Sunday, November 04, 2012

A little rain Monday evening then a quiet week. Winter storm threatens southern MB by weekend..

Weather map for 6 pm Monday
showing band of rain and wet
snow pushing across southern MB
A warm front over northern Alberta will push into southern MB Monday bringing a band of precipitation ahead of it. The bulk of the precipitation should fall as rainshowers through the Interlake Monday afternoon into the RRV by evening, with some wet snow mainly north and east of Lake Winnipeg. Further west, the warm front will likely result in some patchy dense fog developing overnight into Monday morning across SW Manitoba especially towards the SK border.



GGEM map for Sunday morning
Nov 11th showing strong
system affecting southern MB
 
After Monday, things look generally quiet over southern MB the rest of the week with generally fair weather and seasonable temperatures. By next weekend however, long range models are hinting at a potentially significant winter storm affecting southern MB Saturday into Sunday, with the possibility of heavy snow and strong winds. The storm is still a ways off and there are track and intensity differences from the various models that will have a major impact on forecasting who gets snow and how much. So at this point, all we can say is that the POTENTIAL for a significant snowfall of 10 cm or more exists for much of southern MB next weekend, including Winnipeg. I'll be posting blog updates on this developing situation as the week progresses.  

Meteogram showing various model
output for Winnipeg including
6 hr precip amounts (bottom)
 
The chart to the left is a meteogram plot showing various meterological parameters for Winnipeg out to 10 days from UQAM's excellent Meteocentre.com site.  The meteogram is interesting since it plots various model solutions (such as the GFS, UKMET, ECMWF, GLB, etc) as well as previous model runs. It's an effective way to see how models are agreeing, and trends in the expected weather conditions. The meteogram plots MSL pressure (top), 850 mb temperature (center) and 6 hr precip (bottom) Updated Winnipeg meteograms available after noon (12Z meteogram) or after 12 am (00z meteogram).   Meteogram data also available from SpotWx.com            

26 comments:

  1. Lol new GFS suggesting an ice storm with 10 mm of freezing rain... Will be interesting to say the least.

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  2. Hi Rob,

    I've also noticed that the new GFS model run is showing freezing rain storm as well.

    Do you see that being a possibility?

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  3. Interesting.. that must mean GFS is leaning more towards the Euro with a warmer solution for us (a track further north and west) which puts heavier snow west and northwest of Winnipeg and gives a better chance of mixed precip or even rain over Winnipeg/SE MB before changing to snow. We'll have to see if this is a consistent trend among all the models, as well as subsequent runs.

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  4. it's almost incredible that will all the colder air that's expected to move in later this week and with all that cold air to the west that it would actually be warm enough for rain. Will be a very interesting week watching this situation unfold and what the models do day by day on this

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  5. According to EC, it won't be warm enough for rain with highs of -2C and -4C Friday and Saturday, but obviously that may change this week once models get a better handle on this storm

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  6. GEM and GFS are giving about 25 cm of snow to Winnipeg through Saturday, while the Euro is bringing about 20 mm of mixed precip (freezing rain/ice pellets) along with snow (maybe 10 cm or so) GFS has trended higher with 850 mb temperatures over us Saturday so phase may be an issue for RRV/SE MB which will influence snowfall amounts in those areas. Looking more and more like there will be a winter storm of some sort to deal with by the weekend, although snowfall amounts still a tricky issue given uncertainty in storm track and temperatures aloft. Stay tuned..

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  7. i've noticed EC is calling for snow Friday then a chance of flurries Saturday and Sunday with temps definately cold enough for snow. Very strange considering this storm is expected Saturday into Sunday unless that's changed.

    One thing about these models is they are being very consistent....GEM and GFS sticking with snow and Euro with mixed precip then snow... I guess we will have to wait see which one wins this battle. very interesting

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  8. Rob, What is the NAM showing as far as this storm is concerned?

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  9. Re: Snow on Friday. GGEM is faster with this system bringing in snow over RRV Friday morning, while the GFS and Euro don't bring it into Winnipeg until Friday night into Saturday. Thus, EC's "snow" forecast for Friday. This leading band of snow will likely spread over SE SK/SW MB first before moving into Winnipeg/RRV. There will be timing differences with the models before things become a little clearer over the next few days. Saturday still looks like the stormiest day..

    The NAM is a higher resolution model that only runs out to 84 hours.. so we're still a couple days away from getting NAM guidance on this storm.

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  10. Either way it's looking pretty much like we are in for some kinda of stormy weekend...Too early for this, but then some might argue it's always too early for winter

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  11. Yes, it's looking that way.. I think it's a good bet we will be getting snow later Friday through Friday night into Saturday, winding up Sunday. Latest 12Z GGEM has slowed down the snow into Winnipeg Friday, bringing the heavier stuff in Friday night.

    The question remains.. how much? 00Z NAEFS ensemble guidance has ramped up the numbers to a 50% chance of up to 18 mm of precip with this event, with a 25% chance up to 35 mm, and a 25% lower threshold of at least 8 mm. If all that QPF is snow, then you're looking at 20-30 cm for us, but if it's mixed with other precip types (like ice pellets or freezing rain), snow amounts could be half that. But whatever the case, it's looking more and more likely that we have our first winter storm on the way.

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  12. Rob, are we expecting strong winds with this system and if so how strong might the winds become?

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  13. 12Z Euro today has come more in line with the GGEM and GFS with colder temperatures aloft over Winnipeg, making this more of a straight snow event for us. They're showing around 30 cm of snow for Winnipeg starting late Friday, continuing through Saturday and Saturday night before tapering off later Sunday. GFS has also trended colder aloft with today's run. So we seem to be getting a growing consensus that this will be mainly a snow event for us, with significant accumulations of 20-30 cm possible for Winnipeg and much of the RRV, starting Friday afternoon/evening, increasing through Saturday and winding up Sunday. That's what the models are saying now.. we still have to wait and see if they maintain this consistency over the next few runs, or diverge again. But right now, they're all saying a pretty good snowstorm setting up for the RRV.

    As for winds, currently models are suggesting northerly winds of 30 gusting 50 km/h, but there could be higher gusts if this storm is a little stronger. That could present blowing and drifting problems.

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  14. Area of rain over western MB spreading east.. should be moving into Winnipeg by 5 or 6 pm. Looks like about 5 mm of rain this evening before it tapers off around midnight. Rain may mix with or change to wet snow mainly north and east of the city this evening with a slushy coating of snow possible in some areas. Temperatures should remain mild tonight staying generally above freezing.

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  15. Moderate gusts at best....I guess there will not be a tight pressure gradient around low given wind gusts of only 30 to 50 kmh are expected, but any strong low pressure system you never know...let's face it though, you don't need any wind to cause travel problems when 20 cm or more snow falls.

    Will be interesting to see what the NAM indicates in the a couple days from now.

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  16. It's snowing here in the south end, been quite heavy past little bit.. Airport still saying rain..

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  17. Wet snow falling here in Windsor Park tonight...but nothing compared to what's coming this weekend.

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  18. Working mids... but I see the 00z GEM is quite colder now Fri-Sat and has main snow a bit farther south over ern nd into far SE Manitoba and northwest MN. It appears the GEM is keeping trough in western U.S. more positively tilted and less strong on the surface low. American Models and the European have a stronger 500 mb low and a bit stronger surface low and keeps main snow more tied with 500 mb low from eastern Montana and northwestern ND into Sask and Western-Central Manitoba.

    Will see how model trends the next 24 hours. Issues right now is push of cold air southward Thursday with high to the north...and how far boundary can get and also strength of 500 mb low and if 500 mb trough is negatively or positively tilted.

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  19. Dan.. Yes, 00Z GGEM came in more progressive with a weaker low tracking further east, just clipping SE MB with snow. GFS and Euro stronger and further west, bringing greater snow chances over southern MB. I'm going to discount last night's GGEM and go with the GFS/Euro which have been trending towards the further west track. In fact, 06Z GFS was even stronger and further west than previous runs, tracking low over Kenora with mixed pcpn over RRV/SE MB and heaviest snow over SW MB into the interlake. Hopefully we get a clearer consensus over the next couple of days..

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  20. this is almost starting to look a potential miss for us here. one day it's mixed precip with lesser amounts and heavier snow to the west, the next day it's a potential big snowstorm of 20-30 cm for Winnipeg, now it's back to mixed precip for RRV/SE MB and heavier snow to the west again. I've notice that NWS has posted winter storm watches in montana and special weather statements in western north dakota...nothing posted for eastern north dakota and minnesota...interesting.

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  21. It seems models are trending back to the mixed pcpn in RRV/SE MB and heaviest farther west again like it was saying on the weekend. not much consistency within the models of a big snowstorm of 20-30 cm here in the RRV/SE MB.

    Rob, what do you personally think on how this storm is going to evolve?

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  22. I will have an updated blog post with the most likely scenarios coming up.. stay tuned..

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  23. Its very frustrating with the bouncing around of these systems especially when you are in business that relies on weather forecasting. I also want to say I think this fall has been one of the gloomiest falls I can ever remember. It feels like 6 weeks since we last had a day of sunshine.

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  24. Thanks, Rob.

    My feeling is that we get mixed pcpn here in the RRV/SE MB then a change to snow given us less than 20-30 cm but either still a mess to deal with.
    We'll see what happens.

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