There is potential for some accumulating lowland snow early Tuesday morning, January 17 that may affect the morning commute. The main threat for snow accumulations will be above 500 feet, but some locations on the valley floor may get a quick inch of snow if under a snow shower, while other valley locations may see only snow showers and no accumulation.
There is a more potent storm system expected Tuesday night and Wednesday.
· SYNOPSIS:
o A very cold air mass remains over the Pacific NW and will continue through Wednesday. A weather disturbance will move across the area late tonight into Tuesday morning and will produce some light snow accumulations, mainly above 500 feet.
o A stronger system with much more moisture will move into the region from the southwest Tuesday night into Wednesday. This system will overrun the existing cold air with the potential to produce some significant snowfall accumulations over part of the area. The challenge in this system is how fast the cold air will erode, and geographically, where the rain-snow transition line will be. This system also has the potential to produce strong, damaging winds for the Coast and Coast Range. Breezy to windy conditions will be possible in the Willamette Valley.
· PRIMARY AREAS IMPACTED:
o Late Monday night into Tuesday morning: Another batch of organized snow showers will impact most areas, with 1 to 3 inch of snowfall accumulations possible above 500 feet. Locations below 500 feet may get a quick inch of snow if a shower passes over the area, but other locations may get no accumulations. This scenario is similar to the Sunday (Jan 15) snow showers that occurred.
o Tuesday night into Wednesday morning: Wintry precipitation potential, primarily as snow in the North Willamette Valley, Clark County/Lower Columbia, Columbia River Gorge, and other areas of Southwest Washington. Snow is also expected in the Coast Range, Foothills and Cascades with this system.
o Strong, potentially damaging winds (mainly Wednesday am) along the Coast and Coast Range.
· IMPACTS:
o Hazardous travel conditions at times in most areas. The morning commute Tuesday may be impacted by slick roads.
o Significant lowland snow accumulations late Tuesday night into Wednesday.
o Strong, potentially damaging winds along the Coast and Coast Range Wednesday. These winds may down power lines and trees.
· TIMING:
o Early Tuesday morning (commute time): 1 to 3 inches of snow accumulation, mainly above 500 feet.
o Late Tuesday night into Wednesday: Potential for significant snowfall accumulation and transition from snow to freezing rain over part of the areas.
o Early Wednesday morning through midday: Strong, potentially damaging wind storm.
· FORECAST CONFIDENCE:
o High Confidence:
§ High winds along the Coast and Coast Range early Wednesday.
o Moderate confidence:
§ An organized batch of snow showers early Tuesday morning with accumulating snow above 500 feet.
o Low Confidence:
§ Snow accumulations on valley floor Tuesday morning. Some areas may get a quick inch, other locations may get none.
§ Low confidence in the initial precipitation type and amounts of accumulating precipitation (e.g. snow, freezing rain, or rain) Tuesday night into Wednesday
· UNCERTAINTIES:
o Uncertainty remains rather high for the Tuesday night /early Wednesday system concerning the geographic location where the transition zone of snow, freezing rain and rain will be. This will be highly dependent on storm track.
o Also uncertainty on how fast the cold air will erode with the Tuesday night/Wednesday system.
There is a more potent storm system expected Tuesday night and Wednesday.
· SYNOPSIS:
o A very cold air mass remains over the Pacific NW and will continue through Wednesday. A weather disturbance will move across the area late tonight into Tuesday morning and will produce some light snow accumulations, mainly above 500 feet.
o A stronger system with much more moisture will move into the region from the southwest Tuesday night into Wednesday. This system will overrun the existing cold air with the potential to produce some significant snowfall accumulations over part of the area. The challenge in this system is how fast the cold air will erode, and geographically, where the rain-snow transition line will be. This system also has the potential to produce strong, damaging winds for the Coast and Coast Range. Breezy to windy conditions will be possible in the Willamette Valley.
· PRIMARY AREAS IMPACTED:
o Late Monday night into Tuesday morning: Another batch of organized snow showers will impact most areas, with 1 to 3 inch of snowfall accumulations possible above 500 feet. Locations below 500 feet may get a quick inch of snow if a shower passes over the area, but other locations may get no accumulations. This scenario is similar to the Sunday (Jan 15) snow showers that occurred.
o Tuesday night into Wednesday morning: Wintry precipitation potential, primarily as snow in the North Willamette Valley, Clark County/Lower Columbia, Columbia River Gorge, and other areas of Southwest Washington. Snow is also expected in the Coast Range, Foothills and Cascades with this system.
o Strong, potentially damaging winds (mainly Wednesday am) along the Coast and Coast Range.
· IMPACTS:
o Hazardous travel conditions at times in most areas. The morning commute Tuesday may be impacted by slick roads.
o Significant lowland snow accumulations late Tuesday night into Wednesday.
o Strong, potentially damaging winds along the Coast and Coast Range Wednesday. These winds may down power lines and trees.
· TIMING:
o Early Tuesday morning (commute time): 1 to 3 inches of snow accumulation, mainly above 500 feet.
o Late Tuesday night into Wednesday: Potential for significant snowfall accumulation and transition from snow to freezing rain over part of the areas.
o Early Wednesday morning through midday: Strong, potentially damaging wind storm.
· FORECAST CONFIDENCE:
o High Confidence:
§ High winds along the Coast and Coast Range early Wednesday.
o Moderate confidence:
§ An organized batch of snow showers early Tuesday morning with accumulating snow above 500 feet.
o Low Confidence:
§ Snow accumulations on valley floor Tuesday morning. Some areas may get a quick inch, other locations may get none.
§ Low confidence in the initial precipitation type and amounts of accumulating precipitation (e.g. snow, freezing rain, or rain) Tuesday night into Wednesday
· UNCERTAINTIES:
o Uncertainty remains rather high for the Tuesday night /early Wednesday system concerning the geographic location where the transition zone of snow, freezing rain and rain will be. This will be highly dependent on storm track.
o Also uncertainty on how fast the cold air will erode with the Tuesday night/Wednesday system.
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