244  
FOCN45 CWWG 281900  
SIGNIFICANT WEATHER DISCUSSION ISSUED BY THE PRAIRIE AND ARCTIC STORM  
PREDICTION CENTRE OF ENVIRONMENT CANADA AT 2:00 PM CDT THURSDAY JULY  
28 2016.  
 
ALERTS OR STATEMENTS IN EFFECT...NONE IN EFFECT AT THIS TIME.  
 
THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON AND  
THIS EVENING OVER A LARGE PORTION OF CENTRAL AND SOUTHERN ALBERTA.  
 
SYNOPTIC OVERVIEW...MAIN BELT OF THE WESTERLIES IS IN A RELATIVELY  
ZONAL FLOW OVER SOUTHERN CANADA WITH BROAD WEAK RIDGING IN THE WEST  
AND CORRESPONDING BROAD WEAK TROUGHING IN THE EAST. A SERIES OF WEAK  
VORTICITY MAXIMA CONTINUE TO TRACK FROM SOUTHERN ALBERTA ACROSS THE  
SOUTHWEST CORNER OF SASKATCHEWAN AND INTO THE DAKOTAS. BROAD BUT WEAK  
SURFACE RIDGING STRETCHES WEST TO EAST ACROSS THE SOUTHERN PRAIRIES.  
THERE IS ALSO A 1021 MB HIGH EAST OF FORT RELIANCE WITH A WEAK BROAD  
TROUGH FROM SOUTH OF CHURCHILL TO NORTHERN ALBERTA.  
IN THE ARCTIC, AN UPPER LOW WITH A 1008 MB SURFACE REFLECTION JUST  
SOUTH OF GJOA HAVEN IS TRUNDLING SLOWLY NORTHEASTWARD. A WEAK UPPER  
HIGH SITS OVER THE CUMBERLAND PENINSULA WITH AN UPPER RIDGE ACROSS  
NORTH BAFFIN TOWARDS ULUKHAKTOK. BROAD AREA OF SURFACE HIGH PRESSURE  
COVERS MUCH OF DAVIS STRAIT, BAFFIN BAY, THE HIGH ARCTIC AND  
GREENLAND. LOW OVER ARCTIC OCEAN WITH A TROUGH SOUTHWARD ALONG THE  
MACKENZIE VALLEY.  
 
DISCUSSION...  
 
ALBERTA...A MOIST AND UNSTABLE AIRMASS, EVEN MORE UNSTABLE THAN  
YESTERDAY, WILL SIT OVER A LOT OF ALBERTA TODAY. IN THE ABSENCE OF  
STRONG FORCING, DIFFERENTIAL HEATING BOUNDARIES, LEFTOVER OUTFLOWS  
AND THE MOUNTAIN-PLAINS CIRCULATION WILL LIKELY ALL CONTRIBUTE TO  
CONVECTIVE INITIATION. AS THE AIRMASS WILL BE LARGELY UNCAPPED, A  
FAIRLY EARLY (NOONISH) START TO THE ACTION IS ANTICIPATED, AGAIN MUCH  
LIKE YESTERDAY. 1500 TO 2500 J/KG MLCAPE WILL BE COMMON, AND SHEAR  
WILL VARY FROM 25 TO 35 KNOTS. THE MOST LIKELY SCENARIO IS FOR STORMS  
TO FIRE OFF THE FOOTHILLS AND THEN MOVE EASTWARD, WITH ADDITIONAL  
INITIATION OCCURRING IN POCKETS ALL OVER THE PROVINCE. COVERAGE AND  
INTENSITY SHOULD PEAK IN THE MID TO LATE AFTERNOON, WITH HEAVY RAIN  
AND HAIL TO THE SIZE OF LOONIES THE MAIN THREATS. FUNNEL CLOUDS OR  
AN ISOLATED LANDSPOUT ARE POSSIBLE ESPECIALLY UNDER QUICKLY-GROWING  
UPDRAFTS THAT CAN TAP INTO AND STRETCH EXISTING VORTICITY. THE  
RELATIVE MAXIMIUM IN ACTIVITY, WITH THE MOST FAVOURABLE  
JUXTAPOSITION OF INSTABILITY AND SHEAR, IS EXPECTED TO BE IN AN AREA  
BOUNDED BY WHITECOURT, EDMONTON AND OLDS.  
 
FRIDAY WILL BE ANOTHER MODERATE CAPE AND LOW TO MODERATE SHEAR DAY  
ACROSS THE PROVINCE. AREAS SOUTH OF CALGARY WILL HAVE STRONGER SHEAR,  
AROUND 35 KNOTS, SO SEVERE STORMS ARE MOST LIKELY THERE.  
 
IN THE MEDIUM TERM, SATURDAY RATES A MENTION AS A FAIRLY ENERGETIC  
SHORT WAVE TROUGH WILL APPROACH ALBERTA. AS JET + ALBERTA = BAD, A 60  
TO 80 KNOT H25 JET FORECAST TO NOSE INTO THE REGION OVERTOP A MOIST  
AND UNSTABLE AIRMASS WILL MAKE FOR SUPERCELLS FOR ABOUT THE SOUTHERN  
HALF OF ALBERTA, WITH ALL MODES OF SEVERE WEATHER LIKELY.  
 
EASTERN PRAIRIES...WEAK BROAD TROUGH WILL GIVE SCATTERED NON-SEVERE  
THUNDERSTORMS OVER CENTRAL AND PORTIONS OF NORTHERN SASKATCHEWAN AND  
MANITOBA. THE FAR NORTH SHOULD ESCAPE WITHOUT DEEP CONVECTION, AS  
WILL MUCH OF THE SOUTH WHERE MORE STABLE AIR UNDER THE RIDGE WILL  
PREDOMINATE. SBCAPE IN THE 1000 TO 1300 J/KG RANGE OVER  
SASKATCHEWAN'S NORTHERN GRAINBELT THIS AFTERNOON AND INTO  
WEST-CENTRAL MANITOBA, HOWEVER 0-6 KM SHEAR IS ONLY AROUND 15 KNOTS.  
DUE TO THE WEAK FLOW PATTERN, SOME THUNDERSTORMS STILL HAVE THE  
POTENTIAL TO PRODUCE LOCALIZED RAINFALLS OF 20+ MM. ALSO HAVE TO BE  
WARY OF THE POTENTIAL FOR BRIEF FUNNEL CLOUDS DURING CONVECTIVE  
DEVELOPMENT IN THE LATE MORNING THRU AFTERNOON HOURS.  
 
EASTERN ARCTIC...SOME RAIN FOR PORTIONS OF NORTHERN QIKIQTAALUK  
ASSOCIATED WITH APPROACHING GJOA HAVEN LOW, OTHERWISE QUIET APART  
FROM SOME OF THE USUAL ONSHORE FOG AND STRATUS ISSUES.  
 
WESTERN ARCTIC...WINDS WILL BE GUSTY FROM THE SOUTH AT SACHS HARBOUR,  
BUT OTHERWISE IT'LL BE FAIRLY QUIET THIS FORECAST PERIOD.  
 
END/FULTON/MACKAY  
 
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