352
FOCN45 CWWG 291900
SIGNIFICANT WEATHER DISCUSSION ISSUED BY THE PRAIRIE AND ARCTIC STORM
PREDICTION CENTRE OF ENVIRONMENT CANADA AT 2:00 PM 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 WESTERN NWT, A THIRD OVER BOOTHIA PENINSULA, AND A FOURTH OVER
THE ALBERTA/NWT BORDER. ADDITIONALLY, AN UPPER LOW SPINS OVER
SOUTHERN BC 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
SASKATCHEWAN 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 41.8, FORT PROVIDENCE HAD
34.2, WHILE HIGH LEVEL ONLY REPORTED REPORTED 13.1 MM AS THE
MAJORITY OF THE RAIN FELL TO THE NORTHEAST. MOST OF THE RAIN IS NOW
OVER BUT A FURTHER 5 TO 10 MM IS EXPECTED TODAY WITH POSSIBLY UP TO
20 MM IN FORT PROVIDENCE.
THUNDERSTORMS EXPECTED ALONG THE FOOTHILLS TODAY NORTH OF CALGARY.
TO THE SOUTH OF CALGARY, THE BOUNDARY LEVEL IS DRY AND TO THE NORTH
GOOD LEFT EXIT 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 IS SLOWLY DISSIPATING NEAR THE SOUTHERN SASKATCHEWAN/
MANITOBA BORDER. 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. SEASONABLY STRONG MOISTURE RETURN AHEAD OF THE UPPER
LOW WILL YIELD 2000 J/KG MLCAPE ACROSS SOUTHEASTERN SK COMBINED WITH
30 TO 40 KNOTS OF 0-6 KM BULK SHEAR WILL RESULT IN A POTENT LATE
SEASON SEVERE RISK. A FEW SUPERCELLULAR STRUCTURES CAPABLE OF ALL
HAZARDS WILL INITIALLY BE POSSIBLE BUT STRONG FORCING AND MEAN WIND
PROFILES PARALLEL TO THE SURFACE COLD FRONT WILL LIKELY RESULT IN
RAPID UPSCALE GROWTH INTO ONE OR MORE LINEAR CONVECTIVE SYSTEMS.
LINEAR STORMS SLIDE EASTWARD INTO SOUTHERN MANITOBA IN THE EARLY
EVENING HOURS, TRANSITIONING INTO A STRONG WIND AND HEAVY RAINFALL AS
THE PRIMARY THREATS.
IN ADDITION TO THE SEVERE CONVECTION, HEAVY RAIN IS LIKELY OVER
EASTERN SASKATCHEWAN WHERE WIDESPREAD AMOUNTS OF 30 TO 50 MM IS
LIKELY BY MONDAY. LOCALIZED HEAVIER AMOUNTS ARE POSSIBLE, SO RAINFALL
WARNINGS MAY BE REQUIRED AS THE EVENT NEARS. SIGNIFICANT MODEL
DISCREPANCIES AND HEAVY CONVECTIVE BIASES EXIST AT PRESENT TIME SO IT
IS TOO EARLY TO NAIL DOWN AN EXACT AREA, BUT PORTIONS OF EASTERN
SASKATCHEWAN WILL LIKELY SEE SIGNIFICANT RAINFALL FROM THIS SYSTEM.
A SPECIAL WEATHER STATEMENT WILL BE ISSUED THIS AFTERNOON TO
HIGHLIGHT THE HEAVY RAINFALL RISK WITH THIS UPCOMING SYSTEM.
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. WITH A WESTERLY FLOW NEAR 30 KNOTS ESTABLISHING
ITSELF, IT SEEMS LIKELY THAT THE ISLAND WILL REACH STAGE 2 STORM
SURGE LEVELS 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 AS THE TIME OF THE STRONGEST WINDS AND HIGH TIDE DO NOT
COINCIDE. LIKELY SCENARIO FOR TUKTOYAKTUK IS THAT STAGE 1 WILL BE
REACHED, BUT NOT QUITE STAGE TWO, SO FOR NOW CONDITIONS WILL BE
MONITORED CLOSELY.
NU...AN AREA OF SHOWERS ASSOCIATED WITH THE SHORTWAVE OVER BOOTHIA
PENINSULA WILL AFFECT NORTHERN BAFFIN, BUT NO SIGNIFICANT
ACCUMULATIONS ARE EXPECTED FOR THE COMMUNITIES.
END/BILOUS/STAMMERS/ZIOLKOWSKI/GREENHOUGH
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