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Friday, December 10

WHY YOU SHOULDN'T BE EXCITED ABOUT BIG SNOW THIS TIME

Written by: Bob Metcalfe

Yes, this coming storm will be problematic. But it won't be a "feet and feet of snow" type of storm. It doesn't possess the right characteristics... one of them being a lack of cold-enough air.

Image shows the NAM forecast "precip conditionals" which is the best guess for type of precipitation falling at the surface. This is for 12z Sunday (7AM) Notice how our area falls smack dab in the middle of the "I'm really not that sure" zone? This means that there is consistent thought and run after run backing that this event will start quite possibly as rain, with a mix and sleet likely during the transition hours Sunday night. Therefore, frontside snow potential (the east side of the storm) is fairly limited. That isn't to say that the roads won't be terrible though as is always the case with any mix of icy precipitation. I expect that at the peak of the precip transition from rain to all snow there will be very poor conditions. Not a major icing event or anything like that, but slick roads nonetheless.

Our biggest impact is after the storm heads east of the area. Of course we all are looking at the backside potential for lake effect snow. As has previously been mentioned, the fetch (or time for air spent over the lake) isn't ideal. Strong winds will also limit that time further. However there will still be lake snow occurring. Placing these bands now would be nearly impossible as we have to wait for the storm to pass before making any assumptions about sustained wind directions. The cold nature of this time frame will create those huge, light and fluffy flakes that seem to wreak havoc on visibility. Factor in those strong winds and you've got blowing/drifting snow that will probably be our biggest problem on Monday and Tuesday. So while this will be a problematic lake effect event, our hopes for 3 feet or more are exactly that: hopes.

22 comments:

  1. Thanks Bob but the storm is still over 48 hours away. You never know with a slight change of track who knows. The winds I feel are going to be very strong on Monday and Tuesday no matter what. This will cause big problems with any snow that falls.

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  2. That is correct, but the models are converging on an idea more and more, so forecast confidence increases. This could absolutely shift and totally change things. Crazier things have happened. But its just too darn warm ahead to believe that we'd stay as all snow and this west to east track doesn't usually give us a great pure snow storm.

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  3. Other forecasters are talking about times of heavy snow after the storm passes from Sunday night and Monday. Is that not true?

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  4. WHAT HAPPEND TO THE 1-2 FEET CHANNEL 8 WAS PREDICTING YESTERDAO FOR THE ROCHESTER AREA. AHS THAT NOW CHANGED? LAST NIGHT SCOTT STATED THAT IT COULD GET BAD IN ROCHESTER AND COUNTIES BORDERING THE LAKE. IT SEEMS NOW YOU ARE BACKING OFF ON THAT.

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  5. THE NWS IS STATING RAIN TO START AND THEN SOME SNOW TO FINISH. THEY ALSO STATE THAT LAKE EFFECT COULD MORE SIGNIFICAN NOW BECAUSE THE MODLES ARE BACKING OFF ON THE COLD AIR. THEY ARE SAYING THE AIR WILL BE WARMER ON THE BACKSIDE OF THE LOW CAUSING BETTER LAKE EFFECT POTENTIAL. THE FLOW LOOKS TO BE NW WHICH MEANS WE COULD BE IN FOR ANOTHER LONG LASTING LAKE EFFECT EVENT FOR ROCHESTER AND PINTS EAST.

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  6. This storm is definitely really hard to predict! I think the whole thing will be now cast! You cant answer question like how much of the cold air will stay after the cold front moved through? What time will the rain change back to snow?
    And lets not even take about lake effect! How can you even start talking about this when the last week perfectly showed that you cant even predict it a day before it strikes!?
    So we should just wait until the storm is 24h hours away...

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  7. I said there would be snow after the storm. I simply said not to expect 3 feet! There will absolutely be locations with over a foot of new snow.

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  8. By these posts I think I'm being misinterpreted. Perhaps I should have said "don't be excited about SYNOPTIC snow". I meant that it won't lead with feet of snow, rather the mix. The lake effect is a different story Monday and Tuesday. Hope I cleared that up for you all!

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  9. Here is an exerpt from the National Weather Service Forecast Discussion. Per their discussion, conditions are looking better for a significant snow event. They even called out Rochester specifically:

    BUT THE LARGE SCALE
    PATTERN GENERALLY SUPPORTS NORTHWEST FLOW WHICH WOULD TARGET AREAS
    SOUTHEAST OF LAKES ERIE AND ONTARIO ONCE AGAIN...POSSIBLY INCLUDING
    METRO ROCHESTER. IF THE WIND DIRECTION AND QUALITY OF LOW LEVEL
    MOISTURE IN THE 00Z GFS VERIFY...THIS COULD BE ANOTHER SIGNIFICANT
    AND LONG LASTING LAKE EFFECT EVENT.

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  10. Another thing you have to remember is to look for wind shear. This last storm had virtually no shear (turning of the winds with height)which is ideal for good lake effect. If we get a lot of shear, you're putting strain on well-developed bands. Something to think about...

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  11. The bottom line is that you can't make specific lake effect forecasts when you have a huge synoptic storm between you and it.

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  12. I find it hard to believe based on the models that when the storm goes by that we will not at least get 8 inches of snow just from the wrap around from the storm that is not counting possible LES.

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  13. 8 inches from wrap around? Okay, based on what? At least back up your thoughts with some information that leads to that thought.

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  14. Looks like we'll spend much of the time in the dry slot when it does change over to snow.

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  15. Here's the deal...last time Scott went out there and forecasted 1 to 2 FEET of snow. And that is EXACTLY what occurred. This system is very complex and there are a lot of moving parts, as they say. We probably won't have a solid, very high confidence handle on how things will play out until Saturday nights model runs. By then, the storm will be maturing and no longer something that hasn't even materialized yet. You can be sure that if and when things start looking "interesting" for the Rochester metro in terms of major snow (specifically lake effect), Scott and his team will ramp up the detail.

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  16. Well said in the last post. It just seems like the city and east suburbs like Pittsford, East Rochester and Fairport never really get a great deal of LES. Guess time will tell and as you said Saturday night will give us the most accurate data. Thanks

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  17. Does anyone know what the 10:30 GFS showed?

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  18. Not much to say about the synoptic storm itself. Slight shifts in the track, but nothing significant. BUT...and here's the potential more important part...the latest 12z GFS continues its trend of not being so extremely cold. That is very favorable for better quality lake effect snow developement. It also makes the high to our NE more expansive which keeps the moisture pushed back into our area a bit more. And, the winds look to be not quite as NNW as before. All in all..it continues to look good for a potentially major lake effect event similar to the one we just had.

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  19. Thanks for the information but LES is not that exciting for the city and many suburbs around the city. This last event left many more places with little snow as compared to ones who were hit hard. Was hoping for some good synoptic snow from this storm as many thought earlier in the week.

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  20. Winter Weather Advisory has been issued for entire area for freezing drizzle overnight

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