Spring is wearing a mask

It will feel more like March than May as we continue our march toward mid-May. We all know that some days in May can seem like March, just as some days in March can feel like May, if you will. Of course, we don't usually have fields of dandelions in March:

Actually, these were from April.

But these are authentic May dandelions!

In any case, with the coming chill, warm thoughts of summer will be hidden behind a mask:

Now, on to some maps. First is the Tuesday (5-5-20) afternoon satellite picture. With west-to-east flow, we can see that an area of cloudiness is heading toward the Northeast region (which for this set of feature stories extends from Maryland to Maine out to the Great Lakes and Upper Ohio Valley).

The surface weather map as forecast for 8 p.m. EDT:

The narrow red and blue dashed lines typically appear on all of these maps. They represent lines of equal thickness. When you consider a layer of air, we know that warm air expands and cold air contracts. This means we might be able to determine the snow-rain line from a thickness line. In this case, all the blue lines would, on average, indicate snow. The red lines, representing higher thicknesses and therefore more warmth, indicate rain. In this case, the snow-rain line would be between the southernmost blue line and the northernmost red line. This imaginary line extends from Toledo, Ohio, to Buffalo, New York, and over to near Providence, Rhode Island. As a predictive tool, this rain-snow line applies best when there is heavy precipitation. At this time of year, the air near the ground is warmer than it is in winter. So, even if it is cold aloft, it will typically not snow at the same places that it might in January; the actual snow-rain line will be farther north.

Two main low pressure area will move through the region between Wednesday and Saturday. The map above shows the first one causing rain from eastern Ohio to Maryland. The blue area represents wet snow at this time, probably not sticking on paved areas.

On Thursday, any early precipitation should move off the East Coast by midday. From Ohio to western New England, it will be chilly but dry. However, a weak but fast-developing low pressure could cause "surprise" snow for a while overnight:

Whether that happens or not, most of Friday should be chilly and dry.

However, notice the green area advancing from the lower Ohio Valley. See also where the snow-rain boundary could be: south of Pennsylvania. Now, as most low-pressure areas approach, some warming takes place. Looking at that for Friday evening...

...the snow-rain line has moved north, If the low-pressure center is in central Maryland, we would expect Philadelphia to get all rain while the mountains of southwestern and central Pennsylvania get up to several inches of snow. With many shrubs and trees in leaf, there is a greater risk for damage than when the branches are bare in midwinter.

At 2 a.m. EDT Saturday, we see the fast-moving storm has caused potentially accumulating snow from the middle of Pennsylvania through much of Massachusetts. Subfreezing air is advancing in behind the storm with wintry winds.

By Saturday at 2 p.m., the storm center is east o New England, and in the six hours leading up to then, accumulations have occurred from Vermont and New Hampshire through central and southern Maine, Blustery cold winds blowing across the eastern Great Lakes have caused widespread snow showers,

But remember. This was written Tuesday evening. I used past tense in describing some of the maps, yet in fact, none of this has happened yet.

There are still dandelions out in the field. Somehow that reality is somewhat comforting in this Covid Spring.

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