jwilson

Another "slight" risk of severe today and it looks like, once again, Pittsburgh metro and points north will miss out.

Depends on your perspective, of course, but it seems like the metro area has been having some bad luck lately on the stormy weather.  Everything seems to be missing south or farther north.

At this time of year, if anything over a trace would be historic, a 9" snowfall would be biblical, and I'd consider Armageddon right around the corner.

We've had a trace of snow in May twice since 2000 ('01-'02 & '15-'16).. let's go for a third.

If it wasn't for today, we would have had a higher max temp in January (71) this year than in April (70 was previous max).  Oof.

Well that was an intense line, definitely one of the most dynamic cells I've witnessed since living here.  Tornado warning popped on the TV, but it wasn't really for us.  Hope you're all good up in New Kensington.  Twitter report said there was a tornado near Markle.

I was watching power flashes in the distance from my viewpoint.  Actually a lot of other strange lighting colors during the storm, as well.

We got a very brief and minor bout of hail yesterday with that "supercell," but it seemed the actual hail core went south of us, closer to Canonsburg.  Our hail was minuscule in comparison (pea size at the most).

When I get older, I'm retiring to Mammoth Lakes or Lake Tahoe.  200" of snow per year.  Ideally I'll have a place I can ski/snowboard right out to the slopes.

26 minutes ago, KPITSnow said:

Way late on this one, but at least with that we had an epic 2nd half of the winter. Recently when we get screwed over we follow it up with nothing. 
 

we haven’t even had storms to track this year outside of fantasy storms 2 weeks out 

For 2009, even I got screwed a tad on that one being in the Philly suburbs.  Philly measured 23" and I got 12" - that entire winter was full of tight gradient snow storms.

I think my 3.2" is a final.  We've been getting showery snows for a while now but nothing is adding up.

I measured 1.7" at 5:30 AM and 2.8" at 7:30 AM.  Center cut Allegheny got stuck under subsidence/divergence earlier and that limited our totals.  Likewise, a lot of our snow was very fine flakes.  I think one of the things the models didn't handle well was snow growth.  Perhaps that was due to wind shear in the upper levels?  I'm not well versed in the DGZ.

This one hit the target; not an overperformer nor did it disappoint, necessarily.  If we had some blocking it could have been amazing.  To get anything in this winter is luck, though.  A shame we don't see these inland low tracks more often.  Still waiting for that widespread overrunning event that gets everyone.

Changeover occurred between 330 and 4 AM.  Have what looks to be an inch or so thus far, boundary might be setting up east, but the snow side of this system looks more robust (for now) than expected.  We'll see when bombogensis occurs how frontogenic forcing interplays with the current shield.

SREF plumes are up to a mean of over 4" now, compared to 2.5" earlier.

Meanwhile, the HRDPS is a pretty good hit for us (6-10"), though the model name always makes me think it's derpy.  Not sure it's all that valuable, just another possible solution.

11 minutes ago, RitualOfTheTrout said:

Yeah, all guidance is agreeing on a general 3-5 inches. You probably have to cut that to account for initial melting but not bad to see something improve as we get closer. Not saying it will happen, but the storms that are the most likely to bust high are ones that keep getting better as we close in.

The dynamics involved mean this storm has high bust potential either direction.  The heaviest band has swung from the west back to the east of us today.

GEFS mean at 12Z was 5" for PIT.  That's robust.  Hard to trust it, though.  We should have some white rain, but I don't know for how long.  SREF mean is 2.5".

4 minutes ago, Ahoff said:

So, what time is that heaviest band looking to come through, at least right now?  After 7am, I hope?

High-res NAM has changeover around 2-3 AM.  GFS is slower, closer to 6-7 AM.  Canadian agrees.  Bunch of mesoscale models are 4-5 AM, including SREFS, HRRR, ARW.  RGEM has the bulk of snow over by 8 AM.  In other words, there's a spread, but I would be more inclined to trust the faster solutions.  Chances favor the snow rates are at or past peak at 7 AM.  Messy commute.

Based on the 12Z suite, I'd say the odds *look* decent for at least a 2" event in the metro area, which would probably be the biggest storm for most - if not all - of us.  I'm only at ~6" on the season versus the NWS measurement.

For right now, the NWS has PIT at a 74% chance of 2" or more.  44% chance at 4" or more.  1% chance at >12" (lol).  Given the intense convection and fast storm movement we'll see, there's also a high bust potential for those areas that fall outside of the best convective bands (or get stuck under divergence).

It will likely come down to a nowcast event.  Reminds me of tracking Miller B's off the coast.  A lot of times you'd have wildly different snow totals just a few miles apart because of the convergence/divergence and banding.

Just now, Rd9108 said:

NAM further NW and jackpots the usual Youngstown area. 

Was just about to say the NAM finds a new way to screw us by pulling the low too far west.  It trains the good snow to our west and northwest while dryslotting AGH (and points SE) for a while.  Its totals are overdone, but that general idea is trouble.

It is looking to me like an interior New England special.

GFS & NAM are pretty bearish on this, only a couple inches, at most.  NAM looks oddly dry, actually, until the low gets cranking in the Atlantic.  The Canadian is a bit more bullish, ranging from 3-6" across Allegheny (West to East, respectively).  The Canadian has been better this winter than the GFS so there's a little bit of optimism for you.

We're relying on storm dynamics to bring us snow, requiring decent rates in a fast-moving LP to overcome antecedent warmth.  Not that it can't work, but we might have a period of white rain which limits accumulations.

If Wichita Falls, TX is getting a bigger snow than we've seen in years, you know there's something funky going on in weather town.

4 hours ago, Ahoff said:

Why is it almost guaranteed?  Is there something that hints at it not changing, except for prior history?

It's part of a decadal trend, but there's an overall larger trend for the NAO to be positive during the winter months starting back in the 1980s.  The NAO between 1950 and 1980 averaged overwhelmingly negative versus the average since then which has been quite the opposite.

If we break that down a little further, we can see that during the 80s, the NAO spiked upward.  It did begin a downward trend in the 90s which stopped right around 2010 (give or take a couple years), but it still remained positive, overall.  Since then, the NAO has spiked hard positive again.  I think there's an argument the trend should stop soon and start declining again.  Similar to how it operated in the 90s.  That wouldn't necessarily be good news for snow lovers.

Now there's some debate, I suppose, about why this has occurred.  I don't know if data collection and analysis is better now (perhaps the older measurements were flawed or imprecise relative to modern times).  Is it climate change?  Is it short-term variability?  I don't know that anyone is certain on the answer.  I'm not an expert, either.

Here is one relevant portion from a research paper on the NAO and its influence on warming:

Quote

The impact of the summer NAO is much weaker, but still discernible over Europe, North America and Greenland, with the downward trend in the summer NAO from 1988–2012 reducing warming by about a third in Northern Europe and a half in North America.

Basically, the -NAO during summer months has had a negative effect on the warmth of that season over this period.  It has only continued since the time frame included in this particular study.  Not to say a +NAO can't happen during the summer, because it can, but that hasn't been the norm or average in recent history.

Here we can more clearly see the trend of the NAO downward over the summer months (JJA) since the 90s.

There's a bit more from that paper:

Quote

A positive phase of the NAO in winter is associated with . . . [a] weak warming signal [that] can be seen over the United States and cooling over the Mediterranean and Middle East, associated with stronger clockwise flow around the subtropical Atlantic high.  A negative NAO is associated with opposite pressure anomalies, leading to a more wavy jet stream and a weaker, more zonal storm track.

Prior to this decade, of course, the NAO attempted to exert a cooling influence on our winters, but the overall anomalies rose, anyway, in spite of it.  This is due to overall climate change and warming trends outside the influence of the NAO.  Since then, however, the NAO hasn't exerted the same cooling influence on our winters and we've mostly been going the other way.  It helps explain a little why this winter has been basically nonexistant; however, there's a lot of variables to consider.

Quote

From 1920–1971 there was a cooling trend over northern Eurasia and the eastern United States, with warming elsewhere. The NAO downtrend explains the Eurasian cooling, and part of the North American cooling . . . .

Ultimately, the NAO doesn't exert the same influence on summer temps for us as it does for winter temps, so I don't think it's a big reason for our milder summers, but it could still have some impact, especially if the values are strongly anomalous in one direction or the other.

The Giants will win the world series, undoubtedly.

Euro and ensembles hint at potential Saturday night along with GFS/Icon.  Canadian doesn't have the shortwave, more of a little northern stream clipper of sorts.

There's a bit of room to come north, which is a good thing, but perhaps the overall pattern hints at another failure in the works.  Retreating high.  Threat has moved around and we're still 4/5 days out.  Hard to get too excited, cap is probably 3" which is relatively small (but would be our biggest hit this winter if materialized).

5 hours ago, RitualOfTheTrout said:

I'm still holding out hope for a fluke storm, or maybe we get something bigger in March. At this point I'd be just as happy to see March torch in the mid 60s all month as I would getting a big storm. I just hope we don't get a raging -AO / -NAO and a cold rainy spring. A slightly moderated continuation of the past 50 days we be awful.

The -NAO through summer is almost a guarantee, at this point.  We've been stuck in this loop where the NAO tanks from April to October and is positive for the winter months.  I imagine that's part of the reason we haven't had a really hot summer in a while.  Then we get the heat into fall (September/October) when the pattern starts flipping.

Euro and GFS actually look similar for once (Thursday into Friday).  The Canadian is also somewhat similar, but it's a bit more strung out initially and then cranks the primary low later (Saturday).  It's all a very odd evolution.  It amounts to three straight days of rain (Tuesday through Thursday) and then snow on Friday, but obviously the location and strength of the primary/ULL would factor into how much snow we get, if any.  The GFS does go negative tilt. 

We're under 7 days which makes this "agreement" unusual for the winter, but given all the moving pieces, I'm not ready to buy in to any solution.  I have to think a more progressive storm is likely which would limit our accumulations to nothing, more or less.

I don't even know if it's worth mentioning because we're due to have the rug pulled out in another cycle or two, but there's nothing else to talk about.

On 1/27/2020 at 10:16 PM, jwilson said:

Long-term snowfall probabilities have us at essentially a 100% chance of more than three inches over the next couple weeks, but that doesn't mean a whole lot, really, considering the length of the term.

Yeah, remember that?  Well, it's down to 10% now.

EL OH EL