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Dec 5-6 Round Two? NAM brings "sling-shot" Upper Low into SW and the fun has just begun!

wxhstn74

By wxhstn74,
in Lakes/Ohio Valley

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an uncanny otter

an uncanny otter

Posted
Posted

What sucks is that we're kind of in a window of opportunity here with PNA becoming neutral and the EPO negative. I've been hearing rumblings (over in the NE subforum, although I haven't checked back in about 36 hours) that the EURO ensembles are showing a mid month +EPO/-PNA torch regime. With no help from the Atlantic, there may not be a next week for us. That's why it was sort of important to me to get something to come to fruition with one of these waves. Not impossible, but looking bleak.

Oh, I hear you. It would have been nice to get snow out of this (still not discounting the possibility completely but it's not looking promising) but it's rare to get good snows this far south in early December. Most of our big snowstorms in recent years don't come until the 10th at the earliest (2004, 2007, 2008 and 2010 come to mind)

Normally I wouldn't be concerned about missing this storm, but the fact that this was our "window of opportunity" isn't comforting. I took a quick look at Montreal's forecast for next week and it ain't much prettier than ours. :yikes:

It's comforting to know that it's the same crappy pattern for everybody here and in the NE though.

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Snowstorms

Snowstorms

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0z EURO was still showing a band of modest accumulating snow. I'm sure it'll be FTL.

I think the models are underestimating the cold air aloft with the first wave thus they make it seem as though the initial frontal passage is nothing but a nuisance.

As was the case with that last freezing rain storm where models had 2-4C upper air temps but in the end they stayed closer to 0C and freezing rain fell for 3-6hrs.

Lets see.

The GFS does have a warm bias.

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snowstormcanuck

snowstormcanuck

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I think the models are underestimating the cold air aloft with the first wave thus they make it seem as though the initial frontal passage is nothing but a nuisance.

As was the case with that last freezing rain storm where models had 2-4C upper air temps but in the end they stayed closer to 0C and freezing rain fell for 3-6hrs.

Lets see.

The GFS does have a warm bias.

Difference in my mind is that in that ZR storm we had a typical sprawling sfc high located in Quebec feeding low level cold, dry air into srn Ontario on NE winds. In this instance we're not going to get the benefit of evaporative cooling, even after the winds shift NE, as the column is already going to be nearly saturated.

I'm not expecting much from tomorrow, but as you say, let's see. :)

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Snowstorms

Snowstorms

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Difference in my mind is that in that ZR storm we had a typical sprawling sfc high located in Quebec feeding low level cold, dry air into srn Ontario on NE winds. In this instance we're not going to get the benefit of evaporative cooling, even after the winds shift NE, as the column is already going to be nearly saturated.

I'm not expecting much from tomorrow, but as you say, let's see. :)

We have a distant 1040hp anomaly across the West providing N/NE winds around that time frame.

Tonights 0z runs will be important IMO.

In the case with the secondary wave, I think the models aren't handling it properly. No extreme West based blocking to push that storm OTS. The decent HP anomalies across the West should stay across the West providing a nice cool down initially ahead of the system and we have a ULL sitting across the Hudson.

The GFS and even the Euro have been known to kill these waves completely.

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snowstormcanuck

snowstormcanuck

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Well, looking more and more like this storm will be a dud for snow for just about anyone. Wouldnt worry about a "window of opportunity" passing though. The damn models have been all over the place and change every 6 hours.

Again, I'm hearing this second hand, but the EURO ensembles haven't been erratic. They've been pretty steadfast about brining back the GOA low around D10. I'm not saying that everything turns to sh*t just because of the GOA low, but it's obviously not ideal, and might lead to a mid-month torch.

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snowstormcanuck

snowstormcanuck

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We have a distant 1040hp anomaly across the West providing N/NE winds around that time frame.

Tonights 0z runs will be important IMO.

In the case with the secondary wave, I think the models aren't handling it properly. No extreme West based blocking to push that storm OTS. The decent HP anomalies across the West should stay across the West providing a nice cool down initially ahead of the system and we have a ULL sitting across the Hudson.

The GFS and even the Euro have been known to kill these waves completely.

A few 6z GEFS members grazed us with the midweek wave. If the models trend towards how the SREFS are handling the upper level wave, I'd start to get interested in that one.

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Snowstorms

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Difference in my mind is that in that ZR storm we had a typical sprawling sfc high located in Quebec feeding low level cold, dry air into srn Ontario on NE winds. In this instance we're not going to get the benefit of evaporative cooling, even after the winds shift NE, as the column is already going to be nearly saturated.

I'm not expecting much from tomorrow, but as you say, let's see. :)

The 12z GEFS is cooler than the OP. with the first wave. I believe a good part of the GTA see's frozen precip with that run.

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Snowstorms

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For trolling purposes after the fact, what's your call for tomorrow? In terms of amounts?

Just to recap, I've called for a possible slushy coating as the precip ends.

Perhaps 2-4cm across the region based on recent models.More across the northern regions of the GTA tho, perhaps 3-6cm.

I'll have another call after the 0z Nam.

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wxhstn74

wxhstn74

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Dec 5-6 Round Two?

Sorry..MY Bad..not putting the date, I'm learning.

Models having difficulty with jet core coming into SW upper low and why the differences in where the front stalls and moisture axis. It does appears the better moisture will be just east of SE MIch when change-over gets going (which is also up for grabs). Hopefully the next few runs will converge on shortwaves shooting out of the Southwest. After that, upper low shoots out over the Ohio Valley mid-late week and that's another mystery.

Just checked out Model disc and states differences well

...INITIAL SFC FRONTAL WAVE LIFTING NEWD FROM THE LOWER MS VALLEY

SUN NIGHT AND MON...

PREFERENCE...12Z GFS/00Z ECMWF BLEND

WHILE ONLY A TAD FASTER..THE 12Z NAM OTHERWISE REMAINS RATHER

CONSISTENT WITH ITS 00Z RUN IN QUICKLY SHEARING SWRN UPR TROF NEWD

THROUGH THE TN VALLEY AND INTO THE NE SUN NIGHT INTO MON WITH A

RATHER FLAT SFC WAVE RIPPLING NEWD ALONG ASSOCD COLD FRONT WORKING

ACRS THE EASTERN THIRD OF THE U.S. GFS CONTINUES TO SHOW MORE

SEPARATION WITH GT LAKES S/WV ENERGY AND ENERGY DROPPING INTO THE

SRN ROCKIES. AS A RESULT IT TOO IS A LITTLE MORE PROGRESSIVE AND

FLATTER WITH THE SFC WAVE RIPPLING NEWD ALONG THE FRONT IN THE NE

BY TUES MRNG. THE NAM LOOKS THE MOST PROGRESSIVE HERE AND SUBTLE

DIFFERENCES IN THE TIMING AND HANLDING OF UPSTREAM ENERGY DIGGING

INTO NW CANADA SUGGEST GOING SOMEWHERE IN BETWEEN THE SLOWER 00Z

ECMWF TIMING OF THE WAVE AND THE SLIGHTLY FASTER AND WEAKER GFS.

...HANDLING OF POS TILTED UPR TROF WORKING ACRS THE GT LAKES INTO

THE SRN ROCKIES MON INTO WED...

PREFERENCE...00Z ECMWF/00Z ECMWF ENSEMBLE MEAN

THE 12Z NAM IS SEVERAL DECIMETERS WEAKER WITH ENERGY IT DROPS SWD

INTO THE SRN ROCKIES/DESERT SW REGION ON TUES AND IS A LITTLE MORE

PROGRESSIVE WITH THE NRN PORTION OF POS TILTED TROF WORKING ACRS

THE GT LAKES REGION AT THE SAME TIME RANGE. GFS REMAINS

CONSISTENT WITH ITS ENSEMBLE MEAN AND IN FACT HAS TRENDED EVEN

SLIGHTLY DEEPER AND SLOWER WITH ENERGY DROPPING INTO SRN

ROCKIES/DESERT SW MON NIGHT INTO TUES. THAT SAID..THE GFS IS THE

SLOWEST..MOST WESTERN SOLN WITH THE HANGBACK TROF. CAN'T SEEM TO

PIN THE DIFFERENCES TO ANY SPECIFIC UPSTREAM FEATURE AS

DIFFERENCES ARE VERY SUBTLE...BUT CONSIDERING HOW MUCH OF A SLOW

OUTLIER THE GFS IS...THE FACT THAT THE ECMWF AND ECMWF MEAN ARE

VERY CLOSE IN SHOWING MORE PROGRESSION AND AT LEAST HAVE MORE

SUPPORT FROM OTHER CENTER SOLNS..HAVE INITIALLY FAVORED A 00Z

ECMWF/00Z ECMWF ENSEMBLE MEAN SOLN. LATEST UKMET IS CONSIDERED A

FAST OUTLIER AND TOO ORGANIZED WITH HANDLING OF SRN PORTION OF THE

TROF COMING OUT OF THE SW.

PS>>>New 12Z UK shoots Tenn low into W Penn by Thus AM..and the plot thickens

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