368
FOCN45 CWWG 111900
SIGNIFICANT WEATHER DISCUSSION ISSUED BY THE PRAIRIE AND ARCTIC STORM
PREDICTION CENTRE OF ENVIRONMENT CANADA AT 2:00 PM CDT MONDAY AUGUST
11 2025.
ALERTS IN EFFECT...AIR QUALITY ALERTS FOR MOST OF MANITOBA AND
PORTIONS OF NORTHERN SASKATCHEWAN. RAINFALL WARNING FOR CHESTERFIELD
INLET.
SYNOPTIC OVERVIEW...
ALOFT, THE MARITIME JET AXIS CROSSES INTO THE WEST COAST VIA
NORTHERN BC BEFORE DIVING SOUTHEASTWARDS ABOUT A TROUGH THAT
STRETCHES FROM A LOW CENTRE OVER NORTHERN DAVIS STRAIT ALL THE WAY
DOWN TO THE DAKOTAS. THE JET THEN TAKES A MARKED TURN
NORTHEASTWARDS, CUTTING THROUGH NORTHERN QUEBEC, RIDING THE RIDGE
OVER THE MARITIMES. SLIGHT RIDGING IS EVIDENT OVER THE WESTERN
ARCTIC. THE ARCTIC FRONT ENCIRCLES THE LOW CENTRE OVER NORTHERN
DAVIS STRAIT. LOW OVER EASTERN ALASKA. SHORTWAVE TROUGH WEST OF
BANKS ISLAND.
AT THE SURFACE, RIDGING PUSHES INTO CENTRAL BC FROM THE EASTERN
PACIFIC, CROSSING THE ALBERTA ROCKIES INTO WESTERN REGIONS OF THE
PROVINCE. A 1000 MB LOW CENTRE RUNS ALONG THE 60TH PARALLEL BETWEEN
CHURCHILL AND ARVIAT WITH A COLD FRONT MEANDERING WESTWARDS. A
SURFACE TROUGH ALSO EXTENDS SOUTHWARDS, MEETING THE POLAR WAVE AND
POTENT SHORTWAVE OVER SOUTHERN MANITOBA. WEST OF THE TROUGH, A
STRONG NORTHWESTERLY FLOW HAS SET UP BACK TO THE BC BORDER. UP
NORTH, A WEAK LOW CENTRE HUGS THE BEAUFORT SEA COASTLINE WITH
THE NT, WHILE A WEAK HIGH CENTRE LIES FURTHER EAST, OVER EASTERN
VICTORIA ISLAND. LASTLY, THE QS LOW CENTRE REMAINS OVER NORTHERN
DAVIS STRAIT FOR YET ANOTHER DAY.
DISCUSSION...
NRN SK...SMOKE IS CAUSING VERY POOR AIR QUALITY AND REDUCED
VISIBILITY AT TIMES, IN SOME LOCATIONS. NORTHERLY WINDS TODAY WILL
PUSH SMOKE TO THE SOUTH. ON TUESDAY WINDS ARE FORECAST TO SHIFT TO
BLOW FROM THE EAST SO ALERTS WILL LIKELY BE EXPANDED ACROSS
NORTHERN SASKATCHEWAN AGAIN TOMORROW.
NON-SEVERE THUNDERSTORMS WILL MOVE TO THE SOUTHEAST WITH THE COLD
FRONT FROM THE MB LOW THROUGH THE EVENING. EBWD WILL BE UP TO 20
KT BUT MLCAPES ARE ONLY 250-500 J/KG. PWAT VALUES ARE RELATIVELY
HIGH BUT ANY ORGANIZED STORMS WILL BE MOVING FAIRLY QUICKLY SO DON'T
EXPECT MORE THAN LOCALIZED AMOUNTS OF 5-10 MM.
SRN SK/MB...A HIGHLY UNSTABLE NORTHWESTERLY FLOW ACROSS THE SOUTHERN
PRAIRIES WILL HELP ADVECT A BROAD AREA OF CONVECTION FROM WEST TO
EAST THROUGH THE REGION MONDAY. OUT AHEAD OF THE WARM SECTOR TROUGH,
MOST THE EARLY CONVECTION HAS BEEN PLAIN SHOWERS AS IT PASSED OVER
SOUTHERN MB THIS MORNING AND EARLY AFTERNOON. HOWEVER, AS THE TROUGH
ENCOUNTERS A SUNNIER, SLIGHTLY RICHER CAPE ENVIRONMENT OVER
SOUTHEASTERN SK/SOUTHERN MB MID-AFTERNOON, A FEW OF THUNDERSTORMS
MAY TURN SEVERE IN NATURE. ISOLATED CELLS, NOTABLY NEAR THE
INTERNATIONAL BORDER WHERE MLCAPES APPROACH 1000 J/KG COULD AID IN
THE PRODUCTION OF QUARTER-SIZED HAIL. STRONG WIND GUSTS ARE
VERY LIKELY WITH BUNKER VECTORS OF 35 TO 40 KTS, ALONG WITH THE
POSSIBILITY OF SOMEWHAT MORE ORGANIZED AND PERSISTENT SQUALL LINES
FORMING OVER SE SK/SW MB TOWARD EVENING. TRAINING STORMS COULD
PRODUCE HEAVY RAINFALL WITH PWATS =>35 MM OVER SOUTHERN MB BY 00Z
TUESDAY - PARTICULARLY CLOSEST TO THE SHORTWAVE TRACK ACROSS THE
SOUTHERN LAKE BASINS. CONVECTION WILL BE SUPPORTED BY SAID SHORTWAVE
THROUGH EASTERN MB MONDAY NIGHT, WITH MOST OF THE CONVECTION PROGGED
TO MOVE INTO NORTHWESTERN ONTARIO BY MID-MORNING TUESDAY.
WINDS WILL GUST UP TO 70 KM/H ON THE BACKSIDE OF THE NU/MB LOW AT
CHURCHILL MONDAY NIGHT INTO TUESDAY MORNING. LIGHT RAIN WILL
ACCOMPANY THE GUSTS, ALTHOUGH AMOUNTS WILL RATHER NEGLIGIBLE.
THE SMOKE PLUME OVER SOUTHERN MANITOBA WILL LINGER MONDAY, SLOWLY
CLEARING FROM WEST TO EAST ACROSS THE PROVINCE THROUGHOUT THE DAY.
AIR QUALITY ALERTS WILL BE ADJUSTED AS NECESSARY. ANOTHER PUSH OF
SMOKE WILL QUICKLY FOLLOW ACROSS THE SOUTHERN PRAIRIES MONDAY NIGHT
THANKS IN LARGE PART TO THE BROAD NORTHWESTERLY FLOW. PM2.5
CONCENTRATIONS, FOR THE MOST PART, DO NOT LOOK TO BE AS HIGH WITH
THIS NEXT SHOT OF SMOKE. HOWEVER, MODELS ARE PICKING UP ON ONE PLUME
OF CONCERN SLATED TO TRAVEL TOWARDS SOUTHERN MB MONDAY NIGHT INTO
TUESDAY MORNING. THIS WILL BE MONITORED WITH ADDITIONAL ALERTS
ISSUED IF WARRANTED. WINDS WILL TURN EASTERLY OVER THE MAJOR FIRES
IN THE NORTH ON WEDNESDAY, THEN DIRECTING FRESH SMOKE AWAY FROM
THE MAJOR POPULATION CENTRES FOR A COUPLE DAYS.
NUNAVUT...THE LOW ALONG NU/MB BORDER WILL CONTINUE TO PRODUCE
RAINFALL TO MOST OF THE KIVALLIQ ON MONDAY. AN ADDITIONAL 10 TO 15
MM IS EXPECTED FROM CHESTERFIELD INLET WITH SIMILAR AMOUNTS STARTING
TODAY FOR RANKIN INLET AND PERHAPS AS MUCH AS 20 MM FOR ARVIAT. A
RAINFALL WARNING REMAINS IN EFFECT FOR CHESTERFIELD INLET WHERE THE
RAINFALL BEGAN LAST NIGHT. WINDS GUSTING UP TO 60 TO 70 KM/H WILL
FOLLOW THE RAIN MONDAY EVENING IN ARVIAT.
AB/NT...THE ALASKA UPPER LOW WILL MOVE INTO NW AB BY TUESDAY
EVENING. MOST OF THE WESTERN MAINLAND NT WILL SEE SHOWERS WITH
THUNDERSTORMS TODAY. MLCAPE VALUES UP TO 1000 J/KG AND EBWD AROUND
15 KT. COULD SEE SOME LOCALLY HEAVIER RAIN UP TO 25 MM AND POSSIBLY
SOME HAIL UP TO 2 CM. A WIDER SPREAD AREA OF RAINFALL OF 10-25 MM
WILL ACCOMPANY THE LOW AS IT MOVES TO THE SE THROUGH TOMORROW.
END/KNIGHT/GREENHOUGH
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