Weather or not

Stationary front.

Those are two ugly words in the spring, tending to send shivers down the backs of New Englanders. They’re cold. They’re gray. They’re wet. They don’t like to move much. They leave us stuck in below-average temperatures and crank out one showery day after another. They leave us cranky. Like this week.

Think of a stationary front as two living air masses that are tired and need a rest. Normally, cold air and warm air push each other around the country, around the world, diving south, sprinting north, sashaying east and west. Sometimes the warm air is on the offensive (a warm front); sometimes the cold air takes the lead (a cold front); sometimes one overruns the other.

But sometimes, they just plain stop (a stationary front). It’s as though they’ve called a truce and are content to not move for a while. Their “neutral” zone can be 2 miles wide or 200 miles wide, and pity the land masses under and around them. Even though the front may not move for days, the clashing air masses still generate foul weather, and that’s what’s been happening this week.

A natural convergence zone for storm systems, New England generally gets stuck in the northern sectors of stationary fronts in springtime. Chilly temperatures with intermittent rain and drizzle are the trademarks; every so often, a wave of energy will ripple along the fronts and produce periods of heavier showers.

The stationary front dogging us this week has a particularly sharp temperature contrast. While we wallow in the 40s, it’s been pushing 70 as close as New York City and 90 in Maryland. Saturday, the front will wobble north of us and drag some of that warm air into the state, but don’t be fooled. By Sunday it will sag back down and attract an area of low pressure, a trigger for more rain.

Zooming out, the front is thousands of miles long and formed the shape of a backward “7” this week. The longer stem jutted up from the southern states, bisected the middle of the country and jogged east around Ohio. With humid, unstable air feeding it in the South, numerous severe storms and tornadoes were unleashed, making headlines for much of the week in tornado-prone Texas and Oklahoma. Now, it’s in more of a diagonal line from New Mexico to New England.

Next week the air masses are expected to start pushing each other around again, leaving us with a mixed bag. We may warm up early in the week, with temperatures nudging 70, but we could drop back into the low 50s with more rain the second half of next week. But in weather, atmospheric conditions can change quickly.

Of course, as spring progresses and summer nears, the possibility of cut-off lows increases — another producer of chilly rain for days on end.