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January 31st-February 2nd overrunning snow event


Thundersnow12

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It might not mean a big difference but it also looks like the wave is a little weaker and comes ashore further north into BC on the 12z GFS compared to the 0z/6z runs. 

 

that was a huge difference.  The fact that it was weaker, (almost non-existent), didn't allow it to dig towards the southern branch.  That was the biggest diff I could see in the 5h between the 06 and 12z.    We need a stronger vort in the northern stream instead of these strung-out scraps.  I'm not sure how well models handle that and if we could see a turn around.

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A little OT but i was sifting through my old USB and I found these saved images 120 hours out before the GHD storm. Just posting them out as people were making some comparisons with this storm. 

 

post-6644-0-72699600-1422478626_thumb.jp

post-6644-0-86239800-1422478636_thumb.jp

 

Again this is the model runs prior to the GHD storm back in 2011. 

 

 

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fwiw (not much) but the 18z NAM is abandoning the flatter look it had over the northern Plains at 12z. Extrapolating, it would probably still be suppressed, but the hope (and that's all it is at this point) is that maybe this is the beginning of a trend back to a more robust storm. 

 

Decent slug of moisture heading east over MO after 72 hours.  :weenie:

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A few things that I'm trying to weigh...

 

1) The northern stream shortwave is still in the N. Pac upper low right now, it hasn't even formed yet. Once it forms it won't be partially sampled until 12z Friday and fully until 0z Saturday as it looks now. Plenty of time for the intensity of that to change.

 

2) The ridging out west looks plenty amplified to me...not great but it's fairly sharp. The ridging is projected by all three sets of ensembles to really build up towards Alaska Saturday and Sunday. In addition, the AO and NAO will briefly dive negative this weekend into the beginning of next week, with a decent PV over Hudson Bay. This argues for more digging of the polar branch shortwave due to the flow going pretty meridional over central Canada. The amount of digging will also depend on issue 1, but I wouldn't panic over one Euro run. Although the Euro ensembles aren't great, many of them dig the polar branch shortwave more than the op.

 

3) All three sets of ensembles still have at least some members in the more northern camp (IE Ohio River track or north). Although, all three ensembles follow their op every run which limits their use to an extent.

 

4) The western US ridging isn't so strong and far east that the cut-off can't eject, and compared to over the weekend the models are in general still more excited about ejecting the cut-off. One known bias of the Euro is it tends to leave energy back too much in the southwest.

 

All in all, two things (the strength of the PJ shortwave and the ejection of the cut-off) are not very predictable, so large swings are still likely for the next couple of days. The pattern appears conducive for the polar jet shortwave to be pretty potent and possibly trend south in later model runs, which would argue for a better phase with the ejecting cut-off. So, unless the models all trend weaker with the PJ shortwave and slower with ejecting the cut-off I wouldn't panic. With some Atlantic blocking, barring a full phase I wouldn't expect this to cut up to Detroit...with a full phase it is possible, but we haven't seen a full phase modeled much except for the by the GGEM.

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DTX

 

AS FAR AS THIS WEEKEND...MODELS ARE AGAIN JUMPING BACK AND FORTH ON
THE TRACK FOR THE SUNDAY SYSTEM. LATEST MODEL RUNS ARE INDICATING A
WEAKER AND MORE SOUTHERN TRACK WITH THE MAIN JET ENERGY AND
SHORTWAVE ASSOCIATED WITH THIS SYSTEM STAYING TO THE SOUTH OF THE
AREA. SEEING THE MODEL SOLUTIONS VARYING...HAVE GONE WITH CHANCE
POPS UNTIL MODELS COME TO INTO BETTER CONSENSUS. AT THIS
POINT...THE BETTER LOCATIONS FOR SEEING ANY SNOW WOULD LIKELY BE
AREAS CLOSER TO THE OHIO BORDER.
COLDER TEMPS WILL HANG AROUND AS
THE GREAT LAKES REGION REMAINS IN THE LONGWAVE TROUGH THROUGH THE
REMAINDER OF THE EXTENDED.

 

http://forecast.weather.gov/product.php?site=DTX&issuedby=DTX&product=AFD&format=CI&version=1&glossary=1

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A few things that I'm trying to weigh...

 

1) The northern stream shortwave is still in the N. Pac upper low right now, it hasn't even formed yet. Once it forms it won't be partially sampled until 12z Friday and fully until 0z Saturday as it looks now. Plenty of time for the intensity of that to change.

 

2) The ridging out west looks plenty amplified to me...not great but it's fairly sharp. The ridging is projected by all three sets of ensembles to really build up towards Alaska Saturday and Sunday. In addition, the AO and NAO will briefly dive negative this weekend into the beginning of next week, with a decent PV over Hudson Bay. This argues for more digging of the polar branch shortwave due to the flow going pretty meridional over central Canada. The amount of digging will also depend on issue 1, but I wouldn't panic over one Euro run. Although the Euro ensembles aren't great, many of them dig the polar branch shortwave more than the op.

 

3) All three sets of ensembles still have at least some members in the more northern camp (IE Ohio River track or north). Although, all three ensembles follow their op every run which limits their use to an extent.

 

4) The western US ridging isn't so strong and far east that the cut-off can't eject, and compared to over the weekend the models are in general still more excited about ejecting the cut-off. One known bias of the Euro is it tends to leave energy back too much in the southwest.

 

All in all, two things (the strength of the PJ shortwave and the ejection of the cut-off) are not very predictable, so large swings are still likely for the next couple of days. The pattern appears conducive for the polar jet shortwave to be pretty potent and possibly trend south in later model runs, which would argue for a better phase with the ejecting cut-off. So, unless the models all trend weaker with the PJ shortwave and slower with ejecting the cut-off I wouldn't panic. With some Atlantic blocking, barring a full phase I wouldn't expect this to cut up to Detroit...with a full phase it is possible, but we haven't seen a full phase modeled much except for the by the GGEM.

 

nice write up.  I suspect this will come back...to what degree is the question.  It's not unheard of for a threat to disappear like this for one model run in this timeframe, we use to joke about the gfs inevitability to lose a storm 4 days out.   Reading thru a lot of the area AFDs,(MI, OH, IN), no met wants to write this off.  They all basically punted the model runs this afternoon, left previous thoughts in place with the caveat to wait for some future consensus.

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18z GFS not looking good so far in terms of phasing potential.

 

yup....look at the diff between the 84nam and 84gfs.  Where's the northern stream energy on the gfs?    So the question is, playing into biases etc....which solution is more likely?  This is where the argument about waiting for better sampling comes into play.  

post-622-0-27814600-1422483594_thumb.jpg

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yup....look at the diff between the 84nam and 84gfs.  Where's the northern stream energy on the gfs?    So the question is, playing into biases etc....which solution is more likely?  This is where the argument about waiting for better sampling comes into play.  

 

 

Natural inclination would be to pick anything over the NAM at 84 hours, but who knows.  Agree with Powerball that the 18z GFS looks even worse than 12z, which is bad in the sense there's added work to do to get back toward something resembling last night's run.

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Natural inclination would be to pick anything over the NAM at 84 hours, but who knows.  Agree with Powerball that the 18z GFS looks even worse than 12z, which is bad in the sense there's added work to do to get back toward something resembling last night's run.

 

yea but do you remember the difference between yesterdays 18zgfs and the 00zgfs?   I went from a solid snowstorm to a rainstorm. 

 

12 hours ago I was sweating thermal issues, (and the ggem says I still am), now I'm being wiffed to the south with cold dry snow showers by those same models that were threatening me with rain 12 hours ago.  The swings in the last 24 hours have been insane....we always assume the latest is the final....personally I think we're still swinging, at least until tomorrow 12z.   That's when I'll throw the flag.

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The Grinch Storm also....if i remember correctly

Yup that one phased and bombed pretty good, I managed to get almost 2" snow out of it, and had 15mins of the biggest snowflakes I ever saw to save me from my first green/brown Xmas in probably a decade. I wish the GGEM would win out on this storm and everybody could get a good snow for once this winter, but it doesn't look very likely being the only model left with a big dog. I guess we shall see how the 00Z models go, ahh the life of a weather model addict is so fun lol.

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Through 66hr, the 0z NAM doesn't look too bad...further south/west and stronger with the northern stream wave...it's  trying. 

 

More precip and further north across the central plains. 

 

Its slowly moving that storm out of the Maritimes. Need to move it out a bit quicker. 

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