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Dec 11-13 MW/Lakes/OV snow event part 4


Hoosier

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MSP airport is making out pretty well this storm at 11.7". Yet my normally reliable spotters in Chaska and Carver are nowhere to be found. If the nws office has published their measurements, I sure can't find them.

Just got a 13" report in from shakopee...looks like the winner so far.

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these are always way overdone, but it lends some credence to my 5-9" IMBY upgrade, which frankly i feel terrible about.

I'm probably going to need the lake to bail me out around your area. Looks like I jumped on a general 6-10" north of I-80 too quickly *kicks self*. Will be interesting to see exactly where the dry slot ends up.

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these are always way overdone, but it lends some credence to my 5-9" IMBY upgrade, which frankly i feel terrible about.

As far as the experimental snow graphics, yes, I agree, 98% of the time they are overdone (by a fair amount, too).

However, this looks to be more of a office drawn snow map. So, I wouldn't discredit it right away.

As far as amounts, it looks good to me. Pretty much alines with what I would expect (4-6" north of I-80, 2-4" south).

Precipitation blooming across LOT, especially into Ford/Iroquois Counties where higher reflectories have persisted (they win....in rain). Going to be a dreary day.

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If you get time, will you explain why the models are trying to put out .15 or so tenths of precip over my area tomorrow, even though models are occluded with the lows and temps are really cold which I thought would dry things out. spme of the hi res models almost look like they show convective elements to things.

It is easy to look at models and see some omega and RH and see qpf being generated, but I don't know why.

Massive wrap around. Actually not a TROWAL this time even though it looks like one. A little different dynamically. IN this case as the compact and intense PV anomaly "wraps" into itself as the main upper low tracks SE, regions of ascent/divergence aloft results in a flow field originating near the actual low level surface cyclone which flows into the upper low to compensate the mass divergence aloft. That is a pretty simplistic reasoning but it is pretty much what is physically happening. It is a massive comma head, and it is different than a TROWAL because there is no warm air wrapping around the cyclone in the mid-levels. It behaves differently and forms for differing reasons. Features like this are more typical of oceanic storms where the initial shortwave deepens rapidly and "wraps" into the main upper low, sometimes multiple times as the lack of low level friction can support deep circulations a lot longer. Land storms are typically dissipated much faster by boundary layer Ekman Pumping owing to friction in equivalent barotropic (stacked or nearly stacked non-baroclinic) lows.

Ah nice, kinda what I was talking about. CIMMS blog did a brief writeup with images so you can better picture it. http://cimss.ssec.wisc.edu/goes/blog/archives/410

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MSP

AVIATION

/18Z TAF ISSUANCE/

QUITE SIMPLY...ITS A TRAVEL NIGHTMARE ACROSS MOST OF SOUTHERN MN

AND WESTERN WI. MANY AIRPORTS REPORTING 1/4SM +SN...SO THERE IS

WIDESPREAD IFR AND LIFR. AN INTENSE SNOW BAND FROM ROUGHLY

KULM...TO KMSP...TO KNRH...TO KEAU IS DEPOSITING 1-2 INCHES PER

HOUR AND NORTHERLY WINDS ARE CAUSING SIGNIFICANT BLOWING AND

DRIFTING. WITH SURFACE LOW PULLING EAST SOUTHEAST LATE THIS

AFTERNOON...THE HEAVY SNOW BAND MAY FINALLY SHIFT FURTHER

SOUTHEAST FROM KRST...TO KEAU BY AROUND 22Z. EVEN AFTER HEAVY SNOW

ENDS...BLOWING SNOW WILL REMAIN A PROBLEM THROUGHOUT THE EVENING

WITH STILL A NICE PRESSURE GRADIENT MOVING THROUGH MN.

KMSP...CONDITIONS WILL REMAIN BELOW OR AT AIRPORT MINIMUMS FOR THE

NEXT 4 HOURS...WITH A GRADUALLY IMPROVEMENT BETWEEN 22Z AND 00Z.

STILL SHOULD REMAIN IFR OR LIFR INTO THE EVENING GIVEN THE LIGHT

SNOW AND BLOWING SNOW. THE AIRPORT HAS RECORDED CLOSE TO A FOOT OF

SNOW AS OF 12 PM CST. ANOTHER 3-6 INCHES IS LIKELY BEFORE THE SNOW

DIMINISHES EARLY THIS EVENING. WIND GUSTS OVER 20KTS WILL LINGER

WELL PAST 06Z TONIGHT.

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I'm probably going to need the lake to bail me out around your area. Looks like I jumped on a general 6-10" north of I-80 too quickly *kicks self*. Will be interesting to see exactly where the dry slot ends up.

Call this a christmas present to all or whatever you like.

12z euro..Tried to capture the LES stuff ( why i went out so far ) but this is not a great model for that.

post-90-0-20856400-1292094235.png

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Definitely the best week in weather I've experienced. I remember spending much of that time discussing them on eastern as I had just joined there.

Just got an email from my parents saying they've got ridiculous drifting in the front yard... Claimed it was a four foot drift on the driveway against the garage (who knows if that accurate). But I'm glad to see the airport isn't lagging well behind chanhassen in the totals as often seems to be the case for one reason or another.

Well, the airport may outperform the forecast office. We'll see The heaviest band has aligned it self on the Scott County side of the Minnesota River for a while now from Prior Lake to Shakopee northeast towards Bloomington, Minneapolis, and St Paul. The snow has definitely picked up even more on the Carver County side in Chaska and Chanhassen but that band just doesn't seem to want to cross the river. A measurement from 1 mile ESE of Chaska at noon reported 9" while at 12:30 in Shakopee they had measured 13". Certain parts of Shakopee are 1 mile ESE of Chaska because of the orientation of the river.

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PRELIMINARY LOCAL STORM REPORT

NATIONAL WEATHER SERVICE SIOUX FALLS SD

1257 PM CST SAT DEC 11 2010

..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...

..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....

..REMARKS..

1159 AM NON-TSTM WND GST 6 W SPIRIT LAKE 43.42N 95.23W

12/11/2010 M61 MPH DICKINSON IA EMERGENCY MNGR

&&

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Well, the airport may outperform the forecast office. We'll see The heaviest band has aligned it self on the Scott County side of the Minnesota River for a while now from Prior Lake to Shakopee northeast towards Bloomington, Minneapolis, and St Paul. The snow has definitely picked up even more on the Carver County side in Chaska and Chanhassen but that band just doesn't seem to want to cross the river. A measurement from 1 mile ESE of Chaska at noon reported 9" while at 12:30 in Shakopee they had measured 13". Certain parts of Shakopee are 1 mile ESE of Chaska because of the orientation of the river.

I am in Shakopee, seems possible, but so hard to measure with the blowing/drifting.

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Well, the airport may outperform the forecast office. We'll see The heaviest band has aligned it self on the Scott County side of the Minnesota River for a while now from Prior Lake to Shakopee northeast towards Bloomington, Minneapolis, and St Paul. The snow has definitely picked up even more on the Carver County side in Chaska and Chanhassen but that band just doesn't seem to want to cross the river. A measurement from 1 mile ESE of Chaska at noon reported 9" while at 12:30 in Shakopee they had measured 13". Certain parts of Shakopee are 1 mile ESE of Chaska because of the orientation of the river.

The deep frontogenetic layer has been slowly drifting SE and the radar is beginning to reflect that with increasing heavy snow heading towards Rochester. Looks like maybe a couple more hours of moderate for the TC then lighter stuff here on out. Then the good winds kick in.

post-999-0-52667300-1292094993.gif

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It looks much heavier than it really is due to bright banding (melting snowflakes aloft), and yes, based on your temps aloft at 925/850 being just above or around 0C, you should get snow out of that.

the loop showed the 850 temps warming northward for the few frames but jumping back south during the last frame, a nice battle to watch.

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yeah 48 hrs. needless to say, it took the wind out of my sail, air out of my tires, and any other analogy let down you can come up with... :P

Well, 2 things..

1) There's still a good 12-24 hours past 48 hours where LES will still be favorable (and flow will back even more with time)

2) Mesoscale models tend to have a western bias (in my experience) in placement, and also tends to want to hold a band west longer. --Of course, this is not always true--

So, I still say you have a pretty good chance.

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Well, 2 things..

1) There's still a good 12-24 hours past 48 hours where LES will still be favorable (and flow will back even more with time)

2) Mesoscale models tend to have a western bias (in my experience) in placement, and also tends to want to hold a band west longer. --Of course, this is not always true--

So, I still say you have a pretty good chance.

How far North/Northeast this low gets will ultimately be the deciding factor for the fetch/flow alignment of the lake effect band (s)

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The deep frontogenetic layer has been slowly drifting SE and the radar is beginning to reflect that with increasing heavy snow heading towards Rochester. Looks like maybe a couple more hours of moderate for the TC then lighter stuff here on out. Then the good winds kick in.

post-999-0-52667300-1292094993.gif

Yeah as soon as I made that post the heaviest band over the south metro eroded away. Looks like the heaviest of the band is now a bit north of Mankato northeast through Lakeville.

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Looks like we should see a little more southward component here before too long.

sfc_con_pres.gif

sfc_con_3pres.gif

Definitely been interesting watching the surface low track. Pretty intense low level warm air advection into southern WI is partially offsetting the ESE progression of the PV Anomaly and keeping pressure falls mostly E. NAM kills off that WAA a lot within a few hours across that area so it does seem this thing will quickly track SE once it begins to change course.

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