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| Decaying remnants of a thunderstorm that came off the northern Green Mountains created this pretty sky over Burlington, Vermont last evening. Some areas did manage to see some good boomers y'day. Meanwhile, severe weather tomorrow? |
We have more weather we really need to pay attention to today and especially Monday. More on that after we get through the sometimes surprising weather we had yesterday.
First, the heat.
For the third day in a row, Burlington, Montpelier and St. Johnsbury reported record high temperatures.
St. Johnsbury was notable because they reached 90 degrees for the second day in a row, so they were pretty much the hot spot in Vermont during this.
Burlington reached 88 degrees, besting the old record of 86 in 1961.
I'm pretty sure this was the first time since September, 2017 that Burlington had record highs on three consecutive days. So it's a pretty rare event.
Then there were the thunderstorms. We knew a few would form over the mountains, but they became fairly widespread toward evening, more so than many forecasters thought.
Thunderstorms need some sort of updraft to get them going. Lose the updraft, lose the thunderstorm. A cold front, low pressure or even a weak trough of low pressure will sustain thunderstorms for a few hours. That's why we have lines of thunderstorms coming through Vermont fairly regularly during the warm season.
We'll have that on Monday, in fact, which I'll get to in a moment.
On Saturday, the only updrafts to generate thunderstorms were light winds that were forced to rise up the slopes of the Green Mountains and Adirondacks.
Those updrafts generated thunderstorms. But then, each thunderstorm would move away from that mountain, and the updraft the storm fed on would disappear. So the thunderstorm would collapse, bringing a rush of cool air to the surface as they did so.
That rush of cool air acted like a snowplow pushing a foot of fluff off your driveway back in February. That snowplow effect would generate updraft and another thunderstorm. Then that storm would collapse, generating yet another thunderstorm and so on.
Each thunderstorm had a brief life, and not all of them generated new ones. I saw one storm on radar that looked like it had a really heavy downpour form in eastern part of the town of Huntington, move into part of Hinesburg and then dissipate before reaching Route 7 in Shelburne. The entire lifespan of this storm was less than 45 minutes.
The very light air flow was from the southeast on Saturday, so the storms that did generate moved in the opposite direction most summer thunderstorms do. They usually approach us from the west. Saturday's storms came at us from the southeast.
A small minority Saturday's thunderstorms were borderline severe. The biggest one came off the Green Mountains into Rutland, dumping torrential downpours and hail the size of dimes or even pennies.
One unofficial report out of Rutland Town indicated 3.3 inches of rain with that storm including 2.2 inches in 45 minutes. Another 1.1 inches of rain was reported in the spot this morning.
Another report indicated Rutland had up to 1.5 inches of rain in just one hour. Small hail was also reported up in Highgate.
As is usual with storms, some places missed out altogether. Burlington reported a rumble of thunder, but not a drop of rain Saturday. Those of us who did get the rain were grateful, as we needed it.
But be careful what you wish for.....
STORMS, SOME SEVERE LOOM
This morning dawned overcast and humid as the remnants of a pesky storm that had been hanging around the Mid-Atlantic States for a week finally breaks up and comes through New England today.
We'll have scattered showers and storms, all hit and miss today.
Interestingly, because today's storms will be slow movers, NOAA's Weather Prediction Center has put the northern half of Vermont under a marginal (read low but not zero) risk of flash flooding. However, it's been dry, as you know so stream flows are low. Any high water, ponding on roads or dirt road erosion today will be isolated.
Monday's really the day we have to watch out for.
The potential set up is there for possible severe storms in and near Vermont Monday afternoon and evening.
A vigorous cold front will be approaching, and this disturbance will be tilted in a northwest to southeast orientation, which can increase the chance of severe thunderstorms. The air will be moist, and if we can get some morning sun, that will destabilize the atmosphere further.
Vermont remains in the slight risk category for severe storms, level two out of five in the risk ranking. An enhanced risk, which is level three out of five, looms just barely to our west in the latest update from NOAA's Storm Prediction Center.
The biggest threat from these storms will be intense straight line winds in a few spot. This, of course means damage to trees, power lines, even structures. Take any thunderstorm alerts and warnings seriously tomorrow, and get inside a sturdy building if a storm is approaching. Monday is NOT the day to go on a hike or take an excursion out on the lake.
Some of these storms could also have some large, damaging hail. There's even a very low, but again not zero chance of a quick spin up tornado, because there will be changes in wind direction and speed with height as these storms come through. That situation can get a storm to start rotating.
The storms should depart to the east of Vermont by late evening Monday. We then get into a few days of seasonable May weather for the rest of the week.
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