WINTER 2022-23, PLUS RECORD WARMTH...
Before I get to the balmy weekend ahead, the official winter outlook from NOAA is out. The primary driver of this (and many other outlooks), is a weak to moderate La Nina. This will be the third consecutive year with a La Nina in that category of intensity. Uncommon but not unheard of. A traditional La Nina creates a mean storm track that looks like this. The ridge off the west coast directs the storm track into the Pacific Northwest where it digs into the Great Lakes and exits New England. That typically keeps the coldest air locked over the northern third of the U.S. The south remains mild and relatively dry. The wettest weather tends to be focused at the base of the trough in the Ohio Valley.
Some other factors come into play such as sea surface temperatures, high latitude blocking, and the phase of the MJO (Madden Julien Oscillation). In a nutshell, those features are often dictated by the La Nina over the course of the winter resulting in the pattern shown above. NOAA is leaning heavily on that and produces a temperature outlook that looks like this December-February.
The precipitation forecast is heavily based on a storm track like the one shown in the graphic above. That points to near to slightly above normal precipitation during the winter of 2022-23.
The idea from NOAA is that temperatures in the central Midwest will end a bit below normal with precipitation (including snowfall) near to slightly above normal. Below you can see the typical anomalies for snow, temperature, and precipitation in La Nina winters.
My take is that what NOAA is suggesting is a reasonable assessment. However, I think we may start drier in the first half of winter and then see an uptick in precipitation in the later half. I believe snowfall will end up in the range of 30 to 44 inches, heaviest in the north. Overall confidence is lower when it comes to rain and snow as it's impossible to define the precise storm track at this distance. Significant snow bands are usually not much more than 100-200 miles wide (sometimes significantly less). Where those ultimately decide to set-up will tell the tale of how much shoveling any given area will do.
Here you can see the snowfall departures in a weak La Nina compared to a strong one. Notice amounts are less in stronger events due to the strong westerly flow aloft limiting cold air intrusions. I am not expecting a strong event this winter.
Weak La Nina snowfall departures from average.
Strong La Nina snowfall departures
My experience also tells me that La Nina temperatures are often quite variable and there can big some very harsh periods (especially if we get a stratospheric warming event). On the other hand, there are occasions where the flow goes zonal for short periods of time allowing some brief but significant thaws. Temperature swings are common in a typical La Nina winter. I look for them. Based on what I've seen so far, I am also expecting winter to get off to a faster colder start this year in December than the previous two which were very mild! I thought that would be the case last year and was a month off in that assessment. Again, the stronger the La Nina, the warmer the winter. Here you can see the statistical anomalies point to a weak to moderate La Nina in the period December through February.
Overall, I certainly think the potential is there for a healthy winter, especially if we can get the MJO to cooperate and troll the colder phases of 1, 2, and 3 more often than not. The temperature analogs for those phases look like this January-March. If you want winter avoid 4, 5, and 6. I'll continue to refine my outlook over the next 2-3 weeks. As always, long range outlooks are fraught with peril and time will tell.
A REMARKABLE WEEKEND AHEAD...
The temperatures this weekend are going to be remarkable so I'm going to remark on them. Many places have already exceeded expectations with highs Friday reaching more than 80 in the SW half. I'm certain this was due to the extremely dry air with relative humidity values in some of my western counties down around 20 percent. It was even worse in western Iowa where a couple spots came in with RH as low as 10 percent. Most of you are aware that the drier the air is, the cooler it gets at night and the warmer it can heat up during the day. A perfect example of that was seen in Muscatine Friday where the low went from 32 to a high of 84. (Steve Gottshalk reported the same in Lowden) That 52 degree spread is the largest ever during October. The previous record was 48 degrees (43 to 91) in 2006.
In Cedar Rapids, the high reached 83 just 2 days after a low of 16 Wednesday. That's an incredible increase of 67 degrees!
If you liked Friday, there's no reason you won't love Saturday as highs again should go well over 80, perhaps as warm as 86 in a few spots in the SW half of my region. Records for the date are up there but it looks like with more dry air and deep mixing, most areas should have a shot. Cedar Rapids is the area least likely to get a record with the long standing mark there at 88 set in 1899. Moline has the best shot with the record at that location Saturday at 84.
As you can see, readings will be at least 20-25 degrees above the seasonal norms.
Sunday readings could cool a few degrees with some passing clouds. However, a stiff south wind should still give most areas a good shot at another 80 degree day. Overall I would say the general range should be from 80 north to 85 south. Just short of records if that holds. Both Saturday and Sunday look to be windy dry days with a high wild fire danger. No burning please!
SHOW ME SOME RAIN...
It's no secret how dry it is around the Midwest. Saturday will be the 8th consecutive day without rain here in Dubuque (the same for the rest of my region). Going back to August 29th, Dubuque has put together streaks of 12, 16, and now 8 days with no measurable rain. Over the past 55 days, only 0.86" has fallen. The rain deficit in Dubuque over that 55 day period is up to 5.15" Here are some of the rainfall departures since August 29th around the Midwest.
Seeing widespread dryness such as this, I'm happy to report raindrops are in our future. In fact, as early as Sunday night widely scattered showers and storms may dot the area as a disturbance swings by to the NW. These will be light and nothing more than a primer for the main event which commences Monday afternoon.
At that time a weak front will be stretched out across eastern Iowa with moisture pooling along it. Even with additional clouds, temperatures will still be mild with highs well into the 70s. Showers and a few thunderstorms will form on the boundary and could become enhanced by a southern stream wave that curls northeast into Illinois Tuesday night. Models remain inconsistent on the evolution of this energy. Either way the moisture and forcing should be there for a beneficial rain event. It could last into Wednesday if the stronger solutions track the system further NW. Needless to say there are details to work out but for now there is optimism we can more than settle the dust. Here's what models are currently suggesting for rain totals.
The EURO
The GFS
The national model blend
The Weather Prediction Center outlook
Personally, I would be thrilled with a record warm weekend and a nice rain early next week. Right now, that's what the cards are showing. Fingers crossed. Have a sensational Saturday everyone and roll weather...TS
