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Weekend Threat 12/14-12/15


IsentropicLift

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It's a near neutral PNA (slightly negative).

well then there is a disconnect between the math and visual side of things. It might be a mathematical slightly negative PNA but there is fairly substantial ridging into BC and NWT....it might be a BIT to far west....

 

also, the flow into the US is NW to SE straight out of central Canada. If there was a true RNA all the cold would flood the Pacific NW....not sure this makes sense to me....

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well then there is a disconnect between the math and visual side of things. It might be a mathematical slightly negative PNA but there is fairly substantial ridging into BC and NWT....it might be a BIT to far west....

 

also, the flow into the US is NW to SE straight out of central Canada. If there was a true RNA all the cold would flood the Pacific NW....not sure this makes sense to me....

 

 

Yeah, 3-letter acronyms are a very lazy way to look at the pattern...you're better off looking at the pattern and seeing the physical results. 

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this isnt a -PNA - not sure why you think that isnt a +PNA...any shortcomings will be on the atlantic side of the equation. That appears to be a fairly positive NAO. Low heights at the tip of Greenland are about as bad is gets

 

msl_uv850_z500!Geopotential%20500%20hPa%

The ridge axis is too far west for us. You generally want it to be over Wyoming or Colorado for us to have the best chance at a winter storm. That ridge axis would mean the storms would cut over the Apps or Ohio Valley.

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oh for sure. But of there was a block this would be a TRUE miller B....damn h85 low parked over Pittsburgh is a disaster....

 

 

I'm going to hope that the screaming confluence in SE Canada will be enough to shear out that low somewhat...a weaker low will still have enough overrunning and lift from the right entrance region of that jet to produce decent snows. 

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The ridge axis is too far west for us. You generally want it to be over Wyoming or Colorado for us to have the best chance at a winter storm. That ridge axis would mean the storms would cut over the Apps or Ohio Valley.

 

without atlantic blocking that makes sense...look at this map.

 

131212194238.gif

 

the ridge axis is only slightly further east - big diff is the atlantic.

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On the same token, when the GFS/NAM/GGEM show one thing and the Euro is different, some people think the Euro is always right.

 

Not trying to wishcast here but the GFS shows a huge ice concern where I live and the EURO doesn't..., doesn't help at all.

 

I have always thought the EURO is the best at Hr 96 and Hr 120. It acts as "Dr No" when the GFS shows huge snow storms in the LR.

 

I read a lot here and post very little but I think we have a chance here. Every model seems to have flip flopped in their past few runs, thought. That doesn't help at all.

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The 15z SREF has the exact same changeover time as 09z for the metro. Its not warmer up until 60 and the period of snow remains the same length. Afterwards it does appear a tick warmer than 09z which is no longer relevant since we aren't snowing at that point anyway. It does probably lessen the freezing rain risk a bit inland. Otherwise still on track for some nice front end stuff.

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I'm going to hope that the screaming confluence in SE Canada will be enough to shear out that low somewhat...a weaker low will still have enough overrunning and lift from the right entrance region of that jet to produce decent snows. 

 

the confluence is a bit to far east, no?

 

One thing I will say is that at 72hrs the ridge out west flattens out substantially in Canada

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This is another event where the early start time has to be watched closely, the SREFs still seem to show snow as early as maybe 15Z but the globals today as a whole more or less pushed start time in some cases til 21Z which is what the Euro in essence shows...the fact the GFS is only a couple of hours faster starting snow than the NAM is somewhat unusual even at the range of 48-60 hours...the earlier it starts the more snow we see, my guess is most of the coast is changed over by 03Z Saturday night at the latest.

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the confluence is a bit to far east, no?

 

One thing I will say is that at 72hrs the ridge out west flattens out substantially in Canada

 

 

Yes and no. We would also like this a bit further west, but it's still far enough west to prevent significant height rises downstream and dampen out a weak low somewhat...

 

I think what's starting to hurt more is that system diving down from Manitoba and southeastward...that seems to be interacting with the system more and leads to a stronger storm with more height rises. If we can keep that disturbance a bit more progressive, I think the confluence might be enough to go back to colder solutions.

 

Just annoying though that so many things have to go right without blocking. 

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Yes and no. We would also like this a bit further west, but it's still far enough west to prevent significant height rises downstream and dampen out a weak low somewhat...

 

I think what's starting to hurt more is that system diving down from Manitoba and southeastward...that seems to be interacting with the system more and leads to a stronger storm with more height rises. If we can keep that disturbance a bit more progressive, I think the confluence might be enough to go back to colder solutions.

 

Just annoying though that so many things have to go right without blocking. 

 

what is really annoying is that we had a predominantly -NAO from last March thru October, which was utterly unnecessary, and now that its winter it will relax and return in early spring which will screw up early golf season, again.

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what is really annoying is that we had a predominantly -NAO from last March thru October, which was utterly unnecessary, and now that its winter it will relax and return in early spring which will screw up early golf season, again.

 

 

To further elaborate on what I said -- a stronger low that is interacting with the ULL coming down the Plains WILL win out over the confluence that's too far east...but if that interaction were to die down somewhat, I think the low would be weaker and the confluence would shear it out... 

 

And yeah, we had some -NAO periods prior to this, but the huge classic blocking pattern actually has not been seen for a while. All of the blocking has been focused in the NE Pacific for the past several months. Hopefully we can get some more blocking later in the winter, but I'm a bit unsure in that department. Bluewave has posted some analogs which show a bit of promise down the road -- but regardless this winter should have a mainly positive NAO and AO. 

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what is really annoying is that we had a predominantly -NAO from last March thru October, which was utterly unnecessary, and now that its winter it will relax and return in early spring which will screw up early golf season, again.

Did you go ahead in time?..let me know,I would like to have tomorrow's lottery numbers lol

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