Weather Synopsis July 4th, 2007
A Weather Synopsis brought to you by the OSPC in Toronto.
MF
1. TONIGHT..WE MAINTAIN A SLIGHT RISK OF SEVERE TSTMS THIS EVENING NWRN
ONTARIO. ONCE THE CURRENT CIRRUS SHIELD FROM PRIOR CONVECTION TO THE
SW OF THE AREA MOVES OUT THIS AFTERNOON STRONG SUNSHINE WILL
DESTABILIZE THE ATMOSPHERE WITH SURFACE BASED CAPES INCREASING TO
2000-2500 J/KG BY LATE AFTERNOON. STRONG LEFT EXIT REGION OF UPPER
JET AREA BECOMES INVOLVED BY EVENING AS WELL AND AS THE CURRENT CAP
NEAR 850 MB WEAKENS AND EVENTUALLY VANISHES LOOK FOR CONVECTION
EXPECTED TO EXPLODE OVER SERN MANITOBA INTO NWRN MINNESOTA TO MOVE
INTO NWRN ONTARIO BY EVENING. FAIRLY DECENT SHEARS BELOW 6 KM OF 30
TO 35 KNOTS WILL BE SUPPORTIVE OF SUPERCELLS INITIALLY WHICH MAY TRY
TO EVOLVE INTO A FEW BOW ECHO TYPE LINE SEGMENTS THIS EVENING SHOULD
THE TSTM AREA GET ORGANIZED AND RACE ESEWD WITH A WEAK COLD FRONT
ACROSS NWRN ONTARIO. MAIN THREATS ARE 2 TO 5 CM HAIL (IE. UP TO
ABOUT GOLF BALL SIZE) AND WIND GUSTS TO 100 KM/H. ELSWHERE A FEW
NON-SEVERE TSTMS IN THE WARM AIR ADVECTION AREA OVER NERN ONTARIO
AND A FEW EMBEDDED LOWER TOPPED TSTMS OVER FAR NRN ONTARIO WHICH MAY
GIVE SOME SMALL HAIL ARE ON TAP FOR THE CONVECTIVE SCENARIO THIS
AFTERNOON INTO EVENING. SRN/ERN ONTARIO ARE QUIET AND WITH LOW LEVEL
DRY AIR AND SUBSIDENCE IN PLACE WE HAVE BEEN WATCHING CLOUDS AND
PRECIPITATION ECHOES DISSOLVE AS THEY TRY TO COME IN FROM MICHIGAN.
2. FOR WEDNESDAY..THE COLD FRONT AND POLAR WAVE WILL SLIDE SEWD
ACROSS SWRN ONTARIO INTO PENNSYLVANIA/WRN NY STATE BY EVENING.
SLIGHT RISK OF SEVERE TSTMS WITH DAMAGING WINDS AND TORRENTIAL
DOWNPOURS OVER SWRN ONTARIO IN THE WARM AIR DURING THE AFTERNOON
INTO EVENING. HOWEVER A COUPLE FORECAST PROBLEMS LIKE POOR HIGH
LEVEL SUPPORT (RIGHT EXIT OF UPPER JET OVER NRN MICHIGAN).. AMOUNT
OF CLOUD COVER.. AND POSSIBLE ORGANIZED SEVERE TSTMS ACTING
AS A MOISTURE DAM RUMBLING SEWD ACROSS THE US MIDWEST SOUTH OF THE
LOWER GREAT LAKES COULD ACT AS AN INHIBITION AND KEEP ANY TSTMS THAT
MAY FORM NON-SEVERE AND QUITE ISOLATED. FURTHER NE INTO ERN ONTARIO
AND COTTAGE COUNTRY..FURTHER NE LOTS OF CLOUD COVER WILL LIMIT
INSOLATION AND THEREFORE REDUCE INSTABILITY RESULTING IN A FEW
ELEVATED EMBEDDED NON-SEVERE TSTMS WITH BRIEF DOWNPOURS. OVER NRN
ONTARIO COLD UPPER TROUGH WEATHER IS EXPECTED WITH A SEA OF EMBEDDED
TALL CUMULUS AND SCATTERED AFTERNOON AND EVENING NON-SEVERE
THUNDERSTORMS WITH SMALL HAIL AND GUSTY WINDS. TYPICAL FORECAST
SURFACE BASED CAPES OF 500-1000 J/KG ARE EXPECTED..ALTHOUGH BOTH THE
GEM AND NAM SUGGEST LOCAL CAPES OF 1000-1500 J/KG OVER PARTS OF NWRN
ONTARIO INTO FAR NRN ONTARIO FROM BIG TROUT LAKE TOWARDS SRN JAMES
BAY. IF THIS HAPPENS 1-2 CM HAIL ISN'T OUT OF THE QUESTION FOR SOME
OF THE STRONGER THUNDERSTORMS.
3. THURSDAY..WITH UPPER TROUGH OVER THE ERN HALF OF THE PROVINCE
LOOK AGAIN FOR TALL CUMULUS AND CHANCE OF AFTERNOON INTO EVENING
THUNDERSTORMS. LATEST NAM FORECAST SOUNDINGS VIA BUFKIT SUGGEST A
FEW HUNDRED J/KG CAPES AND WITH LOWER FREEZING LEVELS DUE TO COLD
TEMPERATURE ALOFT SMALL HAIL MAY BE AN ISSUE AGAIN. IT APPEARS THAT
EXTREME SWRN ONTARIO AND NWRN ONTARIO WILL BE MORE UNDER THE
INFLUENCE OF A RIDGE COMING IN FROM THE WEST AND THEREFORE LIKELY
FREE OF CONVECTION.
4. IN THE LONGER RANGE..RIDGE MOVES ACROSS ERN PARTS OF THE PROVINCE
FRIDAY INTO SATURDAY GIVING A BREAK FROM THE UNSETTLED WEATHER WHILE
NEXT WARM FRONT BRINGS SHOWERS AND THUNDERSTORMS INTO NWRN ONTARIO.
WITH HOT (32 TO 35 C) AND HUMID AIR TRYING TO RETURN TO THE GREAT
LAKES BY SUNDAY COMBINED WITH A STRONGER FRONTAL ZONE AND STRONG
ZONAL FLOW ALOFT WILL MONITOR CLOSELY FOR A POSSIBLE INTERESTING
SEVERE THUNDERSTORM SCENARIO TO ROUND OUT THE WEEKEND. STAY TUNED.
5. HAVE A GOOD DAY..EH?
Source:Rob Kuhn, Ontario Storm Prediction Centre, Environment Canada
For watches/warnings please visit Environment Canada's Public Weather Warning website or listen to Environment Canada's Weatheradio on your local frequency
Sources:
NOAA National Weather Service
Environment Canada
The Weather Network
