Category: Forecasts

Potentially Record-Breaking Warmth on the Way!

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Warmer weather is on the way for Winnipeg this week as another surge of mild pacific air crosses the Prairies. Temperatures will push well past 0°C on Thursday, with several record highs at risk of being broken across Southern Manitoba.

00Z Fri. SFC Temperature from GEMGLB

Surface Temperature plot valid for 00Z, Friday January 6th, 2012

Warm air will surge across the Prairies with a low pressure system that will track across the Central/Northern Prairies Wednesday/Thursday. Those of us in the Southern Prairies will get to enjoy a nice early-January day where temperatures will reach between 5°C and 10°C by Thursday afternoon with relatively light winds.

Temperatures should be restricted by the snow cover, and I’d like to see a solidly southwest wind to get daytime highs as high as currently forecast (+7°C for Winnipeg).

Thursday, January 5, 2012 18Z Wind Field from GEM-GLB

Surface Wind & MSLP for Thursday, January 05 valid at 18Z from the January 3rd, 2012 12Z run of the GEM-GLB.

Currently, winds are forecast to shift from southerly to westerly in the afternoon, however if the troughing ahead of the low is not as deep as currently forecast, southerly winds could prevail in the RRV and keep our temperature significantly lower. That being said, I’d be willing to pin the daytime high for Winnipeg to be about 6°C, reached late in the afternoon. This temperature is well above the -16°C it reached last year on January 5th, the -13.5°C on January 5th, 2010, and the -24°C it reached on January 5th 2009.

The average daytime high temperature for January in Winnipeg is -12.7°C, and the warmest temperature on record for any day in January in Winnipeg is 7.8°C, set on January 23, 1942. The current record high for January 5th is 4.3°C, set in 1984. We will definitely be well above our average daytime high on Thursday and most likely break the old daily record. Is it enough to break the all-time temperature record for January in Winnipeg? Let us know what you think in the comments!

Chance of Freezing Rain Over The Red River Valley

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A large upper trough swinging across the Prairies is supporting two low pressure systems, one in central Saskatchewan and one in the Northern Plains of the United States, that will move across Manitoba overnight and tomorrow morning, bringing with them snow and the risk of freezing rain.

Dec. 31 Prog

For southern Manitoba, the main concern will be the precipitation generated along the apex of the frontal wave as it occludes southeastwards from the northern low in Central Manitoba to Minnesota. The warm front will align somewhere near a line from Winnipeg to Sprague, and slowly shift south/southeast through the day. Areas near the International Border have the greatest risk of freezing rain, due to the higher intensity of the precipitation expected there. The risk diminishes as you head north towards Winnipeg. I agree with the latest Environment Canada forecast that calls for ice pellets in Winnipeg; the warmest air should stay south of the city and we will likely have enough cold air entrenched to freeze any rain that comes out of an above-freezing layer. I can’t exclude the chance of a brief period or two of freezing rain, especially late overnight and early tomorrow morning. As this system develops, snow will become the predominant weather type, and much of the RRV can expect between 2-4 cm of the white stuff, while a few localities may get up to a couple inches.

I think it’s likely areas south of Morris will see some duration of freezing rain before sitching over to snow. The good news is that this doesn’t have the makings for a large-scale freezing-rain event, so there shouldn’t be any concern of widespread highway closures. Given that some roads are already very slippery, however, drivers should take caution when travelling overnight or tomorrow as fresh snow may be hiding a layer of ice underneath. Always drive with care when freezing rain and snow occur.

This system should clear out tomorrow afternoon, bringing in strong northwesterly winds behind it gusting up to 70 km/h. Fortunately, the arctic cold front is well to our north, so while chilly, we likely won’t even seen our temperature drop to even -15 to -20°C for overnight lows before the next swell of warm air pushes across the Prairies, bringing us continued pleasant winter weather with daytime highs in the -5 to 0°C range! The strong winds will move in tomorrow evening and last through much of the day on Sunday before tapering off, bringing us wind chill values as low as -25 in Winnipeg.

So hang in there, a couple chilly days and we’ll be back to pleasant temperatures with a fresh coat of snow! Happy New Year!

What Happened to Our La Nina?

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What Happened to Our La Nina?

Earlier this year, the NWS issued their winter forecast that called for colder than normal temperatures and higher than normal precipitation. I expressed my doubts about the physical practicality of such a forecast.

Well, that forecast isn’t working out, and the NWS has issued quite a good little summary on what’s happening. It’s definitely more technical than a newspaper article, but it’s certainly not a research article or anything like that. If you’re interested in knowing why our winter has been how it is, this is a really good read!

I still stand by the original forecast not making much sense. As for the near-future, one of my best cold-weather predictors, Vladivostok, Russia, is still relatively warm (only -20°C), so a cold outbreak is probably a long ways off yet.

Handy forecasting trick: Most of the Prairie cold-outbreaks occur when a large ridge slides over the pole from Siberia and then down through Yukon (the Yukon? Any Yukon-ites able to enlighten me?) into the Prairies. When doing medium-term forecasts (8-15 days), I’ll often look at Vladivostok. If they’ve hit below -35°C, then within 6-12 days we’ll often get the cold weather here with daytime highs between -20°C and -25°C. If they get more towards -50°C, then within two weeks the Prairies will have widespread cold temperatures and extreme wind chills.

I still wonder why we bother with seasonal forecasts. Understanding how these oscillations all work is great, but our ability to accurately forecast them individually is often lacking, and we’re a long, long ways off from being able to resolve numerically how all these things interact together. If anything, this just shows how constant analysis and diagnosis of ongoing weather and climate patterns are the best method of forecasting.

Slight Chance of Showers Saturday Evening

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A system tracking across the Rockies into Alberta will slide quickly across the Prairies, brining increasing cloudiness to Winnipeg and the RRV Saturday afternoon with a slight chance of showers in the evening. For more info, read on!

GEM-REG 3HR. QPF
12Z 21 October GEM-REG 3 hour precipitation accumulation valid at 00Z Sunday (Saturday Evening)

Overnight a low pressure system will track across the Central Prairies towards Manitoba with a developing N-S trough intensifying as it moves eastwards. As it enters The Pas and Norway House areas on Saturday, Winnipeg and the RRV will see increasing clouds and a strengthening southerly wind to 30-40 km/h. As the trough swings through Winnipeg in the late afternoon and early evening, we’ll see a slight chance of a shower or two. The bulk of the precipitation should stay north of the city, closer to the low, where there is more significant lift. All models bring the edge of the rain close to Winnipeg, though, so it certainly isn’t out of the question for us to end up getting 2-4 mm out of an hour or two of rain. It seems most likely, though, that late afternoon and the evening will be overcast with a scattered shower or two.

After this system passes through, we’ll enter a stagnant pattern for a couple days with daytime highs just below 10°C and overnight lows slightly below 0°C.

Ensemble 500mb Theta-E
Ensemble Mean 500mb θe

The next chance for significant weather looks to be next Tuesday night / Wednesday morning as a rather sharp 500mb cold trough swings across the province. This will present us with a slight chance of flurries overnight, but shouldn’t amount to too much. More on that next week.

Have a great weekend and enjoy these crisp fall days!