Cooler Air Pushing Southeast Across Southern Manitoba

Brad Leave a comment

The powerful low pressure system that has brought rain to Winnipeg over the past couple days and is bringing 10-20cm of snow to portions of Northern Manitoba has pushed north and east of the Red River Valley, setting the stage for cooler air to filter into the region.

700mb Temperatures for Thursday Morning

NAM forecast of 700mb heights & temperatures valid Thursday morning.

The Red River Valley will be moving into a strong northwesterly flow aloft that will advect cooler air into the region. While earlier in the week, models were projecting a very potent arctic blast, things have become a little more pleasant due to a more significant amplification of the upper-level pattern. The net result of this is a cut-off upper low over the central Prairies that will, in effect, block the coldest air from being able to push southwards. This will give us more cloud than sun with daytime highs near 5 or 6°C through the rest of the work week.

The upper low begins to push eastwards for the weekend, allowing slightly cooler temperatures to the area for the weekend, with highs near 0°C, and a chance of some light snow. Accumulations will be light-to-none throughout the RRV, however a few cm may pile up in the Interlake region.

More Active Weather

Brad Leave a comment

More active weather is in store for this week with multiple chances for precipitation. The question is whether that precipitation will be solid or liquid.

Low pressure system passing to the south-east on Thursday

A low pressure system is currently expected to pass to our south-east on Thursday, generating minimal impacts in Manitoba

The weather to start the week will be fine, with temperatures generally in the high single digits on Monday and perhaps a few double-digit readings here and there. There will be increasing cloudiness during the day as a weather system approaches. This system will begin to spread rain over Southern Manitoba on Monday night with precipitation persisting into the day on Tuesday. Highs on Tuesday will remain very similar to Monday, but the rain will make it a considerably more miserable day. Total accumulations from this system will generally range from 5 to 15mm. As Tuesday’s system departs our region on Wednesday, cooler air will sweep in from the west making for a chilly and windy middle of the week. Temperatures on Wednesday will be in the mid single digits with a gusty west wind.

There has been much talk about the weather for later this week. Some models have been showing a significant Colorado Low system hitting portions of Manitoba on Thursday and Friday. However, other models show little or no precipitation for us later this week. At this point the consensus seems to be that it is unlikely Southern Manitoba will be getting a major blizzard later this week. Most models depict a moderate strength low system sliding past us through Minnesota and up into North-Western Ontario, perhaps bringing a few flurries or rain showers to Southern Manitoba, but not a major winter storm. Some models still show a fairly deep low pressure system to our east over Northern Minnesota and North-Western Ontario later this week, but it looks like it will be sufficiently far away to prevent us from seeing its main impacts. So at this point it appears unlikely that we’ll be seeing any significant amount of the white stuff later this week. However, expecting the unexpected as always a good saying to live by in the weather business.

Elsewhere in Weather News: October 20th, 2012

Matthieu Leave a comment

Severe Weather Outbreak in Dixie Alley

This past Wednesday evening a severe weather outbreak comprised of severe winds and strong tornadoes occurred in the southern United States, causing damage to rural areas of Northern Mississippi. This was brought on by the same system we experienced over the past couple of days. The polar jet stream along with a strong low level jet overhead and plenty of moisture from the Gulf of Mexico combined to create conditions ripe for tornadoes in Dixie Alley.

Trough

500mb heights/temperatures with trough (arrow) and circled area where the tornado outbreak occurred. (Source: Twisterdata)

The strongest, a half-mile tornado, rated EF-3 by the National Weather Service, touched down near Jackson Mississippi and caused quite a bit of damage, tearing up large trees and wrecking mobile houses. As the tornado trekked for 26 kilometers, nine people taking cover inside mobile houses were injured but thankfully no fatalities occurred during this event. As the night wore on, more tornadoes touched down in Mississippi and Arkansas, doing damage to rural homes and cutting off power to residents.

Tornado damage

Tornado damage in Leake County, MS. (Source: WLBT)

A few colder days will follow the trough this weekend and a return flow will set up, bringing warm and humid weather back to the region. Weather models are showing another large trough will likely develop late next week, bringing the potential for more dynamic weather. Of course, it is not uncommon to have severe weather in the southern US during the spring and fall, when the polar jet is in the vicinity.

Elsewhere in the world the weather has remained relatively calm, except for this unusual tornado in France.

Video of the tornado in Marseille, France. (Taner Ozdil)

Tornadoes in France are not rare but are not a common sight in October.

Lingering Showers Give Way to Unsettled Weekend

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A few lingering showers will persist through the Red River Valley this morning as the low pressure system that has been bringing us rain the last couple days slowly pushes eastwards. Conditions won’t improve too much, however, as we’ll be dealing with unsettled weather, albeit a little dryer, through the weekend.

Rainfall accumulations through the day today.

This 12 hour rainfall accumulation map shows the total rainfall that the RDPS model is forecasting for the daytime today.

Showers will slowly taper off through the Red River Valley today from west to east with only a further 2-4mm in rainfall accumulations. This system has brought hugely varying rainfall amounts across the RRV, with general amounts from 20-60mm across the Red River Valley. After spending several months in a row with below-normal precipitation, this system has pushed Winnipeg back to above-normal accumulations for October, which will begin to chip away at our deficit for the year. Winds will also taper off through the day today as we move to a high of only 7 or 8C.

Saturday will be a mainly cloudy day with a slight chance of showers and a high near 11C.

A frontal wave pushes across Southern Manitoba on Sunday, occluded from the parent low that will be captured over Northern Saskatchewan by an upper low in the area. Some uncertainty exists to the amount of precipitation associated with this wave as it moves through. Some models have next to no precipitation, while the GDPS is suggesting as much as 10-15mm of rain. My personal feeling is that we’ll likely see some rain push through with general amounts in the 4-8mm range across much of the RRV. We’ll keep an eye on this system and provide some updates through the weekend in the comments below. Sunday will likely be mostly cloudy again, with a high near 10C.

The biggest weather feature next week looks to be the potential for a significant low pressure system to push into North Dakota, bringing rain, snow, and potentially blizzard conditions to the Red River Valley for the second half of the week. That’s a long ways away, though, and a lot can change between now and then. We’ll be sure to follow this potential system closely through the week ahead.