the mid 30's through the morning and afternoon.  There will still be a period of intense snow, but now it appears as if that will be more focused just south and east of Chicago.  Travel will still be impacted especially if you're traveling south along I-39 into central Illinois or out east along I-57 and I-55 and I-94 into NW Indiana and Michigan.

Locally, the biggest threat for travelers this morning will be the fog.  Locally dense fog has developed in southern Wisconsin and northern Illinois.  By late morning, likely after 10am, and early afternoon, a light rain/snow mix will develop along and east of I-39 - including Rochelle, Rockford and Janesville.  An upper level low swinging through around Noon today (indicated by the blue line on the image to the left) will keep the threat for the light wintry mix going into the afternoon.  Currently, there are reports of drizzle, sleet and light snow within that trough in Wisconsin and Iowa.  By the evening, temperatures will be cool enough to support flurries and light snow. 






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Original Post:
A significant winter storm is poised to pass just east of the Stateline for Christmas Eve. If you're traveling to or out of Chicago on Wednesday, you're looking at some major travel woes.

Here's the timeline for how this storm will affect Rockford. We will have the chance for a rain/snow mix in the morning. By late morning or midday, that mix is expected to switch over to snow chances for the afternoon and evening.

Right now, it looks like a narrow band of wet, heavy snow will develop somewhere around the Chicagoland area Wednesday. Within that band, 3-7" could fall in a matter of hours. Fortunately, it looks like that band will stay to our east, but accumulating snow will be possible for the central and eastern portions of the viewing area.

The National Weather Service in Chicago has issued a Winter Storm Watch for the Chicagoland area. Snow could fall at a rate of 1-2" an hour, creating near whiteout conditions to go along with messy roadways.

Locally, McHenry and DeKalb counties will be under a Winter Weather Advisory. Wet, heavy snow could make for slow goings on the road, but snow totals are expected to be less than what we see in Chicago.

Here's the snow forecast as of Tuesday evening. Areas west of Rockford will see little to no accumulation. Areas along the I-39/90 corridor (including Janesville, Rockford and Rochelle) are looking at 1-2" of snow with 1-3" possible for areas east of Rockford. The far eastern portions of McHenry and DeKalb counties could see up to 5" of snow in spots.

Check back here for updates as this next winter storm gets closer. -BA

Who may see snow and who could miss out

Low pressure beginning to take shape in the far southern Plains will be responsible for severe weather along the Gulf states later today and tonight and could bring snow only 70 miles away from Rockford Christmas Eve.

First, the weather for today.  The rainfall from Monday night is done, with only a little drizzle lasting through the morning.  There is snow falling in Wisconsin, Minnesota and Iowa but that will remain west of the Stateline this afternoon.  Temperatures will hold steady in the 40's before dropping back into the 30's by this evening.  Low pressure developing in the Gulf today will track through Tennessee, Kentucky, Indiana and into Michigan by Wednesday night bringing rainfall up through the Great Lakes, but could also produce some accumulating snowfall in central and northeast Illinois and southeast Wisconsin.  At this point, it looks like the immediate Stateline will miss out on the snow, but travel out east may become a little tricky.  The precipitation will likely spread north mid-morning Wednesday through central and eastern Illinois as a rain/snow mix with temperatures in the mid and upper 30's.  But as low pressure strengthens and deepens by the afternoon, there may be enough lift in the atmosphere to get snow to fall just to the west of the storm track.  Right now it looks like travel along I-55 and I-57 will be impacted south of Chicago and I-94 north of the city up into southeast Wisconsin.  I-39 could see some snow, or even a mix, but at this point travel doesn't look highly impacted here.  Further downstate the interstate could become slick.  Greatest potential for snow accumulation would be along a line from Bloomington, Kankakee, Chicago & Kenosha.  And then out east into NW Indiana.

With temperatures above freezing during the event, should snow develop it would be a heavier snow.  This means the snow would have more weight and moisture with it and with temperatures above freezing the past couple of days, it would initially melt on contact.  The snow will be done by 9pm Christmas Eve night. 

Further west of Rockford there will be no accumulating snow, and maybe not even any precipitation at all - especially if the low tracks further east.  While we're less than 36 hours away, the track of the low is still uncertain.  If you're holiday plans have you traveling on Christmas Eve, especially to the east, you'll want to pay close attention to the forecast as travel could become tough during the afternoon.  After that, the next system coming in Friday night doesn't look all that impressive.  Colder air is set to arrive just in time for the New Year.

Wet weather today. Some snow by Christmas?

A series of low pressure systems swinging through the Midwest and Great Lakes today and tomorrow will bring more wet weather than wintry weather through Wednesday morning.  This morning, however, temperatures are right at freezing, or 32 degrees, so as scattered drizzle and light rain has been falling there is the possibility of a few slick spots through 9am.  Areas that you'll need to watch will be parking lots, sidewalks, decks and bridges and overpasses.  By this afternoon, temperatures will rise into the upper 30's eliminating the threat for wintry weather.

An increase in moisture with low pressure today will keep a steady rain falling through the evening commute and overnight.  Temperatures won't fall off much tonight, and will likely rise into Tuesday morning.  The rainfall will be ending mid-morning Tuesday with drier wrapping in.  Temperatures will stay in the low 40's.  The passage of low pressure Tuesday evening will bring back the chance for a wintry mix that will last through Wednesday morning.

Rainfall totals through Tuesday morning could add up to half an inch.

Wednesday evening another low pressure system will track northeast through the Ohio River Valley.  While the exact track is still a little uncertain at this time, there is the possibility of accumulating snowfall not that far away from the Stateline.  Right now, the greatest threat for accumulating snow would be closer towards Chicago and NW Indiana.  Should that low shift further east, it will take any potential for snowfall east with it.  If it tracks a little further west, the snow band will also shift west.

First Day of Winter

Today marks the winter solstice, or the first day of winter at 5:03pm CT. It is also the shortest day of the year with the sun setting at 4:23pm, only giving us 9 hours of sunlight. We've been loosing a little daylight everyday since June 21st, the summer solstice, when we see our longest day of the year. On a more positive note, after today each day will get a little longer. The nights will get shorter and the days a little longer through June.

While Monday will be the first full day of winter, it won't feel like it. Temperatures will warm to 40° with rain in the forecast. But temperatures near freezing in the morning will allow for some light snow and freezing rain mixed with rain. Not much in terms of accumulations but could make the commute Monday morning a little messy with the few slick spots possible on roads, especially on bridges and roads not traveled as much. With temperatures warming early in the afternoon the precipitation will turn to rain. The periods of rain will continue through the evening and into the morning on Tuesday. The passage of a cold front on Tuesday will bring some drier air into the area and drops temperatures into the 30s for Wednesday.

Small Changes This Weekend, Bigger Changes Next Week

A small influx of moisture this weekend will lead to some minor changes in the upcoming forecast.

While we stay cloudy, we could also see some flurries on Saturday with highs near the freezing mark. As warmer air aloft moves in late Saturday night, some of those flurries could switch to some freezing drizzle, although it doesn't look like it will amount to much at this point. Once we warm into the mid 30s Sunday afternoon, any icy weather will switch to just regular drizzle.

As for next week, Monday will be upgraded to a Moderate Weatherisk with a better chance for rain. Tuesday will be a transition day as rain chances the first half of the day turn to snow chances late. We will see one more chance for snow Christmas Eve before a quiet Christmas Day. -BA

Watching the weekend

We've been focused on what's going to happen with the weather the week of Christmas, but there are a few things we need to look at for the weekend.  The southern branch of the jet stream stays pretty active keeping the majority of storms along the Gulf and out east.

Further north, though, weak subtle low pressure systems will move through the northern branch of the jet stream and could bring us a little wintry weather through Sunday.  Moisture remains limited, but as we've seen in the past few days even the weakest lift in the atmosphere can produce some very light precipitation.  The first of those waves was north in Minnesota and Wisconsin Friday morning and did bring very light drizzle/flurries to the Stateline between 3am and 5:30am.  The next wave that swings through will be early Saturday and then again Saturday night.  Flurries are possible under cloudy skies Saturday morning, but as temperatures begin to warm Saturday night freezing drizzle will be possible.  Temperatures at the surface will remain below freezing, but aloft we'll be warming.  While it's not going to be much, it could be just enough to cause some slick spots.  Throughout the day Sunday, warm air will continue to be pumped into northern Illinois and southern Wisconsin.  Temperatures will warm, but again, we could be dealing with drizzle or even freezing drizzle through Sunday night.  By Monday, there will be enough warm air in place to keep the majority of precipitation all rain before a changeover to light snow late Tuesday and Wednesday.

Next Week's Storm System: A First Look

Before we get into next week's storm system, it should be mentioned that a forecast looking this far out is inevitably going to change. The information outlined below is based off of what the model runs have been saying through Thursday. We'll outline some of the factors that are still up in the air in this post.

Something that is likely not to change is the timeframe we are keeping an eye on, which is Monday through Wednesday. Generally speaking, we are looking at temperatures warm enough on Monday for some combination of rain and snow. That will eventually transition to the chance for snow by Christmas Eve.

Here are some of the questions we are still hoping to answer as we get into the weekend. When does the chance for rain and snow switch over to the chance for just snow? The answer to that question will help us determine how much snow will be possible through Wednesday. How much snow we see (or don't see) will have an impact on anyone with travel plans around Christmas.

Stay tuned for more updates as we go through the weekend. -BA