PASPC Thunderstorm Outlook Day 1

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FOCN45 CWWG 251900

SIGNIFICANT WEATHER DISCUSSION ISSUED BY THE PRAIRIE AND ARCTIC STORM PREDICTION CENTRE OF ENVIRONMENT CANADA AT 2:00 PM CDT WEDNESDAY APRIL 25 2018.

ALERTS IN EFFECT...WIND WARNING FOR CHURCHILL, SNOWFALL WARNINGS FOR KIMMIRUT AND PANGNIRTUNG. SPECIAL WEATHER STATEMENT FOR CAPE DORSET, IQALUIT AND CLYDE RIVER.

SYNOPTIC OVERVIEW...

ALOFT, ARCTIC VORTEX CENTERED NEAR THE MELVILE PENNISULA WITH UPPER TROUGH EXTENDING SOUTHWESTWARD TO SOUTHERN ALBERTA. NARROW UPPER RIDGE OVER THE WESTERN US BECOMES BROADER AS IT EXTENDS NORTHWARD INTO BC AND THE YUKON. CUT-OFF LOW OVER THE EASTERN PACIFIC WEST OF CALIFORNIS.

AT THE SURFACE, 1005 MB LOW OVER FOXE BASIN. 995 MB LOW OVER CENTRAL HUDSON BAY WITH ARCTIC COLD FRONT SOUTHWESTWARD TOWARDS THOMPSON THEN ARCING NORTHWESTWARD ACROSS NORTHEASTERN SASKATCHEWAN INTO THE WESTERN NORTHWEST TERRITORIES. POLAR WV NEAR ISLAND LAKE WITH COLD FRONT EXTENDING SOUTHWESTWARD INTO SOUTHEASTERN SASKATCHEWAN. 1022 MB HIGH NORTHWEST OF ENNADAI WITH RIDGE EXTENDING NORTHWARD TOWARD VICTORIA ISLAND AND SOUTHWESTWARD INTO CENTRAL BC. 996 MB LOW NEAR INUVIK WITH TROUGH SOUTHEASTWARD ALONG THE MACKENZIE VALLEY.

DISCUSSION...

WESTERN PRAIRIES...SCATTERED SHOWERS IN SOUTHEASTERN ALBERTA WILL MOVE OUT OF THE REGION BY EVENING. OTHERWISE CLEAR AND WARM THROUGH TO SATURDAY.

EASTERN PRAIRIES...POLAR COLD FRONT CONTINUES TO PUSH SOUTHEASTWARD ACROSS THE EASTERN PRAIRIES. A FEW SHOWERS ASSOCIATED WITH THE FRONT. AIR MASS NEAR THIS FEATURE IS DRY WITH SPREADS IN THE 15 TO 20 RANGE SO EXPECT MOSTLY VIRGA WITH THE ODD SHOWER TO HIT THE SURFACE. TEMPERATURES IN THE WARM SECTOR SOUTH OF THE POLAR FRONT EXPECTED TO REACH THE LOW TWENTIES. NORTH OF THE ARCTIC FRONT IN NORTHEASTERN SASKATCHEWAN, MIXED PRECIPITATION WITH A RISK OF FREEZING RAIN WILL MOVE IN OVERNIGHT AND THURS MORNING.

LOOKING LESS LIKELY THAT WIND WARNING CRITERIA WILL BE MET IN THE CHURCHILL AND YORK REGIONS. STRONGEST NORTHERLY WINDS ARE EXPECTED TO PUSH THROUGH THE REGION EARLY THIS AFTERNOON WHEN 925 MB WINDS OF 40-45 KNOTS COME THROUGH. SHOULD STILL SEE GUSTS NEAR 80 KM/H SO WILL MAINTAIN THE WARNING UNTIL AFTERNOON UPDATE.

ARCTIC...HUDSON BAY LOW WILL CONTINUE TO PROGRESS EASTWARD TOWARDS NORTHERN QUEBEC THIS AFTERNOON WITH THE FIRST FEW FLAKES ASSOCIATED WITH THE SYSTEM HITTING THE BAFFIN COASTLINE EARLY THIS EVENING. THE SYSTEM WILL THEN TURN NORTHWARD AND DEEPEN AS IT TAPS THE COLD AIR SUPPLY OVER NORTHERN BAFFIN ISLAND. TERRAIN EFFECTS IN BAFFIN ISLAND EXPECTED TO PRODUCE WIDELY VARIABLE PRECIP AMOUNTS RANGING FROM 2-4 CM IN QIKIQTARUAQ TO POTENTIALLY EXCEEDING 25 CM IN CLYDE RIVER. RDPS SHOWNG BULLSEYES OF 15 CM IN 12 HOURS FOR BOTH KIMMIRUT AND PANGNIRTUNG LIKELY DUE TO TERRAIN-ENHANCED STRONG ONSHORE FLOW AIDED BY LOW LEVEL INSTABILITY. MODEL LIKELY OVERDOING AMOUNTS AT SEA LEVEL, ESPECIALLY IN PANGNIRTUNG WHERE DOWNSLOPE WINDS ARE FORECAST. THAT SAID, EVEN WITH REDUCED SNOWFALL ACCUMULATIONS, NEAR WARNING CRITERIA SNOWFALL AMOUNTS ARE ANTICIPATED. WIDEPREAD BLOWING SNOW IS EXPECTED WITH STRONG WINDS FORECAST FOR COMMUNITIES IN SOUTHERN BAFFIN (ONCE AGAIN EXCLUDING QIKIQTARJUAK). KIMMIRUT IS EXPECTED TO HAVE REDUCED VISIBLIITIES IN BLOWING SNOW BUT MILD TEMPERATURES AND SNOWPACK LIMITATIONS SHOULD REDUCE THE POSSIBILITY OF PROLONGED BLIZZARD CONDITIONS.

THE LOW IS FORECAST TO CONTINUE TO TRACK SLOWLY ALONG THE EASTERN COASTLINE OF BAFFIN PRODUCING A PROLONGED PERIOD OF EASTERLY FLOW OVER CLYDE. MODELS ARE INDICATING A CONDITIONALLY UNSTABLE LAPSE RATE FOR 5000 FT AND, ONCE AGAIN, HIGH PRECIPITATION AMOUNTS DUE TO TERRAIN FORCING. WHILE REASONABLE FOR RIDGE TOP, PRECIPITATION AMOUNTS SHOULD ONCE AGAIN BE LOWER AT SEA LEVEL. STRONG NORTHWESTERLY FLOW IN THE WAKE OF THE SYSTEM COULD POTENTIALLY BRING BLIZZARD CONDITION TO THE REGION THURSDAY NIGHT AND NEAR ZERO VISIBILITIES IN BLOWING SNOW HAS BEEN INTRODUCED INTO THE FORECAST FOR THIS TIME PERIOD.

END/RUSSO/NISKA-ARO