951
FOCN45 CWWG 121900
SIGNIFICANT WEATHER DISCUSSION ISSUED BY THE PRAIRIE AND ARCTIC STORM
PREDICTION CENTRE OF ENVIRONMENT CANADA AT 2:00 PM CDT TUESDAY AUGUST
12 2025.
ALERTS IN EFFECT...AIR QUALITY WARNINGS AND STATEMENTS FOR PORTIONS
OF MANITOBA AND SASKATCHEWAN. SEVERE THUNDERSTORM WATCHES FOR
CENTRAL AND EAST CENTRAL ALBERTA.
SYNOPTIC OVERVIEW...
ALOFT, UPPER AIR ANALYSIS ALONG WITH GOES WATER VAPOUR IMAGERY SHOWS
BROAD TROUGHING CENTERED OVER MANITOBA THIS MORNING BOUNDED BY
RIDGING TO THE EAST AND WEST OF THE TROUGH. THIS RIDGE TROUGH PATTERN
LEADS TO NORTHWESTERLY FLOW OVER THE WESTERN PRAIRIES. FURTHER NORTH,
AN UPPER LOW IS ANCHORED OVER BAFFIN BAY WITH A TROUGH EXTENDING
SOUTH INTO THE KIVALLIQ. RIDGING EXISTS BACK TO THE WEST OF THE LOW
OVER THE SW NWT.
AT THE SURFACE, A 1007 MB LOW SITS OVER NW AB WITH WARM FRONT INTO SW
SK. A FRONTAL WAVE SITS OVER NORTHWESTERN ONTARIO WITH A 992 MB LOW
ATTACHED ALONG THE HUDSON BAY COASTLINE EAST OF YORK FACTORY.
A BAROCLINIC ZONE SNAKES ALONG THE 60TH PARALLEL FROM HUDSON STRAIT,
INTO THE KIVALLIQ BEFORE TURNING SHARPLY NORTH INTO THE ARCTIC OCEAN.
A BROAD AREA OF HIGH PRESSURE DOMINATES THE PACIFIC NORTHWEST.
DISCUSSION...
AB/NT...THE LOW WILL VERY SLOWLY MAKE IT'S WAY EAST THROUGH THE WEEK.
ALONG THE WARM FRONT AND TROWAL UP TO 25 MM OF RAIN IS EXPECTED
TODAY. PRECIPITATION WILL BECOME MORE SPOTTY TONIGHT BEFORE
REORGANIZING ITSELF TOMORROW AS THE COLD FRONT MOVES ACROSS ALBERTA.
DUE TO THE CONVECTION, CONFIDENCE IN AMOUNTS IS LOW FOR WEDNESDAY BUT
10-20 MM IS POSSIBLE FOR AREAS FROM JASPER TO COLD LAKE. STRONG WINDS
ARE ALSO EXPECTED WITH THE COLD FRONT. MUCH OF CENTRAL AB COULD SEE
NORTHERLY GUSTS OF 60-70 KM/H WEDNESDAY AFTERNOON/EVENING.
WARM TEMPERATURES AND MODERATE DEWPOINTS WILL ALLOW FOR MLCAPE VALUES
OF 500-1200 J/KG THIS AFTERNOON OVER CENTRAL AB. WITH THE WESTERLY
H500 JET AROUND 40 KT THERE WILL BE ENOUGH SHEAR TO POTENTIALLY HAVE
SEVERE THUNDERSTORMS DEVELOP. HOWEVER, WITH THE UPPER RIDGE SITTING
OVER SOUTHERN AB THINGS MAY REMAIN CAPPED UNTIL LATER THIS AFTERNOON
OR INTO THE EARLY EVENING. ONE COMPLICATION FACTOR IS THAT THE LOW
OVER NORTHERN ALBERTA IS PROGRESSING FASTER THAN THE MODELS HAVE
PREDICTED SO THIS WILL IMPACT THUNDERSTORM DEVELOPMENT THIS
AFTERNOON, LIKELY ALLOWING STORMS TO INITIATE A BIT SOONER THAN THE
MODELS HAVE INDICATED. THE TIMING OF THE THUNDERSTORM DEVELOPMENT
WILL BE CRITICAL TO THE SEVERITY OF THE STORMS THAT ARE EXPECTED.
SEVERE THUNDERSTORM WATCHES HAVE BEEN ISSUED TO COVER THE POTENTIAL
THUNDERSTORM DEVELOPMENT THIS AFTERNOON. SEVERE THUNDERSTORMS LOOK
MORE PLAUSIBLE ON WEDNESDAY ALONG AND AHEAD OF THE COLD FRONT WITH
HIGHER MLCAPE VALUES OF 1000-2000 J/KG AND 40 KT EBWD.
MB...SETTLED WEATHER HAS SET IN TODAY AS THE LOW PRESSURE SYSTEM THAT
PASSED THROUGH YESTERDAY HAS EXITED INTO ONTARIO. ANOTHER PUSH OF
SMOKE HAS MADE ITS WAY SOUTH AGAIN TODAY IN THE NORTHWESTERLY FLOW.
A LARGE SMOKE OF PLUME IS EVIDENT ON SATELLITE IMAGERY IN
SOUTHEASTERN MANITOBA ALONG EDGES AND THROUGH BREAKS IN THE CLOUD AND
THEREFORE AIR QUALITY STATEMENTS HAVE BEEN EXPANDED. IT IS FORECAST
TO EXIT QUICKLY EAST INTO ONTARIO LATER THIS AFTERNOON WHEN
CONDITIONS WILL BEGIN TO IMPROVE FROM NORTH TO SOUTH WHICH SHOULD
PROMPT AN END TO THE AIR QUALITY ALERTS. WINDS WILL BEGIN TO SETTLE
AS A RIDGE OF HIGH PRESSURE MOVES INTO NORTHERN MANITOBA CAUSING THE
WINDS TO TURN EASTLY AND CONFINING THE SMOKE IN NORTHERN MANITOBA
FOR THE NEXT FEW DAYS.
SK..QUIET WEATHER IS ONTAP FOR MOST OF THE PROVINCE TODAY WITH ONLY A
FEW THINGS TO NOTE. THE FIRST THING IS THE AFOREMENTIONED SMOKE PLUME
WILL CLIP PORTIONS OF SOUTH EASTERN SASKATCHEWAN THIS MORNING, MAINLY
THE HUDSON BAY AND KAMSACK REGIONS. SMOKE WILL BEGIN TO TAPER OFF IN
THE AFTERNOON HOWEVER AS THE RIDGE SLIDES IN AND WINDS TAPER OFF.
IN NORTHEASTERN SK SMOKE IS STILL CAUSING VERY POOR AIR QUALITY AT
TIMES AND WITH WINDS SHIFTING TO BLOW FROM THE EAST THROUGH THE DAY,
THE WARNINGS MAY NEED TO BE EXPANDED TO THE WEST. HOWEVER, INCOMING
SHOWERS FROM THE WEST MAY LIMIT HOW BAD THE SMOKE IS AWAY FROM THE
FIRES. RAINFALL AMOUNTS STARTING ON WEDNESDAY COULD BE LOCALLY AROUND
25 MM FOR THE DAY BUT WITH THE CONVECTION AROUND THE LOW, CONFIDENCE
IS MINIMAL THIS FAR IN ADVANCE OF HOW MUCH WILL ACTUALLY FALL.
REGARDLESS, SHOWERY CONDITIONS THROUGH THE REST OF THE WEEK LOOK
LIKELY AND WILL SURELY BE A RELIEF. A WIDESPREAD AREA OF 25 MM ACROSS
NORTHERN SK BY FRIDAY MORNING LOOKS REASONABLE, WITH SOME AREAS
GETTING MORE THAN THAT.
SOME NON-SEVERE THUNDERSTORMS ARE ALSO EXPECTED TO DRIFT IN FROM
ALBERTA THIS EVENING. SOME OF THESE STORMS COULD BRING SOME LOCALLY
HIGHER PRECIPITATION AMOUNTS TO SOME REGIONS.
A MORE SIGNIFICANT SYSTEM WILL BEGIN TO MAKE ITS WAY INTO SOUTH
CENTRAL SASKATCHEWAN WEDNESDAY, USHERING IN A RETURN OF SEVERE
THUNDERSTORMS. BOTH CAPE AND SHEAR PROFILES SUPPORT THE FORMATION OF
SUPERCELLS OVER PARTS OF SOUTHERN SASKATCHEWAN, PARTICULARLY OVER THE
KINDERSLEY TO MEADOW LAKE AREA WEDNESDAY AFTERNOON. SUPERCELLS THAT
INITIATE CLOSEST TO THE LOW NEAR THE WARM FRONT HAVE THE POTENTIAL TO
PRODUCE TORNADOES. CAPPING APPEARS TO BE A POTENTIAL INHIBITOR OF
WIDESPREAD CONVECTION AT THIS TIME, ESPECIALLY FURTHER SOUTH CLOSER
TO THE US BORDER AND MAY LIMIT OVER ALL STORM COVERAGE. IF INITIATION
OVER COMES THE CAP EARLIER (IN THE AFTERNOON), DISCRETE SUPERCELLS
ARE MORE LIKELY. EVOLUTION INTO THE EVENING IS EXPECTED TO LEAD TO
UPSCALE GROWTH INTO A SQUALL LINE WITH BOWING SEGMENTS. ALL
THUNDERSTORM HAZARDS ARE POSSIBLE INCLUDING SEVERE HAIL UP TO
6 CM, WIND GUSTS OF 110 KM/H AND HEAVY RAINFALL OF 50-75 MM/HR.
NU...NIL SIG WX.
END/ZIOLKOWSKI/DYCK/ROMBOUGH/GREENHOUGH
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page