Thursday, March 21st 2013, 11:09 AM EDT
The latest indications are that the weather pattern will continue to favor colder storms that bring snow, in part, from the Central states to the East into early April.
The pattern may translate to a longer heating season, higher heating bills and more time, money and effort into snow removal later into the season than usual in some communities. The pattern can also negatively influence some spring weather-related activities.
The long-range weather patterns from the Central states to the Appalachians and even the East Coast point toward additional storms and just enough cold air when they come calling to bring more snow and a wintry mix, despite the official arrival of spring on Wed., March 20.
According to Paul Pastelok, head of the AccuWeather.com Long-Range Team, "The pattern favors ongoing 'blocking' over much of the Northern Hemisphere."
Pastelok's reference to "blocking" is referring to strong winds high in the atmosphere, known as the jet stream, taking on large southward dips and northward bulges. The jet stream guides weather systems along.
Where the southward dips set up, the weather pattern at the surface is often colder than normal. A blocking pattern can keep some areas cold for extended periods of time. The same pattern can keep some areas warmer than normal.
This is an illustration of what the jet stream pattern can look like in the Western Hemisphere, when there are no large blocks present.
"It appears these southward dips will tend to hang out in the Eastern states and part of the Central states moving forward into the first part of April," Pastelok said.
The same pattern also favors colder storms with more snow over a larger area or longer-lasting wintry mix than you might expect for the date.
As AccuWeather.com meteorologists see it now, the next large, cold storm with snow and other wintry precipitation may roll slowly through the Plains, Midwest and East later during the Palm Sunday weekend into early the following week (thereabouts March 23-26).
Another large storm is possible about a week later during part of the Easter Weekend (March 30-April 1).
However, the exact strength, track and timing of the storms is uncertain at this early stage. Both bear watching for those who have to travel or have outdoor plans.
There are also several smaller systems of concern that will be addressed on an as-need basis and within your local AccuWeather.com forecast.
Because of the time of the year, strong sunshine will negate some of the cold on sunny days. And when the pattern shifts slightly in between storms, warmth can make a brief comeback.
At the same time, the time of the year and blocking pattern can bring some very wild swings in the weather from day to day. It can be sunny and warm one day then a heavy, wet snowstorm the next.
One remote possibility is the places that receive heavy wet snow from one storm could be followed by a heavy rain event after the snow event. This increases the potential for flooding.
Unfortunately, these issues cannot be addressed until within a few days of the event. The weather (heavy snow versus rain) during storms of this nature can vary tremendously in distances of 50 miles or so.
"It is possible that we are seeing lingering effects of two stratospheric warming events that took place in January," Pastelok said.
The stratosphere mirrors the lower atmosphere (in reverse). Waves of cold air followed the two events over parts of North America and were forecast by AccuWeather.com in advance.
Prior to that, the pattern was very similar to the prior winter with well-above-average warmth much of the time.
Those who claimed that this winter would be exactly like last winter from the Mississippi Valley to much of the East were wrong.
The weather pattern started out similar to last year, but changed dramatically over the course of the winter and those effects will linger into the spring.
Even in the narrow swath from Washington, D.C. to Philadelphia, where snowfall has been lacking despite the different pattern, the risk of snow continues this spring. Last spring at the same time temperatures were frequently hitting the 60s and 70s.
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