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Western PA/Pittsburgh Fall Weather Discussion


Ahoff
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That was an unexpected event.  A tornado outbreak in late October isn't exactly typical.  Seems we had some extra shear and helicity that was not predicted?  Recency bias at work, but we appear to avoid the severe weather when there are actual watches in place.  Stuff goes off when there's no expectation.

I have friends near the Ross Park Mall and it looks like the rotation must have gone right over them.  If there was a funnel, luckily it hadn't touched down (yet).

There were also a couple other events to my south.  Not sure what happened near McMurray whether it was a brief touchdown or a microburst.  Definitely a tornado west of Washington.

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I read the SPC discussion around 6:30 while the warnings were still in Ohio and the SPC meso discussion said sundown would mean weakening.  Lots of shear because of how the cold front was filling in after the earlier warm sector, occluding just up in Canada.  Really surprised they didn't even issue a watch after there were warnings all across the line in Ohio.

radsfcus_exp_new18.gif

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I read the SPC discussion around 6:30 while the warnings were still in Ohio and the SPC meso discussion said sundown would mean weakening.  Lots of shear because of how the cold front was filling in after the earlier warm sector, occluding just up in Canada.  Really surprised they didn't even issue a watch after there were warnings all across the line in Ohio.
radsfcus_exp_new18.gif.d3e9dacb72df6b56ec4931eb42f5d0b7.gif

Interesting that they would mention weakening after sunset. I mean that is how it usually goes, but instability was never really a factor yesterday anyway. It was all about the wind shear. I’m sure the sunset could have caused slight weakening, but the main fuel for those storms was the shear


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It’s looking very possible that our low of 37 the other day could be our only low in the 30s as we enter November. There have been 9 times in recorded history that the temperature hasn’t gotten to 36 or lower by the end of October, and only two at KPIT. Latest first 36 is 11/9/1902. The latest in the KPIT era? 11/5/1950. Let’s hope this winter is at least a little like that one.

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2 hours ago, TimB84 said:

It’s looking very possible that our low of 37 the other day could be our only low in the 30s as we enter November. There have been 9 times in recorded history that the temperature hasn’t gotten to 36 or lower by the end of October, and only two at KPIT. Latest first 36 is 11/9/1902. The latest in the KPIT era? 11/5/1950. Let’s hope this winter is at least a little like that one.

Didn’t we get three feet of snow around thanksgiving that year? 

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On 10/22/2021 at 10:54 PM, MikeB_01 said:

Interesting that they would mention weakening after sunset. I mean that is how it usually goes, but instability was never really a factor yesterday anyway. It was all about the wind shear. I’m sure the sunset could have caused slight weakening, but the main fuel for those storms was the shear

Reading the NWSChat report (https://nwschat.weather.gov/p.php?pid=202110232359-KPBZ-NOUS41-PNSPBZ) really sounds like no one would have thought a tornado outbreak would be probable here.  If the SPC dismissed any probability of a tornado outbreak in our area in October then those heuristics (bias, really) definitely influenced the decision to not issue a watch.  Hopefully they will incorporate this in future decisions because the aforementioned discussion also states that our area has seen more and more tornado warnings since 2017.

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2 hours ago, dj3 said:

GFS has been hinting at an early window of opportunity around the first weekend of November. Euro also has some flakes at the end of the run I believe. Just as long as it doesn't play out like this...

1636200000-KgK9RWBEfs0.png

Oh God!  Let the worrying begin, lol.  'Tis the season!  Let's move it west some and lock it in.

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1 hour ago, Ahoff said:

Is there a reason that there are frost and freeze warnings all the way to the Atlantic coast and down to TN.  But not here?  Forecast is for 31 from the NWS.

Did we already have one that I missed?

Quoting this in the fall thread:

No, the NWS posted yesterday that the growing season is over and they will no longer be issuing them this year.

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12 hours ago, TimB84 said:

Quoting this in the fall thread:

No, the NWS posted yesterday that the growing season is over and they will no longer be issuing them this year.

Oops, somehow, I totally ended up in the wrong thread.

Anyway, weird, considering it only went down below freezing for the first time this morning.

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4 hours ago, Ahoff said:

Oops, somehow, I totally ended up in the wrong thread.

Anyway, weird, considering it only went down below freezing for the first time this morning.

I mean, you’d have to be insane to be trying to grow anything sensitive into November, but I do know what you mean. That said, the 29 appears to be exactly on schedule for first 20s at PIT (Nov. 3 is the average date).

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39 minutes ago, TimB84 said:

I mean, you’d have to be insane to be trying to grow anything sensitive into November, but I do know what you mean. That said, the 29 appears to be exactly on schedule for first 20s at PIT (Nov. 3 is the average date).

Well, yeah, most around here are done growing by November, but technically speaking it's odd considering they have records for growing season length.  I mean if they're going to arbitrarily call and end to the season for no weather related reason, why even track it?

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7 hours ago, Ahoff said:

Forecast is 46 or 47, so we'll see.

Just kidding anyway. Official NWS normals have the normal high/low/mean at 56/38/46. Not sure how that happens, as even (55.5+37.5)/2 = 46.5, which rounds up. So 48/26=37 gives us a -9 according to the official NWS report. So we’re at 134 days and counting without a negative double digit departure, and in the same timespan we’ve had 13 positive double digit departures (despite the normals rising decisively this year), and we likely won’t have one over the next 10 days or so at least.

Edit: I looked at the official normals for today, it’s 55.6 and 37.5. (55.6+37.5)/2 = 46.55, which I would still round to 47 and not 46.

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Earliest date with 4 consecutive lows in the 20s:

1. 10/26-29/1976 (4 days)

2. 11/1-5/1879 (5 days)

3. 11/1-4/1954 (4 days)

T-4. 11/3-6/2021 (4 days), 11/3-6/1951 (4 days), 11/3-6/1991 (4 days), 11/3-7/1966 (5 days)
 

This is rarer than I would have thought.

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12 minutes ago, TimB84 said:

Earliest date with 4 consecutive lows in the 20s:

1. 10/26-29/1976 (4 days)

2. 11/1-5/1879 (5 days)

3. 11/1-4/1954 (4 days)

T-4. 11/3-6/2021 (4 days), 11/3-6/1951 (4 days), 11/3-6/1991 (4 days), 11/3-7/1966 (5 days)
 

This is rarer than I would have thought.

That's interesting.

Wonder if it will be the earliest 5 days in a row?  Looks like we have a chance at around 28 again tomorrow morning.

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