540
FOCN45 CWWG 041900
SIGNIFICANT WEATHER DISCUSSION ISSUED BY THE PRAIRIE AND ARCTIC STORM
PREDICTION CENTRE OF ENVIRONMENT CANADA AT 2:00 PM CDT THURSDAY JUNE
4 2026.
ALERTS IN EFFECT...SEVERE THUNDERSTORM WATCH FOR PARTS OF SOUTHERN
ALBERTA. AIR QUALITY WARNINGS FOR PARTS OF THE SOUTHERN NWT.
OVERVIEW...ALOFT, AN UPPER LOW IS LOCATED WEST OF HAIDA GWAII WITH AN
UPPER TROUGH EAST-SOUTHEAST THROUGH CENTRAL B.C. AND THROUGH THE
ROCKY MOUNTAINS. AN UPPER RIDGE IS OVER ALBERTA AND SASKATCHEWAN AND
AN UPPER LOW SITS OVER LAKE WINNIPEG. A BROAD UPPER RIDGE IS OVER
ONTARIO AND SOUTHERN QUEBEC. IN THE NORTH, AN UPPER LOW IS OVER THE
HIGH ARCTIC AND A SHORTWAVE TROUGH IS TRACKING THROUGH THE KIVALLIQ
COAST.
AT THE SURFACE, WEAK LOW PRESSURE IS OVER YUKON AND NORTHERN BC.
A RIDGE OF HIGH PRESSURE IS OVER THE NORTHERN ONTARIO AND JAMES BAY
AND EXTENDS WESTWARD THROUGH THE NORTHEASTERN PRAIRIES. AN OCCLUDED
LOW IS OVER SOUTHEASTERN MANITOBA. A LOW IS OVER THE HIGH ARCTIC.
DISCUSSION...
AB/NORTHERN SK...THE SHORTWAVE OVER BC WILL CROSS INTO ALBERTA THIS
AFTERNOON, TRIGGERING SHOWERS AND THUNDERSTORMS ACROSS MUCH OF THE
PROVINCE. WITH THE JET SUPPORT LARGELY FURTHER TO THE WEST,
THUNDERSTORMS WILL GENERALLY BE LACKING IN SHEAR TO ORGANIZE THEM AND
SHOULD REMAIN SUB-SEVERE. HOWEVER, THE HIGHEST CAPE AND SHEAR LINE UP
OVER AN AREA JUST EAST OF CALGARY. SEVERE THUNDERSTORM WATCHES HAVE
BEEN ISSUED FOR THIS AREA, WHERE LARGE HAIL IS POSSIBLE.
THUNDERSTORMS ARE EXPECTED AGAIN FRIDAY IN AN AREA EXTENDING FROM
CENTRAL ALBERTA UP INTO NORTHWESTERN SASKATCHEWAN, ASSOCIATED WITH A
DEVELOPING LOW AND COLD FRONT. MLCAPE VALUES UP TO 1000 J/KG AND UP
TO 40 KT OF EBWD COULD SUPPORT SEVERE STORMS IN THE AREA, THOUGH WITH
SHEAR VECTORS ALIGNED PARALLEL TO THE COLD FRONT, CONVECTION COULD
GROW UPSCALE RELATIVELY QUICKLY.
SOUTHERN SK/MB...THE UPPER LOW OVER LAKE WINNIPEG AND SURFACE LOW
REFLECTION OVER SOUTHEASTERN MANITOBA WILL SLOWLY DRIFT EASTWARD
THROUGH THE DAY AND CONTINUE TO WEAKEN. LINGERING INSTABILITY OVER
MANITOBA AND THE DYNAMIC SUPPORT FROM THE FEATURES WILL LEAD TO
SCATTERED SHOWERS AND THUNDERSTORMS OVER THE PROVINCE THIS AFTERNOON
AND EVENING. THESE STORMS WILL GENERALLY BE WEAK, ALTHOUGH AN
EMBEDDED SEVERE THUNDERSTORM OR TWO CANNOT BE RULED OUT. FURTHER
WEST, SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE OVER PARTS OF
SOUTHWESTERN SASKATCHEWAN AS WELL THAT MAY DRIFT ALONG THE
INTERNATIONAL BORDER, SUPPORTED BY A SHORTWAVE LIFTING NORTHEAST FROM
MONTANA.
PATCHY FOG IS ONCE AGAIN EXPECTED ACROSS SASKATCHEWAN AND MANITOBA
OVERNIGHT TONIGHT AS LOW LEVEL MOISTURE LINGERS OVER THE REGION, AS
WELL AS ANY MOISTURE FUELED BY DAYTIME CONVECTION.
NWT...WILDFIRE SMOKE IS AFFECTING PARTS OF THE SOUTHERN NWT.
SMOKE WILL LIKELY CONTINUE TO DRIFT AROUND SOUTH OF GREAT SLAVE LAKE
UNTIL FRIDAY, WHEN SHOWERS AND THUNDERSTORMS MOVING THROUGH THE AREA
SHOULD HELP DIMINISH THE SMOKE.
SOME PRECIP TYPING ISSUES ARE FORECAST FOR THE NORTHERN NWT WITH A
COLD FRONT SWEEPING DOWN FROM THE ARCTIC OCEAN. RAIN IS FORECAST TO
CHANGE OVER TO SNOW FOR MOST COMMUNITIES IN THE DELTA THIS MORNING AS
TEMPERATURES CONTINUE TO FALL. THERE IS A VERY SLIGHT CHANCE OF
FREEZING RAIN ASSOCIATED WITH THE CHANGEOVER, BUT MOST COMMUNITIES
ARE EXPECTED TO REMAIN JUST ABOVE THE ZERO DEGREE MARK.
NUNAVUT...THE SHORTWAVE CURRENTLY TRACKING THROUGH KIVALLIQ WILL MOVE
THROUGH MELVILLE PENINSULA AND SOUTHERN BAFFIN ISLAND OVERNIGHT AND
THROUGH FRIDAY BRINGING MIXED PRECIPITATION TO THE AREA.
END/COLANGELO/GRIFFITH
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