Rain and Thunderstorms for Next Week

The soggy spring we’re experiencing in Southern Manitoba just doesn’t seem to be letting up.  With some areas in Southeast Saskatchewan and Southwestern Manitoba already having seen in excess of 2/3s of what they normally receive through an entire year, everybody, including the ground, is ready for a break from the rain.  Unfortunately, it doesn’t look like it’s in the cards.  A sunny and warm weekend will change into quite an unsettled pattern for the first half of next week.  Read on to find out where and how much rain will fall.

24hr. QPF valid 12Z Monday morning from the 00Z Friday Jun 10 GEMGLB model.

Enjoy the sunshine and warmth today and tomorrow!  Plenty of sunshine is in store for us with daytime highs in the low twenties and fairly light winds.  Most of Sunday will be pleasant as well, but by evening a new system is going to be pushing into Southwest Manitoba.

An trowal will swing through Southern Manitoba Sunday night through Monday, bringing with it another batch of rain and thunderstorms.  By Sunday evening, rain will begin to push into Southwest Manitoba with a chance of thunderstorms developing before midnight.  While much concern exists about the more rainfall for SW Manitoba, it looks currently like the greatest threat for heavy rain exists from areas south of Winnipeg and spreading eastward through the Whiteshell.

As the trowal rotates into our area on Sunday, an area of thunderstorms should rapidly develop on Sunday evening in North Dakota near and east of the triple point of the associated wave.  For those who don’t know what that is, the triple point is the point where the warm front and the cold front meet.  This should develop upscale quite rapidly into a large MCS that will track east northeast and should cross into S. MB overnight.  Currently, it appears that Winnipeg would be on the northern edge of the higher amounts, with it likely that areas south of the city could see 20-40mm of rain.  Areas elsewhere in Southern Manitoba (including the Southwest corner) that are not impacted by the MCS from North Dakota will see between 10 and 20mm of rain through Monday evening.

This system will then pull northward and rotate into Central Manitoba.  Unfortunately, this prolonged period of rain could bring an additional 20-30mm to the absolutely soaked Interlake region, which is battling un-before-seen high lake levels.

Perhaps of even bigger concern is the next system that will barrel into Southern Manitoba on Wednesday evening.  While details are sure to change, this has the potential to be the most significant convective system we’ve experienced this year.  An extremely intense shortwave will head northeast into North Dakota through the day on Wednesday and initiate a large area of convection by Wednesday evening.  This convection will be pulled northward with the shortwave as it slowly becomes captured in an upper low and rests over the western lakes.  

12hr QPF valid 12Z Wednesday morning, June 15 from the 00Z Friday June 10 GEMGLB.

Thunderstorms will develop and intensify through an upper trough and pull northward into the upper low, resulting in prolonged, intense precipitation along a fairly narrow band.  Positioning will be crucial for this system, but with the potential to be dumping 1.5” – 3” of rain through the RRV into the Interlake, this will be a extremely important system to keep an eye on.

So get out and enjoy the sun!  As summer tries to push in next week, the storm track is going to move back into Southern Manitoba and we are likely going to see several impulses move through during the week.

Significant Storm System Heading into Manitoba

A powerful early-summer storm system has pushed through Montana overnight and pushed into Southwestern Manitoba, bringing with it heavy rain and widespread thunderstorms.  Read on to find out what’s in store for today, and where there might be severe thunderstorms…

0845Z 10.7u/3.9u Multispectral Satellite Imagery; a extremely large area of thunderstorms covers most of Southern Saskatchewan, the northern half of Montana.  This system also has an arm of convection that extends west-east across northern North Dakota approaching the international border.  This system has brought nickel sized hail to the Estevan region and 90km/h wind gusts to northern Montana.

A significant storm system ejecting from the Rocky Mountains intensified rapidly overnight and has produced widespread thunderstorms throughout southern Saskatchewan.  This system will move eastwards through the day today, pushing precipitation through Manitoba.

The setup today is quite complex.  There is a surface low running near the international border that is connected to the upper-level impulse.  These two features are acting in tandem to produce much of the convection in Saskatchewan this morning.  Further to the southeast, a surface low is entering into western North Dakota with an associated frontal wave attached to it.  A warm front extends through southern North Dakota and across central Minnesota, with a cold front laying south from the low pressure centre along the Montana/Wyoming – Dakotas boundaries.

1000Z Radar Composite for the Prairies

So!  For Southern Manitoba today.  The band of thunderstorms stretching from Melita-Virden to Emerson should continue through the early morning hours, but will be sheared apart by mid-to-late morning as the western portion of the line is pulled westward around the upper low and the eastern half is pushed further east by a significant low-level jet.  I think that there will be thunderstorms up to a line that lay from Portage la Prairie – Winnipeg – Kenora.  North of that line (including Portage and Winnipeg), I’d say that there’s a good chance of some showers this morning, but only a slight risk of a thunderstorm as the line is weakened through the stretching as well as the morning sun.

After that line passes, we’ll see a relatively cloudy lunch and early afternoon.  During this period, the warm front in North Dakota will have advected northward and lay fairly close to the Canadian border.  By mid-afternoon, convection will initiate south of the border along the warm front, caused by daytime heating and increasing instability as the upper centre approaches.  These storms will probably become marginally severe to severe quite quickly, with the main threat being large hail.  There is a slight chance that storms right near the warm front could produce tornadoes.

I think that the worst should stay south of the border, but it’s highly dependant on how far north the warm front can push.  The SPC agrees with me, and has pushed their slight risk area into Southern Manitoba, with concerns that the worst could actually occur on our side of the border.  I’d advise anyone living within 75km of the border in the Red River Valley and east to keep an eye out for weather watches or warnings this afternoon.

24hr. precipitation accumulation valid 12Z Wednesday morning from the 00Z June 7 GEMREG model.

Storms that initiate along the warm front should become elevated this evening, as they become support by a strong low level jet overrunning the warm front.  As the upper low moves across Southern Manitoba, it too should support an area of convection due to significant instability aloft.  All this will move through overnight, giving rain and thunderstorms to many areas in Southern Manitoba.  Rainfall amounts may vary significantly depending on convection, but general widespread amounts will likely be from 15-25mm, with areas that get battered by thunderstorms potentially seeing 30-40mm.

We should see some light rain tomorrow morning through the RRV and points east as the system pulls out, with skies beginning to clear through the afternoon.  After that, it looks like we’ll have at least a few days without rain before the next system moves through!

Just enough time to mow the grass.

Enjoy the sun today and tomorrow because guess what, more rain is on the way.

June 3, 2011 Hand-Analysis of 12Z Sounding Data; Black lines are heights, coloured lines are θw values.

The broken record keeps on repeating in Winnipeg as rain gives way to sun gives way to rain with just enough time to mow the grass in between.  With the system that brought numerous damaging storms across Southern Manitoba yesterday moving out, the upper flow aligns itself to place the Southern Prairies directly along the main storm track.

Convective outlook for June 3, 2011.

Little significant weather is expected in Southern Manitoba today, with only the slight chance of a thundershower or two over the Parkland areas, mainly in the northern Minnedosa and Dauphin regions.  Sunny skies will prevail through the evening for areas in the Red River Valley and east before a few clouds move in overnight.  Get out there and enjoy the beautiful weather!

24hr. cumulative precipitation valid 12Z Sunday 5 June from the 12Z 3 June GEMREG; my personal opinion is that it drags the precipitation a little too far south across the Prairies and that the streak through Southern Manitoba will likely be further north.

Things change by tomorrow evening, though.  A new system currently moving into the Prairies from the Yukon Territory will arrive in the Southern Prairies by tomorrow afternoon and into the Red River Valley by tomorrow evening.  This system will produce a lengthy trail of precipitation, however it’s north-to-south width looks fairly narrow.  The exact position of this shortwave will determine where precisely the rain will fall, although all indications currently point to another 2-4mm of rain pushing through the Winnipeg/Gimli/Selkirk/Whiteshell areas with lesser amounts further south.

This precipitation looks to clear out by Monday morning, leaving behind general instability through the region due to an elongated surface trough hanging back from the main system.

The sun will then come out (hopefully) in full force Monday afternoon and Tuesday morning, before cloud moves back in on Tuesday afternoon ahead of yet another low pressure system.

12hr. cumulative precipitation valid 12Z Wed 8 June from the 12Z Fri 3 June GEM-GLB

This third system within a week will push in on Tuesday evening with a warm front positioned just south of the international border, draped west-to-east across North Daktoa.  Some light rain with the risk of elevated thunderstorms riding over the warm front with push into our area by Tuesday evening before developing into a large area of moderate rain overnight.  It looks to rain through Wednesday and most of Thursday night before tapering off on Thursday morning.

This system is still a ways off, so we’ll fire off another blog post in a couple days with some more details on that one.  We’ll update Sunday’s system right in the comments here.

Do you have any stories or pictures from the storms yesterday?  Feel free to leave them in the comments or fire a tweet off to our official Twitter account, @WeatherInThePeg.

Showers and Thunderstorms, U2, Then More Rain

While the temperatures may not be completely summer-like, today will be a day that indicates a clear shift towards summer weather.  An incoming disturbance will produce widespread convection today with showers and thundershowers covering much of Southern Manitoba.  Pleasant weather should make an appearance for tomorrow’s U2 concert, but Winnipeg will quickly return to rainy weather on Monday as a system that will bring significant challenges to those with housing near the lake moves into the province.

A substantial stacked low pressure system currently positioned just east of Regina is set to move across Southern Manitoba today.  A few factors will combine to produce what could be a fairly interesting afternoon today.  

First, a southerly wind, combined with yesterday’s rain has pushed dewpoints to nearly 10°C throughout the Red River Valley with a relatively deep layer of evidenced by the stratus cloud that has managed to form overnight despite winds of 15-20km/h.  This moisture will provide the fuel needed for thundershowers. 

Secondly, rather cool mid-level temperatures will be in place.  As the low pushes in, temperatures in the mid-levels should drop to -7 to -8°C, which when combined with daytime heating will produce ample instability to get convection initiating.  It is also indicative of fairly low freezing level, which will help in the generation of small hail.

And last but by far not least, the fact that this upper disturbance is stacked on top of a surface low means that there will be significant rotation through the mid and upper levels which will help storms develop rotation.

When these things combine, it’s considered a pretty classic case for cold core funnels.  These funnel clouds do not develop in the classic sense; instead of developing in the rapidly rotating updraft of supercell thunderstorms, they develop through the descent of cold air through a storm that has developed rotation due to significant mid-to-high level spin.  Think of it as a funnel cloud that develops because of how air is coming out of the cloud rather than how air is being ingested into the cloud.

These funnel clouds do have the potential to touch down and become tornadoes.  If they do, they are often extremely short lived (< 1-2 minutes) and are much weaker than the tornadoes that form from supercell thunderstorms.  Any of the storms that could produce a cold core funnel cloud are also extremely likely to be capable of producing hail.

I think that most areas across Southern Manitoba could see hail today, although the threat is biggest in the Red River Valley and east.  Winnipeg and areas south should most likely see pea-sized hail should it develop.  Further east in the Whiteshell and Sprague regions, the potential exists for marginally severe hail (about dime to quarter-sized).

The biggest hindrance to the development of all this is the lack of focus for convection.  With no strong front or trough, convection may simply blow up all over the place instead of in any organized fashion, which will leave all the storms fighting each other for resources.  If this happens, it’s likely that it would quickly blossom into a big area of showers with only the odd lightning strike.

My bet for the Red River Valley is this: low stratus this morning will burn off quickly with the morning sun.  By mid-morning, most areas should be seeing a mix of sun and cloud.  Daytime heating, combined with a weak cap, will initiate the convection earlier than typical, resulting in showers spreading into the Red River Valley around 12-1PM or shortly thereafter.  Any showers that develop in the RRV are just as likely to become thundershowers, and I think there will be numerous funnel clouds today.

As for Sunday and the big U2 concert, it should be quite a pleasant day.  We’ll see a sunny morning give way to a mix of sun and clouds in the afternoon with a daytime highs around 15-17°C.  It will cool off quick in the evening, so make sure to bring a sweater if you’re headed to the concert.

12hr. QPF valid 06Z May 31 from the 06Z May 28 GFS

After that, it looks like a significant low pressure system will track through Southern Manitoba, bringing nothing but headaches and grief for residents on the lakes.  Current indications are for a widespread area receiving 20-40mm of rain with winds potentially as high as 50 gusting to 70 km/h.  This system will do no good for the flood-striken areas near the lakes, and I would suggest that residents in the area should begin to make preparations already as with the strong winds out of the north-east, significant water damming will likely occur on the western to southern beaches.