877  
FOCN45 CWWG 071200  
SIGNIFICANT WEATHER DISCUSSION ISSUED BY THE PRAIRIE AND ARCTIC STORM  
PREDICTION CENTRE OF ENVIRONMENT CANADA AT 7:00 AM CDT MONDAY JULY  
7 2025.  
 
ALERTS IN EFFECT...AIR QUALITY ALERTS FOR PARTS OF CENTRAL  
SASKATCHEWAN, PARTS OF THE NORTHWEST TERRITORIES, AND MOST OF  
MANITOBA. FOG ADVISORY FOR PORTIONS OF EASTERN ALBERTA AND  
SOUTHWESTERN SASKATCHEWAN.  
 
SYNOPTIC OVERVIEW...ALOFT THIS MORNING, GENERALLY WESTERLY FLOW OVER  
THE PRAIRIES SAVE FOR A POTENT SHORTWAVE AND SOUTHWARD TROUGH NEAR  
WYNYARD, SK, MAKING ITS WAY EASTWARD. TO THE NORTH, LARGE LOWS SIT  
OVER EASTERN BAFFIN ISLAND AND THE GULF OF ALASKA WITH WEAK RIDGING  
COVERING MOST OF THE MAINLAND ARCTIC.  
 
AT THE SURFACE, VERY SLACK FLOW AND GENERALLY WEAK RIDGING IN ALL  
DIRECTIONS OVER THE PRAIRIES SAVE FOR A NORTH TO SOUTH TROUGH OVER  
SOUTHEASTERN SK INTO MONTANA. A 982 MB OCCLUDED LOW SITS AT THE  
ENTRANCE TO DAVIS STRAIT AND IS SLOWLY DECAYING.  
 
DISCUSSION...  
 
AB...FOG PATCHES DEVELOPED ALONG THE ALBERTA/SASKATCHEWAN BORDER LAST  
NIGHT, AND WERE DEEMED PERSISTANT ENOUGH TO WARRANT A FOG ADVISORY.  
THIS FOG SHOULD LIFT SHORTLY AFTER SUNRISE.  
 
OTHERWISE A GENERALLY QUIET DAY OF WEATHER IS IN STORE FOR MOST OF  
ALBERTA, THE NOTABLE EXCEPTION BEING IN THE NORTH, WHERE AHEAD OF A  
THERMAL RIDGE UP TO 750 J/KG OF MLCAPE, SURFACE HEATING, AND A WEAK  
SHORTWAVE AS WELL AS A LOCATION IN THE LEFT EXIT OF A 250 MB JET  
SHOULD ALLOW FOR THE DEVELOPMENT OF A FEW THUNDERSTORMS TODAY.  
 
SK/MB...THE SURFACE AND SHORTWAVE TROUGH SHIFTING INTO SOUTHEASTERN  
SK WILL AGAIN BE THE FOCUS FOR THUNDERSTORM ACTIVITY TODAY. THE BULK  
OF THE INSTABILITY AND BETTER SHEAR ARE SLIPPING INTO NORTH DAKOTA,  
WITH JUST THE SOUTHWESTERN CORNER OF MANITOBA - SOUTH OF THE THE  
TRANS-CANADA HIGHWAY - LOOKING AT ANOTHER MARGINAL HAIL AND WIND RISK  
FOR THE AFTERNOON. STORM MOTIONS MAY CARRY ACTIVITY EASTWARD FOR  
AREAS NEAR THE INTERNATIONAL BORDER THROUGH THE EVENING.  
 
THOUGH THERE'S NOT A WHOLE LOT OF INSTABILITY LEFT ALONG MOST OF THE  
TROUGH, THERE'S EXCELLENT LOW LEVEL CONVERGENCE AND VORTICITY BOTH  
BACK WESTWARD FROM THE MANITOBA BORDER THROUGH SOUTHEASTERN SK AND UP  
THROUGH THE HIGHWAY 11 CORRIDOR. FUNNEL CLOUD ACTIVITY IS A DISTINCT  
LIKELIHOOD LATE MORNING AND THROUGH THE AFTERNOON - THE SHORTWAVE HAS  
REMAINED QUITE PROMINENT THROUGH LAST NIGHT, EASILY VISIBLE ON BOTH  
RADAR AND SATELLITE WITH A CLEAR CENTRAL AREA FOR DAYTIME HEATING  
LATER TODAY.  
 
THE STAGNANT SURFACE FLOW, CLEAR SKIES, AND EXTRA MOISTURE LEFT IN  
THE WAKE OF THE DISTURBANCE IS RESULTING IN A FAIR AMOUNT OF DENSE  
FOG OVER SOUTHWESTERN SK THIS MORNING. CONDITIONS FOR WIDESPREAD FOG  
LOOK EVEN BETTER TONIGHT FOR SOUTHEASTERN SK AND WESTMAN.  
 
SMOKE FROM WILDFIRES WILL CONTINUE TO CAUSE POOR AIR QUALITY VALUES  
THROUGH PARTS OF MANITOBA AND NORTH-CENTRAL SASKATCHEWAN. THE SLACK  
FLOW IS MAKING CLEARING TIMES TRICKY FOR LONG-STALLED, NARROW BANDS  
OF DENSER SMOKE NEAR THE SURFACE - NEARLY INVISIBLE ON SATELLITE.  
SURFACE WINDS START TO TURN STRONGLY SOUTHWARD TUESDAY IN  
SASKATCHEWAN AND WEDNESDAY IN MANITOBA.  
 
NT...SMOKE FROM WILDFIRES NEAR WHATI AND SOUTHEAST OF YELLOWKNIFE IS  
BEING ADVECTED NORTHWARDS AND NORTHWESTWARDS IN THE SOUTH TO  
SOUTHEASTERLY FLOW, REDUCING AIR QUALITY IN THESE REGIONS.  
AIR QUALITY WILL LIKELY BE AT LEAST MODERATELY POOR FOR PARTS OF THE  
NORTH SLAVE REGION FOR THE NEXT 36 HOURS, THOUGH CONDITIONS MAY  
IMPROVE LATER THIS MORNING IN YELLOWKNIFE AS THE FLOW IS EXPECTED TO  
BECOME MORE SOUTHERLY OVER THE FIRE LOCATED TO THE SOUTHEAST OF THE  
CITY. A FIRE IS ALSO NOTED VERY NEAR FORT MACPHERSON. THOUGH THERE'S  
NO SURFACE OBSERVATIONS IN THE AREA, ENOUGH SMOKE WAS SWIRLING AROUND  
ON VISIBLE SATELLITE TO ISSUE A SAQS FOR THE REGION LAST NIGHT.  
 
OTHERWISE, SURFACE TROUGHING AND MODERATE INSTABILITY SHOULD ALLOW  
FOR THUNDERSTORMS TO DEVELOP ONCE AGAIN THIS AFTERNOON FOR MANY AREAS  
OVER THE MACKENZIE RIVER. A SHORTWAVE LOCATED WEST OF GREAT SLAVE  
LAKE HAS PRODUCED LIGHTNING THROUGH MOST OF THE NIGHT AND IS ENOUGH  
OF A TRIGGER TO INTRODUCE A RISK OF THUNDERSTORMS FOR THE YELLOWKNIFE  
REGION THIS AFTERNOON.  
 
NU...A SYSTEM SPINNING OVER ELLESMERE ISLAND SHOULD PROVIDE SCATTERED  
FLURRIES AND A RISK OF FREEZING DRIZZLE FOR PARTS OF THE HIGH ARCTIC  
TODAY, AS HAS BEEN OBSERVED AT TIMES LAST NIGHT.  
 
END/KNIGHT/BATE  
 
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