Category: Forecasts

Our First Spring Storm System

Brad Leave a comment

After a period of unprecedented March warmth, it is time for a dose of March weather reality. Our first significant spring weather system will roll through Southern Manitoba early this week. This system will follow what has been a cool, but fairly seasonal weekend. Hopefully you are starting to get a feel for what spring is really like in Southern Manitoba.

Precipitation forecast for Southern Manitoba early on Tuesday morning

The GEM model shows light rainfall over Southern Manitoba at 1am on Tuesday with more precipitation developing over the Dakotas

A strong south-easterly wind will develop out ahead of the approaching low pressure system on Monday. Wind speeds will generally be on the order of 40km/h gusting to 60km/h. The combination of strong wind speeds and mainly cloudy skies will mean that high temperatures in Southern Manitoba will stay stuck in the mid single digits on Monday. During the day on Monday light shower activity, as well as the odd embedded thunderstorm, will develop across Southern Manitoba. Accumulations from these showers are expected to be light, with rainfall amounts of only a couple millimeters expected.

This weather system will really begin to get going on Monday night, with strong to severe thunderstorms expected to develop across the Dakotas. These thunderstorms will be triggered by a strong area of lift associated with the low pressure system. Additionally, a powerful low-level jet stream will provide a secondary source of lifting and a strong moisture feed. A low-level jet stream, or LLJ for short, is a “river” of very strong wind about 5000 feet above the ground. Wind speeds in the LLJ can exceed 100km/h less than one mile above the surface. The result of the LLJ on Monday night will be the rapid movement of air into the Northern US Plains and Southern Manitoba from more southern parts of the United States. The movement of warmer, more moist air into our region along the LLJ will provide support for some stronger storms on Monday night. The potential for severe thunderstorms certainly exists on Monday night in portions of North and South Dakota. It is unlikely that we’ll see any severe storms in Manitoba, but some stronger cells with gusty winds and hail may sneak across the border late on Monday or early on Tuesday.

The thunderstorms that develop across the Dakotas on Monday night will eventually move into Southern Manitoba during the overnight hours regardless of their strength. Besides the potential for gusty winds and hail as outlined above, many of the storms moving up from the south will produce locally heavy rainfall. Widespread accumulations of 5 to 10mm are expected on Monday night into Tuesday morning over Southern Manitoba, but locally heavier amounts are possible where thunderstorms pass by.

The bulk of the precipitation will be over for Winnipeg and the Red River Valley by Tuesday morning. Only light showers will persist during the day on Tuesday. However, residents of Western Manitoba won’t be quite as lucky. Rain will change to snow in Western Manitoba on Tuesday morning. Snow will continue over portions of Western Manitoba through the day on Tuesday. Total accumulations by Tuesday evening will generally be in the 2 to 6cm range in Western Manitoba. However, areas at higher elevations, such as Riding Mountain National Park, may see 10cm or more by late in the day on Tuesday. It is possible that Winnipeg and the Red River Valley could get a bit of snow on Tuesday evening. If any snow does fall it will be light in nature and won’t accumulate to much, if anything. Even if Winnipeg does get a dusting of light snow on Tuesday night it will be gone by Wednesday, as high temperatures will remain well above zero through mid-week.

Storm total rainfall amounts in Southern Manitoba will vary from place to place. Some estimates are listed below:

  • Winnipeg: 10 to 15mm
  • Steinbach: 5 to 10mm
  • Brandon: 10 to 20mm
  • Portage la Prairie: 10 to 15mm

*Note that the above forecasts have a large margin of error given that thunderstorms will largely determine where the heaviest rain will fall.

The GFS is predicting temperatures near 20C for Winnipeg next Saturday

The GFS model temperature prediction for next Saturday – the yellow/orange boundary represents temperatures near 20C (image courtesy of College of Dupage)

Long-range models don’t show any sign of winter returning to Southern Manitoba. The current run of the GFS model (a short to medium range model) shows temperatures potentially returning to the 20C mark in Southern Manitoba by next weekend. While this may or may not actually happen, it is a sure sign that temperatures will remain above-normal through the end of the month.

Elsewhere in Weather News

Hail Storm – A Winter Wonderland

This past Friday, a severe thunderstorm rolled through Indiana bringing with it strong winds, heavy rain and frequent lightning. What was so unusual about this storm was that it also dumped four inches of hail during the course of 15 minutes – which is considered quite a lengthy time for a hail storm. The severity of the hail storm was more than enough to wreak havoc on the highways. Hail drifts were reported to be a foot high in some areas and authorities closed a section of the interstate in the area due to cars getting stuck in ruts and several accidents being reported. The road conditions were winter-like as cars hit the ditch and residents described the scenery as a “hail blizzard”. After four hours, snow plows cleared away the remainder of the hail that was not melted yet and the interstate was reopened. The hail was not significant in size as it came down, only measuring up to dime-size, causing no property damage in the area.

Hail drift in the doorway, taken in Fountaintown, IN (just east of Indianapolis). (Source: WTHR news - Jessica White)

Hail drift in the doorway, taken in Fountaintown, IN (just east of Indianapolis). (Source: WTHR news – Jessica White)

The line of storms that was associated with a cold front moving through the region also prompted tornado watches in the Midwest, as several weak tornadoes touched down in Illinois, Indiana and Kentucky. Since then, the slow moving cut-off low brought more potent storms to the Southeast US on Saturday. It has now moved out over the Atlantic and is no longer a threat to North America.

Interstate 74 totally covered by hail, with ruts. Snowplows had to come in and clear away the hail. (Source: WTHR news)

Interstate 74 totally covered by hail, with ruts. Snowplows had to come in and clear away the hail. (Source: WTHR news)

Elsewhere in Weather News has been provided by Matt

A Return to More Seasonal Weather

Brad Leave a comment

The unbelievable March heat wave is coming to an end in Southern Manitoba as the blocking pattern that has been maintaining record-obliterating heat throughout much of Central and Eastern North America begins to break down. This will cause us to return to a slightly more unsettled and seasonal pattern, albeit temperatures will still remain (for the most part) above normal for this time of year.

Heat Wave Shatters Records

Temperature Anomalies March 8-15

The intensity and scope of Summer in March is clearly visible in this data from the MODIS instrument on the Terra satellite. Areas with warmer than average temperatures are shown in red; near-normal temperatures are white; and areas that were cooler than the 2000-2011 base period are blue. Image credit: NASA Earth Observatory.

The March 2012 heat wave has shattered records all across North America, with thousands of temperature records being broken across the United States and Canada. Pellston, Michigan broke their daytime high record for March 21 by an absurd 32°F, a temperature that was 48°F above average. In St. John, NB, their daytime high of 25.4°C on March 21st was warmer than any day they’ve ever had in April. Halifax, NS
also had a warmer day yesterday than any day on record in April with their high of 28°C. The list goes on and on, but it seems that almost anywhere you go east of the Rocky Mountains has set numerous records and is experiencing weather that’s arrived at least a month early, if not a couple! The image above illustrates exactly how substantial the warm weather has been; it shows the departure from the 2000-2011 normal for land temperatures for March 8-15th. The reds show just how wide-spread and substantial the heat wave has been!

Winnipeg has broken numerous records over the past 12 days, including:

  • 8 daily record high temperatures (11, 12, 15, 16, 17, 18, 19, 22)
  • Earliest 20°C reading on record (March 18)
  • Warmest overnight low in March (14°C on the night of March 18/19)
  • Earliest thunderstorm on record since 1953 (Evening of March 19th)
  • Warmest March day on record (March 19th, 23.7°C)
  • Most significant departure from normal temperature for any day of the year (+23.4°C above normal on March 19th)
  • 4 consecutive days over 19°C (Only 4 days since records began have reached that mark. From Rob’s Blog: In other words, it took only 4 days during this warm spell to match what took 140 years to accomplish.)

Records that will need to happen yet and need to be verified:

  • Warmest March on Record (Currently sitting at a mean temperature of 0.4°C, record is 1.6°C set in 1878).
  • Highest dew point in March (17°C on March 19th, need to finish parsing data set to verify)

The past week and a half has truly been an extraordinary weather event that has not been seen in the lives of 99% of the people who will read this. As the next weather system moves through, we’ll see a transition it a more seasonal weather pattern that will return us to closer-to-normal temperatures and bring with it some unsettled weather.

Upcoming Weather

Accumulated Precipitation

Accumulated Precipitation from 18Z Mar. 22 to 00Z Mar. 24 (Thursday Afternoon to Friday Evening)

A somewhat complicated scenario presents itself for Winnipeg over the next couple days. Overnight, the cut off low that has been anchored over the Southern Plains of the US has been working NE and has pushed it’s deformation zone into Southern Manitoba, spilling clouds northwards. There’s a chance we’ll see a light shower early this morning in Winnipeg, however most models keep the precipitation to our south (including the GEM-REG, pictured above. There will be a few scattered showers through the RRV through the morning, with a better chance of measurable precipitation east of the Red River. The precipitation will move out by the afternoon, however we won’t lose the cloud. This will limit our temperature to 19 or 20°C. If we’re able to get a couple hours of sunshine today (unlikely), we’ll definitely have a shot at breaking the daily record high of 22.8°C.

As the low pulls off to the east, instead of clearing out with a northwest wind, we’re left in a slack flow as another system ejects northeastwards out of Montana. It will approach Manitoba on Friday night and cross the province through the Interlake on Saturday. As it moves across Saskatchewan on Friday night, it will pull much of the moisture in Southern Manitoba northwards as a warm front lifts out of North Dakota. Saturday morning will be a toss up…some models want to clear out the cloud and give us a nice sunny day, however I think that our proximity to the lift associated with the low, the cap we’ll have as we’re in the warm sector of the system, and the moisture present in the low-levels will keep us on the cloudier side of things until the cold front passes through around lunch time. We’ll clear out with the cold front and have our coldest night in what seems like forever now with an overnight low around -5°C.

Sunday will be a fairly nice, albeit crisp, day with sunny skies and a daytime high in the high single digits. While this temperature will certainly feel cold, it will still be 5°C+ above the normal daytime high.

The most significant precipitation event since the beginning of March looks to be shaping up for Monday night through Tuesday; it’s still early, though, so we’ll keep you updated in the comments on this post and have a good look at it in Monday’s post.

And last but not least, happy World Meteorological Day everybody!

Table of Broken Temperature Records (Winnipeg)

Day New
Record		 Old
Record		 Previous
Record Year
Sun Mar. 11 12.8°C 12.5°C 1981
Mon Mar. 12 9.7°C 7.2°C 1922
Thurs Mar. 15 14.4°C 11.1°C 1927
Fri Mar. 16 19.9°C 12.4°C 1981
Sat Mar. 17 19.2°C 12.8°C 1938
Sun Mar. 18 20.9°C 14.4°C 1910
Mon Mar. 19 23.7°C 18.9°C 1938
Thurs. Mar 22 21.7°C 18.3°C 1878
Table of daily record high temperatures during the March 2012 heat wave from March 11, 2012 to March 22, 2011.

March Heat Wave Continues

Brad Leave a comment

Last week saw Winnipeg bathing in historically abnormal warm weather that shattered numerous daily record high temperatures as well as breaking the record for the warmest day in March since 1872. Thunderstorms then pushed through Winnipeg Monday night, lighting the city up with intense lightning and settling the dust with 10-15mm of rain. On the back side of these storms, cooler air pushed over Southern Manitoba, giving us a daytime high yesterday around 13°C cooler than Monday, which amazingly was still ~10°C above normal for this time of year. Despite the “cool” day, the heat wave isn’t over yet, with temperatures set to rebound to threaten more daily high temperature records over the next few days.

Temperature Records Smashed

Day New
Record		 Old
Record		 Previous
Record Year
Sun Mar. 11 12.8°C 12.5°C 1981
Mon Mar. 12 9.7°C 7.2°C 1922
Thurs Mar. 15 14.4°C 11.1°C 1927
Fri Mar. 16 19.9°C 12.4°C 1981
Sat Mar. 17 19.2°C 12.8°C 1938
Sun Mar. 18 20.9°C 14.4°C 1910
Mon Mar. 19 23.7°C 18.9°C 1938
Table of daily record high temperatures over the from March 11, 2012 to March 19, 2011.

Winnipeg saw unprecedented heat for the middle of March which broke daily high temperature records on 7 of 9 days. Many records were broken by at least 5°C, and temperatures peaked on Monday, March 19 at 23.7°C, which broke the record high temperature for that day by 4.8°C and broke the old record for the hottest day in March in Winnipeg of 23.3°C set on March 27, 1946. On Sunday, March 18th, Winnipeg had a high of 20.9°C, which was the earliest 20°C reading on record.

Since Friday, Winnipeg has recorded 4 straight days over 19C. In the previous 140 years of March records, that mark has been reached on only 4 occasions in Winnipeg. In other words, it took only 4 days during this warm spell to match what took 140 years to accomplish.
– Rob’s Obs Blog

Perhaps even more impressive was how far above normal temperatures have been. Typically, for the second week of March, normal daytime highs are around -1°C to 0°C. With temperatures rocketing into the high teens, Winnipeg spent almost an entire week with temperatures at least 15°C above normal.

Temperature Anomolies

Winnipeg Record Daily Mean Temperature Anomalies, courtesy Danny Blair – University of Winnipeg

In fact, as the above graph shows, Winnipeg set a new all-time record for temperature anomaly. On March 19th, the daily mean temperature was 23.4°C above normal, which was a higher value than any other day of the year. Winnipeg had never been so far above normal temperatures as Monday.

The Weather This Week

So what’s in store? After a cool Tuesday, temperatures are set to rebound today and tonight, with milder air once again pushing into our region. Today will bring plenty of sunshine with a breezy southwest wind around 30km/h and a high of 14°C. A warm front will push northwards through Southern Manitoba on Thursday, bringing a mix of sun and clouds and temperatures in the upper teens. This warmth will once again bring us the chance of breaking more daily record high temperatures. Currently, Thursday currently looks to be the most likely day we may break a record high temperature. For the next few days, the daily record high temperatures are:

Day New
Record		 Old
Record		 Previous
Record Year
Wed Mar. 21 ??.?°C 19.4°C 1938
Thur Mar. 22 ??.?°C 18.3°C 1878
Fri Mar. 23 ??.?°C 22.8°C 1910

How about the long term? Ensemble guidance continues to smother central and eastern North America with 90-100% chances of temperatures being above normal.

Anomaly Outlook

NAEFS 8-14 Day Temperature Anomaly Probability Outlook, valid March 28 – April 4.

With probabilities that high, while we may have a chilly day here or there, we’ll be hopping right towards summer with little risk of a disheartening return to winter.

March Madness

Brad Leave a comment

What a week it has been! Temperature records have fallen, our snow cover has disappeared, and thunderstorms are in the forecast – the question is what next?

Map showing the risk of thunderstorms on Monday, March 19, 2012

The light green region shows where there is a slight risk for severe thunderstorms on Monday

This week will start out on a warm and possibly stormy note. Monday’s temperatures are expected to be in the low to mid twenties across Southern Manitoba with a risk of thunderstorms. If Winnipeg records a high temperature on Monday that is greater than +23.3C the city will record a new all-time record high for the month of March. The previous all-time record high of +23.3C was set on March 27, 1946. On Sunday Winnipeg set a new record for the earliest ever occurence of a 20C high temperature, beating the old record of +22.8C set on March 23, 1910.

Day New
Record		 Old
Record		 Previous
Record Year
Sun Mar. 11 12.8°C 12.5°C 1981
Mon Mar. 12 9.7°C 7.2°C 1922
Thurs Mar. 15 14.4°C 11.1°C 1927
Fri Mar. 16 19.9°C 12.4°C 1981
Sat Mar. 17 19.2°C 12.8°C 1938
Sun Mar. 18 20.9°C 14.4°C 1910
Mon Mar. 19 23.7°C 18.9°C 1938
Table of daily record high temperatures over the past week.

As you may have noticed on Sunday, the humidity has risen significantly in the Red River Valley and South-Eastern Manitoba. When that extra moisture in the air is combined with warm temperatures, thunderstorms become possible. A strong jet stream is currently in place over Southern Manitoba, setting the stage for some potentially strong storms later on Monday afternoon into the evening. There will be a “lid*” over the atmosphere on Monday preventing storms from developing earlier in the day. This “lid” may or may not come off the atmosphere later on Monday. Whether or not the “lid” comes off will determine if storms can develop. Any storms that form shouldn’t be particularly strong, with the strongest storms only being marginally severe at best. However, with the way this March has gone it is best to assume that anything can happen – including stronger than expected thunderstorms.

The rest of the week looks a bit more “normal”. Actually temperatures will remain well above-normal but will seem more reasonable for this time of year. It looks like most days this week should feature high temperatures in the low double digits. As a result more temperature records will be threatened over the coming days, but they won’t be broken by the huge margins seen on the weekend. It doesn’t look like any more 20C days are imminent, but we certainly could hit 20 degrees again before the month is over.

In the long range models show continued warm weather through the end of March. With our snow cover gone it will be very difficult for conditions in Southern Manitoba to reach below-normal values. We’ll have to wait until our seasonal averages rise by several degrees before below-normal weather is even possible again. Bear in mind that above-normal temperatures don’t necessarily give way to beautiful weather conditions all the time. Models do hint at less settled weather over the next 7-10 days, which means we could get our first significant rain storm of the season (fingers crossed that it doesn’t turn into a snowstorm!)

Here is Environment Canada’s statement regarding broken temperature records on Sunday:

March 18, 2012 High Temperature Records

New high temperature records set on March 18, 2012

*A “lid” being on the atmosphere is simple way of referring to atmospheric capping. Capping is when there is warm air above the ground which prevents air near the surface from rising. We know that warm air rises and cold air sinks, but warm air only rises if it is warmer than the air around it. Therefore if the air at the surface is relatively warmer than the air aloft it will rise and if the air aloft is relatively warmer than the air at the surface the surface air won’t rise. On Monday the air aloft will be relatively warmer than the air at the surface for most of the day. Storms will only develop if colder air moves in aloft allowing the surface air to rise up high into the atmosphere. This may or may not happen, causing the thunderstorm forecast to remain uncertain.

Elsewhere in Weather News

Record Breaking Heat Wave Across the United States

The heat wave that currently has Southern Manitoba feeling more like May than March has also taken hold of much of the United States this past week. The unusual warmth is caused by a large surge in the jet stream over most of the US Plains, Midwest and East Coast. The jet stream, which acts as a fence between the cold air masses and warm air masses, is part of the reason why the US is experiencing its first major heat wave of the year. As the jet stream surges in the Plains and East, a trough (dip) in the jet stream over the west coast is bringing unseasonably cold air to the region and much precipitation with it.

250mb wind speeds, showing the jet stream, Sunday March 18th. (Source: Brad’s Model Viewer/COD)

250mb wind speeds, showing the jet stream, Sunday March 18th. (Source: Brad’s Model Viewer/COD)

Since the beginning of March the US has seen more than 1700 new records reached, including some records that weren’t even close to the previous records. Here are some notable ones from this past week across the US:

  • International Falls, MN: Previous record = 13°C, New record = 25°C, Average = 1°C
  • Marquette, MI: Previous record = 16°C, New record = 24°C, Average = 3°C
  • Minneapolis, MN: Previous record = 17°C, New record = 23°C, Average = 4°C

    Map showing record highs Wednesday, March 14th. 307 record highs were broken and 97 tied. (Source: National Climactic Data Center)

Map showing record highs Wednesday, March 14th. 307 record highs were broken and 97 tied. (Source: National Climactic Data Center)

As the jet stream shifts east early this week the spell of record-breaking temperatures will end for the plains, giving way to strong thunderstorms as the cool air from the west collides with the moist gulf air present over tornado alley. However, the Midwest and East Coast will remain near record breaking temperatures for a couple more days before cooler air arrives (but still above normal) and ushers showers in with it.