August - October Area Outlook
Area Climate Outlook for Late Summer/Early Fall
August – October 2008
1. August through October Climatology:
Overall average temperatures are close to the warmest of the year in early August, and then begin to fall during the mid to late part of the month. Much cooler temperatures return in September and October, with the arrival of Fall. Average low temperatures across the region east of the Wyoming mountains start off in the mid to upper 50’s in August, then fall into the mid 40’s for September, and into the mid 30’s for October. Average high temperatures over lower elevations tend to be in the mid to upper 80’s in August, then cool into mid to upper 70’s in September, with upper 50’s to mid 60’s in October. For locations like Laramie and Rawlins, average lows are in the mid 40’s to near 50 in August, then fall into the upper 30’s to lower 40’s in September, and reach the upper 20’s to lower 30’s in October. Average highs are in the upper 70’s to lower 80’s in August, then cool to around 70 degrees in September, and average in the upper 50’s in October. The average first freezes in Fall tend to occur in the mid to latter part of September.
Average total rainfall declines during this period, especially from about mid-August onward, as drier air masses become common over the region. Average rainfall east of the mountains ranges from about 1.25 to 1.75 inches in August, then drop off to about ¾ to 1 inch during October. Laramie and Rawlins average about 0.80 to 1.2 inches of precipitation in each of the three months.
2. Current situation:
The event known as La Nina has ended and generally neutral conditions are being observed over most of the tropical Pacific Ocean. Some warmer than average water temperatures are now being observed over the far eastern tropical Pacific as depicted in Figure 1 below, but it is too early to tell if this is the beginning of an El Nino event.
More information can be found at the Climate Prediction Center’s website here:
http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.html
Drought Status: Overall drought conditions have changed little across the region with some worsening of the drought noted over the southern Nebraska panhandle. Much of the area’s drought status remained in normal conditions to abnormally dry conditions. A relatively small area of moderate drought condition (primarily hydrologic in nature due to low reservoir levels) is over the western Nebraska panhandle, as can be seen in Figure 2 below:
Figure 2: July 29, 2008 Drought Status
The latest drought status and more information can be found at the National Drought Mitigation Centers website here: http://www.drought.unl.edu/
August through October Outlook
Temperature:
The Climate Prediction Center’s three month temperature outlook for this area indicates that there are equal chances that temperatures will be above average, near average, or below average for the period, as depicted by Figure 3 below.
Figure 3: August – October 2008 Temperature Outlook
The local downscaled temperature outlook, which provides the temperature outlook for more specific sites as opposed to a general area, shows a slightly greater likelihood for average or below average temperatures across most local sites. Specific probabilities for selected locations in this area are shown in Table 1:
|
Location |
Probability Above Normal |
Probability Near Normal |
Probability Below Normal |
|
Cheyenne |
32% |
33% |
35% |
|
Laramie |
34% |
34% |
32% |
|
Medicine Bow |
32% |
34% |
34% |
|
Scottsbluff |
33% |
34% |
33% |
|
Sidney |
32% |
34% |
34% |
|
N. Neb. Panh. |
32% |
34% |
34% |
Table 1
More information on the Local 3 Month Temperature Outlook can be found here:
http://www.weather.gov/climate/calendar_outlook.php?wfo=cys
Precipitation:
For precipitation, the latest outlook indicates that above average precipitation is favored across most of the central Rocky Mountains and the central plains during the period…especially from far southeast Wyoming into northeast Colorado and the entire Nebraska panhandle. Equal chances for above, near, or below average precipitation is forecast for most of northern and western Wyoming as depicted in Figure 4 below:
Figure 4: August – October 2008 Precipitation Outlook
The latest drought outlook (see Figure 5 below) indicates that the current drought situation over the region is not expected to change significantly during the remainder of the summer into early Fall, though some improvement is possible over the northern Nebraska panhandle.
Figure 5: Seasonal Drought Outlook
Issued July 17, 2008
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