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Posted at 02:24 PM ET, 01/24/2013

Roller coaster ride: Warm-up next week, then cold may return in early Feb.


Up and down we go. After our coldest weather in a few years, temperatures recover into the 50s next week. But beyond that, temperatures trend down and perhaps way down into the first week of February.

Next week’s warm-up

A brief moderation in temperatures is expected next week with highs climbing to the mid-40s on Monday (we may have some light rain or mixed precipitation early on) and into the mid-50s on Tuesday, and mid-to-upper 50s on Wednesday and Thursday.

However, the warm days may be marred by clouds and rain especially on Wednesday. This time of year there is always the potential for clouds and rain to ruin a warm day. We’ve already seen that happen once this year. Thursday’s temperatures are more of a question mark and will depend on how quickly a cold front works through the area.

Friday through February 7, cool down

Beyond Thursday the pattern looks like it will try to transition back to colder than average with highs mostly in the 30s and low 40s and generally dry weather. Snow does not seem likely next week (with the possible exception of a little very early Monday) before at least Saturday.

Winter lovers can take solace in that as we get into the first week of February it looks quite cold with a pattern similar to this week’s pattern. That suggests the probability of snow will rise back to a little above normal.

Technical discussion

A look at next week

During the first half of next week the southward dip in the jet will be well to our south giving us deep, mild southwesterly flow. The GEFS ensemble mean forecast from last night (see below) does a good job of portraying why Tuesday and Wednesday should be warm but also show the seeds of our next cool down towards the beginning of February.


Remember that the jet stream is roughly parallel to the height lines shown below while also running from east to west. The dip in the jet stream over the middle of the country has two impacts:

1) On the east side of the trough (dip in the jet stream) deep southwesterly flow is present. The surface low that is expected to develop to the lee of the Rocky Mountains should track to the Great Lakes by Tuesday evening. The deep southwesterly flow will pull plenty of warm air ahead of the trailing cold front explaining the expected warming trend of early next week.

2) On the west side of the trough, the upper flow is forecast to be from the northwest. The strong ridge (red area) just off the west coast forces the jet stream northward across western Canada and then southeastward into the U.S. That northwesterly and cross polar flow suggests more cold air will eventually feed into the Plains. Some of that cold will eventually reach our area towards the beginning of next month.

A look at the February 1-7 period

The CPC D+11 composite super ensemble mean (below left) suggests the temporary warming next week will be short lived and that the pattern will revert back to the one of this past week. Remember that such a chart is the average of the forecast for seven consecutive days. The resultant flow pattern is then used to identify years in a week in which the flow was highly correlated (similar), or analog year.


CPC forecast D+11 mean 500 mb flow pattern for the week centered on February 4 (left) and January 24 (right, the current week). Blue areas depict below normal heights and red areas above normal heights.

The flow pattern portrayed for the first week of February closely resembles the flow pattern this week (on the right panel) which has featured very cold weather and a couple light snow chances. Notice how similarly located the blue and red areas are on the two maps. They are almost carbon copies.

The ten analog dates for Feb. 1-7 (see left side of panel) featured very cold departures from normal from the upper Mississippi Valley to the East Coast. At least one of the analog dates (January 18, 1994) was identified by the composites prior to our current cold spell. Said analog featured frigid temperatures. The analogs identify enough snow events to suggest that snow chances would be higher than climatology.

Conclusion

We’ll be on a roller coaster in terms of weather over the next two weeks. Cold today, warmer than normal during the first half of next week, and a shift back to cold again for the first week of February. Next week offers no chances of snow but should yield rain around midweek before the weather dries out and turns colder again. Then very cold weather is possible along with above normal snow chances as we get into the first week of February.

By  |  02:24 PM ET, 01/24/2013

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