First snow possible as early as next Sunday

This upcoming week will be fairly benign, weatherwise for the Upper Midwest. The only big player in town this week will be an area of low pressure that develops in the southeastern U.S. on Tuesday. As this system works into Ohio by Wednesday, we’ll remain on the far western fringes. I do expect some gusty north-northeast winds which will put the brakes on temperatures but the rain and snow showers will remain in Chicago, points east.
Our next weak cool front arrives Thursday with a few evening snow showers.  This will keep temperatures in the 30s for Friday through Sunday. However, by Sunday and Monday we will be eyeing a storm system working out of the southern Plains. Depending on the track, we could see some rainfall, some snowfall, or nothing at all. This has the opportunity to bring our first shoveling snow, but the details are quite limited at this point.

New this winter, I will be putting a percent-chance on wintry systems. This will preclude our official snowfall forecast maps by a few days, as we will only put snowfall forecast numbers out when a storm is about 24 hours away. (This allows for more accurate forecasts, and less changing from shift to shift. In addition, this means we will have a storm system on-shore in the western United States with reliable weather data). The 13WREX Probability Scale is broken into several different categories with a percent chance forecast that we will exceed that particular category. These probabilities will get fine-tuned leading up to the 24 hour threshold when our forecast for the storm will be issued. We believe this will allow people a better idea of what the storm potential will be, many days in advance.

The probability scale will also be included in our broadcast, mainly for larger-scale systems. -ES

13WREX Probability Scale:
Sunday December 4, 2011

  • 22% Snowfall Accumulation
  • 09% Snow >2 inches
  • 01% Snow >4 inches
  • 00% Snow > 6 inches
  • 00% Snow > 8 inches
  • 00% Snow > 12 inches
  • 00% Snow > 18 inches
  • 33% Precipitation type: All Rain
  • 33% Precipitation type: Rain/Snow Hybrid
  • 33% Precipitation type: All Snow
  • 26% Precipitation . 0.25 inches
  • 12% Precipitation >0.50 inches
  • 04% Precipitation >1.00 inches
  • 00% Precipitation >2.00 inches
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Posted under weather, weather geek

This post was written by qni_it on November 27, 2011

Cold Snap of Tomorrow vs. Cold Blast of the Future

Our latest computer models are showing several rounds of cold air dipping into our area and the first one is here tomorrow.  Today’s highs reached into the lower to mid 50s, while tomorrow’s highs will be in the upper 30s.  Another cold snap arrives on Tuesday and then again on Friday.  One of the models goes pretty far out in the forecasting world.  It’s more like la la forecast land.  2 weeks from today (Saturday), there could be a cold snap that dives in pulling down very cold Arctic air.  If this comes true, we are looking at highs in the lower 20s.  Actually, that cold snap is more like a cold blast.  All these dips of cold air will allow the ground temperature to stay cold enough to support snow accumulation.  It is safe to say, that it is time to break out all the winter gear and leave it out until spring.

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Posted under cold blast

This post was written by qni_it on November 26, 2011

Last serious warmth of the year

It’s certainly possible (if not probable) we won’t have any more 60 degree temperatures in Northern Illinois for the remainder of the year. We’ll go into an at-or-below-normal pattern in the next few days and stay there for at least two weeks, and by that time we’ll be well into December so a 60 would be record-breaking.

Don’t worry, they’ll be back next March! 😉

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Posted under weather

This post was written by qni_it on November 25, 2011

Pattern change in progress

Below is the raw output of the ECMWF model which shows the plunge in temperature that will be well underway in just a few hours. 12°C is equivalent to 54°F roughly. By Monday 12z (Monday morning) we’re down to -3.4°C, which is roughly 25°F.

There shouldn’t be anything bitter, looking at this forecast. However, at the very bottom, there is a significant chunk of cold air that arrives in the first few days of December. There is some very light QPF (or precipitation) by that time as well. And just by my quick analysis, I am a bit concerned about the amount of energy that drops out of Montana into Texas. It seems the models are allowing this precip and low pressure to mysteriously disappear. I wouldn’t be surprised if this gets resolved in future model runs, pointing to a bigger storm system for Dec 1-6 in the Central U.S.

Speaking of QPF, you can see it adds up about 0.22″ of precipitation tomorrow. We have high confidence this will fall as rain because the 2M TMP and 850mb TMPs all remain above zero. -ES

 

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Posted under weather, weather geek

This post was written by qni_it on November 25, 2011

Split Weekend: Rain and Snow… No Sun

Our next storm system starts to affect our forecast by later tonight and will last through the weekend.  Temperatures will play a huge role in what type of precip we see.  Starting on Saturday, our temperatures will stay well above freezing with the highest amount of rainfall here during Saturday morning.  Our temperatures will start to fall during the afternoon hours due to cold Canadian air wrapping around the low.  This will change any rain into a rain/snow mix by Saturday evening and then change to all snow overnight and into Sunday.  Some area could have light accumulation by Sunday morning.  For Sunday afternoon, the snow showers will have ended. However, the cold air will continue to sink in and the winds will pick up.  This will cause our temperatures to feel like the upper teens and lower 20s for Sunday afternoon.

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Posted under rain, snow, weather

This post was written by qni_it on November 25, 2011

Thanksgiving Day: 1990 – 2010

Looking back on the past 20 years of Thanksgiving, I found some surprising facts that I thought you might find interesting too.  Let’s start with averages.  In the past 20 Thanksgivings, our average high temperature is around 42 degrees with an average low of 24 degrees.  What I found interesting is that we have never had a high in the 60s or the 20s.  We have kept the afternoon highs pretty much in the 30s.  From 2010 to 1990, we have 11 highs in the 30s, 6 highs in the 40s, and 4 highs in the 50s.  When it comes to overnight lows, our coldest Thanksgiving start was 12 degrees back in 2002 and our coldest high was 31 degrees in 1995.  Our warmest Thanksgiving was 59 degrees in 1998 and our warmest start was 36 degrees.  However, we just beat the warmest start today with 39 degrees.

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Posted under climate/climate change

This post was written by qni_it on November 24, 2011

Fog: How Does it Work?

If you woke up Thanksgiving morning in the Rockford region and thought you’d see a little sunshine, I could imagine you were not too happy when you saw the gray, gloomy skies.  The air temperatures and dew point temperatures leveled off, resulting in the fog that enveloped the Rock River Valley.  In some areas, visibilities were under one mile.  The National Weather Service considers any visibility under one-quarter mile to be hazardous.

Fog, while similar in form to a stratus cloud, is low lying and very near the Earth’s surface.  When the air temperatures and dew point temperatures are typically within 3° or 4° of each other (relative humidity nearing 100%), the lower atmosphere becomes saturated with moisture.  Fog tends to form when a cool, stable air mass is trapped underneath a warm air mass.  The moisture in the atmosphere begins to condense as tiny water vapor particles attach themselves to tiny dust and ice particles that are in the air.  The result is a rather stable cloud mass of water droplets suspended in the air near the surface, which we call fog.

During foggy conditions, especially when there will be a lot of holiday travelers on the road, it is important to remember to use extra caution while driving.  Turn your fog lamps on.  Make sure you slow down while at intersections, as it may be tough to view any oncoming traffic lights.  Lastly, don’t forget to give yourself plenty of time to arrive at your destination.   -JA

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Posted under fog, safety, weather, weather geek

This post was written by qni_it on November 24, 2011

BBQ Alert on Thanksgiving?

The addendum to the official BBQ Alert guide says I can issue an official proclamation only on specified holidays. Now, I am in search for a good turkey-grilling recipe. If someone can figure out how to BBQ a turkey, be sure to let me know. You can post it on the 13 Weather Authority Facebook page. Link to the right.

I do know for a fact that Tyler, Texas based “Greenberg Smoked Turkeys” does smoked turkeys quite well…I spent many a Thanksgiving there early in my career.

As far as the nation’s airports go, we’ve got no big problems right now. According to the data at 6pm from the FAA, only Boston and San Francisco are seeing significant delays. There was a storm system bringing rain and inland snows to the Northeast. That has since moved off the Atlantic coast.

Have a happy Thanksgiving!

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Posted under BBQ Alert, news

This post was written by qni_it on November 23, 2011

Coast to Coast Storm Systems

Tons of people are flying and driving today and tomorrow to spend time with family during this Thanksgiving holiday.  Many of them will probably run into some issues due to two major storms system on each coast.

Airports in Boston, Philadelphia, and Seattle have canceled flights due to the storms.  Roadways in New England are difficult to drive on, thanks to 4-8 inches of snow accumulation. The good news is the storm system along the east coast will be gone by Thursday.

However, the storm system along the upper west coast is a different story.  They have had to deal with damaging winds up to 70 mph and flooding rains.  Once this storm moves inland, another system slides in for Thanksgiving afternoon.

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Posted under weather

This post was written by qni_it on November 23, 2011

We should expect shoveling-snow in the next 2 weeks

If the last five years are any indication, the shovels and snowblowers will get some use in the next week or two. Looking back through the past five years, our earliest occurrence of multiple-inches of snow came on November 30th and December 1st of 2008 when 4.8 inches of snow fell in the Rockford area.

The largest of the first-snows fell between December 7th and 9th when nearly a foot fell! On December 1, 2006 we set a one-day record with 10.7 inches.

While we see no definitive snows within the next 7 days, there will be a significant pattern change in the next week to ten days. This will definitely increase the chance of a snow producing storm system.

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Posted under snow

This post was written by qni_it on November 22, 2011