048  
FOCN45 CWWG 181300  
SIGNIFICANT WEATHER DISCUSSION ISSUED BY THE PRAIRIE AND ARCTIC STORM  
PREDICTION CENTRE OF ENVIRONMENT CANADA AT 7:00 AM CST TUESDAY  
DECEMBER 18 2018.  
 
ALERTS IN EFFECT...SNOWFALL WARNING FOR ALBERTA MOUNTAIN PARKS. WIND  
WARNING FOR PORTIONS OF SOUTHWESTERN ALBERTA.  
 
SYNOPTIC OVERVIEW...ALOFT, BROAD LONG WAVE UPPER RIDGE OVER THE  
PRAIRIE PROVINCES PARTIALLY FLATTENED WITH SIGNIFICANT SHORTWAVE  
UPPER TROF OVER NORTHERN MB. WHILE THIS SW EXITS EASTWARD TODAY, A  
SECOND DIGGING SHORTWAVE NEAR THE BC COAST WILL PASS THRU SOUTHERN  
AB TODAY, SOUTHERN SK TONIGHT AND SOUTHERN MB TUESDAY.  
 
DISCUSSION...  
 
ALBERTA...STRONG CROSS BARRIER FLOW RESULTING IN A COUPLE OF  
PHENOMENA TODAY. FIRST, STRONG DOWNSLOPE WINDS WILL PERSIST  
THROUGH THE DAY ALONG THE LEE OF THE ROCKIES. GUSTS OF OVER  
110 KM/H HAVE BEEN REPORTED NEAR THE MONTANA BORDER THIS  
MORNING. THE WINDS ARE EXPECTED TO GRADUALLY WEAKEN THIS  
EVENING AS THE FLOW ALOFT VEERS TO NORTHWEST AND THE SURFACE LEE  
TROUGH MOVES EASTWARD.  
THE SECOND RESULT IS UPSLOPE PRECIPITATION ADVECTING IN FROM THE  
WINDWARD SIDE OF THE MOUNTAINS. HIGHER ELEVATIONS COULD SEE SNOW  
AMOUNTS IN EXCESS OF 10 CM BY TONIGHT.  
 
ERN PRAIRIES...  
ACCUMULATING SNOW AHEAD OF SHORTWAVE TROF NORTHEASTERN MB TODAY.  
FORECAST SOUNDINGS SHOW DEEP EXPOSURE TO DENDETIC GROWTH ZONE SO  
PRECIPIATION EFFICIENCY AND SNOW/LIQUID RATIO SHOULD BE HIGHER THAN  
AVERAGE; 5 TO 10 CM LIKELY ALONG HUDSON BAY COAST TODAY.  
 
THE PASSAGE OF PACIFIC SHORTWAVE AND ASSOCIATED JET STREAK TO  
SUPPORT RIPPLE IN THE BAROCLINICITY IN THE EASTERN PRAIRIES. PATCHY  
PRECIPITATION TO PASS THRU SOUTHERN SK TONIGHT AND SOUTHERN MB EARLY  
TUESDAY. TRANSIENT AREAS OF SHOWERS, FLURRIES, OR LIGHT FREEZING  
RAIN POSSIBLE.  
 
ERN ARCTIC...  
DISSIPATING OCCLUDED LOW WILL PASS THRU SOUTHEASTERN BAFFIN ISLAND  
TODAY BRINGING SOME LIGHT SNOW.  
 
OUTLOOK: THE LONG RANGE MODELS REBUILD THE UPPER RIDGE MID WEEK THEN  
PASS ANOTHER IMPULSE THRU TOWARDS THE WEAKEND. GFS SHOWS A  
POSSIBLE COLORADO SYSTEM FOR THE EASTERN PRAIRIES JUST AFTER XMAS.  
 
END/BAGGALEY/MARK  
 
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