Weather 12-10-19

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Weather satellite indicates a continued northerly flow aloft over the forecast area this morning under a sharp high pressure ridge just ahead of an approaching Pacific storm system. Low stratus clouds and patchy fog is present in most of the Columbia Basin and Wenatchee Valley locations with limited visibility and patchy freezing fog. These areas that are socked in under low clouds will probably remain that way through the day but clouds may lift a bit this afternoon. The presence of this stratus and the short daylight period will likely keep temperatures from rising appreciably in these cloudy with afternoon high temperatures today across Northcentral Washington in the mid 30’s. There is also a 60% chance of rain mixed with snow after 4:00 p.m.

Then, tonight through Wednesday a fast moving weather system will arrive bringing a 70% chance of a rain/snow mix. This wave is visible on satellite just off the coast of Oregon this morning. The system is shaping up to resemble the stronger and wetter suite of models from previous runs. The overnight time of transit will bring high confidence that most precipitation will be snow, with a ghost of a chance of freezing rain pockets in the far southern portions of the basin, south of the I-90 corridor. The fast moving nature of the wave will preclude any major snow accumulations, with probably no more than a couple inches in the mountains and a trace to an inch in the deep basin and up to an inch or so over the rising terrain of the eastern basin which coming overnight and thus impacting the Wednesday morning commute period will probably lead to a slippery drive to work for area motorists on Wednesday morning. Shortly after dawn on Wednesday this quick hitter will be passing off to the east leaving mostly cloudy skies during the day tomorrow with highs in the mid to upper 30’s.

Wednesday night and Thursday, weather models continue to show an active period as a strong zonal jet stream takes aim across Oregon with a series of waves riding along and north of the jet into Washington and north Idaho. There is a 70% chance of rain mixed with snow Wednesday night and a 50% chance of precipitation on Thursday with afternoon highs near 40 degrees. Moderate snow accumulations are likely in the mountains with travel impacts likely over the mountain passes, with light accumulations possible for the northern valleys, Cascade valleys, and Waterville Plateau before a switch to rain. The I-90 corridor and points south are expected to see valley rain/mountain snow.

For Friday through the weekend, showers will end and our skies will become mainly partly cloudy as our flow turns northwesterly with afternoon high temperatures in the lower 40’s on Friday, with mid to upper 30’s expected for Saturday and Sunday.