250
FOCN45 CWWG 171900
SIGNIFICANT WEATHER DISCUSSION ISSUED BY THE PRAIRIE AND ARCTIC STORM
PREDICTION CENTRE OF ENVIRONMENT CANADA AT 2:00 PM CDT THURSDAY JULY
17 2025.
ALERTS IN EFFECT...AIR QUALITY ALERTS FOR PARTS OF ALBERTA,
SASKATCHEWAN, MANITOBA, AND THE NT. HEAT WARNING FOR PARTS OF THE
SOUTHERN NT. SEVERE THUNDERSTORM WATCH FOR PARTS OF THE SW NT AND SE
AB.
SYNOPTIC OVERVIEW...ALOFT, RIDGING IS OVER THE EASTERN PACIFIC AND
ALASKA. A SHORTWAVE IS OVER NORTHERN BC ANOTHER SHORTWAVE IS OVER
SOUTHERN ALBERTA. AN UPPER LOW IS OVER THE HIGH ARCTIC AND ANOTHER
UPPER LOW IS OVER NORTHERN HUDSON BAY.
AT THE SURFACE, A 1014 MB LOW IS OVER THE MACKENZIE. HIGH PRESSURE
STRETCHES FROM THE EASTERN PRAIRIES THROUGH TO THE WESTERN ARCTIC.
A DECAYING 998 MB LOW IS OVER NORTHERN HUDSON BAY.
DISCUSSION...
PRAIRIES...THERE WILL BE A COUPLE OF CONCERNS THIS FORECAST PERIOD.
FIRST, OF COURSE, IS SMOKE. THE MAIN FIRES OF NOTE CONTINUE TO
FUMIGATE DOWNSTREAM REGIONS AND THE AREAS AFFECTED WILL DEPEND ON THE
WINDS. WITH ONE OF THE HIGH CENTRES OVER THE EASTERN PRAIRIES, MOST
OF THE SMOKE WILL LIKELY BE MOVED OFF TO THE EAST. THIS MEANS THAT
SMOKE FROM THE FIRES IN THE BISSETT REGION OF SOUTHERN MANITOBA WILL
PRIMARILY AFFECT THAT REGION AND THEN NORTHWESTERN ONTARIO.
SMOKE FROM THE FIRES IN NORTH-CENTRAL SK AND MB WILL AFFECT A SWATH
ABOUT 200 KM WIDE FROM BUFFALO NARROWS TO ISLAND LAKE, WITH SOME
SMALL VARIATION NORTH AND SOUTH OF THIS SWATH. SMOKE BULLETINS HAVE
BEEN UPDATED TO REFLECT THIS LIKELIHOOD. MOVING FORWARD, A SHIFT TO
MORE SOUTHERLY FLOW WILL BEGIN TO ADVECT THIS SMOKE PLUME NORTH OR
NORTHWESTWARD TOWARD LAKE ATHABASCA AND THE 60TH PARALLEL, POSSIBLY
BEFORE MORNING ON FRIDAY.
THE OTHER CONCERN THIS FORECAST PERIOD IS SEVERE THUNDERSTORMS.
ORGANIZED CONVECTION WILL FORM THIS AFTERNOON IN SOUTHERN ALBERTA AND
MOVE INTO SOUTHWESTERN SASKATCHEWAN THIS EVENING. MLCAPE WILL BE
500-1000 J/KG AND EBWD AROUND 40 KNOTS, LEADING TO PRIMARILY A HAIL
THREAT. CLOSER TO THE UPPER TROUGH AXIS, IN SOUTHEASTERN AB, A FUNNEL
CLOUD THREAT ALSO EXISTS. ALSO IN THE VICINITY OF THIS TROUGH WILL BE
RAINFALL AMOUNTS SURROUNDING THE AREA OF CALGARY, RANGING FROM 15-25
MM TODAY BEFORE THE SYSTEM DEPARTS TONIGHT.
NT...SMOKE CONTINUES TO AFFECT A NUMBER OF COMMUNITIES IN THE NT AND
AIR QUALITY ALERTS REMAIN IN EFFECT TO REFLECT THE MOST IMPACTED
REGIONS.
THUNDERSTORMS ARE ONCE AGAIN FORECAST THROUGH MUCH OF THE WESTERN
NWT. STORMS WILL BE SLOW MOVING AND THERE IS SOME POTENTIAL FOR
LOCALLY HEAVY RAIN AND/OR HAIL. BEST CHANCE FOR SEVERE WEATHER TODAY
FROM ROUGHLY THE LIARD REGION TO FORT SIMPSON, ALTHOUGH TS ARE IN THE
FCST AS FAR NORTH AS WESTERN GREAT BEAR LAKE, AND THEN EAST THROUGH
NORTH SLAVE REGION.
HEAT WARNINGS REMAIN IN EFFECT FOR AREAS SOUTH OF GREAT SLAVE LAKE.
THE COMMUNITIES OF HAY RIVER AND FORT RESOLUTION ARE LIKELY TO BE
SPARED THE WORST OF THE HEAT THANKS TO LAKE BREEZES GENERATED BY
GSL, HOWEVER FURTHER INLAND WILL NOT BE AS FORTUNATE. CONDITIONS
WILL IMPROVE ON SATURDAY. IT REMAINS TO BE SEEN HOW THE WIDESPREAD
FOREST FIRE SMOKE IMPACTS TEMPERATURES THIS AFTERNOON.
NU...THE SYSTEM OVER NORTHERN HUDSON BAY CONTINUES TO DECAY WITH JUST
A FEW SHOWERS LINGERING AROUND BAFFIN ISLAND AND KIVALLIQ. WITH WEAK
FLOW SETTLING OVER THE AREA, REMNANT CLOUD, DRIZZLE, AND FOG WILL BE
THE MAIN ISSUES FOR THE NEXT FEW DAYS.
END/CARLSEN/MOODIE/VAN LOCHEM
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