Below is the US National Weather Services detailed overview of tomorrows weather, with a few comments by me in brackets and lower case to add clarity. To summarize, for areas of Ontario under the coloured severe weather threat areas, there is a risk of severe thunderstorms, strong winds up to 120kmh, heavy rain, hail, and the potential for Tornadoes. The current guidance puts Windsor under the greatest threat for severe weather, with Chatham, London, KW, Sarnia, Goderich, through Owen Sound to Blue Mountains expected tpo see a wild night, though it must be stated that *all* areas are at risk for seeing severe weather. This will be a dangerous storm for Southern Ontario. DAY 2 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1236 AM CDT TUE SEP 09 2014 VALID 101200Z - 111200Z ...THERE IS A SLGT RISK OF SVR TSTMS WEDNESDAY ACROSS SOUTHERN PORTIONS OF THE GREAT LAKES REGION INTO THE MIDDLE MISSISSIPPI AND LOWER OHIO VALLEYS... ...SUMMARY... SEVERE STORMS ARE POSSIBLE WEDNESDAY ACROSS SOUTHERN PORTIONS OF THE GREAT LAKES REGION INTO PARTS OF THE MIDDLE MISSISSIPPI AND LOWER OHIO VALLEYS. THIS WILL BE ACCOMPANIED BY THE RISK FOR DAMAGING WIND GUSTS...POSSIBLY A COUPLE OF TORNADOES...AND COULD IMPACT THE CHICAGO...DETROIT...INDIANAPOLIS AND CLEVELAND METROPOLITAN AREAS BY WEDNESDAY EVENING. ...SYNOPSIS... A BELT OF STRONG CYCLONIC FLOW WITHIN THE POLAR WESTERLIES APPEARS LIKELY TO DIG ACROSS THE NORTHERN ROCKIES INTO THE NORTHERN PLAINS DURING THIS PERIOD...AROUND THE SOUTHERN PERIPHERY OF AN ELONGATED LOW/POSITIVELY TILTED TROUGHING PROGRESSING ACROSS THE INTERNATIONAL BORDER AREA. MODELS STILL INDICATE THAT THIS WILL BE PRECEDED BY THE CONTINUED EAST NORTHEASTWARD PROPAGATION OF A HIGH-LEVEL JET WHICH HAS EMERGED FROM THE PACIFIC...ACROSS THE UPPER MIDWEST AND GREAT LAKES REGION. CYCLOGENESIS SUPPORTED BY THIS LATTER FEATURE ALONG A SOUTHWARD ADVANCING COLD FRONT APPEARS LIKELY TO PROCEED...WITH A CONTINUED SLOW DEEPENING OF THE LOW FORECAST AS IT MIGRATES NORTHEASTWARD OUT OF IOWA EARLY WEDNESDAY...ACROSS NORTHERN LOWER MICHIGAN...INTO WESTERN QUEBEC AROUND OR SHORTLY AFTER 12Z THURSDAY (8:00 PM Wednesday). WHILE THE MOISTENING WARM SECTOR OF THE LOW SURGES ACROSS THE LOWER GREAT LAKES REGION AND OHIO VALLEY DURING THE DAY...THE SOUTHEASTWARD ADVANCING COLD FRONT IN ITS WAKE IS EXPECTED TO REACH THE LOWER GREAT LAKES (Ontario)...LOWER OHIO VALLEY...OZARK PLATEAU AND SOUTHERN PLAINSBY THE END OF THE PERIOD. LARGE-SCALE FORCING FOR UPWARD VERTICAL MOTION ASSOCIATED WITH THE CYCLONE (strong low pressure system)...AND ALONG THE TRAILING COLD FRONT...ARE EXPECTED TO PROVIDE THE FOCUS FOR THUNDERSTORM ACTIVITY WEDNESDAY AND WEDNESDAY NIGHT. SOME OF THESE STORMS ARE EXPECTED TO BE SEVERE...WITH SWATHS OF POTENTIALLY DAMAGING WIND GUSTS POSSIBLE ACROSS SOUTHERN PORTIONS OF THE GREAT LAKES REGION. ...GREAT LAKES REGION INTO MIDDLE MS AND LOWER OH VALLEYS (& SW Ontario)...IT STILL SEEMS THAT AN EXTENSIVE AREA OF GENERALLY WEAKENING CONVECTION WILL SPREAD WITH THE STRONGER LARGE-SCALE ASCENT...NORTHEAST AND EAST OF THE SURFACE CYCLONE...INTO A PROGRESSIVELY MORE STABLE ENVIRONMENT ACROSS MUCH OF LOWER MICHIGAN AND ADJACENT AREAS OF THE GREAT LAKES TO THE NORTH EARLY IN THE DAY. IT REMAINS UNCLEAR WHETHER CONVECTION ON THE SOUTHERN FLANK OF THIS ACTIVITY WILL REMAIN STRONG...AND GRADUALLY RE-INTENSIFY AS DESTABILIZING NEAR-SURFACE INFLOW STRENGTHENS BY MIDDAY...OR NEW DEVELOPMENT OCCURS IN RESPONSE TO LOW-LEVEL WARM ADVECTION ALONG A TRAILING OUTFLOW BOUNDARY/DIFFERENTIAL HEATING ZONE ACROSS NORTHERNILLINOIS/INDIANA. REGARDLESS...GUIDANCE CONTINUES TO INDICATE RAPID LOW-LEVEL MOISTURE RETURN WILL OCCUR AHEAD OF THE CONVECTIVE BOUNDARY AND COLD FRONT...WITH PRECIPITABLE WATER INCREASING TO 2+ INCHES...AND SURFACE DEW POINTS INCREASING TO NEAR 70F AS FAR NORTH AS SOUTHERN LOWER MICHIGAN BY AFTERNOON. ALTHOUGH THE CORE OF THE STRONGER LOWER/MID TROPOSPHERIC WIND FIELDS...ON THE ORDER OF 50-70 KT...MAY SHIFT TO THE EAST OF THE CYCLONE...AND TO THE NORTH OF THE MORE SUBSTANTIVE BOUNDARY LAYER DESTABILIZATION...40 TO 50 KT WESTERLY MEAN FLOW APPEARS LIKELY TO PERSIST ACROSS MUCH OF THE SOUTHERN GREAT LAKES REGION THROUGH THE DAY. GIVEN THESE SPEEDS...AND THE POTENTIAL FOR HEAVY PRECIPITATION LOADING WITHIN THE EVOLVING EASTWARD PROPAGATING CONVECTIVE SYSTEM...SWATHS OF SEVERE SURFACE WIND GUSTS MAY ACCOMPANY ACTIVITY. IT DOES NOT SEEM OUT OF THE QUESTION THAT PEAK GUSTS COULD AT LEAST APPROACH SIGNIFICANT SEVERE CRITERIA /65 KT/ (120 kph). A COUPLE OF TORNADOES ALSO APPEAR POSSIBLE...PARTICULARLY NEAR THE INITIAL CONVECTIVE BOUNDARY WHICH COULD TEMPORARILY STALL ROUGHLY NEAR THE SOUTHERN MICHIGAN/INDIANA AND OHIO BORDER AREA. UNCERTAINTIES...HOWEVER...STILL APPEAR TOO LARGE FOR AN INTRODUCTION OF 10 PERCENT SIG SEVERE PROBABILITIES...AND AN ASSOCIATED HIGHER CATEGORICAL SEVERE OUTLOOK...AT THE PRESENT TIME. WEAKENING PRE-COLD FRONTAL WIND FIELDS/SHEAR...AND MID/UPPER FORCING FOR ASCENT...WITH SOUTHWARD EXTENT ACROSS THE MIDDLE MISSISSIPPI/LOWER OHIO VALLEYS INTO THE SOUTHERN PLAINS IS EXPECTED TO RESULT IN SIMILAR TRENDS CONCERNING SEVERE WEATHER POTENTIAL WEDNESDAY INTO WEDNESDAY EVENING. ..KERR.. 09/09/2014
Posted on: Tue, 09 Sep 2014 10:43:48 +0000
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