Ontario Storm Prediction Centre-Latest Forecast Discussion
FXCN01 CWTOIssued: Saturday, January 14, 2012.
1. TODAY..ONE LAKE EFFECT SNOW BAND STILL STRONG ENOUGH TO BE
CONSIDERED A SNOWSQUALL IS COMING IN OFF OF SRN LAKE HURON TO ABOUT
ST MARYS WHERE SNOW SQUALL WARNINGS FOR LOCAL 15 CM REMAIN IN
EFFECT. THIS BAND SHOULD SLOWLY BE FORCED SOUTH TOWARDS LONDON AND
WOODSTOCK AS THE THERMAL TROUGH SINKS SOUTHWARD. THE WRF AND GEM
BOTH SHOW THIS SOUTHWARD SINKING MOTION BEGINNING THIS MORNING.
HENCE THE REASON FOR KEEPING LONDON AND WOODSTOCK IN A SNOW SQUALL
WATCH. IN THE NORTHERLY FLOW OFF OF GEORGIAN BAY IN THE WAKE OF THE
THERMAL TROUGH, SHEARED WIND PROFILES AND A LOWERING SUBSIDENCE
INVERSION WILL KEEP THE LAKE EFFECT SNOW BANDS WEAK WITH LOCAL 5 CM
OF FLUFFY WHITE STUFF EXPECTED MAINLY FROM ABOUT COLLINGWOOD TO JUST
EAST OF OWEN SOUND. ELSEWHERE ACROSS SRN ONTARIO JUST SCATTERED
FLURRIES ARE EXPECTED, AND ACROSS THE REST OF THE PROVINCE A QUIET
DAY IS ON TAP COURTESY OF THE LARGE RIDGE OF ARCTIC HIGH PRESSURE
MOVING SLOWLY EAST OVER THE GREAT LAKES.
2. TONIGHT..LAKE EFFECT ACTIVITY IN SRN ONTARIO WILL BE SLOWLY SHUT OFF AS STRONG SUBSIDENCE WITH THE RIDGE COMBINED WITH LIGHT AND SHEARED WINDS CAUSE ANY REMAINING FLURRIES TO RETREAT BACK TO OVER THE LAKES THEMSELVES. SOME REGIONS MAY EXPERIENCE THEIR FIRST MINUS 20 C READINGS OF THE SEASON OVER SRN ONTARIO, WITH TEMPS IN ERN ONTARIO AND E OF GEORGIAN BAY PLUNGING INTO THE MINUS MID 20S. IN THE RETURN COLD SOUTHERLY FLOW OFF OF LAKE SUPERIOR, LOOK FOR MULTI BANDED FLURRIES TO FORM IN AREAS FROM ABOUT TERRACE BAY TO WAWA WITH LOCAL 2-4 CM EXPECTED BY MORNING. OTHERWISE A QUIET NIGHT IS EXPECTED.
3, SUNDAY..WARM ADVECTION SNOW AHEAD OF A MOISTURE STARVED BUT FAIRLY STRONG AND DYNAMIC ALBERTA CLIPPER WILL SPREAD INTO NWRN ONTARIO AS FAR SE AS THE THUNDER BAY AREA, GIVING A GENERAL 2-5 CM SNOWFALL TO THOSE REGIONS. COLD SOUTHERLY FLOW OFF OF LAKE SUPERIOR CONTINUES AND WITH LAKE EFFECT CLOUD TEMPERATURES NEAR MINUS 15 FOR A GOOD PART OF THE DAY, LOOK FOR DENDRITIC GROWTH TO HELP BOOST SNOW AMOUNTS IN THE TERRACE BAY TO WAWA AREAS TO 5-10 CM. SOME FLURRIES MAY COME IN OFF OF LAKE HURON TO THE MANITOULIN ISLAND AREA, BUT AMOUNTS AT THIS POINT SHOULD BE LIMITED TO 2-4 CM. A QUIET AND SEASONABLY COLD MID WINTER DAY IS EXPECTED UNDER THE RIDGE OVER SRN/ERN ONTARIO.
4. IN THE LONGER RANGE..CLIPPER LOW TRACKS ACROSS NWRN INTO FAR NRN ONTARIO MONDAY BRINGING A GENERAL 10 CM SNOWFALL WITH IT. WARM ADVECTION SNOWS SPREAD INTO NERN ONTARIO, WITH POSSIBLE WET SNOW VS RAIN ISSUES NEAR THE NORTH SHORE OF LAKE HURON AS TEMPERATURES SNEAK A COUPLE DEGREES ABOVE THE FREEZING MARK. SRN ONTARIO MAY START TO SEE A FEW WET FLURRIES OR SHOWERS AS THE PRECIPITATION SHIELD AHEAD OF A COLD FRONTAL TROUGH OUT OF THE CLIPPER LOW GETS CLOSER. STRONG WARM ADVECTION SHOULD HELP RETURN TEMPERATURES TO A COUPLE DEGREES ABOVE FREEZING SRN ONTARIO, WITH TEMPERATURES IN ERN ONTARIO RECOVERING TO NEAR OR JUST BELOW THE ZERO DEGREE MARK. AN INTERSTING SCENARIO THOUGH IS SETTING UP FOR TUESDAY AS GUIDANCE IS SUGGESTING A LOW WILL DEVELOP OVER OR NEAR COLORADO MONDAY THEN MOVE NEWD AND DEEPEN AS IT RACES ACROSS THE LOWER GREAT LAKES INTO QUEBEC. THERE STILL IS SOME QUESTION AS TO ITS EXACT TRACK, WHICH APPEARS TO BE NEWD RIGHT OVER SRN/ERN ONTARIO TUESDAY. DETERMINISTIC GLBL SEEMS TO BE THE DEEPEST AND FURTHEST N OF THE GUIDANCE, WITH MANY ENSEMBLE MEMBERS, THE ECMWF, LATEST SREF AND ESPECIALLY GFS SUGGESTING A TRACK THAT WILL KEEP THE LOW JUST SOUTH OF OTTAWA. FOR THESE REASONS HAVE SHAVED OFF A FEW DEGREES FROM TUESDAY'S MAXIMUM TEMPERATURES IN A SWATH OF REGIONS FROM GREY BRUCE ACROSS BARRIE AND HALIBURTON INTO ERN ONT INCLUDING OTTAWA WHICH WILL LIKELY NOT GET INTO THE WARM SECTOR. HAVE ALSO ACCORDINGLY ENSURED THAT FORECASTS INDICATED BOTH RAIN AND SNOW FOR THESE REGIONS, ALONG WITH RISK OF FREEZING RAIN FOR THE OTTAWA VALLEY GIVEN THE EXPECTED TRACK OF THE LOW. IF THE TRACK ADJUSTS ANY FURTHER SOUTHEAST MORE TOWARDS THE GFS SOLUTION, PHASE ISSUES AND CONSIDERABLY COLDER TEMPERATURES FOR MUCH OF SRN ONTARIO MAY BE A POSSIBILITY. WILL KEEP A CLOSE EYE ON THIS SYSTEM, WHICH MAY HAVE A BAND OF HEAVY ACCUMULATING SNOW IN THE COLD AIR TO THE NW OF ITS TRACK. COLD ARCTIC AIR AND MAYBE A BRIEF SHOT OF LAKE EFFECT SNOWS WILL RETURN TO SRN/ERN ONTARIO IN THE WAKE OF THIS SYSTEM BY MID WEEK.
5. HAVE A GREAT DAY, EH?
END/KUHN/OSPC
2. TONIGHT..LAKE EFFECT ACTIVITY IN SRN ONTARIO WILL BE SLOWLY SHUT OFF AS STRONG SUBSIDENCE WITH THE RIDGE COMBINED WITH LIGHT AND SHEARED WINDS CAUSE ANY REMAINING FLURRIES TO RETREAT BACK TO OVER THE LAKES THEMSELVES. SOME REGIONS MAY EXPERIENCE THEIR FIRST MINUS 20 C READINGS OF THE SEASON OVER SRN ONTARIO, WITH TEMPS IN ERN ONTARIO AND E OF GEORGIAN BAY PLUNGING INTO THE MINUS MID 20S. IN THE RETURN COLD SOUTHERLY FLOW OFF OF LAKE SUPERIOR, LOOK FOR MULTI BANDED FLURRIES TO FORM IN AREAS FROM ABOUT TERRACE BAY TO WAWA WITH LOCAL 2-4 CM EXPECTED BY MORNING. OTHERWISE A QUIET NIGHT IS EXPECTED.
3, SUNDAY..WARM ADVECTION SNOW AHEAD OF A MOISTURE STARVED BUT FAIRLY STRONG AND DYNAMIC ALBERTA CLIPPER WILL SPREAD INTO NWRN ONTARIO AS FAR SE AS THE THUNDER BAY AREA, GIVING A GENERAL 2-5 CM SNOWFALL TO THOSE REGIONS. COLD SOUTHERLY FLOW OFF OF LAKE SUPERIOR CONTINUES AND WITH LAKE EFFECT CLOUD TEMPERATURES NEAR MINUS 15 FOR A GOOD PART OF THE DAY, LOOK FOR DENDRITIC GROWTH TO HELP BOOST SNOW AMOUNTS IN THE TERRACE BAY TO WAWA AREAS TO 5-10 CM. SOME FLURRIES MAY COME IN OFF OF LAKE HURON TO THE MANITOULIN ISLAND AREA, BUT AMOUNTS AT THIS POINT SHOULD BE LIMITED TO 2-4 CM. A QUIET AND SEASONABLY COLD MID WINTER DAY IS EXPECTED UNDER THE RIDGE OVER SRN/ERN ONTARIO.
4. IN THE LONGER RANGE..CLIPPER LOW TRACKS ACROSS NWRN INTO FAR NRN ONTARIO MONDAY BRINGING A GENERAL 10 CM SNOWFALL WITH IT. WARM ADVECTION SNOWS SPREAD INTO NERN ONTARIO, WITH POSSIBLE WET SNOW VS RAIN ISSUES NEAR THE NORTH SHORE OF LAKE HURON AS TEMPERATURES SNEAK A COUPLE DEGREES ABOVE THE FREEZING MARK. SRN ONTARIO MAY START TO SEE A FEW WET FLURRIES OR SHOWERS AS THE PRECIPITATION SHIELD AHEAD OF A COLD FRONTAL TROUGH OUT OF THE CLIPPER LOW GETS CLOSER. STRONG WARM ADVECTION SHOULD HELP RETURN TEMPERATURES TO A COUPLE DEGREES ABOVE FREEZING SRN ONTARIO, WITH TEMPERATURES IN ERN ONTARIO RECOVERING TO NEAR OR JUST BELOW THE ZERO DEGREE MARK. AN INTERSTING SCENARIO THOUGH IS SETTING UP FOR TUESDAY AS GUIDANCE IS SUGGESTING A LOW WILL DEVELOP OVER OR NEAR COLORADO MONDAY THEN MOVE NEWD AND DEEPEN AS IT RACES ACROSS THE LOWER GREAT LAKES INTO QUEBEC. THERE STILL IS SOME QUESTION AS TO ITS EXACT TRACK, WHICH APPEARS TO BE NEWD RIGHT OVER SRN/ERN ONTARIO TUESDAY. DETERMINISTIC GLBL SEEMS TO BE THE DEEPEST AND FURTHEST N OF THE GUIDANCE, WITH MANY ENSEMBLE MEMBERS, THE ECMWF, LATEST SREF AND ESPECIALLY GFS SUGGESTING A TRACK THAT WILL KEEP THE LOW JUST SOUTH OF OTTAWA. FOR THESE REASONS HAVE SHAVED OFF A FEW DEGREES FROM TUESDAY'S MAXIMUM TEMPERATURES IN A SWATH OF REGIONS FROM GREY BRUCE ACROSS BARRIE AND HALIBURTON INTO ERN ONT INCLUDING OTTAWA WHICH WILL LIKELY NOT GET INTO THE WARM SECTOR. HAVE ALSO ACCORDINGLY ENSURED THAT FORECASTS INDICATED BOTH RAIN AND SNOW FOR THESE REGIONS, ALONG WITH RISK OF FREEZING RAIN FOR THE OTTAWA VALLEY GIVEN THE EXPECTED TRACK OF THE LOW. IF THE TRACK ADJUSTS ANY FURTHER SOUTHEAST MORE TOWARDS THE GFS SOLUTION, PHASE ISSUES AND CONSIDERABLY COLDER TEMPERATURES FOR MUCH OF SRN ONTARIO MAY BE A POSSIBILITY. WILL KEEP A CLOSE EYE ON THIS SYSTEM, WHICH MAY HAVE A BAND OF HEAVY ACCUMULATING SNOW IN THE COLD AIR TO THE NW OF ITS TRACK. COLD ARCTIC AIR AND MAYBE A BRIEF SHOT OF LAKE EFFECT SNOWS WILL RETURN TO SRN/ERN ONTARIO IN THE WAKE OF THIS SYSTEM BY MID WEEK.
5. HAVE A GREAT DAY, EH?
END/KUHN/OSPC
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