Spring at the Gates

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After the blast of winter Winnipeg and the rest of Southern Manitoba recieved last week where some regions recieved upwards of 7” of snow, spring has begun its march towards Southern Manitoba. After a cooler day today, we’ll see temperatures climb into the low single digits for the rest of the week. Some weather models show suprising heat building into the province, so the big question is: just how warm is it going to get?

12hr. QPF w/Surface Analysis

GEM-REG model image valid 12Z Thursday morning. Shaded areas are 12hr. precipitation accumulation. Red lines represent warm fronts and dark blue lines represent the cold front.

Southern Manitoba will start today on the cold side of a baroclinic zone that carves across Central Saskatchewan into North Dakota. This will limit our temperatures into the low minus single digits with daytime highs through the Red River Valley reaching only -7 or -8°C with a light northwest wind.

Winds will veer to the southwest in the evening as a low pressure system track through the Central Prairies drags a warm front across Southern Manitoba. This front will have a few scattered flurries associated with it, but accumulations should be only from a skiff to a cm. After the front passes overnight, temperatures will be on the up and up for the forseeable future.

On Thursday, we should see temperatures climb to around -4°C through the RRV under sunny skies. Thursday night temperatures will drop to between -15 and -20°C on the last cold night for a while. On Friday, temperatures will climb above zero and stay there through the night as temperatures are sustained by a southerly wind supplied by a powerful low pressure system tracking along the 60th parallel. Warm temperatures combined with a south-east wind will likely result in fairly cloudy skies as moisture from the melting snow is trapped underneath all the warm air aloft.

In the long term, models continue to pump warm air over Southern Manitoba. Warm temperatures will be the name of the game as low after low tracks across the northern Prairies. Little precipitation is in the forecast over the next 10 days, and the real question is just how warm will it get? High temperatures will be highly dependent on snow cover and, thus, difficult to accurately forecast. We’ll have to see just exactly how quickly the snow cover is eroded to get a better handle on high temperatures next week.

When a substantial snowpack is in place, daytime temperatures can have extreme difficulty rising much above 0°C regardless of the temperatures even a couple hundred feet off the ground. In Winnipeg, temperatures will often top out at 2 or 3°C under light or southerly winds. Under a westerly or south-west wind, temperatures can reach as high as 6 or 7°C, even with a snowpack.

The GFS currently has all the snow melting over the RRV by the middle of next week, and subsequently is able to pump up daytime highs as high as 16°C. This seems somewhat unrealistic, given how the snowpack was substantially reinforced at the end of last week.

Warmer Weather is on its Way

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With spring set to officially begin in just a few weeks it appears that spring-like weather is not far off either. It is safe to say that winter’s worst cold is behind us.

GEM Model precipitation forecast for Tuesday morning

GEM-Regional model precipitation forecast for early Tuesday morning

For the most part this week is expected to be warm in Southern Manitoba, but with some snow. Two low pressure systems will move across Southern Manitoba early in the week. One low will pass through on Monday and another one on Tuesday. The first system will be very weak and will drop less than 2cm of snow in most of Southern Manitoba on Monday. The second system on Monday night into Tuesday will be stronger, but the majority of the snow is expected to pass through Western Manitoba and up into the Interlake, avoiding the more heavily populated parts of Manitoba. However, the Tuesday system may still generate amounts of 2-4cm in places like Winnipeg and Brandon if it tracks as currently expected. Parts of Southern Manitoba closer to the International border can expect to see 2cm of snow or less from Monday night through Tuesday. Despite the fact that Monday and Tuesday will be a bit snowy temperatures will remain quite mild. Highs on both days should be near the zero mark in most areas. As Tuesday’s weather system departs it will pull down a bit of colder air from the north. As such expect a northerly wind to develop later on Tuesday causing temperatures to drop off for Tuesday night and Wednesday.

The second half of the week also looks to be rather mild. As alluded to earlier, Wednesday will be the coolest day of the week as we deal with the minor push of cold air caused by the low pressure system on Tuesday. By Thursday and Friday temperatures are expected to rise back to or above zero degrees, hopefully melting some of the snow that accumulated earlier in the week.

Climate Prediction Center outlook for March 10-14. Red areas can expect above-normal temperatures

Climate Prediction Center outlook for March 10-14. Red areas can expect above-normal temperatures

In the medium-range weather models are showing above-normal weather conditions (temperatures) developing in Southern Manitoba. If you read last week’s Monday post you will have realized that the long-range forecast for March was a bit unclear. In more recent days many medium range models and forecasts have begun to reveal the potential for warm conditions through early to mid March. The Climate Prediction Center graphic above illustrates this trend. However, we still don’t have a good understanding of how March will end. Although if you believe in the old March sayings “In like a lamb, out like a lion” or “In like a lion, out like a lamb” this March should end very nicely considering the nasty snowstorm late last week.

A Deadly Week in the US: Damaging Tornadoes

Tornado Outbreak: February 28 – 29, 2012

Disastrous cold fronts associated with low pressure systems barreled through many parts the United States last week. Areas that were hit the hardest include the Midwest, the Appalachian region, the Southeast and Southern Plains causing widespread destruction and over 50 deaths. As the system emerged from the Rockies, the cold front brought the necessary trigger to lift the moist, warm air. Early on, the Southern Plains were impacted with cold-core tornadoes in Nebraska and stronger storms throughout eastern Kansas where multiple weak tornadoes were reported, as well as an EF-2 tornado that destroyed most of the town of Harveyville, Kansas. Thankfully everyone was accounted for and only injuries were reported with the Harveyville twister.

Harrisburg, Ill – A man inspects what is left of a house completely demolished by the EF-4 tornado. (Source: ABC 7)

Harrisburg, Ill – A man inspects what is left of a house completely demolished by the EF-4 tornado. (Source: ABC 7)

As the cold front continued to push east into the night of Tuesday, February 28th, it spawned more dangerous tornadoes throughout Missouri and in southern Illinois. The strongest tornado produced, rated EF-4, struck the town of Harrisburg, Illinois, killing nine people and destroying entire city blocks at one time. As the cold front pushed east, even more tornadoes spun up through Kentucky and Tennessee on the 29th, injuring more people in the towns of Clarkson and Hodgenville, Kentucky. The two day ordeal brought in about 300 wind damage reports and over 50 tornado reports, spanning over nine states.

Tornado Outbreak: March 2 – 3, 2012

The destruction did not end there however. Another low pressure system had moved over Michigan – it spanned from southern Ontario all the way down to eastern Texas. The best parameters for severe storms were situated in the Midwest, around the western foothills of the Appalachians and through the US Southeast. The Storm Prediction Center (SPC) had issued some of these areas as ‘high risk’ for Friday, March 2nd – the highest tier of risk for severe weather the SPC can issue.

US Southeast RADAR showing the system spanning from southern Ontario to Texas at 3:30pm, March 2nd, including many supercells along and ahead of the cold front. (Source: College of DuPage)

US Southeast RADAR showing the system spanning from southern Ontario to Texas at 3:30pm, March 2nd, including many supercells along and ahead of the cold front. (Source: College of DuPage)

Supercells were popping up all over RADARs as the afternoon wore on, and the ingredients were in place for long-tracked tornadoes. Many tornadoes ripped through towns on this day, including West Liberty, Kentucky (pop. 3000), where the town was levelled by an EF-3 – not one building left untouched.

Warnings issued by the SPC March 2nd through 3rd. (Source: SPC)

Warnings issued by the SPC March 2nd through 3rd. (Source: SPC)

Some of the hardest hit areas, Kentucky and Tennessee, were expecting freezing rain following the cold front.

Nashville RADAR, including 11 tornado warnings, showing many supercells on the afternoon of March 2nd. (Source: NOAA-NWS)

Nashville RADAR, including 11 tornado warnings, showing many supercells on the afternoon of March 2nd. (Source: NOAA-NWS)

Here are some storm statistics regarding the outbreak:

  • A storm near Wilmore, Kentucky, was moving at speeds up to 137km/h.
  • 39 people, across five states, died from tornadoes associated with this storm – over 300 injured in Kentucky alone.
  • Winds up to 280km/h accompanied the Henryville, Indiana, tornado (EF-4) and the tornado stayed on the ground for over 80km.
  • At one point, four million people were within 40km of a tornado.
  • Three states issued a state of emergency.

Elsewhere in Weather News has been provided by Matt

Snow Tapering Off Today

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Today’s post will be short as I’m occupied with some family-related business.

Moderate snow pushed into the Red River Valley yesterday evening, bringing reduced visibilities and slippery conditions. Snow will continue through much of the day before tapering off.

Accumulated Precipitation From 00Z Friday to 00Z Saturday

GEM-GLB Accumulated precipitation from 00Z Friday to 00Z Saturday

Snowfall accumulations will generally be close to 5cm, however there will be a swath near the Trans-Canada highway between Brandon and Winnipeg that will likely see total amounts in the 5-10cm range. Snow should taper off by evening, and we’ll see an overnight lows throughout the RRV around -15°C.

Over the weekend, we’ll see mostly sunny skies with daytime highs near between -10° and -5°C, with overnight lows between -20°C and -15°C. The next chance for precipitation will come Monday with a passage of a warm front that will push our temperature up into the plus mid-single digits.

Unsettled Weather into the Weekend

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After a few sunny days, snowier weather will return to Southern Manitoba as a slow-moving system tracks from Southern Saskatchewan into Southern Manitoba along the international border. For today, we’ll see skies cloud over this morning, but we’ll still have beautiful conditions, with highs through the entire RRV sitting within a degree or two of 0°C and winds dying off by early afternoon.

Tonight will mark a transformation to a snowier pattern, however, as a complicated series of shortwaves begin to march across the Prairies associated with a strong upper low.

500mb Winds

500mb Winds from the GEM-REG valid 12Z Thursday morning, March 1st.

As the Colorado low that has brought severe winter weather to the Northern Plains progresses eastwards, an upper low will be pushing into Southern Alberta and inducing troughing eastwards across the Southern Prairies. As this troughing occurs, a series of smaller shortwaves will lift northwards and track across Southern Manitoba.

Tonight, an area of light snow will develop along the RRV in North Dakota and slowly lift northwards into Winnipeg. This area of snow will slowly fizzle out over the region before being replaced by a more organized area of snow that will push across Southern Manitoba as the main low tracks across the Southern Prairies. By Thursday night, we’ll be back under steady snowfall.

24hr. QPF

24hr. Precipitation Accumulation valid 12Z Friday morning, March 2nd.

The entire system will exit the region overnight on Friday. Snowfall totals west of the Trans-Canada highway will be general amounts near 5cm. Areas in the RRV and east into the Whiteshell will see more, with widespread accumulations of 5-10cm and localized amounts potentially reaching as high as 12-13cm. These amounts are estimates right now, and we’ll certainly see how things shape up over the next day and a bit.

After this system clears out we’ll have a bit of an unsettled weekend with the potential for some light flurries as a weak low pressure system tracks through Central Manitoba. The next potential for snow comes on Monday as another powerful low pressure system tracks through the Prairies. More on that on the weekend!