317
FOCN45 CWWG 181900
SIGNIFICANT WEATHER DISCUSSION ISSUED BY THE PRAIRIE AND ARCTIC STORM
PREDICTION CENTRE OF ENVIRONMENT CANADA AT 2:00 PM CDT SATURDAY JULY
18 2026.
ALERTS IN EFFECT...AIR QUALITY WARNINGS FOR THE SOUTHERN NWT AND
PORTIONS OF THE NORTHERN PRAIRIES. HEAT WARNINGS FOR SOUTHERN NWT,
PARTS OF NORTHERN ALBERTA, SOUTHEASTERN ALBERTA, SOUTHWESTERN
SASKATCHEWAN, PARTS OF NORTHERN SASKATCHEWAN, AND PARTS OF SOUTHERN
AND CENTRAL MANITOBA. SEVERE THUNDERSTORM WATCHES FOR PARTS OF
NORTHERN AND CENTRAL ALBERTA.
OVERVIEW...ALOFT, AN UPPER LOW SITS OVER VANCOUVER ISLAND. AN UPPER
RIDGE EXTENDS FROM THE CENTRAL CONUS NORTHWARDS THROUGH THE CENTRAL
PRAIRIES AND THROUGH THE NWT TO THE BEAUFORT SEA. UPPER LOW AND
TROUGH OVER THE KITIKMEOT AND A LARGE UPPER LOW COMPLEX CENTERED
OFFSHORE OF LABRADOR WITH TROUGHING NORTHWARD THROUGH BAFFIN ISLAND.
AT THE SURFACE, THERE IS TROUGHING OVER THE YUKON, NWT, WESTERN
NUNAVUT, BC, AND ALBERTA. SLACK FLOW OVER THE EASTERN PRAIRIES.
WEAKENING 996 MB LOW IN THE LABRADOR SEA.
DISCUSSION...
AB...A SEVERE WEATHER DAY IS EXPECTED. ISOLATED TORNADIC SUPERCELLS
DEVELOPED YESTERDAY EVENING IN THE NORTHERN FOOTHILLS AIDED BY A 30
KT JET AT H500, STRONG BACKED FLOW IN THE BOUNDARY LAYER, AND DEW
POINTS APPROACHING 20 DEG C. THIS MAY BE A PREVIEW OF THE TYPE OF
SEVERE WEATHER FOR TODAY.
IN THE UPPER LEVELS, A NEGATIVELY TILTED TROUGH IS EXPECTED TO CAUSE
A RIDGE BREAKDOWN AS THE H500 JET STRENGTHENS TO NEAR 50 KTS WITH
DIFFLUENT FLOW IN THE EXIT REGION OVER CENTRAL ALBERTA. IN
CONJUNCTION WITH NEAR SURFACE FLOW OF 10+ KTS FROM THE EAST OR
SOUTHEAST, HODOGRAPHS WILL BE QUITE CURVED. BWD VALUES WILL THEREFORE
BE SUPPORTIVE OF SUPERCELLS, MOST LIKELY OF THE CLASSIC VARIETY. AN
ELEVATED MIXED LAYER HAS ALSO BEEN EVIDENT ON THE STONY PLAIN
SOUNDING OVER THE PAST SEVERAL DAYS, WHICH SHOULD ENSURE ENOUGH
DAYTIME HEATING TO REALIZE UNUSUALLY HIGH CAPE VALUES.
RECENT RUNS OF THE RDPS AND HRDPS ARE CONSISTENTLY SUGGESTING MLCAPE
VALUES OF 3000+ J/KG WHICH IS NEARLY UNHEARD OF IN ALBERTA. THE MAIN
QUESTION IS WHERE EXACTLY THE SURFACE LOW DEVELOPS AS TORNADIC
POTENTIAL WILL BE MAXIMIZED IN THE NORTHEAST QUADRANT. THE BEST
CHANCE FOR STRONG AND/OR MULTIPLE TORNADOES WILL COINCIDE WITH THE
INTERSECTION OF A DRYLINE AND COLD FRONT. NWP GUIDANCE HAS BEEN
GRADUALLY PULLING THIS FEATURE NORTH AND WEST WITH SUCCESSIVE RUNS,
FROM THE SASKATCHEWAN BORDER TOWARD THE EDMONTON METRO AREA.
THIS AREA WILL BE MONITORED VERY CLOSELY TODAY, AS ANY STORMS THAT
FORM IN THIS ENVIRONMENT WILL LIKELY BE DANGEROUS. IT SHOULD BE NOTED
THAT THIS EXACT TYPE OF PATTERN, WHILE RARE, HAS HISTORICALLY BEEN
ASSOCIATED WITH LONG-TRACK, TORNADIC SUPERCELLS.
ELSEWHERE IN THE PROVINCE. SMOKE HAS DRIFTED INTO NORTHERN ALBERTA
FROM THE NWT, AND AIR QUALITY WARNINGS HAVE BEEN ISSUED ACCORDINGLY.
SOME IMPROVEMENT IS POSSIBLE TODAY WITH SURFACE FLOW TURNING WEAKLY
SOUTHEAST. HEAT WARNINGS ALSO REMAIN IN NORTHERN ALBERTA FOR TODAY,
THOUGH SMOKE IN THE AREA MAY HINDER DAYTIME HIGH TEMPERATURES. COOLER
TEMPERATURES ARE FORECAST FOR SUNDAY. A HEAT WARNING IS ALSO IN
EFFECT FOR SOUTHEASTERN ALBERTA.
SK/MB...A FAVOURABLE SETUP FOR SUPERCELLS TODAY IN WEST CENTRAL
SASKATCHEWAN WITH ALL MODES OF SEVERE WEATHER POSSIBLE INCLUDING
TORNADOES. STRONG 250 AND 500 MB JETS ACROSS SOUTHERN ALBERTA WITH
LEFT EXIT REGION SITTING RIGHT ALONG DEVELOPING WARM FRONT FROM LOW
CURRENTLY DEVELOPING IN CENTRAL ALBERTA. STRONG VEERING PROFILES,
COMBINED WITH 1500 TO 2500 J/KG OF MIXED LAYER CAPE AND 30 TO 35
KNOTS OF 0 TO 6 KM BULK LAYER SHEAR SIT ON WEST SIDE OF UPPER RIDGES
BY 00Z. NORTH BATTLEFORD TO PRINCE ALBERT AND MEADOW LAKE REGIONS ARE
THE MOST FAVOURABLE AREA OF TORNADIC SUPERCELLS TODAY. FURTHER SOUTH
STRETCHING DOWN TO THE US BORDER, STRONG WIND SHEARS WITH SLIGHTLY
LESS CAPE COULD SEE MORE OF A QLCS OR MULTICELL SET UP. CAPPING WILL
BE AN ISSUE EARLIER IN THE DAY WITH MORE OF A LATE SHOW EXPECTED.
STORMS MAY REMAIN SEVERE OVER SOUTHERN SASKATCHEWAN THOUGH THE NIGHT.
CURRENT ONGOING MORNING CONVECTION ALON WITH SMOKE STREAMING INTO THE
REGION FROM WASHINGTON COULD HAMPER TODAYS SET UP.
WILDFIRES CONTINUE TO BURN IN NORTHERN MB AND SK, REDUCING AIR
QUALITY DOWNWIND OF THE FIRES. AIR QUALITY WARNINGS CONTINUE FOR THE
AREA.
UNDER THE INFLUENCE OF THE UPPER RIDGE, PORTIONS OF SOUTHWEST
SASKATCHEWAN, PARTS OF NORTHEN SASKATCHEWAN, AS WELL AS SOUTHERN AND
CENTRAL MANITOBA WILL SEE HEAT WARNING CRITERIA BEING MET. DAYTIME
HIGHS IN THE LOW 30S COMBINED WITH OVERNIGHT LOWS IN THE HIGH TEENS
AND HUMIDEX VALUES 38 AND HIGHER WILL CONTINUE THROUGH THE WEEKEND.
DAY 2 OUTLOOK FOR MB...
THE PATTERN AND FOCUS FOR MAJOR CONVECTION SHIFTS EAST TO MANITOBA
SUNDAY AS THE LOW CENTER SITS NEAR FLIN FLON BY MIDDAY. WITH THE WARM
FRONT RUNNING EAST FROM THAT POINT AND COLD FRONT SOUTHWARDS ALONG
THE SK/MB BORDER IN THE AFTERNOON, MOST OF SOUTHERN AND CENTRAL MB
WILL BE SITTING IN 20C+ DEWPOINTS AND SIGNIFICANT INSTABILITY FOR THE
DAY; 1500 TO 2500 J/KG MLCAPE ALONG WITH 40 KNOTS OF DEEP SHEAR
BELOW A 100 KNOT UPPER LEVEL JET. THERE ARE, IN SPOTS, SOME NICELY
VEERING PROFILES TO SUPPORT SUPERCELLS AND ALL WEATHER HAZARDS: HEAVY
RAIN, LARGE HAIL, DAMAGING WINDS, AND TORNADOES. THERE WILL BE
THUNDERSTORMS AND SEVERE THUNDERSTORMS FOR THE AREA, AND A BROAD HIGH
RISK FOR MUCH OF IT.
BUT THE OVERALL CHARACTER OF THE DAY SO FAR IS STILL ONE OF
CONDITIONS AND UNCERTAINTY FOR MODE AND TIMING. THERE IS ROUGHLY -30
J/KG OR STRONGER MLCIN FORECAST OVER THE ENTIRE AREA THROUGH THE
AFTERNOON AND EVENING. WITH THAT, ISOLATED CELLS OR SUPERCELLS IN THE
MAIN AIRMASS ARE NOT LIKELY. ON THE NORTHERN PERIPHERY, SCATTERED
THUNDERSTORMS - POTENTIALLY ALREADY SEVERE - WILL BE ONGOING IN THE
NORTHERN PARKLANDS AND INTERLAKE SUNDAY MORNING. WHILE THIS WOULD
DIMINISH LATER ACTIVITY OVER THOSE SAME AREAS, THE OUTFLOW
BOUNDARIES, COUPLED WITH TERRAIN AND LAKE BREEZE INTERACTIONS, MAY
PROVE ENOUGH TO OVERCOME THE CAP OUTRIGHT ELSEWHERE. EVEN IF NOT,
ELEVATED CONVECTION ITSELF CAN RESURFACE AS IT PROGRESSES SOUTHEAST
INTO THE AFTERNOON. LATEST CAMS TEND TO LEAN INCREASINGLY TOWARD THE
LATTERMOST OPTION, GENERALLY INTENSIFYING RAPIDLY OVER WESTERN
MANITOBA INTO BOWING SEGMENTS. THESE THUNDERSTORMS WILL BE DOMINATED
BY INCREASINGLY WESTERLY WINDS ALOFT AND RAPID UPSCALE GROWTH
PRODUCING A THREAT OF VERY HIGH STRAIGHT LINE WINDS AT THE SURFACE -
WELL IN EXCESS OF 100 KM/H. THE COMBINATION OF ALL THE ABOVE MAKES
TIMING PARTICULARLY HARD TO NAIL DOWN, WITH MAJOR ACTIVITY IN THE RRV
RANGING ANYWHERE FROM LATE MORNING TO LATE EVENING WHEN THE COLD
FRONT IS ABOUT TO EXIT THE PROVINCE.
BUT AT ANY RATE, EVEN WITH THE CAPPING INVERSION, THERE REMAIN
MULTIPLE OPPORTUNITIES FOR WIDESPREAD AND RAPID THUNDERSTORM
DEVELOPMENT. WHILE THEY DIFFER IN PARTICULARS, NEARLY ALL ARE
INDICATING POTENTIAL FOR ONE OR MORE MAJOR HAZARDS OVER SOUTHERN
MANITOBA. SEVERE ACTIVITY WILL DEPART SOUTHEAST OUT OF THE PROVINCE
EARLY OVERNIGHT INTO MONDAY.
NT/NU...FIRES WERE VERY ACTIVE BETWEEN GREAT SLAVE LAKE AND THE
MACKENZIE RIVER THIS WEEK AND A LOT OF SMOKE WAS THROWN INTO THE
ATMOSPHERE. WHILE NORTHWEST FLOW HAS BROUGHT ABOUT SOME IMPROVEMENT
FOR COMMUNITIES ALONG THE MACKENZIE RIVER, SMOKE WILL CONTINUE SWIRL
AROUND SOUTHERN PORTIONS OF THE TERRITORY, KEEPING AIR QUALITY POOR
IN THE AREA.
A HEAT WARNING REMAINS IN EFFECT FOR SOUTHERN REGIONS. COOLER
TEMPERATURES ARE FORECAST FOR SUNDAY, BUT DAYTIME HIGHS IN THE LOW
30S MAY RETURN NEXT WEEK.
AS THE LABRADOR LOW CONTINUES TO SPIN, SOUTHEASTERN BAFFIN ISLAND
WILL SEE SHOWERS CONTINUE OVER THE NEXT FEW DAYS WITH NO SIGNIFICANT
QPF IN ANY TOWN SITES.
END/LUZNY/DYCK/KNIGHT/VAN LOCHEM/VALLEE
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