Portland, Oregon Blog #2
Portland's weather is affected dominantly by Maritime air masses. In winter, the region is primarily affected by Maritime Polar air, bringing moisture and moderating temperatures. Continental Polar air can also enter into the region, bringing cold, dry air. In summer, Portland is more likely affected by Maritime Tropical and occasionally Continental Polar air.
The maps below show the air masses and the associated weather.
Pictures source: http://www.sci.uidaho.edu/scripter/geog100/lect/05-atmos-water-wx/05-part-6-air-masses/ch5-part-6-air-masses.htm
Portland's latitude can receive mid-latitude cyclones, as well as warm, cold, and occluded fronts. Generally, the occluded fronts here are warm occluded fronts, as diagrammed in the picture below.
Picture source: Chambers, Frederick. Moisture and Precipitation Processes-Part 2. PowerPoint Presentation, Slide 10, Geography 3232. April 2, 2012.
Meteorologist Nick Allard of Portland NewsChannel 8 predicted on Tuesday, April 3rd "Rain is moving in this morning as a slow moving cold front hits the area.", "Once the rain starts it will stick around for most of the day becoming showers by mid to late afternoon. Highs will be in the low to mid-50s.
Picture source: http://www.kgw.com/weather/maps?radar=63612987&img=9&c=y
Portland has topographic features that influence weather. Portland lies in the valley between the Coast and Cascade Ranges. Warmer moist air from the Pacific Ocean is forced to rise over the Coast Range, which receives precipitation. Portland is warmer and dryer than the Coast Range because air warms adiabatically as it comes down over the mountains into the rain shadow. This air is then again orographically lifted over the Cascade Range, condensing and cooling, allowing for precipitation.
Picture source: http://www.wildpnw.com/2011/06/20/rain-shadow-effect-pacific-northwest/#.T3tC5mBhwVk
Meteorologist Nick Allard of Portland NewsChannel 8 predicted on Tuesday, April 3rd "Rain is moving in this morning as a slow moving cold front hits the area.", "Once the rain starts it will stick around for most of the day becoming showers by mid to late afternoon. Highs will be in the low to mid-50s.
After the cold front moves through cooler air will push in and keep the pattern unsettled. In fact we'll see showers and possibly hail showers or even thunderstorms on Wednesday and Thursday. Look for a few more showers on Friday but we'll be drying out overall into the weekend.", "NICE!"
Current weather maps for the Portland region show a cold front approaching.
Portland has topographic features that influence weather. Portland lies in the valley between the Coast and Cascade Ranges. Warmer moist air from the Pacific Ocean is forced to rise over the Coast Range, which receives precipitation. Portland is warmer and dryer than the Coast Range because air warms adiabatically as it comes down over the mountains into the rain shadow. This air is then again orographically lifted over the Cascade Range, condensing and cooling, allowing for precipitation.
This picture highlights how prevailing winds and topography affect the weather in the Portland region.
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