#upper trough

[aweathermoment]

Seasonable Weather with A Chance of Showers

Feeling chilly after the weather we've had lately, more seasonable weather has returned to Southern Manitoba with a slight chance of showers tonight across most areas of the RRV. [](https://img.skitch.com/20120905-ndaatwfmy7ted4bfydiupjixuc.png)

A GOES East multispectral satellite imagery from Tuesday evening showing the large captured low (denoted by the red L) anchored over Northern Manitoba.

A large upper trough is entrenched over Manitoba, bringing with it cooler air and clouds. Over the next several days, our temperatures will only climb to around the 20°C mark, right around the normal daytime high at this time of year of 21°C. For today, temperatures will climb to about 23°C before the sky clouds over as a weak cold front passes and our winds increase out of the northwest to about 20*km/h* with gusts to 40*km/h*. Clouds will clear out in the evening and we'll drop to a chilly low of 8°C. Skies will cloud up again on Thursday as we struggle to hit 20°C. Well have a slight chance of showers through Winnipeg and the Northern RRV through lunch and the early afternoon, however it won't amount to much if it does materialize. Temperatures will slowly climb at the end of the week into the weekend. Friday will see mainly sunny skies with a high of 21°C as we have one more day under the influence of the upper trough. As we move into the weekend, warm air pushes in once again, and we should see above-normal highs near 25°C under sunny skies.

[aweathermoment]

A Cooler Weather Regime

Cooler, more seasonable, weather is going to move into Southern Manitoba for the week ahead as a large upper trough swings into the region. [](https://img.skitch.com/20120903-bbgnmcen6334ycus6ah2ir2gif.png)

GEM-REG 500mb wind field valid Tuesday morning. A deep upper low is straddling the SK MB border with a trough extending to the SW denoted by the dashed black line.

A strong upper low sitting over the northern Prairies is in the process of stalling out over Northern Manitoba as it's been captured by a significant long-wave trough. While today will be quite pleasant with sunshine and daytime highs across the Red River Valley near 28°C, the aforementioned trough will be moving into our region tomorrow. With this system stalled out over the province, we'll be stuck under cooler air for the rest of the week; daytime highs will sit around the low-20's under a mix of sun and clouds or cloudy skies. Winds are expected to be fairly light through the week and overnight lows will sit around 10-13°C. While Northern Manitoba will be fairly wet this week, it looks like we'll be relatively dry in Southern Manitoba. The best chance for rain looks to be on Wednesday night into Thursday as a small reinforcing trough swings through the Red River Valley. Things then look to improve slightly over the weekend as an upper ridge starts to push across the Prairies, however another powerful low pressure system is forecast to move through Southern Manitoba and bring another batch of cooler air across the Prairies next week as it ushers in another cold trough.

[aweathermoment]

Rain Returns to the Red River Valley

While July has been a wonderful summer month (perhaps a little too wonderful at times), my lawn and my wallet are both ready for some cooler weather and some rain.  The cooler weather certainly has arrived; was anyone outside yesterday?  Even with the wind it was wonderful!  And, fortunately for my tomato plants, it looks like some rain is on the way as well.  Read on to find out the details!

16:15Z Daytime Multispectral Composite Satellite Image

The upper ridge that brought near-record Humidex values to Southern Manitoba earlier this week has finally moved off towards the east, which has allowed the upper trough situated along the B.C. Coast to begin moving inland.  As it migrates eastwards, it will spawn two low pressure centres: one over Central AB and a second one that will move through Montana and along the North Dakota/South Dakota border.  This will result in a rather complicated setup come Saturday morning with a surface low pressure system anchored to the upper low over Central AB with a secondary surface low pressure system anchored to a shortwave rounding the upper trough across the ND/SD border, with an elongated surface trough connecting the two.

GEM-REG Fri. July 22 12Z Model Run valid Sat. July 23 @ 12Z; 3hr. QPF + MSLP

In short, this setup will bring with it two bouts of precipitation.  The first will arrive through the morning hours on Saturday.  It's exact placement is still quite certain, as it will be produced by nocturnal convection along a 30kt southeasterly low-level jet.  As the evening progresses today, it will become quite a bit clearer as to where exactly the thunderstorms will track.  That being said, it's quite likely that areas near the international border will see 10-15mm of rain tomorrow morning with a few embedded thunderstorms as this system passes by.  Currently, it looks as if it's up in the air as to whether or not it will reach as far north as Winnipeg, however I suspect we'll see a sprinkle or two tomorrow morning.  I certainly won't dismiss the possibility of a good shower or thunderstorm here tomorrow morning with local amounts around an inch, though!

After that, the upper trough will begin to swing in during the afternoon, and that will bring with it a band of rain that will track through in the late afternoon and evening, bringing an additional 10-15mm to what has fallen already.

Total Accumulated Precip. from the 12Z GEMREG Fri. July 22 valid 12Z Sun. July 24 (Sunday Morning)

All in all, most of the RRV should see 0.75-1.25 inches of precipitation tomorrow distributed between two distinct rain events: relatively early in the morning and late in the afternoon.  Cloudy skies will likely dominate between the two events, limiting our daytime high to only about 20°C.

After this system clears out tomorrow evening, we should have a few nice sunny days with highs in the mid-twenties.  The next chance for rain looks like Tuesday evening, when a weak system moving through brings the slight chance of some late-day showers or thunderstorms.