Snow in April?
Well, yes, and – bizarre as it may seem – it’s not all that unusual.
Meteorologists say Wednesday and Thursday’s mix of hail, snow and rain – interspersed in some areas with a pyrotechnic display of thunder and lightning – was classic Puget Sound area convergence zone behavior.
Our convergence zone, on the leeward side of the Olympic Mountains, is formed when wind blowing from the Pacific Ocean hits the Olympics and is diverted around them, like water flowing around a rock in a stream.
When the winds converge over the Puget Sound area, the Cascades block them and they have nowhere to go but up.
The updrafts create instability and cooling, and when temperatures are near freezing anyway, the result often is sudden bursts of hail, snow and that slushy mix in between.
Convergence zone or no, the weather for the past few days still has been unusual for this time of year.
“We had a very cold upper level trough move over us, and it brought the snow levels down very, very low for April,” Dennis D’Amico, meteorologist at the National Weather Service in Seattle, said Thursday.
“It’s certainly been a wet and cold start to this month,” D’Amico said. “We’re about five to 10 degrees below normal (about 49 degrees), and we’ve been wet so far.”
Precipitation at Sea-Tac Airport, for example, is already is about 2.25 inches, well above normal 0.6 inch.
And more rain is predicted this weekend. The Weather Service on Thursday forecast a 30 percent chance of rain Saturday with the odds going up Saturday night and through Sunday.
Snowfall in the mountains has been heavier than usual, too. In the past weeks, two to four feet of snow has fallen on the Western Cascades.
The Olympics and the east side of the Cascades has picked up 1 to 3 feet of snow in the past week, D’Amico said.
Rob Carson: 253-597-8693 firstname.lastname@example.org