Tag: Northwest Flow

The Deep Freeze Gives Way to A Mixed Weekend

Brad Leave a comment

While temperatures across the Red River Valley this morning are extremely cold, a developing series of major low pressure systems set to impact Alaska will be responsible for pushing us out of the deep freeze and back towards more seasonal temperatures for next week.

12hr. QPF valid Saturday at Noon

The GEM-REG is showing around 1–2cm of snow across the Red River Valley by midday on Saturday.

Friday


Sunny. Increasing cloud overnight.
-24°C / -28°C

Sunny skies will dominate the Red River Valley for most of the day today as we remain under the influence of the Arctic high. Entrenched in the cold air under this high, temperatures today will climb up to about –24°C; this is some 13°C below the “normal”[1] temperature for this time of year. The strong northwesterly flow aloft that’s brought our cold air back will begin to waver tonight as a weak disturbance ripples down the jet stream towards Southern Manitoba. An Alberta clipper will rush across the Prairies tonight, pushing clouds into Southern Manitoba through the overnight period and preventing our overnight lows from dropping to anywhere near where they bottomed out last night. Overnight lows will likely sit at around –27 or –28°C tonight through most of the Red River Valley.

Saturday

Saturday

About 2cm of light snow.
-16°C / -28°C

As the Alberta clipper pushes through on Saturday, a broad area of light snow will move through the Red River Valley. This system will be rather moisture-starved with only ¼ to ½” of precipitable water to it’s name, so snow will likely be light with SLRs of only around 15:1 (relatively crystalline snow). This will all combine to produce only 1–2cm of snow despite the fact that it will snow most of the day. Temperatures will warm up to around –15°C as a little bit of mild air pushes into the province with this system, but temperatures will plummet right back to where we were before as the clouds clear out fairly quickly on Saturday evening and we head to an overnight low of, again, around –28°C.

Sunday


Mix of sun & cloud. Chance of flurries.
-20°C / -28°C

Skies will start off sunny on Sunday but another weak system tracking across southwestern Manitoba will spread some cloud into the Red River Valley midday. This disturbance will track through fairly quickly so we’ll likely see a chance of flurries (with better chances over southwestern Red River Valley) late in the morning into the early afternoon. The clouds will clear out by evening as we head to another cold night with temperatures dropping back to about –28°C. Heading into next week, the flow aloft begins to become significantly more zonal, allowing milder Pacific air to push further eastwards across the Prairies. Temperatures will generally be warmer but by exactly how much is still hard to tell. Ensemble predictions have moved from an above-normal temperature forecast next week into a more seasonal-looking pattern. Either way, we’ll certainly be leaving the temperatures we’ve seen over the past week behind for a while.

  1. It should probably be said that the “normal” temperature for late January in Winnipeg is most likely just an average of the extremes.  ↩

A Rainy Weekend; Sunny Next Week?

Brad Leave a comment

Photo from Mike O’Flaherty to CJOB

Winnipeggers were woken by a severe thunderstorm on Friday morning around 5:40AM.  The storm ripped through Winnipeg leaving torrential rains in it’s wake.  Rob wrote an excellent summary of some of the damages that occurred in Winnipeg, including flooded underpasses, power outages, and explosive manhole covers.

Later that day, convection fired up through the RRV and brought another round of heavy rain.  Winnipeg had only heavy rainshowers that caused some localized flooding.  There was another tornado report out of Steinbach, however.  Looking through the damages, I’m highly doubtful that it’s a tornado.  While they’ve had more than their fair share of strong wind events this year, it’s a little ironic that we get more false tornado reports out of one of the only storm-ready communities than a lot of other places it seems.

Now moving on to this weekend’s weather for Winnipeg.

A large upper low positioned north of Winnipeg is bringing huge amounts of rain to the province.  A heavy rain warning exists for Grand Rapids right now, with Environment Canada expecting between 50-75mm of rain.  Through today, rain will wrap around the upper low and spread into the northern RRV by early afternoon.  The models are vary slightly in the exact positioning, but by this evening, areas in the RRV north of Morris can expect rain.  The upper low sinks to the SE overnight, drawing the wrap-around precipitation further south, and most communities within the RRV should expect a fairly rainy Sunday with unseasonably cool temperatures with daytime highs only in the mid-teens.

After this system clears out on Sunday night, the northern half of the RRV will see somewhere from 10-20mm of rain, while the southern half will see more along the lines of 5-10mm, perhaps as high as 15mm.  Following this system should be a relatively unremarkable week.  Cooler temperatures will be the name of the game, with daytime highs around 20 degrees.  The current forecast is for sunshine, however don’t expect completely clear skies as while we may be in a cooler airmass, we still have a strong August sun, which will likely produce lovely cumulus-filled afternoon skies.

One last thing to watch out for in the deceptive Environment Canada “a sunny week!” forecast is the fact that Winnipeg will be under a northwest flow for the duration of the week.  The weather has a sneaky habit of throwing little shortwaves down in a northwest flow that the model doesn’t pick up very well, and should any of these happen (as is even being hinted at for Monday evening), we could easily see another batch of showers and/or thunderstorms.

So instead of thinking this coming week will be a beautiful sunny week, wear thicker shirts, bring a jacket, and don’t be surprised if it ends up more unsettled than the forecasts are hinting at right now.