600
FOCN45 CWWG 221900
SIGNIFICANT WEATHER DISCUSSION ISSUED BY THE PRAIRIE AND ARCTIC STORM
PREDICTION CENTRE OF ENVIRONMENT CANADA AT 2:00 PM CDT TUESDAY JULY
22 2025.
ALERTS IN EFFECT...AIR QUALITY ALERTS FOR PARTS OF ALBERTA,
SASKATCHEWAN AND MANITOBA. RAINFALL WARNING FOR BAKER LAKE AND PARTS
OF SOUTHERN ALBERTA.
SYNOPSIS...ALOFT, RIDGING OVER THE PACIFIC. LONG WAVE TROUGH FROM LOW
IN BAFFIN BAY SOUTHWEST TO ADDITIONAL UPPER LOWS IN THE KIVALLIQ AND
THE US NW COAST OVER OREGON. SHORT WAVE TROUGH THROUGH ONTARIO.
RIDGE THROUGH QUEBEC AND HUDSON BAY. TROUGH OFF THE EAST COAST.
AT THE SURFACE, BROAD LOW PRESSURE OVER NORTHERN BAFFIN ISLAND.
999 MB LOW JUST WEST OF ARVIAT WITH WARM FRONT TO THE SOUTHEAST AND
COLD FRONT TO THE SOUTHWEST THROUGH SOUTHERN SK AND AB. OCCLUDED
FRONT THROUGH CENTRAL MB. ASSOCIATED SURFACE FRONTAL WAVE IN
SOUTHEASTERN MONTANA.
DISCUSSION...
AB...RAINFALL CONTINUES OVER SOUTHERN ALBERTA WITH ADDITIONAL AMOUNTS
IN THE 10-25 MM RANGE EXPECTED. A RAINFALL WARNING REMAINS IN EFFECT
FOR CALGARY AND SECTIONS OF THE FOOTHILLS IMMEDIATELY TO THE WEST
WHERE 24 HOUR TOTAL RAINFALL IS EXPECTED TO REACH 50 MM. RAIN WILL
END LATE THIS AFTERNOON FOR THE CALGARY AREA.
FURTHER SOUTH, A SHORT WAVE FROM THE UPPER TROUGH IN BC WILL PROVIDE
THE TRIGGER FOR THUNDERSTORMS IN THE SOUTHEAST CORNER OF THE PROVINCE
TODAY. MLCAPE WILL BE IN THE 400-700 J/KG RANGE AND EFFECTIVE SHEAR
AROUND 20-25 KT. THE MAIN THREATS WITH THESE STORMS WILL BE SMALL
HAIL AND HEAVY RAIN.
HIGH PRESSURE AND COOL TEMPERATURES WILL SLUMP SOUTH
THROUGHOUT THE DAY. CLEAR SKIES TONIGHT AND MINIMAL WIND OVERNIGHT
WILL LIKELY GENERATE WIDESPREAD FOG ACROSS SOUTHERN ALBERTA.
ADDITIONALLY, SOME AREAS OVER CENTRAL AB AND ALONG THE FOOTHILLS
ARE FORECAST SEE TEMPERATURES IN THE LOW SINGLE DIGITS TONIGHT.
AREAS JUST NORTHWEST OF CALGARY (INCLUDING SUNDRE, ROCKY MOUNTAIN
HOUSE) WILL LIKELY SEE PATCHY FROST TONIGHT AS TEMPERATURES HOVER
NEAR 0C. A FROST ADVISORY WILL BE FORTHCOMING THIS AFTERNOON.
SK/MB...CONVECTION FROM LAST NIGHT THAT DEVELOPED IN MONTANA AND
NORTH DAKOTA WILL CONTINUE TO TRACK THROUGH SOUTHEASTERN SK AND
SOUTHERN MANITOBA TODAY. A GENERAL 10-20 MM OF RAIN IS POSSIBLE BY
TONIGHT. A SURFACE RIDGE OF HIGH PRESURE BUILDS IN BEHIND INTO S SK,
BRINGING WITH IT A VERY WEAK FLOW AND SMOKY CONDITIONS. SOME SHOWERS
DEVELOP IN SW SK TUESDAY NIGHT AND TRACK EAST OVER THE NIGHT
SUPPORTED BY A SHORT WAVE EJECTED FROM THE UPPER LOW CURRENTLY OVER
OREGON. AMOUNTS WILL REMAIN MINIMAL; 5-10 MM BY WEDNESDAY MORNING.
CONVECTIVE POTENTIAL TODAY REMAINS SUB-SEVERE AS THUNDERSTORMS WILL
BE EMBEDDED IN A LARGER AREA OF SHOWERS. SURFACE RIDGE THROUGH SK/MB
KEEPS INSTABILITY MINIMAL. THERE IS A SLIGHT RISK OF SUB-SEVERE
CONVECTIVE ACTIVITY CONTINUING THROUGH THE OVERNIGHT PERIOD IN SE SK
AND SW MB SUPPORTED BY THE AFOREMENTIONED SHORTWAVE TRACKING EAST
THROUGH SK.
WILDFIRE SMOKE IS SLOWLY PUSHING SOUTH AND EAST ALONG THE COLD FRONT.
IN SOUTHERN SK. WARNINGS ARE ANTICIPATED TO BE EXPANDED TO THE MB
BORDER BY THE END OF THE DAY. IN SOUTHERN MANITOBA, WARNINGS ARE
EXPECTED TO EXPAND TO THE CITY OF WINNIPEG BY THE END OF THE DAY.
IN NORTHERN MANITOBA, CLEARING IN BEHIND THE COLD FRONT IS EXPECTED
ALONG THE NU BORDER.
NT...SHORTWAVES RIDING AN UPPER WARM FRONT IN THE WESTERN NT WILL
BRING SOME SHOWERS WITH ISOLATED THUNDERSTORMS TO THE NORTHERN
MACKENZIE VALLEY TODAY. THEY ARE EXPECTED TO TRIGGER OFF THE
MACKENZIE MOUNTAINS, AND WEAK FLOW ALOFT SHOULD KEEP THUNDERSTORMS
CONFINED TO THE TERRAIN, LEAVING REMNANT SHOWERS TO EFFECT AREAS
NORTH OF NORMAN WELLS. THE EXCEPTION BEING NEAR FORT MCPHERSON, WHERE
ISOLATED THUNDERSTORMS ARE EXPECTED TODAY. A RIDGE DOMINATES THE REST
OF THE NT.
NU...RAINFALL AMOUNTS ASSOCIATED WITH THE SURFACE LOW NEAR ARVIAT
WILL REMAIN SUB SEVERE FOR ALL COMMUNITIES EXCEPT BAKER LAKE WHERE A
RAINFALL WARNING HAS BEEN ISSUED. 24 HOUR TOTALS WILL BE HIGHEST FOR
BAKER LAKE FOLLOWED BY CHESTERFIELD INLET OF UP TO 35 MM AND 20 MM
RESPECTIVELY BY TONIGHT. GOOD AGREEMENT BETWEEN ECMWF AND GEM
DETERMINISTIC AND ENSEMBLES OF WARNING LEVEL RAIN AT BAKER LAKE BY
TONIGHT. THE NOW 999 MB SURFACE LOW NEAR ARVIAT WILL CONTINUE TO
DEEPEN TO 994 MB TODAY, WRAPPING IN MOISTURE FROM LAST NIGHTS
THUNDERSTORMS INTO THE TROWAL AND INTO BAKER LAKE.
THE TROWAL AND SURFACE LOW CONTINUE TO TRACK NORTHEAST OVER THE
FORECAST PERIOD INTO SOUTHERN BAFFIN BRINGING UP TO 10 MM RAINFALL
AMOUNTS TO KINNGAIT AND KIMMIRUT BY WEDNESDAY NIGHT.
WINDS AROUND THE LOW WILL BE STRONGEST TODAY OF EASTERLY 40 GUSTING
TO 60 KM/H IN CHESTERFIELD INLET AND SOUTHWESTERLY 40 GUSTING TO
60 KM/H IN ARVIAT.
END/DYCK/CARLSEN/PIMISKERN
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