Friday, December 19, 2014

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.

Thursday, December 18, 2014

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

Wednesday, December 17, 2014

Christmas travel will likely be impacted across the U.S.

If you plan on traveling this holiday season, you'll want to pay close attention to the forecast.  Even if we don't see too much of an impact locally, a potentially big Christmas storm could have impacts on air and road travel leading up to Christmas.

A series of storm systems will invade the Pacific Northwest through this weekend, but most of those will bypass us to the south.  Late Sunday night, winds will begin to shift around to the southwest allowing temperatures to rise through Monday morning.  At the same time, an approaching cold front will begin to move east out of the Midwest and sweep across the Great Lakes Tuesday.  Ahead of the cold front, a mixture of rain and snow - and possibly freezing rain - could occur Monday and early Tuesday in northern Illinois and southern Wisconsin.  Heavier snow is possible further north into Wisconsin and Minnesota while rain develops further downstate.

By Tuesday, cold air wrapping in behind the cold front could bring a period of light to moderate snow during the afternoon.  This will be occurring at the same time low pressure begins to organize in the far southern Plains and gulf states. 

It's still a week away and many things will change between now and then, but it's important to put this storm system on the radar because it will be coming right before the holidays.  As low pressure moves across the Great Lakes Tuesday, another and stronger low will be developing in the far southern Plains.  This low looks to track northeast into the Ohio River Valley and cause some big headaches out east.  Whether or not we see impacts from this storm depend on where exactly the track takes it.

The European model has the low further west, closer to Illinois, which would have a greater impact on the Stateline with a mix and heavier snow through Christmas Eve night.  The GFS model takes that same low, but slides it further to the east.  We would still receive some snow, but it wouldn't amount to much.  It's still a ways away, but if you have plans on traveling next week you'll want to make sure to keep close tabs on the forecast.  There are still many different variables we have to look at going into next week.  We'll continue with updates, especially as we get close to Christmas.  Right now, the greatest travel impact days are going to be Monday night and potentially Wednesday evening of next week. 

Tuesday, December 16, 2014

Changing weather pattern could bring snow & cold to the Midwest

If you're worried that we might not see a white Christmas, I wouldn't lose hope just yet.  A changing weather pattern during the last week and a half of December may favor a cooler and more active jet stream pattern through the beginning of 2015.

We won't see much precipitation this week following Monday and Tuesday's rainfall.  High pressure building in late Tuesday will help keep the active branch of the jet stream positioned along the gulf states through the weekend.  A series of low pressure systems moving into the Pacific Northwest will follow the jet stream south and bypass the Great Lakes, especially with high pressure anchored overhead.  While we could come close to a little wintry weather Thursday and Saturday, high pressure overhead should limit how far north those lows move.  And even though temperatures will fall back into the low 30's, we won't be that far off from average highs as the coldest of the air remains bottled north in Canada and the Arctic.

Looking ahead into next week, though, there are some signs that point to a changing weather pattern.  High pressure building in the Pacific will push the jet stream up the west coast and into western Canada.  This in turn will cause a dip, or trough, in the jet stream to develop over the middle of the country.  This will cause the northern branch and southern branch of the jet stream to merge, or work together, and could cook up a couple stronger storm systems before and after Christmas.  It's still too early to tell whether or not these systems will impact northern Illinois and southern Wisconsin, or if we'll see all snow from them.  But it's something to keep in the back of your mind as many will be traveling or finishing up last minute shopping.  We'll keep the updates coming through this week and into the weekend as it looks like there will be some impact of the weather in time for Christmas.

Dreaming of a white Christmas?

Singing: ''I'm dreaming of a white Christmas"

Now that you have that song in your head, let's discuss the probability of seeing a white Christmas.
This map is from the National Climatic Data Center showing historically the areas that have the highest probability of seeing a white Christmas.  Based on data going back to 1981, northern Illinois and southern Wisconsin have roughly a 60% to 70% chance of seeing an inch or more of snow on the ground.

Keep in mind that this map doesn't mean we'll have a 60% to 70% chance of seeing a white Christmas, but rather climatologically the probability of snow on December 25th, and should only be used as a guide.  Actual conditions this year could, and probably will, vary from these probabilities due to current weather patterns.  If you're dreaming of a white Christmas, I wouldn't lose hope just yet.  A changing weather pattern could bring some snow to the Midwest next week.  More on that can be find right here.

Monday, December 15, 2014

Big Changes Coming Tuesday

It has been a mild and gloomy weather pattern across the Stateline the last several days, but winter will soon return to the Stateline.

All of the changes we see on Tuesday will be thanks to an area of low pressure sitting in northern Missouri as of Monday night. On the front side of this low, we will continue to see mild temperatures, rain, and areas of fog.

On the backside of this low, we will see falling temperatures throughout the day Tuesday. Precip chances will also be on the decrease, giving us the chance for a few lingering showers in the morning, a slight chance for a rain/snow mix around midday, and possibly a few snowflakes for the afternoon.

Once our next low passes, expect a cool and quiet pattern for the rest of the week. -BA

Impressive Cloudy Streak for Stateline

The sun has been pretty elusive around the Stateline the last month or so. Now that we finally have some sunshine back in the forecast this week, the National Weather Service in Chicago is putting our cloudy weather in perspective.

From November 1st to December 14th, the weather observation station at the Rockford International Airport has reported cloudy or mostly cloudy skies 80% of the time. That's more than 35 days of cloudy skies.

This past week (Dec. 7-14th) was even worse. Rockford reported cloudy skies a whopping 97% of the time.

At least the forecast is looking much better for everyone who loves the sun. Mostly to partly sunny skies will be in the forecast starting Wednesday and continuing through next week. -BA