PASPC Thunderstorm Outlook Day 1

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FOCN45 CWWG 221300

SIGNIFICANT WEATHER DISCUSSION ISSUED BY THE PRAIRIE AND ARCTIC STORM PREDICTION CENTRE OF ENVIRONMENT CANADA AT 7:00 AM CST THURSDAY FEBRUARY 22 2018.

ALERTS IN EFFECT...EXTREME COLD WARNINGS FOR PARTS OF THE KITIKMEOT.

SYNOPTIC OVERVIEW...LOOKING ALOFT, A BROAD RIDGE-TROUGH-RIDGE PATTERN EXISTS OVER NOAM WITH A HIGH-AMPLITUDE RIDGE OVER THE EASTERN PACIFIC, A BROAD TROUGH EXTENDING FROM A COLD LOW OVER NUNAVUT SOUTHWESTWARDS TO CALIFORNIA, AND A HIGH OVER THE SE UNITED STATES.

THE PACIFIC JET ENTERS CANADA VIA THE AK/YT BORDER RIDING OVER THE APEX OF A HIGH-AMPLITUDE RIDGE OFF THE WESTERN NOAM COAST. PACIFIC JET THEN DIVES SOUTHWARDS ALONG THE B.C. COAST AND THEN TURNS EASTWARDS THROUGH CA/NV AT THE BASE OF AN UPPER LOW DIGGING SOUTHWARDS THROUGH OR/WA. PACIFIC JET THEN EJECTS NORTHEASTWARDS OUT OF CO AND ACROSS THE AMERICAN PLAINS, CROSSING OVER LAKE SUPERIOR AND THEN THROUGH ON/QC/NL. POLAR JET DIVES SOUTHWARDS THROUGH THE NWT AND THEN TURNS EASTWARDS ACROSS NORTHERN SK/MB THROUGH THE BASE OF AN UPPER LOW MOVING EASTWARDS ALONG THE MB/NU BORDER. THE POLAR JET THEN RIDES EASTWARDS ACROSS HUDSON BAY AND NORTHERN QC/NL.

AT THE SURFACE, THE MAIN FEATURE IS A 1002 MB LOW TRACKING EASTWARDS ALONG THE MB/NU BORDER WITH WARM FRONT RUNNING SSW FROM NW MB INTO CENTRAL SK AND COLD FRONT DRAPED THROUGH NW MB AND NORTHERN SK, ARCING BACK NORTHWARDS INTO THE NWT OVER GREAT SLAVE LAKE. FLANKING IT TO THE SW IS A 1032 MB HIGH OVER THE B.C. INTERIOR AND TO THE SE IS A 1042 MB HIGH OVER LAKE SUPERIOR WITH A RIDGE AXIS EXTENDING WESTWARDS ALONG THE CANADA/US BORDER.

DISCUSSION...

EASTERN ARCTIC...SOME BLOWING SNOW POSSIBLE IN ARVIAT LATER TODAY INTO TONIGHT WITH GUSTY NORTHWESTERLY WINDS BEHIND THE PASSAGE OF A COLD FRONT. COMPARED WITH CHURCHILL, EVERYTHING SEEMS MORE MARGINAL, AND THUS THE CONDITIONS WILL BE MANAGED BY BLOWING SNOW FREQUENTLY LESS THAN 1 KM IN THE PUBLIC FORECAST.

LIGHT SNOW CONTINUES ACROSS PORTIONS OF BAFFIN ISLAND AND THE QIKIQTAALUK.

NEAR-WARNING WIND CHILLS POSSIBLE AT TIMES OVER BAFFIN ISLAND IN THE COMING DAYS, BUT NOT EXPECTING THE WARNING CRITERIA TO BE EXCEEDED.

EASTERN PRAIRIES...SOME LIGHT SNOW WILL FALL TODAY ACROSS NORTHERN MANITOBA AS THE FRONTAL WAVE ASSOCIATED WITH THE LOW TRACKING ALONG THE MB/NU BORDER MOVES THROUGH.

IN CHURCHILL, CONDITIONS LOOK FAVOURABLE FOR NEAR-BLIZZARD CONDITIONS THIS AFTERNOON IN THE WAKE OF A COLD FRONT PASSAGE. WINDS WILL INCREASE OUT OF THE WEST TO 40-50G70 KM/H AND TEMPERATURES WILL BEGIN DROPPING TOWARDS THE -25 TO -30C RANGE. LOW-LEVEL LAPSE RATES WILL BE DEEP AND STEEP, WITH A NEAR- TO SLIGHTLY SUPER-SATURATED BOUNDARY LAYER WITH RESPECT TO ICE. THE STRONG WINDS WILL BE PRECEDED BY SEVERAL HOURS OF LIGHT SNOW WHILE THE ACCUMULATIONS WON'T BE PARTICULARLY NOTABLE, IT MAY BE ENOUGH TO HELP KICK-START THE BLOWING SNOW. IN THE END, THOUGH, THERE IS SIGNIFICANT UNCERTAINTY IN THE WORST CONDITIONS BEING SUSTAINED FOR 6 CONSECUTIVE HOURS. IT'S NOT A MATTER OF WHETHER OR NOT CONDITIONS WILL BE BAD ENOUGH, RATHER THE QUESTION IS WILL IT LAST LONG ENOUGH? WILL COVER WITH NEAR-ZERO VISIBILITIES IN BLOWING SNOW IN THE FORECAST AND A WATCHFUL EYE AS THE DAY PROGRESSES.

BENIGN WEATHER OVER THE SOUTHERN PRAIRIES.

WESTERN PRAIRIES...A CHANGE IN THE UPPER PATTERN FRIDAY WILL BRING A RETURN TO ZONAL FLOW OVER THE MOUNTAINS. AS A RESULT GUSTY CONDITIONS WILL BE SEEN ALONG THE MOUNTAINS FROM GRANDE PRAIRIE TO THE INTERNATIONAL BOARDER. GUSTS OF 70 KM/H ARE EXPECTED ALONG THE MOUNTAINS WITH THE STRONGEST WINDS IN THE USUAL PINCHER CREEK AREA. WIND WARNING MAY BE HIT IN THE PINCHER CREEK REGION, BUT AT THIS TIME IT LOOKS MARGINAL SO GUSTS GO 90 KM/H HAVE BEEN PUT IN THE FORECAST.

KITIKMEOT...EXTREME COLD WARNING CONTINUES WITH WIND CHILL VALUES NEAR MINUS 55. A WARMING TREND ON FRIDAY WILL BRING AN END TO THE EXTREME COLD WARNING.

WESTERN ARCTIC...FRIDAY, A LOW PRESSURE SYSTEM WILL MOVE SOUTHWARD FROM THE ARCTIC OCEAN TO STRENGTHEN THE PRESSURE GRADIENT ALONG THE ARCTIC COAST. TUKTOYATUK LOOKS LIKE IT WILL BEAR THE BRUNT OF THE STORM WITH A BLIZZARD STARTING FRIDAY AND LASTING INTO SUNDAY EVENING. SACHS HARBOUR AND PAULATUK ARE EXPECTED TO SEE NEAR BLIZZARD CONDITIONS STARTING LATE FRIDAY AND LASTING INTO SUNDAY. ULUKHATOK MAY SEE BLIZZARD CONDITIONS ON SUNDAY. THE BLIZZARD WARNINGS MAY HAVE TO BE EXTEND TO THESE COMMUNITIES AS THE EVENT DRAWS NEAR.

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