789  
FOCN45 CWWG 152000  
SIGNIFICANT WEATHER DISCUSSION ISSUED BY THE PRAIRIE AND ARCTIC STORM  
PREDICTION CENTRE OF ENVIRONMENT CANADA AT 2:00 PM CST FRIDAY  
DECEMBER 15 2017.  
 
ALERTS IN EFFECT... FREEZING RAIN WARNING FOR ILE-A-LA-CROSSE.  
SNOWFALL WARNING IN YELLOWKNIFE.  
 
SYNOPTIC OVERVIEW... BREAKDOWN OF THE STAGNANT RIDGE-TROUGH PATTERN  
OVER NORTH AMERICA IS UNDERWAY AS THE UPPER RIDGE OVER BRITISH  
COLUMBIA CONTINUES TO COLLAPSE SOUTHWARDS. UPPER LOW HAS CRESTED THE  
APEX OF THE RIDGE IN THE SOUTHWESTERN NWT AND IS NOW SLUMPING  
SOUTHEASTWARDS. A LARGE VORTEX CONTINUES TO SIT OVER A SIZEABLE  
PORTION OF EASTERN CANADA AND THE EASTERN ARCTIC WITH NUMEROUS  
SHORTWAVES ROTATING WITHIN IT, BUT NONE AS POTENT AS THE MAJOR UPPER  
LOW SITUATED OVER THE NORTHERN TIP OF LABRADOR.  
 
AT THE SURFACE, A DEVELOPING 994 MB SOUTHEASTWARD TRACKING LOW NEAR  
HAY RIVER HAS A WARM FRONT EXTENDING SOUTHEASTWARDS THROUGH NORTHERN  
ALBERTA, ACROSS SASKATCHEWAN, THEN INTO NORTH-CENTRAL NORTH DAKOTA.  
A SECOND FRONTAL WAVE WHICH MOVED INTO NORTHWESTERN ALBERTA DURING  
THE NIGHT IS NOW LOCATED NEAR SASKATOON WITH A COLD FRONT SWEEPING  
SOUTHWESTWARDS. IN THE EAST, A MAJOR LOW PRESSURE SYSTEM OVER  
NORTHERN LABRADOR IS NOW WEAKENING, WITH A CENTRAL PRESSURE AT 18Z  
OF 962 MB. HOWEVER ANOTHER DEVELOPING 966 MB LOW OFF THE SOUTHWEST  
TIP OF GREENLAND IS REINFORCING THE WHOLE LOW COMPLEX AS IT TRACKS  
WESTWARD.  
 
DISCUSSION...  
 
PRAIRIES...FREEZING RAIN REMAINS POSSIBLE IN BUFFALO NARROWS  
REGION EARLY THIS AFTERNOON BUT POTENTIAL IS DIMINISHING. THE  
DEVELOPING NWT LOW WILL CONTINUE TO BE THE PRIMARY WEATHER MAKER AS  
SNOW INTENSIFIES AHEAD OF THE WARM FRONT. 24-HOUR SNOWFALL TOTALS  
OF 10 TO 15 CM ARE FORECAST OVER NORTHERN AND EAST-CENTRAL  
SASKATCHEWAN, WITH LOWER AMOUNTS OF 5 TO 10 CM EXPECTED THROUGH  
SOUTHEASTERN SASKATCHEWAN AND SOUTHWESTERN MANITOBA. BEHIND THE LOW,  
WITH THE GUSTY COLD FRONT DROPPING THROUGH ALBERTA, A BAND OF  
SHOWERS WILL TRANSITION TO FLURRIES THIS AFTERNOON AS THE  
TEMPERATURES BEGIN TO FALL. LA RONGE AND KEY LAKE WILL BE CLOSE TO  
THE 10CM IN 12 HOUR THRESHOLD TODAY. BUFFALO NARROWS PICKED UP 6 CM  
IN 7 HOURS THIS MORNING.  
 
50 KNOT JET EAST OF EDMONTON THIS AFTERNOON WILL BRING SOME GUSTY NW  
WINDS. NOT EXPECTING ALL OF THE WINDS TO MIX BUT COULD SEE GUSTS IN  
THE 70 TO 80 KM/H RANGE OVER EAST CENTRAL ALBERTA.  
 
IN SOUTHERN SASKATCHEWAN TODAY, A WINTERY MIX EXPECTED AS FLURRIES  
CHANGE TO SHOWERS WEST OF THE FRONT AS TEMPERATURES CLIMB INTO THE  
+2 TO +4C RANGE. ALONG THE FRONT, PARTICULARLY ALONG A LINE FROM  
MEADOW LAKE SOUTHEAST TO REGINA, SPOTTY LIGHT FREEZING RAIN MAY HAVE  
OCCURRED THIS MORNING WITH THE TRANSITION FROM BELOW TO ABOVE  
FREEZING. IN THE WAKE OF TODAYS SNOW, FREEZING DRIZZLE WILL BE  
POSSIBLE ACROSS MUCH OF EASTERN SASKATCHEWAN ALONG A TROUGH  
EXTENDING SOUTH-SOUTHEASTWARDS FROM A LOW PRESSURE CENTRE OVER  
NORTHWESTERN SASKATCHEWAN.  
 
IN MANITOBA, SNOW IS FALLING OVER THE PARKLAND AND SOUTH TODAY.  
TOTAL AMOUNTS WILL RANGE FROM ONLY 1 OR 2 CM AT WINNIPEG TO THE 4 TO  
8 CM RANGE IN THE SOUTHWEST AND WEST-CENTRAL AREAS.  
 
WESTERN ARCTIC... YELLOWKNIFE RECIEVED 10 CM THIS MORNING BUT WILL  
TAPER OFF AS THE VORT CENTRE NEAR HAY RIVER SLUMPS SOUTHEASTWARDS.  
POTENTIAL FOR SIMILAR AMOUNTS NEAR GREAT SLAVE LAKE TODAY INTO  
TONIGHT. HIGHER AMOUNTS ARE LIKELY TO BE VERY LOCAL.  
 
EASTERN ARCTIC... MAJOR LOW PRESSURE SYSTEM OVER NORTHERN LABRADOR  
SPREAD WIND GUSTS IN EXCESS OF 90 KM/H OVER PORTIONS OF SOUTHERN  
BAFFIN ISLAND OVERNIGHT, BUT WINDS QUICKLY DIMINISHED DURING THE  
MORNING. EXPECT WINDS TO BE HIGHLY VARIABLE IN SOME LOCATIONS AS  
BROAD SYNOPTIC WIND PATTERN INTERACTS WITH LOCAL TOPOGRAPHY.  
MODERATE WINDS WILL CONTINUE OVER PORTIONS OF SOUTHERN BAFFIN ISLAND  
OVER THE NEXT 36 TO 48 HOURS AS THE LOW SLOWLY MIGRATES  
NORTHEASTWARDS INTO DAVIS STRAIT.  
 
END/MELSNESS/WIELKI  
 
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