426  
FOCN45 CWWG 261900  
SIGNIFICANT WEATHER DISCUSSION ISSUED BY THE PRAIRIE AND ARCTIC STORM  
PREDICTION CENTRE OF ENVIRONMENT CANADA AT 2:00 PM CDT WEDNESDAY  
APRIL 26 2017.  
 
ALERTS IN EFFECT... NONE.  
 
SYNOPTIC OVERVIEW... UPPER LOW NEAR HAIDA GWAII WITH TROUGH  
SOUTHEASTWARDS TO A VORT MAX OVER OREGON STATE. SOUTHERN STREAM WELL  
SOUTH OF OUR AREA, ROUNDING THE BASE OF A LONG WAVE TROUGH OVER  
TEXAS AND THEN ROARING BACK NORTHWARD OVER THE GREAT LAKES, FINALLY  
EXITING THE CONTINENT OVER NEWFOUNDLAND. TO THE NORTH OF THIS  
STREAM, THERE IS A QUASI-STATIONARY UPPER LOW OVER EAST-CENTRAL  
ALBERTA AND A WEAK UPPER LOW NEAR FARGO TRACKING NORTHEAST. IN THE  
ARCTIC, SEVERAL UPPER CENTERS COMPRISE A LARGER CYCLONIC CIRCULATION  
COVERING MUCH OF THE EASTERN ARCTIC AND ARCTIC ISLANDS. THERE IS AN  
UPPER LOW NEAR SACHS HARBOUR, ANOTHER OVER SOUTHERN DAVIS STRAIT,  
AND ONE MORE OVER DEVON ISLAND. HILVL JET IN THE ARCTIC STREAM RUNS  
FROM THE MACKENZIE DELTA TO NORTHERN QUEBEC.  
 
AT THE SURFACE, 995 MB LOW OVER NORTHERN HAIDA GWAII WITH TROUGH  
ACROSS CENTRAL BC THEN ALONG THE BC/AB BORDER. LARGE HIGH PRESSURE  
RIDGE STRETCHES FROM SASKATCHEWAN TO NORTHERN QUEBEC WITH A 1033 MB  
CENTRE WEST OF SANIKILUAQ. 995 MB LOW OVER WISCONSIN. 1007 MB LOW  
NORTH OF BAKER LAKE PUSHING EAST-SOUTHEAST. BROAD BUT RATHER WEAK  
AREA OF HIGH PRESSURE COVERS THE BEAUFORT AND MOST OF THE ARCTIC  
ISLANDS. 994 MB LOW OVER SOUTHERN DAVIS STRAIT ASSOCIATED WITH ITS  
UPPER CENTER.  
 
DISCUSSION...  
 
ALBERTA...LIMITED CHANGE WITH UPPER LOW SITTING OVER EAST CENTRAL  
ALBERTA INTO SATURDAY MORNING. WITH EASTERLY SURFACE FLOW AND AMPLE  
RECENT MOISTURE FOG AND STRATUS POSSIBLE TOMORROW MORNING AGAIN  
ALONG THE FOOTHILLS. CONVECTION EXPECTED THIS AFTERNOON AROUND A  
CONVERGENT AREA OVER SOUTHERN AB, WITH LEE LOW FORECAST NEAR  
LETHBRIDGE BY MIDNIGHT. MLCAPES OF 300 TO 500 J/KG AND SHEAR NEAR  
25 KNOTS OVER THE LETHBRIDGE AND CARDSTON REGIONS WITH THUNDERSTORM  
RISK MENTIONED THERE. CBS THAT DEVELOP WILL MOVE VERY SLOW WITH THE  
EFFECTIVE MEAN WINDS BARELY AT 5 KNOTS HENCE THE MODEL PRECIP  
BULLSEYES NEAR 30 MM AROUND THE LEE LOW TONIGHT. TROUGH REMAINS  
ALONG THE MOUNTAINS TONIGHT AND TOMORROW. WITH INSTABILITY, RECENT  
SNOWFALL ON THE GROUND AND QS TROUGH COULD SEE LOCALLY HEAVY  
SNOWFALL.  
 
ERN PRAIRIES... COOL AND UNSETTLED WEATHER, BUT NOTHING SIGNIFICANT  
EXPECTED. SERIES OF LOWS TRACKING THROUGH THE AMERICAN MIDWEST HAS  
THE WESTERN EDGE OF ITS PRECIPITATION SHIELD JUST TICKLING  
SOUTHEASTERN MANITOBA. IT MAY EDGE WESTWARD SLIGHTLY OVER THE NEXT  
DAY OR SO, BUT MANITOBA WILL BE MOSTLY UNAFFECTED BY THIS STORM OVER  
NORTHWESTERN ONTARIO. ALTHOUGH HIGH PRESSURE CIRCULATION DOMINATES  
THE PRAIRIES, THE UPPER LOW OVER EAST-CENTRAL ALBERTA HAS SOME LIGHT  
RAIN AND SNOW ASSOCIATED, WHICH IS AFFECTING PARTS OF SOUTHWESTERN  
SASKATCHEWAN.  
 
ARCTIC... SUB-WARNING SNOWS CONTINUE TODAY AT QIKIQTARJUAQ AND  
PANGNIRTUNG, ALONG WITH SOME BLOWING SNOW AT TIMES AT CLYDE RIVER  
AND IQALUIT, ALL THANKS TO THE RELATIVELY STRONG LOW OVER SOUTHERN  
DAVIS STRAIT. CONDITIONS SHOULD IMPROVE TONIGHT. MEANWHILE, THE WEAK  
LOW NORTH OF BAKER LAKE IS SPREADING A COUPLE OF CM OF SNOW ALONG  
ITS TRACK FROM THE NORTHERN KIVALLIQ EVENTUALLY SPREADING INTO SOUTH  
BAFFIN.  
 
OUTLOOK... MAIN SYSTEM OF CONCERN WILL BE THE LOW WHICH IS OVER  
WISCONSIN TODAY - FORECAST TO SPREAD SNOW OVER SOUTHEASTERN BAFFIN  
ISLAND FRIDAY NIGHT OR SATURDAY, POSSIBLY WARNING AMOUNTS.  
 
END/MELSNESS/ROMBOUGH  
 
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