YELLOW ALERT - Big Storm Potential

Posted by Rufus La Lone on

Friday October 22
Rain, wind, high mountain snow, dangerous surf, thunderstorms, tornado potential, sunshine.  Wow.  Refill that Mug and read on to find out what may happen outside the next several days.
Yesterday, a very powerful storm formed well away from the coast, ushering in some wind & plenty of moisture to the region.  That Low was termed a ‘bomb cyclone’ because it deepened (to about 953 mb) so quickly as it approached the PNW.  It tracked northeast toward Haidi Gwaii, BC as it finally filled in (center pressure rises).  Hence, it’s impact was nominal for most Patrons.  
First on our radar (pun intended): another potentially more powerful ‘bomb cyclone’, is modeled to form this Sunday, Oct 24 - but this time, it is likely to track closer to NW in the Sunday/Monday period.  Below is a portion of Portland Nat’l Wx Service Meteorologist Neuman discussion, posted early this morning:
Much like the days ahead of yesterday`s bomb cyclone, members
of the EPS remain generally the strongest with the majority of
members strengthening Sunday`s low pressure to somewhere between
940-950mb. Anything sub-950mb would result in the lowest pressure
observed in the northeast Pacific in the vicinity of 130W and 45N
in recorded history.
Note, there have been deeper low pressures
observed elsewhere in the northern Pacific closer to the Aleutian
Islands and Gulf of Alaska. Meanwhile, most members of the GEFS and
CMCE are slightly weaker and generally bottom the low pressure out
near 950-955mb. Where the low pressure tracks once it begins to weaken
remains the biggest uncertainty.
(Bold font is my emphasis)
Your WxCafé focus today, Fri Oct 22, is for additional rain/showers today into early Saturday.  Then, the big storm.  Although there's lots of uncertainty about the strength and path the Sunday/Monday monster storm, Patrons should prepare for the impact.  Coastal areas will have severe erosion issues, as well as dangerous sneaker waves; atmospheric attributes will favor the potential for coastal zone tornado development (as Neuman mentioned, similar to Oct 14, 2016); WIND gusts up to 45 mph inland (less likely: gusts to 60 are also charted by some models); heavy rain.  This storm will cover a large area, so site-specific forecast conditions may vary, depending on your location - from northern CA to BC.  Power outages are probable in many locations.  Please HEED Nat’l Wx Service watches & warnings.
Our weekend storm will impact northern CA, as well, with brisk wind & heavy rain. There is an indication that a weaker, secondary Low may form and make landfall between the central OR coast north to WA, keeping it rather windy on Tue.  Overall, expect plenty of rain, showers, occasionally strong wind gusts on into the middle of next week.  Late week we could see some drying, which will be appreciated.  
Weekend of Oct 30,31 is trending mostly dry, with Halloween not expected to be a chilly as earlier.  The start of November is trending rather mixed, with a few days of moderate-to-heavy rain & wind along with a few dry days.  We’ll sort this out later.
The variability of storm strength, how many of them, and when they arrive is always in play.  Therefore, this forecast is different from our last.  That’s the nature of what we do here and why you need a good morn’n beverage in that Mug!
Below is a capture from one of the model outlooks for our big storm on Sunday.  Note how deep (959 mb) the Low is modeled as it crosses THE 130W line, moving NW.  The Columbus Day storm of Oct ’62 had a depth of 956-960 mb, but tracked N-NW well inside the 130W line along the OR & WA coast.  Our Sunday/Monday system will be tracking much farther N before it crosses the 130W.  Still, this warrants attention.
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