WINTER STORM FCST 12/14/07 - 12/17/07: SOUTHERN US - NORTHEAST US

[Robert Dewey]

All I can say for the 00Z NAM is W-O-W. The westward trend continued, and it's even more intense, keeping the Ohio Valley low dominant for a longer period of time.

End result? Better than 1.25 inches of QPF across a large portion of the Great Lakes - IN, OH, MI, and portions of NY. With snow ratios running at 12:1, that would yield 15 inches... But with the -10C isotherm running so close to the heaviest QPF, and given the lift, I'm thinking closer to 15:1... Which would put out widespread +18 inch amounts.

I wonder if the 00Z GFS will be as ambitious.

EDIT: Looks like the RGEM is just as ambitious as the NAM (981MB over NY/PA at 00Z/MON). I'm actually getting a little concerned that the low might end up too far west, bringing in mixed precipitation as far NW as DTW. Hmmm... However, the RGEM brings the best slug of QPF in (40-50mm) when things cool back down.

 

[Dan Robinson]

The warm punch from the south is the wild card. The 0z WRF even shows a good sized pool of warm air (around 45F) sticking around west of the mountains through Sunday morning, which could limit Ohio's totals. The farther you get west away from that, the better. That cooldown on Sunday afternoon looks pretty impressive as the front swings through, with temperatures dropping 20+ degrees during the afternoon. That may be our saving grace of getting anything from this here.

The ice storm potential looks interesting on the eastern slopes, may be worth checking out tomorrow. It looks like mainly a nighttime event though. Night + mountains = no photo ops.

North of I-80 is where the most fun will be with this system.

 

[Robert Dewey]

Not to get too far off topic, but Rob Dale (if you're reading)... I see the new NAM snow algorithm is outputting 21 inches for KJXN with a total QPF of ~1.25 inches... am I reading that right?

BUFKIT for KDET is showing 22 inches at 1.50 inches QPF...

Of course, those snow amounts would depend on the QPF actually verifying

EDIT: Just noticed KLAN showing 24.7 inches I've never seen values that high here in central or eastern MI.

 

[Robert Dewey]

Seems the 00Z GFS is more "conservative" with 1.00 to 1.25 inches of QPF. It's also a touch colder, which would support the 15:1 snow ratios (again, taking into account other factors... and the consensus between algorithms). However, I did notice the QPF area has shifted somewhat northwestward, and increased in size slightly.

So, here's how it breaks down for the southern MI area (KLAN eastward):

NAM and RGEM: 24 inches
GFS and NGM: 14-18 inches

It just looks weird to see southern MI and >10 inches in the same paragraph.

 

[rdale]

NAM is a little weird with it's surface positions... I'm going on-air with 4-8" for Lansing to Jackson, 2-4" towards GRR, 8-12" for SE Mich. It certainly could be more, but at 24 hours out before first accumulations I'm already holding my breath as it is!

 

[Robert Dewey]

NAM is a little weird with it's surface positions... I'm going on-air with 4-8" for Lansing to Jackson, 2-4" towards GRR, 8-12" for SE Mich. It certainly could be more, but at 24 hours out before first accumulations I'm already holding my breath as it is!

Yeah, it's hard to go against statistics... Seeing a widespread +16 inch event would put some areas (i.e. Detroit) into the record-book category... meaning it's very rare.

Certainly there have been many other times in the past X number of years where the models have shown good consistency and agreement with high QPF / high snow ratio environment, only to see a bust (I can think of a couple right off the top of my head).

 

[Mike Kovalchick]

Yeah, it's hard to go against statistics... Seeing a widespread +16 inch event would put some areas (i.e. Detroit) into the record-book category... meaning it's very rare.

Certainly there have been many other times in the past X number of years where the models have shown good consistency and agreement with high QPF / high snow ratio environment, only to see a bust (I can think of a couple right off the top of my head).

I just about passed out looking at the OOZ NAM for Lansing! I am starting to think that moving my snowblower to my cottage was a bad idea as I have a 1/4 mile long driveway at my house near Haslett with nothing to clear the driveway with but a snow shovel?

I haven't had a chance to look more closely at the latest model runs. Are they realistic? Ensembles? Model runs have been shifting West with almost every run. Over due to jog back East? Wow. La Nina seems to favor a strong low West of the mountains...and with only 5" this season..overdue?

 

[Robert Dewey]

Are they realistic? Ensembles? Model runs have been shifting West with almost every run. Over due to jog back East? Wow. La Nina seems to favor a strong low West of the mountains...and with only 5" this season..overdue?

The consistency and agreement are certainly there for +12 inch amounts from LAN eastward... But statistics argues otherwise.

There are TONS of events where I've said "if that QPF verifies, we (or they) will see 12-18 inches"... only to see 6-8 inches as the rule, and 10-12 inches to be the exception.

This looks just like those other events, relatively speaking, so it's hard to say. Rob has a good point... wait until the snow starts and you can see a radar representation, and perhaps some short-term modeling (RUC).

In most cases, it seems like 8-12 inches is the highest (or at least safest) most forecasters will go without some sort of verification to bump the totals (i.e. 8 inches on the ground, still snowing at 3 inches per hour).

 

[rdale]

21Z SREF showed the most snow (5-10" for eastern half of MI, N IN, NW OH) that I ever recall seeing for a winter event... Usually there's enough spread that you only get a few inches. There's pretty good agreement!

In my web story I'll be putting the potential for more and explaining why - but for onair use I'm going to stay "conservative" (although when I'm going with numbers much higher than NWS, I don't think that's a valid qualifier) until otherwise needed.

The impact of a 7" snowfall is the same as an 11" one, so there's no need to get too whacked with numbers until it starts.

Speaking of - radar looks GREAT coming out of SW IL / MO :>

 

[Joel Wright]

Wow, you Michigan boys will be doing some shoveling with this one!! The models have really upped their QPF with the new 00z/06z runs. Northern Indiana, extreme northwest OH, and much of lower MI is gonna get clocked. This is your storm Robert!

Looks like the rain/snow line will actually back up pretty close to the southeast tip of lower MI. If not, somewhere very close to that. You want to be just northwest of where that ends up, and that looks to be near the DTX area. 10-13", with isolated 17" totals look good for you guys.

Winds are looking pretty damn strong too, especially later in the event as the surface cyclone tightens up.

Enjoy guys!

 

[Danny Neal]

It seems as though Skilling is predicting eight to ten inches of snow for the Chicago area. http://blogs.trb.com/news/weather/weblog/wgnweather/ Seems a bit high, but with strengthening NNE winds off a 36 degree lake....keep in mind air temperatures will be in the teens....we could get into 4-6 hours of lake effect snow fall. NWS wants to keep it conservative with 3-5 and I suppose from the synoptic system that is accurate. As Joel wrote it seems like the main snow fall in the order of the 12 to 14 inch range will be confined from Indianapolis on north and east to Cleveland. As that big Canadian high and this Low merges and tightens up, the pressure gradient will be extreme and I could see 50+ mph gusts at any given time during this event spelling big problems for the North east.

 

[Robert Dewey]

Well, not much has really changed with the 12Z NAM. The rain/snow line does creep up towards the MI border, but I think areas north of the state line will see all snow. However, the warmer profile could tone down snow amounts slightly from what the earlier NAM was suggesting...

I expect a rather large area of 12-18 inches from LAN eastward, as most models agree that QPF will be at or above 1.00 inch. Some of the heavier models, including the research WRF runs, the NAM, and the RGEM suggest 1.25 to as much as 1.75 inches (ARW WRF). Thus, I can't really rule out isolated +18 inch amounts.

I think a bigger story will be the combination with the wind. The latest NAM rapidly deepens this system to 985MB over northern OH, with a very tight pressure gradient. Winds right off the deck approach 40-50knts, so I expect many areas will be sustained in the 25-35MPH range, with gusts around 45MPH... perhaps even a few isolated 50MPH gusts.

If this projected solution occurs, I expect blizzard warnings to be hoisted from northern IN, northwestern OH, into southcentral and southeastern MI.

 

[Jeff Miller]

If this projected solution occurs, I expect blizzard warnings to be hoisted from northern IN, northwestern OH, into southcentral and southeastern MI.

I agree with this, the Cleveland AFD also is mentioning the prospect of hoisting Blizzard Warnings for their forecast area based on near-blizzard or blizzard criteria.

I want to add it is rare for the Conservative Cleveland Office to mention upgrades to Blizzard Criteria. Normally Cleveland is quite the conservative office and will downplay as much as possible (I grew up in this region).

Also, based on history growing up in this region, I don't expect the mammoth 14" plus accumulations to materialize in NW Ohio. Just based on the 30 plus winter storms I grew up with in that area, for whatever reason, the heavy heavy snow will probably remain in SC lower Michigan between Detroit and Ann Arbor. I've seen storms like this time and time again in this region. I suspect Toledo will end up with 8-10", Detroit 10-12", and locally heavier amounts further west. The big story will be low visibilities and strong blowing and drifting of snow.

 

[rdale]

http://wlns.com/Global/story.asp?S=1686033

 

[Robert Dewey]

FWIW, the 12Z GFS has continued the trend with a slightly stronger and further west solution, which gives me more confidence. It's not as heavy with the QPF as the NAM, but still a respectable +1.00... The slightly colder profile might bump snow ratios up a bit and compensate, so snow totals wouldn't be completely different between the two models.

I'm still sticking with 12-18 inches right now for LAN eastward, with blizzard conditions developing around 12Z SUN through 18-21Z SUN.

EDIT: Just noticed GRR expanded the WSW and simply states "a foot or more." I guess they don't want to put an upper limit on the totals, eh?