899
FOCN45 CWWG 051200
SIGNIFICANT WEATHER DISCUSSION ISSUED BY THE PRAIRIE AND ARCTIC STORM
PREDICTION CENTRE OF ENVIRONMENT CANADA AT 7:00 AM CDT SATURDAY
SEPTEMBER 5 2026.
ALERTS IN EFFECT...RAINFALL WARNING FOR POND INLET. SEVERE
THUNDERSTORM WATCH FOR SOUTHWESTERN MANITOBA. AIR QUALITY WARNING FOR
FORT SIMPSON.
SYNOPTIC OVERVIEW...ALOFT, AN UPPER RIDGE SITS OVER THE NORTHEASTERN
PACIFIC WITH RIDGING INTO ALASKA AND YUKON. THE FLOW DIVES INTO A
DEEP UPPER TROUGH THAT EXTENDS FROM ELLESMERE ISLAND SOUTH THROUGH
NUNAVUT TO THE 60TH PARALLEL, THEN SOUTHWEST TO AN UPPER LOW OVER THE
U.S. PACIFIC NORTHWEST. THE FLOW REBOUNDS INTO A BROAD UPPER RIDGE
OVER THE CENTRAL UNITED STATES NORTHWARDS THROUGH MANITOBA AND NW
ONTARIO AND INTO NORTHERN QUEBEC.
AT THE SURFACE, A 1007 MB LOW SITS OVER THE NORTH DAKOTA/MONTANA
BORDER WITH A COLD FRONT SOUTH AND A WARM FRONT EAST THROUGH NORTH
DAKOTA. TO THE NORTHWEST, A 1026 MB HIGH SITS OVER THE BEAUFORT SEA,
WITH RIDGING EXTENDING SOUTHWARD THROUGH THE NWT AND INTO ALBERTA.
IN THE ARCTIC, A 991 MB LOW SITS JUST NORTH OF POND INLET WITH A
FRONTAL WAVE TO ITS SOUTHWEST; ITS APEX SITS OVER NORTHERN BAFFIN
ISLAND WITH A WARM FRONT EXTENDING EASTWARD INTO BAFFIN BAY AND A
COLD FRONT THAT RUNS SOUTHWEST THROUGH THE KIVALLIQ COAST AND INTO
NORTHERN MANITOBA.
DISCUSSION...
AB...THIS AFTERNOON, MODEST INSTABILITY FROM CORONATION TO
LLOYDMINSTER IN A REASONABLY MOIST AIR MASS AND CLEARER SKIES SHOULD
TRIGGER THUNDERSTORMS IN THE REGION. ALONG A FRONTAL BOUNDARY,
SCATTERED SHOWERS STRETCH ACROSS MUCH OF THE CENTRAL ALBERTA, THE
FOOTHILLS AND THE ROCKIES. IN THE NORTHERN FOOTHILLS, SNOW APPEARS TO
BE FALLING AT OBED SUMMIT THIS MORNING. ISOLATED STRIKES ARE POSSIBLE
IN THE MOUNTAIN PARKS THIS AFTERNOON WITH VERY SLIGHT CAPE INDICATED
ON GUIDANCE, THOUGH CONFIDENCE IS NOT HIGH ENOUGH TO EXPLICITLY
FORECAST THIS YET. SHOWERS AND THUNDERSHOWERS WILL CONTINUE THROUGH
TONIGHT AS A SHORTWAVE MOVES INTO AN AIRMASS WHICH WILL REMAIN
UNSTABLE ALOFT, WITH MUCAPE VALUES AS HIGH AS 1000 J/KG BEFORE
MORNING IN THE CYPRESS HILLS.
EASTERN PRAIRIES...THUNDERSTORMS CONTINUE THIS MORNING IN SOUTHWEST
MANITOBA ALONG A WARM FRONT PUSHING SLOWLY EASTWARD IN NORTH DAKOTA.
THESE STORMS ARE EXPECTED TO WEAKEN AND SLIDE SOUTHEASTWARD ALONG THE
WARM FRONT THROUGH THE MORNING HOURS.
WITH A RELATIVELY STAGNANT UPPER PATTERN OVER THE SOUTHEASTERN
PRAIRIES, HOT, HUMID, AND CONVECTIVE WEATHER WILL PERSIST THIS
WEEKEND. TROUGHING THROUGH SOUTHEASTERN SASKATCHEWAN AND SOUTHWESTERN
MANITOBA STEMMING FROM A LOW PRESSURE SYSTEM ALONG THE MONTANA AND
NORTH DAKOTA BORDER WILL BE THE FOCUS FOR AFTERNOON CONVECTION TODAY.
THE HOT AND HUMID AIRMASS UNDER THE UPPER RIDGE WILL PROVIDE THE HEAT
AND MOISTURE NECESSARY TO PRODUCE 2000+ J/KG OF MLCAPE TODAY.
HOWEVER, WITH ONLY 20-30 KTS OF BULK SHEAR, RELATIVELY WEAK FORCING,
AND LARGE AND WIDESPREAD CIN UNDER THE UPPER RIDGE, THE CONVECTIVE
INITIATION WILL BE HIGHLY CONDITIONAL. WIND WILL BE THE PRIMARY
THREAT WITH STORMS THAT DO INITIATE TODAY, AS DRIER MID-LEVELS
PROMOTE AN ENVIRONMENT WITH HIGH DCAPE VALUES, WITH HEAVY RAIN BEING
THE SECONDARY THREAT. HAIL WILL NOT BE AS MUCH OF A CONCERN, AS HIGH
FREEZING LEVELS WILL INCREASE HAILSTONE MELTING.
MORE SHOWERS AND THUNDERSTORMS ARE FORECAST FOR THE REGION FOR THE
REMAINDER OF THE WEEKEND, BEFORE A MORE PROGRESSIVE LOW PRESSURE
SYSTEM SCOURS OUT THE HOT AND HUMID AIR MASS ON TUESDAY MORNING.
NU...AS THE LOW MOVED OVER NORTHERN BAFFIN ISLAND AND MOISTURE
STREAMED UP FROM THE SOUTHWEST, POND INLET HAS RECEIVED AROUND 50 MM
OF RAIN OVER THE LAST TWO DAYS. WHILE THE HEAVIEST RAIN HAS FALLEN
ALREADY, POND INLET IS EXPECTED TO RECEIVE ANOTHER 5-10 MM BEFORE THE
RAIN TAPERS OFF LATER TODAY. A RAINFALL WARNING REMAINS IN EFFECT FOR
THE SITE FOR THE TIME BEING.
FURTHER SOUTH, MODERATE RAIN SHOWERS HAVE DEVELOPED ALONG THIS
SYSTEM'S COLD FRONT AS IT PUSHES EAST. A QUICK BURST OF 5 TO 10 MM OF
RAIN WILL BE POSSIBLE FROM THE MELVILLE PENINSULA SOUTH TO ARVIAT,
BEFORE THE FRONT PUSHES EASTWARD, BRINGING MORE RAIN TO BAFFIN ISLAND
ON SUNDAY.
BEHIND THE COLD FRONT, MODERATE TO STRONG NORTHWEST WINDS WILL SWEEP
THROUGH MUCH OF THE TERRITORY WITH LOCALIZED WINDS AS HIGH AS 60
GUSTING 80 KM/H LATER TODAY INTO SUNDAY AS A MUCH COOLER AIR MASS
SWEEPS THROUGH THE REGION. FLURRIES WILL FALL OVER EASTERN KITIKMEOT
TONIGHT BUT THERE'S TOO MUCH SPREAD IN GUIDANCE AND TEMPERATURES ARE
STILL TOO WARM TO COMMIT TO AMOUNTS OF 2CM OR MORE.
NT ... DESPITE COOL WEATHER AND LIGHT WINDS, SMOULDERING FIRES
AROUND FORT SIMPSON STILL OCCAISIONALLY REDUCE AIR QUALITY IN
THE COMMUNITY. THE AIR QUALITY WARNING WILL PROBABLY HAVE TO REMAIN
OUT UNTIL MORE SIGNIFICANT PRECIPITATION. OTHERWISE NO SIG WX.
END/COLANGELO/BATE
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