11/20/07-11/22/07 FCST: NE/MN/IA/WI/IL (WINTER PRECIP)

[Robert Dewey]

DTX put up watches along and north of I69 for 3 to 6 inches, with the possibility of 8 inches or more. Their expectation is for lake enhancement, so I'm sure those values would most likely be realized in lake-adjacent counties.

I also notice that University of Missouri is anticipating convective snow over areas of northern IL...

Given the model trends, things certainly are looking interesting.

 

[Brandon Sullivan]

Looks like local WFO's have the best accums a little further north than i thought. many offices saying it is short of advisory criteria in some spots, but will issue due to holiday impacts.. DMX/DVN/LOT issued SN Adv.

 

[Joel Wright]

Our local NWS (DVN) hoisted a snow advisory for my local area. I doubt they'd be doing this if this weren't the first event of the season, combined with it falling near a holiday.

Just got home from work so just now took a quick look at the 12z and 18zers. Really not all that much change from last night. The GFS is moving this storm out pretty quick compared to the NAM. The Canadian is sort of in the middle. The UKMET took a disappointing turn more towards a weaker solution compared to it's run yesterday.

All in all, just a marginal event the way it's looking now. Very disappointing considering the strength of the trough and tremendous baroclinicy. Seems like sort of a waste to have all the ingredients in place, and yet apparently it's lacking a strong enough shortwave. The only real interesting thing about it is the fact it's the first real winter system of the season for the midwest.

Anyway, accumulation forecasts should be solidified a bit by the 00z models about to come out. I'm hoping they tweak the moisture levels up a bit, while slowing things up. That's about all we can hope for at this point lol.

 

[Joel Wright]

Nothing really new on the 00z NAM, NGM, and Canadian. Looks like a stripe of 1-3" wet snow to accumulate centered from about St. Joseph MO, up to near the Quad Cities, and on towards Milwaukee by early Thursday morning.

I should be home tomorrow night, so if there's anything interesting maybe I'll post a few pics.

 

[Brandon Sullivan]

From what I can tell. The 0z WRF looks to have shifted the heaviest QPF values a touch south, which is in my favor!! Also, it looks to hold on to Large Scale Precip longer than before.. The GFS appears to hold onto the precip longer too, but has the axis of heaviest precip to the NE, near LOT..

Right now we are getting some moderate rain. I am wondering if the rain occurring could undercut the model forecast temps, with radiation cooling keeping it cooler than forecast tomorrow? That would be nice. It is getting to the Nail Biting Stage.

Edit: 3z RUC shows the main precip axis from Quincy, IL to Chicago, IL

 

[Robert Dewey]

The 12Z NAM continues with it's trends... Even though it has pulled the system further to the northwest, it is actually colder aloft (dropping 925mb T's to 0C near DTW by 00Z/THU). This is also around the time that the heaviest precipitation rates move in, or are about to move in.

If heavier precipitation rates do in fact occur... and given the slight cold air advection... I wouldn't be surprised to see a quicker change over to snow; more along the lines of what the NAM is showing (i.e. around 03Z north of DTW).

The 12Z NAM also puts out quite a bit of QPF during the "snow" time frame... While the ground is still warm and temperatures will be marginal at best, I think areas north of DTW will see at least advisory criteria snow (i.e. +2 inches in 6 hours).

 

[Robert Dewey]

Just got a chance to look at some cross-sections for the DTX area... Convective instability appears to be present for an extended period of time, as seen by the theta-e surface folding. There also appears to be quite strong frontogenesis in that particular area, and no directional shear... This would lead me to believe that some pretty intense banding may occur in a northeast to southwest fashion.

Also of note is how all of the experimental WRF models handle this system. They deepen the system more rapidly than previously thought, as seen by the 850mb height falls. In addition, the ARW core (which is usually drier) outputs over an inch of QPF into the cold sector just north of the thermal gradient.

Making this tricky is the very tight thermal gradient, and narrow warm intrusions seen on the cross-sections.

All in all, I would call for a general 2-4 inches north of a line from KMTC to KJXN. However, I would not at all be surprised to see significantly higher amounts depending on the verification of banding and how the thermal profile sets up. Another aspect to note is the NAM snowfall algorithm outputting +15 inches just east of MI in Ontario, Canada (before someone takes it the wrong way, I said it's something interesting to note).

While many are pushing this system off as a dud, I'm starting to think we might be looking at a "surprise snowstorm" for some areas; again, being highly dependent on certain features (wouldn't be confident enough to issue a watch... or tell a viewing audience).

 

[Maggie Kahman]

Its snowing here in Fairfield; not alot, but it is covering the ground somewhat.

This is what im getting (from WeatherBug)

Now through 11 am

Light snow will be scattered across south central Nebraska through the morning hours. One band of heavier snow...producing a dusting of accumulation and visibilities down to 1 mile...will Slide south of highway 92...and sit along Interstate 80 from York to Kearney through 11 AM. This snow area will gradually work south into Clay Center and Geneva as well. Further west and north...or roughly northwest of a Lexington to Greeley line...the snow will gradually taper off to flurries by late morning. Brisk north winds will keep chill factors in the teens throughout the day.

 

[rdale]

Even with a quicker changeover - ground temps are still in the mid40's across central MI and the heaviest coming at the onset, falling onto rain-soaked ground, probably will prevent much accum especially on the roads. Coming at night means this will be a nonevent for most travelers...

 

[Robert Dewey]

Even with a quicker changeover - ground temps are still in the mid40's across central MI and the heaviest coming at the onset, falling onto rain-soaked ground, probably will prevent much accum especially on the roads. Coming at night means this will be a nonevent for most travelers...

We were able to accumulate 1-2 inches on October 13th of last year... with an air temperature of 35F, and during the daylight hours. If I recall, temperatures were into the 60's up until a few days before the event.

It was quite a sight (I got video of the snow squalls) - most leaves hadn't even changed color yet.

 

[rdale]

I do remember last year's burn - but that was with pretty quick snowfall rates and I don't see this system being capable of that...

 

[Robert Dewey]

I do remember last year's burn - but that was with pretty quick snowfall rates and I don't see this system being capable of that...

We didn't change over until 3AM last night... or a solid 6 hours after what the NAM and FSL RUC soundings suggested.

I suspect the NAM snow algorithm failed horribly over southern Ontario, Canada... where it had +15 inches. Just by looking at the radar loop, it appears as though the NAM was too far north with the heaviest QPF, while too cold (the go big or bust potential hinged on just 1-2C in regards to the thermal fields).

The operational RUC actually predicted the thermal fields quite well, but I discarded it out of pure wish-casting and the fact that it was a tad too strong.