Saturday, May 07, 2011
Unsettled weather moving in Sunday night.. showers and thunderstorms with locally heavy rain possible
Today's scattered shower and thunderstorm activity over the Red River valley was a prelude to what looks to be an active period of weather coming up over southern Manitoba. A strong storm system is forecast to move into South Dakota late Sunday which will draw up a moist and unstable airmass northward. Shower and scattered thunderstorm activity is expected to develop over North Dakota and move into southern MB by late Sunday into Sunday night. Some of the rain could be heavy at times with amounts of 15-25 mm possible over portions of southern MB by Monday morning, including parts of the Red River valley. This system will be slow moving and will continue to generate showers and scattered thunderstorms over the northern plains and southern MB Tuesday into Wednesday. Of concern will be rainfall over this period, as river levels remain high across southern MB. Since much of this rainfall will be convective in nature, it will be difficult to pinpoint which areas will receive the heaviest rain and how much at this point.. but stay tuned as this situation develops.
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There is talk in the news that in Brandon 900 homes could be evacuated. That's before the heavy rains.
ReplyDeleteRob, I need your explanation on this one!!
ReplyDeleteYesterday I was wathcing a newscast (wdaz) and they explained that we will be going into a split-jetstream configuration. One going to the north and south of us. Yet you talk about a powerful Low level jet getting cranked up tonight giving us convection.
That's makes sense since how they showed the Upper low getting stuck in this slack flow and acutally backtracking over us late week!
Low level jet??? Split jet pattern??? How are they related??
Storm Prediction Centre in Oklahoma has southern Manitoba at risk of severe thunderstorms tomorrow with 5% contours extending north of the border. They also have us in a slight risk (15%) on Tuesday with a warm front close to the border. Interesting.
ReplyDeleteBrandon has declared a state of Emergency. Sound like their situation is getting dire
ReplyDeleteGeez, the new forecast on TWN and EC are a slap in the face. Only a chance of showers over next few days apparently, down from big accumulations. Are we just gonna miss out on this storm in Winnipeg?
ReplyDeleteWow what a change in the forecast
ReplyDeleteDaniel..
ReplyDeleteThe low level jet would be associated with the storm system that is being supported by the slow moving upper low. You can have a stronger wind flow in the lower levels even if the upper winds are slack. In this case, the strong storm system developing in South Dakota is pushing up a strong southerly low level jet of 50 knots into the eastern Dakotas tonight, while the upper flow is a fairly weak 25 knots. That low level jet riding up over the warm front is what can support the development of elevated convection.
Thanks for the explanation!
ReplyDeleteOh....Looks like some thunderstorms starting to form in Southern Manitoba!
Winnipeg might get a good one in a few hours!!!
Latest model runs have backed off the heavy rain threat for the Red River valley somewhat, with a shift towards southwest MB, southeast SK and the interlake regions over the next few days. Looks like a couple of waves of convection firing up with this slow moving system...one tonight over North Dakota that will spill into southern MB (including southern RRV), and then another Tuesday that will move over SW MB into the Interlake regions Tuesday into Wednesday. Overall looks like less rain for RRV through Wednesday, but still a heavy rain threat for SW MB where they certainly don't need it.
ReplyDeleteOf course, all this will depend on where the convection fires up over the next day or two and models can have a hard time getting that right.. so keep an eye on North Dakota and southern MB radar to see where cells are developing to help assess rain potential for southern MB.
Winnipeg might be getting into the thunderstorm action sooner than I thought! A nice cluster right on our doorstep!
ReplyDeleteOf course a thunderstorm pops up right over the city.. I just fired up the BBQ!
ReplyDeleteLooks like the far west side of the city got the worst of that storm!
ReplyDeletewill there be any more tonight?
ReplyDeleteFinally some thunderstorms are starting to fire up stateside but looks like we won't see that!
ReplyDeleteSeems a steady rain might settle in overnight!
Tornado possibilities for SouthEast ND/MN Tuesday?
ReplyDelete35C in Topeka, KS today...the heat is just a day's drive south of Winnipeg...so close, yet so far.
ReplyDeleteYeah, I was noticing that 30C+ heat in KS, NE and Iowa.. even got to 28C in Mobridge SD.. near the ND border. Getting agonizingly close!
ReplyDeleteLooks like the next round of convection is firing up over nwrn ND.. that will spell bad news for SW MB and SE SK where convection will morph into large area of heavy rain tonight into Tuesday with 25-50 mm possible. Hopefully bulk of rain stays west of the Assiniboine valley for Brandon's sake, but the Souris river valley looks to be a concern.
Tomorrow should be interesting. We'll have to keep an eye on any convection firing off along surface trough in N Dakota out ahead of the mid level dry slot (clearing/instability in question but fairly good shear to play with). Narrow warm sector pinches out as it lifts northwards towards us by ealry evening. Forcing from LLJ doesn't look especially well organized but maybe enough to support band of showers/ left-over tstrms moving up from N Dakota between 7 and 10 pm. The core of that summer like heat and humidity shifts into S Minnesota tomorrow with temps in the low thirties and despoints in the low twenties..
ReplyDeleteRob, My parents live in Elie and they are concerned because they plan to send a lot of water into the La Salle watershed. They were told they too might have to evacuate!!
ReplyDeleteParents were told they might have to leave Elie by Wednesday! Might be 1 to 4 feet of water in town!!!
ReplyDeleteTough situation daniel.. hopefully the La Salle can take the overflow with minimal flooding. Hope your parents fare OK..
ReplyDeleteLuckily, not much rain overnight over SW MB with amounts of 5 mm or less since midnight.. good news for the Assiniboine watershed. Even SE SK only had 10-20 mm according to CWB Weatherbug network, so not nearly as heavy as models were indicating (25-50 mm+) Still more rain on the way today.. but its not looking as dire as models were suggesting (at one point, GEM was showing a 12 hr total of 100+ mm over Estevan for today!)
ReplyDeleteSome breaks in the cloud cover appearing over southern RRV and SE MB.. hopefully some of that drier air can work its way into Winnipeg and we see some sun! This weather's depressing.
ReplyDeleteI'm crossing my fingers and hoping the long range GFS and ECMWF are correct and we see some warmer and drier weather next week with temperatures in the mid 20s over southern MB.. along with some wind that will help dry things out. We need it!
Interesting setup today with main shortwave heading northwards through E. MT / W. ND towards the CDN border. One warm front is socked in with stratus, draped across N. ND with a second warm front further south lying from SE S.D. across S. MN. Mid-day sounding from XWI showing significant cap at 770mb w/temps @ +10C. Conceptually, quite good and matches airmass over NE/SD.
ReplyDeleteSo! Likely have good warm advection all the way from NE to S MB in warm conveyor belt. Somewhat dry in mid-levels, evidenced by copious ST throughout MB/ND. Strong lift associated with this system, however. This results in two main weather stories.
The first is convection supported by the shortwave as it heads north. Ample lightning evident in W ND near the Devil's Lake basin pushing northward towards SE SK. This will likely continue through the day and slowly mash out into a large area of rain as it approaches the deformation zone, which currently runs from Val Marie, SK towards Swan River, MB. Exact rainfall amounts will likely be less than models have been indicating (as they have been through this whole system), however local amounts close to 1" certainly are possible.
Second story will be for the RRV and east. Surface based convection, save for a miracle, isn't going to happen with such a strong cap. There will likely be convection firing off in S ND this afternoon, however, which will push northward and has plenty of support to ride up the warm fronts and become elevated. MUCAPES of ~ 1000 J/kg ride into the S RRV tonight and across SE MB which will likely provide continued support to thunderstorms as they move through the southern portions of the province.
I think Winnipeg will potentially see some showers with the chance of a strike later this evening, however the exact area of convective initiation will prove to be essential for forecasting the track of the convective system as there is strong directional shear through S MB with streamlines switch from south and wrapping around the shortwave to south and pulling off the the east over just a couple hundred kilometers.
It will be quite interesting to see how things develop this afternoon, and if you're lucky enough to see some sun this afternoon, enjoy it! It could even feel like a bonifide summer day in the sunshine :)
Nice write-up, TBS.
ReplyDeleteInteresting to note that a small thunderstorm fired just south of Steinbach early this afternoon but quickly fizzled. Looks to have developed where a hole in the low level cloud deck developed.
I think we'll be talking a whole lot about the cap this storm season. Storm chasers/enthusiasts in the central and southern US plains have been pulling their hair out this spring. The cap has been very strong so far and is likely the reason for the dryline mixing so far east, at times, providing the southeast US with a few major outbreaks.
As Rob stated awhile back, our storm season is influenced heavily by soil moisture content and evapotranspiration. If this northward shift in the storm track can continue as we push forward, that would put us in a favorable spot for convection. Some of southern Manitoba's most significant severe weather events have happened with a ridge just to our south putting us on the northern periphery.
I'm starting to become convinced that we're going to be at or above average in terms of thunderstorms/severe weather in the coming months.
Convection is blossoming extremely nicely in SW MB/SE SK where the upper jet is feeding into the shortwave. Looks mainly like heavy rain, but it sure looks impressive.
ReplyDeleteThings are shaping up that this evening we may see quite a line of convection develop from NW ND ENE across SRN MB.
Looks like a thunderstorm has gone up north of the city and a second one near Falcon Lake. Lets see if more are to come... Both these thunderstorms fired up where there has been at least partly sunny skies for the last hour or so.
ReplyDeleteBy the way, the Falcon Lake storm produced golf ball sized hail.
ReplyDeleteyeah.. warnings out for those storms. Line of enhanced cumulus from Fargo curving SE to Redwood Falls MN.. that is the area to watch for more development which eventually would advect into S Manitoba. T/Tds of 28/19 as close to us as Fergus Falls MN..
ReplyDeleteLittle skeptical of that golf ball report. I'm a little curious what brand of golf balls they're used to...
ReplyDeleteThat being said, attention turns to W MN / C ND as surface based convection has begun in MN and elevated convection will likely develop along the same line through ND early this evening. This will advect nearly straight north into S MB.
Tornado warnings now being issued for Minneapolis! No surprise!
ReplyDeleteThey hit 31 C today with high dewpoints!!