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Forecasting Precipitation
scaffolding activity

Forecasting precipitation requires the consideration of many factors. Sometimes simple mathematics can be an effective tool for predicting when precipitation will occur, however, this method alone is always reliable. It is important to consider sources of moisture and lifting mechanisms in the development of precipitation. The purpose of this activity is to introduce some indicators that useful for predicting when and where precipitation is going to occur. Key words throughout this activity link directly to helper resources that provide useful information for answering the questions.

Key Components:
1) Why is moisture necessary for precipitation to develop?

2) What role do fronts play in the development of precipitation?

3) Describe what happens as an parcel of air rises upwards through the atmosphere.

Forecasting Scenarios:
4) For the following weather scenarios, indicate if precipitation is "likely" or "unlikely" to occur given the conditions described in each scenario. Explain why.

Weather Scenario Precipitation?
Example Scenario:
Boulder, CO, a city on the east side of the Rockies. Downslope winds are expected.
Unlikely Downslope winds (or wind blowing down the mountain) tend to be very dry, warming as it descends, creating an unfavorable environment for the development of precipitation (since rising air in the presence of downslope winds is unlikely).
Scenario 1:
A cold front is approaching from the west, but the air both ahead of and behind the front is very dry.
Scenario 2:
A warm front is approaching and the air behind and ahead of the front is very moist.
Scenario 3:
Upslope winds are expected in Boulder, CO and the air has been very moist for the past couple of days.
Scenario 4: The trend for the latest batch of precipitation is a steady eastward movement of 30 miles/hour. The latest position is roughly 700 west of here. Will precipitation arrive within 24 hours?

Terms for using data resources. CD-ROM available.
Credits and Acknowledgments for WW2010.
Department of Atmospheric Sciences (DAS) at
the University of Illinois at Urbana-Champaign.