615 FXUS61 KPHI 031940 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 340 PM EDT MON JUN 3 2013 .SYNOPSIS... LOW PRESSURE ON THE SLOW MOVING COLD FRONT FROM NEW JERSEY TO CHESAPEAKE BAY WILL MOVE OFFSHORE TONIGHT. CANADIAN HIGH PRESSURE WILL BUILD INTO THE NORTHEAST USA TUESDAY AND WEDNESDAY. LARGE HIGH PRESSURE IN CENTRAL ATLANTIC OCEAN THURSDAY AND FRIDAY COMBINED WITH SLOWLY EVOLVING EASTERN UNITED STATES LOW PRESSURE SHOULD DEVELOP HEAVY RAINS IN PARTS OF OUR AREA BY LATE IN THE WEEK. THE LOW PRESSURE SYSTEM NEXT WEEKEND SHOULD EXTEND FROM NEW ENGLAND TO THE CAROLINAS. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... A FRONTAL BOUNDARY IS LOCATED RIGHT ACROSS THE CENTRAL PORTION OF OUR AREA THIS AFTERNOON, BASICALLY JUST NORTHWEST OF THE I-95/DELAWARE VALLEY CORRIDOR. A WEAK WAVE OF LOW PRESSURE DEVELOPED ON THE BOUNDARY THIS AFTERNOON, WHICH IS HELPING SLOW THE MOVEMENT OF THE FRONT. HOWEVER, WE STILL EXPECT THE BOUNDARY TO SLOWLY SAG EASTWARD THIS EVENING. WE WILL STILL GET SCATTERED SHOWERS, AND A FEW THUNDERSTORMS ALONG AND AHEAD OF THE BOUNDARY. THE BEST CHANCE FOR MORE WIDESPREAD SHOWER/THUNDERSTORM ACTIVITY WILL BE AHEAD OF THE FRONT ACROSS EASTERN NEW JERSEY AND SOUTHERN DELAWARE. THIS IS WHERE THE GREATEST SHORT WAVE/VORTICITY INFLUENCE IS LOCATED AS WELL AS THE GREATEST INSTABILITY. SCATTERED SHOWERS WILL ALSO DEVELOP ALONG AND JUST BEHIND THE FRONTAL BOUNDARY AS ANOTHER WEAK SHORT WAVE/VORT MAX APPROACHES FROM THE WEST. SO FAR, THESE SHOWERS HAVE GONE UP QUICKLY, BUT HAVE NOT BUILT VERY TALL; WE EXPECT THIS TREND TO CONTINUE, ALTHOUGH A BRIEF MODERATE TO HEAVY DOWNPOUR CAN OCCUR. FARTHER EAST, THERE IS A NICE LOW LEVEL THETA-E RIDGE AND CO-LOCATED OMEGAS EXTENDING ALONG THE DELAWARE AND NEW JERSEY COASTLINE. HEAVY RAINFALL WILL CONTINUE TO BE A POSSIBILITY IN SHOWERS/THUNDERSTORMS HERE UNTIL THIS AREA MOVES OFFSHORE LATER THIS EVENING. AFTER THE FRONT PUSHES OFFSHORE LATER THIS EVENING, PW VALUES DROP AND WITH NO ADDITIONAL SHORT WAVE/VORT MAX, SHOWERS SHOULD DIMINISH. AREAS ALONG THE COAST WILL HOLD ON TO THE PRECIPITATION CHANCES THE LONGEST, BUT EVERYONE SHOULD BE RAIN FREE BY MIDNIGHT OR SHORTLY AFTER. A BLEND OF MAV/MET MOS WAS TAKEN FOR OVERNIGHT LOWS. THE MAV CLEARS EVERYONE OUT SOONER THAN THE MET, WHICH COOLS EVERYONE FASTER. LOOKING UPSTREAM, THERE IS SOME DECENT CLEARING WHICH SHOULD MOVE IN DURING THE NIGHT, SO WE USED A MAJORITY OF THE MAV. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/... ON TUESDAY, HIGH PRESSURE TRIES TO BEGIN NOSING ITS WAY DOWN ACROSS THE AREA FROM THE NORTHWEST. MOSTLY CLEAR SKIES ARE EXPECTED, ALTHOUGH A FEW CLOUDS COULD DEVELOP DURING THE AFTERNOON. TEMPERATURES ARE EXPECTED TO BE FAIRLY CLOSE TO NORMAL, AND MOS NUMBERS WERE CLOSE, SO A BLEND OF MAV/MET WAS TAKEN. && .LONG TERM /TUESDAY NIGHT THROUGH MONDAY/... 500MB: FLAT WEST-EAST RIDGING DEVELOPING ALONG THE EAST COAST TO START THE MID WEEK PERIOD WILL EVOLVE TO LARGE SCALE POSITIVE TILT TROUGH FROM THE GREAT LAKES TO THE SOUTHERN PLAINS WITH NUMEROUS EMBEDDED SHORT WAVES CONFUSING THE FLOW. FOR US ALONG THE EAST COAST...A DEEP SOUTHWESTERLY FLOW OF HUMID AIR DEVELOPS BY THE END OF THE WEEK WITH THE POTENTIAL FOR A LARGER AREA OF COVERAGE 1.5 INCH RAINFALL COMPARED TO WHAT OCCURRED YESTERDAY AND TODAY. TEMPERATURES: CALENDAR DAY AVERAGES NEARLY 5 DEGREES BELOW NORMAL WEDNESDAY BECOMING NEAR NORMAL THURSDAY THEN ABOVE NORMAL THURSDAY THROUGH THE WEEKEND WITH POTENTIAL FOR AT LEAST 5 DEGREE WARMER THAN NORMAL DAYS FOR BOTH FRIDAY AND SATURDAY. THE DAILIES BELOW... THE ECMWF WAS NOT AVAILABLE IN AWIPS 1 FOR THIS 12Z FCST CYCLE THO IT WAS APPARENTLY AVAILABLE IN AWIPSII TUE NIGHT THROUGH WED NIGHT ELEMENTS ARE 12Z/4 50 50 BLENDED NCEP GFS/NAM MOS GUIDANCE. THU IS MAINLY 12Z/3 GFS MEX GUIDANCE THU NIGHT-MONDAY...1442Z HPC GUIDANCE IS BLENDED AT TIMES WITH THE 12Z/3 GFS MEX MOS GUIDANCE. TUESDAY NIGHT...MOSTLY CLEAR AND COMFORTABLY COOL! NW WIND WITH G UNDER 15 KTS IN THE EVENING DIMINISHING DURING THE NIGHT AS THE WIND TURNS LIGHT NORTH. WEDNESDAY...PARTLY SUNNY. LIGHT WIND BECOME SEA BREEZES DURING THE AFTERNOON KACY/KMIV AND KILG. WEDNESDAY NIGHT...THICKENING CLOUDS LATE. THURSDAY...MOSTLY CLOUDY WITH SHOWERS POSSIBLE OVER EASTERN PA? FRIDAY...SHOWERS...FOG AT NIGHT? PWAT NEAR 1.8 INCHES AND DIFFLUENT THICKNESS WITH A FRONTAL BOUNDARY OVER THE AREA AND WEAK LOW PRES. A RECIPE FOR HEAVY RAINFALL. SATURDAY...LEFTOVER SHOWERS OR A TSTM MAINLY COAST? PATCHY FOG EARLY MORNING AND LATE AT NIGHT. SUNDAY AND MONDAY MAINLY HPC GUIDANCE...BETWEEN SYSTEMS AS RIDGING FOLLOWS THE DEPARTURE OF THE FRIDAY LOW PRESSURE SYSTEM AND THE NEXT ONE COMING FROM THE WEST LATE MONDAY OR TUESDAY. && .AVIATION /20Z MONDAY THROUGH SATURDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. A SLOW MOVING FRONTAL BOUNDARY WILL CONTINUE TO SLIDE EASTWARD ACROSS THE AREA THIS EVENING. SCATTERED SHOWERS WILL CONTINUE TO DEVELOP ALONG AND AHEAD OF THE BOUNDARY THROUGH THIS EVENING. MOSTLY VFR CONDITIONS WILL PREVAIL OUTSIDE OF ANY SHOWER ACTIVITY ALONG AND BEHIND THE FRONT. IF ANY SHOWERS DO IMPACT A TAF SITE LATE THIS AFTERNOON INTO THIS EVENING, A BRIEF PERIOD OF MODERATE TO HEAVY RAIN COULD OCCUR AND TEMPORARILY REDUCE VSBYS AND/OR CIGS. FOR NOW WE WILL HANDLE THIS OCCURRENCE WITH A TEMPO GROUP WHEN THEY BECOME MORE IMMANENT. AHEAD OF THE FRONT, FOR MIV/ACY, MVFR/IFR CONDITIONS WILL PERSIST UNTIL THE FRONT MOVES INTO THESE AREAS. ALL SHOWER ACTIVITY SHOULD DIMINISH AROUND OR SHORTLY AFTER MIDNIGHT. ONCE THE FRONT MOVES OFFSHORE, VFR CONDITIONS WILL MOVE IN EVERYWHERE AND PERSIST THROUGH TUESDAY. WINDS WILL BE FAIRLY TRICKY UNTIL THE FRONT MOVES THROUGH THE AREA. AHEAD OF THE FRONT, SOUTHERLY WINDS WILL PERSIST, WHILE NORTH-NORTHWEST WINDS WILL MOVE IN BEHIND THE FRONT. HOWEVER, RIGHT ALONG THE BOUNDARY, WINDS WILL BE VARIABLE, THEN TURN MORE NORTHWEST AS THE FRONT MOVES THROUGH. NORTH-NORTHWEST WINDS ARE EXPECTED ON TUESDAY, AND MAY GUST NEAR 15 KNOTS, ESPECIALLY EARLY IN THE DAY. OUTLOOK... TUESDAY NIGHT...VFR CLEAR. NW WIND G UNDER 15 KT BECOMING LIGHT N DURING THE NIGHT. CONFIDENCE WELL ABOVE AVERAGE. WEDNESDAY...VFR SCT-BKN CLOUDS AOA 5000 FT. LIGHT WIND BECOMING SE TO S SEA BREEZES DURING THE AFTN AT KACY KMIV AND KILG. CONFIDENCE WELL ABOVE AVERAGE. THURSDAY...MOSTLY VFR CONDITIONS. CHANCE OF SHOWERS MOSTLY IN E PA. CONFIDENCE IS AVERAGE. THURSDAY NIGHT INTO FRIDAY...MVFR TO IFR CONDITIONS DEVELOPING AS SHOWERS AND SCATTERED THUNDERSTORMS DEVELOP IN THE INSTABILITY BURST. CONFIDENCE IS ABOVE AVERAGE. SATURDAY...POSSIBLE IFR OR MVFR CONDS IN FOG/STRATUS EARLY AND MAYBE A CHANCE OF A SHOWER OR TSTM IN THE AFTN WITH VFR CIGS? && .MARINE... A FRONTAL BOUNDARY WILL SLOWLY PUSH THROUGH THE COASTAL WATERS TONIGHT. SOUTH-SOUTHWEST WINDS AHEAD OF THE FRONT WILL BECOME MORE NORTHWEST BEHIND THE FRONT. WE EXPECT WINDS AND WAVES TO REMAIN BELOW ADVISORY LEVELS TONIGHT INTO TUESDAY. HOWEVER, WINDS COULD APPROACH 20-25 KNOTS FOR A BRIEF PERIOD OVERNIGHT TOWARD DAYBREAK TUESDAY BEHIND THE COLD FRONT. OUTLOOK... TUESDAY NIGHT THROUGH WED NIGHT...NO HEADLINES. THU INTO FRIDAY...POSSIBLE SLY FLOW FETCH GENERATED SCA CONDS OR HAZARDOUS SEAS FOR THE ATLC WATERS. CONFIDENCE FOR AN SCA HEADLINE IS AVERAGE. SATURDAY...WINDS AND SEAS SHOULD DIMINISH. && .RIP CURRENTS... THE RIP CURRENT RISK FOR THE NEW JERSEY BEACHES TODAY IS FORECAST TO BE MODERATE. THIS WEEK IS RIP CURRENT AWARENESS WEEK. EACH DAY THIS WEEK, WE WILL ISSUE A PUBLIC INFORMATION STATEMENT DETAILING VARIOUS CONCERNS FOR THOSE HEADED TO THE OCEAN WATERS THIS SEASON. && .CLIMATE... OUR ENSO SEASON HEADING INTO THIS SUMMER STAYED UNDER THE CPC DEFINITION OF A FULL FLEDGED LA NINA. SO OUR SUMMER ANALOGS WILL HAVE A DIFFERENT SET OF PREVIOUS SUMMERS THAN THE LAST TWO. IN SPITE OF SOME CHILLY DAYS IN THERE, (MAYBE SURPRISINGLY) BOTH APRIL AND MAY WERE UNSEASONABLY WARM AGAIN FOR THE FIFTH CONSECUTIVE SPRING. BY LOCAL DEFINITION, THOSE MONTH'S AVERAGE TEMPERATURES HAVE TO FALL IN THE TOP THIRD OF ALL MONTHS DATING BACK TO 1872. MAY CAME DOWN TO THE WIRE. WHILE NEITHER MONTH WAS AS WARM AS SPRING 2012, THEY STILL CRACKED THE TOP THIRD. SINCE 1872, THIS COMBINATION HAS OCCURRED ONLY TWENTY-TWO TIMES, BUT NOW TEN TIMES SINCE 1990. IT SHOULD BE NOTED (AS SOLAR CYCLISTS MIGHT ALREADY), THE SUMMERS OF 1980, 1991 AND 2002 WERE ALL HOT SUMMERS IN PHILADELPHIA. THE CURRENT SOLAR CYCLE IS NOT ON PAR WITH THOSE. NEVERTHELESS, THIS ELEVEN YEAR CYCLE HAS SHOWN ITSELF IN THE ANALOGS. BECAUSE WE HAVE NOTICED THAT SUMMERS PRIOR TO CPC'S ANALYSIS OF ENSO CONDITIONS HAVE DRAGGED DOWN THE SKILL OF THESE SUMMER ANALOGS, WE WILL STOP USING ANALOGS PRIOR TO THE SUMMER OF 1950. THIS ALSO LEAVES A HOMOGENEOUS ENSO CLASSIFICATION (VS USING JMA CLASSIFICATION PRIOR TO 1950). FOR HOTTER OR WORSE, HERE ARE THE FIVE ANALOGS. THESE ARE TEMPERATURES AND PRECIPITATION FOR PHILADELPHIA FOR THE UPCOMING SUMMER FOLLOWING UNSEASONABLY WARM APRILS AND MAYS WITH ENSO NEUTRAL CONDITIONS IN THE TROPICAL PACIFIC. THE ONE DIFFERENCE WITH THIS ANALOG SET VS THE LAST COUPLE OF SUMMERS IS THE BACK END HEAT FOR AUGUST. WHILE THE LAST SEVERAL SUMMERS HAVE BEEN DOWNRIGHT HOT, AUGUST HAS BEEN THE MONTH CLOSEST TO AVERAGE LEVELS. YEAR JUNE AVG JULY AVG AUGUST AVG SUMMER AVG SUMMER PCPN 1959 72.2 75.9 76.5 74.9 16.49 1980 70.6 78.5 80.0 76.4 9.11 1991 75.7 79.0 79.0 77.9 12.01 1993 74.4 81.4 78.9 78.2 8.68 2004 71.8 76.3 75.0 74.4 16.65 AVG 72.9 78.2 77.9 76.4 12.59 1981-2010 NML 73.3 78.1 76.6 76.0 11.28 THE EXPERIMENTAL TWO CLASS SEASONAL OUTLOOK BY THE CPC FOR THIS SUMMER HAS THE MOUNT HOLLY CWA WITH ABOUT A 60 PERCENT CHANCE OF WARMER THAN NORMAL WEATHER. THE PRECIPITATION OUTLOOK IS FOR EQUAL CHANCES OF IT BEING EITHER DRIER OR WETTER THAN NORMAL. ANOTHER LOCAL PROGRAM PRODUCED BY THE RECENTLY RETIRED MARK DELISI IS COMPLETELY DEPENDENT ON THE TIMING OF THE FIRST HEAT WAVE OF THE SEASON AT PHILADELPHIA. THIS PROGRAM INDICATES THE LIKELIHOOD OF AN ABOVE NORMAL JJA TEMPERATURE REGIME WITH THE FIRST DAY OF THE RECENT HEAT WAVE OCCURRING MAY 29...IDENTICAL TO THE FIRST DAY OF THE 2012 INITIAL HEAT WAVE HERE AT KPHL. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...DRAG 339 NEAR TERM...ROBERTSON SHORT TERM...ROBERTSON LONG TERM...DRAG 339 AVIATION...DRAG/ROBERTSON 339 MARINE...DRAG/ROBERTSON 339 RIP CURRENTS... CLIMATE...