User's Guide/Supplemental Information

FOCN45 CWWG 021900

SIGNIFICANT WEATHER DISCUSSION ISSUED BY THE PRAIRIE AND ARCTIC STORM PREDICTION CENTRE OF ENVIRONMENT CANADA AT 2:00 PM CDT MONDAY SEPTEMBER 2 2019.

ALERTS IN EFFECT...SEVERE THUNDERSTORM WATCH POSSIBLE THIS AFTERNOON FOR SOUTHEAST SK.

SYNOPTIC OVERVIEW...ALOFT, LARGE UPPER LOW OVER EAST-CENTRAL HUDSON BAY DOMINATING THE EASTERN ARCTIC. THERE IS A SHORTWAVE TROUGH OVER CENTRAL ALBERTA WITH A TROUGH HANGING BACK THROUGH WASHINGTON STATE. AT THE SURFACE, THERE IS A 998 MB LOW VICINITY SOUTHAMPTON ISLAND AND A 994 MB LOW IS NEAR CUMBERLAND SOUND. A RIDGE OF HIGH PRESSURE STRETCHES FROM THE BEAUFORT SEA, SOUTHEASTWARD THROUGH MANITOBA, AND INTO THE US MIDWEST. A 1009 MB LOW OVER NORTH-CENTRAL ALBERTA WITH A SURFACE TROUGH EXTENDING SOUTHEASTWARD INTO SOUTHWEST SK TO ANOTHER 1009 MB LOW OVER NORTHERN MONTANA.

DISCUSSION...

WESTERN PRAIRIES...LOW PRESSURE SYSTEM NEAR LESSER SLAVE LAKE IS SUPPORTING AN AREA OF SHOWERS THAT WILL CONTINUE TO MOVE EASTWARD INTO NORTHERN SASKATCHEWAN BRINGING LOCAL AMOUNTS OF 5-20 MM BY THIS EVENING. NORTHWESTERLY WIND GUSTS TO 50 KM/H BEHIND THE COLD FRONT WILL IMPACT MUCH OF CENTRAL AND SOUTHERN ALBERTA TODAY.

EASTERN PRAIRIES...ELEVATED THUNDERSTORMS STILL ONGOING OVER EASTERN SK THIS MORNING IN RESPONSE TO STRONG SOUTHERLY LOW LEVEL JET OVERRUNNING WARM FRONT IN NORTHERN MONTANA. THESE SHOWERS AND THUNDERSHOWWERS ARE NOW TRACKING EASTWARD INTO WESTERN MANITOBA. MAIN FOCUS WILL NOW SHIFT BACK TO SK AS TROUGH MOVES INTO SK. SOUTHERLY FLOW AHEAD OF TROUGH ADVECTING TD'S INTO THE LOW TO MID TEENS THIS AFTERNOON. IMPRESSIVE 0-6 KM SHEAR EXPECTED WITH 50-60 KNOTS BY LATE AFTERNOON OVER SOUTHEAST SK. MLCAPE IN THE 1000-1300 J/KG RANGE. QUESTION OF HOW THE MORNING SHOWERS AND LOW LEVEL CLOUD LINGERING WILL AFFECT DESTABILIZATION. IF THE SUN CAN BREAK OUT EARLY ENOUGH THE AIRMASS WILL HAVE TIME TO REENERGIZE AND SEVERE STORMS ARE POSSIBLE WITH THE SHEAR AND INSTABILITY AVAILABLE. LARGER STORMS ARE EXPECTED OVER NORTH DAKOTA WHERE THERMODYNAMICS ARE MORE IMPRESSIVE AND IF THE STORMS INITIALIZE IN NORTH DAKOTA THAT MAY STEAL A LOT OF THE ENERGY AVAILABLE FOR STORMS IN SOUTHEAST SK. BUT CAPPING ISSUES WILL BE A CONCERN IN NORTH DAKOTA AND SOUTHEAST SK APPEARS TO BE ON THE NORTHERN EDGE OF CAP. SO WILL NEED TO MONITOR BUT SEVERE THUNDERSTORM WATCHES ARE POSSIBLE. TORNADO RISK IS NON ZERO WITH THE IMPRESSIVE SHEAR. STORMS THEN MIGRATE INTO SOUTHERN MANITOBA THIS EVENING AND WILL BE RATHER SLOW MOVING SO COULD SEE SOME LOCALLY HEAVY RAINFALL AMOUNTS ACROSS SOUTHERN MANITOBA.

WESTERN ARCTIC...UPPER LOW OVER THE EASTERN ARCTIC IS CONTINUING TO BRING MODERATE WINDS AND MIXED PHASE PRECIPITATION TO THE CENTRAL ARCTIC ARCHIPELAGO.

EASTERN ARCTIC...COMPLEX OF LOW PRESSURE SYSTEMS OVER THE EASTERN ARCTIC CONTINUES TO BRING UNSETTLED WEATHER TO VARIOUS COMMUNITIES THERE. LOWS ARE BEGINNING TO WEAKEN AND FILL, THEREFORE THE PRECIPITATION AND WINDS THAT HAVE BEEN PLAGUING THE REGION FOR THE PAST FEW DAYS IS BEGINNING TO SUBSIDE. A 30-35 KNOT 925 MB JET STILL REMAINS OVER SOUTHERN KIVALLIQ, WHICH CONTINUES TO GENERATE NORTHWEST WINDS WITH GUSTS TO 60-70 KM/H. THESE WINDS WILL CONTINUE TO WEAKEN THROUGHOUT THE DAY.

END/MCDONALD/WIELKI

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