1/20/06 - 1/21/06 - MIDWEST SNOWSTORM

Tim... I thought you said winter was done for the season! :lol:

What I like about this system is no matter how weak the mid and upper level circulation appears to be, there is a very significant amount of vertical motion present along the length of the baroclinic zone, possibly in association with isentropic upglide. This might allow for a rather extended period of very heavy snowfall........ Somewhere.

Models have been flipping around a bit, but I would say anyone from southeast NE... through northern IL and southern WI, into MI are at risk.

I'll probably wait until the short range models capture it before laying down a better forecast foundation.
 
Finalizing grids and publishing now. Will have products done this evening for my homepage. wiscwx.com as in the avatar if you want my thoughts :) I'll make sure to write an extended edition AFD

...Alex Lamers...
 
Right now I'm thinking a track further south than what the 18Z GFS had... All models have shown a southward trend...

While I think the 00Z NAM is too far south, I think the 18Z GFS is too far north. I believe a solution in between the two is most likely at the moment.
 
Yay my products are out! I got borderline winter storm accums in my grid database for S WI/N IL/E IA part of my forecast area...didn't want to go too robust yet. Looks like it will be an interesting system. Lots of agreement on the global models.

...Alex Lamers...
 
GFS AND ECMWF HAS BEEN CONSISTENT WITH A TRACK THAT COULD BRING 6 INCHES OR MORE TO SOUTHEAST WI. OTHER MODELS HOWEVER KEEP THE SYSTEM FARTHER SOUTH. IF GFS AND ECMWF CONTINUE WITH GOOD AGREEMENT FOR SNOW OVER SOUTHEAST WI...WINTER STORM WATCHES MAY BE ISSUED ON THU FOR FRIDAY NIGHT/SATURDAY MORNING.

From Milwaukee/Sullivan AFD.

Still looking good! I have a feeling we still might get screwed as usual though.

...Alex Lamers...
 
Wow... The system is 100% gone on the latest 12Z NAM (or at least VERY far south). Wonder what the GFS will show... Both models weren't looking so hot on the 06Z runs either.
 
Looks like the 12Z NAM is the outliar this go around... Again.

All other models still on track... GFS is a touch stronger than the 06Z run. The models that have the best continuity are the UKMET and GEM, both 12Z models showing a decent wave along the baroclinic zone.

I think the 00Z NAM will come around to a similar solution. Then again, all 4 of the other models could swing towards the NAM run - but that's not very likely at this point, though not impossible (I've seen it happen).

Anyway, consulting on one model (especially the NAM which has been a non-performer this winter) probably isn't the wisest way to handle this one.
 
The NAM's been kinda useless lately... but, it still demands consideration.

As for the GFS, the last couple of runs have been a little less optimistic. Today's 12Z run (in particular) surprised me... HPC suggests it's an outlier, which seems reasonable. Still, trends would indicate a weaker storm overall.

Honestly, comparing the GFS, UKMET, and ECMWF, I come up empty. The track solutions aren't all that different early on (which is what matters most for me here in Omaha), but clearly diverge with time (more important for those of you in the Midwest/Great Lakes). While most of the models support a solution just far enough south and east to keep me on the northern edge of the best snow, it's been my experience that these southern stream systems come out a little farther north than anticipated. So, I'm prepared for some accumulating snow.
 
I'm completely throwing out the 12Z/18Z NAM... Hopefully the 00Z NAM will be in line with the other models. As of right now, the 12Z GFS would have the axis of heaviest snow from northern IL through southern lower MI with intense lift and mixing ratios averaging around 4G/KG. The system isn't coming from the deep south, and with a relatively cold profile I would suspect snow ratios of 12-15 to 1 with this storm. 12Z GEM outputting about .75-1.00 storm total QPF's across lower MI.

HPC Day 3 has a HIGH risk for 4 or more inches, MDT risk for 8 or more inches, and a SLGT risk for 12 or more... HPC also has a bullseye of QPF at 1.15 inches near my area.

We shall see...
 
Thats fine with me Tim. We made it this far thru the winter w/out anything major, may as well get thru the rest of it to. With the exception of the needed precip, I would rather just stay brown until march, and have a wetter than avg spring.

Doug Raflik
 
My computer's been down the last few days getting repaired, so I've been dying to finally look at some model data! (Relying on The Weather Channel leaves a lot to be desired).

Since the storm is just now coming on shore, the next few runs will be pretty important. Even now not all of the storm is on shore, so I think tomorrow's 12z runs will be more telling than tonight's. But, hopefully when the 0z comes out in a bit things will look better.

This morning's runs really speed this thing along, which would severely limit accumulations for whomever ends up in the right track. There does seem to be a lot of moisture available for the storm though.

We are ALL overdue for a good snow, so hopefully one of us can bag a good one with this one, or one soon! 8)
 
The 18Z GFS didn't look so hot... Trending towards the NAM, though not as extreme. 18Z UKMET keeps continuity with previous runs.

If the 00Z NAM trends back towards a stronger solution, then I would be alot more confident. If both 00Z NAM and 00Z GFS show a weaker system than the 18Z runs, then my confidence will be significantly reduced.

But... Looking at the WV loop, the system looks pretty decent. RUC has a nice jet at 250MB diving down the backside of the trough with decent diffluence downstream. I see no reason why the system should fall apart as rapidly as the 12Z/18Z NAM suggests...
 
From what I can tell, the 00Z NAM is significantly farther north than the 18Z run, which is a good trend. Also boosting confidence, the 00Z GEM is identical to it's past two runs (12Z and previous 00Z). In addition, the NGM also trended stronger than the 12Z run.

I always like to analyze trends in the models, as I feel that gives the best indication of what is going on. I have average confidence that this system will be AT LEAST as strong as what the 12Z GFS had, though with more QPF. The reason I think we could see more QPF in the north is the fact that the GFS appears to suffer convective feedback along the GoM, dropping as much as 3-5 inches of rain in a 6 hour period over a rather large grid spacing. That could be restricting the northward transport of moisture in the model...
 
Latest run down...

00Z NAM much further north and stronger than the 12Z runs, but still the farthest south.

00Z GFS a bit stronger and a bit further north than the previous runs. QPF also higher, with super-high QPFs along the GoM gone (still might be overdone down there). QPF axis of 1.15 inches stretches through MI.

00Z RGEM shows the best continuity, but doesn't go past 48 hours. It has a similar look to the GFS though a bit deeper and slower. Produces 1.00 QPF over parts of MO, which might extrapolate into areas further northeast as the precipitation field expands.

00Z GGEM is alot weaker and more progressive. Appears to be the weakest of the models so far with very light QPF amounts.

00Z UKMET is nearly identical to it's previous run... Not much more to say.


Given that, all but one (GGEM) of the models are either continuous or trending slightly deeper. The previous NAM runs appear to be outliers, and I suspect the 06Z and 12Z NAM runs will show an even deeper and further north system. I have above average confidence in a closed 850MB low tracking from central OK through extreme northern OH by FH72. QPF's on the cold side of the baroclinic zone should max out around 1.00 to 1.15 inches with the very intense lift expected. With a slightly deeper solution, I would expect the system to be less progressive, thus owing to the higher QPF values.

HPC Note about the NAM run:

...SYS OVER SW ON DAY 1 AND LIFTING THRU MS VLY DAY 2...
THE NAM IS UP TO 45 M TOO STRONG WITH THE H5 RIDGING IT PLACES
OVER NM/W TX AHEAD OF THIS TROF. THE NAM IS ALSO WEAK WITH THE
H25 WINDS ON THE LEADING EDGE OF THIS TROF...SPECIFICALLY THE NAM
IS 40 KTS TOO WEAK OVER FGZ AND APPROX 20 KTS TOO WEAK OVER BOTH
RIW AND DNR. THE NAM MAY BE TOO WEAK WITH THIS TROF IN THE
FORECAST PD AS A RESULT OF ITS INITIALLY WEAK UPR DYN.

Dewey out.
 
The reason the models were so unfavorable in the previous 3-4 runs was because of very significant initialization errors and missing observations. Tonight's 00Z GFS initialized wonderfully and the actual piece of energy is now onshore in N CA.

...Alex Lamers...
 
00Z Canadian Ensembles are in, and the majority hold a wide stripe of +1.00 inch QPF's, dispite what the GGEM shows.

I am now locking the main threat into an area from Quad Cities IA/IL, through southern lower MI, into most of southern Ontario Canada. This looks like it could be a rather significant snowstorm (+12 inches) for some areas given what the current models and trends are suggesting... But obviously too early to pinpoint anything more specific.

FWIW... GFS does kick winds up across lower MI at 12Z SAT to 20-30KNTS, but with the overal weak pressure gradient I'm not too excited for the prospects of a wind driven snow.
 
HPC noted the NAM was 30-40m too weak with the trough...

Even with that error, NAM has trended slightly stronger and the GFS has trended slightly weaker in the 36-48HR period... RGEM has also trended slightly weaker with the 500MB trough and a touch faster, though the SFC low remains the same intensity at 1010MB. The SREF shows pretty high deviations with the SFC low intensity and 850MB heights. MSLP deviations range in the 3.5-4.5MB range, while 850MB temps are 3.5-4.5 range. The SREF also shows 0.50-0.75 inches of mean QPF with a deviation of nearly 0.50 inches...

As for QPF... RGEM comes in with 25-30mm, or roughly 1.00 to 1.25 inches. NAM has increased QPF in extreme southern lower MI from 0.25-0.50 inches to 0.75 to 1.00 inches. Each run has shown an increase, pushing things further north. The GFS has trended southward and slightly less with the QPF axis, now maxing out at around 1.00 inch across a few places...

Right now, I'll stick with QPF's on the order of 1.00 inch or slighly higher for places in northern IN/OH and southern lower MI, which seems to be the average.
 
HPC has quite the belt of snow projected...with an update coming in the next hour...but local WFOs seem to be projecting low snow ratios around 9:1 and are concerned that the fast movement of the system will knock down totals. LOT is only going with 2-5 inches as of the morning shift which seems quite low given qpf on most models. Last two GFS runs have shifted slightly south with the main QPF but have not weakened significantly.

...Alex Lamers...
 
HPC has quite the belt of snow projected...with an update coming in the next hour...but local WFOs seem to be projecting low snow ratios around 9:1 and are concerned that the fast movement of the system will knock down totals. LOT is only going with 2-5 inches as of the morning shift which seems quite low given qpf on most models. Last two GFS runs have shifted slightly south with the main QPF but have not weakened significantly.

...Alex Lamers...

Actually, the NAM has slowed down somewhat... The previous GFS did have a 6 hour period of intense omega at 700MB, but have now extended that to 6-9hrs. Any slowing of the system could really allow things to pile up in a hurry, moreso than what the current models are showing. In addition, things are quite unstable as DTX noted, with theta folding in on itself indicating raw conditional instability (i.e. upright convection will dominate, versus the weaker symmetric stuff). NAM shows a very tight isentropic pressure gradient across southern MI with an overrunning 50-60KNT flow...

But, if the system ends up faster, things would be cut signifcantly... Right now, I'm going for a 12 hour period of light snow, with a 6 hour period of very intense snowfall rates. As for snow ratio, I guess it depends on how tight the baroclinic zone gets... But the system isn't really coming from the deep south, so the ice crystal types in the higher cloud tops might support a higher snow ratio...

I'm still thinking, with the current runs and trends, that someone will end up with over a foot.
 
12Z WRF NMM Core is quite a bit stronger than the operational NAM...

It outputs 2-3 inches per hour for 3-6 hours, with not much more before or after. The 700MB omega fields are absoluting stunning - more indicative of a strong nor'easter with -15 to -20 ubars/s... The ARW Core on the other hand, is weaker... The NMM is capable of resolving features such as dynamic cooling, thermal circulations, etc..
 
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