2/1 - 2/3 FCST S. PLAINS/MIDWEST/GL/NE STORM

[Jonathan Whitehead]

Well my facebook news feed couldnt be anymore apocalyptic for the Norman/OKC area. That said, its going to be quite a close call for Norman. All the Earl barkers snowfall accumulation total maps Ive seen so far have quite a tight gradient NW-SE from Norman to Ada. Wouldnt surprise me at all if its so tight as btwn Slaughterville and Norman. Either Norman is going to get dumptrucked or its going to miss by 20 miles, though most of the models do have Norman in the "money area" so if I were a met at OUN Id be pulling the trigger on armageddon as well.

EDIT: Forgot to put plug in for my Missouri River Valley AFD I posted this afternoon on my page found at the link in my sig.

 

[Joel Wright]

This continues to look like a classic high-end Midwest snowstorm. The type we see once every 10 or 20 years. The global models have remained the most consistent, which isn't much of a surprise. The NAM has had a few hiccups over the last day or so. Namely the two prior 18z runs, and I think the new 00z as well. Basically most of the models have slowly converged onto what the Euro has been advertising for days. A wide swath of 12-18" snows still look likely from central MO, through central/northeast IL, northern IN, and into southern lower MI. Isolated higher amounts would be possible, but these off the wall amounts of 25"+ I've been seeing are probably overdone. Even though SLRs will be relatively high, the strong winds will really act to granulate the snow as it falls through the air, and also pack it in pretty densely on the ground.

 

[David Reimer]

It's looking like a close call here for the D/FW Metroplex. As we stand right now, the most significant accumulations of ice/sleet/snow will be just northwest of the metroplex (literally by 30-40 miles). Since we're still over 24 hours out from the event here, I'm a little nervous about something causing accumulations to increase here (whether it be a quicker transition or a later onset). The models generally held to their own tonight, with the 4 KM WRF supporting my suspicious of a slower onset down here. I'm not going to lose sleep over the exact location of the freeze line yet, but it's sure going to be an interesting event. Even if we don't get a major storm here in D/FW, we'll end up with ridiculously cold temperatures and a little drought relief which will hopefully help us (even if its a little) for spring.

I've posted a fairly large discussion over on the Texas Storm Chasers website, you can read it here.
http://www.texasstormchasers.com/2011/01/30/212011-winter-storm-discussion-2/

 

[Robert Dewey]

GFS and GEM have trended stronger, with the NAM coming in a bit weaker. GFS still throwing around 1.25 inches of QPF up around Detroit on a 20:1 ratio between the various methods. One thing I noticed is the winds within the mixing layer have increased, almost tapping 60knts within the first 2k ft during peak snowfall rates (GFS is indicating 9 inches in 3 hours). The downside to the wind, as Joel mentioned, is that this would likely work against higher snowfall ratios, so I'm thinking 15:1 at most... which still yields 16-18 inches.

If I was calling the shots, I'd probably go with 10-15 inches for much of southern lower MI, and increase amounts only as needed for specific areas (counties within heavier bands). Blizzard criteria looks probable at this point.

EDIT: After reading the MKX AFD, looks like they are going with a 13:1 ratio for their SE sections given the wind speeds. With that in mind, I'll stick with my 10-15 inch guesstimate.

 

[Andrew Francis]

I'll take this... lol, but on a more serious note, the local OKC mets calling for 6-8 in OKC and Tulsa with close to a foot. Major emphasis on wind chill factor on Tuesday as the blowing snow with temps in the 20s will be intense.

I am ready for this thing to evolve! I want to see where the money band sets up soo badly. I am very anxious. It looks like Springfield MO could miss out if the track is just a handful of miles further west. It is going to be crazy to see totals of 12"+ taper to an inch or two as you travel east along the snow line.

 

[DWest]

Latest model trends looking good for my area - NAM coming in line with the GFS and painting a good solid 14+" snowfall, even up to two feet if the latest GFS turns out to be accurate. Not sure I'd hold my breath for the latter, but I can always hope.

 

[John Vandehei]

One thing I noticed is the winds within the mixing layer have increased, almost tapping 60knts within the first 2k ft during peak snowfall rates (GFS is indicating 9 inches in 3 hours). The downside to the wind, as Joel mentioned, is that this would likely work against higher snowfall ratios, so I'm thinking 15:1 at most... which still yields 16-18 inches

Kind of what I was thinking. The winds are going to do two things. One, strong winds creating lots of collision for the snow flakes on the way down. This prevents the formation of large fluffy flakes, which are best for high snow fall totals. The smaller flakes we will end up with will pack down more densely when they accumulate. Also, wind driven snow will pack down tighter as well. There is also historical precedent going against some of the 20+ inch totals I've been seeing (at least for here in Michigan). To get that kind of snow (excluding long duration lake effect events), typically you need a situation where the surface and upper levels lows stack up, creating a storm that will linger two or more days. The models have been advertising this one to move through here in 24 hours or less. One of the area TV meteorologists covers this well on his blog, stating that Grand Rapids (MI) has never gotten a foot of snow in one single day in February, and that the highest one day snow total was 16.1 inches. The other thing going against this storm, as I mentioned in my earlier post, is that the low begins to fill as it nears Michigan. It appears that a secondary low begins to form near the east coast by Wednesday afternoon, which will shift the energy away from the western Great Lakes. All this being said, this still will be a significant storm. With progged QPF's in my area between 1.25 and 1.5, that would support 16 to 20 inches of snow around my location, assuming a 13:1 snow/water ratio. Even if we only got a half a foot, the winds along will make this quite the storm. Right now, I going to conservatively forecast 14 inches for my location, even though I'm open to the possibility of picking up more.

 

[Jeff Piotrowski]

0Z Baron Bams Model Snow forecast model.

‎0z BAMS snowfall accumulation forecast through 6pm Thursday. The snow band jumped further east on this run. St. Louis still on the edge of the heavy snow line on this model, but with trend east, expect changes upward in accumulation there. Freezing rain and sleet accumulations not depicted on this model. Those area will be on the southern side of the snow belt

 

[Robert Dewey]

NAM keeps switching things up, at least around here. My location went from 1.15 inches of QPF down to about 0.70 inches now, as the high pressure to the north is predicted to be stronger, eating away at the precip shield from WI through lower MI. The thermal profile is colder with that run, so snow ratios would probably end up between 1:15 to 1:20... which still yields 10-14 inches in a best case scenario. Definitely a trend away from the monster numbers shown earlier.

I really don't like how the system is weakening by the time it affects the Great Lakes. All models indicate this.

RGEM is now in, and it's still in the same ballpark as the 12z GFS in terms of track / strength / QPF. I'd like to say the NAM is the outlier, but I've seen high pressure to the north kill off QPF-bombs one-too-many times.

 

[Tim Vasquez]

The 12Z NAM has just come in and it puts the axis of snowfall accumulation across Norman to just north of Tulsa. The totals haven't changed much from what other posters have pointed out.

I did happen to see that the GEM is going for only a fraction of the amounts forecast by the GFS and NAM, all up and down the track. I haven't ever paid much attention to the Canadian models... do they usually err on the low side? I'm wondering if this has something to do with differences in the convective parameterizations in their models vs. at NCEP.

Anyhow what I'll be interested to see is if we develop any sort of LLJ that delays the precip transitions, and how well the models handle that. It might be worth comparing profiler data with model data in the lowest 100-200 mb across Texas and Oklahoma as the night wears on.

Tim

 

[Chris Carter]

OAX has lowered our snow amounts, we were sitting around 4 to 12 inches from Norfolk to Falls City, now it looks more like 2 to 10 inches in the same area. I'll stick with my gut and still say 7" in Bellevue.
This storm has the potential to be historical in terms of affected people and records. It can't be a historical storm for all though.

 

[Robert Dewey]

I haven't ever paid much attention to the Canadian models... do they usually err on the low side? I'm wondering if this has something to do with differences in the convective parameterizations in their models vs. at NCEP.

The 15km GEM doesn't seem to be too far off from the GFS;

http://www.weatheroffice.gc.ca/data...4_R1_north@america_I_4PAN_CLASSIC@012_036.jpg

http://www.nco.ncep.noaa.gov/pmb/nwprod/analysis/namer/gfs/12/images/gfs_pcp_036m.gif

For those relying on the 12z NAM, I just noticed this message from NCEP: http://www.hpc.ncep.noaa.gov/discussions/pmdhmd.html

AN UNRESOLVED CONCERN HOWEVER IS THAT MISSING RAOB DATA FROM SAN DIEGO MAY BE CONTRIBUTING TO THE NAM'S QUESTIONABLE INITIALIZATION WHICH SHOWS THE CENTER OF THE MID-LEVEL TROUGH AS MUCH AS 50-75 NM EAST OF ITS APPROXIMATED POSITION ACCORDING TO WATER VAPOR IMAGERY. THUS...THE NAM'S SLOWER/STRONGER TREND ENTERING THE PLAINS IS QUESTIONED.

 

[Mike Smith]

Tim,
I've found the GEM pretty worthless in the major storms.
Mike

 

[Tim Vasquez]

Regarding the GEM depiction of snowfall totals, I had been looking at this:

http://grib2.com/gem/CONUS_GEM_SFC_ACCUM-SNOW_72HR.gif

This says about 4 inches in OKC and Tulsa with 8-10 inches in Missouri. I agree that the QPFs do appear to be in the same ballpark, so the GEM's snowfall figures are a bit of a mystery. If the GEM gets this one right and we get hosed on snow, I'll have to pay more attention to it in the future.

Tim

 

[Jesse Risley]

The ECMWF continues to remain the outlier with this event. It will be interesting to see how the low tracks as compared to what the models are progging. The NAM and GFS seem to have come into somewhat better alignment in the earlier phases of the system, even if the NAM is slightly off on its prognostications due to aforementioned reasons. It's also interesting to see such high snowfall totals progged on the SREF mean 12 hr outputs, as it's unusual to see 12+ inches on the mean calculations...the bulls eye continues to be depicted from NE MO towards CHI.