Cold Returns Thursday Night

The warm stretch of weather we've had recently has been great and much needed. The weather pattern that produced pulverizing cold during the Christmas/ News Years timeframe was beaten down. These changes were only temporary apparently as arctic cold will be uncorked again across the northern plains.

Cold Encounters of the Terrestrial Kind

Following a storm system for Thursday, a strong cold front will sweep through Wisconsin. This will be the start of our next cold encounter. This outbreak will not be cold as the last, but if the ridge remains strong next week we could easily revert back to the end of 2017 in the near future. Many models bring warm air back in as early as the middle of next week, some do not and keep it brisk. For now, expect wind chill advisories this weekend or early next week. Sunday looks the coldest statewide right now with high temperatures in the teens and single digits, windchills decreasing to -20F or less at night (per the GFS forecast).

Sunday Night forecast windchills. It's early and things can change.

For Wisconsin this weekend into early next week, relatively speaking it will be colder across the northwest with fresh snow cover. It will be much colder across Minnesota and the Dakotas where the polar high seems to be zeroing in. In eastern Wisconsin temperatures will be relatively warmer with the chance of cloudy night or two keeping temperatures up. It is early and things can change.

Forecast temperature trend in Wisconsin Rapids, WI for the next 7 days. Not as cold as it was around New Years but still in the same category.

Why so cold?

Throughout December our weather pattern was characterized by consistent ridging in the west. This forced storm systems north across dry Canadian Rockies and pulled cold airmasses south into the northern plains. When the ridge broke down last week, the cold was shut off and warmer air was allowed to sneak in this weekend through this week. The pattern change is exemplified by a storm system moving across the southwest US lifting northeast into Wisconsin on Thursday, which hasn't happened in what feels like months!

500 mb wind speed showing upper ridge west, trough east and northwest flow returning to Wisconsin.

This weekend however we will see the ridge return. It seems a tendency towards ridging in the west will remain as we move deeper into this La nina winter. Weather patterns over the northern Pacific Ocean are changing towards a pattern that will favor wetter and relatively warmer pattern in Wisconsin. The CPC predicts warmer and wetter during the 8-14 day period as upper level troughing returns to the west. The image below suggesting perhaps a storm between Dec 16-22. Kind of reminded me of this.

Precipitation tendency during the 8-14 day period

Now that we've got the cold outbreak checked off the list, maybe mother nature could bring us some snow instead?

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