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FOCN45 CWWG 041900
SIGNIFICANT WEATHER DISCUSSION ISSUED BY THE PRAIRIE AND ARCTIC STORM
PREDICTION CENTRE OF ENVIRONMENT CANADA AT 2:00 PM CDT SATURDAY
OCTOBER 4 2025.
ALERTS IN EFFECT...RAINFALL WARNING FOR SOUTHERN MANITOBA.
SYNOPTIC OVERVIEW...ALOFT, A RIDGE IS OVER THE EASTERN PACIFIC, WITH
A BROAD TROUGH CENTERED OVER ALBERTA AND THE NORTHWEST TERRITORIES
WITH AN UPPER LOW OVER THE BEAUFORT SEA. DEEPER TROUGHING IS FOUND
FURTHER SOUTH OVER THE WESTERN UNITED STATES TIED TO AN UPPER LOW
OVER UTAH. SHORTWAVES ARE LOCATED OVER NORTHEASTERN ALBERTA AND NEAR
THE YT/BC BORDER WITHIN THIS TROUGH. AN UPPER LOW IS CENTRED OVER
BAFFIN BAY, AND AN UPPER TROUGH IS LOCATED WEST OF BANKS ISLAND,
EXTENDING WESTWARDS INTO THE BEAUFORT SEA. BROAD UPPER RIDGING LIES
OVER EASTERN CANADA LEAVING THE EASTERN PRAIRIES IN AN ACTIVE
SOUTHWESTERLY UPPER FLOW WITH NUMEROUS EMBEDDED IMPULSES.
AT THE SURFACE, A 991 MB LOW IS CENTRED OVER THE CENTRAL KITIKMEOT,
WITH A WARM FRONT EXTENDING TO THE EAST AND A COLD FRONT EXTENDING
SOUTHWEST, BISECTING SASKACTHEWAN. A 1002 MB LOW IS OVER SOUTHEASTERN
MANITOBA, WITH A COLD FRONT EXTENDING SOUTHWARD AND A WARM FRONT
NORTHEASTWARD. ANOTHER LOW IS OVER THE HIGH ARCTIC, NEAR ELLESMERE
ISLAND. HIGH PRESSURE LIES OVER THE EASTERN PACIFIC, EXTENDING INTO
NORTHERN BC AND THE YUKON. A WEAK LOW LIES OVER THE WESTERN NWT.
DISCUSSION...
AB...A COLD FRONT SWEEPING THROUGH THE PRAIRIES HAS RESULTED
IN A COOLING, UNSTABLE AIR MASS WITH CONVECTIVE SHOWERS, FLURRIES,
THE POSSIBILITY OF A FEW LIGHTNING STRIKES NEAR THE ROCKY MOUNTAINS
THIS AFTERNOON, AND GUSTY WINDS ACROSS THE PROVINCE.
TEMPERATURES AND HEIGHTS WILL CONTINUE TO FALL TONIGHT, WHICH WILL
SWITCH A LOT OF PRECIPITATION OVER TO A MIX OF RAIN/SNOW OR JUST
SNOW, PARTICULARLY OVER HIGHER TERRAIN. AREAS ALONG THE SOUTHERN
ROCKIES ARE LIKLEY TO SEE HEAVIER SNOWFALL AMOUNTS THANKS IN PART TO
THE BUILDING SURFACE RIDGE (GENERATING UPSLOPE FLOW) AND UNSTABLE
NATURE OF THE AIR MASS. SNOWFALL TOTALS OVER THE EXTREME SW NEAR THE
U.S. BORDER COULD BE IN EXCESS OF 10-15 CM, BUT THIS WILL DEPEND
HEAVILY ON THE SNOWFALL RATES, AND WHETHER MELTING WILL OCCUR DURING
THE FIRST FEW HOURS OF SNOW. A SNOWFALL WARNING WAS CONSIDERED,
HOWEVER CONFIDENCE IS LOW THAT SNOWFALL TOTALS WILL EXCEED 15 CM BY
EVENT END.
SK/MB...ANOTHER COLORADO LOW IS EXPECTED TO DEVELOP STATESIDE AND
MOVE NORTHEASTWARDS INTO SOUTHERN MANITOBA SATURDAY NIGHT INTO
SUNDAY.
FIRST, A SLIGHT RISK OF SEVERE THUNDERSTORMS WILL DEVELOP LATE
SATURDAY OVER EXTREME SOUTHEASTERN MANITOBA AS A WARM FRONT LIFTS
NORTHWARD WITH ELEVATED INSTABILITY BUILDING INTO THE REGION, ALBEIT
TO A MUCH LESSER EXTENT THAN LAST NIGHT. MUCAPE VALUES WILL BE IN THE
500 TO 1000 J/KG RANGE WITH 50 KNOTS OF BWD SO PRIMARY THREATS WILL
BE 2-4 CM HAIL, 80-90 KM/H WIND GUSTS AND TORRENTIAL RAIN. AN ADHOC
SUITE OF THUNDERSTORM OUTLOOKS WILL BE ISSUED LATER TODAY FOR
SATURDAY INTO SUNDAY HIGHLIGHTING THESE RISKS.
SECOND, AND OF PERHAPS GREATER CONCERN, IS STEADY AND INTENSIFYING
RAIN ALONG AND NORTHWEST OF THE WARM FRONT WHICH WILL STALL OVER
SOUTHEASTERN MANITOBA LATER SATURDAY NIGHT INTO SUNDAY. MODEL MEAN
QPF TOTALS REMAIN IN THE 50 TO 70 MM RANGE FOR PORTIONS OF THE RED
RIVER VALLEY AND SE MB FOR LATE SATURDAY THROUGH END OF SUNDAY.
AMOUNTS WILL BE HIGHLY VARIABLE DUE TO THE CONVECTIVE NATURE OF THE
PRECIPITATION, WITH 30 TO 50 MM EXPECTED ACROSS THE RRV INCLUDING
WINNIPEG AND 50 TO 70 MM FORECAST OVER THE SOUTHERN RRV AND
SOUTHEASTERN MANITOBA. RAINFALL WARNINGS HAVE BEEN ISSUED FOR
SOUTHEASTERN MANITOBA AND WILL CONTINUE TO BE UPDATED AS THE EVENT
UNFOLDS.
NT...ONSHORE FLURRIES ARE EXPECTED OVER THE NEXT 24 HOURS GENERALLY
FOR THE ARCTIC COAST. A WEAK LOW PRESSURE SYSTEM WILL GIVE SOME LIGHT
RAIN OR WET SNOW TO A NUMBER OF COMMUNITIES OVER THE SOUTHERN NT
TONIGHT AND SUNDAY. AN ONSHORE FLOW COULD HELP ENHANCE RAINFALL IN
THE FORT RESOLUTION REGION TODAY.
NU...A STRENGTHENING LOW PRESSURE SYSTEM OVER THE EASTERN KITIKMEOT
LOOKS TO FIRST BRING RAIN, FOLLOWED BY STRONG WINDS (GUSTING TO 60 OR
70 KM/H) FOLLOWED BY SNOW TO NIGHT INTO SUNDAY OVER THE REGION.
FORECASTING SNOWFALL AMOUNTS IS A LITTLE TRICKY GIVEN TEMPERATURES
NEAR ZERO AND THE TIGHT QPF GRADIENT, BUT GENERALLY THESE COMMUNITIES
COULD EXPECT TO SEE 2-4 CENTIMETRES OF SNOW TONIGHT OR SUNDAY.
FURTHER SIGNIFICANT SNOWFALL AND STRONG WINDS ARE POSSIBLE OVER
KUGAARUK TONIGHT. THIS SYSTEM WILL ALSO BRING MODERATE RAIN AND SNOW
TO THE KIVALLIQ REGION WITH WINDS GUSTING TO 80 KM/H ON SUNDAY.
THE STRONGEST WINDS WILL BE AT CHESTERFIELD INLET, AND MAY FLIRT WITH
WARNING CRITERIA SO THIS WILL HAVE TO BE MONITORED CLOSELY AS THE
EVENT NEARS.
END/STAMMERS/PIMISKERN
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