648
FOCN45 CWWG 281200
SIGNIFICANT WEATHER DISCUSSION ISSUED BY THE PRAIRIE AND ARCTIC STORM
PREDICTION CENTRE OF ENVIRONMENT CANADA AT 7:00 AM CDT FRIDAY AUGUST
28 2026.
ALERTS IN EFFECT...RAINFALL WARNING FOR FAR NORTHWEST ALBERTA AND
FORT PROVIDENCE. AIR QUALITY WARNINGS FOR FORT LIARD, FORT
PROVIDENCE, AND THE FAR NORTHWEST OF ALBERTA. STORM SURGE WARNING FOR
HERSCHEL ISLAND.
SYNOPTIC OVERVIEW...ALOFT TODAY, UPPER TROUGH OVER THE BEAUFORT SEA
EXTENDING SOUTHWARD THROUGH THE YUKON AND THEN THROUGH BC FOLLOWED BY
A SHARP UPPER RIGDE OVER THE PRAIRIES THAT EXTENDS NORTH INTO THE
EASTERN KITIKMEOT AND THEN INTO THE EASTERN ARCTIC ARCHIPELAGO.
AN UPPER LOW SITS IN HUDSON BAY WITH A TROUGH SOUTHWARD THROUGH
ONTARIO AS WELL AS EASTWARD TO ANOTHER UPPER LOW OVER THE LABRADOR
SEA. UPPER RIDGE OVER THE MARITIMES.
AT THE SURFACE, A 998 MB LOW LIES OVER NORTHEASTERN ALBERTA WITH
TROUGHING SOUTHWARD THROUGH SASKATCHEWAN AND NORTHEASTWARD THROUGH
THE KITIKMEOT. A COMPLEX OF LOWS LIE OVER EASTERN HUDSON BAY AND
NORTHERN QUEBEC. HIGH PRESSURE LIES ACROSS THE VICTORIA ISLAND, THE
KIVALLIQ AND BAFFIN ISLAND.
DISCUSSION...
AB/NRN SK...LOW PRESSURE MATURING OVER THE NORTHERNMOST AREAS OF THE
PROVINCE WILL PROVIDE COPIOUS AMOUNTS OF PRECIPITATION TO PARTS OF
IT'S NORTHWEST CORNER. THE RDPS HAS BEEN SHOWING A BIAS TOWARDS A
PRECIPITATION FORECAST THAT IS TOO HEAVY RECENTLY BUT MOST GUIDANCE
DOES SHOW A SWATH OF 50+ MM IN 24 HOURS AND BULLSEYES NEAR 100 MM IN
A 24 HOUR PERIOD ENDING SATURDAY MORNING COVERING SOME PORTION OF
RAINBOW LAKE, HIGH LEVEL AND HIGHWAYS 35 AND 58 IN THE NORTHWEST
CORNER OF THE PROVINCE. THIS IS TRENDING A BIT EASTWARDS, BUT IN THE
SAME FORECAST REGION. A RAINFALL WARNING IS WARRANTED AND THERE'S A
LIGHT RISK OF LOCALLY HIGH IMPACTS FROM THIS SYSTEM HERE.
THERE'S SOME DEBATE AS TO HOW MUCH SMOKE WILL MIX DOWN FROM THE RAIN
AND HOW MUCH WILL SCOUR OUT, BUT FOR NOW AIR QUALITY IN THE NORTHWEST
CORNER OF THE PROVINCE REMAINS POOR TO VERY POOR, AND AN AQ WARNING
IS OUT THERE TOO.
ELSEWHERE, A SHORTWAVE, UPPER LEVEL JET, SOME PERTURBATIONS AT 500
MB, AND SOME TERRAIN EFFECTS WILL COMBINE WITH MODEST
INSTABILITY TO TRIGGER NON-SEVERE THUNDERSTORMS OVER NORTHERN
PORTIONS OF ALBERTA AND SASKATCHEWAN THIS AFTERNOON.
MB/SRN SK...ABOVE SEASONAL TEMPERATURES OVER THE EASTERN PRAIRIES
WILL APPROACH HEAT WARNING CRITERIA THROUGH THE WEEKEND BUT OVERNIGHT
LOWS WILL DIP BELOW WARNING THRESHOLDS.
THR TROUGH FROM THE NORTHEASTERN ALBERTA LOW CONTINUES TO SUPPORT AN
AREA OF SHOWERS AND EMBEDDED NON-SEVERE THUNDERSTORMS EARLY THIS
MORNING. THUNDERSTORMS WILL REINVIGORATE OVER EASTERN SASKATCHEWAN/
WESTERN MANITOBA ON FRIDAY AFTERNOON. UP TO 1500 J/KG MLCAPE COMBINED
WITH 30 KNOTS OF BULK WIND SHEAR MAY SUPPORT A FEW MARGINALLY SEVERE
THUNDERSTORMS ON FRIDAY AFTERNOON OVER EASTERN SASKATCHEWAN BUT CAM
GUIDANCE REMAINDS MURKY IF ANY NEW CONVECTION ACTUALLY DEVELOPS HERE.
FOR NOW, HAVE MAINTAINED A GREY AREA ON THE DAY 1 THUNDERSTORM
OUTLOOK GIVEN UNCERTAINTIES IN NEW DEVELOPMENT AND THE REGION BEING
UNDER THE INFLUENCE OF THE UPPER RIDGE.
SHOWERS AND THUNDERSTORMS WILL PERSIST INTO THE OVERNIGHT HOURS
ACROSS PORTIONS OF CENTRAL AND NORTHERN MANITOBA.
THE SOUTHEASTERN PRAIRIES WILL REMAIN UNSETTLED THROUGH THE WEEKEND
AS THE PARENT UPPER LOW MOVES ONSHORE AND BEGINS TO INFLUENCE THE
EASTERN PRAIRIES.
SMOKE FROM FIRES OVER 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.
NT...LOW PRESSURE WRAPPING UP NEAR THE ALBERTA BORDER IS SET TO BRING
SIGNIFICANT PRECIPITATION WEST OF GREAT SLAVE LAKE. RDPS HAS BEEN
DODGING EASTWARDS THE LAST TWO RUNS, AND SATELLITE AND RADAR OOES
SUGGEST OUR SYSTEM IS FURTHER EAST THAN PREVIOUSLY FORECAST. RAINFALL
APPEARS NOT TO HAVE MATERIALIZED IN A SIGNFICANT WAY IN FORT LIARD
AND FORT SIMPSON, AND WARNINGS HAVE BEEN ENDED AS AN ADDITIONAL 5 TO
10 MM TODAY SHOULD NOT BRING IMPACTS.
FORT PROVIDENCE, THE HAMLET, HAS ALSO UNDERFORMED FORECAST RAINFALL
AMOUNTS BUT A LINE OF TRAINING THUNDERSTORMS HAS BEEN SITTING QS IN
THE FORECAST REGION FOR SEVERAL HOURS, THOUGH NOT OVER ANY
INFRASTRUCTURE.
NEW THINKING IS THAT AN ADDITIONAL 20 TO 45 MM OF RAINFALL WILL FALL
BETWEEN HAY RIVER AND FORT PROVIDENCE OVER THE NEXT 24 HOURS.
A WARNING ISN'T QUITE NEEDED FOR HAY RIVER YET, THOUGH THIS WILL HAVE
TO BE MONITORED. A WARNING REMAINS OUT IN FORT PROVIDENCE.
THE LACK OF RAINFALL TO THE WEST UNFORTUNATELY MEANS FIRES IN THE
AREA WILL CONTINUE BURNING, WITH A NORTHERLY FLOW ADVECTING SMOKE
FROM FORT SIMPSON THOURGH FORT LAIRD. AQ WARNINGS ARE OUT FOR THESE
REGIONS.
MEANWHILE, LOW PRESSURE IS ALSO MOVING INTO THE BEAUFORT SEA.
PRESSURES ARE LOW ENOUGH THAT STAGE 1 AND MAYBE 2 FLOODING IS
PROBABLE OVERNIGHT TONIGHT AT HERSCHEL ISLAND AND WITH A WESTERLY
FLOW NEAR 30 KNOTS ESTABLISHING ITSELF SATURDAY IT SEEMS LIKELY
ENOUGH TO REACH STAGE 2 AT HIGH TIDE THAT AFTERNOON, SO A STORM
SURGE WARNING HAS BEEN ISSUED. THESE WESTERLIES COULD ALSO BRING
PROBLEMS TO TUKTOYAKTUK EVENTUALLY BUT IT'S TOO EARLY TO SAY HERE.
NU...MOISTURE FLOWING NORTH FROM QUEBEC WILL IMPACT COMMUNITIES ON
SOUTHERN BAFFIN ISLAND OVER THE NEXT FEW DAYS WITH KIMMIRUT AND
IQUALIUT POSSIBLY SEEING 15 TO 25 MM OF RAIN BY FRIDAY EVENING.
MODERATE NORTHEASTERLY WINDS OVER CORAL HARBOUR GUSTING UP TO 70 KM/H
EXPECTED TODAY FROM THE LOW IN CENTRAL HUSON BAY.
END/STAMMERS/BATE
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