Friday, February 25, 2011
Weather columnist Kevin Myatt: Needed rain heralds day of springlike gusty wind
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Welcome to the topsy-turvy world of springlike weather, where something called warm air advection can bring a day of cold rain and a strong cold front can cause temperatures to rise above 60 degrees.
It's not spring on any calendar yet, but the storm system currently affecting our region and much of the eastern two-thirds of the nation is very springlike, with its severe weather in the Mississippi River Valley, heavy snow from the Upper Midwest to New England and lots of rain and wind through much of the rest of the East and South.
Today, the wind will kick up behind a strong cold front. It is a front of Pacific origin, not from the Arctic or Canada, so it will not lead to any massive chill, just a couple of mornings in the 30s this weekend, nothing unusual for late February. But highs today will likely climb above 60 degrees as westerly winds whip down the slopes of the Appalachians, causing some warming from downslope compression of air.
This will be a far cry from Thursday's slow climb through the 30s and 40s with a constant, but very needed, rain. That rain was a result of a warm, moist flow from the Gulf of Mexico overriding a cold dome of air near the surface, a process called warm air advection. Overnight, the warm air finally won the battle and pushed the cold air northward, enabling today's windy warmth to occur.
As the cold front pushes through today, a line of heavy showers is likely this morning, accompanied by the potential for strong downdraft winds.
Once the front passes, more constant wind will take hold, and gusts could top 50 mph at times. But unlike the past couple of windy days, the wildfire threat has largely been doused by the rain, which soaked potential surface fuels such as leaves and brush.
Rainfall amounts of 0.75 to 1.25 inch were common across the region by midevening Thursday, with more falling overnight into this morning. It is the biggest widespread rain since Nov. 30 and Dec. 1, and will keep Roanoke and Blacksburg from setting a new record for driest winter on record.
But without additional rains in the coming weeks, we'll be right back to brush fires and smoky air with a growing drought.
There is another chance of rain with a similar storm system Monday.
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