694
FOCN45 CWWG 291200
SIGNIFICANT WEATHER DISCUSSION ISSUED BY THE PRAIRIE AND ARCTIC STORM
PREDICTION CENTRE OF ENVIRONMENT CANADA AT 7:00 AM CDT SATURDAY
AUGUST 29 2026.
ALERTS IN EFFECT...RAINFALL WARNING FOR FAR NORTHWEST ALBERTA AND
FORT PROVIDENCE. AIR QUALITY WARNINGS FOR FORT MCMURRAY AND FORT
SIMPSON.
SYNOPTIC OVERVIEW...ALOFT, MULTIPLE SHORTWAVES EXIST OVER THE WEST:
ONE OVER NORTHERN ALASKA WITH TROUGHING TO THE SOUTH OF IT, ANOTHER
OVER YUKON, A THIRD OVER BOOTHIA PENINSULA, AND A FOURTH OVER THE
ALBERTA/NWT BORDER. ADDITIONALLY, AN UPPER LOW SPINS OVER THE BC
COAST NEAR THE AMERICAN BORDER WITH THE LONGWAVE TROUGH EXTENDING
SOUTH. THEN, AN UPPER RIDGE ARCS OVER THE SOUTHERN PRAIRIES WHICH
CONTINUES OVER NORTHERN MANITOBA, MAINLAND NUNAVUT, AND OVER BAFFIN
ISLAND. A SHORTWAVE IS EMBEDDED IN THE FLOW OVER MONTANA. FINALLY,
AN UPPER LOW SITS JUST EAST OF JAMES BAY.
AT THE SURFACE, A RIDGE FROM THE PACIFIC OCEAN SPRAWLS OVER BC. A
LOW OVER THE BEAUFORT SEA HAS A TROUGH EXTENDING SOUTH OVER THE
MACKENZIE MOUNTAINS WHICH MEETS ANOTHER LOW OVER GREAT SLAVE LAKE.
TWO TROUGHS EXTEND FROM THIS LOW; ONE TO THE NORTHEAST OVER THE
KITIKMEOT AND INTO THE ARCTIC ISLANDS, THE OTHER TO THE SOUTHEAST
OVER NORTHERN SASKATCHEWN AND INTO CENTRAL MANITOBA. A WEAK LOW
PRESSURE CENTRE SITS OVER SOUTHWEST SASKATCHEWAN. A RIDGE OF HIGH
PRESSURE FROM DAVIS STRAIT EXTENDS SOUTHWEST OVER THE KIVALLIQ AND
INTO NORTHEAST MANITOBA AND NORTHWEST ONTARIO. A SERIES OF LOW
PRESSURE CENTRES EXIST OVER EASTERN HUDSON BAY, NORTHERN QC, AND
LABRADOR.
DISCUSSION...
AB/NRN SK...LOW PRESSURE MATURING OVER THE FORT SMITH REGION WILL
PROVIDE PRECIPITATION TO NORTHWEST ALBERTA TODAY. SOME REPORTS INTO
THE 40S FOR AMOUNTS. FORT VERMILLION HAD 42, WID HAD 33.8, YOJ 50.3.
MOST IS OVER BUT A FURTHER 5 TO 10 MM EXPECTED THIS MORNING AND
POSSIBLY UP TO 20 MM IN WID.
THUNDERSTORMS EXPECTED ALONG THE FOOTHILLS TODAY NORTH OF CALGARY.
SOUTH OF CALGARY IS DRY AND TO THE NORTH GOOD LER OF A JET, MOISTURE
AND CONVERGENCE. NEAR SVR HAIL AND RAIN ARE POSSIBLE DEPENDING ON
SMOKE AND CLOUD COVER THROUGH THE DAY.
MB/SRN SK...ABOVE SEASONAL TEMPERATURES ARE EXPECTED OVER THE
EASTERN PRAIRIES THROUGH THE WEEKEND. SOME PLACES IN SOUTHEAST
SASKATCHEWAN AND SOUTHWEST MANITOBA WILL EXPERIENCE DAYTIME HIGHS
APPROACHING HEAT WARNING CRITERIA TODAY, BUT OVERNIGHT LOWS WILL DIP
BELOW WARNING THRESHOLDS.
PATCHY FOG HAS FORMED NEAR THE SOUTHERN SASKATCHEWAN/MANITOBA
BORDER. THIS FOG WILL LIFT LATER THIS MORNING. FOG IS EXPECTED TO
RETURN OVER SOUTHERN MANITOBA TONIGHT.
SMOKE FROM FIRES IN BC AND THE PACIFIC NORTHWEST MAY AFFECT
SOUTHERN SASKATCHEWAN AT TIMES OVER THE COMING DAYS AS SOUTHWEST FLOW
ALOFT DEVELOPS ON THE BACKSIDE OF THE UPPER RIDGE.
CONVECTION WILL CONTINUE IN NORTHERN MANITOBA TODAY THROUGH TO THIS
EVENING. SHOWERS AND THUNDERSTORMS WILL FOCUS ALONG THE SURFACE
TROUGH FROM THE GREAT SLAVE LAKE LOW PRESSURE SYSTEM. THUNDERSTORMS
ARE EXPECTED TO REMAIN SUB-SEVERE.
A SECOND AREA OF CONVECTION WILL DEVELOP THIS AFTERNOON IN SOUTHEAST
SASKATCHEWAN, ASSOCIATED WITH THE SURFACE LOW THERE. ADDITIONALLY,
THE SHORTWAVE FROM MONTANA WILL APPROACH THE AREA, PROVIDING EXTRA
LIFT TO TRIGGER AND SUSTAIN THUNDERSTORMS. THESE THUNDERSTORMS WILL
ENTER SOUTHWEST MANITOBA VIA THE SHORTWAVE, BY THE EVENING HOURS.
THERE IS POTENTIAL FOR THESE THUNDERSTORMS TO BECOME SEVERE THIS
AFTERNOON AND EVENING WITH MLCAPE VALUES UP TO 1000 J/KG AND BULK
SHEAR OF 25-30 KNOTS. WITH THE SLACK FLOW ALOFT UNDER THE UPPER
RIDGE, THE LARGEST SEVERE THREAT IS HEAVY RAIN IN SLOW MOVING OR
TRAINING THUNDERSTORMS. LARGE HAIL AND SEVERE WINDS CANNOT BE RULED
OUT EITHER.
THE LOW PRESSURE SYSTEM OVER SOUTHERN SASKATCHEWAN WILL CONTINUE TO
DEVELOP OVER NIGHT SATURDAY. ASSOCIATED SHOWERS AND THUNDERSTORMS
WILL CONTINUE INTO SUNDAY WITH THE LARGEST THREAT BEING HEAVY RAIN.
AS THE UPPER LOW OVER SOUTHERN BC APPROACHES THE PRAIRIES ON SUNDAY,
AN AREA OF UPPER-LEVEL DIFFLUENCE SETS UP OVER SOUTHERN
SASKATCHEWAN. THIS WILL HELP MATERIALIZE A MORE ORGANIZED AREA OF
SHOWERS AND THUNDERSTORMS. MORE INFORMATION ON THIS SYSTEM TO COME.
NT...LOW PRESSURE IS MOVING INTO THE BEAUFORT SEA TONIGHT.
PRESSURES ARE LOW ENOUGH THAT STAGE 1 AND MAYBE 2 FLOODING IS
PROBABLE AT HERSCHEL ISLAND AND WITH A WESTERLY FLOW NEAR 30 KNOTS
ESTABLISHING ITSELF IT SEEMS LIKELY ENOUGH TO REACH STAGE 2 AT HIGH
TIDE, SO A STORM SURGE WARNING HAS BEEN ISSUED. THESE WESTERLIES
COULD ALSO BRING PROBLEMS TO TUKTOYAKTUK SIMILAR WINDS AND
PRESSURE HAVE BROUGHT FLOODING BEFORE BUT CONFIDENCE IS STILL LOW.
NU...AN AREA OF SHOWERS ASSOCIATED WITH THE SHOTWAVE OVER BOOTHIA
PENINSULA WILL AFFECT NORTHERN BAFFIN, BUT NO SIGNIFICANT
ACCUMULATIONS ARE EXPECTED FOR THE COMMUNITIES.
END/BILOUS/WIELKI
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