PASPC Thunderstorm Outlook Day 1

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FOCN45 CWWG 171300

SIGNIFICANT WEATHER DISCUSSION ISSUED BY THE PRAIRIE AND ARCTIC STORM PREDICTION CENTRE OF ENVIRONMENT CANADA AT 7:00 AM CST WEDNESDAY JANUARY 17 2018.

ALERTS IN EFFECT... FREEZING RAIN WARNINGS FOR EAST-CENTRAL ALBERTA AND MAY BE REQUIRED FOR PORTIONS OF THE NORTHERN GRAINBELT.

SYNOPTIC OVERVIEW... ALOFT THERE IS AN UPPER TROUGH OVER THE EASTERN PACIFIC, AND AN UPPER RIDGE FROM THE NORTH CENTRAL STATES NORTHEASTWARD ACROSS SASKATCHEWAN AND NORTHWEST TERRITORIES INTO THE BEAUFORT. SHORT WAVE TROUGH BETWEEN THE UPPER RIDGE AND UPPER TROUGH EXTENDING FROM NORTHERN BC TO SOUTHWESTERN SASKATCHEWAN. THERE IS AN UPPER TROUGH FROM THE ARCTIC ISLANDS THROUGH FOXE BASIN SOUTHWARD ACROSS EASTERN HUDSON BAY TO SOUTHERN ONTARIO THEN SOUTHWESTWARD TO MISSISSIPPI.

AT THE SURFACE, A TROUGH SITS FROM THE MACKENZIE DELTA INTO NORTHERN ALBERTA. 999 MB LOW OVER NORTHERN JAMES BAY WITH WAVE NORTH OF SAULT ST MARIE. WARM FRONT SOUTHWARD FROM WAVE AND COLD FRONT EXTENDING NORTHWESTWARD FROM WAVE THROUGH NORTHERN MANITOBA. UPPER SHORT WAVE EXPECTED TO DEVELOP A LOW OVER THE NORTHERN GRAINBELT WHICH IS FORECAST TO TRACK SOUTHEASTWARD ACROSS SOUTHERN MANITOBA TONIGHT. BROAD RIDGE OF HIGH PRESSURE EXTENDING SOUTHWARD FROM THE ARCTIC OCEAN TO KIVALLIQ.

DISCUSSION...

PRAIRIES... ABOVE SEASONAL TEMPERATURES EXPECTED ACROSS THE REGION AS MILDER PACIFIC FLOW BECOMES ESTABLISHED. EARLY THIS MORNING THE WESTERLY PACIFIC FLOW HAD ALREADY SPREAD ACROSS ALBERTA INTO SOUTHWESTERN SASKATCHEWAN WHERE OVERNIGHT TEMPERATURES JUMPED TO THE PLUS SIDE OF ZERO.

RISK OF FREEZING RAIN OVER THE NORTHERN GRAINBELT AND SOUTHERN MANITOBA AS THE DEVELOPING LOW TRACKS SOUTHEASTWARD ACROSS THE REGION. FREEZING RAIN HAS BEEN REPORTED OVER ALBERTA AHEAD OF THE UPPER LEVEL SHORT WAVE. SOME UNCERTAINTY REMAINS AS TO WHETHER THE FREEZING PRECIPITATION WILL REMAIN ORGANIZED AS IT PUSHES ACROSS SASKATCHEWAN. FREEZING RAIN WARNING MAY BE EXPANDED.

A NEW LOW IS FORECAST TO DEVELOP NEAR FORT NELSON, BC EARLY THURSDAY MORNING. AS IT TRACKS EAST THROUGH THE DAY HEAVY POCKETS OF MIXED TYPE PRECIPITATION ARE EXPECTED TO AFFECT MUCH OF ALBERTA AND NORTHERN SK. THE SYSTEM WILL BE RELATIVELY UNSTABLE SO QPF WILL BE TRICKY TO PIN DOWN. PARTS OF THE ICEFIELDS PARKWAY MAY SEE TOTAL SNOWFALL AMOUNTS NEAR 15 CM. GUSTY WINDS ARE ALSO POSSIBLE ALONG THE MOUNTAIN PARKS.

WESTERN ARCTIC... THE TROUGH ACROSS THE NWT IS EXPECTED TO PRODUCE SOME RELATIVELY HEAVY SNOW THROUGH THURSDAY. CURRENT GUIDANCE SUGGESTS SUB-WARNING ACCUMULATIONS BUT TOTAL AMOUNTS OF 10 TO 20 CM ARE POSSIBLE FROM THE RICHARDSON MOUNTAINS TOWARDS NORMAN WELLS.

EASTERN ARCTIC... OUTFLOW FROM THE ARCTIC RIDGE OF HIGH PRESSURE GIVING NEAR WARNING VALUES FOR EXTREME COLD FOR THE HALL BEACH OVERNIGHT. AREA THIS TEMPERATURES AND WINDS HAVE STABILIZED AND WIND CHILL CRITERIA OF -55 IS NOT EXPECTED.

END/RUSSO/ROMBOUGH