CASPER'S CLIMATOLOGY

Casper,Wyoming lies in the central portion of the state in the North Platte River Valley at an elevation of 5,300 feet. The Natrona County International Airport, where the readings are taken for the WxChallenge, is located about 8 miles west-northwest of town at an elevation 200 feet higher. Most of the land surrounding Casper is hilly with flat prairie land extending in most directions, except to the south where Casper Mountain extends 3,500 feet above the city.  The picture to the right shows Casper Mountain rising above the downtown area on a clear, sunny day.

                                                                                                                                                    This is an image of Casper, Wyoming with Casper
                                                                                                                                                    Mountain in the background, courtesy of Wikipedia .

Casper has a semi-arid climate, with most of the air masses moving in from the Pacific Ocean; however, the high mountains to the west serve as moisture barriers, blocking much of the precipitation that is common closer to the coast.  The image below is a topographical map of Wyoming from ESRL which shows these high mountains to the west of Casper, as well as smaller mountains just to the south.  


This is a topographical map of Wyoming which shows Casper's proximity to the high Rocky
Mountains, courtesy of Earth System Research Laboratory (ESRL).

As I mentioned, the wind plays an important role in Casper's weather.  The wind rose, below, shows that the wind predominately blows from the southwest in October, because of the gap in the Rocky Mountains southwest of town, as you can see on the topographical map above.  Also, west winds downsloping off the mountains often raise the temperature here, in addition to blocking precipitation.  Even though the windiest times of year are in the winter and spring, the average wind speed in October is still a breezy 10 knots.


This is a wind rose plot, showing Casper's wind in October blows mostly from the southwest, courtesy of National Resources Conservation
Service.

Knowing the average temperatures and precipitation, as well as the extremes, will be a big advantage in the WxChallenge.  Here are the Daily Almanacs for the contest period: October 14, October 15, October 16, October 17, October 21, October 22, October 23, and October 24. From these Daily Almanacs, you can see the average high temperatures range from 61 degrees on October 14 to 55 degrees on October 24.  These temperatures are a good starting point in predicting what the actuals will be.  On the other hand, the record high temperatures for this period range from 77 degrees to 83 degrees.  Also, it's important to know the lowest maximum temperatures on record, which at this time of year varies from 26 degrees to 35 degrees. Most likely, the first snow or arctic outbreak of the season contributes to these low temperatures.

The Daily Almanacs show the average low temperatures range from 33 degrees on October 14 to 29 degrees on October 24; however, the record lows get much colder.  They vary from 9 to 20 degrees at this time.  Milder weather is still not out of the question, though. The highest minimum temperatures in Casper range from 45 to 52 degrees.                        
                                                                                                                                                                                      
As I said, Casper has a semi-arid climate, therefore, the average daily precipitation is only .03 inches or .04 inches. This list of daily  rainfall records shows October 21 the record is only .18 inches and October 16 it's up to 2.06 inches.  Finally, the Local Climate Data for Casper shows that the record two-minute sustained wind speed for October is 51 mph (44 knots).  So, predicting a wind speed higher than this would be a very bad idea.

Next, I'll examine the "big picture" on one of the days my forecast busted in Casper.


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