***A FLASH FLOOD WATCH*** REMAINS IN EFFECT FOR THE EASTERN TWO THIRDS OF UPSTATE NY & MOST OF PENNSYLVANIA THROUGH MOST OF TUESDAY: ***THE CONTINUED ASSAULT WITH TROPICALLY INDUCED/ DRENCHING DOWNPOURS*** WILL REMAIN THROUGH MOST OF THE REGION UNTIL MIDWEEK. THE SIMPLEST WAY TO EXPLAIN THE WAVES OF MODERATE TO HEAVY RAINS & EMBEDDED THUNDERSTORMS IS LIKE A "SQUEEZE PLAY" GOING ON, AS AN ELONGATED/ HIGHLY AMPLIFIED DEEP TROUGH ALONG THE WESTERN SIDE OF THE APPALACHIANS, WHILE A STRONG AREA OF HIGH PRESSURE OVER THE WESTERN ATLANTIC OCEAN IS RIDGING ITSELF WESTWARD TOWARDS THE EASTERN COASTLINE. AN UPPER/ LOWER JET STREAM IS STREAMING MOSTLY NORTHWARD FROM THE EASTERN GULF OF MEXICO & PULLING COPIOUS AMOUNTS OF TROPICAL MOISTURE WITH IT. THE MORE CENTRALIZED/ NARROW AXIS OF THE HEAVIEST RAINFALL TODAY OCCURRED ACROSS MAINLY THE EASTERN THIRD OF THE REGION, WHERE NUMEROUS **FLASH FLOOD WARNINGS** WERE ISSUED AS TRAINING HEAVY SHOWERS/ EMBEDDED T-STORMS LIFTED NORTH NORTHEAST BETWEEN THE TWO STRONG SYSTEMS. THE AXIS OF OCCASIONAL HEAVY SHOWERS & T-STORMS WILL SHIFT MORE TO THE WEST LATER TONIGHT & TUESDAY ON A MORE SOUTH TO NORTH AXIS FROM SOUTH/ CENTRAL, PA THROUGH NORTH/ CENTRAL, PA TO CENTRAL, NY FROM HARRISBURG/ HERSHEY THROUGH STATE COLLEGE/ WILLIAMSPORT TO ACROSS THE CORNING/ ELMIRA AREA OF NY TO CENTRAL LAKE ONTARIO. TIMES OF HEAVY DOWNPOURS ASSOCIATED WITH THESE WAVES OF LOW PRESSURE WILL BE AT ITS GREATEST THREAT DURING THE AFTERNOON HOURS, AS SOME LIMITED DAYTIME SURFACE HEATING WILL ENHANCE CONVECTION TO CREATE EXCESSIVE RUN-OFF FROM STRONGER SHOWERS & A FEW T-STORMS. GENERAL RAINFALL AMOUNTS DURING THE NEXT 24 HOURS IN THE AREAS I OUTLINED ABOVE IS EXPECTED FROM .75 TO 1.25 INCHES WITH SOME AREAS RECEIVING GREATER AMOUNTS...ESPECIALLY WHERE TRAINING HEAVY SHOWERS & STORMS SWEEP THROUGH...LIKELY CREATING "FLASH FLOODING" ALONG SMALLER CREEKS & STREAMS...ESPECIALLY IN LOW- LAND AREAS, BUT THE LARGER MAIN STEM RIVERS ARE GRADUALLY SWELLING, AS I DROVE AROUND PORTIONS OF THE REGION. THERE ARE A FEW RIVERS DURING THE PAST COUPLE DAYS ACROSS THE MOWHAWK VALLEY OF EASTERN/ NORTHEASTERN, NY WHICH HAVE SPILLED OVER THEIR BANKS, ALONG WITH URBAN STREET FLOODING...PARTICULARLY IN POOR DRAINAGE LOCATIONS & CULVERTS. NEEDLESS TO SAY...IT WILL REMAIN VERY MUGGY DURING THE OVERNIGHT HOURS WITH LOWS FROM THE MID TO UPPER 60`S, BUT DAYTIME HIGHS WILL SLOWLY INCREASE THE REST OF THE WEEK TO AROUND 80 TOMORROW...THE LOWER 80`S WED. AFTERNOON...TO THE MID 80`S THURSDAY AFTERNOON & FINALLY FRIDAY APPROACHING 90 DEGREES. *** ON WEDNESDAY...THE AMPLIFIED/ LONGWAVE TROUGH IS FORECAST TO BEGIN BREAKING DOWN AS THE STRONGER HIGH PRESSURE RIDGING RETROGRADES WELL INLAND & SHIFTS LESS FREQUENT SHOWERS & T-STORMS TO WESTERN, PA/ WESTERN, NY DURING THE AFTERNOON & EARLY EVENING HOURS. DUE TO SOME TROPICALLY INDUCED/ MOIST AIR MASS IN PLACE, ALONG WITH MORE SUN INCREASING MODERATE CONVECTIVE VALUES NEAR THE SURFACE FROM 500 TO NEAR 1000 J/ KG`S, DESTABILIZING THE ATMOSPHERE DURING THE AFTERNOON HOURS OF WEDNESDAY & THURSDAY....WILL RESULT IN STILL A GOOD CHANCE OF A HEAVY AFTERNOON T-STORM IN SOME AREAS OF THE REGION. **FROM** STEVE MATTISON...VOLUNTEER SKYWARN SPOTTER FOR THE NWS.
Posted on: Tue, 02 Jul 2013 03:09:01 +0000
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