Monday, August 30, 2010

Thunderstorms, heavy rain likely over southern MB this afternoon/tonight.. severe storms possible southeast

A sharp frontal zone over southeast MB today combining with a wave of energy moving in from the southwest will lead to the development of showers and thunderstorms over southern MB today into tonight, with areas of heavy rain likely as well as the potential for locally severe thunderstorms with hail and strong winds mainly over SE Manitoba. Heavy downpours are likely with thunderstorms, with rainfall amounts of 20-40 mm in a short period possible over southern MB including the RRV. Locally higher amounts are possible where storms regenerate over the same area. The activity is expected to merge into a large area of heavy rain mainly north of Winnipeg through the Interlake regions tonight where 50-75 mm is possible by Tuesday.

Saturday, August 28, 2010

Warm air returns Sunday mainly south and east of Winnipeg..

A sharp frontal zone over northern North Dakota brought cloudy skies and rain over the Red River valley today, keeping afternoon temperatures only in the mid teens.. some 15C cooler than 24 hours earlier. On Sunday, this frontal zone will move back north as a warm front to lie across southern Manitoba by afternoon. Current indications are that this frontal zone will lie just south and east of Winnipeg Sunday afternoon, with temperatures reaching 30C south of this boundary over the southern Red River valley and southeast Manitoba. (see Sunday afternoon NAM temperature forecast image) Temperatures will be sharply cooler north and west of this front, with highs only in the mid teens to 20C along with occasional showers. At this point, it looks like most of this shower activity should stay north of Winnipeg.. good news for the final day of the LPGA golf tournament. However, the frontal zone will be close enough to the city to keep a threat of some showers, along with temperatures in the low to mid 20s (if we get some sunshine, 20c if we stay cloudy) This frontal zone will become stalled over the Red River valley Sunday night into Monday night with showers and thunderstorms moving in giving the potential for locally heavy rain as storms "train" along the stalled frontal zone.

Thursday, August 26, 2010

Windy and warm again then unsettled by Sunday..

Windy and warm weather is moving back into southern MB as an increasing southerly flow returns to the eastern Prairies. Today will see plenty of sunshine with highs in the upper 20s as southerly winds pick up in the 30 km/h range. Friday will be even windier and warmer, with gusty south winds of 40 to 60 km/h pushing temperatures into the low 30s over the Red River valley. A weak front will pass through southern MB Friday night bringing slightly cooler but pleasant conditions Saturday along with light winds. By Sunday, low pressure developing over the western Dakotas will bring a warm front along the US border which will be the focus for scattered showers and thunderstorms Sunday into Sunday night. More showers and thunderstorms are likely by Monday as the main low moves across the border with cooler conditions moving in behind this system for early next week.

Saturday, August 21, 2010

Increasing winds and heat for Sunday..

Perfect weather today will give way to more uncomfortable conditions Sunday as a strong southerly flow of hot and more humid air spreads into southern Manitoba. A developing low pressure system over Montana will push a warm front across southern MB overnight into Sunday morning with a few thunderstorms likely along the front, especially north and west of Winnipeg. As the warm front pushes north, gusty southerly winds of 40 to 60 km/h will develop over southern MB Sunday tapping a very warm airmass over the Northern US plains. Temperatures of 32-35C are likely across southern MB and the RRV by Sunday afternoon, with humidex values of 40-43C. The hot and windy conditions will continue through Sunday evening with temperatures likely remaining near 30C through midnight. A sharp cold front will cross southern MB Monday bringing showers and thunderstorms along with cooler temperatures.

Monday, August 16, 2010

Cool start to the week.. warming up by the weekend ..

Cool temperatures will dominate the weather picture over southern MB over the next few days before a nice warm-up by the weekend. Today at least will feature sunshine which will offset the below normal temperatures. For Tuesday, a quick moving clipper system will bring increasing clouds and a few showers across southern MB, with temperatures only in the upper teens. This system will clear out Tuesday night with sunshine returning Wednesday but a continuation of below normal temperatures. Thursday should start to see some moderation in the weather pattern with warmer air moving in for Friday as temperatures climb back to normal. The weekend is looking summer-like again with highs close to 30C along with increasing humidity and a threat of thunderstorms.

Friday, August 13, 2010

Torrential early morning thunderstorm swamps Winnipeg

After 5 days of heat and humidity, Mother Nature unloaded over Winnipeg early this morning with a torrential thunderstorm that swamped the city with heavy rainfall. The storm moved in over the southwest part of the city by 5:40 am, and within 30 minutes had dropped about 40 mm of rain over much of the city. The heavy rainfall caused numerous problems in the city with traffic light outages, flooded underpasses and manhole covers being blown off by the tremendous rainfall rates.

The photo here (from Mike O'Flaherty to CJOB) shows the storm approaching the city from the west before 6 am. At my weather station in Charleswood, I recorded 33 mm of rain between 5:40 and 6 am, with a total of 41 mm by 6:40 am. Winnipeg airport recorded 43 mm of rain while the Forks had 40 mm downtown. The University of Winnipeg weather station recorded 57 mm between 5:50 and 6:50 am. Lesser amounts of 20-30 mm were recorded over the southern parts of the city. (click here for city of Winnipeg rainfall map) The thunderstorms signaled an upcoming change in the weather pattern, with cooler weather moving in for the weekend into next week.

Radar image from 6 am showing
intense cell over Winnipeg.

Wednesday, August 11, 2010

Thunderstorms likely Thursday.. cooler weather for the weekend..

Warm and humid conditions will continue over southern MB for the next couple of days before a significant change to cooler weather this weekend into next week. The next threat of thunderstorms will be pushing into southern MB Thursday, spreading into the Red River valley by late afternoon and evening. Once again, a band of showers and thunderstorms are likely, with locally heavy rainfall possible. Some storms may be severe with strong wind gusts and hail. This activity will move out Thursday night with variable conditions for Friday. By Friday night, a cold front will sweep through Southern MB, with gusty northwest winds ushering in cooler air from northern MB. This front will signal a change to cooler and less humid conditions for the weekend into next week, with daytime highs only in the upper teens to low 20s.. a refreshing change to the hot and humid conditions of the past week.

Monday, August 09, 2010

Humidex advisory issued for southern MB.. temperatures of 32-35C today with humidex readings of 40-43C

A humidex advisory has been issued for much of southern MB today including Winnipeg as a hot and humid airmass spreads over the eastern Prairies. Temperatures today are expected to climb into the 32-35C range this afternoon over southern MB, with dewpoints around the 20c mark. This will result in widespread humidex values of 40-43C this afternoon, with local readings of 45C possible. Winnipeg should hit 33C this afternoon, with a chance of reaching the 35C mark. This should make today the hottest day in the city in 3 years since a 35.3C reading on July 29 2007, and the hottest August temperature in 7 years (35.9C on Aug 19 2003) Today will mark the peak of the heat spell, as unsettled conditions with cooler weather is expected beginning tomorrow.

Thursday, August 05, 2010

Hot spell forecast for next week.. locally strong thunderstorms possible Saturday into Saturday night

Models are cranking up the heat beginning this weekend, and continuing much of next week. A warm front is forecast to push through southern MB on Saturday, which could trigger some heavier thunderstorms especially by Saturday night. (Note that SPC is indicating a slight risk of severe storms for Saturday over the northern Plains. Models hint at potential for strong elevated thunderstorms Saturday evening/night anywhere from North Dakota into central MB) We start getting into the steambath on Sunday with hot and humid conditions as the warm front pushes north of us, with afternoon highs of 30-33C and humidex values near 40. The hot and humid conditions are expected to persist through Thursday with daily highs in the 30-33C range before a cold front sweeps through late in the week with cooler air by next weekend. Although much of next week should be generally storm free as warm air aloft caps thunderstorm development over southern MB, there is a chance of daily scattered thunderstorm activity as weak impulses ride the upper ridge, especially through the Riding Mtn/Interlake areas. All in all though, looks like a steamy stretch of weather coming up, with potentially 5 straight days of 30C plus weather next week.

Wednesday, August 04, 2010

A couple of cool days ahead.. then warming up for the weekend..

Cooler weather is on tap today and Thursday as a northwest flow brings in a cooler airmass from northern Manitoba. Temperatures will only be in the low 20s today and Thursday along with a chance of showers today and tonight. (Temperatures may even be cool enough for some narrow bands of lake effect showers to the southeast of Lake Winnipeg and Lake Manitoba overnight into Thursday morning) Things will improve by Friday as high pressure builds in with sunny skies, light winds and more seasonable temperatures. Warmer and more humid weather is expected for the weekend as temperatures climb back into the upper 20s. The increased warmth and humidity however will once again bring the threat of thunderstorms over southern MB, especially Saturday night and Sunday. Long range guidance is hinting at very warm weather for much of next week, with high temperatures in the 30s across southern Manitoba.