Yesterday was the Ides of February (Feb. 15). That means that meteorological winter will be over in less than two weeks. Astronomical winter has a bit more than a month to go. Winter officially ends (and Spring begins) on Mar. 20, 2014.
Given that winter 2013-2014 has been so cold and snowy across much of the eastern U.S. (compared to recent years), and the western U.S, has been so dry (Fig. 1), the end of winter can’t come soon enough. Folks east of the Rockies want the “polar vortex,” also known historically as the Hudson Bay low, to leave; folks in the West want the persistent upper level ridge to vanish (Fig. 2).
However, weather and nature do not always adhere to human-made calendars. They certainly don’t follow human wishes.
There is some good news on the horizon. The deep upper level low and trough in the east will relax their grip during the upcoming week (Fig. 3). Upper level winds will become more “zonal,” meaning they’ll be blowing across the U.S. mainly from west to east. This is much different than the persistent upper level wind flow pattern that has dominated the U.S. almost all winter. Still, periodic disturbances moving through the area may bring brief periods of rain and/or snow depending upon temperatures at the time of the precipitation.
Because the warm-up will not be as dramatic as it appeared the other day, snow melt will be a bit more subdued, lessening flooding risk, at least a little. Due to extensive snowpack and the amount of liquid water content in the snow (Fig. 4), flooding potential is on the mind of many meteorologists and hydrologists as Spring approaches.
Unfortunately, this “January Thaw” look-alike, actually arriving in mid-February, will be relatively short-lived. The Hudson Bay low is expected to reform by early in the week of Feb. 23 (Fig. 5) and bring more cold and snow to the Great Lakes, Ohio Valley and Northeast. It isn’t until March arrives that another temperature rebound can be expected in the eastern U.S.
Out west, the overall pattern will not change much. The upper level ridge will flatten, allowing storms to continue their periodic attack on the Pacific Northwest inland to Idaho and Montana. Moisture, however, will not reach into California, Arizona, New Mexico and much of Texas. This means the western drought (now covering most places southwest of a Portland, OR – Minneapolis, MN – New Orleans, LA line) will continue unabated.
Even as March unfolds (and computer models suggest a grander weather pattern shift), does a significant storm system seem poised to develop over the southern Rockies (Fig. 6). This portends the potential for a Colorado and High Plains snowstorm and a potential severe storm outbreak across eastern Texas and Oklahoma.
This type of longer-term outlook (two weeks into the future) is always subject to updates and possible major changes. That’s because of the inherent uncertainly in modeling atmospheric conditions beyond about 7 days.
So, be sure to check back for updates here as the calendar marchs toward March.
© 2014 H. Michael Mogil