Tag: cold

A Return to Winter

Brad Leave a comment

Colder air is set to return by the end of the week as a low pressure system ushers in Arctic air as winds shift to the northwest behind it.

GFS Sounding for 06Z Thursday

A sounding for 06Z Thursday (midnight-ish tonight) from the GFS model depicting an above-freezing level.

Before the cold weather returns we’ll have one more pleasant day. Although skies will be cloudy today, we’ll see temperatures once again climbing above 0°C through the Red River Valley with a light southerly flow. Conditions will begin to degrade overnight as a low pressure system pushes into Southern Manitoba.

The first threat with this system will be the potential for freezing rain tonight. As the sounding1 above shows, an AFL (Above Freezing Level) with sub-zero surface temperatures will be in place through much of the overnight period before eroding early Thursday morning. The saving grace for the Red River Valley could be that most of the precipitation looks to push north of the valley through the Interlake. If, however, any precipitation manages to wander through the RRV overnight, then there’s certainly a decent chance it’ll fall as freezing rain. Cooler air begins pushing in at all levels early Thursday as we move to the back side of this system and winds switch to the northwest.

Winds will strengthen out of the northwest on Thursday to 40km/h with gusts towards 60km/h as a band of snow slumps southwards with the cold front. At this point, it looks like snow will push into the Red River Valley mid-morning and last until the early evening (6-8PM). Snowfall accumulations will likely be around 5cm. Temperatures will start near -5°C tomorrow morning and fall to -8 or -9°C by the evening. We’ll head to an overnight low of around -15°C tomorrow night.

Sunny skies should dominate Friday and Saturday with highs near -10°C. A weak disturbance looks to bring a chance of light snow to the Red River Valley again on Sunday.

  1. A “sounding” is a way of plotting how the temperature and dewpoint change with height. The sounding is for a single location and plots the temperature/dewpoint with height in pressure coordinates as the vertical axis. ↩

The Calm After the Storm

Brad Leave a comment

After a weekend laced with active weather all over the Prairies, we will go into a much more subdued pattern for this week. But unfortunately, it doesn’t look like the snow is going anywhere fast.

Cold temperatures are expected on Monday morning in Western Manitoba

Cold temperatures are expected on Monday morning in Western Manitoba

The weather to start the week looks cool to cold, but fairly uneventful. The main story may in fact be the low temperatures, with very cold values expected. On Sunday morning Coronation, Alberta plunged down to -29C! In Southern Manitoba our lows don’t look to be quite that extreme, but if skies clear out as expected some -20C readings may appear in Western Manitoba this morning. In the Red River Valley our daytime temperatures won’t moderate much from this morning’s lows, with temperatures basically flat-lining throughout the day in the high minus single digits or low minus double digits. It looks like we’ll get down into the low minus teens on Tuesday morning, with widespread -20s not looking too likely at this point. By Tuesday afternoon it looks like we’ll climb up to the mid minus single digits, which should be fairly pleasant given the lack of wind. On Wednesday models suggest that we could get up to the freezing mark, though they may not have a great handle on the new snow cover, so I’d assume our temperatures will remain slightly below zero for now.

No significant weather is in store for the late week period, just more typical mid-November conditions. Long-range models hint at warmer than normal weather returning to Manitoba later this month, but those predictions should be taken with caution for now as our new snow cover may not be properly accounted for yet.

What a Difference a Week Can Make

Brad Leave a comment

The difference between the weather experienced last week and that which is coming for early this week will be quite extraordinary. Temperatures on Monday look to be nearly 20 degrees cooler than values experienced last week.

850mb temperatures (about 5000ft above the ground) are forecast to sink to near or below zero degrees on Monday

850mb temperatures (about 5000ft above the ground) are forecast to sink to near or below zero degrees on Monday

High temperatures on Monday are not expected to stray far from the 10C mark in Southern Manitoba. Eastern most sections in the south may manage to hit the mid teens, but the rest of Southern Manitoba shouldn’t be much warmer than 10 degrees. This comes as quite a contrast to the 30 degree temperatures of last week. The above graphic shows the extent of the cold air, with freezing temperatures just 5000 or so feet above the ground. We will most likely see some shower activity develop across Southern Manitoba on Monday, but amounts should be relatively light in most areas. Thankfully Tuesday and Wednesday will be warmer, with highs moving sharply higher. Tuesday should be near or above twenty degrees (depending on which model you believe), while Wednesday is expected to be in the low to mid twenties. There may be some convective rain and/or thunderstorms on Wednesday as humidity levels increase ahead of an approaching low pressure system.

The Preliminary outlook for later this week is for more warm to hot weather. Highs back in the middle or upper twenties will be possible on Thursday and Friday according to the latest modelling. However, my confidence level in the late week forecast is lower than normal since there is some uncertainty as to how quickly a series of fronts will pass through the province late in the week. Given my lack of confidence in the Thursday-Friday forecast I won’t say much about the weekend. You can read more about longer range predictions in the next paragraph.

The long-range forecast calls for above-normal temperatures in Southern Manitoba for the second half of June

The long-range forecast calls for above-normal temperatures in Southern Manitoba for the second half of June

The NAEFS forecast seen above shows the long-range temperature forecast for the June 18-25 period. It appears that we will stick with above-normal weather for most of the second half of June. Also note that we are on the edge of the warmest air, meaning that approaching systems coming out of the colder air to our west (a trough) could potentially trigger strong thunderstorms as they interact with the warmer air to the east. This type of trough-meets-ridge pattern is to blame for the severe thunderstorms on Saturday night.

AWM Chases!

The A Weather Moment team took to the highways of Southern Manitoba on Saturday for our first chase of the year. Hot and humid surface weather combined with an approaching low pressure system and a strong jet stream aloft made conditions ripe for severe supercells thunderstorms which could potentially produce tornadoes.

A thunderstorm east of Altona on June 9, 2012

A thunderstorm east of Altona on June 9, 2012

The AWM team decided to drive toward Holland, MB to start the day. After arriving in Holland it was decided that Pilot Mound would be an appropriate new target given the new weather information available. Upon arriving in Pilot Mound and watching the latest weather conditions evolve we felt our location was ideal. At that point it was time to wait…and wait..and wait. After watching numerous towering cumulus clouds fail to breach the cap we decided to abandon Pilot Mound and follow some storms to our east which were approaching the Red River Valley. As we began to get a good visual of the storms around the Altona region it was clear that there was little chance of a tornado. Cloud bases were high and there were no significant lowerings to be found – the storms were elevated – not surface-based tornado producers. Nevertheless we stopped for awhile near Altona to take a closer look at the storms, a look which revealed nothing of significance. Having taken a few anvil and sunset photographs it was time to head back toward Winnipeg, just missing the infamous hailstorm (which put down tennis ball sized hail) that hit the city around sunset.

Overall it was a good chase. It was not a complete bust since there were storms, but it was definitely a bust in the fact that tornadoes were really nowhere to be found (I’ve kept the door open here for you to decide whether or not this is a tornado: http://tornadohunter.ca/tornado-hunter-blog/2012/6/10/the-longest-chase-day-ever-but-we-got-a-tornado.html). It is only early June and the severe weather season is just beginning, the next chase will be here before we know it.

The AWM team (Brad, Scott and Matt) would like to thank the 311 unique visitors who made 624 visits to this website yesterday, a new record number of visits for this website. Thank-you.

A Mild Day Before The Deep Freeze

Brad Leave a comment

Southern Manitoba will see a beautiful afternoon today with plenty of sunshine and highs approaching 0°C in southwest sections of the Red River Valley. This afternoon/evening would be a great time to get out and enjoy the warm weather; a cold front sweeping southwards is going to bring a drastic change on Thursday.

500mb Wind Prognosis

+42 Hour 500mb Winds & Height forecast valid 12Z 09 February, 2012 from the GEM-REG Model

A strengthening upper ridge over the western portion of the continent will organize itself and amplify significantly today and tomorrow. By Thursday morning, it will stretch from Nevada northwards all the way to the Arctic Sea shoreline of the Yukon Territory. As a response, long-wave troughing will be enhanced over the central portions of the continent. Practically, this means that large-scale troughing will be induced in the arctic vortex and rotate around it.

In winter time, long-wave troughs are often associated with cold temperatures and incoming surface ridges of high pressure.

As this long-wave trough rotates from the Kivalliq region of Nunavut through Southern Manitoba, arctic air will be allowed to spill southwards. With this particular upper trough and associated cold front, there appears to be a significant push of cold air: temperatures on Thursday will only recover a degree or two from our overnight low of around -12°C, and temperatures will plummet on Thursday night. Currently, it looks like most areas in the Red River Valley will see overnight lows between -28°C and -32°C on Thursday night, with the colder temperatures east of the Red River and the warmer temperatures west of the Red River courtesy some light downslope winds over the escarpment. Like the previous cold front, very little precipitation is expected with it’s passage.

The normal daytime high for Winnipeg right now is -10°C. The normal overnight low is -20°C.

We’ll be under the influence of this bitterly cold air for a couple days before some warmer air advects into our region from the north again and we return to more seasonal values for Sunday and the start of the new week.