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FOCN45 CWWG 171230
SIGNIFICANT WEATHER DISCUSSION ISSUED BY THE PRAIRIE AND ARCTIC STORM
PREDICTION CENTRE OF ENVIRONMENT CANADA AT 7:00 AM CST TUESDAY
DECEMBER 17 2024.
ALERTS IN EFFECT...BLIZZARD WARNING FOR CLYDE RIVER. SNOWFALL WARNING
FOR WESTERN ALBERTA. FOG ADVISORY FOR SOUTHERN ALBERTA.
SYNOPTIC OVERVIEW...ALOFT, AN UPPER LOW LIES OVER THE GULF OF ALASKA
WITH A NEGATIVELY TILTED TROUGH SOUTHEASTWARD TO THE COAST OF
WASHINGTON. UPPER LOWS ALSO LIE OVER ALASKA, YUKON, NORTHERN
SASKATCHEWAN, NORTHWESTERN ONTARIO AND FOXE BASIN. AN UPPER RIDGE
LIES ACROSS THE BC COAST INTO SOUTHERN ALASKA.
AT THE SURFACE, HIGH PRESSURE LIES ACROSS THE NWT WITH RIDGING
SOUTHWARD INTO ALBERTA AND SOUTHERN SASKATCHEWAN. A 997 MB LOW LIES
NEAR JAMES BAY AND A COMPACT 988 MB LOW LIES OVER DAVIS STRAIT.
DISCUSSION...
AB...STRATUS BLANKETS MUCH OF CENTRAL AND SOUTHERN ALBERTA THIS
MORNING, WITH SOME POOR VISIBILITY BEING OBSERVED ON WEBCAMS. A FOG
ADVISORY REMAINS IN EFFECT FOR PARTS OF SOUTHERN ALBERTA AT THIS
TIME, ALTHOUGH THE FOG APPEARS TO BE LESS WIDESPREAD THAN YESTERDAY
EVENING. HOWEVER, THE STRATUS DECK WILL LIKELY REMAIN OVER THE REGION
UNTIL THERE IS A SHIFT IN THE PATTERN.
SPEAKING OF WHICH, A PACIFIC LOW IS SET TO MOVE THROUGH SOUTHERN
ALBERTA AND NORTHERN MONTANA, BRINGING SNOWFALL TO SOUTHERN AND
CENTRAL ALBERTA TONIGHT AND WEDNESDAY. SNOWFALL WILL BEGIN TONIGHT
OVER PARTS OF WESTERN ALBERTA, AND SPREAD EASTWARD THROUGH WEDNESDAY
MORNING. SNOWFALL TOTALS WILL BE HIGHEST FROM HINTON/GRANDE PRAIRIE
THROUGH EDMONTON AND EAST/SOUTHEAST TOWARD LLOYDMINSTER AND MEDICINE
HAT. NWP GUIDANCE OVER THE PAST 24-36 HOURS HAD BEEN SHIFTING THE
HIGHEST SNOWFALL TOTALS SOUTHEASTWARD, WELL INTO SASKATCHEWAN, BUT
THAT TREND HAS REVERSED. AT THIS TIME, AMOUNTS OF ROUGHLY 8-15 CM ARE
EXPECTED, WITH MANY REGIONS APPROACHING WARNING CRITERIA FOR THE
WEDNESDAY DAYTIME PERIOD. A SNOWFALL WARNING HAS BEEN ISSUED FOR
HINTON, WITH THE EXPECTATION THAT IT COULD POSSIBLY BE EXPANDED
EASTWARD AS NWP GUIDANCE CONVERGES ON A STABLE SOLUTION FOR THIS
SYSTEM.
SK/MB...PLENTY OF REMNANT STRATUS OVER THE EASTERN PRAIRIES THAT
SHOULD GRADUALLY CLEAR THROUGH THE DAY ON TUESDAY.
AS THE ARCTIC RIDGE OF HIGH PRESSURE BUILDS SOUTHEASTWARD ON TUESDAY
NIGHT TEMPERATURES WILL FALL TO THE MINUS THIRTY DEGREE MARK.
COMBINED WITH WINDS OF 15 TO 20 KM/H, EXTREME WIND CHILLS ARE LIKELY
ACROSS PORTIONS OF SOUTHERN SASKATCHEWAN BY WEDNESDAY MORNING.
THIS WILL BE HIGHLY CONTINGENT ON HOW MUCH CLEARING OCCURS ACROSS
SASKATCHEWAN TODAY WITH THE HIGHEST LIKELIHOOD FOR EXTREME WIND
CHILLS OVER WEST CENTRAL REGIONS BUT SOUTHERN REGIONS COULD ALSO SEE
NEAR -40 WIND CHILLS IF SUFFICIENT CLEARING OCCURS. EXTREME COLD
WARNINGS ARE LIKELY FORTHCOMING THIS AFTERNOON FOR SOME REGIONS.
ATTENTION QUICKLY TURNS TO WEDNESDAY, WHEN ANOTHER SYSTEM WILL
DEVELOP IN THE LEE OF THE ALBERTA ROCKIES AND MAKE ITS WAY ACROSS THE
SOUTHERN PRAIRIES, BRINGING WARNING LEVEL SNOWFALL TO PARTS OF
SASKATCHEWAN WEDNESDAY AND WEDNESDAY NIGHT. THIS SYSTEM WILL CONTINUE
INTO SOUTHWESTERN MANITOBA EARLY THURSDAY MORNING BRINGING
POTENTIALLY WARNING LEVEL SNOWFALL TO THE REGION. THERE IS ALSO THE
RISK OF FREEZING RAIN/FREEZING DRIZZLE OVER SOUTHEASTERN AB AND
SOUTHWESTERN SASKATCHEWAN WITH THIS SYSTEM AS WELL AS SNOW/BLOWING
SNOW OVER SOUTHEASTERN SASKATCHEWAN WEDNESDAY. ALERTS WILL BE ISSUED
AS TIME APPROACHES AND THE SYSTEM'S TRACK BECOMES CLEARER.
ARCTIC...A POLAR LOW LOOKS TO DEVELOP OVER CENTRAL DAVIS STRAIT COME
TUESDAY. GUIDANCE HAS BEEN CONSISTENT RUN-TO-RUN, WITH THE SYSTEM
STILL PROGGED TO RETROGRESS TOWARDS CLYDE RIVER DURING THE DAY,
SPREADING LIGHT SNOW THROUGH THE COMMUNITY. OF GREATER CONCERN IS THE
TIGHT BACK SIDE GRADIENT. NORTHWESTERLY WIND GUSTS IN EXCESS OF
80 KM/H ARE LIKELY IN THIS GRADIENT WHICH, CONCURRENT WITH THE
FALLING SNOW, WILL LEAD TO BLIZZARD CONDITIONS BEGINNING TUESDAY
AFTERNOON. WINDS WILL ABATE WEDNESDAY MORNING AS THE LOW DISSIPATES
OVER THE STRAIT BRINGING AN END TO THE BLIZZARD CONDITIONS TO THE
COMMUNITY.
NWT...CLEAR SKIES UNDER A RIDGE OF HIGH PRESSURE HAVE BROUGHT SOME
EXTREMELY COLD WIND CHILLS TO PARTS OF THE TERRITORY OVERNIGHT.
A WARNING IS IN EFFECT FOR FORT LIARD AND NORMAN WELLS. TEMPERATURES
MAY MODERATE AT FORT LIARD AS SOME CLOUD MOVES IN OVERNIGHT, BUT
EXTREMELY COLD WIND CHILLS ARE EXPECTED IN NORMAN WELLS, FORT GOOD
HOPE AND FORT MCPHERSON TONIGHT AND WEDNESDAY MORNING.
THE METEOROLOGICAL SERVICE OF CANADA IS INVESTIGATING THE
DISCONTINUATION OF THIS SIGNIFICANT WEATHER DISCUSSION. IF YOU USE
THIS BULLETIN AND HAVE ANY COMMENTS OR CONCERNS, PLEASE CONTACT US AT
FOCN45@EC.GC.CA WITH THE SUBJECT: "SIGNIFICANT WEATHER DISCUSSION
FEEDBACK". INCLUDE YOUR ORGANIZATION AND HOW YOU USE THIS PRODUCT.
END/STAMMERS/GRIFFITH
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