FORECASTS: 2/7/10 to 2/10/10 - Midwest & Great Lakes Winter Storm

[Robert Dewey]

I haven't been paying much attention to the models until this morning, and was surprised to see a possible snow event across the Great Lakes region. NAM & GFS are both exceptionally high with snow ratios (+20:1), with 0.50 to 0.75 inches of QPF. The BUFKIT output shows generally +8 inches of snow across most of the area, with specific sites reaching 12-15 inches (LAN, DTX).

Going over historic events, this setup is quite favorable for a heavy snowfall with a coastal low and a secondary low across OH / IN.

The event it still a couple days out, so lots of time for changes... and I'd be afraid to call for anything over 8 inches at this point.

 

[rdale]

Agree with your last line, I'm okay going public with 4-8" but I'm letting people know it could be worse. I find it hard to see how we'd miss at least a good snowblow event out of this...

 

[Robert Dewey]

Interesting to note that the GEM is stronger than both the 12z & 18z NAM/GFS at 0z WED (18z RGEM is 10MB stronger than the 18z NAM). The 12z GEM has a pretty healthy QPF bullseye just S of MI. Obviously with a stronger low, we'd probably end up with higher snowfall rates for a longer duration, depending on how quickly the coastal low takes over.

 

[Mike Smith]

Light to moderate falling snow here (1 mi. NW of AAO ASOS) with the ground now white.

 

[Robert Dewey]

In the past 24 hours, my location has went from being at the southern edge of the heaviest snow forecast to the very northern edge... which has shaved a few inches off. 12z NAM BUFKIT still showing 8-10 inches (as opposed to 12-14 inches)... but nothing like the 14-16 inches it was showing for LAN on the 0z run.

It's really about location, as the models have been pretty consistent with total QPF and thermodynamics. I'm also not completely sold on the strength of the SFC low - NAM has been trending deeper (998MB at 6z 2/10), as has the GFS and the RGEM to an extent.

 

[rdale]

The pivot pont is going to be critical, I've upped my LAN an inch to 5-9" but won't go doubledigits until I am convinced (once you put a foot in your forecast range, that's what people will remember.)

 

[Robert Dewey]

The pivot pont is going to be critical, I've upped my LAN an inch to 5-9" but won't go doubledigits until I am convinced (once you put a foot in your forecast range, that's what people will remember.)

I agree with that. My dad (and most other non-wx folks that I talk to) take the max forecast and run with it. If it's 6-12 inches, I hear from everyone "so, we're expecting a foot huh?"

I'm waiting for updated totals out of MN and IA... So far, I've seen a report of 3 inches of snow with liquid equivalent of 0.15 inches, for a 20:1 ratio. Willmar MN is sitting at 7.5 inches as of 8:30AM CT... with most locations in the 3-5 inch range. The radar returns aren't all that impressive, especially near Willmar... but I'm thinking the radar beam might actually be overshooting the best precipitation; something to consider when watching the radar today.

 

[John Vandehei]

I see both the GFS and NAM both put down approximately 0.75" of QPF for my location. At a 10:1 ratio, that would be at least 7 inches of snow. At 20:1, we're talking 15 inches! Considering this thing is still 24 hours out, I certainly don't want to go out on a limb and go that high yet. However, double digit snowfall totals are not out of the question. At the very least, I might have to skip work and go out skiing tomorrow - I haven't skied decent powder in Michigan in quite some time.

 

[Robert Dewey]

I see both the GFS and NAM both put down approximately 0.75" of QPF for my location. At a 10:1 ratio, that would be at least 7 inches of snow. At 20:1, we're talking 15 inches! Considering this thing is still 24 hours out, I certainly don't want to go out on a limb and go that high yet. However, double digit snowfall totals are not out of the question. At the very least, I might have to skip work and go out skiing tomorrow - I haven't skied decent powder in Michigan in quite some time.

BUFKIT NAM and GFS are both suggesting 14-16:1 ratios, which seems pretty reasonable to me.

 

[rdale]

A look at the sounding (and Cobb and UWM algorithms) make it pretty clear that 10:1 is not in the cards... At least 15:1 and more likely 20:1

http://sanders.math.uwm.edu/cgi-bin-snowratio/sr_map_main.pl

 

[Robert Dewey]

Some of the 12z WRF research runs are pretty interesting. Note that they aren't much stronger than the operational model (in some cases, actually weaker)... but they're a bit more rambunctious with QPF. I'm wondering if that has something to do with the finer resolution and convective schemes?

 

[Robert Dewey]

Well, DTX has backed off on issuing a warning... with the general thought being 4-8 inches, with an isolated 10 inch amount along the OH/IN border (as opposed to CLE with 8-12 inches and IWX with 9-14 inches at the border). Among some of the reasons include lack of significant forcing within the TROWAL (most significant forcing is along the 500mb vort), and a "tenuous" thermal profile, leading to liquid ratios of 12:1 instead of 15:1 or 20:1. I'm not sure I completely agree - I think DTW and points southward definitely should have went over to a warning... while keeping the watch in effect for areas further north.

 

[cstrunk]

The snow bands across central Iowa have seemingly stalled, as mentioned in the last DMX forecast discussion and which can been seen on radar trends. There may be some redevelopment of snow just to the west, before the low drops south and brings in more snow (and wind) overnight.

Since yesterday, in Ames we have probably received 6-7" of snow. It's snowing lightly/moderately now. We'll see if more snow moves in tonight as expected, before the winds really start to howl from the north.

 

[rdale]

Well, DTX has backed off on issuing a warning... with the general thought being 4-8 inches, with an isolated 10 inch amount along the OH/IN border (as opposed to CLE with 8-12 inches and IWX with 9-14 inches at the border).

Which is why most trained TV meteorologists don't bother showing winter weather alerts from the NWS... Let your forecast be your forecast. NWS DTX has 5-11" indicated in the point-n-click. I have a hard time believing that people will click their city, see those numbers, and say "Well, there is no winter storm warning, but Grand Rapids has one, so I guess we're only getting flurries here."

 

[Robert Dewey]

Already seeing 6-11 inch amounts out of MN into IA... Definitely a long duration event. From what I can see on the 0Z NAM, the 500mb shortwave is a tad deeper, with the associated vorticity correspondingly stronger and elongated further north. I'm definitely digging the trend, though I admit I haven't checked out anything under the 500mb level yet (I'll reserved judgment until the full NWP data is out).