Precipitation in up slope regions may be more persistent, but periods of heavier precipitation will still occur. In zonal flow, the combination of short wave forcing and warm air advection in areas of high precipitable water are the main factors for precipitation in Washington, Oregon and North Idaho. Without both positive temperature advection and short wave forcing, precipitation will likely be light with low areal coverage outside of the up slope regions. Due to limited observations, numerical models may not be able to accurately simulate temperature advection fields until the storm makes landfall. Frequently, the models do not accurately predict the depth of surface lows approaching the coast.
Numerical models are also often unable to accurately simulate the passage of short waves.
Since numerical models poorly forecast short waves during strong zonal flow and misrepresent actual temperature advection fields, close scrutiny of observational data over the Pacific is required to make accurate precipitation forecasts. To assist with the laboratory exercise, a high resolution topography image is provided along with average yearly precipitation maps for Washington , Oregon and Northern Idaho . Identify the location of any synoptic scale surface features. Draw the fronts on the map provided . Identify the areas of precipitation.