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.