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Mesoscale Discussion 9
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   Mesoscale Discussion 0009
   NWS Storm Prediction Center Norman OK
   1252 AM CST Fri Jan 05 2018

   Areas affected...Portions of the eastern slopes of the Cascades and
   Columbia Basin

   Concerning...Freezing rain 

   Valid 050652Z - 051245Z

   SUMMARY...Multiple waves of light to occasionally moderate freezing
   rain will likely impact points east of the Cascade crest through the
   overnight hours. Freezing rain rates of a few hundredths of an inch
   per hour will be possible.

   DISCUSSION...Ahead of a shortwave trough over the eastern Pacific,
   southwesterly mid-level flow is transporting increased moisture
   across the Pacific Northwest late this evening. Within this moist
   conveyor, weak warm advection and related isentropic ascent will
   yield two or more rounds of precipitation overnight, with one
   currently advancing northward across western Washington. While most
   of the heavier precipitation will likely fall west of the Cascades,
   occasional light to moderate precipitation will likely occur across
   eastern Cascade slopes and into the Columbia Basin. Antecedent high
   pressure over the interior is maintaining a shallow layer of
   near-surface temperatures in the upper 20s/lower 30s across this
   region, and forecast soundings indicate a sufficiently deep warm
   nose aloft for complete melting of most hydrometeors. In turn,
   occasional freezing rain (characterized by rates of a few hundredths
   per hour) will remain possible into the morning hours.

   ..Picca.. 01/05/2018

   ...Please see www.spc.noaa.gov for graphic product...

   ATTN...WFO...OTX...PDT...SEW...PQR...

   LAT...LON   45682042 45692132 45742157 45852168 47172143 47652113
               48952057 49011930 49011912 48781892 48171856 47641843
               46391904 45682042 

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Page last modified: January 05, 2018
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