2008/2009 Exclusive Winter Outlook

We’ve pored over the data, run tests, used many beakers and test tubes… okay, maybe not quite that extreme.

We won’t soon forget last winter when more than 70 inches of snow fell in the Rock River Valley. There will not be a repeat of that this season. However, we are expecting slightly above average precipitation. As far as temperatures go, it appears the cold weather from November will be carried on into December and possibly January. Because we’ll be starting the season in a deficit (temperature-wise), we feel compelled to continue with a slightly below-average temperature pattern through winter 2008/2009.

Summary:
Last winter, we were in a strong La Nina pattern. That has since subsided this fall into a near-neutral pattern, perhaps a weak La Nina. Generally, La Nina leads to temperatures that are cooler than average in the Midwest. Other large-scale signals indicate the potential for a similar situation in which cold air is able to build up in Alaska/northern Canada, then spill southward into the central United States.

The National Weather Service office in Detroit came up with a number of analogue years; that is, years in the past that were similar to what occurred this past year. They used years in which a La Nina was ongoing from winter through the summer, with a return to neutral conditions by fall. We used that technique in our Winter Outlook by looking back at what conditions Rockford experienced in the seven analogue years. While there was certainly variability in temperature and snowfall, we were able to identify a couple of general trends.

Temperature:
We can already get a glimpse into a good part of December using our ensemble computer models. What they suggest is a continuation of the cold. Aside from the first week of November, a significant long-term pattern has developed bringing us repeated bouts of cold weather. This trend is also very similar to one of the aforementioned trends from the analogue years. We found that December typically ended up with much below average temperatures – sometimes to the tune of 5°F below average. It also appeared that a significant cold wave would affect the Midwest after the middle of the month, sending Rockford’s temperatures below zero for several days. While we aren’t giving specifics within this Winter Outlook, it is hard to ignore such suggestions.

In any event, some moderation in temperature is expected into January (partially based on data from analogue years). Given that we are in a weak La Nina, or perhaps non-existent La Nina by February or March, we are given fewer signals of any deviation above or below. As a result, we are going to trend to near normal temperatures in January. For February, we are not seeing any notable indication for either above or below average temperatures, but data from analogue years points to the possibility for slightly warmer than average conditions. Even if February does end up warmer than average, we do not feel it will outdo the very cold December and near-average January.

In a nutshell, our Winter Outlook calls for below-average temperatures on the whole, particularly during the month of December.

Precipitation:
As with temperatures, a lack of a strong La Nina or El Nino doesn’t lend itself to making a precipitation outlook easy. Looking back at our analogue years, snowfall amounts had a high level of variability. A few years had vastly higher than average snowfall totals, while others had scarce amounts of snow. We are calling for average to slightly above average snowfall this winter, partly due to the fact that colder than average temperatures will favor snow.

Since cold air intrusions will be frequent for the first part of winter, we expect Alberta Clipper systems to be quite common. While these usually are starved for moisture and therefore produce relatively low snowfall totals, their frequency may mean more small snows more often. Recall only to last year when we had so many Alberta Clippers; the minor amounts of each one added up to a sizable portion of the 72.9 inch total for the season.

There is some indication that the dominant “Texas Hook” storm track may be a bit farther northwest this year than last year, putting the heavier snow bands northwest of Rockford. That doesn’t mean we won’t have any significant snowstorms; they just may become rarer into February and March of 2009.

Eric Sorensen
Adam Painter
Justin Gehrts

For additional reading:
NWS Detroit Winter Outlook – http://www.crh.noaa.gov/images/dtx/climate/winterout08.pdf [Note: keep in mind that the specifics pertain to Lower Michigan, not necessarily northern Illinois/southern Wisconsin]

WREX Winter Outlook Notes – http://www.justingehrts.com/files/winter_outlook_notes.pdf

Share

Posted under Uncategorized

This post was written by qni_it on November 25, 2008

10 Comments so far

  1. tony November 25, 2008 10:37 PM

    Now what are the chances this year of having a white christmas. I know last year we didn’t have one. But based on this, it looks like we may have a chance at it. Also will there still be a winter storm next week from the models. Of course, once march comes around, most people won’t be wanting major snows because spring would be just around the corner. I will bet this outlook will be hit right on the head.

  2. Dubuquer November 26, 2008 3:52 AM

    With the so-called “Texas Hook” farther northwest, or trending further northwest this winter season, would that mean more mixed precipitation?

    And, by “farther northwest” how much so (on average, I know this is very variable…)

    And, also, when should we expect our first snowfall (advisory or winter weather warning criteria) in Northwest Illinois?

    Chances of a white Christmas this year?

    And, precip has been below normal here for quite awhile– I take it this trend isn’t going to continue–based on the prediction of slightly above average precip?

    Thanks for everything you guys do for us.. and the Winter Outlook last year hit the nail on the head!

    -Cody in Dubuque, Iowa

  3. Justin Gehrts November 26, 2008 4:16 AM

    White Christmas chances can be found on the Weather page under the “13 Winter Authority” below the forecast. 🙂

  4. Eric Sorensen November 26, 2008 4:31 AM

    Dubuquer:

    The Texas hook storms will be later in the season. On December 1, 2006 we had a 11″ snow here in Rockford. While it’s possible we could get a big winter event later in December our northwest flow will provide more clipper systems…little snows.

    Our northwest flow (from December) may turn around by January and February as we’re expecting a moderation in temps. Should this happen, our Texas hook storms will be later in the season. It’s too early to tell where they will set up. -ERIC

  5. Dubuquer November 26, 2008 5:00 AM

    Thank You, Eric and Justin!
    So, expect light amounts of snow, but don’t rule out a good snow in the first half of December as a rule.
    I figured it would be too early to indicate where the TX Hook Storms would dump on us…
    Any indication on when the first decent snowfall may occur?

    Thanks for taking the time to answer my question

    -Dubuque, IA

  6. WI Weather Buff November 26, 2008 12:24 PM

    Interesting. Your Winter Outlook somewhat differs from that of NOAA:

    http://www.crh.noaa.gov/news/display_cmsstory.php?wfo=mkx&storyid=18761&source=0

    It will be interesting to see who's right when all is said and done.

  7. tony November 26, 2008 1:08 PM

    I actually trust 13 with their forecast more than the NWS and NOAA. Those two look at the whole country in general, while 13 focuses more on rockford and the surrounding area. I hope we have enough snow for a white christmas this year.

  8. Adam Painter November 26, 2008 6:46 PM

    Tony, jog your memory a bit but 2007 was registered as having a white Christmas. At least 1″ of snowpack was measured at 6 o’clock on Christmas morning. Granted with highs in the 40s it had melted away by sunset, but it still goes in the books as a white Christmas.

    WI Wx Buff, we are well aware of NOAA’s prediction. They had the same forecast for last winter, and our temperatures ended up actually a little below average instead of being on the warm side as they had predicted. I didn’t find much data supporting their 2008-2009 claim so I couldn’t jump on that bandwagon. Time will tell… it should be a fun 4 months!

  9. tony November 26, 2008 9:32 PM

    Oh ok, I actually don’t remember that but that’s cool. Shows how much of a short term memory I have.

  10. vicki September 11, 2009 6:05 PM

    what i am really looking for is some type of forecast for this coming up winter…have there been any predictions made yet for this winter or is this it?

Leave a Comment

Name (required)

Email (required)

Website

Comments

 

More Blog Post