047
FOCN45 CWWG 141900
SIGNIFICANT WEATHER DISCUSSION ISSUED BY THE PRAIRIE AND ARCTIC STORM
PREDICTION CENTRE OF ENVIRONMENT CANADA AT 2:00 PM CDT SUNDAY
SEPTEMBER 14 2025.
ALERTS IN EFFECT...AIR QUALITY ALERTS FOR PARTS OF THE NORTHWEST
TERRITORIES, NORTHERN ALBERTA, AND NORTHERN SASKATCHEWAN.
SYNOPTIC OVERVIEW...ALOFT, AN UPPER LOW SITS OVER SOUTHERN ALBERTA
WITH A TROUGH SOUTHWARD INTO THE WESTERN US LEAVING THE EASTERN
PRAIRIES IN AN ACTIVE SOUTHERLY UPPER FLOW WITH SEVERAL SHORTWAVES
EMBEDDED. AN UPPER RIDGE LIES OVER THE US MIDWEST AND EXTENDS
NORTHWARD INTO EASTERN MANITOBA AND THROUGH TO SOUTHERN BAFFIN
ISLAND. AN UPPER LOW IS OVER NORTHERN GREENLAND WITH A TROUGH
SOUTHWARD THROUGH THE ARCTIC ISLANDS. ANOTHER UPPER LOW IS OVER THE
LABRADOR SEA WITH A TROUGH SOUTHWARD THROUGH EASTERN CANADA.
AT THE SURFACE, A RIDGE OF HIGH PRESSURE EXTENDS FROM THE ARCTIC
OCEAN SOUTHWARD TO NWT. A 1000 MB LOW IS NEAR TALOYOAK WITH A WARM
FRONT SOUTHEASTWARD THROUGH FOXE BASIN. THE COLD FRONT EXTENDS
SOUTHWEST INTO NORTHERN ALBERTA AND CONNECTS TO A 1004 MB LOW OVER
CENTRAL BC. A 1023 MB HIGH PRESSURE CENTER IS OVER NORTHERN ONTARIO
AND A RIDGE AXIS WESTWARD EXTENDS INTO MANITOBA AND NORTHERN
SASKATCHEWAN. ANOTHER RIDGE AXIS EXTENDS NORTHWARD THROUGH SOUTHERN
BAFFIN ISLAND.
DISCUSSION...
AB...AN UPPER LOW MOVES NORTHWARDS TO APPROACH FORT MCMURRAY MUCH OF
THE PROVINCE COULD BECOME UNSTABLE WITH A CHANCE OF NON-SEVERE
THUNDERSTORMS FOCUSED NEAR THE LOW AND OVER THE FOOTHILLS. THERE'S A
COMBINDATION OF SHEAR AND INSTABILITY IN THE HINTON AND GRANDE
PRAIRIE REGION THAT IS MILDLY CONCERNING BUT OUR ASSESSMENT IS THAT
INSTABILITY IN THIS REGION WILL MOST LIKELY REMAIN CAPPED TODAY.
WILDFIRE SMOKE CONTINUES TO PLAGUE SEVERAL AREAS. A WILDFIRE IN THE
RED EARTH REGION CONTINUES TO REDUCE AIR QUALITY LOCALLY.
DENSE WILDFIRE SMOKE IS NOTED OVER FIRES NEAR BUFFALO NARROWS, SK,
AND HAS ADVECTED INTO PORTIONS OF NORTHEASTERN ALBERTA. OVER A NARROW
SWATH CENTRED RIGHT OVER FORT MCMURRAY, AIR QUALITY HAS BEEN VERY
POOR AND AN AIR QUALITY WARNING WAS ISSUED HERE THIS MORNING.
SMOKE FROM A FIRE NORTH NORTHWEST OF FORT CHIPEWYAN HAD LED TO VERY
POOR AIR QUALITY IN FORT SMITH. AIR QUALITY IN THAT COMMUNITY HAS
IMPROVED SOMEWHAT AS AN EASTERLY FLOW IS ATTEMPTING TO ESTABLISH
ITSELF BUT MAY BE WORSE CLOSER TO THE FIRE, ACCORDING TO FIREWORK
GUIDANCE, SO THE AQW CONTINUES IN THESE REGIONS.
SK/MB...AN ACTIVE CONVECTIVE PATTERN CONTINUES. SEVERAL SHORTWAVES
EMBEDDED IN THE SOUTHERLY UPPER FLOW WILL TRACK NORTHWARD OVER THE
COMING DAYS LEADING TO ROUNDS OF CONVECTIVE SHOWERS AND EMBEDDED
THUNDERSTORMS THROUGH SASKATCHEWAN AND MANITOBA. FOR TODAY'S
CONVECTIVE SET-UP, SOUTHERLY FLOW CONTINUES TO ADVECT SEASONABLY
WARM, MOIST AIR TO THE PRAIRIES, CREATING A BUOYANT AIRMASS OVER THE
AREA. A BLANKET OF STRATUS/FOG ENCOMPASSED MUCH OF SOUTHEASTERN
SASKATCHEWAN AND SOUTHWESTERN MANITOBA EARLY THIS MORNING, EVIDENCE
OF THE RICH BOUNDARY LAYER MOISTURE IN PLACE. WITH THE FOG CONTINUING
TO LIFT AND DISSIPATE LATE THIS MORNING, DAYTIME HEATING (PENDING
CLOUD COVER) WILL CONTINUE TO DESTABILIZE THE AIRMASS THROUGH THE
AFTERNOON. MODEL GUIDANCE IS INDICATING A THUNDERSTORM ENVIRONMENT
CHARACTERIZED BY 1000+ J/KG OF MLCAPE AND 30 KTS OF BWD OVER SOUTHERN
MANITOBA TODAY. AN UPPER IMPULSE OVER THE DAKOTAS WILL TRACK TOWARDS
SOUTHWESTERN MANITOBA, REACHING THE AREA BY EARLY EVENING, AND WILL
PROVIDE AMPLE LIFT FOR THUNDERSTORM DEVELOPMENT THIS EVENING OVER
SOUTHWESTERN MANITOBA. GIVEN THE MOISTURE RICH AIRMASS, HEAVY RAIN IS
THE MAIN THREAT WITH THUNDERSTORMS THAT DEVELOP AS WELL AS LARGE
HAIL. ONE CAVEAT IS THE CLOUD COVER ASSOCIATED WITH THE IMPULSE -
WHICH WILL LIMIT DAYTIME HEATING AND THEREBY REDUCED MLCAPE VALUES
OVER THE AREA.
THE IMPULSE WILL CONTINUE TO TRACK NORTHWARD THROUGH MANITOBA THROUGH
THE OVERNIGHT WITH SHOWERS AND EMBEDDED THUNDERSTORMS FORECAST TO
LAST THROUGH THE OVERNIGHT, ALTHOUGH THE SEVERE WEATHER THREAT WILL
DIMINISH LATE IN THE EVENING. A SECOND WAVE OF NOCTURNAL ACTIVITY
WILL MOVE INTO SOUTHEASTERN SASKATCHEWAN/SOUTWESTERN MANITOBA IN THE
EARLY MORNING HOURS OF MONDAY AS A LOW WILL TRACK NORTHWARD FROM THE
US. A STRENGTHENING LOW LEVEL JET ASSOCIATED WITH THE LOW WILL
CONTINUE TO AID IN DEEP MOISTURE ADVECTION AND WILL FUEL THUNDERSTORM
DEVELOPMENT THROUGH THE MORNING HOURS. THIS LOW WILL CONTINUE TO
PROVIDE A FOCUS FOR THUNDERSTORM DEVELOPMENT THROUGH MANITOBA ON
MONDAY, WHERE HEAVY RAINFALL WILL ONCE AGAIN BE THE PRIMARY THREAT.
FOG WILL ALSO BE POSSIBLE THE NEXT FEW NIGHTS OVER THE SOUTHERN
PRAIRIES AS SEASONABLY HUMID AIR REMAINS IN PLACE OVER THE REGION.
ARCTIC...WILDFIRES LOCATED NORTHWEST OF GREAT SLAVE LAKE, NEAR WHATI,
AND NORTHWEST OF FORT CHIPEWYAN ARE GIVING POOR TO VERY POOR ACROSS
MUCH OF THE SOUTHERN NORTHWEST TERRITORIES AT THE MOMENT. A GENTLE
SOUTHEAST TO NORTHEASTERLY FLOW WILL GIVE WAY TO A STRONGER WESTERLY
FLOW TONIGHT AS A LOW AND SOME RAIN PASSES THROUGH TONIGHT.
THIS SHOULD REDUCE, BUT NOT NECESSARILY ELIMINATE, WILDFIRE SMOKE IN
THE REGION.
THIS SAME SYSTEM SHOWS THE POTENTIAL FOR LOCALLY 35 MM OF RAIN TODAY
AND TONIGHT NEAR FORT SIMPSON AND 25 MM OF RAIN NEAR KUGLUKTUK
TOMORROW.
THE LOW NEAR TALOYOAK WILL CONTINUE TO TRACK EASTWARD TODAY,
SPREADING A MIX OF PRECIPITATION THROUGH BAFFIN ISLAND. PRECIPITATION
WILL PRIMARILY FALL AS RAIN, BUT SOME SNOW MAY BE MIXED IN AT TIMES
IN NORTHERN REGIONS. NO NOTABLE AMOUNTS ARE EXPECTED.
LOW TO DEVELOP EAST OF ELLESMERE ISLAND BRINGING GALES TO CLARENCE,
KANE-S, WEST BAFFIN AND LANCASTER-E MARINE AREAS. THERE ARE STRONG
WINDS ALOFT OVER GRISE FIORD WITH THE SYSTEM BUT DIRECTION AND
INVERSION HEIGHT AREN'T TYPICAL OF A WIND WARNING SETUP AT LEAST
THROUGH THE DAY MONDAY.
END/MOODIE/KOKOLSKY/BATE
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