MESOSCALE PRECIPITATION DISCUSSION 0015
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1254 PM EST THU JAN 21 2016
 
AREAS AFFECTED...W WASHINGTON...NW OREGON 
 
CONCERNING...HEAVY RAINFALL 
 
VALID 211800Z - 220300Z
 
SUMMARY...HIGHLY MERIDIONAL ATMOSPHERIC RIVER TO BEGIN TO REDUCE
THREAT ACROSS WA/OR...LIMITING FLOODING THREAT TO THE NEXT 3-4
HOURS

DISCUSSION...BLENDED TPW ANALYSIS INDICATES AMPLE MOISTURE WITH
VALUES IN THE 1.2-1.3" RANGE ACROSS A 200 MILE WIDE PLUME AHEAD OF
A SLOW MOVING COLD FRONT THAT IS GENERALLY ORIENTED NORTH-SOUTH
NEARLY PARALLEL TO THE COASTLINE. WV LOOP SHOWS MULTIPLE
DEVELOPING BAROCLINIC SHIELDS/SHORTWAVE RIDGING OCCURRING; THE
FIRST NEAR 43.5N130W AND THE SECOND FURTHER SOUTH NEAR 37N130W. 
THE INITIAL WAVE WILL CONTINUE TO TRACK NORTH TOWARD THE OLYMPIC
RANGE TIMING ABOUT 20-21Z TIME FRAME WITH A SLUG OF INCREASED RAIN
RATES PER RECENT AMSU PASS TO .25" WHICH SHOULD ENHANCE FOR A FEW
HOURS OF NEAR .5"/HR RATES IN OROGRAPHIC ASCENT...PARTICULARLY
GIVEN THE 60-70KT 85-7H UNIDIRECTIONAL SSWLY FLOW.  AFTER THE WAVE
PASSES...A EASTWARD ADVANCEMENT OF THE COLD FRONT WILL START
REDUCING THE MST FLUX AND DRY OUT FROM W TO E BY 00Z ACROSS THE
OLYMPICS WITH THE POTENTIAL OF UP OF AN ADDITIONAL 2".

FURTHER SOUTH...STRONG 130-150KT UPPER LEVEL JET IS DIGGING SOUTH
OF THE SOUTHERN INFLECTION/BAROCLINIC LEAF...LIKELY ENHANCING IT. 
THIS WILL EFFECTIVELY STALL THE EASTWARD PROGRESS OF THE FRONTAL
ZONE OFF THE OREGON COASTLINE AND LIMIT ONSHORE FLOW BEING MORE
PARALLEL TO THE COASTLINE AND REDUCED OROGRAPHIC PROFILE ACROSS
THE OREGON COASTAL RANGE.  WITH THIS DEEPENING FURTHER
SOUTH...EXPOSURE FROM SOUTHERLY FLOW WILL LIKELY BE BLOCKED BY
CAPE BLANCO AND SHIFT THE FOCUS OF ONSHORE MST FLUX INTO SW
OREGON/NW CALIFORNIA.  

GALLINA

ATTN...WFO...MFR...PQR...SEW...

ATTN...RFC...NWRFC...

LAT...LON   48262410 48062286 47142286 45492310 43902351 
            43882436 45712414 47002449 48072486 48072466