511
FOCN45 CWWG 031900
SIGNIFICANT WEATHER DISCUSSION ISSUED BY THE PRAIRIE AND ARCTIC STORM
PREDICTION CENTRE OF ENVIRONMENT CANADA AT 2:00 PM CDT SATURDAY JUNE
3 2023.
ALERTS IN EFFECT...SPECIAL AIR QUALITY STATEMENT FOR PARTS OF
NORTHERN SASKATCHEWAN, NORTHERN ALBERTA, AND THE NORTHWEST
TERRITORIES. HEAT WARNINGS FOR SOUTHERN MANITOBA. SEVERE
THUNDERSTORM WATCH FOR SOUTHERN SASKATCHEWAN AND MANITOBA.
SYNOPTIC OVERVIEW...ALOFT, THE DOMINANT FEATURE OVER
MOST OF CANADA IS A SPRAWLING UPPER RIDGE. ANCHORED BY AN UPPER HIGH
CENTRED OVER THE LAKE OF THE WOODS REGION OF ONTARIO, THE UPPER RIDGE
EXTENDS FROM BRITISH COLUMBIA INTO THE SOUTHERN ARCTIC, ACROSS HUDSON
BAY, AND THROUGH MUCH OF QUEBEC AND ONTARIO. FLANKING THE UPPER
RIDGE IN THE WEST, AN UPPER LOW SITS OFF THE BRITISH COLUMBIA
COASTLINE AND A SECONDARY UPPER LOW SITS OVER THE NORTHWESTERN UNITED
STATES. IN THE EAST, A SHARP UPPER TROUGH EXTENDS FROM LABRADOR
SOUTHWARDS TO THE ST. LAWRENCE RIVER VALLEY. IN THE NORTH, UPPER LOWS
SIT OVER THE ARCTIC OCEAN AND BAFFIN BAY WITH WEAK RIDGING IN
RESPONSE.
AT THE SURFACE, A 1014 MB LOW SITS OFF THE BRITISH COLUMBIA COAST. TO
ITS EAST, A COLD FRONT SWEEPS NORTHWARDS ALONG THE COAST INTO THE
WESTERN ARCTIC; IT THEN TURNS SOUTHEASTWARDS THROUGH THE KIVALLIQ TO
THE SOUTHWESTERN HUDSON BAY COAST THEN TURNS EASTWARDS THROUGH
QUEBEC. BACK IN THE SOUTH, A 1011 MB LOW SITS OVER MONTANA, WITH A
COLD FRONT SOUTHWARDS AND A WARM FRON THAT LIFTS NORTHWARDS NEAR THE
AB/SK BORDER, CURLING NORTHEASTWARDS ACROSS THE CENTRAL PRAIRIES THEN
TURNING SHARPLY SOUTHWARDS TO THE GREAT LAKES FROM NORTHERN MANITOBA.
A 1035 MB HIGH SITS OVER NORTHERN QUEBEC AND LABRADOR.
DISCUSSION...
PRAIRIES...HOT AND HUMID CONDITIONS WILL LEAD TO ANOTHER DAY WITH
SEVERE THUNDERSTORM POTENTIAL OVER PORTIONS OF SASKATCHEWAN AND
MANITOBA. THE GENERAL THERMODYNAMIC ENVIRONMENT IS SIMILAR TO THE
LAST FEW WITH A BROAD AREA OF 1000 TO 1500 J/KG OF MLCAPE IN PORTIONS
OF SOUTHERN SASKATCHEWAN AND SOUTHERN MANITOBA. BULK SHEAR VALUES
RANGE FROM 15 TO 30 KNOTS IN SOUTHERN SASKATCHEWAN DOWN TO ALMOST
NOTHING IN SOUTHERN MANITOBA. FORCING IS WEAK TODAY, THOUGH, DRIVEN
MAINLY BY A SURFACE LOW MOVING INTO SOUTH-CENTRAL SASKATCHEWAN, ITS
NORTHWARDS TROUGH, AND A SHORTWAVE PUSHING INTO THE SAME REGION.
EXPECT TO SEE MORE ORGANIZED CONVECTION WITH A RISK OF ISOLATED
SEVERE THUNDERSTORMS IN SOUTHERN SASKATCHEWAN AND A LESSER RISK OF
SEVERE ON THE MANITOBA SIDE OF THE BORDER. WITH BETTER SHEAR AND
ORGANIZATION ON THE SASKATCHEWAN SIDE, THE PRIMARY THREAT WILL
LARGELY BE FOR DAMAGING HAIL; IN MANITOBA, STORM MOTION WILL QUICKLY
DIMINISH DUE TO THE LACK OF SHEAR, AND WHEN COMBINED WITH THE VERY
HOT AND HUMID AIR MASS IN PLACE, TORRENTIAL RAINFALL WILL BE THE
PRIMARY CONCERN WITH ANY THUNDERSTORMS THAT DEVELOP.
HEADING INTO THE NIGHT, AN AREA OF ELEVATED MUCAPE VALUES IN EXCESS
OF 500 J/KG WILL SHIFT NORTHWARDS WITH THE STRENGTHENING LLJ. THE
INSTABILITY COMBINED WITH ISENTROPIC ASCENT AS THE WARMER AIR MASS IS
LIFTED NORTHWARDS WILL LIKELY CONTINUE TO SUPPORT SHOWERS AND
THUNDERSTORMS NORTHWARDS INTO THE NIGHT, THOUGH THE SEVERE THREAT
WILL LIKELY DIMINISH AFTER SUNSET.
IN ALBERTA, THUNDERSTORMS WILL DEVELOP ON THE CENTRAL FOOTHILLS AND
NORTHWARD THIS AFTERNOON. CAPE VALUES ARE NOT AS IMPRESSIVE AS IN SK
AND MB, WITH MLCAPE LESS THAN 750 J/KG. IN THESE THREAT
AREAS, IT IS POSSIBLE THAT EFFECTIVE SHEAR IS TOO STRONG TO DEVELOP
ORGANIZED STORMS. HOWEVER, HIGH BASED CONVECTION COULD LEAD TO SOME
STRONG WINDS.
HEAT WARNINGS CONTINUE FOR SOUTHERN MANITOBA TODAY WITH LITTLE CHANGE
IN THE FORECAST. DAYTIME HIGHS WILL CLIMB INTO THE 30S IN A HOT AND
HUMID AIR MASS OVER THE REGION. THE EXTREME HEAT WILL LIKELY SHIFT
NORTHWESTWARDS LATER THIS WEEKEND. EXTREME HEAT WARNINGS WILL EXPAND
AS REQUIRED IN THE DAYS AHEAD.
SMOKE CONTINUES TO IMPACT MOST OF NORTHERN ALBERTA AND PARTS OF
NORTHERN SASKATCHEWAN. HEAVY RAIN OVER NORTHWESTERN SASKATCHEWAN
OVER THE PAST 24-36 HOURS HAS DAMPENED THE FIRES IN THE AREA
SOMEWHAT, THOUGH PLENTY OF SMOKE REMAINS OVER NORTHERN ALBERTA.
LOW-LEVEL EASTERLY/NORTHEASTERLY HAS PUSHED SMOKE OVER CENTRAL
ALBERTA OVERNIGHT, BUT VALUES OF PM2.5 REMAIN MODERATE. IT IS
ANTICIPATED THAT AS THE NOCTURNAL INVERSION ERODES OVER THE AREA,
CONCENTRATIONS OF PM2.5 WILL DECREASE LATER THIS MORNING.
NWT...AIR QUALITY AND LOCAL VISIBILITIES CONTINUE TO BE POOR DUE TO
SMOKE AROUND GREAT SLAVE LAKE AND FOR PORTIONS OF THE MACKENZIE
RIVER TODAY. CONDITIONS WILL GRADUALLY IMPROVE OVER EASTERN PORTIONS
OF THE NT THROUGHOUT THE FORECAST PERIOD AS WINDS ALOFT SHIFT THE
PLUME TO THE WEST, BUT HAZY SKIES AND POOR AIR QUALITY WILL CONTINUE
TO AFFECT THE REST OF REGION FOR THE FORESEEABLE FUTURE.
NUNAVUT...LIGHT TO MODERATE SNOW WILL DRIFT SOUTHWARDS ALONG BAFFIN
ISLAND'S EASTERN COAST TODAY, SUPPORTED BY ONSHORE FLOW COUPLED WITH
A PASSING SHORTWAVE. ACCUMULATIONS WILL LARGELY BE TIED TO THE HIGHER
COSTAL TERRAIN, BUT A COUPLE CENTIMETRES WILL BE POSSIBLE IN THE
COASTAL COMMUNITIES. HEADING INTO THE NEXT COUPLE DAYS, SOME FLURRIES
WILL BE POSSIBLE ACROSS MUCH OF BAFFIN ISLAND AS ANOTHER SHORTWAVE
DRIFTS SOUTHWARDS OVER THE ISLAND.
END/WPG/MARK
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