Friday, December 25, 2015

Deepest Christmas snowcover in Winnipeg in 15 years

41 cm of snow over the past week has resulted in the deepest snow cover at Christmas in Winnipeg in 15 years.  As of this morning, the airport was showing a snowdepth of 21 cm, the deepest snowpack at Christmas since a 30 cm reading on Dec 25 2000. At my site in Charleswood, I recorded a snow depth of 30 cm this morning.. the deepest snowdepth on Christmas since Dec 25 2000 (31 cm).        
Christmas day snow on ground stats (Winnipeg since 1955)

Least snow on ground....... TR (1997) *
Most snow on ground......... 80 cm (1955)
Average snow on ground.... 16 cm 

* NOTE: Official "snow on ground" readings for Winnipeg airport started in the fall of 1955 and continued until 2002. Thereafter, snow on ground measurements at the airport have been taken by an automated sonic snow sensor at the XWG autostation which uses sound waves to estimate snow depth.  This automated method is not as reliable as human read measurements due to sampling errors caused by drifting, which human based measurements can take into account. Since 2004, manual snow depth readings have been taken at the Charleswood 2 climate site (my backyard) as a secondary source of snow depth measurements in Winnipeg. Note however that snow depth readings at this residential site are generally higher than readings at the airport (by about 30%), owing to the fact that the airport site is more exposed and more prone to blowing, drifting and compacting of the snow pack. 

Prior to 1955, there have been at least 3 Christmases noted with no snow on the ground in Winnipeg: 1939, 1913, and 1877 (based on anecdotal and newspaper reports) Coincidentally, the 4 years with green Christmases in Winnipeg were also the top 4 warmest Decembers on record.

Christmas day snowdepth in Winnipeg since 2000

(Rob's Obs readings)  ........ Airport

2015 ......... 30 cm .............. 21 cm
2014 .........  5 cm   .............   1 cm
2013 ......... 21 cm .............. 10 cm
2012 ......... 24 cm .............. 18 cm
2011 .........   2 cm  ..............  1 cm
2010 ......... 23 cm ................ M
2009 ......... 10 cm ................ 4 cm
2008 ......... 24 cm ............... 14 cm
2007 ......... 28 cm ............... 15 cm
2006 ......... 11 cm ...............  7 cm
2005 ......... 14 cm ................ M
2004 ........... 8 cm ................ 4 cm
2003 ........... 4 cm ................ M
2002 .......... 11 cm ............... 12 cm
2001 .......... 12 cm ............... 12 cm
2000 .......... 31 cm ............... 30 cm

Prior to 1955, there have been 3 Christmases documented in Winnipeg with no snow on the ground, although these are not part of the official climate record. They were 1939, 1913 and 1877. Coincidentally these are There was also reference made that in Dec 1834, the first snow of the season in Winnipeg fell on Dec 28th.. so it's possible that Dec 1834 was also a brown Christmas (but then, we don't know what they considered the first significant snow back in 1834)

Scenes from Christmas Day 1939 in Winnipeg

The following photos are from Christmas Day in 1939 in and around Winnipeg. The photos show Winnipeggers taking advantage of a rare snowfree Christmas day that year with activities like lawn bowling at Assiniboine Bowling Club (bottom left) and golf at the St Charles golf course (bottom right). Dec 1939 was the 3rd mildest December on record in Winnipeg, and included the warmest December temperature ever recorded in the city with a high of 11.7C on Dec 6th.

Winnipeggers pose on a rare snowfree golf course on
Christmas Day 1939 

Lawn Bowling in Winnipeg Christmas Day 1939
Golfing on Christmas Day 1939

Monday, December 21, 2015

Another round of snow moving into southern Manitoba Tuesday afternoon/evening.. 5-15 cm likely

Grey area highlights regions most likely
to see 5-15 cm snow Tuesday aftn/night
After a tame start to winter with little in the way of snow, Mother Nature is making up for it this week as yet another storm system brings another round of snow to southern Manitoba Tuesday. This will be the third significant snowfall of the past week in Winnipeg, after last Wednesday's 20 cm dump and Saturday's 5 cm snowburst. For tomorrow, a storm system pushing in from Washington state will track east into North Dakota, spreading snow along the US border by the lunch hour. As the system tracks east, snow will spread into the Red River valley and southeast Manitoba through the afternoon, reaching Winnipeg by mid to late afternoon just in time for the late afternoon rush hour. Snow will increase in intensity through the evening, with a period of heavy snow possible giving snowfall rates of 2-3 cm/hr at times. This will have serious impacts on the afternoon/evening rush hour if the band of heavy snow moves in by 4 pm. Total snowfall from this system is expected to be in the 7-10 cm range for most of the Red River valley including Winnipeg, but amounts of 10-15 cm are possible where the heavier snow band lingers a bit longer. Snow will taper off overnight Tuesday and should be done by the Wednesday morning commute. Luckily winds will not be that strong with this system and temperatures will be mild around -5C which should help with snow clearing operations Tuesday night.  Even so, expect a slower commute Wednesday morning as the city digs out from yet another snowfall.  

Tuesday, December 15, 2015

Snowfall warning issued for WInnipeg/RRV.. 10-20 cm of snow possible Wednesday

A snowfall warning has been issued for Winnipeg and the Red River Valley for Wednesday as a storm system from Colorado moves into Minnesota. Snow from this system will spread into southern Manitoba after midnight and become heavier towards morning.  Snow is expected to move into Winnipeg around 3 am overnight, and become heavier by 6 am or so with 2-5 cm of new snow by the morning rush hour.  Plan to allow extra time to get to work or school tomorrow morning as the commute will be slow due to snow covered roads and slippery conditions. A period of moderate to heavy snow is expected through the morning with snowfall rates of 1-2 cm/hr at times giving another 5-10 cm by midday before snow eases off in the afternoon and evening with another 5 cm or so. This will make for a very slow commute for the drive home (unless everyone leaves earlier because of the storm) All in all, 12-20 cm is possible for Winnipeg by Wednesday night. Occasional light snow will continue Wednesday night into Thursday morning with another couple cm possible. Winds will also pick up later Wednesday into Wednesday night so drifting and some blowing snow will become an issue although bulk of snow will be over by then.

Models coming in line that heaviest swath of snow tomorrow will set up somewhere from the Pilot Mound-Altona area north through Winnipeg into southern Lake Winnipeg region. 10-20 cm possible within this swath. 10 cm outside this main area. Dry slot will give lesser amounts to our southeast and has pushed the heavier band further west.. which is why initial forecast of heavier amounts southeast of Winnipeg has changed. That's what the latest guidance is saying.. now let's see how it all pans out. Got my snow ruler ready!


A snowy commute home for Winnipeg drivers as a band of
heavy snow crosses the city in time for "rush" hour
(photo credit: Winnipeg Free Press)
Light snow started up in Winnipeg around 2 am and by 8 am, I measured 2.4 cm at my site in Charleswood. Snow started to pick up in intensity through the morning with another 4 cm by noon. Snow continued steady but fairly light through the afternoon, before a heavier snowband pushed through the city from 3-5 pm dumping 5 cm of snow in 2 hours at my site. I recorded a storm total of 14 cm by 5 pm, and 15.5 cm by 6:30 pm. Winds were generally light through much of the event, although they started to pick up late in the afternoon into the evening out of the northwest causing some blowing and drifting snow. General snowfall amounts of 10-15 cm were common through the Red River valley and SE Manitoba up to the evening. Snow continued Wednesday night with another 5 cm by Thursday morning. Storm total at my site was 20.5 cm.  

Sunday, December 13, 2015

Storm system to bring snow to Red River valley and SE Manitoba Wednesday.. colder temperatures to follow

Probability of at least 5 cm of snow
within 24 hrs by Wednesday evening
(WPC graphic)
Mild weather continues over southern Manitoba with extensive cloud, patchy fog and occasional freezing drizzle. This stagnant weather pattern is expected to persist for the next couple of days before a more significant storm tracking through Minnesota Wednesday impacts southern Manitoba with snow and increasing winds. There remains some uncertainty with the track of this storm, which will influence snowfall amounts over southern Manitoba. At this point, models are indicating the heaviest snow with this system will fall mainly in eastern North Dakota and northern Minnesota, with lesser amounts over southern Manitoba. Even so, southeast Manitoba and the Red River valley should see some snow with this system, with 5-10 cm possible for most areas. Should the system track a bit further west, snowfall amounts will likely be higher across southern Manitoba. Note also that the system will be bringing increasing north winds Wednesday, which would lead to blowing and drifting snow issues especially over the Red River valley.  Stay tuned for future updates on this developing system.

Average temperatures in Winnipeg over
past 90 days shows persistent warmth
A change to colder weather will follow in the wake of this system for the end of the week into the weekend, with temperatures falling to more seasonable levels for mid December. Keep in mind, normal highs are now -10C in southern Manitoba with lows of -20C.. temperatures we have yet to see so far this season.  The coldest temperature since Nov 1st in Winnipeg has been only -17.5C on Nov 26th,  and we've only dropped below the -15C mark on only 2 occasions so far this season. Truly remarkable given that normal lows are now -20C. Temperatures have been so consistently above normal over southern Manitoba over the past 2 months that dropping to near normal temperatures would seem like a bitter cold snap. Thanks to the strongest El Nino since 1997, Arctic air intrusions have been blocked from surging southward, allowing a persistent flow of mild Pacific air to prevail over the Prairies and much of north America.  In the past 8 weeks, Winnipeg has seen only 5 days below normal, with none since Nov 27th. So a change to even normal temperatures will seem cold. However, indications are the cold weather will not be that intense or prolonged, with above normal temperatures expected to return by next week. This is consistent with a strong El Nino winter, where cold air intrusions are less frequent and shorter in duration.        


Sunday, December 06, 2015

December warm spell continues - but trend to colder weather and snow by end of week

It was another balmy day across southern Manitoba Sunday, with temperatures once again well above normal for December.  Snowfree areas and localities in downslope regions were the warmest again as temperatures soared into the double digits yet again, including 11C in Winkler, 10C in Morden and 11C in Wawanesa. In these areas, daytime highs have been above freezing for a full week now, including 2 or 3 days in the double digits.  

Winnipeg didn't fare quite as warm Sunday with southerly winds off a lingering but diminishing snowpack over the northern and eastern Red River valley keeping temperatures in the low single digits (high of +3C) Nonetheless, considering normal highs are now -7C and lows near -18C, few people will complain about temperatures some 10-15C above normal (except cold weather and snow lovers)   But if you're looking forward to colder weather or snow, there's some good news in the forecast. Models are indicating an end to the current December warm spell later this week, with a return to more seasonal temperatures by the weekend. Before that, a weak system tracking across southern MB Tuesday may bring some mixed precipitation (including a threat of freezing rain) Tuesday.  A stronger system will impact southern MB by Thursday with some snow possible which will herald the arrival of colder air later Thursday and Friday into the weekend. There is a possibility of more snow on the weekend, but models are less certain about the timing and amounts.. so that will need to be monitored. In any case, enjoy the balmy weather while you can.. colder weather and snow is on the way for the end of the week.

Dec 4 2015 - Morden soars to record 14.2C. Warmest December day since 1969

Morden resident cuts his lawn on Dec 4 2015
as temperatures soar to 14.2C (from CBC)
One of the more remarkable milestones of this current December warm spell was registered in Morden, MB on Friday Dec 4th when the mercury soared to an astonishing 14.2C, making it not only the warmest spot in Manitoba that day, but in all of Canada.  Having a place in Manitoba get national hot spot honours in December is exceedingly rare, as the balmy west coast, Maritimes or southern Ontario are typically the warmest areas of Canada in winter. The 14.2C reading was a record high for Morden for Dec 4th, beating the previous record high of 12.2C in 1916. It was also Morden's 3rd warmest temperature ever recorded in December, surpassed only by a 14.4C reading on Dec 1 1969, and their all time December high of 17.8C on Dec 6 1939 (yes, 17.8C!).  The 1939 record was established during a historic warm spell that brought the warmest temperatures ever recorded in southern Manitoba in December, including Winnipeg's all time December high of 11.7C on Dec 6th (the only time Winnipeg has observed a temperature of 10C or more in December). That year went on to see a green Christmas across much of southern Manitoba, including Winnipeg.

Max temperatures across southern MB - Dec 4 2015
Warmest readings in snowfree and downslope areas
So how did Morden get so warm on Friday?  Two main reasons: no snow on the ground and warming downslope winds off the Pembina escarpment.  A look at the max temperature map on Dec 4th shows the warmest readings that day were observed over southwest Manitoba (where there was no snow cover), especially in areas with warming south-southwest downslope winds off higher terrain.This included areas east of Riding Mountain (Dauphin, McCreary), north of the Turtle Mountains (Boissevain, Deloraine) and east of the Pembina escarpment (Morden, Miami) Downslope winds off higher terrain can add 2-7C (and sometimes more) to downwind localities compared to areas outside the downslope zone.


Relief map of Pembina valley (left) shows Pembina escarpment running just west of Morden, dividing higher terrain to the west and the lower flat plains of the Red River valley to the east. South to southwest downslope winds blowing off the higher terrain can result in warmer temperatures immediately to the east of the escarpment (like a mini-chinook)  Image on the right is a visible satellite image taken Dec 4th at 2:45 pm showing snowcover over southern MB. There was a distinct line from Portage La Prairie through Carman to Emerson, separating snow-covered areas to the east and bare ground to the south and west. Temperatures were some 5-10C cooler over the snow-covered areas, with highs of +2-4C, including a windy +2.3C in Winnipeg (surface plots on image are in degrees F. Morden is shown as 57F (14C) at this time)  The high resolution image below shows the snowcover in greater detail. Note the distinct snow line running through Carman to northeast of Emerson. Note also deeper snowpack (brighter white area) still evident west and northwest of Winnipeg.

High resolution MODIS satellite image showing snowcover
over Red River valley on Dec 4 2015

Synoptic set up - Dec 4 2015

Sfc map - 6 am Dec 4 2015
925 mb - 6 am Dec 4 2015
On the morning of Dec 4th, southern Manitoba was is a southerly flow of very mild air between a surface ridge south of Lake Michigan, and a trough over western Saskatchewan.

Of note is how warm the air was just above the surface that day. Air temperatures up to +14C were observed over the Morden area at 925 mb, or about 700 metres above ground.  This is exceptionally warm air for December, and was helped northward by a strong south-southwest wind of 50+ knots (90+ km/h) at this 925 mb level. These warm values would eventually cool off to +8C by mid afternoon, but it showed the potential for temperatures over 10C in snowfree areas that day. Morden got the greatest benefit of this warm air aloft, helped by sunshine, snowfree ground, and downslope winds. It should be noted that on this day, the downslope winds did not reach much further east of Morden, and in fact, nearby Winkler, just east of Morden, only got up to 9.5C that day as their winds were more southeast through the day tapping cooler air off the snowcovered Red River valley.

 A look at Morden's hourly temperature chart for Dec 4th shows that temperatures rose from +5C at 9 am to +10C by 11am, and 12.7C by noon. It would climb to a maximum of 14.2C shortly after 2 pm, before downslope winds from a 200 degree direction shifted to the southeast (160 degrees) tapping cooler air over the snow-cooled Red River valley. Temperatures dropped quickly to 8C by 3 pm and +5C by 4 pm.

Road trip to Morden  

Snowcover becomes meager
east of Carman
It's not very often that a place in Manitoba experiences 14C in December, so I decided to take a drive to Morden that day to witness such a rare event. Considering it was just an hour away from Winnipeg made it that much more amazing to experience. I left Winnipeg shortly before 1 pm heading off on Highway 3 through Sanford to Carman. There was a brisk southerly wind gusting to 60 km/h, keeping temperatures in the +2 to +3C range almost all the way to Carman. As I got closer to Carman, the meager snowpack started to diminish and the temperature rose to +6C in Carman.

Snowcover disappears south
of Carman
Green fields north of Morden
Dec 4 2015

As I turned south on Hwy 3 heading to Morden, the snowpack disappeared completely just south of Carman and from there on, there wasn't a hint of snow anywhere, with the landscape resembling something from October or April.  The temperature rose to 10C by the Hwy 23 intersection and 11C by the turnoff to Morden.

Hwy 3 to Morden - Dec 4 2015
Once I headed west to Morden, the outdoor temperature on my car thermometer climbed 1C per kilometre as I headed into the downslope region, reaching 14C by the time I got into Morden. My car thermometer would peak at 15C at 2:15 pm. Getting out in Morden, it felt like April.. no snow on the ground, a balmy breeze under clear blue skies, and temperatures in the teens. It was quite the difference from chilly snowcovered Winnipeg just an hour away! By 3 pm, the temperature had dipped to 11C as winds shifted into the southeast and by 3:30, it was down to 7C as I headed back to Winnipeg. It was a quick visit, but certainly a novelty to experience springlike warmth just an hour outside of Winnipeg!  If you're looking for a balmy getaway near Winnipeg, keep an eye on those downslope winds!

Downtown Morden - Dec 4 2015

Car thermometer registers
15C in Morden - Dec 4 2015

Dec 4 2015 in Morden - or is it April?

Wednesday, December 02, 2015

Mild November caps off 4th warmest fall on record at Winnipeg

Mild weather continued through much of November across southern MB, with mean monthly temperatures almost 4C above normal for November. In Winnipeg, November finished with an average monthly temperature of -1.0C or 3.9C above normal. This ties Nov 1928 as Winnipeg's 20 mildest November since 1872. Temperatures were especially mild over the first 3 weeks of the month before the first snowfall of the season on the 18-19th. Up until then, temperatures were above normal every day ending a streak of 25 straight days above normal since Oct 26th.     

Temperature anomaly map (left) for November 2015 shows core of abnormal warmth centered over northern Minnesota and southern MB in November. Only 4 days of the month were below normal in Winnipeg (right)  

The mild November helped cap off the 4th mildest fall in Winnipeg since 1872, tying the falls of 2009 and 1953 at 7.3C, or 3C above normal.

90 day graph of temperatures (right) in Winnipeg over the Sep-Nov period 2015. All 3 months were above normal, with only 19 days below normal over the 3 month period. 

Outlook for December: 

6-10 day CPC outlook
3-4 week outlook to Dec 25th

Milder than normal weather is expected to continue through at least the first half of December, thanks to a very strong El Nino this year. The next week looks especially mild, with an extended flow of Pacific air that will keep temperatures about 10-15C above normal into next week. Temperatures will be at or above the freezing mark over much of southern Manitoba over the next few days, especially in snowfree areas such as the Pembina valley (Morden, Winkler), SW Manitoba (Melita), downslope areas east of the Riding Mtns  (Dauphin, McCreary) and forested areas (Whiteshell)  In these areas temperatures may reach +5 to +10 C by the weekend.  Long range models are hinting at colder weather (near normal) arriving the weekend of Dec 12-13th, but it's too early to say if that's a trend to colder weather for the second half of December, or a passing cold snap. Past El Nino years suggest that cold snaps are usually short lived and not as intense as the upper pattern rebounds to bring a return of milder Pacific air over the country.  In fact, when looking at past strong El Nino years, there's a very high probability that December will end up warmer than normal in southern MB (as well as much of the northern and eastern US). The image below is a composite of average December temperature anomalies of 6 strong El Nino years since 1950 (1997, 1991, 1982, 1972, 1965, 1957)  Of these years, only one December was colder than normal in the Prairies (1972)  The top 2 warmest Decembers on record in Winnipeg occurred during strong El Nino events (1877 and 1997)  

Composite image of December temperature anomalies
based on 6 strong El Ninos since 1950