Keep in mind, just like any long range forecast; the further away you get from the forecast time the lower the confidence becomes and lower the accuracy will be. Generally we are decently confident within 10 days, any further and confidence drops unless we see a very strong signal. We will try to explain those details with each update if needed.
30 Day Outlook – September 2023
Our Forecast Thoughts and Discussion
In September this year, we are rolling into a strong El Nino… which typically means we see a warmer fall. In terms of precipitation, El Nino falls can be wetter, but that precipitation is more likely later in the fall rather than early. As such, I don’t see a ton of moisture coming our way for September this year… hopefully October will be a bit more promising.
We’ll take a look at all of that but here are a few of the short term highlights:
- Labor Day Weekend and the next couple of days after that period look warm and dry. Temperatures will likely be well above normal (typical average daily high for Denver this time of year is about 85 degrees)
- Models showing a lot of “high pressure” setups to the Southwest and South of Colorado for much of the month. This would favor hotter and dryer conditions for much of the month while that pattern is dominant. How hot and dry we stay will depend on how strong those high pressure systems build and where exactly they set up.
- There is uncertainty as we get towards the last part of the month. This could either be more of the same or we could see a pattern change – models are not helpful on this so we will just have to continue to monitor. Models do favor ridging (high pressure) again in early October so we may not see much change in late September. Time will tell!
Climate Prediction Center Outlooks
The Climate Prediction Center 30 day Outlooks show the likelyhood (probability) of precipitation to be above or below average and temperatures to be above or below average.
This causes some confusion… for example deeper shades of red on the temperature product do not mean hotter temperatures… they simply mean above average temperatures are more likely. Please take note of this when veiwing the information below.
Note: this is not our forecast, it is one of many tools we use when creating our own forecast… additional context is needed when viewing any single weather product.
If you have any questions, reach out!
Our Thoughts on the CPC Outlooks
The CPC Outlook for September favors a higher probability of dryer than average conditions for much of Colorado. The Eastern parts of the state have the higher probability here with the extreme Wester parts of the state retaining an “equal chances” designation – meaning it could be wetter or average or dryer than average. My thinking on this is twofold;
1. September is historically a dry month for Colorado so it doesn’t take much precip to boost us above average.
2. Depending on where the high pressure is setting up, it’s not inconceivable that we see monsoon-like moisture spin around the edge of the high pressure and give the mountains and Western slope better chances for rain and thunderstorms.
In terms of temperature, there’s a fair amount of confidence that September 2023 will be warmer than average. August 2023 ended up above average and given what I’m seeing for September – it looks likely that similar pattern will remain well into the month. Againt, the Eastern part of Colorado is favored to end up above average, more than the West.
Our Forecast and Additional Discussion
El Nino will be strong this fall and going into Winter. We are already seeing its effects on much of the Southern and Western U.S. and will continue to for a while.
El Nino events favor a warmer and wetter fall in Colorado, but no two events are a like. We can take that into account when forecasting for a month or a season during an El Nino event, but there is still a lot of variability.
That being said, this summer was record breaking for many areas mainly due to the strong high pressure over the Southern part of the country. I see a lot of evidence in the models that weather pattern will continue for a while. That would favor warmer conditions for Colorado.
Precipitation is less certain, but it doesn’t look likely we see a ton of those chances in September, so I’m leaning towards a dry September. September is historically dry anyways, so one storm system could blow that apart, but we will see.
Drought Status and Updates
As of September 1, 2023 Colorado’s drought designations are mainly limited to the Southwestern corner of the state. Largest areas are Abnormally Dry and Moderate drought with a pocket of Severe Drought in Alamosa and the surrounding valley. This area has been expanding over recent weeks. Additionaly, Eastern Colorado has seen hot and dry conditions, with little rainfall and hot temperatures – we will be watching for any drought designations over the coming weeks.
We will continue monitoring this
Current Month’s Forecast
September 2023 (Palmer Divide Region)
- Temperatures: Above average
- Precipitation: Near average to slightly below average
Previous Months (2023)
August 2023 (Palmer Divide Region)
- Temperatures: Slightly above average -Finished slightly above average-
- Precipitation: Slightly below average -Finished slightly below average-
July 2023 (Palmer Divide Region)
- Temperatures: Near average -Finished slightly below average-
- Precipitation: Near average to slightly below average – Finished above average-
June 2023 (Palmer Divide Region)
- Temperatures: Near to below average -Finished below average-
- Precipitation: Above average – Finished above average-
May 2023 (Palmer Divide Region)
- Temperatures: Near to below average -Finished below average-
- Precipitation: Above average -Finished above average-
March 2023 (Palmer Divide Region)
- Temperatures: Near to below average (slight bias towards below average, especially first half of the month)
- Precipitation: Near average (March is typically a wetter month, expect overall precip to finish near average with a slight bias towards above average)
Previous Months (2022)
December 2022 (Palmer Divide Region)
- Temperatures: Near average -Finished near average-
- Precipitation: Near to below average (Eastern Colorado) Near to above average (Colorado Mountains) -Finished below average in E Colorado-
October 2022 (Palmer Divide Region)
- Temperatures: Near average to slightly above average -Finished near to above average-
- Precipitation: Near average -Finished below average-
June 2022 (Palmer Divide Region)
- Temperatures: Near average to slightly above average -Finished above average-
- Precipitation: Near average, possible slightly below average -Finished below average-
May 2022 (Palmer Divide Region)
- Temperatures: Average to slightly above average -Finished near average-
- Precipitation: below average overall -Finished near average-
April 2022 (Palmer Divide Region)
- Temperatures: Average to slightly above average -Finished near average-
- Precipitation: near average to slightly below average -Finished well below average-