WATCHES, WARNINGS, AND STATEMENTS... RAINFALL WARNING FOR WEST-CENTRAL ALBERTA. SEVERE THUNDERSTORM WATCH FOR MUCH OF CENTRAL ALBERTA EXTENDING INTO WEST-CENTRAL SASKATCHEWAN.
DISCUSSION... AN APPROACHING UPPER TROUGH NOW COMING ASHORE OVER THE US PACIFIC NORTHWEST WILL HELP TO INITIATE THUNDERSTORMS OVER CENTRAL ALBERTA THIS AFTERNOON, WHICH WILL TRACK INTO MORE FAVOURABLE MOISTURE IN WESTERN SASKATCHEWAN. A SOUTH TO SOUTHEASTERLY FLOW IS FEEDING MOISTURE FROM EASTERN MONTANA AND THE WESTERN DAKOTAS UP TOWARDS THE BATTLEFORDS. EXPECT THE MAIN FOCUS FOR CONVECTION THIS AFTERNOON TO BE ALONG A WEST TO EAST WARM FRONT LIFTING SLOWLY NORTHWARD AROUND SASKATOON. SBCAPE EXPECTED IN THE 2000 TO 3000 J/KG RANGE IN THE WARM AIRMASS JUST SOUTH OF THE WARM FRONT, WITH A STRONGLY VEERING HODOGRAPH FROM THE SURFACE TO 3 KM, ALBEIT WITH RELATIVELY LIGHT WINDS IN THE 15 TO 20 KT RANGE.
WHILE SEVERE THUNDERSTORMS ARE LIKELY IN WEST-CENTRAL SASKATCHEWAN, THEY SHOULD NOT EXTEND THROUGH THE NIGHT AS THEY TRACK EASTWARD AWAY FROM THE MOST FAVOURABLE LOW LEVEL JET. MEANWHILE IN ALBERTA, THE SURFACE LOW IS EXPECTED TO INTENSIFY TONIGHT WITH RAINFALL RATES INCREASING OVER WEST-CENTRAL REGIONS MODELS ARE CONSISTENLY FORECASTING OVER 100 MM THROUGH THE GRANDE PRAIRIE AND WHITECOURT AREAS. THE WATCH FOR WHITECOURT WILL BE SWITCHED TO A RAINFALL WARNING TONIGHT AFTER TRW WEAKEN AND RED EARTH MAY NEED TO BE ADDED WITH COMING UPDATES.
ALBERTA FOOTHILLS WILL ALSO BECOME ACTIVE FOR TRW BEST MOISTURE EXISTS NORTH OF CALGARY WITH DRYING WESTERLY WINDS OVER THE SOUTHERN FOOTHILLS. BEST SHEAR IS NEAR THE ELBOW WITH THE 500 MB JET AND SFC EATERLY WINDS. SUPERCELLS ARE EXPECTED TO DEVELOP AND TRACK EASTWARDS INTO THE EVENING.
LITTLE IN THE WAY OF SIGNIFICANT WEATHER IN THE ARCTIC TODAY. A SLOW MOVING VERTICAL LOW JUST EAST OF RESOLUTION ISLAND IS THE MAIN WEATHER MAKER, GIVING RAIN AND DRIZZLE TO MUCH OF EASTERN BAFFIN. AS THE LOW TRACKS NORTHWARDS STRONG NORTHERLY WINDS ARE EXPECTED TO DEVELOP AT TIMES IN GRISE FIORD SATURDAY.
ON FRIDAY, THE BEST SEVERE WEATHER THREAT WILL SHIFT INTO SOUTHEASTERN SASKATCHEWAN, POSSIBLY EXTENDING INTO SOUTHERN MANITOBA FRIDAY NIGHT AS THE LOW LEVEL JET SHOULD BE MORE FAVOURABLE ALONG WITH THE AFOREMENTIONED UPPER TROUGH LENDING SUPPORT.
END/MELSNESS/WIELKI
SIGNIFICANT WEATHER DISCUSSION ISSUED BY THE PRAIRIE AND ARCTIC STORM PREDICTION CENTRE OF ENVIRONMENT CANADA AT 7:00 AM CDT FRIDAY JULY 8 2011.
WATCHES, WARNINGS, AND STATEMENTS...RAINFALL WARNING FOR WEST-CENTRAL ALBERTA.
THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON AND THIS EVENING OVER PORTIONS OF SOUTHEAST SASKATCHEWAN AND TONIGHT IN SOUTHERN MANITOBA.
OVERVIEW...THE 00Z UPPER ANALYSES AND WATER VAPOUR IMAGERY REVEALED A POTENT NEGATIVELY-TILTED UPPER TROUGH OVER SOUTH-CENTRAL BRITISH COLUMBIA, VERY CLOSE TO CUTTING OFF. NOT MUCH ELSE OF CONSEQUENCE WAS NOTED. THE 06Z SURFACE ANALYSIS REVEALED A LOW PRESSURE SYSTEM OVER SOUTH-CENTRAL ALBERTA WITH A WARM FRONT EXTENDING MORE OR LESS EASTWARD FROM IT. ALSO OF NOTE WERE NUMEROUS OUTFLOW BOUNDARIES FROM DECAYING AND ONGOING CONVECTION OVER ALBERTA AND SASKATCHEWAN.
DISCUSSION...TODAY WILL BE AN INTERESTING DAY FOR SASKATCHEWAN, AS A SYNOPTICALLY-EVIDENT SETUP FOR A SEVERE WEATHER OUTBREAK IS NEARBY. WIND SHEAR, BOTH DEEP AND LOW-LEVEL, WILL BE IDEAL FOR SUPERCELLS WITH LOW-LEVEL ROTATION WITHIN THEM. FORECAST HODOGRAPHS SHOW SUBSTANTIAL LOOPING AND UPDRAFTS SHOULD HAVE GOOD VENTILATION FROM 40 KNOT MIDLEVEL WINDS. MOISTURE, CHARACTERIZED BY SURFACE DEWPOINTS IN THE UPPER TEENS, WILL BE PLENTIFUL EAST OF A SURFACE TROUGH, FORECAST TO BE THROUGH THE SASKATOON, MOOSE JAW AND ASSINIBOIA REGIONS BY 09/00Z. THE TROUGH WILL PROVIDE PLENTIFUL LIFT FOR CONVECTIVE INITIATION. THE QUESTION ABOUT STORM STRENGTH, THEN, WILL BE ON CLOUD COVER. IF THE REGION STAYS CLOUDY DUE TO ONGOING CONVECTION, STORMS WILL NOT LIKELY BE PARTICULARLY VIOGOROUS, WITH MLCAPES BELOW 1000 J/ KG. HOWEVER, 2 HOURS OF SUN SHOULD BE GOOD ENOUGH FOR MLCAPES IN EXCESS OF 2000 J/KG. SHOULD THIS SCENARIO UNFOLD, SUPERCELLS WITH LARGE HAIL WILL OCCUR AND A FEW TORNADOES WILL BE LIKELY FOR A FEW HOURS BEFORE THE STRONG FORCING PROMOTES GROWTH OF THE STORMS INTO ONE OR MORE BROKEN LINES. THIS WILL BEAR CLOSE MONITORING AND IF INSTABILITY RISES HIGHER THAN CURRENTLY ANTICIPATED, A MODERATE RISK WILL BE NEEDED. AS IT SITS RIGHT NOW, MOST OPERATIONAL MODEL RUNS ARE PORTRAYING EXTENSIVE CLOUD COVER NORTH OF THE 49TH PARALLEL, GIVING RISE TO LOWER-END COVERAGE OF SEVERE THUNDERSTORMS SOUTH OF THE YELLOWHEAD AND EAST OF HIGHWAY 11.
HOWEVER THE SCENARIO UNFOLDS, THE POTENCY OF THE UPPER TROUGH WILL PROMOTE RESPONSE OF THE WIND FIELDS THROUGH THE TROPOSPHERE, GIVING PLENTY OF FORCING AND SHEAR FOR THUNDERSTORMS THROUGH THE NIGHT. THE LOW-LEVEL JET IS FORECAST TO STRENGTHEN TO 35 KNOTS OR HIGHER. ALONG WITH MIDLEVEL WINDS APPROACHING 50 KNOTS, THIS WILL SUPPORT NOCTURNAL THUNDERSTORMS WITH OCCASIONAL LARGE HAIL EASTWARD INTO MOST OF SOUTHERN MANITOBA.
OTHERWISE, THE EASTERN PRAIRIES AND EASTERN ARCTIC WILL BE QUIET THIS FORECAST PERIOD.
SFC LOW OVER SRN ALBERTA WILL DRIFT NWD TDA AND BECOME VERTICAL THROUGH ALL LEVELS VICINITY WHITECOURT BY 00Z WITH WRM FNT EWD AND COLD FNT SEWD FROM LOW. SIGNIFICANT MOISTURE N OF WRM FNT AND NW OF LOW SUPPORTS MODEL SOLUTION WITH 50 PLUS MM RAIN OVER REGIONS IN NW QUADRANT OF LOW. EXPECT SOME IMPROVEMENT SATURDAY AS LOW MOVES EWD INTO SK. LOCALLY HEAVIER AMOUNTS POSSIBLE N OF WRM FNT WITH EMBDD CONVECTION EXPECTED.
BRISK NELY WINDS EXPECTED TO CONTINUE FOR RESOLUTE AS STG HIGH OVER ARCTIC OCEAN COMBINES WITH AREA OF LOW PRESSURE OVER BAFFIN ISLAND TO GENERATE STG ELY GRADIENT OVER CNTRL ARCTIC ISLANDS. WINDS EXPECTED TO REMAIN SUB WARNING.
END/CARLSEN/MACKAY
SIGNIFICANT WEATHER DISCUSSION ISSUED BY THE PRAIRIE AND ARCTIC STORM PREDICTION CENTRE OF ENVIRONMENT CANADA AT 2:00 PM CDT FRIDAY JULY 8 2011.
WATCHES, WARNINGS, AND STATEMENTS... RAINFALL WARNING FOR WEST-CENTRAL ALBERTA. SEVERE THUNDERSTORM WATCH FOR EASTERN SASKATCHEWAN, WHICH MAY ALSO BE EXTENDED INTO SOUTHERN MANITOBA LATER TODAY. SEVERE THUNDERSTORM WATCH FOR FORT MCMURRAY AND BUFFALO NARROWS, WHICH MAY BE EXTENDED TOWARDS SLAVE LAKE LATER TODAY.
OVERVIEW... AT 12Z, THE UPPER ANALYSES SHOWED A STRONG UPPER TROUGH PUSHING EWD THRU THE NWRN US AND SRN BC. 990 MB SFC LOW NEAR SLAVE LAKE CONTINUES TO DEEPEN AS IT CURLS NORTHWESTWARD AND SHOULD SOON BE CAPTURED. FAIRLY WELL DEFINED COLD FRONT WHICH PUSHED THROUGH SOUTHERN ALBERTA OVERNIGHT IS, AS OF 18Z ROUGHLY FROM A MEADOW LAKE TO EAST OF SASKATOON TO ROCKGLEN LINE. AHEAD OF THIS FRONT, STRONG LIFT IS TRIGGERING SCATTERED THUNDERSTORMS. WHILE CONSIDERABLE CLOUDINESS IS INHIBITING THUNDERSTORMS SOMEWHAT, THERE SEEMS TO BE ENOUGH CLEARING BEFORE THE COLD FRONT THAT DAYTIME HEATING SHOULD BRING MLCAPES INTO THE 2000 J/KG RANGE. WATER VAPOUR IMAGERY SHOWS A SHORTWAVE TROUGH PUSHING NORTHEASTWARD THRU MONTANA TOWARDS ESTEVAN, WHICH SHOULD CONTINUE TO ENHANCE THE SHOWERS AND TSTMS FORMING OVER THAT AREA THROUGHOUT THE DAY. HEAVY RAIN IS OF CONCERN IN THE FLOOD PLAGUED SE SK AND SW MB TODAY AND TONIGHT, AS THE SHORTWAVE WILL BE TAPPING INTO DEEP MOISTURE ALREADY IN PLACE. WITH A STRONGER LLJ FORECAST INTO SOUTHERN MB TONIGHT, EXPECT TSTMS TO BE A BIT MORE PERSISTANT THAN LAST NIGHT.
HEAVY RAIN CONTINUES THROUGH NORTHERN ALBERTA WITH AMOUNTS UP TO 94 MM REPORTED IN SLAVE LAKE. RAIN HERE WILL CONTINUE INTO SATURDAY WITH A FURTHER 50 TO 100 MM EXPECTED. UNDER THE UPPER LOW POTENTIAL FOR FUNNEL CLOUDS TODAY. A LINE OF TRW HAVE ALREADY DEVELOPED ALONG A CONVERGENCE LINE FROM SLAVE LAKE TOWARDS BUFFALO NARROWS. BY DAYS END CAPES ARE NEAR 1500 J/KG. SOUTH OF THE LOW A STRONG GRADIENT AND LLJ OF 68 KNOTS WILL GIVE STRONG WINDS. OUR MAIN CONCERN IS THROUGH THE STONY PLAIN TO GRANDE PRAIRIE AREA WHERE THE LOW LEVEL JET AXIS WILL SIT THIS EVENING.
IN THE ARCTIC, LITTLE IN THE WAY OF SIG WX TODAY. QIKIQTAALUK CONTINUES TO BE PLAGUED BY SHOWERS, DRIZZLE, AND FOG.
END/MELSNESS/WIELKI
SIGNIFICANT WEATHER DISCUSSION ISSUED BY THE PRAIRIE AND ARCTIC STORM PREDICTION CENTRE OF ENVIRONMENT CANADA AT 7:00 AM CDT SATURDAY JULY 9 2011.
WATCHES, WARNINGS, AND STATEMENTS...RAINFALL WARNING FOR WEST-CENTRAL ALBERTA.
OVERVIEW...THE 00Z UPPER ANALYSES REVEALED A DEEP-TROPOSPHERIC LOW NEAR EDMONTON AND A RIDGE AHEAD OF IT, OVER CENTRAL CANADA AND THE CENTRAL UNITED STATES. THE 06Z SURFACE ANALYSIS REVEALED A 991 MB LOW JUST EAST OF EDMONTON. WARM AND COLD FRONTS EMANATED FROM THIS LOW, WITH THE WARM SLICING SOUTHEAST ACROSS SOUTH-CENTRAL MANITOBA AND THE COLD CUTTING SOUTHWARD THROUGH SOUTHERN SASKATCHEWAN; IN ADDITION, A PRE-FRONTAL TROUGH, THE FOCUS FOR SEVERE THUNDERSTORMS LAST NIGHT, SAT IN BETWEEN. THE WARM SECTOR WAS CHARACTERIZED BY SURFACE DEWPOINTS IN THE MID TO UPPER TEENS. ELSEWHERE, A FLAT PRESSURE PATTERN DOMINATED.
DISCUSSION...THUNDERSTORMS ONGOING DURING THE LATE OVERNIGHT HOURS, FORCED BY THE COLD FRONT, WILL LIKELY MAINTAIN THEMSELVES IN A DISORGANIZED FASHION THROUGH MOST OF THE MORNING AS THEY RUMBLE ACROSS SOUTHERN MANITOBA. DESPITE MODERATE MOISTURE ADVECTION ATOP A NIGHTTIME INVERSION, MUCAPES ARE STRUGGLING TO TOP 500 J/KG. AS A RESULT, STORMS ARE REMAINING SUB-SEVERE OR MARGINALLY-SEVERE AT WORST. AS THE COLD FRONT MOVES EASTWARD, WE EXPECT SCATTERED THUNDERSTORMS ALONG AND AHEAD OF IT. THE TIMING OF THE FRONT, HOWEVER, WILL BE SUCH THAT STORMS CANNOT TAP INTO PEAK HEATING IN THE WARM SECTOR. THUS, WITH 500 MB WIND SPEEDS IN THE 40 TO 50 KNOT RANGE, AT WORST WE EXPECT MARGINALLY-SEVERE STORMS IN THE FAR EASTERN PARTS OF MANITOBA.
THE STACKED LOW MENTIONED ABOVE IS FORECAST TO MOVE EASTWARD THROUGH CENTRAL SASKATCHEWAN TODAY. SYSTEM CLOUD ASSOCIATED WITH THIS FEATURE IS BLANKETING NORTHERN MANITOBA AND SASKATCHEWAN AND WRAPPING AROUND OVER ALL BUT THE SOUTHERN TIP OF ALBERTA. RAINFALL WARNINGS HAVE BEEN PARED BACK THIS MORNING TO INCLUDE ONLY THE PEACE RIVER, GRAND PRAIRIE AND HINTON - GRANDE CACHE REGIONS WHERE AN ADDITIONAL 10 TO 15 MM OF RAIN ARE EXPECTED TODAY. BANDS OF EMBEDDED SHOWERS AND A FEW THUNDERSTORMS WILL OCCUR IN WRAP AROUND BANDS CLOSER TO THE LOW. A CLOSE EYE WILL HAVE TO BE KEPT ON CLOUD EDGES ALONG ANY DRY SLOTS OR OTHER OPEN AREAS IN AND JUST SOUTH OF THE MAIN CLOUD SHIELD, WHERE PROLONGED INSOLATION COULD RESULT IN MLCAPES OF 800 TO 1000 J/KG. 6KM BULK SHEARS IN THE STRONGER EAST TO NORTHEASTERLY FLOW NORTH AND WEST OF THE LOW ARE EXCEEDING 30 KNOTS FOR MOST OF THE DAY TODAY THUS SUGGESTING AT LEAST A RISK OF SOME STRONGER LONG-LIVED CELLS DEVELOPING AS EARLY AS MIDDAY. CLOSER TO THE LOW, WHERE SHEARS WON'T BE AS GREAT, ANY AXIS OF FOCUSED LOW LEVEL CONVERGENCE COULD BE THE SITE OF A NON-SUPERCELL FUNNEL.
TO THE SOUTHWEST OF THE LOW, THE WESTERLY LOW LEVEL JET HAS WEAKENED SOMEWHAT SINCE YESTERDAY, BUT GUSTS IN THE 50 TO 70 KM/H RANGE CONTINUE TO BE INCLUDED IN THE REGIONAL FORECASTS OVER MUCH OF SOUTHERN ALBERTA.
ELSEWHERE IN THE PRAIRIES AND OVER THE ENTIRE ARCTIC, THE WEATHER IS EXPECTED TO BE BENIGN.
SUNDAY MAY HAVE SOME SEVERE STORMS IN SOUTHERN MANITOBA SOUTH OF THE TRANS-CANADA, AS ANOTHER UPPER IMPULSE INFLUENCES THE REGION IN THE AFTERNOON. CAPE AND SHEAR VALUES WOULD SUPPORT SUPERCELLS WITH LARGE HAIL AND DAMAGING WIND GUSTS.
END/CARLSEN/SCHMIDT SIGNIFICANT WEATHER DISCUSSION ISSUED BY THE PRAIRIE AND ARCTIC STORM PREDICTION CENTRE OF ENVIRONMENT CANADA AT 2:00 PM CDT SUNDAY JULY 10 2011.
WATCHES, WARNINGS, AND STATEMENTS...STRONG WIND WARNING FOR LAKE WINNIPEG NORTH BASIN.
DISCUSSION...NEARLY VERTICAL LOW OVER WEST CENTRAL MANITOBA CONTINUES TO TRACK EASTWARD ACROSS CENTRAL MANITOBA. FRONTAL WAVE PULLING EASTWARD THRU NORTHWESTERN ONTARIO WITH TROWAL/TROF HANGING BACK OVER PORTIONS OF CENTRAL AND CENTRAL SK/NRN MB. ISOLATED THUNDERSTORM ACTIVITY ALONG THE TROWAL/TROF BROUGHT SIGNIFICANT DOWNPOURS IN TSTMS EARLY THIS MORNING TO THE GILLAM AREA. AUTO STATION AT GILLAM REPORTED 37.2 MM OVER 2 HOURS EARLY THIS MORNING WITH NEAR 50 MM FALLING OVER A 24 HOUR PERIOD. RAINFALL WARNING WAS ISSUED FOR THE AREA BUT HAS SINCE BEEN ENDED. FOR THE REMAINDER OF THE DAY EXPECT SCATTERED THUNDERSTORMS AS THE UPPER LOW PUSHES THRU CENTRAL MANITOBA DURING PEAK HEATING HOURS. THERE MAY BE A SLIGHT RISK OF COLD CORE FUNNELS THIS AFTN VCNTY OF THE UPR LOW AND TROF LN.
SOUTHERN PRAIRIES WILL REMAIN GENERALLY SUNNY AND SEASONABLY WARM TODAY WHILE THE NORTH IS CLOUDY AND DAMP, ON THE SOUTHERN EDGE OF THE NORTHERN CLOUD SHIELD, IN THE VICINITY OF A SURFACE TROUGH/TROWAL, SOUTHEASTERN MANITOBA MAY SEE AN ISOLD TSTM OR TWO LATE THIS AFTN/ EVNG, SHEAR IS RELATIVELY STRONG WITH THE CORRESPONDING SBCAPE RANGING FROM UNDER 1000 J/KG IN THE NRN RRV TO 2000-2500 J/KG IN THE SRN RRV WHERE T/TD OF 30/18 ARE EXPECTED. WEAK WWA OVER THE REGION MAY BE ENOUGH TO CAP CONVECTION HOWEVER ANY LOW LVL CONVERGENCE BOUNDARIES IN THE AREA MAY BE ENOUGH TO OVERCOME THIS. LATEST SFC ANALYSIS INDICATES WEAK CONVERGENCE ALONG THE MB ESCARPMENT WHERE LIGHT SLY FLOW IS MEETING A W/SWLY FLOW. WILL CONTINUE TO MONITOR AND WATCHES MAY BE REQUIRED. WX BALLOON WILL BE LAUNCHED LATER THIS AFTN FM XWN TO ACCESS THE CAP. ATTM ELEVATED STORMS HAVE DEVELOPED OVER WRN DAKOTA IN THE RT JET ENTERANCE AREA BUT THESE STORMS SHUD REMAIN SOUTH OF THE INTERNATIONAL BOUNDARY.
TO THE WEST OF THE LOW, A Q-S BAND OF RAIN EXTENDS FROM AB PEACE COUNTRY SOUTHEAST TO SK ALONG DEFORMATION ZONE. THE GREATEST AMOUNTS OF 10 TO 20 MM LOOK TO FALL OVER WEST CENTRAL AB TODAY AND TOMORROW - LIKELY AGGRAVATING THE FLOODING SITUATION OVER THE ALREADY SATURATED REGIONS.
FURTHER SOUTH ALONG THE FOOTHILLS, A FEW THUNDERSTORMS ARE LIKELY THIS EVENING WITH THE APPROACH OF A WEAK SHORTWAVE FROM THE WEST. MLCAPES ARE NOT EXPECTED TO EXCEED 500 J/KG AND SHEAR WILL BE MINIMAL UNDER A SLACK FLOW ALOFT RESULTING IN NON-SEVERE PULSE STORMS. THE PATTERN IS SETTING UP SUCH THAT THUNDERSTORMS MAY BE MORE SAVAGE ON MONDAY BUT CLOUD COVER AND COLD DEW POINTS MAY KEEP STORMS AT BAY.
IN THE ARCTIC, NIL SIG WX.
END/RUSSO/MARK
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