Saturday's Storm Forecast Was A Bust; Heat Forecast Is The Real Deal

NOAA's Storm Prediction Center at midafternoon 
Saturday was contemplating issuing a severe thunderstorm
watch for northern New England. They ultimately
decided not to, which was smart, since
turned out widely expected severe thunderstorms
failed to materialize. The storm initiation that
the SPC expected in this map also didn't form.

Saturday was surely a lot quieter than expected.

Severe thunderstorms that were widely forecast to develop across northern Vermont failed to materialize, as we now know. 

I suppose if there's a botched forecast it's good that we didn't have damaging storms, instead of the other way around.  It would have been worse had un-forecasted storms materialized.

One forecast I'm much more confident will come true - and is coming true as we move into this Sunday afternoon - is a real early season hot spell in the Green Mountain State.

But first, let's get into what went wrong with Saturday's forecast for storms.

On paper, everything looked set for scattered severe storms from mid-afternoon into the evening Saturday.  Temperatures were rapidly rising into the 80s across Vermont by late morning. Montpelier managed to tie a record high of 85 degrees for the date.

Weather disturbances were marching across Ontario toward Quebec to help pull the trigger on the storms that would then move southward into Vermont, New Hampshire and Maine. 

Pretty much all the weather models were on board with this. Remember the other day when I said weather models had gotten a lot better than they used to be on forecasting small scale features, like thunderstorms in a narrow area?

That's true, but they still have their shortcomings.  The models didn't handle Saturday's situation well at all. 

Before noon, a band of clouds and light showers formed in New York's St. Lawrence Valley.  They blotted out the sun in northwestern Vermont by noon, and dropped some sprinkles. This light band of showers blossomed into a line of moderate thunderstorms on a line from just south of Burlington to St. Johnsbury, then continued to march east into New Hampshire. 

This band of lighter activity was not forecast to develop, and even as it did, wasn't expected to hold together all the way southeast to the Massachusetts coast.

This initial band was not at all forecasted.  Instead of continued sun the band stabilized the atmosphere, helping to prevent the kinds of towering clouds you get as thunderstorms develop. This band also left behind a whole bunch of what I would call debris clouds. That meant the sun really couldn't come back out and start to churn the atmosphere and make it unstable again.  

WMUR meteorologist Eric Weglarz noticed a boundary running across
northern Vermont and New Hampshire Saturday evening
that under many circumstances would have triggered some
hefty storms, but not all the ingredients were there to 
set them off, so no severe weather occured.

The forecasted disturbances did make it into southern Quebec in the late afternoon and evening. Thunderstorms, some severe, blossomed in the Montreal area and started heading southeast. 

One cell had together for hours and ended up crossing the border near Newport, Vermont. But the relatively stable air prevented this storm from growing into something severe. 

Even during the time of day when the storms were forecast to blow up and failed to do so, most of the ingredients were there. 

The weather disturbances were trying to add lift to the atmosphere. There was a subtle but sharp temperature boundary last evening running from about Ottawa to Burlington to northern New Hampshire near Conway. 

This was a recipe for strong to severe storms, but that instability wasn't enough to create chaos.  You could tell we were almost there.  Last evening, small downpours appeared seemingly out of nowhere north of Route 2.  

An example was around my place in St. Albans. One swing of the radar showed almost nothing around us. A couple minutes later, we had a brief downpour.  Another look at the radar just a few minutes after my previous peek showed a brand new cell zipping rapidly away from St. Albans and heading east. The Northeast Kingdom was also suddenly pockmarked by little downpours. 

At the time these little downpours were popping up, the sun was setting.  The sun wasn't going to add any energy to an otherwise volatile atmosphere. The severe threat was over. 

HOT WEATHER

The forecast for today and tomorrow is a lot more straight forward and less prone to complications and mishaps.

The atmosphere today is just a tiny bit warmer than yesterday, but there's a lot more sunshine.  That is allowing today's temperatures to go well above those on Saturday. 

It was already 87 degrees at noon in Burlington, so we're almost a shoo-in for reaching 90 degrees.  That's despite the fact that there will be more clouds mixing with the hazy blue skies as the afternoon wears on. 

There are no strange and risky weather disturbances to trigger widespread thunderstorms. But lake breezes along Lake Champlain, updrafts that mountains are helping to create, and just some residual general instability will probably trigger a few widely scattered showers and storms later this afternoon and evening. 

It'll be very hit and miss, with most of us probably not getting any rain. If thunderstorms do develop later today, they won't be severe. 

Monday will be the hottest day of the hot spell, and if more record highs are set, Monday will be the most likely day.  The record high in Burlington tomorrow is 94 degrees and Montpelier's record is 89.  Both are definitely in jeopardy. 

A cold front from Quebec will be approaching us Tuesday, so temperatures might be a couple degrees cooler, especially north and east of Interstate 89. But it will still be hot and humid. 

The cold front is expected to fully come through Wednesday.  If the front is a bit slower than forecast, we'll endure more warmth and humidity, along with the risk of storms.  If the front is faster, it'll get more comfortable, especially later in the day, and there would be fewer showers and storms. We'll see.