171  
FOCN45 CWWG 291200  
SIGNIFICANT WEATHER DISCUSSION ISSUED BY THE PRAIRIE AND ARCTIC STORM  
PREDICTION CENTRE OF ENVIRONMENT CANADA AT 7:00 AM CDT THURSDAY JULY  
29 2021.  
 
ALERTS IN EFFECT...SPECIAL AIR QUALITY STATEMENTS FOR SOUTHWESTERN  
REGIONS OF ALBERTA, PORTIONS OF MANITOBA AND EAST-CENTRAL  
SASKATCHEWAN. HEAT WARNINGS IN EASTERN AND CENTRAL ALBERTA, AS WELL  
AS THE FORT LIARD REGION.  
 
SYNOPTIC OVERVIEW...THE 00Z UPPER ANALYSES REVEALED A LOW OVER THE  
CENTRAL ARCTIC AND A LOW OFF THE WEST COAST. A BROAD RIDGE SAT OVER  
WESTERN CANADA. THE SURFACE ANALYSIS SHOWS A LOW OVER THE CENTRAL  
ARCTIC AND A LOW/TROUGH COMPLEX FROM SANIRAJAK TO JAMES BAY.  
HIGH PRESSURE WAS OVER SOUTHWESTERN MANITOBA.  
 
DISCUSSION...  
 
EASTERN PRAIRIES...NUMEROUS FOREST FIRES RAGE ON OVER PORTIONS OF THE  
EASTERN PRAIRIES. SMOKE FROM THESE FIRES CONTINUES TO DEGRADE THE AIR  
QUALITY AND REDUCE VISIBILITIES. SPECIAL AIR QUALITY STATEMENTS  
REMAIN IN EFFECT FOR REGIONS NEAR THE FIRES EAST OF LAKE WINNIPEG,  
GRAND RAPIDS, MB, AND HUDSON BAY, SK.  
 
SEVERE THUNDERSTORMS ARE MARGINALLY POSSIBLE TODAY IN PARTS OF  
WESTERN SASKTCHEWAN. MLCAPE AROUND 1000 J/KG AND BULK SHEAR AROUND 25  
KNOTS WOULD NORMALLY PRECLUDE SEVERE WEATHER, BUT A RELATIVELY DRY  
BOUNDARY LAYER WILL PROMOTE HIGH-BASED STORMS. WIND GUSTS IN EXCESS  
OF 90 KM/H WOULD BE THE MAIN THREAT.  
 
WESTERN PRAIRIES...WARM TEMPERATURES HAVE RETURNED TO ALBERTA, AND  
HEAT WARNINGS HAVE BEEN EXPANDED TO INCLUDE MUCH OF EASTERN AND AND  
CENTRAL PARTS OF THE PROVINCE. WARNINGS WILL LIKELY BE EXPANDED  
FURTHER OVER THE COMING DAYS AS THE RIDGE CONTINUES TO BUILD.  
 
SMOKE FROM WILDFIRES IN BC CONTINUES TO AFFECT PORTIONS OF  
SOUTHWESTERN ALBERTA; MAINLY THE MOUNTAINOUS REGIONS DIRECTLY  
DOWNWIND OF THE FIRES. A SPECIAL AIR QUALITY STATEMENT REMAINS IN  
PLACE FOR BANFF, KANANASKIS AND NORDEGG THIS MORNING.  
 
THUNDERSTORMS CURRENTLY TRACKING EASTWARD THROUGH CENTRAL ALBERTA  
COULD PERSIST INTO THE AFTERNOON. THIS AFTERNOON, THUNDERSTORMS ARE  
EXPECTED TO DEVELOP ALONG THE FOOTHILLS. THE GREATEST POTENTIAL FOR  
SEVERE STORMS IS AGAIN IN THE NORTHERN FOOTHILLS WHERE THE EDSON AND  
ROCKY MOUNTAIN HOUSE REGIONS INTERSECT. WITH MIXED LAYER CAPE VALUES  
AROUND 1500 J/KG AND 30 OR SO KNOTS OF BULK SHEAR, MARGINALLY SEVERE  
HAIL WOULD BE THE MAIN HAZARD. HOWEVER, AS THE RIDGE BUILDS OVER  
ALBERTA AND SMOKE CONTINUES TO STREAM OVER THE MOUNTAINS FROM BC, A  
THICKENING SMOKE CEILING COULD INHIBIT THUNDERSTORM INITIATION.  
 
NWT...SHOWERS WITH EMBEDDED NON-SEVERE THUNDERSTORMS ALONG A TROUGH  
OF LOW PRESSURE WILL TRACK ACROSS THE GREAT SLAVE LAKE AREA TODAY  
BEFORE MOVING SOUTHEASTWARD OUT OF THE REGION.  
 
A HEAT WARNING IS IN EFFECT FOR THE FORT LIARD REGION.  
 
ARCTIC...THE BOOTHIA LOW IN THE ARCTIC IS FILLING AND WEAKENING,  
WHILE THE HUDSON BAY LOW WILL DELIVER ANOTHER ROUND OF SHOWERS AND  
FOG TO COASTAL SITES IN THE EAST TODAY.  
 
END/CARLSEN/GRIFFITH  
 
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