Rainy Day on Tap for Winnipeg

Winnipeg will see a few showers this morning develop into a rainy afternoon before it all turns to wet snow this evening as the first “summer-y” system of the year pushes through Southern Manitoba.


Hand-analysis of the 925mb Height/Thermal Field for 12Z March 20

A very summer-y low is passing through North Dakota this morning, with a warm front draped west-to-east across much of the state, just south of the international border, before it dives south through Iowa. This system has brought with it copious amounts of warm air and is the first real summer-like system of the year.

East of the warm front, in Iowa, a complex of thunderstorms are moving across the state, supported by a 60 kt 850mb jet riding over the surface warm front, bringing with it moist air with Θw values near 20°C. This 60 kt LLJ then arcs north and pushes into Northwestern Ontario. As can be seen by the red shading in the analysis I have done this morning, warmer air is being pushed up through much of Southern Manitoba, including the RRV, Interlake and Parkland regions of west-central Manitoba. With the surface warm front just south of the border and plenty of warm air overrunning it, this has brought a mix of precipitation for areas in Southwestern Manitoba across the Trans-Canada highway into the Whiteshell and north.


1.5km CAPPI Radar Reflectivities

Pilot Mound, Morden, Steinbach and Sprague should escape most of the precipitation until later today. Being so close to the warm front, the precipitation is actually developing north of them where the air aloft that is being lifted is saturating. For those areas, expect a cloudy day with drizzle likely and if the wind manages to calm a bit (say to 15 km/h or less) fog patches are certainly possible. By later this afternoon, rain should move into the area, though with accumulations of about 5mm. For Portage la Prairie, Winnipeg, Dugald, Selkirk/Gimli and the Whiteshell, showers seen this morning will continue to develop and intensify to an area of rain by this afternoon. Expect to see about 5-10mm of rain before switching over to wet snow this evening. Do not be surprised to see a few snowflakes today, though; as it is quite likely for there to be embedded convection in the rain bands, areas of heavier precipitation may be able to produce rain mixed with snow as the shallow warm pool is unable to completely melt all the precipitation.


12Z 20 March 2011 GEM-REG 12h QPF Accumulation valid 00Z March 21 2011

Further west, over the higher terrain, the precipitation will predominantly be snow. Dauphin/St. Rose/Minnedosa are under a heavy snowfall warning as 10-15cm of snow are expected by this evening. Fortunately, as this weather system is driven primarily by warm air, the precipitation should end quite quickly as the low pulls out of our area this evening.

All in all, it’s quite a good day to stay inside with a hot drink and read a book. A little bit of everything will be seen through the afternoon, and unless you’re a big fan of having a new “Rally Inspired” paint job on your car, it’s best to stay off the messy, messy roads.

The next significant weather system will pass through on Tuesday, and this system will receive plenty of attention as it develops as it has the potential to produce significant amounts of snow/rain, and could add uncomfortable amounts of water into the Assiniboine/Red River drainage basins. I’ll post some more information about that system on Monday when things are a little clearer.

The Upcoming Week

Sunshine and warm temperatures are the name of the game this week.

There’s not much to say for this week other than enjoy the nice weather.  A broad upper ridge will dominate the weather over the southern Prairies through most of the week.


12Z GEM-REG 500mb Heights & Speed valid 12Z Wednesday Oct 6.

A broad upper ridge sitting over the southern Prairies is bringing temperatures into the low to mid 20’s over Southern Saskatchewan and temperatures near 20 for Southern Manitoba.  This upper ridge will give way to a weak upper trough that will move across the Prairies Tuesday and Wednesday, however any rain associated with it will stay well north of the RRV and not effect our temperatures too much with them being limited only to the high teens.  After the trough moves by, then the upper ridge begins to build back and temperatures should head back into the low 20’s for the week’s end.

A warm and dry outlook is sure to be welcome news for farmers who have been battling waterlogged fields through much of the summer.

A Couple Unsettled Days, Then Warmer Weather Returns

As we quickly approach the beginning of fall, Winnipeggers can be happy to know that after the next couple days, the mitts can go back into the closet.

So what’s on tap?  For this evening, most of the RRV should see heavy drizzle or light rain as a trough line moves through that connects two low pressure systems: one in central Saskatchewan and one in South Dakota.  The precipitation will move out overnight and tomorrow will bring mainly cloudy conditions with scattered drizzle and moderate northwest winds.  Showers or drizzle may make an appearance downwind of the lakes, but nothing widespread is expected.

On Wednesday afternoon into the overnight period, areas close to the International border may see some showers spread north from a system moving through the Dakotas, however it seems to me that the models are underestimating the effect of the ridge that will be positioned across the central Prairies.  It’s likely that the dry outflow from the ridge will keep things cloudy instead of rainy over southern areas of the RRV.

The rest of the week looks quite nice with sunny skies through much of the RRV and temperatures climbing into the high teens.  There’s definitely a chance that Winnipeg will see temperatures over 20°C, however I’d currently bet on just high teens as the models tend to over-amplify upper ridges in 60+ hour forecasts.  A string of disturbances will trek across the Dakotas, and there is a slight chance that some precipitation will nudge into areas near the international border, but for the most part, expect the second half of the week to be warm and dry.

As one other note, it looks that from here out, overnight lows look to be in the 5-10°C range, which is good news for farmers in the RRV, many of whom were able to escape the frost which affected Winnipeg and areas north and west on Saturday night.  Drier, frost-free conditions are sure to be good news for many of the province’s farmers.