212  
FXCN01 CWAO 182030  
 
DAYS 1 TO 7 UPDATED SIGNIFICANT WEATHER DISCUSSION - WEST  
 
PREVIOUS DAYS 1 TO 3 SIGNIFICANT WEATHER DISCUSSION AVAILABLE HERE:  
[HTTP://COLLABORATION.CMC.EC.GC.CA/CMC/CMOP/FXCN/20180118/FX_D1-3_WEST_2018011800.HTML]  
 
PREVIOUS DAYS 4 TO 7 SIGNIFICANT WEATHER DISCUSSION AVAILABLE HERE:  
[HTTP://COLLABORATION.CMC.EC.GC.CA/CMC/CMOP/FXCN/20180118/FX_D4-7_WEST_2018011800.HTML]  
 
DAYS 1 TO 3 DISCUSSION UPDATE:  
VALID 12Z THURSDAY JANUARY 18 2018 - 12Z SUNDAY JANUARY 21 2018  
 
NORTHERN PRAIRIES SYSTEM THURSDAY WEAKENING TO TROUGH FRIDAY-SATURDAY...  
PREFERRED GUIDANCE: RDPS  
SCENARIO CONFIDENCE LEVEL: MEDIUM-HIGH  
THERE ARE SOME DIFFERENCES IN THE DETAILS BUT AT THE END THE RDPS IS WELL  
SUPPORTED BY THE OTHER GUIDANCE FOR BOTH THE PROGRESSION AND THE QPF ASSOCIATED  
WITH THIS SYSTEM. THE SURFACE TROUGH LEFT OVER THE EASTERN PRAIRIES ONCE THE  
MAIN SYSTEM HAS REACHED NORTHWESTERN ON LACKS SUPPORT HENCE THE DYNAMIC  
ASSOCIATED WITH THAT FEATURE IS WEAK AND THE ASSOCIATED QPF LIGHT. THE RDPS  
SEEMS TO CAPTURE WELL THIS EVENT AND IT FINDS SUPPORT FROM THE OTHER GUIDANCE  
REGARDING THE PRECIPITATION AMOUNTS.  
 
WEAKENING COLD LOW OFF THE WEST COAST THURSDAY-FRIDAY...  
PREFERRED GUIDANCE: ECMWF/GDPS (RDPS STILL ACCEPTABLE)  
SCENARIO CONFIDENCE LEVEL: MEDIUM-HIGH  
NO UPDATE NEEDED.  
 
PACIFIC SYSTEM REACHING THE WEST COAST LATE SATURDAY...  
PREFERRED GUIDANCE: GDPS UNTIL SUNDAY 18-00Z, GFS AFTERWARDS.  
SCENARIO CONFIDENCE LEVEL: MEDIUM  
NOT MUCH TO ADD TO WHAT HAS BEEN SAID IN THE ORIGINAL FX. THE RDPS MASS FIELD  
LOOKS OK BUT BY T+48 IT BECOMES TOO DEEP WITH THE LEADING UPPER TROUGH AS IT  
MOVES OVER BC. QPF-WISE, RDPS/GDPS LOOK FINE UNTIL T+60. THEN THEY ARE MUCH  
LOWER WITH QPF OVER VANCOUVER ISLAND COMPARED TO GFS/UKMET AND THE ECMWF SEEMS  
TO SUPPORT THE HIGHER QPF AMOUNTS SOLUTION. REPS SUPPORTS THE CANADIAN MODEL  
SOLUTION WITH MAX QPF AROUND 30-40 MM FOR A 24H PERIOD ENDING ON 18-00Z.  
FOREIGN MODELS ARE MORE IN THE 70-90MM RANGE DURING THE SAME PERIOD.  
 
DAYS 4 TO 7 DISCUSSION UPDATE:  
VALID 12Z SUNDAY JANUARY 21 2018 - 00Z THURSDAY JANUARY 25 2018  
 
WEST COAST SYSTEM MOVING EAST TO AB MONDAY-TUESDAY...  
PREFERRED GUIDANCE: ECMWF  
SCENARIO CONFIDENCE LEVEL: MEDIUM-LOW  
AGAIN THERE IS A LACK OF GOOD CONSENSUS SOLUTION HERE. GDPS SEEMS TOO WEAK WITH  
THE UPPER RIDGE OVER THE WESTERN PRAIRIES HENCE TOO FAR TO THE SOUTHEAST WITH  
THE LEE SIDE DEVELOPMENT. HOWEVER, WHILE THE GDPS SLOWS DOWN ON TUESDAY THE  
ECMWF/GFS SPEED UP SO THAT AT THE END PRETTY MUCH AT THE SAME PLACE OVER  
SOUTHERN MB. HERE THE ECMWF SLOWER AND FURTHER NORTH SOLUTION IS PREFERRED  
TO THE GDPS ONE. GFS HAS MORE OR LESS THE SAME TIMING AS THE ECMWF BUT SEEMS TO  
HAVE A LACK OF PRECIPITATION OVER THE PRAIRIES.  
 
EASTERN PACIFIC/GULF OF AK LOW WEDNESDAY...  
PREFERRED GUIDANCE: ECMWF (GDPS TOO DEEP)  
SCENARIO CONFIDENCE LEVEL: MEDIUM-LOW  
GDPS REMAINS TOO DEEP, TOO FAR TO THE NORTHEAST AND ALSO TOO HIGH WITH THE QPF  
OVER VANCOUVER ISLAND LIKELY DUE TO A TOO STRONG ONSHORE FLOW OVER VANCOUVER  
ISLAND. THERE IS NO SUPPORT FOR SUCH HIGH AMOUNTS AND WE REJECT THIS SCENARIO  
TODAY. MODELS PROPOSED BY THE PREVIOUS SHIFT ARE STILL SUGGESTED.  
 
THE COMPLETE VERSION OF THIS DISCUSSION IS AVAILABLE AT THE FOLLOWING LINK:  
[HTTP://COLLABORATION.CMC.EC.GC.CA/CMC/CMOP/FXCN/20180118/FX_D1-7_WEST_2018011812.HTML]  
 
END/CHOUINARD  
 
 
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