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Posted at 03:24 PM ET, 01/15/2013

A cold, borderline frigid inauguration week is expected


As Matt noted, seasonal temperatures are expected for the remainder of this week. But an arctic front arrives Sunday, feeding cold air into the region for inauguration week.

Inauguration day high temperatures should be mostly in the 30s and a few snow flurries may even fly during the afternoon or evening.

By Tuesday and Wednesday, the pattern may produce the coldest weather in about two years with high temperatures possibly below freezing.

For the entire January 21-29 period, temperatures should average below normal, with a smattering of bitter cold. I expect a relatively dry pattern, but because of the cold, our chances for seeing at least some light snow are probably a little better than average.

While a cold pattern most likely dominates this period, the storm track is expected to be across the northern tier. Such a track suggests that a warmer than normal day or two may be interspersed among the prevailing really cold days. This happens when clipper systems track across the Great Lakes and temporarily modify our temperatures by shutting off the flow of cold air southward.

Yesterday’s Climate Prediction Center (CPC) 6-10 and 8-14 day outlooks did a good job of assessing the pattern

Technical discussion

The Day 8 and Day 11 CPC super ensemble mean 500 mb forecasts for the last several days - which show the general flow patterns in the atmosphere - have been remarkably stable and similar to one another. Today’s Day 11 simulation continues to show a strong ridge (red area) poking well northward through Alaska, implying arctic air will continue to spill southward as it flows from this ridge southward into the Great Lakes area and northeastern U.S.


A simulation of the atmospheric flow compared to average 11 days into the future. It suggests a big trough or dip in the jet stream along the East Coast, allowing arctic air to spill southward.

Yesterday’s CPC guidance indicated that in 90 percent of similar patterns in the past or “analogs”, temperatures were colder than average. Sixty percent of them gave us below normal precipitation.


(Left) percent of analogs showing below normal temperatures 11 days into the future. (Right) percent of analogs showing below normal precipitation.

The analog probabilities were not yet available from today’s Day 11 simulation. However, I did composite daily temperature anomaly maps for the beginning, middle, and end of the period based on the new analogs and they suggested similar probabilities to those offered above.

The 10 analog dates supplied by today’s CPC Day 8 and Day 11 mean maps are a cold grouping. At least two of the analogs, centered on Jan. 16, 1994 and Jan. 9, 1982, were associated with historic cold waves. The former led to brownouts across the region while the latter featured brutal cold for the AFC championship game (known as the “Freezer Bowl”).

Despite the general dry look over the January 23-29 period, three of the analogs included light snow accumulations within the 7-day window suggesting there is at least some but not a lot of snow potential. For those who like cold, they may have struck gold.

However, the lack of general snow cover will keep our temperatures from getting anywhere near as cold as 1994. The northern tier storm track will make it hard to get any significant snow unless some wave manages to track to our south. In such a pattern, a clipper type system which might produce some light snow is more likely.

Why we may get breaks from the cold in this pattern


Last night’s European model (see to the right) illustrates how we could get a warm day or two during a colder than normal period. While its forecast is probably far from being correct, it does show how any low pressure system tracking along the northern tier may modify and disrupt our coming cold.

Remember that the flow around a low pressure system is counterclockwise and is roughly parallel to the isobars, just cutting across them slightly towards lower pressure. The low level flow on the east side of the low usually is from the south.

If surface pattern for any day during the period was similar to the one shown above, low level southwesterly flowwould result for a day or two as the low pressure system scooted across the northern tier and the Great Lakes region. If a low were strong enough like the one on the European forecast, it could produce enough warm advection to raise our temperatures back into the 50s for a day.

The strength of the low on the European (above) is an outlier but the latest GFS also shows a low albeit weaker coming across the northern tier in the general period (sometime in the Jan 24-26 range) again suggesting the potential for a day or two of moderation from the cold. How much moderation and how cold it gets it is still up in the air as the models are getting into the time range when they have little or no skill.

Conclusion

Our coldest temperatures of the year are expected to arrive next week. Temperatures during the January 21-29 are expected to average below normal. However, our coldest temperatures probably will occur Tuesday and Wednesday. Some temporary moderation from the cold is possible towards Jan 24-26 timeframe as a low pressure system passes to our north. Snowfall chances are probably a little above normal with light events favored.

By  |  03:24 PM ET, 01/15/2013

Categories:  Latest, Inauguration

 
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