Hot Times To Come To An End With Drenching Storms

 Last night was really as oppressive as you can get in Vermont, especially in the Champlain Valley.

This is the National Weather Service in South Burlington's 
idea of where the heaviest rain will fall later today and
tonight. More than an inch is in the forecast west of the
Green Mountains. Note that actual rain totals will
differ from what's shown here. It all depends on where
the heaviest showers and storms set up.

It never got below the mid-70s in Burlington.  The record for the "highest" low temperature for the date is 71 degrees, set in 1973. 

 I don't think we'll set a new record today, though, as I expect showers and storms will cool Burlington off below that 71 degree mark by midnight tonight. 

But I'm getting ahead of myself just a bit here. 

First, we have to survive another day of warm, and very humid weather. Dew points will be within a few degrees either side of 70 degrees, so it will be another sweaty day. Before showers and thunderstorms arrive, actual temperatures will probably soar well into the 80s again. 

That sets the stage for a rather stormy late afternoon and night in Vermont.  We're still watching that juicy, slow moving cold front approach us. That front created storms that actually prompted a tornado warning north of Watertown, New York last evening, but those storms quickly diminished to sprinkles by the time they reached Vermont. 

It'll be a different story today.  No tornadoes, but a few storms could get pretty rambunctious and some will have drenching downpours, sort of like what hit Burlington, Vermont last Friday. 

Most of us won't have severe storms, but a few isolated ones this afternoon and evening could create what are know as wet microbursts. 

The term "wet microburst" sounds like a harmless, tiny water balloon popping, but these microbursts can be dangerous. 

A bit of dry air can get entrained into a thunderstorm, which causes a little evaporation and cooling. That causes air to sink. Meanwhile, the thunderstorm is absolutely loaded with rain drops. Those drops are heavy. So everything ends up falling at once. A big packet of wind and rain drops vertically to the ground, then spreads out when it hits the ground.

Wind speeds in microbursts can easily exceed 60 mph and the torrents of rain can cause a local flash flood. These things can cause a lot of damage in a small area.

Luckily, there won't be too many of these with this cold front in Vermont later today. 

Still, many of us will experience lightning, gusty winds and especially some heavy downpours. After sunset, there won't be any severe thunderstorms, but the threat of torrential downpours continues. We'll have the usual threat of local street flooding and minor washouts, but nothing horrific. 

For most of us, this is a good thing. We need the rain. Especially since after this episode, we've got a long spell of dry weather coming up. 

The best rainfall will probably be west of the Green Mountains, which is actually too bad, since southeastern Vermont needs the rain the most.  Rainfall will be incredibly variable with winners and losers. But generally west of the Greens, most places can at least hope for an inch or more of rain. Parched southeastern Vermont, which is officially in drought conditions,  could get as little as a quarter inch. 

Rain will be pretty much over by tomorrow morning, except maybe in the Northeast Kingdom. It will be somewhat cooler, and definitely less humid on Wednesday as well.

A second cold front arrives Wednesday afternoon with a few scattered showers and garden variety thunderstorms. After that goes by, you'll really notice the change. It will be decidedly cooler. 

Thursday will probably be the coldest day since mid June or so. That's a relative term, of course. We can expect highs on Thursday to be in the 65 to 70 degree range.  That's cooler than normal for this time of year, but nowhere near as chilly as it can get in the opening days of September. 

Likewise, temperatures early Friday morning will be in the 40s for most of us. Again, cool, but nothing unusual. 

Temperatures will pop back up to a little above normal by Saturday, but nothing like we saw the past few days. Another cold front will bring us back down to the pleasant low 70s by Sunday and Monday. 

It'll probably be warmer than average most of the time, though through mid-September. But this being the end of summer, we'll see some cool shots of air mixed in there as well. The heat of summer is almost over.