Monday, November 12, 2012

Cold start to the week with a milder finish. No more snow for awhile..

It will be a cold start to the week after a weekend storm system brought widespread snow across southern Manitoba. Temperatures today will remain around the -5C mark with brisk NW winds making it feel more like -15 with the windchill.  For tonight, clearing skies and diminishing winds over a fresh snowpack will allow temperatures to drop to the coldest of the season so far, with -20C temperatures likely by Tuesday morning. Below normal temperatures will persist through midweek before a moderating trend towards late week with temperatures rising towards the melting point. In fact, long range models are indicating warmer than normal weather over the weekend into early next week with above freezing temperatures expected. In addition, no new snow is expected the rest of this week which will help in snow clearing operations from the weekend storm. All in all, a nice week ahead after a winter-like start! 

48 comments:

  1. 24.1C in Huntingdon, Quebec right now...

    RIDICULOUS!!!

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  2. Rob,

    I've heard rumblings of December possibly being warmer than normal.

    What are the latest indications on that front?

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  3. Here is a better snow cover analysis for our region. Note that the region of 10cm snow depth is actually just SE of Winnipeg based on actual observations. A large part of the RRV in N Dakota up into SE Manitoba will have bare ground fairly rapidly when temperatures climb to the freezing mark.

    Upper Midwest snow depth

    Tricky forecast for tonite's low. Saving grace may be down-slope SW flow that sets up this evening. Air will be returning around a polar high way down in the states with a long trajectory off of snow free areas. There is also the wild card of some higher clouds associated with a weak trough that will push thru (and swicth our winds to NW by tomorrow morning).

    If flow remains light and strong inversion sets up, low minus teens to -20 is possible in pockets here and there (with 925 hPa temps of -7 C). However, I am hoping we will have enough mixing with 925 hPa flow of 15-20 kts for much of the nite to keep us from totally bottoming out.

    Daniel

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  4. Anonymous.. I'm staying away from long range predictions more than a week out.. climatic signals aren't strong enough right now to give even an educated guess, at least for me. I see CPC is indicating better odds of above normal temperatures for us over the next couple of weeks.. but with our snowpack, it may be closer to normal. Beyond that though, I'm not going to speculate unless I see some stronger climatic signals taking shape.

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  5. Daniel..

    Yeah, if we had a light NW wind all night with clearing skies, -20C would be a slam dunk for the airport. I think we have a good setup tonight for a strong low level inversion developing. Temperatures above 925 mb are actually warming slightly tonight as cold core shifts to our east. Once we clear, radiational cooling off our fresh snowpack will strengthen the low level inversion, allowing for a decoupling of the surface winds. That should enable us to to drop towards that -20C mark, provided we stay clear most of the night. A light SW flow may spare the airport from hitting -20C, but -20C is possible in my area and spots outside the perimeter. RAP is giving a low of -17C for Winnipeg tonight.

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  6. Clouds hanging in there keeping our temperatures from bottoming out tonight.. also helping to keep up a southwest wind. Looks like we'll be clearing for a few hours after midnight, but more clouds upstream may prevent us from getting to -20C. Maybe -15C at the airport, a little colder outside the perimeter..

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  7. Crazy numbers from Eastern Canada...

    Huntingdon's (at the Quebec/Vermont border) official high was 24.5C tying their all-November record.

    What is even more insane is that the record is from November 28, 1990 (the 28th... CRAZY).

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  8. Gotta love that downslope wind... It's this wind that more than once prevented us from hitting -30°C last winter.

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  9. Only -10C on top of the Canadian Wheat Board.

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  10. Got down to -16C at the airport, -15C at my place, -11C at the Forks. A little more cloud and a little more favourable wind helped us from bottoming out to -20C overnight. Not too disappointed though :)

    Snowpack at my place is down to 18 cm this morning.

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  11. Got down to -16C at the airport, -15C at my place, -11C at the Forks. A little more cloud and a little more favourable wind helped us from bottoming out to -20C overnight. Not too disappointed though :)

    Snowpack at my place is down to 18 cm this morning.

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  12. Those sunrises the last few days are a welcome change. What is the nov total todate Link?

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  13. XWG is showing only 11cm. It's apparently the official Winnipeg source for the EC snow map (http://www.weatheroffice.gc.ca/data/analysis/352_100.gif) and the NAM snow depth data.

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  14. Rob...

    I have noticed the Pilot Mound AWOS wind is stuck at 00031kts.... dont know if it would be iced over (unsure about freezing rain that far northwest) or if something some techs can fix. I am unsure how your maintenance is done for the AWOS'S.

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  15. All the data I can find for Pilot Mound has values either as missing or flagged as erroneous. So they know it's broken already.

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  16. With a southerly flow developing tonite thru tomorrow afternoon, we'll see how warm we can get. Typically with a southerly flow and snow cover, temperature recovery is limited, but with bare ground that will open to our south quickly we may get a bit warmer than otherwise would be the case.

    Watch for a good burst of mixing late tomorrow between 7 and 10 PM as flow kicks around to WSW and briefly taps 925 hPa temps approaching +5 C. That will probably cause temperatures to spike to their high for the day. Will be short-lived however as cold advection continues thru the early part of Thursday, knocking temps back down.

    The roll coaster ride continues on Friday as southerly flow develops again and 925 temps rise to 0 C.

    Daniel

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  17. Dan - Am I correct in assuming you get your Canadian obs from MADIS? It may explain your problem at Pilot Mound. Here's the original data from WPO at 12Z today, and the version from MADIS:

    Original SA report:
    SACN86 CWAO 141200
    WPO SA 1200 AUTO8 M M M 229/-10/-11/17MM/M/ SOG 11 6016 20MM=

    MADIS METAR report:
    CWPO 141200Z AUTO 00017KT M10/M11 RMK AO1 SOG 11 6016 SLP229 T11021110

    The original SA report has winds from 170, with speed missing. The MADIS METAR has wind speed at 17 knots, and direction from 0. Bass ackwards. I guess their SA decoder doesn't handle the missing wind speed well.

    I'll alert the MADIS folks, but EC is discontinuing the SA format soon anyway.

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  18. Garth...

    Thanks for the info. I know there are certain sites in Canada that are still sent into the NWS Gateway in a SA format....WPO being one along with WGN (Gretna). The sites at Emerson and Sprague are not sent thru Gateway and thus not in our system.

    But yes would assume the MM for wind is causing a problem and how it is decoded.

    So I take it that obs such as WPO will soon be a MTR like the YWG and YBR??? Seems as if NWS comms has trouble reading some of the sties that start with W versus Y.

    Thanks

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  19. Dan - Yes, I hope the SA reports will be available as METAR instead. All I know for sure is they'll be available as a new XML format (SWOB Met-ML) on Environment Canada's datamart. Rob probably knows more about this.

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  20. As warm as +9 C down in Fargo today, with essentially no snow cover south and east of Grafton ND. Area of pesky stratus and fog advecting up from Grand Forks, and will arrive shortly for this evening. Further west, not much evidence of warmer temperatures surfacing out over Saskatchewan (a couple readings of 1 C). We might squeeze out another couple of degrees, but nothing dramatic before falling back overnite.

    Quick shot of cold advection and high pressure tomorrow, before return flow sets up overnite Thursday.. stabilizing our temperature drop. Persistent southerly flow will continue right thru until the beginning of the work week. Edge of snow pack should continue to steadily erode north over the course of the next few days.

    Daniel

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  21. Hopefully we can get some overnights just above zero, that could put a good dent on this white stuff.

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  22. Not everybody wants the snow to disappear!

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  23. Garth/Rob

    In regards to the SA and METARs.... another question.

    There are SAO sites in Canada that are in MADIS but are not sent in through NWS Gateway and thus we cannot view them unless we go to MADIS.

    Sites such as Emerson (WEX), Sprague (WSU), Pinawa (WEA), Melita (WEI), Shoal Lake (WUT) and others. Now will these sites start sending out a METAR obs as well do you know?

    --Dan

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  24. Dan..

    I'll check with our monitoring guys and let you know..

    Rob

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  25. Visible satellite imagery nicely shows extent of snowpack across southern Prairies and far northern plains. Snow still pretty deep across southern SK and western MB from weekend storm with 25-40 cm snowdepths still being reported. Snowpack is in the 10-20 cm range over the RRV, more in the western RRV and YPG area, less in the east.. with snowdepths falling off sharply towards Lake of the Woods (only 1 cm snowdepth in Kenora) 15 cm snowdepth at my place this morning and 11 cm at XWG.

    Other than the far NW, Minnesota is nice and bare, so as Daniel noted, best bet for warming winds for us will be with a SE flow, rather than westerly wind which still goes over an expansive snowpack right to the Rockies.

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  26. Hello Rob,
    I am asking you a question for the first time, but have been watching your blog for a while now.
    I live in the Amber Trails end of town, and measured 33 inches of snow, is that possible, since most places reported in the 20's?

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  27. Anon

    I would suggest if you measured 33 inches or prob cm's it would be either a snow drift or snow blowing off a roof and filling an area.

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  28. Anonymous.. I assume you mean 33 CM, not inches. Most places in Winnipeg measured between 20-25 cm (8-10") with the weekend storm. It's certainly possible that you measured 33 cm in your yard, as some areas may have drifted a bit, or there was blow off that accumulated more in a sheltered spot.

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  29. LOL! Just saw Jim Slater of the Jets do the weather on Winnipeg CTV news tonight! So that's what unemployed hockey players have to do to make some money!! :)

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  30. Jim did well. It made me miss the days of Stan Kubicek on CKND - no nonsense, no quibbling about tenths of a degree, no bragging, just an enjoyable (and often humorous) forecast report.

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  31. Rob,

    Do you think the temps over the weekend and into next weekend will actually climb above zero as forecasted given the snowpack that still exists?

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  32. I think above freezing temperatures are likely, even with our snowpack. If we didn't have snow, we'd probably be looking at temperatures of +7 or +8C this weekend into next week... but our snowpack will shave a good 5C off those temps. Still nice though.. and still no new snow for awhile so our snowpack will continue to go down.

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  33. Rob has the snow depth in the city gone down due to the pack settling/compacting? That much couldn't have melted with the temperatures being below freezing.

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  34. With such warm temperatures aloft (above 0C), and 925 mb - 850mb winds at 70 to 90 km/h, I would expect above freezing temps the surface today, even with the snow. Shows how little I know apparently.

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  35. That 50k wind is just awful today. Hopefully the winds drop off.

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  36. Updated NWS CPC outlook for the DJF period issued Nov 15th now has ND/MN in below average temps for the winter period. Demise of the El-Nino and other factors the reason.

    http://www.crh.noaa.gov/images/fgf/Winter2013/Nov_15_DJF_Outlook.jpg

    Here is a very detailed outlook and explanation issued by our office...

    http://www.crh.noaa.gov/news/display_cmsstory.php?wfo=fgf&storyid=89389&source=0

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  37. Anonymous..

    Yes, the decrease in our snowpack is mainly due to compacting/settling. There's likely been some reduction due to sunshine and wind, but mainly it's just been the settling of the snow we received from the weekend storm.

    Depending on the water content of the snow, snowpack can go down quite a bit even with temperatures below freezing. A dry and fluffy snow can compact rapidly, while a heavy dense snow will take longer to settle (as long as it's below freezing). Strong winds will pack the snow down and harden it.. almost like concrete if it's cold and windy enough.

    The fastest way to reduce snowpack is with above freezing temperatures both day and night, especially if accompanied by above freezing dewpoints and/or rain or drizzle.

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  38. Thanks for the update Dan.. I don't envy anyone trying to predict what winter will be like this year. Variable will be a pretty safe bet I think!

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  39. Rob and others...

    Yes long range always a tough challenge...look at last year even with a dominate La Nina strong blocking over the arctic and elsewhere gave us the mild winter.

    Our local long range expert gave us an office update today and said the latest CFS and other CPC guidance is indicating this mild stretch will last into late Dec then it will turn stormy around the holidays and then predominately colder than normal Jan-Feb. We will see.

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  40. Must be a dome of cold air sitting over the airport... All the way up to +1°C in southern parts of city. Similar between -2 and 0 in most parts.

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  41. Yeah, that is sure strange... - 4.8C at the airport now as of 2 PM and +1.3C at the forks....+1.1C here at my place in Windsor Park and pretty much 0C or +1C everywhere across town as well and it sure feels very pleasant outside today....light winds and some filtered sunshine.

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  42. I see temps dropped a little at the airport...now -5.3C at 3PM. Also dropped a bit at my place here in Windsor park as well..now - 0.8C at 3PM. I've also noticed a drop at Rob's place as well...from 0.5C at 2PM to now -1.9C at 3PM.

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  43. Wow, temps dropping quickly now across much of the city...now -2.3C at my place in Windsor Park at 3:20PM, -1.5C at the forks and -2.5C at Rob's Obs. So basically it was 0C to +1C pretty much across the city today except for the the Airport's reading of -5C. very strange indeed but it sure felt more like that +1C earlier today rather than -5C that's for sure.

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  44. Weak inverted trough came thru early this morning, associated with a disturbance moving into the northern plains states. Switched our flow to the NW off of the deeper snow pack, and caused temps to crater at YWG. Inversion out there never really broke down today, whereas in most other areas it did (as noted). Again goes to show how unrepresentative that station can be sometimes.

    Models having some difficulty resolving the surface pressure pattern around the trough. This feature will wash out at some point, and broad SE flow takes over again by tomorrow. A lot of variability tonite for lows, with temperatures plunging in some spots with light and variable winds until the return flow takes over.

    With that SE wind trajectory tomorrow, and 925 hPa temps progged at 8-10 C over southern Manitoba by afternoon.. we could get rather warm and really diminish our dwindling snow pack. Guidance is variable: NAM, RGEM, GGEM are just barley above freezing for a high, whereas SCRIBE (both regional and global) gives highs of 4/5 C. I think given the set-up tomorrow some of the higher guidance may end up working out.. especially in the city and areas just to our SE (where even 6-7 C may not be out of the question).

    Will also have to watch temps overnite Sunday.. with some guidance suggesting temps staying over zero the entire night.

    Daniel

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  45. PS..

    One wildcard will be potenital for fog formation overnite.. which would then advect northwards tomorrow morning. Given the SE flow however, best chance for getting fogged in tomorrow will be the western RRV, with deeper snow pack and up-slope trajectory.

    Daniel

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  46. Dense fog has developed at the airport this evening with vsby down to 1/4 mile as of 10 pm.. Looks pretty localized as city webcams show good vsby elsewhere across the city currently.

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  47. NAM shows only 1cm of snow left on the ground by Wed afternoon. Seems a little extreme.

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  48. My snowdepth is down to 12 cm as of this morning, and looks pretty solid. I agree that going down to 1 cm by Wednesday is unlikely, without some rain and consistently above freezing temperatures day and night. Perhaps 5-7 cm snowdepth by Wednesday is more realistic.

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