609
FOCN45 CWWG 221900
SIGNIFICANT WEATHER DISCUSSION ISSUED BY THE PRAIRIE AND ARCTIC STORM
PREDICTION CENTRE OF ENVIRONMENT CANADA AT 2:00 PM CDT TUESDAY AUGUST
22 2017.
ALERTS IN EFFECT...NONE.
SYNOPTIC OVERVIEW...UPPER RIDGE OVER WESTERN CANADA WITH NORTH TO
SOUTH SURFACE RIDGE OVER EASTERN SK. WEAK VORT MAX EMBEDDED IN THE
THE RIDGE NEAR LAKE ATHABASCA. NEARLY VERTICAL LOW JUST SOUTHWEST OF
JAMES BAY WITH SURFACE TROUGH WESTWARD FROM LOW. STACKED LOW OVER
BAFFIN BAY, WITH TROF EXTENDING SOUTHWESTWARD INTO NORTHERN HUDSON
BAY. STACKED LOW MAKING LANDFALL IN THE ALASKA PANHANDLE.
DISCUSSION...
PRAIRIES...VORTMAX OVER LAKE ATHABASCA WILL TRIGGER THUNDERSTORMS
OVER NORTHERN SK. LOOKS LIKE A PRETTY GOOD SETUP FOR FUNNEL CLOUDS IN
THE REGION AS SURFACE WINDS REMAIN LIGHT AND SUFFICIENT LOW LEVEL
VORTICITY WITH THE VORT MAX. A FEW NON-SEVERE THUNDERSTORMS ARE
POSSIBLE THIS AFTERNOON ALONG THE ALBERTA FOOTHILLS WITH
DIFFERENTIAL HEATING. COLD AIR ALOFT OVER SOUTHERN MB WITH 500 MB
TEMPS BELOW -20C AND WITH CONVERGENCE ALONG TROUGH WILL SEE
CONSIDERABLE CU/TCU OVER MUCH OF MB TODAY AND MAY SEE SOME LOW
TOPPED CB'S OVER SOUTHEAST MB WHERE SLIGHTLY BETTER THERMODYNAMICS
EXIST AS WELL AS ENHANCED CONVERGENCE WITH LAKES CONVERGENE.
CONVECTION SHOULD DISSIPATE RATHER QUICKLY THIS EVENING WITH LOSS OF
DAYTIME HEATING.
WEDNESDAY SHOULD SEE A RETURN OF MORE SUBSTANTIAL THUNDERSTORMS IN
ALBERTA FROM CALGARY TO GRANDE PRAIRIE. DEPENDING ON MOISTURE
AVAILABILITY, MLCAPE OF 1000 TO 2000 J/KG AND DEEP-LAYER SHEAR OF 40
KNOTS WILL LEAD TO A FEW SUPERCELLS CAPABLE OF LARGE HAIL AND
DAMAGING WINDS.
ARCTIC...NORTHERLY FLOW OVER JONES SOUND GIVES POTENTIAL FOR GUSTY
WINDS POSSIBLY UP TO 80 KM/H LATER THIS AFTERNOON AND TONIGHT IN
GRISE FIORD ALTHOUGH INVERSION MAY BE A BIT HIGH. OTHERWISE, SOME
COASTAL FOG ALONG ARCTIC COASTLINE AND BAFFIN ISLAND EAST COAST
ESPECIALLY TONIGHT AND WEDNESDAY MORNING.
END/MCDONALD/NISKA-ARO
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