Solutions in red.

The image at left is another depiction of the relationship between the polar jet stream (remember, the jet is high in the troposphere, not at the surface) and warm and cold air masses in the lower troposphere near the surface of the Earth. Cold air masses generally lie north of the jet, and warm air masses to the south. Using this principle, it's possible to make predictions about temperature trends using 300 mb maps that show the position of the polar jet.

All three images at left represent forecasts for 12 UTC (8 AM) Saturday Morning April 14. The first was issued Monday at 12 UTC and represents a 5-day forecast, and is the same image posted below in Monday's . The second was issued Thursday at 12 UTC (8 AM local time) and represents a 2-day forecast.

The Monday forecast shows a pronounced ridge over New England. The jet stream lies to the north of Vermont. It indicates that there is a warm air mass under that ridge over New England. The more recent Thursday forecast shows a less pronounced ridge over New England. The jet stream in this case lies right over Vermont. This means that the warming below the ridge is not as strong as in the 5-day forecast.

The final image shows the actual jet stream on Saturday morning. The jet is not as intense as predicted. You will also note that the core of the jet over New England is further south than predicted. This indicates that the warm air associated with the ridge did not make it as far north as predicted. This should

How is this reflected in the NWS forecast? On Monday, the NWS called for a forecast high temperature of 42 F at Lyndon Center at the bottom of Vail hill. On Thursday, they were still calling for a high of 41 F. Personally, given the look of maps, I would have adjusted my prediction to about 36 F. It is possible that with the clear skies that usually accompany a ridge will allow the sun to warm things up. However, the nor' easter that brought us today's storm will likely bring in low level moisture that will keep things cool and damp.

Sorry, people it looks like more winter.

Final assignment for Saturday/Sunday.

A) Download a map of the actual 300 mb heights at 12Z Saturday morning and compare them to the forecasts. (Click here and click on 000 under 300 mb sometime after 11 AM on Saturday). Pay particular attention to the ridge and jet stream over New England.

B) Check the Saturday high temperature at the course weatherpage. Is it higher or lower than the predicted temperatures? Explain whether these results consistent with your observations of the jet and ridge mentioned above.

The high temperature was 41.7 degrees F recorded at 2:30 PM. As it turns out, errors in predicting the jet did not affect a very accurate 5-day forecast of the high temperature for Saturday. However, this does illustrate that there was a warming (albeit slight) associated with a northward displacement of the jet.