262  
FOCN45 CWWG 251900  
SIGNIFICANT WEATHER DISCUSSION ISSUED BY THE PRAIRIE AND ARCTIC STORM  
PREDICTION CENTRE OF ENVIRONMENT CANADA AT 2:00 PM CDT SUNDAY  
SEPTEMBER 25 2016.  
 
ALERTS IN EFFECT...RAINFALL WARNINGS FOR PORTIONS OF NORTH-CENTRAL  
MANITOBA. FREEZING RAIN WARNING FOR GRISE FIORD. STRONG WIND WARNINGS  
FOR THE WESTERN MANITOBA LAKES AND GALES FOR THE EASTERN LAKES.  
 
SYNOPTIC OVERVIEW...LATE THIS MORNING, A HIGH AMPLITUDE UPPER RIDGE  
OVER HUDSON BAY AND INTO THE HIGH ARCTIC CONTINUES TO DRIFT  
EASTWARD. THIS IS FOLLOWED IMMEDIATELY BY A SHARP UPPER TROUGH  
THROUGH MANITOBA, AND THEN ANOTHER BROADER RIDGE OVER THE REMAINDER  
OF WESTERN CANADA. AT THE SURFACE, A 1001 MB LOW AND OCCLUDING  
FRONTAL WAVE NEAR NORWAY HOUSE IS MOVING NORTHEASTWARD TO LIE NEAR  
GILLAM BY TONIGHT AND IS STARTING TO FILL. A NEW LOW REFORMS ON THE  
WAVE OVER DRYDEN INTO MONDAY. A SURFACE RIDGE OVER ALBERTA BUILDS  
INTO SASKATCHEWAN THROUGHOUT THE PERIOD. UP NORTH, A DECAYING  
FRONTAL WAVE IS CROSSING NORTHERN KIVALLIQ ASSOCIATED WITH A LOW IN  
THE HIGH ARCTIC, WHILE A LARGE SURFACE RIDGE COVERS EASTERN HUDSON  
BAY AND BAFFIN ISLAND.  
 
DISCUSSION...  
 
WESTERN PRAIRIES...RATHER QUIET THIS FORECAST PERIOD.  
 
EASTERN PRAIRIES...RAIN AND A FEW EMBEDDED THUNDERSTORMS ASSOCIATED  
WITH THE UPPER TROUGH AND SURFACE LOW CONTINUE TO STREAM NORTHWARD  
THROUGH THE EASTERN HALF OF MANITOBA. AS THE LOW CONTINUES PUSHING  
NORTHWARD RAINFALL AMOUNTS ARE REACHING WARNING CRITERIA IN  
NORTH-CENTRAL AREAS OF MANITOBA, WITH BERENS RIVER ALREADY AT 57 MM  
AS OF 11 AM. SOME AREAS COULD SEE UPWARDS OF 75 MM ESPECIALLY IN  
THUNDERSTORMS. THE RAIN WILL TAPER OFF IN MANITOBA SOUTHWEST TO  
NORTHEAST TONIGHT, AND THEN MOVE INTO NORTHWESTERN ONTARIO FOR  
MONDAY.  
 
GUSTY NORTHWESTERLY WINDS ON THE BACKSIDE OF THIS SYSTEM WILL  
INCREASE TO 50G70 KM/H TODAY OVER SOUTHERN MANITOBA AS THE GRADIENT  
TIGHTENS BETWEEN THE LOW AND BUILDING RIDGE. GALES ARE EXPECTED FOR  
LAKE WINNIPEG LATER TODAY INTO MONDAY AS A RESULT AS WELL.  
 
EASTERN ARCTIC...SHOWERS AND FLURRIES WILL CONTINUE STREAMING INTO  
KIVALLIQ AND NORTHERN BAFFIN ISLAND AS A WEAKER WAVE MOVES THROUGH  
THE AREA INTO TUESDAY. PRECIPITATION TYPING WILL BE AN ISSUE FOR  
ARCTIC BAY AND POND INLET, BUT WITH SLIGHT WARMING THROUGH THE  
LOW LEVELS, THE BULK OF THE 10-20 MM TOTALS LOOK TO FALL AS RAIN SO  
FAR.  
 
HIGH ARCTIC...THE ABUNDANT WARM AIR ALOFT WILL RESULT IN A RATHER  
SHARP INVERSION OVER GRISE FIORD FOR THE NEXT 24 HOURS. THE TOP-DOWN  
APPROACH TO FORECAST SOUNDINGS SHOWS THAT PRECIPITATION WILL LIKELY  
MELT AND THEN ENCOUNTER A SUB-FREEZING LAYER DOWN LOW.  
AS PRECIPITATION DURATION WILL LIKELY EXCEED 2 HOURS, WE HAVE OPTED  
TO ISSUE A FREEZING RAIN WARNING FOR GRISE FIORD. FREEZING RAIN  
SHOULD CHANGE OVER TO SNOW THIS EVENING OR OVERNIGHT.  
 
END/KNIGHT/MACKAY  
 
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