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FOCN45 CWWG 311200 SIGNIFICANT WEATHER DISCUSSION ISSUED BY THE PRAIRIE AND ARCTIC STORM PREDICTION CENTRE OF ENVIRONMENT CANADA AT 7:00 AM CDT THURSDAY MAY 31 2018. ALERTS IN EFFECT...WIND WARNING FOR CAPE DORSET. SYNOPTIC OVERVIEW...GENERALLY A SOUTHWESTERLY FLOW ALOFT OVER MUCH OF THE PRAIRIES. RELATIVELY STRONG SHORTWAVE TROUGH OVER NORTHWESTERN ONTARIO EXTENDING SOUTHWESTWARD INTO THE AMERICAN MIDWEST TRACKING EASTWARD. ANOTHER UPPER TROUGH IMPINGING UPON THE WEST COAST OF THE UNITED STATES. LARGE UPPER LOW CIRCULATION COVERS THE CENTRAL AND EASTERN ARCTIC, WITH THREE CENTRES, THE STRONGEST OF WHICH IS OVER FOXE BASIN THIS MORNING. AT THE SURFACE, 982 MB LOW OVER FOXE BASIN. RIDGE OF HIGH PRESSURE EXTENDING FROM THE CWESTERN ARCTIC ARCHIPELAGO SOUTHEASTWARD ACROSS SOUTHERN KIVALLIQ. FRONTAL BOUNDARY THAT STADDLES NORTHWEST TO SOUTHEAST ACROSS NORTHERN ONTARIO INTO THE DAKOTAS AND MONTANA. DISCUSSION... WESTERN PRAIRIES...A BOUT OF PROLONGED SOAKING RAINS WILL OCCUR OVER THE SOUTHERN THIRD OF THE PROVINCE DURING THIS FORECAST PERIOD. RAIN WILL BEGIN THIS AFTERNOON AND CONTINUE UNTIL FRIDAY EVENING, AS THE PROVINCE EXPERIENCES THE COLD SIDE OF THE UPPER JET. TOTAL 48-HOUR AMOUNTS SHOULD BE IN THE 20 TO 40 MM RANGE, BUT REGIONS SOUTH OF A PINCHER CREEK-OYEN LINE MAY SEE UP TO 60 MM BEFORE RAIN ENDS, ESPECIALLY WITH ANY LEFTOVER/REMNANT CONVECTION THAT SPILLS INTO THE PROVINCE FROM SASKATCHEWAN AND MONTANA. EASTERN PRAIRIES...EXTREME SOUTHERN SASKATCHEWAN INTO SOUTHWESTERN MANITOBA... SOUTH OF THE INTERNATIONAL BORDER IN MONTANA AND NORTH DAKOTA, EXCELLENT DYNAMICS AND THERMODYNAMICS ARE SETTING UP FOR TODAY WITH THE POSSIBILITY OF ALL SEVERE WEATHER TYPES THERE INCLUDING TORNADO POTENTIAL. THE PRIMARY FORECAST UNCERTAINTY AT THIS TIME IS THE PLACEMENT OF A WARM FRONT, CURRENTLY FORECAST ENTIRELY ON THE AMERICAN SIDE IN NORTHEASTERN MT INTO NORTHWESTERN ND - SHOULD THIS BEGIN TO LIFT NORTHWARD INTO EXTREME SOUTHEASTERN SK/SOUTHWESTERN MB UPGRADED THREAT LEVELS AND HAZARDS WILL BE NEEDED FOR THE REGION. BUT SO FAR JUST NORTH ON THE CANADIAN SIDE, COOLER AND DRIER NORTHERLIES ARE OCCURRING AT THE SURFACE AND LOOK TO ABRUPTLY DIMINISH THE AVAILABLE MOISTURE AND INSTABILITY FOR SEVERE THUNDERSTORM SUPPORT. WITH LIMITED INSTABILITY, WEAK TROUGHING NEAR THE CYPRESS HILLS AND SOME TERRAIN INTERACTIONS COULD PROVIDE SUFFICIENT TRIGGER THERE FOR AFTERNOON THUNDERSTORM DEVELOPMENT. FARTHER EAST FOR EXTREME SOUTHEASTERN SASKATCHEWAN AND SOUTHWESTERN MANITOBA, SLIGHTLY HIGHER DEWPOINTS REMAIN BUT WITH EITHER FLAT OR SLIGHT WARM AIR ADVECTION IN THE LOWER LEVELS; SURFACE-BASED DEVELOPMENT HERE IS POSSIBLE BUT STILL SOMEWHAT UNLIKELY DESPITE BETTER INSTABILITY. HOWEVER, THE UPPER LEVEL JET STREAM OVER THE ENTIRE AREA REMAINS STRONG - 80 KNOTS FROM THE SOUTHWEST - AND WILL PERMIT STRONGER STORMS TO CROSS THE BORDER AS THEY DEVELOP DOWN SOUTH IN THE AFTERNOON. EVEN WITHOUT CONTINUED INSTABILITY TO FUEL THE THUNDERSTORMS, ALREADY DEVELOPED CELLS WILL PRESENT A THREAT OF STRONG WIND GUSTS ESPECIALLY AS THEY BEGIN TO COLLAPSE. MARGINALLY SEVERE HAIL IS ALSO POSSIBLE. THIS SEVERE WEATHER POTENTIAL WILL CONTINUE THROUGH THE NIGHT AS THE FAVOURABLE JET DYNAMICS REMAIN IN PLACE AND CONVECTION BECOMES ELEVATED. GENERAL NON-SEVERE THUNDERSTORM ACTIVITY WILL ALSO BEGIN TO EXPAND NORTHWARD TOWARDS CENTRAL SASKATCHEWAN AND THE REMAINDER OF SOUTHERN MANITOBA THROUGH THE NIGHT AS BOTH STORM MOTION INCREASES AND THE UPPER FLOW TURNS MORE NORTHWARD. EASTERN ARCTIC...STRONG WEST/NORTHWESTERLY FLOW IS NOW IN PLACE ON THE BACKSIDE OF THE FOXE BASIN LOW OVER WESTRN QIKIQTAALUK AND NORTHERN KIVALLIQ. ALTHOUGH BLIZZARD/NEAR BLIZZARD CONDITIONS WERE REPORTED OVERNIGHT AT HALL BEACH WEB CAMS AT THE AIRPORT INDICATE BETTER VSBYS THAN WHAT THE AUTO STATION IS REPORTING. THERE ARE ADVANTAGES TO HAVING 24 HOURS OF DAYLIGHT. WILL HAVE TO WAIT FOR THE MANNED OBSERVATION TO SEE IF THIS IS ALSO THE CASE IN NAUJAAT. WIND WARNING REMAINS IN EFFECT FOR THE CAPE DORSET AREA. 925 MB WINDS TOP OUT NEAR 50 KTS NEAR MIDDAY THEN DIMINISH IN THE AFTERNOON. SNOWFALL AMOUNTS AT BOTH PANGNIRTUNG AND CLYDE RIVER HAVE BEEN NUDGED DOWNWARDS AS WE SUSPECT SNOWFALL AMOUNTS IN SCRIBE ARE BEING INFLUENCED BY UPSLOPE TERRAIN ENHANCEMENT. END/RUSSO/CARLSEN
Started by PaulMy
Started by JennyLeez
Started by Mark