Monday, April 8, 2013

Significant April Snow Coming For Midweek?

As of Monday morning, forecasters were predicting snow for midweek that could be more than just conversational. We'll track the forecasts later today.

The scene on April 30, 1984 outside Lakewood Cemetery in Minneapolis.

Looking for a little weather education? Here's our weather instructional video for this week's unfolding situation from Tom Novak at @NovakWeather.


Several have asked us to include Tom Novak's response as to why he thinks the storm may track further north than others are forecasting. Here is his response (copied from a comment in the previous blog post):


I can't speak for those forecasting at the MPX NWS (They have several shifts hence different forecasters), but my M.O. with weather forecast is more of a "top down" approach rather than vice-versa. Let me explain.

When I look at model data, I almost always look at the 250mb level first (Jet Stream level) before drilling lower in our atmosphere. This is especially crucial when viewing a storm that is more than 48 hours out. Once I get a good feel for the upper-level dynamics, then I drill deeper into the mid-levels before finally ending my viewing on the surface features.

It is safe to say that I place much more weight on the mid & upper level dynamics than I do with the surface features especially when forecasting more than 24 hours in advance. Hell, I never trust surface weather maps including QPF (precipitation forecasts) until approx. 36-48 hours before the onset of a storm.

I've learned my lessons the hard way by placing way too much emphasis on surface features, including QPF, too early in the game. This is a trap that many weather forecasters run into especially those with little time on their hands and/or who are simply too laze to view all atmospheric levels.

With the impending storm for this week, I'm pretty confident that the storm will track further north than what some forecasters are predicting. There are several reasons why I'm going with this scenario:

1.) Jet stream dynamics support a further north solution with the mid & upper level lows. All computer models are on board with this. Remember, even though the surface low may track well south of MN through IA, MO & IL, the upper level support will linger well NW of the surface low over so. MN.

2.) Strong forcing at the 850mb, 700mb & 500mb levels will tend to keep the precipitation shield established well north of the surface low.

3.) I can't believe I'm still saying this, but Arctic air is still alive and well in the northern U.S. including much of the Upper Midwest & MSP metro.

Put all of this together, and you have a mess on your hands for much of MN. I hope this all makes sense.

40 comments:

  1. NWS has upped the snow amounts a tad to 2-5 inches for my point forecast for Tuesday night into Wednesday...but still seems conservative from what Novak was saying in his last post from the last thread....btw Bill I think you should move that last post from Novak from the last thread to this one,it was a very good explanation and in my opinion info worthy for this thread as well.

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  2. This weekend looks absolutely miserable. yr.no is predicting a low of 14 for Saturday and 10 (!) for Sunday. That would be a record low for Sunday.

    On the other hand, if this brutal weather delays the inevitable yard work, fine by me.

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    1. Really?....is that even possible,I guess maybe if there was fresh snowcover,but isn't what we get mid-week going to melt by then,I haven't seen anyone else forecast lows that low,NWS has 30's for lows with rain likey! What is yr.no?

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    2. It's the ECMWF.

      http://www.yr.no/place/United_States/Minnesota/Minneapolis/long.html

      It's moderated significantly since I posted that this morning.

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  3. Can somebody explain to me what the hell is up with the latest GFS snowfall forecast? Is it onto something or on something? I'm assuming the numbers are well overdone, but does what it's showing mean anything?

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  4. Excellent post at the end of the last thread, Novak! I always appreciate the explanation behind a forecast. Keep up the good work.

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  5. I just saw on Weather Nation that Paul Douglas and his gang are NOT on board with a big snow for the metro. Their computerized snowfall forecast shows just .2 inches of snow for Minneapolis by 7 p.m. Wednesday.

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  6. First off all the base of the trough was on shore by 12z/08, according to water vapor imagery so the models should have gotten a reasonable read from RAOB(balloon) network. While both the NAM and the GFS show QPF's (precipitation amounts) very close to 2", the Nam was warmer at 700mb compared to the GFS, therefore it shows almost .75" of sleet at MSP and snowfall of around 6". The GFS doesn't have any sleet. IMO where that 0° 700mb line sets up will tell the story.

    Every model I have have looked at is showing heavy snow in the metro. The list includes the 4k Nam,Euro,GFS,Ukmet,RPM,Gem and reg NAM, although the later shows the heaviest for the north metro. Looking at where the models set up the upper levels lows down to the surface is favorable for heavy snow.

    The possibilities at this time (keyword possibilities) is somewhat mind boggling, and hard to phantom for this time of the year.

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  7. NWS has just posted a Winter Storm Watch for the Metro for a mix changing to snow Tuesday night to Thursday morning (possible 6+ inches of snow).

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  8. MNMOWCO I hope your hearing all this......you need to change back to MNPLOWCO in a hurray.......like you say it will snow on the hard!

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    1. Ha, big daddy! I hope Paul Douglas is right with a couple of slushy inches on the grass and on the hard just wet.
      Blowers are back on the Bobcats and shovels and the like are at the ready....But I'm really thinking slush and a quick melt even though temps don't seem to be very warm....yet still above freezing. Green or white it still is $$ to me. Although I would rather have green.
      Cheers
      MNPLOWMOWIDONTKNOWCO

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  9. Wonder how much plowing will be necessary with this one... I'm skeptical there will be that much, but what the heck do I know!

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  10. Weather service has gone from reducing amounts to saying 6-10 inches of snow may be a good bet across a good chunk of the area. This really is amazing how winter got off to a slow start and now doesn't seem to want to go away. Models will be interesting tonight to see what they do.

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  11. Plymouth Weather LoverApril 8, 2013 at 9:33 PM

    Wow!! What else can I say? I am speechless and getting ready to wet my shorts!! Bring on a record. Bring it! C'mon. Record needed!!

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  12. Mr. Novak has shifted his HIGH IMPACT area to now include the MSP metro area and says 6+ potential is a good bet!

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  13. I just read Paul Huttner's blog,tell me the GFS model is not true,can we/are we going to get 20+ inches of snow,tell me thats not possible!

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  14. New NWS graphic has upped the ante even further...calling for 6-12 inches,were bordering numbers getting out of hand...are we going to see something extreme here Randyinchamplin?Novak?Duane?anyone?

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  15. Nightmare scenario setting-up for much of southern MN, including the Twin Cities. ICE then SNOW.

    As cold air seeps in at the lowest layers of our atmosphere late tomorrow night into WED am, our liquid will melt on contact, especially outside of the core metro. I wouldn't be surprised to see 1/4 to 1/2 inch of ice by noon WED.

    Then, as the rest of the atmospheric column cools, the liquid will change to all snow later WED & accumulate at a good clip overnight WED into early THUR. I can't imagine getting a foot, but a good 6"-10" of heavy wet snow seems reasonable.

    Needless to say, one hell of a storm with a ton of moisture over a prolonged period of time. My hope is that the ground can retain some of this moisture.

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  16. Make that FREEZE on contact. Wouldn't that be interesting if ice could melt on contact? :)

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  17. There is going to be a very long, slow-moving fetch of moisture-laden air riding into this system.

    As for "how" NWS mets do their forecasting, it is up to the individual. Of course a good met starts out big picture and works in and from top to bottom. But everyone isn't a good met...

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  18. I remember the 8+ inch storm we got in late April 2002, and it wasn't really that bad. Roads were slushy, but drivable. I drove around a lot that night and remembered thinking it was pretty docile storm. This storm, even if we get 10 inches probably won't feel like a January 10 inches. It will be slushier. Less will accumulate on sidewalks and roads. The ground's warm, so it will melt from below as well. Day time times above freezing. It won't be that bad. Just some good moisture for our area.

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  19. I knew that turning forty would be bad but seriously this is crazy! Makes me miss my Grandma and her story. Keep the info coming guys. I really love learning form you all.

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  20. This must be some sort of record for April....MSP will be under a winter storm warning for 42 consective hours(pretty long duration for April).

    MNPLOWMOWIDONTKNOWCO(I love that by the way,really funny),you will be plowing on the hard,with a healthy 6-10,even your boy Paul Douglas made a comment in his blog last night as "very plowable".

    In the I can't believe it department....NWS graphic has another storm depicted for this weekend,with a question mark on snow amounts.....are you freakin' kidding me!!!!!!!

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  21. I wonder how unhelpful models are this time of year. In other words, with a warm ground, high sun angle, temps above freezing, snow from Wednesday melting before the final tally is counted Thursday...I could see 10 inches not really looking like 10 inches. I'm guessing these are things that computer models don't factor in. Am I right on that?

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    1. That's an excellent question. Iowa State's meteograms look the same as they would during the dead of winter. The snowfall with compaction chart does not appear to take melting into account.

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    2. Let's use a slightly modified Paul DOuglas approach:
      take all models QPF and average it. Use a 10:1 snow ratio to get your expected snowfall.
      Cut it by 50%. That would be your estimated snowfall accumulation if it were winter.
      Considering it is April there will be more melting, however it seems that the bulk of the snow should come Wednesday night when the sun angle should not have a lot of effect.
      So maybe cut the total another 25%?
      That would be my forecast for MSP for this storm

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    3. I'm thinking along the same lines. To me, the only way real accumulation takes place is if the snow comes down with great intensity or occurs at night. I just think forecasters may be forgetting what an uphill battle it is to get serious accumulation (not just snow falling from the sky) this time of year.

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  22. I've seen some sleet mixing in with the rain downtown Mpls!

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  23. Lull? Or Bust? Or Dud?
    Storm not behaving as forecasted thus far,no forecast was calling sunny breaks and temperatures warming to 42 today!

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    1. Correction,currently now 44,keeps warming up.What a joke!Chilly yes,Arctic not!

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  24. Kare's afternoon forecast says 6 total for metro, including whatever we get Wednesday. If that verifies, assuming some will melt away before Thursday morning's snowfall, it will be much less impressive than many are forecasting.

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  25. The meat of the storm is just entering the southwest corner of the state now...

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  26. Wow.......my weather channel app has 8-16" from tonight thru Thursday! I'm having a hard time believing that.

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  27. Advisory upgraded to Winter Storm Warning...

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  28. Wow!.........."this could be the highest snow producer for much of the area for the entire season"....that's what the NWS afternoon discussion had to say,I urge all of you to read their afternoon discussion,its a good read with significant changes including more snow and to add insult to injury(if your not a snowlover)the last paragraph of their discussion talks about another heavy snow producer for parts of our CWA over the weekend.......simply incredible to be tracking snowstorms this time of year!

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  29. National Weather Service just stated in its update at 4:54 p.m. that snow should range between 10-15 inches from Redwood Falls through the Twin Cities!

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    1. Snow Miser...where do you read this on NWS Site - I don't find it????

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    2. Read the weather message under the winter storm warning....it says locally 14 or 15 inches of snow through the Twin Cities Metro!

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  30. Is this for real?! My NWS point forecast has me in a range from 9-19 inches of snow in the far west metro. At the same time, Kare 11 just showed the biggest swath of snow going over St. Cloud (40 miles north). Which is correct?

    I'm a big snow fan, but this is ridiculous. I had to dig my shovel back out!!!

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  31. New thread: http://www.minnesotaforecaster.com/2013/04/gobbsmacked-most-forecasters-see-hefty.html

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