PASPC Thunderstorm Outlook Day 1

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FOCN45 CWWG 231900

SIGNIFICANT WEATHER DISCUSSION ISSUED BY THE PRAIRIE AND ARCTIC STORM PREDICTION CENTRE OF ENVIRONMENT CANADA AT 2:00 PM CDT MONDAY APRIL 23 2018.

ALERTS IN EFFECT...NONE.

SYNOPTIC OVERVIEW...ALOFT, THE PATTERN IS DEFINED BY A PERSISTENT VORTEX OVER THE CANADIAN ARCTIC ARCHIPELAGO WITH A BROAD LONG-WAVE TROUGH EXTENDING SOUTHWARDS INTO HUDSON BAY AND THEN SOUTHWESTWARDS ACROSS MB/SK INTO MT/WY. WITHIN THIS LONG-WAVE TROUGH ARE TWO MAJOR UPPER LOWS: THE FIRST IS OVER SOUTHWESTERN HUDSON BAY AND THE SECOND IS OVER SOUTHERN MONTANA. WEST OF THE LONG-WAVE TROUGH A RATHER SHARP UPPER-LEVEL RIDGE IS IN PLACE, EXTENDING FROM WASHINGTON STATE NORTHWARDS ACROSS B.C./WESTERN AB INTO THE MACKENZIE REGION OF THE NWT.

AT THE SURFACE, HUDSON BAY UPPER LOW HAS A 1003 MB LOW OVER THE SOUTHERN HUDSON BAY. A STRONG BAROCLINIC ZONE RUNS THROUGH NORTHERN QUEBEC INTO THIS LOW AND EXTENDS WESTWARD THROUGH THE NORTHERN PRAIRIES AND CENTRAL YUKON. A BROAD AREA OF HIGH PRESSURE COVERS MUCH OF THE WESTERN PRAIRIES WITH A 1033 MB HIGH ON THE CANADIAN GREAT DIVIDE. FURTHER NORTH, A 1029 MB HIGH SITS OVER WESTERN NUNAVUT WITH SURFACE RIDGE EXTENDING EASTWARDS TO SOUTHAMPTON ISLAND. A 998 MB LOW SITS OVER BAFFIN BAY.

DISCUSSION...

WESTERN PRAIRIES...A RIDGE OF HIGH PRESSURE BUILDS IN FROM BC AT BOTH THE SURFACE AND ALOFT. TEMPERATURES WILL GRADUALLY WARM TO NEAR NORMALS TODAY IN ALBERTA AND THEN WE HIT THE 20 DEGREE MARK FOR TUESDAY!!! IT'S FINALLY SPRING!

EASTERN PRAIRIES...FLURRIES AND PERIODS OF LIGHT SNOW CONTINUE IN THE UPPER TROUGH OVER NORTHERN MANITOBA THIS AFTERNOON AND EVENING. CLEARING FORECAST TONIGHT AS THE UPPER TROUGH SLIDES EASTWARD AND THE SURFACE RIDGE BUILDS IN. IT CONTINUES TO BE QUIET OVER THE SOUTHERN PRAIRIES WITH SURFACE HIGH BUILDING IN FROM BRITISH COLUMBIA.

WESTERN ARCTIC...CLOUD IS SPREADING INTO THE MACKENZIE AHEAD OF A PACIFIC LOW WHICH IS DEVELOPING OVER THE CENTRAL NWT TUESDAY. A COUPLE CM OF SNOW WITH A RISK OF FREEZING RAIN WILL SPREAD SOUTHEASTWARD FROM NORMAN WELLS TO NORTH OF GREAT SLAVE LAKE THEN TO LUTSEL K'E. FREEZING RAIN IS MOST LIKELY NEAR GAMETI AND WEKWEETI WHERE THERE IS MORE MOISTURE AND A MORE PROLONGED AFL.

EASTERN ARCTIC...SO FAR NO VISIBILITY REDUCTION WITH THE WINDS IN IQALUIT. WINDS ARE FORECAST TO INCREASE TO 40 GUSTING TO 60 KM/H, BUT GIVEN THAT THERE HASN'T BEEN MUCH BLOWING SNOW THUS FAR, SIGNIFICANT VISIBILITY RESTRICTION APPEARS LESS LIKELY. LIGHT TO MODERATE SNOW WILL CONTINUE NEAR POND INLET FOR THE NEXT COUPLE DAYS WITH ACCUMULATIONS TOPPING OUT AT 2-4 CM PER 12 HOURS.

FURTHER WEST, LIGHT SNOW WILL SPREAD BACK INTO THE MELVILLE PENINSULA OVER THE NEXT COUPLE DAYS, COMBINING WITH PERSISTENT NORTHWESTERLY WINDS OF 30 TO 40 KM/H TO PRODUCE OCCASIONALLY REDUCED VISIBILITIES IN BLOWING SNOW.

AS THE MACKENZIE LOW MOVES EASTWARD, THE NEXT CONCERN WILL BE THE SPREAD OF SNOW INTO ARVIAT ON WEDNESDAY. WARNING AMOUNTS OF SNOWFALL ARE POSSIBLE WITH NORTHERLY WIND GUSTS NEAR 70 KM/H. THE TRACK AND INTENSITY OF THE LOW ARE STILL VERY UNCERTAIN, BUT A BRIEF BLIZZARD IS A POSSIBILITY.

END/VAN WILGENBURG/ANISKA-ARO