MESO: Mesoscale Discussion 0060

ACUS11 KWNS 282143
SWOMCD
SPC MCD 282142
WAZ000-ORZ000-290315-

MESOSCALE DISCUSSION 0060
NWS STORM PREDICTION CENTER NORMAN OK
0342 PM CST MON JAN 28 2013

AREAS AFFECTED...CASCADES OF WA AND NRN ORE

CONCERNING...HEAVY SNOW

VALID 282142Z - 290315Z

SUMMARY...SNOW RATES WILL INCREASE TO 1-2 IN/HR FOR ELEVATIONS AOA
2-2.5 KFT BY 00Z...WITH SIMILAR RATES CONTINUING INTO THE EVENING
HOURS.

DISCUSSION...A RIBBON OF MODESTLY ENHANCED DEEP MOISTURE...
HIGHLIGHTED BY 0.50-0.65-INCH PW VALUES PER GPS DATA...EXTENDS SEWD
INTO THE PACIFIC NW FROM THE FAR E PACIFIC. AND GIVEN THE ONGOING
UPSLOPE FLOW REGIME...REGIONAL MOSAIC RADAR IMAGERY AND SFC OBS
INDICATE WIDESPREAD PRECIPITATION OCCURRING...ESPECIALLY OVER THE
WRN SLOPES OF THE CASCADES. AS A MID-LEVEL SHORTWAVE TROUGH
CONTINUES MOVING SEWD OVER BRITISH COLUMBIA...UPSLOPE FLOW IS
FORECAST TO STRENGTHEN OVER THE CASCADES LATER THIS AFTERNOON INTO
THIS EVENING. RTX VWP DATA DURING THE LAST COUPLE OF HOURS INDICATE
A SUBTLE INCREASE IN THE FLOW BELOW 3 KM AGL...POTENTIALLY IN
ASSOCIATION WITH THE ONSET OF THE STRENGTHENING UPSLOPE FLOW. THE
MORE MARKED INCREASE IN UPSLOPE FLOW IS ANTICIPATED BY 00Z...WITH A
CORRESPONDING INCREASE IN PRECIPITATION RATES. AS SUCH...SNOW RATES
WILL LIKELY REACH 1-2 IN/HR BY 00Z FOR ELEVATIONS AOA 2-2.5 KFT.
THESE RATES ARE FORECAST TO CONTINUE THROUGHOUT THE EVENING HOURS.
ADDITIONALLY...STRENGTHENING SFC WINDS SHOULD YIELD REDUCED
VISIBILITIES IN AREAS OF BLOWING/DRIFTING SNOW.

..COHEN.. 01/28/2013

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

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

LAT...LON 48992117 48862064 48222047 47822059 47232085 46672116
46012144 45252155 44752168 44642203 44922221 45152218
45332213 45682214 45952228 46192235 46652231 47142192
47552175 48052182 48662209 48972193 48992117

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