The Upcoming Lowland Snow Event on Monday

The Upcoming Lowland Snow Event on Monday

Many of you  in western Washington are going to see snowflakes tomorrow.  

But there may be going to an enormous variation from flurries to a number of inches.

The mountains and foothills are going to get hit laborious and the snow-level might be low.

This is a really advanced, marginal occasion with the potential for some surprises.   But just like the COVID-19 vaccines, scientists/forecasts have higher instruments than even a number of years in the past.

Not this a lot.

Before I’m going into element, let me provide the backside line for the Monday snow scenario.   

Temperatures might be marginal for snow, however the place there may be adequate precipitation, snow will attain the floor. The northeast Olympic Peninsula might be hit laborious by 2-12 inches and snow will improve to a number of inches rapidly within the Cascade foothills. Elevations above 200 ft and away from the water may get a dusting to an inch. 

 There is the potential menace of a localized convergence zone that would arrange in central Puget Sound that would lay down a number of inches.

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The scenario

The fashions are all just about in settlement about the important thing elements of the climate sample tomorrow. 

 As proven within the floor climate forecast for Monday at 7 AM, a low strain heart will attain the central WA coast at the moment (the stable strains are isobars, strains of fixed strain).  The shading exhibits low-level temps, indicating cool air (blue) to the north and northwest.  Low degree winds are additionally displayed.  This sample will permit a surge of cooler air to push by means of the Fraser River Valley and jet southward into the Olympics, producing an upslope snow band.

The Upcoming Lowland Snow Event on Monday
The low heart will then push throughout the Cascades and funky air will transfer southward behind it.  Marginal for snow close to the water and the place precipitation intensities are gentle.  And someday harmful may occur at the vanguard of the southward-bound cool air inside the Sound.
1608536742 226 The Upcoming Lowland Snow Event on Monday

Let me present you the accrued SNOWFALL from the UW WRF.  SNOWDEPTH might be MUCH LESS as a result of the bottom is heat.

Here is the entire snowfall from this morning by means of 7AM tomorrow.  At this level, northeasterly winds approaching the Olympics have began the snow occasion there.

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The Upcoming Lowland Snow Event on Monday
By 1 PM,  the northeast Olympics slopes have been hit laborious, with as much as a foot again from the water.  If you reside in Port Angeles or Sequim, be prepared for this, notably in the event you dwell away from the Strait.  More reasonable snow (dusting to an inch) may fall over the San Juans and round Bellingham.
1608536742 771 The Upcoming Lowland Snow Event on Monday
And now it turns into showtime for Puget Sound. 
Cooler, northerly (from the north) air will transfer southward into western Washington and air aloft will flip to the northwest.  Cool, upslope movement will drive the freezing degree down over the Cascade foothills, with a number of inches of snow all the way down to round 750-1000 ft and maybe a bit decrease. Very gentle snow will prolong in direction of the Sound, however change primarily to rain close to the water and sea degree.   The snow complete map by means of 7 PM exhibits the scenario.
1608536743 373 The Upcoming Lowland Snow Event on Monday
But here’s a hazard right here, one which some current mannequin simulations have urged.  
That if a convergence zone units up between the northerlies transferring down the Sound and southerlies coming across the Olympics, a snowband–dropping a number of inches– may arrange.   Here is an instance of it from the newest NWS GFS mannequin for the 6-h snowfall ending 7 PM tomorrow.  I might be watching the following sequence of runs rigorously to see if this seems to be possible.
1608536743 71 The Upcoming Lowland Snow Event on Monday
Finally, as I’ve “skilled” all of you… one ALWAYS wants to have a look at uncertainty–which means contemplating ensembles of many alternative forecasts.  For instance, the UW high-resolution ensemble exhibits loads of uncertainty for snow at SeaTac, however most forecast members have one thing (the mean–black line–is round 1 inch)
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Keep in thoughts that the bottom is heat and air temperatures are NOT forecast to go under freezing….that might be protecting of the streets except the snow comes down too quick for melting.  The newest Seattle SNOWWATCH map exhibits street temperatures within the higher 40s to 50F (see under).   
1608536743 359 The Upcoming Lowland Snow Event on MondayThis goes to be attention-grabbing.

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