Snow Returns to the Northwest's Mountains.

It is always something to celebrate and enjoy.  After a dry/warm summer, the first pulse of cooler air moves in from the northwest behind an upper level trough of low pressure.  The first light snow over our higher elevations.  

And it happened last night.   Here are some cam shots Sunday morning to illustrate.  And the fun is not over yet.

We start with the parking lots of Mount Rainier's visitor center, where a snow plow is already at work.

Or at the Olympic Mountain's Hurricane ridge

Both of these locations are around 5000- 5500 ft, and so far the snow has generally been above 4500ft.  But as shown by the latest aircraft reports over Seattle, the freezing level is still dropping, so snow could get down to 4000 ft today.  In fact, there was even a light dusting at Steven's Pass:

The figure below shows temperatures (red lines) and winds (barbs) above Seattle over time (time increases to the left).   Heights are in pressure (850 indicates about 5000 ft).  The winds are westerly, which produces substantial upslope precipitation. Note that 0C (freezing) line has gotten down to 850 hPa (about 5000 ft).   And snow doesn't melt immediately when it warms, it takes approximately another 1000 ft to disappear.  That is why some snow got to Stevens, whose base is roughly 4000 ft.

The latest infrared satellite picture (8 AM, below) shows cool, instability clouds (mottled appearance, called open cellular convection) offshore, with a comma-shaped cloud mass making landfall right now.  This kind of feature is a real snow producer!

 The radar imagery at the same time show these cool showers clearly.  They will reach the Cascades mid-morning.

The latest model runs suggest substantial snowfall over the higher volcanic peaks and the north Cascades during the next 24-h.   Some places may get more than a foot!

The National Weather Service has a Winter Storm Warning up for the higher elevations.  The text will warm the hearts of all skiers and water managers (see below).  

WAZ513-567>569-020000-
/O.CON.KSEW.WS.W.0004.000000T0000Z-151102T1900Z/
OLYMPICS-CASCADES OF WHATCOM AND SKAGIT COUNTIES-
CASCADES OF SNOHOMISH AND KING COUNTIES-
CASCADES OF PIERCE AND LEWIS COUNTIES-
437 AM PST SUN NOV 1 2015

...WINTER STORM WARNING REMAINS IN EFFECT UNTIL 11 AM PST MONDAY...

* SOME AFFECTED LOCATIONS...MOUNT BAKER...HURRICANE RIDGE...
  PARADISE...STEVENS PASS...WHITE PASS...RAINY PASS...CHINOOK
  PASS.

* TIMING...SNOW SHOWERS WILL FALL IN THE MOUNTAINS TODAY AND
  TONIGHT. THE HEAVIER SNOW WILL OCCUR TODAY...WITH INTENSE BURSTS
  OF SNOW LIKELY. SNOW SHOWERS WILL TAPER OFF MONDAY.

* SNOW LEVEL...4000 TO 4500 FEET TODAY THROUGH MONDAY.

* SNOW ACCUMULATIONS...TODAY THROUGH TONIGHT... HURRICANE RIDGE: 4
  TO 6 INCHES. RAINY PASS: 7 TO 13 INCHES. MOUNT BAKER: 7 TO 13 INCHES.
  STEVENS PASS: 2 TO 8 INCHES. SNOQUALMIE PASS: NO ACCUMULATION.
  CHINOOK PASS: 5 TO 10 INCHES. WHITE PASS: 4 TO 8 INCHES.
  PARADISE: 13 TO 20 INCHES.

* MAIN IMPACT...THIS WILL BE THE FIRST SIGNIFICANT SNOWFALL OF THE
  SEASON FOR THE HIGHER PASSES AND MOUNTAIN HIGHWAYS. TRAVELERS
  SHOULD BE PREPARED FOR SLIPPERY ROADWAYS...POOR VISIBILITY...AND
  POSSIBLE TRAVEL DELAYS ON THE HIGHER PASSES.