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Colorado Low Brings Major Rainfall to Southern Manitoba

May 6, 2015May 6, 2015 Brad Leave a comment

While Southern Manitoba has seen glancing blows from true Colorado Lows a few times over the past couple years, Winnipeg is in the middle of a multi-year drought with the last direct hit from a Colorado Low in memory occurring in November 2012.[1] Responsible for some of the biggest synoptic storms[2], Colorado Lows are a major weather system that often produce pretty much everything: thunderstorms, heavy rain, light showers, overcast & drizzly conditions, freezing rain, heavy snow and/or blizzard conditions.

Imagery of Developing Colorado Low — This satellite image from early this morning shows the developing Colorado Low over…Colorado. Who would have thunk?

Today will see the arrival of a Colorado Low that will dominate the weather over Manitoba for the coming few days. Southern Manitoba will escape most of the nasty weather associated with this system with just rain expected – albeit a fair amount – while Northern Manitoba gets slammed with heavy snow, freezing rain and strong winds.

Wednesday

24°C / 15°C

Increasing cloudiness then showers with the risk of a thunderstorm

Today will be a relatively pleasant day despite the imminent arrival of the Colorado Low. While today will start off with a little bit of sunshine, high cirrus will move in through the morning with thicker cloud arriving this afternoon. Winds will be out of the south to southeast at around 30–40km/h with some gustiness on top of that. Shower activity – with the risk of thunderstorms – will work its way northwards out of the Dakotas through the day into the Red River Valley. Temperatures will be quite mild with highs around the 23–24°C mark.

Heading into the evening, main band of showers associated with this system will spread across Southern Manitoba bringing rain with a slight chance of an embedded thundershower to the region. Rainfall amounts through the Red River Valley will likely be highly variable thanks to the convective nature of the precipitation; in general the “safe” guess at this point is somewhere in the 15–25mm range…or so. I don’t believe amounts will be much higher than that, but depending on a whole bunch of factors, amounts could end up in the 5–10mm range instead. Unfortunately, with such highly convective systems, these things are almost impossible to forecast until much closer to the event, so we’ll be providing updates in the comments below as well as on Twitter and Facebook. The showers will persist through the night as the temperature dips down to around 14 or 15°C.

Thursday

17°C / -2°C

Showers

Tomorrow will be a fairly wet day with more shower activity, potentially quite heavy at times, lasting much of the day before finally beginning to taper off in the evening. Our high temperature will only be around 17°C with some light southerly winds flipping to the northwest in the afternoon to around 40km/h. Rainfall amounts, again, could be quite variable thanks to the convective nature of things and exactly how the system matures.

RDPS Forecast Precipitation Accumulations by Thursday Evening — The RPDS weather model is bullish on convection and producing over 2″ of storm-total rainfall for the Red River Valley. This is likely too much.

There are really two possible outcomes:
1. General rainfall amounts near 10mm with convective amounts once again near 20–30mm in the Red River Valley. This would assume a general “rainy” area with embedded convective storms.
2. Very little rain as energy reconsolidates around a low developing in North Dakota and precipitation pushes off to our south and east.

I don’t think Plan #2 is particularly likely, but it should be noted. Again, we’ll provide updates heading forward below in the comments as this entire system becomes a more developed.

The gusty northwesterly winds will taper off in the evening as the precipitation moves out. Expect the temperature to drop to a very chilly –2°C.

Friday

8°C / -3°C

Mainly sunny and cool

Friday will be a pretty benign day marked by temperatures well below normal for this time of year as our high struggles to climb to 8°C with an Arctic ridge building into the region. Winds will be breezy out of the northwest at around 30km/h making for a chilly day all around.

Clear skies will continue on Friday night as the temperature dips to around –3°C.

I checked through our archives and chatted with a few other people, and that seems to be the general “last hit” agreement. Feel free to leave a comment if you can recall one more recently. ↩
Synoptic storms are large low pressure systems that impact across hundreds to thousands of kilometres, unlike convective storms which impact small areas. ↩

Hot Weather Continues

May 1, 2015May 1, 2015 Brad Leave a comment

The summer-like temperatures seen in Winnipeg over the past couple days will continue into the weekend with daytime highs 10°C above normal. A cold front will finally push through on Saturday evening, bringing an end to the exceptional warmth and ushering in a return to seasonal temperatures.

Today will be a gorgeous day in the Red River Valley with light winds and daytime highs near 25°C with a bit of a southwesterly wind. Expect a few clouds tonight with a low near 10°C.

Tomorrow will be a more interesting day as a more organized southerly flow develops over the Red River Valley ahead of an approaching low pressure system. Temperatures will climb to around 27°C while a meager amount of moisture pools through the Red River Valley ahead of an approaching trough. As the trough moves into the Red River Valley, it’s looking quite possible that we may see a few thunderstorms develop, however the chance is largely conditional.

Winnipeg Forecast Sounding for the afternoon of Saturday May 2, 2015 — This forecast sounding valid Saturday afternoon for Winnipeg from the NAM model shows a deep layer of instability, adequate moisture and favorable shear for thunderstorm development.

Given the fairly low amount of moisture available, cloud bases would likely be very high; the forecast sounding indicates cloud bases near 10,000ft which would mean the biggest threat from the storms would be strong wind gusts. Some hail might be a threat further south in North Dakota, perhaps sneaking onto extreme southeastern Manitoba, but overall it looks more like we’ll see a few weak thunderstorms develop capable of producing some fairly gusty winds. The overall environment, save for the lack of moisture, looks quite favorable for the development of the storms, though. Winds will generally be out of the south to southwest at around 30 gusting 50km/h with a slight chance for some 50 gusting 70km/h winds in the afternoon.

Some cloud will linger overnight as temperatures dip to around 9°C with winds relatively light out of the west to northwest.

Sunday will bring a bit of cloudiness and slightly cooler temperatures with a daytime high of “only” 19°C. Winds could be gusty out of the northwest for a few hours beginning in the morning before settling down to 30 gusting 50km/h for the afternoon. Sunday night looks mainly clear with a low near 5°C.

Summer Warmth Arrives

April 29, 2015April 28, 2015 Brad Leave a comment

Summer-like warmth has arrived for Winnipeg and the Red River Valley thanks to an upper-level ridge moving into the region that will spread warm air over Manitoba for the coming days. Some rain looks likely on Thursday evening as a “cool” front passes, but the other days through the second half of the week look beautiful with plenty of sun to go along with the warmer weather.

Today will be a mainly sunny day with a high near 21°C. Winds will remain fairly light through the day as well. With an overnight low near 8°C or so, the warmth should hang on into the evening making for a pleasant evening to be outside.

Thursday will bring a fair amount of cloud, however the sun will still poke out a few times through the day. Winds will be breezy out of the south, picking up to around 30–40km/h with gusts to 50–60km/h or so. Heading into the second half of the afternoon should really bring in the thicker cloud ahead of the approaching “cool” front. A band of showers will move in sometime between 6–9PM and last for a few hours as they move through.

RDSP 12hr. Precipitation Accumulation — The RDPS shows around 2mm of rain through much of southern Manitoba associated with the passage of a “cool” front on Thursday evening. Image above is total accumulations from Thursday evening at 7PM to Friday morning at 7AM.

Precipitation is expected to be fairly light, however, with total accumulations around 2mm, although if the odd convective cell gets going, some places may see closer to the 5mm mark. Winds will taper off with the passage of the front and temperatures will drop to around the 7°C mark with clearing skies overnight.

Friday will be another pleasant day with light winds, mainly sunny skies and a high near 21°C. Expect a low near 8°C on Friday night.

Pleasant Weather Returns

April 24, 2015April 23, 2015 Brad Leave a comment

Winnipeg will see a reprieve from the below-normal temperatures this weekend as the ridge of high pressure that’s brought the cooler weather shuffles off to the . In its place, a southerly flow will return warmer air to the region with temperatures climbing back to near the seasonal mark.

Over the next few days, no significant weather is expected in Winnipeg or the Red River Valley. Today will start off with some lingering cloud that will clear out through the day. Temperatures will climb to a high of around 13°C with a light southeasterly wind. Expect a low near 0°C under clear skies tonight.

Saturday will bring mainly sunny skies, light southeasterly winds and a high near 16°C. Saturday night will see a low near +2°C with a bit of cloud cover.

RDPS forecast Temperature for Friday Afternoon — The RPDS weather model is forecasting highs climbing above 15°C in Winnipeg on Saturday afternoon.

Sunday’s high will also be near 16°C, however with a few more clouds than Saturday. The temperature will drop to 7°C or so on Sunday night with increasing cloudiness overnight.

A Weather Moment

Author: Brad