Wednesday, July 13, 2016

Cool wet weather to give way to drier warmer conditions by weekend into next week

Departure from normal precip (mm) across Prairies since
Apr 1st. It's been notably wet across the far south
The frustrating weather pattern that has plagued southern Manitoba with frequent precipitation events over the past 6-7 weeks continues to linger into mid July with yet more rain today. A large storm system tracking through northern Manitoba will bring cool, windy and unsettled conditions throughout southern Manitoba today, making it seem more like a day in mid September than mid July. But once this system finally starts to move eastward tomorrow, a gradual improving trend is expected later this week through the weekend and possibly through much of next week with a warmer and drier pattern setting up. Long range models are indicating the development of a massive dome of hot and stable air that will be setting up over the central US plain states next week, that hopefully will edge northward into southern Manitoba. The core of the heat will be south of the international border over states like Iowa, Nebraska and South Dakota where temperatures of 35-40C are likely in what will be an extended heat wave next week. Some traditionally hotter spots there may be seeing temperatures as high as 43C (110F)  In Manitoba, temperatures will likely be above normal with temperatures of 25-30C expected with a trend towards less frequent shower and thunderstorm activity. However, given that southern Manitoba is expected to be lying on the northern edge of the heat dome, there will likely be periodic thunderstorm activity as impulses round the upper ridge (aka "ridge riders")  One potential type of severe weather threat with this type of upper pattern is the "derecho" - a cluster of powerful long lived thunderstorms that ride along the periphery of the upper ridge and produce widespread wind damage along its path, often at night.   

 Large upper ridge expected to dominate weather pattern over central US next week bringing widespread heat over much of the US edging into southern Canada 

A pattern change to drier and warmer weather is desperately needed over southern Manitoba. After a dry start to the growing season, the overall pattern turned wetter and more unsettled in late May and has persisted through much of June through the first half of July. Some places in the Red River valley have seen over 2 times the normal precipitation since June 1st. Lettelier for example has recorded a whopping 313 mm of rain from June 1st to July 12th, some 260% of normal. Since May 23rd, Winnipeg (and much of southern MB) has had only one stretch of 4 or more days with no measurable rain (June 13-16) otherwise, rain has been occurring every other day or two over the past 6 weeks, often heavy at times. Farmers are hoping that drier and warmer weather will salvage what could be a very good crop this year.


Monday, June 06, 2016

The week ahead.. cool start with a hot and stormy finish

The weather in southern Manitoba this week will see a transition from a cool fall-like start to a more summerlike pattern by the end of the week, complete with increasing heat and humidity as well as the risk of potentially severe thunderstorms by Thursday or Friday.  Highs today will only top out around 19C, some 5C below normal for early June, but by Friday, Winnipeg and the RRV could be looking at temperatures close to 30C. The increasing heat and humidity along with a couple of weather systems tracking across southern Manitoba will lead to the development of scattered thunderstorms, some of which may be severe. Stay tuned through the week as this developing weather situation evolves.   

Sunday, May 29, 2016

A brief dry period.. then another round of showers and thunderstorms on the way Monday night into Wednesday. Areas of heavy rainfall likely especially over southwest Manitoba

It's been a wet week over much of southern Manitoba this past week. Since last Sunday (May 22) general rainfall amounts of 40-70 mm have fallen across much of southern Manitoba, with locally heavier amounts in some places. (I've recorded 70 mm at my site in SW Winnipeg since last Sunday night)  Today saw a welcome break from the unsettled weather with partly sunny skies this afternoon, and we'll enjoy rainfree weather much of Monday before another bout of wet weather moves into southern Manitoba.  The culprit this time will be a developing low pressure system over North Dakota which will spread showers and thunderstorms over southwest Manitoba later Monday into Monday night, moving into the Red River valley Monday night into Tuesday.  The heaviest rain is expected Monday night into Tuesday morning.

Projected rainfall totals (inches) Mon-Wed. Heaviest
rainfall expected over SW MB with 75 mm possible
Rainfall from this system will be highly variable since localized areas will see heavier amounts from slow moving or persistent heavier shower or thunderstorm cells. Places which miss the heaviest convection will see lower amounts. In general, most places in southern Manitoba will likely see 20-30 mm of rain Monday night into Wednesday morning, with heavier totals of 50-75 mm possible in some areas.. especially over the southwest corner of the province (Melita, Virden, etc) where current guidance is indicating the greatest probability of heaviest rainfall.  At this point, one should focus on the potential for heavy rain over the next few days instead of the exact location.. which will likely change slightly as models try to predict the track and intensity of this system.

Sunday, May 15, 2016

After a chilly weekend.. things looking up this week.

It was a chilly weekend over southern Manitoba with high temperatures only near 11C Saturday, and 15C today along with some showers.  But the rest of the week is looking up as the cool airmass moves east and a warmer upper pattern re-establishes itself over the Prairies.  The result will be a warmer and drier week coming up with ample sunshine and highs back to the 20C mark by Tuesday, and mid to upper 20s by the end of the week.  The early outlook for the Victoria Day long weekend looks warm and increasingly humid with a chance of showers and thunderstorms by Monday.  

Monday, May 09, 2016

Warm start to week with a cold finish.. and some rain in between..

It's been a summery and dry start to May in southern Manitoba with plenty of sunshine and warm temperatures. As of Sunday May 8, the monthly mean temperature for the month has been 14C in Winnipeg, about 3-4C above normal for the first week of May.  And the warm weather is expected to continue Monday with another sunny but hazy, breezy and dry day, and highs of 25C.  But that will be the end of the warm weather for awhile as the upper weather pattern shifts this week to bring cooler and more unsettled weather into southern Manitoba.  Tuesday will see a band of showers sweep across southern Manitoba ahead of a deepening storm system over Montana and Dakotas.  Scattered showers are expected Wednesday as the storm system slowly tracks across southern Manitoba, before cooler weather arrives Thursday behind the system with northwest winds and occasional rain keeping temperatures only near 10C.  The rain should pull off Friday, but temperatures will be quite chilly with highs only in the single digits of +5-8C, quite a contrast to the how the week started in the mid 20s.

But we can use the rain. Today marked the 3rd straight week with little or no rainfall in Winnipeg and much of southern MB. Preliminary guidance is indicating that 10-20 mm of rain is possible between Tuesday and Thursday across Winnipeg and the RRV. And at this point, not too many people will be complaining considering how dry things have been. In fact the dry weather has led to a couple of large wildfires near the Ontario/Manitoba border over the past few days, and Monday will see high risk fire weather conditions with gusty southeast winds, warm temperatures and low humidity.