NOAA releases winter outlook

NOAA has just released their official winter outlook for the US. Their forecast calls for generally above normal temperatures over the US south and southeast and generally wetter than normal conditions over the Ohio Valley and Pacific Northwest. This is in response to the developing La Nina which would tend to produce below normal heights (trough) off the West Coast and above normal heights (ridge) over the southeast US with a storm track riding from the US west coast into the Great Lakes.

For the northern Plains/southern Prairies.. there is essentially an equal chance of either below/near or above normal conditions this winter.. i.e. a non-forecast. In other words, there is no clear signal how this year's La Nina will affect the southern Prairies one way or the other. If indeed the general synoptic pattern sets up as described above, then there would be a greater likelihood of below normal temperatures this winter over the Prairies, especially the western Pariries, with perhaps above normal snowfall over the eastern Prairies closer to the storm track.

Here in Winnipeg, our last extended La Nina occurred from mid 1998 to early 2001. During those winters,

1998-99… generally warmer than normal.. especially February and March.
1999-2000.. Generally much above normal..with near normal January. (snowcover was gone here by end of February)
2000-01... A real see-saw winter. Third coldest December on record, followed by a mild January then cold February
2001-02.. Generally warmer than normal, cold March

So as you can see, La Nina doesn't necessarily equate to a cold winter here, at least in the eastern Prairies. One also has to consider the remarkably low Arctic sea ice cover recorded this year (an all time low), which presumably would tend to delay the onset of deep and persistent Arctic airmasses in the far north. That could mean a delayed start to winter over the Prairies, before colder than normal conditions set up for the latter half of the winter, mainly over the western Prairies. If that storm track is further north, then Alberta could see a snowier than normal winter with storms off the Pacific, with above normal temperatures more likely over the eastern Prairies.

A TV meteorologist in the US has produced an analog map showing temperature/precip anomalies based on previous La Nina years back to 1950. It supports above normal temperatures in the southeast US, and colder than normal temperatures over the north/northwest US including the southern Prairies.

So there are hints that perhaps we'll see colder than normal conditions at some point this winter, but there are also conflicting signals that reduce confidence in this outlook, especially in light of warming trends in our winters over the past decade and this year's record low Arctic ice cover.

NOAA will update their winter outlook on October 18th and Nov 15th.

Where's the sun?

It's been a dreary few days over Winnipeg and Southern MB with generally overcast skies and cool conditions, as well as that washout of a Thanksgiving Monday. Our last sunny day was last Thursday (Oct 4th) which helped boost temperatures to 18C. Since then, afternoon temperatures have generally been stuck between 5 and 10c under overcast skies. Here in Winnipeg we had some brief sunny breaks Sunday morning (7th) otherwise, it's been overcast since last Friday. But that isn't unusual for this time of year as cool air begins flooding over the Prairies with still relatively warm ground and open lakes providing low level moisture. As a result, quite often you can get several days of cool cloudy weather during these months even in high pressure ridges (known as "dirty" highs in these cases) We're in such a period right now, and it looks like we'll stay cloudy through Friday before we get a better chance of some sunshine this weekend.

Significant rain possible over SE MB Monday

A new storm system developing over Minnesota will track into Northwest Ontario Monday and intensify. Significant rain is expected to develop on the northwest wide of this storm system, affecting much of southeast MB and the Red River valley Monday including Winnipeg. 20 to 30 mm of rain is possible over southeast MB with little or no rain expected west of the Red River valley. In addition, it will be quite cool as northwest winds tap some colder air aloft, bringing temperatures down to the 5c mark by afternoon. A good day to stay inside and enjoy some Thanksgiving leftovers!

Thanksgiving weekend outlook

A slow moving complex area of low pressure developing over the central American Plains will give a mixed bag of weather over southern MB this holiday weekend. Models have been struggling to find a consistent solution with this upcoming system, which explains the large swings and flip flops in the forecast this weekend. Initially it appeared as if this system would bring a prolonged period of rain over southern MB through the weekend. It now looks like much of the rain will fall over southern SK and southwest MB Friday into Saturday before moving into the rest of southern MB Saturday night into Sunday. At this point, the bulk of the weekend rain is expected through southwestern MB and the interlake (perhaps 20 -30 mm), with lesser amounts expected over the Red River valley and southeast MB (5-15 mm)

Saturday looks interesting as the storm system sharpens over the US midwest sending a pronounced warm frontal tough towards southern MB. This warm front will mark the leading edge of much warmer air which will be surging north into North Dakota and Minnesota on Saturday. The front may push into extreme southeast MB on Saturday with 25C temperatures possible along the US border. At this point, it appears Winnipeg will stay on the cool side of this front with temperatures in the mid teens. However if the front pushes far enough north Saturday afternoon, Winnipeg may get into the low 20s (as current forecasts suggest) The frontal trough will move east Saturday night into Sunday with showers and possible thunderstorms over southern MB with locally heavy rain possible. Another system threatens showers for Monday.

Summing up.. unsettled Saturday with showers over southwest MB and the interlake - drier with a warming trend over southeast MB. Showers and thunderstorms Saturday night with locally heavy rain possible. Showers ending Sunday. A few showers possible Monday. Have a good long weekend whatever the weather!

Rob's Obs humidity/dew point values

I installed a new temperature and humidity sensor on my Davis weather station today.. hopefully that will give more reliable humidity and dew point values now. So far values look good, but I will continue to monitor over the next few days to make sure readings are reliable.