Nov 23
NOAA WINTER OUTLOOK

THURSDAY, NOAA UPDATED ITS WINTER OUTLOOK:
NOAA's Climate Prediction Center (CPC) forecast for the upcoming winter months of December 2024 to February 2025. While there is a 57% chance that a weak La Niña will develop and impact the weather across much of the United States, its impacts in the Upper Mississippi River Valley can be highly variable with both temperatures and precipitation.
Temperatures: Equal chances for either warmer- (warmest third), near-normal, or colder-than-normal (coldest third) across the Upper Mississippi River Valley.
Why equal chances?  Mixed Temperature Signals with no strong tendency either way.
Precipitation: Near to wetter than-normal is favored (33-40%) across the Upper Mississippi River Valley and Great Lakes. This does not necessarily imply that this winter will end up being snowier than normal but tends to increase chances. 
Locally, wetter-than-normal (not just a hundredth of an inch wetter than normal, but among the wettest third of the winters from 1991-2020) is slightly favored (33-40%) across our part of the Upper Mississippi River Valley. This forecast was based on trends with La Niña since the early 1990s and over the past 15 winters.
La Niña Trends
Since the early 1990s, La Niña (weak, moderate, & strong) impacts on local winter precipitation have changed. We have been seeing more wetter La Niña winters and less drier La Niña winters. From 1949-1990 (12 total), 6 were among the driest third, 3 were among wettest third, & 3 were near normal. Since 1991 (13 events), 6 were among the wettest third, 4 were near normal, & 3 were among the driest third.

Besides La Niña, this winter will also be affected by:
Arctic Oscillation (AO) and North Atlantic Oscillation (NAO) - These oscillations can influence the number of Arctic air masses that penetrate into the Southern United States and nor'easters on the East Coast.
Eastern Pacific Oscillation (EPO) - This can affect the location of where the cold air masses will be located in the northern United States
Madden-Julian Oscillation (MJO) - This can affect both temperatures and precipitation in the weekly time scale.


A number of sources are used to make the outlook, but one of the more influential models is the IRI Multi-Model Probability Forecast. This is what it indicated for winter temperatures-largely what the outlook depicts.
The CFSv2, a U.S. based climate model which is weighted heavily, shows this for winter in its latest run Friday.
The CFSv2 precipitation outlook shows much of my region with near to slightly below normal amounts. If the temperature pattern is correct, much of what falls could be snow. 
Honestly, it's very difficult to make an accurate forecast for a 3-month period. Small shifts in storm tracks and jet streams can make large differences. I summarized my winter outlook issued October 18th this way....

My conclusion is that there is quite a bit of doubt regarding the evolution of winter. I think we end up colder than normal (but not drastically), with near average snowfall despite lower than normal precipitation. I expect one or two nasty cold snaps and 2-3 significant snowstorms. Furthermore, I would not be surprised to see several clipper like events with 1-3 inch type snows that are followed by wind and cold. As usual, I anticipate a January thaw that will be a welcome break for several days. If things go well, we may get a couple more mild periods deeper into February.

For what it's worth, that is where my mind is now. That said, with all the extreme weather we've witnessed recently, I'm ready for about anything, including the kitchen sink. You should be too!

I will also add that my outlook from 5 weeks ago was heavily weighted on a mean jet stream pattern that looks like this December though February.
That look, tied to NW flow around a west coast ridge, has become more pronounced the past week, indicating a shift in that direction. In fact, the GFS shows this for the 500mb storm track December 8th. A spitting image of the classic La Niña winter above, if I do say so myself!

EXPLORE OUR NEW WEBSITE & HOLIDAY DEALS AT OUR GALENA AIRBNB
Santa's secret destination to relax after his big night!

A SHORT TERM PERSPECTIVE
I'm not going to spend much time on the weekend, as the sensible weather is storm free and uneventful. Highs will be chilly Saturday and with minimal sunshine should be confined to the low to mid 40s. Sunday, we get a good bump with a burst of warm advection that should pop highs into the low to mid 50s, perhaps close to 60 in the far south. 

That little party ends Monday with a low pressure wave that passes just to the southeast. A few showers are possible, but the best forcing remains to the north, limiting coverage to scattered and amounts to little if any. The north stands the best chance of seeing any damp weather, with temperatures returning to the 40s by late day. 

Colder weather takes control the remainder of the week, with highs mainly in the 30s. Thanksgiving eve, the EURO brings a weak disturbance that could kick up some snow showers. Amounts are greatest in the north, where an inch or two is shown. That's if the EURO even verifies, the GFS has nothing at all. This is a low confidence scenario at this time. Here's what the EURO currently indicates for snow Wednesday night.
Following Thanksgiving, even colder air enters the picture for Black Friday, the weekend, and the start of December. Phasing today is less than indicated yesterday, which keeps the cold but decreases the chances of any significant snow producing system. However, the leading edge of the cold could easily set off a brief period of snow showers capable of producing minor accumulations up to an inch Saturday night.

Next Monday the EURO shows a brief but intense blast of cold with lows December 2nd around zero in the north with single digits elsewhere.
Wind chills Monday morning are impactful if the EURO is on track in the range of 15 to 20 below. Hopefully the EURO backs off on that idea in later runs.
Models have been flipping around significantly in recent runs, so confidence is at best moderate on precipitation  trough Thanksgiving weekend, but still remains high on the coming shot of cold air after Turkey day. 

That is all for now. Carry on and have a stellar weekend. Roll weather...TS