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December 9-10, 2018 Wintry Weather Threat

Ralph Wiggum

By Ralph Wiggum,
in Philadelphia Region

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Ralph Wiggum

Ralph Wiggum

Posted
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Posted
2 hours ago, hazwoper said:

0Z GFS op has moved north....

Everything except cmc moved north at 0z. GEPS is now several big hits. Euro moved 140 miles N with lp. Expect this to continue as we get better data sampling. GEFS means qpf adjusted N quite a bit...accum snows back into parts of the region. Pretty large jumps north all around minus cmc.

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RedSky

RedSky

Posted
Posted
1 hour ago, The Iceman said:

This is right where I want to be in the 96-120 time frame. No way would I feel good being in the bulls eye with the shifting N every run. I would still be wary of a changeover for 95 if this comes N. 

12" DC 6" Philly and .5" imby it's right it fits the pattern this year

 

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The Iceman

The Iceman

Posted
Posted

OP Euro was ugly with a capital U. EPS still has enough positive solutions to stay interested though time is running out on this one. The shortwave is over AK...the 00z should have even better sampling. If we don't see meaningful changes by then, we likely aren't seeing any. Stranger things have happened though and we still have the CMC, who knows, maybe those crazy canadiens know something we don't. Riding it though until it folds LOL hey steve, whats the CRAS saying??

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Newman

Newman

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Posted

The men and women at Mount Holly are on our side with this one: 


The 12z ECMWF
and GFS keep this system well to the south of the region as it
progresses off the coast Sunday night. To be blunt, I am not buying
what the models are selling, though I do think the sharp gradient in
precipitation on the north side makes physical sense (given the
strength of the surface high to its north). A perusal of ensemble
guidance suggests the trend has been for a slower exit stage east of
the southern-stream system, and there are indications that the
interaction with the upstream northern perturbation somewhere in the
vicinity of the northern plains late this weekend could act to (1)
force the southern-stream system farther north with time (as models
tend to struggle mightily with at this time range) and (2) act to
develop a secondary low somewhere upstream (west) of the southern-
stream low. According to the 12z ECMWF, this second low is prevented
from moving northward by a digging shortwave in eastern Canada early
next week. However, the GFS is much faster with this trough,
suggesting that timing uncertainty is very large with this important
feature.

With so many perturbations and complex interactions at play and
large run-to-run variability, I tend to resort to systematic biases
of each model as a starting point. At this time range, models often
are too aggressive with the northern-stream kicking the southern-
stream system offshore before the inevitable northwest-trending
tracks within 48 to 72 hours of the event. The 12z CMC is worthy of
noting its farther northwest track and has been fairly consistent
with this. Given all of the above, it is premature to trim PoPs in
our area Sunday afternoon through Monday night. In fact, I spread
PoPs northward to account for what I suspect are model biases
exhibiting their usual selves. Given the trend this cool season so
far, broad-brushing the timing and expanding PoPs well northward of
medium-range consensus seems to me the wise choice at this juncture.
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penndotguy

penndotguy

Posted
Posted
18 minutes ago, Newman said:

The men and women at Mount Holly are on our side with this one: 


The 12z ECMWF
and GFS keep this system well to the south of the region as it
progresses off the coast Sunday night. To be blunt, I am not buying
what the models are selling, though I do think the sharp gradient in
precipitation on the north side makes physical sense (given the
strength of the surface high to its north). A perusal of ensemble
guidance suggests the trend has been for a slower exit stage east of
the southern-stream system, and there are indications that the
interaction with the upstream northern perturbation somewhere in the
vicinity of the northern plains late this weekend could act to (1)
force the southern-stream system farther north with time (as models
tend to struggle mightily with at this time range) and (2) act to
develop a secondary low somewhere upstream (west) of the southern-
stream low. According to the 12z ECMWF, this second low is prevented
from moving northward by a digging shortwave in eastern Canada early
next week. However, the GFS is much faster with this trough,
suggesting that timing uncertainty is very large with this important
feature.

With so many perturbations and complex interactions at play and
large run-to-run variability, I tend to resort to systematic biases
of each model as a starting point. At this time range, models often
are too aggressive with the northern-stream kicking the southern-
stream system offshore before the inevitable northwest-trending
tracks within 48 to 72 hours of the event. The 12z CMC is worthy of
noting its farther northwest track and has been fairly consistent
with this. Given all of the above, it is premature to trim PoPs in
our area Sunday afternoon through Monday night. In fact, I spread
PoPs northward to account for what I suspect are model biases
exhibiting their usual selves. Given the trend this cool season so
far, broad-brushing the timing and expanding PoPs well northward of
medium-range consensus seems to me the wise choice at this juncture.

Hmm very interesting, I just can’t believe we aren’t going to see anything 

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Ralph Wiggum

Ralph Wiggum

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37 minutes ago, KamuSnow said:

Ok, do I get a clue?

CRAS meso has a classic setup with a 50/50 moving into place, stj energy undercutting split flow out west, developing +pna, 2 lobes of energy diving into the midwest...looks alot like the NAM. Again....right or wrong who knows? I try and never take the CRAS verbatim at face value but due to it's high resolution it can sniff out changes before some of the globals. Boxing Day storm is a prime example.

In any event some of our energy will be moving  onshore out West over the next 24-30 hours. If we dont get some shifts on the globals by 0z tomorrow night or the mesos start backing down then it's time to be concerned. Still have a window to see positive moves tho. Seen crazier things happen and it wont take major changes aloft still. 

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KamuSnow

KamuSnow

Posted
Posted
34 minutes ago, Ralph Wiggum said:

CRAS meso has a classic setup with a 50/50 moving into place, stj energy undercutting split flow out west, developing +pna, 2 lobes of energy diving into the midwest...looks alot like the NAM. Again....right or wrong who knows? I try and never take the CRAS verbatim at face value but due to it's high resolution it can sniff out changes before some of the globals. Boxing Day storm is a prime example.

In any event some of our energy will be moving  onshore out West over the next 24-30 hours. If we dont get some shifts on the globals by 0z tomorrow night or the mesos start backing down then it's time to be concerned. Still have a window to see positive moves tho. Seen crazier things happen and it wont take major changes aloft still. 

Lol, I thought of the CRAS, but didn't know it was a mesoscale model. I was curious because as much as the majority of models are (for now) consistent with a southern and out to sea track, it's not quite a done deal yet due to all the moving parts and how they evolve. Getting snow this far north looks like more of a long shot now, but I'm giving it another day or two, and open to different reads, so yeah. Thanks!

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Stormman96

Stormman96

Posted
Posted
5 minutes ago, KamuSnow said:

Lol, I thought of the CRAS, but didn't know it was a mesoscale model. I was curious because as much as the majority of models are (for now) consistent with a southern and out to sea track, it's not quite a done deal yet due to all the moving parts and how they evolve. Getting snow this far north looks like more of a long shot now, but I'm giving it another day or two, and open to different reads, so yeah. Thanks!

Now we lost the nam.  We are going in wrong direction 

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Ralph Wiggum

Ralph Wiggum

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Was just about to post that about the NAM. Yep we r going the wrong direction. Still a window but even with a North shift things may have gone too far South already. Good tuneup for tracking anyway. Euro weeklies say we r in for an active run. Hopefully tho this doesnt become a pattern this year. Cold, dry, and suppressed storm patterns suck. Would rather get cutters with waa thumps to rain.

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