557  
FOCN45 CWWG 052000  
SIGNIFICANT WEATHER DISCUSSION ISSUED BY THE PRAIRIE AND ARCTIC STORM  
PREDICTION CENTRE OF ENVIRONMENT CANADA AT 2:00 PM CST SATURDAY  
DECEMBER 5 2020.  
 
ALERTS IN EFFECT....FREEZING RAIN WARNING FOR FORT LIARD. SPECIAL  
WEATHER STATEMENT FOR THE SOUTHERN AND CENTRAL NORTHWEST TERRITORIES.  
 
SYNOPTIC OVERVIEW...ALOFT THIS AFTERNOON, THERE IS AN UPPER RIDGE  
OVER WESTERN CANADA. A SHORTWAVE UPPER TROUGH IS OVER NORTHWESTERN  
ONTARIO, TRACKING INTO MINNESOTA. A DEEP UPPER TROUGH EXTENDS FROM  
THE POLAR VORTEX OVER GREENLAND SOUTHWARDS TO A WEAK UPPER LOW OVER  
SOUTHERN BAFFIN ISLAND THEN CONTINUING SOUTHWARD INTO QUEBEC. A  
SHORT WAVE TROUGH IS OFF THE WEST COAST. AN UPPER LOW SITS NORTH OF  
THE BEAUFORT SEA. SHORT WAVE TROUGH OVER NW BC TRACKING NEWD  
SUOPPORTING FREEZING PRECIP AT WATSOIN LAKE AT THIS TIME.  
 
AT THE SURFACE, A 1039 MB HIGH SITS OVER SOUTHERN BC AND ALBERTA,  
WITH A WEAK RIDGE OVER NORTHWESTERN ONTARIO EXTENDING NORTHWARDS  
INTO NORTHERN MANITOBA AND THE KIVALLIQ. A WEAK 1001 MB LOW SITS  
JUST SOUTH OF BAFFIN ISLAND AND A 1006 MB LOW SITS NORTH OF GREAT  
SLAVE LAKE WITH A TRAILING COLD FRONT/TROUGH BACK WESTWARDS TO A 991  
MB LOW OVER THE GULF OF ALASKA, NORTH OF HAIDA GWAII. FINALLY,  
THERE IS A 993 MB LOW NORTH OF THE BEAUFORT SEA.  
 
DISCUSSION...  
 
WESTERN PRAIRIES...TEMPERATURES CONTINUE TO BE 5 TO 15 DEGREES ABOVE  
NORMAL AND THE TREND WILL CONTINUE INTO NEXT WEEK. SOME DAILY MAXIMUM  
TEMPERATURE RECORDS MAY BE BROKEN TODAY.  
 
EASTERN PRAIRIES...NIL SIG WX, AS ABOVE-SEASONAL TEMPERATURES WILL  
PERSIST THROUGH THE WEEK INTO AT LEAST THE FIRST HALF OF NEXT WEEK.  
UMOS/SCRIBE DAYTIME HIGHS CONTINUE TO BE TOO COLD WHILE OVERNIGHT  
LOWS ARE TOO WARM, SO APPROPRIATE ADJUSTMENTS HAVE BEEN MADE TO THE  
PUBLIC FORECASTS. PATCHY FOG EXPECTED TO RE-DEVELOP OVER PARTS OF  
NORTHERN MANITOBA OVERNIGHT TONIGHT AND PERHAPS EXTENDING SOUTHWARDS  
INTO PARTS OF CENTRAL AND SOUTHERN MANITOBA. FOG PATCHES WILL LINGER  
THROUGH MUCH OF THE DAY IN NORTHERN SASKATCHEWAN.  
 
WESTERN ARCTIC...TODAY WILL BE THE RELATIVE CALM BEFORE THE STORM,  
WITH JUST SOME LIGHT SNOW FORECAST FOR THE CENTRAL MACKENZIE. THIS  
EVENING A LOW PRESSURE SYSTEM WILL BEGIN TO ENTER THE NWT SUPPORTED  
BY THE SHORT WAVE TROUGH CURRENTLY OVER NW BC. THIS WILL BRING A  
MIX OF PRECIPITATION. THE MAIN AREA OF SNOW WILL BE IN THE CENTRAL  
MACKENZIE, WHERE 5 TO 10 CM IS EXPECTED BY NOON ON SUNDAY.  
DENDRITIC GROWTH ZONE WITH NEW MODEL RUNS LOOKS INTERESTING SO WE  
WILL BE RE-EVALUATIONG AMOUNTS PRIOR TO AFTERNOON ISSUE ESP IN THE  
VICINTY OF NORMAN WELLS. FURTHER SOUTH, PATCHY FREEZING RAIN IS  
LIKELY FROM FORT LIARD TO LUTSELKE, INCLUDING YELLOWKNIFE. THE  
FREEZING RAIN WILL BEGIN TONIGHT IN FORT LIARD AND SPREAD EASTWARDS  
THROUGH THE OVERNIGHT AND INTO SUNDAY MORNING AND WILL END OR  
CHANGE TO SNOW BY SUNDAY AFTERNOON. THE SYSTEM EXITS THE AREA  
SUNDAY EVENING, JUST AS THE NEXT LOW BEGINS TO MOVE IN.  
 
HIGH ARCTIC...THE FORECAST LOOKS PROBLEMATIC FOR  
SACHS HARBOUR WITH LOTS OF BLOWING SNOW LIKELY BUT AT THIS TIME  
CONDITIONS LOOK TO REMAIN A BLOWING SNOW SITUATION RATHER THAN A  
BLIZZARD.  
 
EASTERN ARCTIC...THE TROUGH OFF THE WEST COAST WILL INDUCE  
CYCLOGENESIS OVER THE NWT TONIGHT, AND THAT LOW WILL ROCKET EAST OVER  
THE SUBSEQUENT 24 HOURS. JUST NORTH OF ITS TRACK WILL FALL SOME SNOW,  
AND THE TOTALS MAY PUSH 10 CM. THE PRIMARY AXIS FOR THIS POTENTIAL  
APPEARS TO BE FROM ABOUT BAKER LAKE TO NAUJAAT. WARNINGS MAY BE  
NECESSARY AS THE EVENT DRAWS NEARER.  
 
END/STAMMERS/PROCTOR  
 
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