ZCZC SPCSWOMCD ALL
ACUS11 KWNS 020314 
SPC MCD 020314 
WAZ000-ORZ000-020915-

MESOSCALE DISCUSSION 2004
NWS STORM PREDICTION CENTER NORMAN OK
0914 PM CST TUE DEC 01 2015

AREAS AFFECTED...PORTIONS OF THE COLUMBIA RIVER BASIN OF NRN ORE AND
SRN WA

CONCERNING...FREEZING RAIN 

VALID 020314Z - 020915Z

SUMMARY...INITIAL SNOW/SLEET SHOULD TRANSITION TO MAINLY FREEZING
RAIN OVER THE NEXT FEW HOURS AS PRECIPITATION MOVES IN FROM THE
WEST. FREEZING-RAIN RATES WILL LIKELY EXCEED 0.05 INCH PER 3
HOURS...WITH RATES UP TO 0.1 INCH PER HOUR POSSIBLE THROUGH 09Z.

DISCUSSION...THE SFC GRADIENT BETWEEN AN AREA OF COLD HIGH PRESSURE
ACROSS THE NRN GREAT BASIN/ROCKIES AND LOWER PRESSURE OVER THE ERN
PACIFIC HAS ENCOURAGED ELY WINDS THROUGH THE COLUMBIA RIVER BASIN
TODAY. SFC TEMPERATURES THROUGH MOST OF THE BASIN REMAIN AOB
FREEZING AS OF 03Z...AND PRECIPITATION SHIFTING EWD FROM THE COAST
ASSOCIATED WITH A SHORTWAVE TROUGH SHOULD SPREAD OVER THE MCD AREA
IN THE NEXT FEW HOURS. RECENT AMDAR SOUNDINGS IN THE VICINITY OF
KPDX SHOW A PROMINENT WARM NOSE OF +6-9 DEG C CENTERED AROUND
925-900 MB. HOWEVER...FORECAST SOUNDINGS FROM THE LATEST NAM/HRRR
SUGGEST THIS WARM LAYER DOES NOT EXTEND MUCH FURTHER E THAN KPDX.
THEREFORE...PRECIPITATION ACROSS THE LOWER ELEVATIONS OF THE
COLUMBIA RIVER BASIN MAY INITIALLY BEGIN AS SNOW/SLEET...BEFORE
TRANSITIONING TO FREEZING RAIN AS SWLY WARM AIR ADVECTION OCCURS
MAINLY IN THE 850-700-MB LAYER. FREEZING-RAIN RATES WILL LIKELY
EXCEED 0.05 INCH PER 3 HOURS...AND RATES UP TO 0.1 INCH PER HOUR MAY
BE POSSIBLE.

..GLEASON.. 12/02/2015

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...PDT...PQR...

LAT...LON   45841967 45571968 45371999 45282081 45282176 45342224
            45542232 45842223 45922175 46032062 46011983 45841967 

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