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Wednesday, December 30

WEEKEND LAKE EFFECT DISCUSSION

Written by: News 8 Weather Team

First and foremost, we'd like to discuss the aim of this blog. We created the weather blog in hopes of providing the public with a behind-the-scenes, more in-depth look at what our thoughts are about upcoming or occurring weather. We provide insights as to model data, as well as our own "gut" feelings. We've all got some experience and reason for the thoughts we put into our forecasts.

Recent comments have compared our forecasts to other stations, or criticized our accuracy. We aren't competing. Our forecasts are our forecasts, and no one elses. Weather forecasting is and will NEVER be an exact science, therefore you will always see variations from one station (or one meteorologist) to the next. And yes, we will have errors. There, we said it!

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Okay, now to this weekend's lake effect. Potential is definitely there, there's no doubt about it. Nice cyclonic curvature overhead, an 850 mb low to our east, and a favorable wind direction.

I guess what I want to clear up is the size of this event. We'll all get a good dose of snow, that's not the question at hand. It's that we won't see "historic" or "major" snow. The ideal direction for blockbuster lake effect here is northeast as mentioned before. We've had plenty of occasions where good snow results from a northwest wind, and this weekend will probably be one of them. So while you may need the shovel, you won't be needing your next door neighbors 26 hp John Deere snowblower to escape the driveway.

I took a look at the 1000-850 mb average RH, and its decent, but not impressive. In comparison to the lake effect "event" (if you can call it that) of a few days ago, this next go-around will be something much better, as far as moisture characteristics go. Slower winds will be able to grab more moisture, and the temperatures aren't quite as cold, which means that the air has more moisture-holding capability.

Why aren't we posting the when/where/how much yet? It's too early. The models are really fighting over the placement of this low off the northeast coast, and even then, the thing takes a little joyride around the northeast maritimes. The direction of the winds will have a huge bearing on snow location and amounts. We'll keep you posted.

As I finished this, the data for the 18z NAM came in. Two thoughts:



This is for late Friday night. Good northwest flow, which could set us up with an upstream connection to Lake Superior. Several hours of decent lake effect favoring northwest/southwest areas of Rochester. But it moves quickly.



This is late Saturday/early Sunday morning. This could be interpreted two ways. One, a direct north wind could all but kill the lake effect. Plus, its a pretty swift wind, further limiting boundary-layer moisture. Or two, if this shifts even a little bit, BINGO, there's our northeast wind.





6 comments:

  1. For the Friday evening event, what do you mean by snow favoring "northwest/southwest" areas of Rochester?

    ReplyDelete
  2. If the north flow does indeed setup, and kills the LES, how long will this flow last before it either shifts NW or NE? I ask because I hope that if it does go north, it won't stay that way for too long so that the majority of the "event" is greatly reduced to near nothing.

    ReplyDelete
  3. Here is the forecast discussion out of Cleveland, OH. They seem slightly worked up by the potential LES on a NW wind, even suggesting Warnings to be posted. We'll be even closer to the moisture source off Lake Ontario. Do you think headlines will be needed for Monroe County?

    LARGE UPPER LEVEL LOW WILL SPIN OFF OF THE NEW ENGLAND COAST INTO
    WEDNESDAY. THIS WILL KEEP A COLD WEST TO NORTHWEST FLOW ACROSS LAKE
    ERIE WITH LAKE EFFECT SNOW ANTICIPATED SUNDAY THROUGH WEDNESDAY. AS
    PIECES OF ENERGY ROTATE AROUND THE LOW THERE WILL BE FLUCTUATIONS IN
    THE LOCATION AND INTENSITY OF THE SNOW SHOWERS. AREAS OF SNOW MAY
    SPREAD TO ALL OF THE AREA ON SUNDAY AS ONE OF THESE TROUGHS ROTATES
    ACROSS THE REGION.

    SNOWFALL AMOUNTS THROUGH THE PERIOD LOOK AS IF THEY WILL BE
    SIGNIFICANT WITH LAKE EFFECT SNOW WARNINGS FOR THE WEEKEND. WINDS
    MAY BE FAR ENOUGH AROUND TO THE NORTHWEST FOR THE LAKE EFFECT SNOWS
    TO AFFECT LOCATIONS AS FAR WEST AS ERIE…HURON AND LORAIN COUNTIES.

    THIS AIRMASS LOOKS TO BE THE COLDEST WE HAVE SEEN THIS SEASON. HIGHS
    WILL GENERALLY BE IN THE TEENS TO MIDDLE 20S. LOWS LOOK TO BE IN THE
    SINGLE DIGITS AND TEENS

    ReplyDelete
  4. To the 2nd commenter who ask, "how long will this (North Flow) flow last before it either shifts NW or NE?" - Right now we don't know, you can't accurately forecast the wind directions and say how long they will stay that way. Just go back to early December when we got the long single band of snow from Lake Erie. Everyone though once that band dropped south of Rochester winds would stay westerly well that changed and there was no indication that would happen and we were talking hours not days.

    To the 3rd Commenter, I forecasted lake effect snow off of Erie for several years before coming to Rochester and I can tell you this, you can't extrapolate their forecast for ours. They will be dealing with similar but different set of conditions. From what I saw yesterday and this morning it appears they will get a little bit more help from some better upper level dynamics. If winds are northwest to north for them they will also be aided by a long Lake Huron fetch along with Lake Erie
    To answer your question, do I think the NWS in Buffalo will issue advisories or warnings for Lake Effect snow across Monroe County. It is definitely possible. They issued an advisory for Tuesday's event which didn't produce much of anything.

    To the first commenter, since I didn't write this post I don't think I can tell you what Bob, meant I think with the winds coming out of the Northwest the snow could set up across Monroe country from the northwest to the southeast and then points east. Again time will tell and all players need to get into the right positions but it will indeed be cold and there is enough here to say we will get lake effect snow and for a good period of time through the weekend and into next week.

    ReplyDelete
  5. Brian,
    Thank you so much for taking the time to answer all of our questions. It helped clear up a lot of things. Also, to the entire News 8 / Fox Rochester team, have a happy new year. You guys and gals are, by far, the best team in Rochester....And don't let any irritated commenters on this blog get to you, they're just frustrated by the weather and taking it out on the mets.

    ReplyDelete
  6. Thanks yuou Bob and Brian and Scott. No other Weather station does a blog like you guys do. This is great way to talk weather and I appreciate it. I know many of the bloggers, including me, get frustrated because we all love snow. We seem to take it out on you guys, which we should not. You cannot control the weather. Forcasting weather in Western, Ny is very difficult and you all do an awesome job. We will see what happens with the lake effect this weekend. Thanks for thge 2009 year in reveiew. That was great. Stay encouraged and God bless you all for a great 2010. Maybe we will get a good blizzard around here. Thanks

    ReplyDelete

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