Saturday, April 14, 2012

Strong storm system south of border to impact areas south and east of Winnipeg Sunday

A strong storm system developing over eastern Colorado today is expected to spawn an outbreak of severe weather over the central American Plains today with a high risk of severe thunderstorms especially though Kansas, Nebraska and Oklahoma where violent long tracked tornadoes are possible. The storm system is expected to track into South Dakota tonight then into Minnesota and Wisconsin on Sunday. Widespread rain is expected on the northwest flank of the storm with areas of heavy rain possible over the Dakotas tonight into northern Minnesota Sunday. This area of rain will likely just graze southeast Manitoba Sunday with some rain likely towards the US and Ontario borders. Sunday will also see increasing northerly winds over southern Manitoba which will draw in colder air through the day as temperatures fall into the single digits. In fact, there's a chance that rain may change to snow on the backside of this storm system Sunday night over northwest Ontario. Near to below normal temperatures are likely through the upcoming week over southern Manitoba.

37 comments:

  1. The afternoon is turning out not that bad!

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  2. 15mm in South St. Vital yesterday.

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  3. High wind watch issued for area's south of the border, along with the potential of two inches of rain!!

    Take a look at the radar out of Kansas right now for some TEXT book tornadic supercells!!

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  4. 1008PM Warning On the ground in Clearwater to Wichita.

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  5. Watching CNN for the tornado emergency for Wichita.

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  6. SWAT chasers got hit by the tornado in southeast Wichita about an hour ago. They were streaming live here

    http://www.tornadovideos.net/pages/full_screen/

    I just happened to be watching when they got hit! Don't be surprised to see their video all over the media tomorrow, they're very busy on their phones at the moment :P

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  7. -10 C and a 40 gusting to 60 wind. That wind chill is gonna be cold tonight. Best get out the winter parka!

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  8. Jeff Masters Blog posted #1 picture today is Semi from Steinbachs "Penner International" flipped on its side on I29 in Iowa.
    http://www.wunderground.com/blog/JeffMasters

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  9. 50-75 mm of precipitation south and east of a Fargo to Fort Francis line.. Sisseton, SD came in with a whopping 100+ mm. Fortunately we avoided the 10-25 cm of snow as was reported over N Minnesota and Ontario. And If you think our temps are bad.. just look at the north shore of L Superior, under the cold core and fresh snow cover. Many readings this afternoon between -5 C to -10 C. Ouch

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  10. We didn't do too bad after all 4C.

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  11. American guidance considerably colder than SCRIBE for tomorrow's system. They show 925 temps as low as 0 C north of a warm front. With clouds and precipitation moving in by afternoon, we would be lucky to reach 3/4 C under that scenario. Looks like a focused area of strong lift, with nose of 30 kt LLJ and possible frontogenesis (leading to some banding). NAM is stronger than GFS with forcing, and shows more dynamic cooling. NAM would have mainly wet snow for tomorrow while GFS has rain mixing in with some wet snow on the back edge of precipitation.

    Tricky situation because system will be intensifying as it moves east, and taps a stronger LLJ and moisture advection. Possible convection in N Dakota tomorrow evening ahead of the cold front. They should be basking in the warm sector during the day with temps in the 15-18 C range.

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  12. 31.4C today in Huntingdon, Quebec (Quebec/Vermont border), 66 km south of Montreal.

    2 other stations in Southern Quebec were above 30C. Those are the first three 30C+ temperature readings in Canada for 2012.

    Humidex of 34C in Huntingdon as well which is also the highest humidex recorded in the country for 2012.

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  13. Next area of precipitation over SE SK this morning falling as snow right now. Area of precip will be moving eastward into SW MB this morning, and into RRV this afternoon.. reaching Winnipeg between 3-6 pm. By then, it will be rain for us as temps climb to 7-8C, but cooling off to 3-4C as rain moves in with lower dewpoints. General rainfall amounts of 5-10 mm being advertised from the models for Winnipeg between 3 pm and 3 am.

    Specifically from last night's runs..

    RGEM.... 11 mm
    GGEM.... 7 mm
    NAM .... 13 mm
    ECMWF... 3 mm

    NAEFS ... 5 mm (ensemble)

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  14. RGEM seems a little over zealous to me...unless a little convection gets going on the nose of the LLJ...

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  15. Yeah, it's the higher res models that are giving the higher amounts.. so I think they're hinting at some embedded convection developing. Some hints of it right now over northern ND and SE SK, but nothing major. NAM is also colder with the precip, with freezing levels dropping to 1000 ft AGL after midnight in Winnipeg.. possibly changing any lingering rain to wet snow by then, as alluded to earlier by anonymous.

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  16. Area of low clouds last night kept temperatures warmer.. giving us a head start today. We'll see where we level off as more clouds move in ahead of the system.

    NAM sticking to its guns bringing in stronger forcing and 925 temps of 0 by this evening. It shows surface temperatures dropping off to 0/1 C by around 10 pm and now gives us 16 mm total precipitation with possibly 5 mm in the form of wet slushy snow. RGEM guidance is warmer keeping it all rain.

    CMC does not reject NAM scenario.. so it seems to be a question of what guidance you believe. My own gut feeling.. precip will move in as rain and switch over to wet snow in any heavier bands and forcing around 10 PM. Its also worth noting that models are a little bit slower in bring in precip.. which may favor higher totals since the system will have more time to tap LLJ and moisture.

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  17. Didn't see your comment Rob. I think the regional models are picking up on a band of frontogenesis, that will set somewhere around the TransCanada. There is also uncertainty in how much the system can intensify before reaching here..

    Daniel

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  18. Will be interesting to see how low the freezing level gets this evening as to whether or not we change to snow here in Winnipeg/RRV. Sometimes, the slightly lower elevation of the valley is all it takes to keep us as rain, while higher elevations outside the valley change to wet snow. A couple hundred feet elevation is sometimes the difference between rain and snow in these shoulder season events.

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  19. Precipitation band closely associated with region of 700 hPa frontogenesis, as seen on SPC mesoscale analysis. The RUC model driving the analysis, along with NAM, also picking up 925 cold core below zero (no doubt associated with heaviest forcing and precip). Unfortunately there is a dearth of recording stations in eastern Saskatchewan and western most Manitoba.. any reports from this area of phase type?

    Daniel

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  20. Interesting analysis of our March WX.

    http://earthobservatory.nasa.gov/IOTD/view.php?id=77671&src=eoa-iotd

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  21. Very narrow frontogenic rain band sharpening - from just south of Portage, to northwestern parts of Winnipeg. Radar estimated rainfall rates are in the 15-20 mm/h range under the core of that band, with intensities dropping off quickly to 4-7 mm/h on the periphery.

    Precipitation totals and location will depend on the evolution of that band, which may remain just north of the TransCanada. Cold pool at 925 hPa has weakened, and RUC keeps shallow, near-surface melting layer thru midnight. Still think there is shot at wet snow right under the heaviest forcing, if that band can linger long enough and allow colder air to move in (along with diurnal cooling).

    That leads to the next question.. RUC shows a southern wave strengthening over the course of the night, perhaps at the expense of our northern one. It will be associated with an increasing LLJ, modest instability, and a blossoming area of convection. Uncertainty as to whether or not it will rob energy and moisture from northern system. Some of that elevated convection may advect into SE Manitoba..

    Daniel

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  22. Rain falling a little harder now with 4 mm past hour at my station, and 7 mm since it started around 5 pm. Radar showing a band of moderate to heavy rain along and north of the Transcanada between from Portage thru Winnipeg to Pinawa, possibly along that zone of 700 mb forcing Daniel was alluding to. Still looks like all rain, but that could change over to wet snow after midnight although bulk of precip should be east of the city by then.

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  23. 15mm of rain when I last checked here in St. Bonifice. Coming down harder now; I had doubts to even getting more than 10 but the models seem to have trended to a more correct solution mighty quick today. If the rain can keep up for 2-3 more hours it wouldn't surprise me if I had an inch in my rain gauge.

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  24. 18.6 mm at my place.. quite a bit more than models were suggesting (especially the ECMWF) Hi-res models were the best with both NAM and RGEM suggesting 10-15 mm rain for YWG. Winnipeg was in the "sweet spot" of this system, lying at the inflection point of the comma head associated with the 700 mb low crossing southern MB along the US border.

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  25. I finished with 12.4 mm at my place in Transcona, in line with EC's 10-15 mm forecast.

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  26. A couple reports of some minor snow amounts from yesterday's system.. including 1 cm in Roblin and Gilbert Plains, 0.4 cm in Yorkton, and trace amounts in Pinawa. Most places in southern MB only saw about 5-10 mm of rain with this system, with the heaviest amounts in a narrow band from just south of Portage to Winnipeg. Shows up nicely on Woodlands 24 hr radar accumulation product from Brad's radar viewer (click on my name for image) Note however that radar precip amounts seem to be overestimated by 2-3X actual reports.

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  27. I finished with 20 mm at my place in South St. Vital.

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  28. That band was associated with a region of mid-level frontogenesis (intensifying temperature gradient), associated with a small scale deformation axis. Thermal direct circulations across temperature gradients (rising in the warm air and descending in the cold air), have been linked with enhanced rates of precipitation. Convection blowing up on the LLJ and area of better elevated instability, seemed to weaken the northern band.

    The 16 mm at YWG seems too low, as it was closer to the heavier band.. measurements from that site should not be trusted with much confidence. Would be interesting to look at precipitation totals from ag-wx and cwb stations under that QPE bullseye..

    Daniel

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  29. 20mm here in fort garry

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  30. The weatherbugs for Rosser and Grosse Isle show monthly totals of 20-25 mm for April, not sure if includes yesterdays rain or not.. the map plots with daily data seem to be down.

    Re precip band

    Yeah that mid level forcing and deformation was maximized on the north side of the low as Rob mentioned (I missed your comment earlier).

    Daniel

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  31. Rob!

    Looks like next week a storm system may drag some very warm air into the area. Depending on how close the low pressure system gets to us, southerly winds prior to the system could pump up some warm and humid air.

    BTW, I'm moving in JUNE! Off to ST VITAL part of the world :) Bought by first HOUSE!!

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  32. Congrats on the house, Daniel!

    GFS is showing quite the warm-up early next week. Also a cold front slicing through late on Tuesday with a good amount of MLCAPE ahead of it.

    Could be some thunderstorm potential to monitor for next week Tuesday.

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  33. Congrats on the new house daniel! Looking forward to some new St Vital weather obs this summer!

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  34. Thanks Rob and Derek!

    With more rain in the forecast, and with all the previous rains, things will really green up with some warm weather!!

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  35. nice idea.. thanks for sharing.

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  36. nice idea.. thanks for sharing.

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