The NWS released their latest forecast for December and it is calling for very strong odds of a warmer-than-average December for Illinois and a large portion of the United States. They put the chances at 70 percent or higher in northern Illinois and the Great Lakes region. The odds are between 60 and 70 percent for the rest of Illinois. Those are about the strongest odds that I have ever seen in a monthly forecast.
This forecast for December is strongly supported by the various forecasts out to 14 days, which are also calling for very strong chances of above-average temperatures.
The precipitation forecast is not as striking – increased odds of wetter-than-average conditions in the south and along the East Coast. That’s a classic El Niño precipitation pattern in winter months for those regions.
The winter storm over the weekend left a narrow swath of significant snowfall across the central Midwest. The heaviest amounts of 5 or more inches (blue) extended from the High Plains through Iowa, northern Illinois, southern Wisconsin, northern Indiana, and Michigan.
Here is a close-up of Illinois. The largest amounts are along the Illinois-Wisconsin border. Amounts of 5 inches or more (blue) were common across the northern third of the state. The largest snowfall totals in Illinois was 17.1 inches at Roscoe (Winnebago Co.) followed closely by 16.9 inches in Mundelein (Lake Co.). It was the second largest November snowfall for both Chicago (11.2 inches) and Rockford (8.8 inches). See graphics below created by NWS Chicago.
Snowfall amounts tapered off southward, decreasing rapidly from 5 to 1 inches (green), and south of Interstate 70 was essentially snow-free.
Today the NWS Climate Prediction Center released their forecast for December, winter, and spring. Of course, the strong El Niño in the Pacific Ocean is the dominant player in the forecast. It is expected to remain strong this winter, before transitioning to neutral conditions in late spring/early summer.
In general, over the next six months Illinois will have an increased chance of being warmer than average, while parts of Illinois will have an increased chance of being drier than average. The strongest effects of El Niño will likely be felt in northern states (warmer and drier than average), and in the Southwest and Southeast US (cooler and wetter than average).
For December, Illinois has an increased chance of being warmer than average. There is no increased risk of being wetter or drier in December.
For winter, Illinois has an increased chance of being warmer than average. The eastern half of Illinois has an increased chance of being drier than average. The western half of Illinois has no increased chance of being wetter or drier than average.
For spring, the northern half of Illinois has an increased chance of being warmer than average. The southern half has no additional chance of being warmer or cooler than average. Parts of eastern and northern Illinois have an increased chance of being drier than average. The rest of the state has no increased chance of being wetter or drier than average.
A large, slow-moving low-pressure system passed through the central US this week, bringing widespread rains from Louisiana all the way up the Mississippi River Valley. Areas in yellow and beige received 2 to 4 inches of rain, including large parts of Illinois. Some counties along the Illinois-Indiana border received amounts in the 1 to 2 inch range. Meanwhile, areas in Missouri and Arkansas received 5 to 8 inches.
The largest amount reported in Illinois in the last three days was 3.95 inches in White Hall, IL. White Hall is in Greene County and where my great-grandparents lived.
Here are the rainfall departures for November so far. Areas in green are between half an inch and two inches above average. Areas in blue are two to four inches above average. This should pretty much erase any concerns about dry conditions earlier this fall.
By the way, these maps came from a NWS product at http://water.weather.gov/precip/
I have noticed that the average date of the first snow is a popular search term on the blog, so here is the reposting of the median dates of the first measurable snowfall of the season in Illinois. This map is based on 1971-2000 data. While it is not based on the current 1981-2010 averages, the map is still relevant for the purpose of getting an idea of the dates. Measurable snowfall means at least a tenth of an inch.
In the northern third of Illinois, the first snowfall occurred around Thanksgiving. The dates switch from November to December once you reach central Illinois (just north of a line between Quincy and Champaign). By the time you reach Carbondale, the date can be as late as December 20. From this you can see that we are by no means behind schedule this year.
While we have one of the strongest El Niño events occurring in the Pacific Ocean basin right now, the effect on November temperatures is typically quite chilly. Looking at the past 5 strong El Niño events since 1950, November was colder-than-average in three events (1972, 1982, and 1997), average in one event (1957), and warmer-than average in one event (1965).
Here is how this year stacks up to the monthly temperature departures from the 1982-83 and 1997-98 events. As you can see (circled), November 1982 was slightly below average (-0.4 degrees) while November 1997 was well below average (-3.9 degrees). This November so far is 5.9 degrees above average.
In the last two big events, the above-average temperatures did not appear until December, January, and February. So what does it mean if this November is unlike 1982 and 1997? It just means that no two El Niño events behave in exactly the same way.
The rain has finally moved into Illinois this morning. According to the National Weather Service, widespread heavy rain is expected to continue in Illinois over the next 3 days. Here is the forecast map for Tuesday morning showing a large storm moving across the central US. Rain is likely from the Gulf of Mexico all the way up to the western Great Lakes. Snow is likely in the Plains states (areas in blue). However, we will likely be too warm in Illinois to see snowfall.
One of the impacts of the warmer-than-average weather in October and November is that soil temperatures have been slow to fall below 50 degrees . This is the important temperature threshold for those applying fall fertilizer (55 degrees with an inhibitor).
As of this writing (November 13), yesterday’s daily high soil temperatures at 4 inches were still ranging from 49 degrees in the north to 58 degrees in the south. Naturally, the air temperatures are going to have to get into the 40s and stay there for these soil temperatures to continue to drop. However, the NWS forecast for the coming week shows highs in the mid to upper 50s in the north and in the low 60s in the south.
The USDA-funded Useful to Usable (U2U) project has released their split Nitrogen application decision tool for corn across the Corn Belt. The Corn Split N tool combines historical weather and fieldwork data with economic considerations to determine the feasibility and profitability of completing a second (split) N application within a user-specified time period. Check it out at www.agclimate4u.org under the “decision support tools”.
Screen shot with default values for Champaign County, Illinois
November is starting out warm and dry for Illinois. The statewide average temperature is 6.1 degrees above average, while statewide precipitation is at 0.8 inches (75% of average).
The map below shows that precipitation is fairly widespread across the state. Meanwhile, lower precipitation totals prevailed in states to the west. Wetter conditions have occurred across southern Missouri and across the Ohio River Valley.
Here are how past Novembers have fared in terms of temperature and precipitation. No trends in precipitation; however, the 1980s and 1990s were wetter. There is a slight tendency towards warmer Novembers in the last 35 years. However, 2014 proved to be the exception with the 4th coldest November on record. Continue reading “November, Starting Warm and Dry in Illinois”