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.

10 comments:

  1. Those conditions can hold off until October as far as I am concerned lol... especially if we are dealing with another cold, drawn-out, La Nina type winter and late spring.

    Yesterday was quite a let-down in terms of convection. LLJ weakened and re-focused off to our east (what a surprise) over Minnesota/ NW Ontario - brushing the Whiteshell/ Bissett regions. Meanwhile the activity associated with the surface trough (that was moving in from the western RRV) weakened as it hit the cold pool from the N Dakota elevated convection. A 'perfect storm' of wrong ingridients resluting in just light rain/ drizzle again for the city.

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  3. Right now, if one believes models like NAM and GFS.. I see almost no severe potential and even little heavy rain threat for us.

    Here is a familiar story... LLJ cranks up over the Northern High Plains of the western Dakotas tonite only to jump across and (of course) stall out over NW Minnesota and NW Ontario tomorrow evening. That puts in position to see a lot of debris cloud. Best warm advection/ instability/ etc, etc all look to remain south of the border.. yet again.

    Under this scenario one would expect an MCS affect N Dakota somewhere between the US highway 2 and I-94 corridors tomorrow morning - depending on northern extent of cap (elevated mixed layer). I would then look for surface based storms to break out in the vicinity of the triple point down in N Dakota and evolve into an MCS/ heavy rain threat across NW and WC central Minnesota brushing SE Manitoba. Hopefully things will set up a bit further north...

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  4. I am now permanently suspicious of any nocturnal thunderstorms making their way out of ND this year.

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  5. Storms are really starting to fire up now along the Manitoba/ Saskatchewan border!!!

    There still is some hope of getting a storm tonight for the Red River Valley!!!

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  6. Not likely...

    Those storms are forming along an inverted trough and are diurnally driven. LLJ and main moisture transport will target Central Minnesota tonite - so with the loss of daytime heating and only marginal shear - expect those storms to weaken before they reach us. The inverted trough is progged to come thru at 7 AM so it should be a quiet frontal passage. However, we may have to watch secondary cold front that moves thru sometime late tomorrow... ushering in that pattern change to fall like weather.

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  7. That is quite the supercell that is hugging the international border in North Dakota!!!

    Tornado warned!!! Have to keep an eye out to see if it crosses into Manitoba!!

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  8. Two MCSs over the upper midwest..one in N Dakota and one in Minnesota. The latter is occurring on the nose of 850 hPa jet while the former appears to be associated with elevated moisture transport (at 700 hPa) and a region of midlevel frontogenesis. Very deep moisture down there with 700 hPa dewpoints as high as 9 C.

    Locally.. convection continues along inverted trough and is being supported by just enough southerly 850 hPa flow poking up from the Dakotas to keep a few lines of convection going.

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  9. Convection over N Dakota evolving into well defined MCV (mesoscale convective vortex) and continues lifting NE...

    Meanwhile shear and weak LLJ appear sufficient to cause line of convection off to our west to continue consolidating. Hard to say when it will weaken.. we'll find out tomorrow morning ;)

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  10. Well.. it had to come sooner or later.. but wow, what a deluge this morning. I picked up 40 mm of rain between 5:40 and 6:30 am, with 33 mm of that falling in the first 20 minutes. Max rainfall rate of 209 mm/hr at 5:52 am. Tremendous rainfall rates will likely result in flooded underpasses and basements this morning..

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