Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 300814 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 414 AM EDT WED JUL 30 2014 .SYNOPSIS... A BUILDING AREA OF HIGH PRESSURE OVER THE WESTERN ATLANTIC WILL PUSH A WARM FRONT TOWARDS THE REGION THIS WEEKEND. MULTIPLE SURFACE WAVES LOOK TO RIDE ALONG THIS FRONTAL BOUNDARY THROUGH THE WEEKEND. HIGH PRESSURE SHOULD MAKE A RETURN TO THE REGION EARLY NEXT WEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... A MID LEVEL SHORT WAVE TROUGH SHOULD LIFT NORTHEAST THROUGH THE DAY. THE QUESTION IS THOUGH, EXACTLY HOW CLOSE WILL IT COME TO THE REGION. BOTH THE NAM AND GFS SHOW THE TROUGH REMAINING NORTHWEST OF THE REGION AS INDICATED BY THE Q VECTOR AND VORTICITY FIELDS AT 850 AND 700 MB. IN ADDITION TO THE QUESTION OF HOW CLOSE THE TROUGH WILL BE TO THE REGION, THERE ARE A FEW OTHER LIMITING FACTORS FOR SHOWER/THUNDERSTORM DEVELOPMENT. FIRST, THE LIFT IS LIMITED TO THE MID LEVELS, AS THERE DOES NOT APPEAR TO BE A REFLECTION OF THIS SHORT WAVE TROUGH AT 500 MB. IN ADDITION, ANY UPPER LEVEL JETS ARE WELL SOUTH AND EAST OF THE REGION. SECOND, LOW LEVEL MOISTURE, ALTHOUGH SLIGHTLY HIGHER THAN YESTERDAY IS STILL LIMITED, AND THUS WILL LIMIT INSTABILITY. AS FOR TEMPERATURES...SHOULD SEE HIGHS A FEW DEGREES HIGHER THAN YESTERDAY AS CLOUD COVER SHOULD BE A BIT MORE LIMITED. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM THURSDAY/... THE PREVIOUSLY MENTIONED MID LEVEL SHORT WAVE TROUGH COMES A LITTLE CLOSER TO THE REGION THROUGH THE EVENING HOURS, BUT STILL REMAINS JUST NORTHWEST OF THE REGION. INSTABILITY AFTER 00Z IS LIMITED TO MEAGER ELEVATED INSTABILITY, SO ONLY EXPECT ISOLATED SHOWERS, IF ANYTHING. MOISTURE CONTINUES TO INCREASE, SO DESPITE THE LIGHT WINDS DO NOT EXPECT AS MUCH RADIATIONAL COOLING AS TUESDAY NIGHT, SO SHOULD SEE TEMPERATURES A FEW DEGREES HIGHER THAN TUESDAY MORNING. ANOTHER SHORTWAVE TROUGH BEGINS TO APPROACH THE REGION LATE TONIGHT, AND WHILE IT SHOULD STAY WEST OF THE REGION THROUGH THE TONIGHT PERIOD, THE COMBINATION OF THE HEIGHT FALLS IN ADVANCE OF THE TROUGH, AND WEAK ELEVATED INSTABILITY MAY BE ENOUGH FOR SOME SHOWER DEVELOPMENT AROUND SUNRISE THURSDAY MORNING, PRIMARILY IN THE NW PORTIONS OF THE REGION. && .LONG TERM /THURSDAY THROUGH TUESDAY/... NO DRAMATIC SHIFTS IN THE GUIDANCE OVER THE PAST 24 HOURS THOUGH IT IS BECOMING MORE APPARENT THAT THERE IS A SPLIT AMONGST THE NCEP VS. NON-NCEP GUIDANCE FOR THIS WEEKEND. THE DOMINATE FEATURE/DRIVING FORCE THROUGH THE END OF THE WORK WEEK. THEREAFTER, THE STRONGER TROUGH BEGINS TO BREAK DOWN WITH ITS CLOSED LOW OPENING UP AND MOVING OFF TOWARDS THE NORTH AND EAST OVER THE WEEKEND. A MUCH MORE BROAD BASED TROUGH REMAINS OVERHEAD THROUGH THE END OF THE PERIOD. THURSDAY...STRONGER SHORTWAVE INTERACTION WITH INCREASING COLUMN MOISTURE AND BETTER, NOT GREAT, INSTABILITY SHOULD LEAD TO WIDELY SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS...SOME AS EARLY AS LATE MORNING. INCREASED POPS ACCORDINGLY AND SPED UP THE TIMING OF THE SHOWERS DURING THE DAY...SREF PROBS AND PQPF FIELDS SHOW THIS TREND. TEMPERATURES SHOULD END UP BEING SEVERAL DEGREES BELOW NORMAL WITH AMPLE CLOUD COVER AND SHOWER ACTIVITY. FRIDAY...DEEPER MOISTURE ADVECTS INTO THE REGION WITH RIDGING OFFSHORE BUILDING AND HEIGHTS ACROSS THE EAST COAST BEGINNING TO INCREASE. BETTER INSTABILITY OVER THE EASTERN SECTIONS OF THE CWA WITH MORE MID-LEVEL IMPULSE ACTIVITY SHOULD LEAD TO EVEN MORE SCATTERED CONVECTION DURING THE PEAK HEATING HOURS. WEAK SURFACE CONVERGENCE UNDER A PREDOMINANT SOUTH-SOUTHEAST FLOW WILL AIDE IN BETTER LIFT FOR SHOWER ACTIVITY ALONG THE HIGHER TERRAIN. TEMPERATURES SHOULD AGAIN END UP COOLER THAN NORMAL. SATURDAY - SUNDAY...UPPER LEVEL JET DYNAMICS COME INTO PLAY MORESO THAN PREVIOUS DAYS WITH THE RIGHT ENTRANCE REGION SITTING ACROSS THE MID-ATLANTIC. OFFSHORE RIDGE CONTINUES TO BUILD AND PUSHES THE INVERTED TROUGH CLOSER TOWARDS THE REGION, AS A WARM FRONT OF SORTS. NUMEROUS WAVES MOVE ALONG THIS BAROCLINIC ZONE WITH VARIOUS DEGREES OF STRENGTH AND SPEED. AS STATED ABOVE THERE IS A SPLIT IN THE NUMERICAL GUIDANCE IN REGARDS TO THE TIMING AND LOCATION OF THESE WAVES. NCEP GUIDANCE HAS A SLOWER APPROACH THAN THE NON-NCEP MEMBERS AND ALSO WITH THEIR QPF FIELDS. NOT TOO PRUDENT TO RELY ON THE QPF OUTPUT STILL SEVERAL DAYS AWAY, BUT THE TREND MAY BE YOUR FRIEND...WETTER SOLUTION FOR US THIS WEEKEND. STILL LOTS OF UNCERTAINTY TO WORK WITH THOUGH THE GFS LOOKS IN LINE WITH THE GEFS WHILE THE EC AND ITS ENSEMBLE MEMBERS ARE IN CLOSE AGREEMENT. WE CONTINUE WITH THE CHANCE POPS GIVEN THE UNCERTAINTY BUT HAVE ADDED MODERATE RAIN TO THE FORECAST WITH THE AMOUNT OF AVAILABLE MOISTURE THAT COULD BE TAPPED INTO. MONDAY - TUESDAY...SLIGHT DRYING TREND EXPECTED ON MONDAY THOUGH NOT ENTIRELY VOID OF ANY SHOWERS WITH COLD AIR STILL ALOFT WITH A FEW MORE SHORTWAVES SHEARING ACROSS OVERHEAD. HIGH PRESSURE SHOULD BE NOSING IN BY TUESDAY TO ALLOW FOR BETTER DRYING. MORE MOISTURE AND HEAT ADVECTS IN AND COULD PUSH TEMPERATURES BACK TO NORMAL. && .AVIATION /08Z WEDNESDAY THROUGH SUNDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. VFR CONDITIONS ARE EXPECTED THROUGH THE TAF PERIOD. ONCE AGAIN...SHOULD SEE SCT TO POSSIBLY BKN CUMULUS CLOUDS AROUND 050. THERE IS A SMALL RISK OF SHRA AND TSRA NEAR KABE AND KRDG BETWEEN 18 AND 03Z...BUT COVERAGE IS EXPECTED TO BE VERY LIMITED SO NO MENTION IN THE TAFS FOR NOW. EXPECT SOUTHWESTERLY WINDS OF 5 TO 10KT THROUGH 00Z, BEFORE WINDS ONCE AGAIN BECOME LIGHT AND VRB. OUTLOOK... THURSDAY - FRIDAY...MOSTLY VFR WITH SCATTERED SHOWERS AND THUNDERSTORMS POSSIBLE EACH AFTERNOON. LOCAL SUB-VFR CONDITIONS IN SHOWERY ACTIVITY. MEDIUM CONFIDENCE. SATURDAY - SUNDAY...MOSTLY VFR. POSSIBILITY FOR WIDESPREAD SHOWERS AND THUNDERSTORMS EACH DAY CREATING MVFR/IFR CONDITIONS...SOME COULD BE HEAVY. MEDIUM CONFIDENCE ON POSSIBILITY, LOW CONFIDENCE WITH RESPECT TO COVERAGE. && .MARINE... EXPECT WINDS AND SEAS TO REMAIN BELOW SMALL CRAFT ADVISORY TODAY AND TONIGHT WITH WINDS STAYING BELOW 15 KT AND SEAS BETWEEN 2 AND 3 FEET. OUTLOOK... THURSDAY - SUNDAY...SUB-SCA CONDITIONS ARE EXPECTED ACROSS OUR WATERS THIS PERIOD. && .CLIMATE... RECORD LOWS FOR WEDNESDAY MORNING, JULY 30TH. PHILADELPHIA, PA....58 DEGREES SET IN 1981 AND 1914. WILMINGTON, DE......55 DEGREES SET IN 1956. ALLENTOWN, PA.......50 DEGREES SET IN 1997 AND 1968. READING, PA.........52 DEGREES SET IN 1981. ATLANTIC CITY, NJ...53 DEGREES SET IN 1981 AND 1968. TRENTON, NJ.........54 DEGREES SET IN 1997. GEORGETOWN, DE......54 DEGREES SET IN 1981. MOUNT POCONO, PA....42 DEGREES SET IN 1968. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...HEAVENER NEAR TERM...JOHNSON SHORT TERM...JOHNSON LONG TERM...HEAVENER AVIATION...HEAVENER/JOHNSON MARINE...HEAVENER/JOHNSON CLIMATE...

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