A weather pattern we have seen many times since late October, 2013, has reappeared in its amplified form. The ridge of high pressure in the upper atmosphere has been building since late last week along the Pacific Coast, stretching from northwest Mexico to Alaska. This has pushed the jet stream far to the north into Alaska and the Yukon.
|The 500 mb pattern for North American at 00z January 21, 2014. Click on the image for a larger view. Image Credit: WLTX-TV.|
The result has been unseasonably warm temperatures for this time of year. It is still cold, but in Fairbanks the temperature averaged 24° F above normal on Monday. There have been wild swings in Fairbanks, AK, this month with its coldest temperature of -41° F on January 12th & 13th, and its warmest temperature at 34° F on January 17th. On that day the temperature averaged 32° F above normal.
|Alaskan temperatures at midnight January 21, 2014. These are warm readings for central Alaska in January. Click on the image for a larger view. Image Credit: WLTX-TV.|
As the jet stream plunges south into the southeastern U. S. it has been bringing to cold Arctic air from north central Canada. Here temperatures have been -20° F to -40° F. This is not as cold as the air mass at the beginning of the month, but still cold enough to cause problems.
|Canadian temperatures at midnight January 21, 2014. Click on the image for a larger view. Image Credit: WLTX-TV.|
All of the signs point to cold pattern persisting to the end of the month. The seven day forecast for Columbia, SC illustrates this as the temperature climbed to 70° F Monday afternoon, yet the high temperature is only expected to reach 35° F on Friday. The northwest flow aloft is also a dry weather pattern. The Arctic air is quite cold, thus devoid of much moisture. Relative humidities in the afternoon have been dropping into the 10-20% range. Very dry air, indeed!
|The 7-day forecast produced on January 20, 2014. Click on the image for a larger view. Image Credit: WLTX-TV.|
The 6 to 10 day forecast, covering the period from January 26th through January 30th, shows a continuation of this pattern into next week. The eastern half of the nation will be colder than normal while the western half is well above normal. Alaska will similarly experience above normal temperatures.
|The 6-10 day outlook for temperatures spanning the time from January 26-30, 2014. The probabilities are for above and below normal temperatures. Click on the image for a larger view. Image Credit: NOAA\CPC.|
This may be the pattern through the end of January, but all indications are that the pattern will change in early February. The upper air pattern will flatten and the cold air will retreat into the Arctic region. Thus, temperatures will moderate and it should be a nice beginning to the month.
The pattern of amplifying and de-amplifying has brought wild swings of temperatures to Alaska and the Southeast. I see no reason to believe that the pattern will not continue through much of February. The outlook is calling for drier than normal conditions for February. However, the bulk of precipitation so far this winter has tended to come all-at-once with extended dry periods in between. All it will take is the right timing and we will see snow.