746  
FOCN45 CWWG 241200  
SIGNIFICANT WEATHER DISCUSSION ISSUED BY THE PRAIRIE AND ARCTIC STORM  
PREDICTION CENTRE OF ENVIRONMENT CANADA AT 7:00 AM CDT WEDNESDAY JULY  
24 2024.  
 
ALERTS IN EFFECT...AIR QUALITY ADVISORIES FOR PARTS OF ALBERTA,  
NORTHWEST TERRITORIES, CENTRAL AND NORTHERN SASKATCHEWAN.  
HEAT WARNINGS FOR PARTS OF ALBERTA, PARTS OF SASKATCHEWAN, PARTS OF  
THE NT AND MOST OF THE KIVALLIQ. RAINFALL WARNING FOR FT LIARD, NT.  
 
SYNOPTIC OVERVIEW...THE 00Z UPPER ANALYSES REVEALED A LOW OVER THE  
WEST COAST WITH A RIDGE OVER SASKATCHEWAN, AND A SOUTHWEST FLOW  
CROSSING THE ROCKIES. ANOTHER LOW WAS OVER DAVIS STRAIT.  
 
THE SURFACE ANALYSIS SHOWS LOW PRESSURE OVER ALBERTA, SOUTHERN NWT,  
AND DAVIS STRAIT. HIGH PRESSURE SITS OVER ONTARIO AND QUEBEC, AS WELL  
AS WESTERN NUNAVUT.  
 
DISCUSSION...  
 
ALBERTA/N SK...DEVELOPING LOW PRESSURE TODAY WILL BRING A SMORGASBORD  
OF HIGH IMPACT WEATHER THROUGH THE END OF THE WEEK, POTENTIALLY  
ENDING THE ONGOING HEAT WAVE WITH A BANG. THE FIRST ORDER OF BUSINESS  
CONCERNS SEVERE CONVECTION IN AB, WHICH BEGAN LAST NIGHT AS A JET  
POKING IN FROM BC LED TO EVENING SUPERCELLS ALONG THE NRN FOOTHILLS.  
OWING TO A HIGH END ENVIRONMENT, THESE STORMS CONTINUED WELL INTO THE  
NIGHT. THIS STRONG UPPER JET WILL PERSIST THROUGH THE DAY AND BE  
AUGMENTED BY AN INTENSE SHORTWAVE PIVOTING AROUND THE BASE OF THE  
UPPER TROUGH, WHICH SHOULD REACH AB BY LATE IN THE DAY. THE LAST  
COUPLE OF OBSERVED SOUNDINGS FROM CWSE STONY PLAIN INDICATE A STOUT  
EML BETWEEN 850 AND 700 MB THAT APPEARS TO HAVE ORIGINATED FROM THE  
HIGH DESERT OF NE OREGON, AN EXPLOSIVE INGREDIENT THAT IS OFTEN  
LACKING IN ALL BUT THE MOST HIGH-END SEVERE EPISODES.  
 
THE OVERALL ENVIRONMENT LOOKS PRIMED FOR SUPERCELLS ONCE AGAIN, WITH  
ALL SEVERE HAZARDS POSSIBLE, INCLUDING TORNADOES AND VERY LARGE HAIL.  
WITH ET APPROACHING ITS SEASONAL LATE-JULY PEAK, DEWPOINTS NEAR 20  
LOOK ATTAINABLE YIELDING MLCAPE ON THE ORDER OF 2000 J/KG OR MORE.  
0-6 KM BWD VALUES OF 50-70 KTS IN CONJUNCTION WITH RM STORM MOTION OF  
25 KTS MEAN THESE WILL LIKELY BE OF THE HP OR CLASSIC VARIETY. AS THE  
PARENT LOW PULLS OFF THE FOOTHILLS, NEAR-SFC WINDS WILL BACK TOWARD  
THE E OR NE AT PERHAPS 10 KTS, YIELDING THOSE SICKLE-SHAPED  
HODOGRAPHS SO COMMON WITH TORNADIC STORMS. THE MAIN TRIGGERS IN THIS  
SCENARIO WILL BE SYNOPTIC LIFT AHEAD OF A DIGGING UPPER TROUGH, AND A  
POSSIBLE EAST-WEST DRYLINE DRAPED ACROSS THE HWY 2 CORRIDOR. SHOULD  
THIS DRYLINE MATERIALIZE AS NWP GUIDANCE SUGGESTS, AND CONVECTION  
FORM ALONG IT, TORNADIC SUPERCELLS ARE LIKELY. TO THE NORTH OF THIS  
BOUNDARY, ADDITIONAL SUPERCELLS ARE ALSO LIKELY, WITH THE TORNADO  
RISK BEING SOMEWHAT LOWER. LARGE HAIL POTENTIALLY EXCEEDING 5 CM IN  
DIAMETER APPEARS TO BE THE MAIN RISK WITH THESE STORMS.  
 
THE MAIN CAVEAT CONCERNING THE ABOVE INVOLVES THICK WILDFIRE SMOKE  
WHICH CONTINUES TO PLAGUE THE PROVINCE. SHOULD FIRES OVER THE ROCKY  
MOUNTAINS BECOME ACTIVE THIS AFTERNOON, LARGE PLUMES OF SMOKE MAY  
INHIBIT CONVECTION UNTIL VERY LATE IN THE DAY. SHOULD THIS BE THE  
CASE, THE TORNADO RISK MAY REMAIN MUTED ALTHOUGH LONG-TRACK SEVERE  
THUNDERSTORMS WILL LIKELY CONTINUE WELL INTO THE NIGHT AS THE PARENT  
LOW TRACKS NE TOWARD LAKE ATHABASCA BY THURSDAY. ANY LATE NIGHT  
CONVECTION IS HIGHLY LIKELY TO EVOLVE INTO MORE OF A WIND THREAT.  
 
THIS LOW WILL ALSO BE THE FOCUS FOR SOME WELCOME RAINFALL ACROSS  
NORTHERN SECTIONS OF THE PROVINCE, WITH WARNING-LEVEL AMOUNTS  
POSSIBLE IN THE BOREAL FOREST REGIONS NORTH OF EDMONTON.  
TOTAL RAINFALL AMOUNTS MAY REACH 50 MM OR MORE BY FRIDAY. SHARPLY  
COOLER TEMPERATURES WILL ACCOMPANY THIS RAINFALL, HELPING TO  
AMELIORATE WIDESPREAD FOREST FIRE SMOKE TO SOME DEGREE. THIS WILL  
LIKELY NOT BE THE CASE ACROSS N SK, WHICH WILL END UP LARGELY IN THE  
WARM SECTOR OF THE LOW. MOST OF THE SMOKE CURRENTLY IN AB IS LIKELY  
TO END UP THERE BY LATE IN THE WEEK.  
 
SOUTHERN SK/MB...THE HEAT WILL CONTINUE TO BUILD EASTWARD LATER THIS  
WEEK AS THE UPPER RIDGE MIGRATES THAT WAY.  
 
MOST OF THE THUNDERSTORM ACTIVITY TODAY IN THE EASTERN PRAIRIES, IF  
ANY, WILL LIKELY BE IN WEST-CENTRAL SASKATCHEWAN, NEAR THE ALBERTA  
BORDER. IF STORMS MAKE IT INTO SASKATCHEWAN (AND THAT'S A BIG IF, DUE  
TO CAPPING), THEY WILL BE ABLE TO TAP INTO AN ENVIRONMENT  
CHARACTERIZED BY MLCAPE OF 2000-3000 J/KG AND BULK SHEAR AROUND 40  
KNOTS. SUPERCELLS WOULD ENSUE, WITH TARGE HAIL AND DAMAGING WINDS THE  
MAIN THREATS. THE TORNADO THREAT IS MINIMAL HERE DUE TO WEAK  
LOW-LEVEL WINDS.  
 
NWT...RAINFALL WARNING CONTINUES FOR FT LIARD AS THE FIRST IMPULSE  
FROM THIS DEEP BC TROUGH PIVOTS WESTWARD ACROSS AREAS ADJOINING THE  
60TH PARALLEL. TOTAL AMOUNTS OF 40-70 MM ARE LIKELY BY THE TIME THIS  
EVENT WRAPS UP BY THIS EVENING, ALTHOUGH GIVEN THE CONVECTIVE NATURE  
OF THIS SYSTEM AMOUNTS WILL BE HIGHLY VARIABLE. ELSEWHERE, AIR  
QUALITY ADVISORIES REMAIN IN PLACE AS THICK FOREST FIRE SMOKE  
CONTINUES TO PLAGUE THE SOUTHERNMOST PORTIONS OF THE TERRITORY.  
AREAS NORTH OF WRIGLEY SHOULD CONTINUE TO SEE A REPRIEVE FROM THE  
SMOKE AS A SOUTHWARD MOVING COLD FRONT PUSHES IT IN THAT DIRECTION.  
 
NUNAVUT...THE DAVIS STRAIT LOW WILL DRAPE A FRONT ACROSS PARTS OF THE  
ARCTIC, BRINGING A BAND OF SHOWERS THAT WILL STRETCH FROM THE  
NORTHERN KIVALLIQ TO SOUTHERN BAFFIN ISLAND. ACCUMULATIONS WILL  
GENERALLY FALL IN THE 5 TO 15 MM RANGE.  
 
END/CARLSEN/VAN LOCHEM  
 
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