The Nation's Weather 12.15.09

By WEATHER UNDERGROUND (AP)

Two weather systems were forecast to produce unsettling weather activity in the West and East on Tuesday.

A strong Pacific front was set to hit the Pacific Northwest and northern California with significant onshore flow and moisture. Energy along the front was expected to combine with rich Pacific moisture to produce swaths of lower elevation rainfall and high elevation snowfall throughout the regions. Gusty winds were forecast to accompany precipitation throughout the day. Precipitation in northern California was expected to spread southward into Monterrey Bay.

A weak ridge of high pressure was also expected to keep showers from spreading into southern California, while ridging was forecast to translate into warmer and drier weather conditions in the south.

In the East, low pressure over the Great Lakes was expected to continue to produce a mix of lake effect rain and snow showers as it shifted into the Lower Great Lakes and the Northeast. The heaviest snow totals are expected to develop to the east of the Great Lakes.

Meanwhile, an associated cold front was forecast to stretch across the Mid-Atlantic and the Southeast, mingling with moisture from the Gulf of Mexico to produce another round of light showers and thunderstorms.

Elsewhere, high pressure in the Central U.S. was forecast to keep a frigid air mass locked over the Plains and the Midwest.

Temperatures in the Lower 48 states Monday ranged from a low of -32 degrees at Jordan, Montana to a high of 87 degrees at Naples, Florida.