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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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