Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 250813 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 413 AM EDT FRI APR 25 2014 .SYNOPSIS... HIGH PRESSURE WILL MOVE OFFSHORE TODAY AS LOW PRESSURE ADVANCES EAST THROUGH THE OHIO VALLEY, CROSSING OUR REGION TONIGHT INTO SATURDAY MORNING. HIGH PRESSURE IS THEN EXPECTED TO INFLUENCE OUR AREA SATURDAY NIGHT THROUGH MONDAY. THE NEXT LOW PRESSURE SYSTEM LOOKS TO DEVELOP ACROSS THE PLAINS STATES MONDAY AND IS FORECAST TO BE SLOW-MOVING, RESULTING IN UNSETTLED WEATHER ACROSS OUR REGION FROM TUESDAY THROUGH THURSDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... HIGH PRESSURE WILL BE OVER THE REGION EARLY BUT MOVE EASTWARD THRU THE COURSE OF THE DAY. AS IT DOES, AN AREA OF LOW PRES OVER THE OH VLY WILL MOVE EWD AS WELL. CLOUDS WILL INCREASE, THICKEN AND LOWER AS THE DAY PROGRESSES. WHILE MOST OF THE DAY LOOKS TO BE DRY, RAIN WILL DEVELOP FROM W TO E BY LATE AFTN/ERLY EVE. TEMPS SHOULD END UP RIGHT AROUND NRML AND IT WILL BE MUCH LESS WINDY THAN IT HAS BEEN OVER THE LAST FEW DAYS. BASED ON CURRENT TEMPS AND LONGER DAYLIGHT HOURS, HAVE OPTED TO DROP THE FREEZE WARNING..FOR ALL BUT SUSSEX AND WARREN COUNTIES. THERE COULD BE SOME SPOTS THAT MAKE IT TO FREEZING OR CLOSE, BUT DO NOT EXPECT WIDESPREAD FREEZING TEMPS ATTM. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SATURDAY/... THE AFOREMENTIONED LOW PRES WILL MOVE ACRS THE REGION DURG THE FIRST PART OF TONIGHT BRINGING RAIN TO THE AREA. RUMBLES OF THUNDER CAN NOT BE RULED OUT, ESPECIALLY OVER THE SRN AREAS. THE LOW AND ITS ATTENDANT CDFNT WILL MOVE THRU OVERNIGHT AND PRECIP SHUD END FROM SW TO NE BY DAYBREAK. && .LONG TERM /SATURDAY THROUGH THURSDAY/... TO START THE LONG TERM, AN AREA OF SURFACE LOW PRESSURE IS FORECAST TO BE PASSING BY TO OUR NORTHEAST SATURDAY MORNING, WITH MUCH OF THE SCATTERED/ISOLATED SHOWER ACTIVITY DIMINISHING AT THAT TIME. HOWEVER, THE PRIMARY UPPER LEVEL TROUGH/CLOSED LOW IS PROGGED TO DROP SOUTHEAST FROM THE NORTHERN GREAT LAKES INTO NEW YORK STATE THROUGH THE COURSE OF THE DAYTIME SATURDAY, AND WITH COLDER AIR PRESENT ALOFT IN THE ATMOSPHERE, MORE SCATTERED SHOWERS WILL BE THE RESULT. THE GFS/NAM AND ECMWF ALL SHOW SOME VERY MARGINAL INSTABILITY TO BE PRESENT SATURDAY AFTERNOON TO EARLY EVENING, BUT WE OPTED NOT TO ADD THUNDER AT THIS TIME AS WHAT MAY OCCUR IS ONLY SOME LOW-TOPPED CONVECTIVE ACTIVITY. THROUGH THIS TIMEFRAME, WE KEEP SLIGHT CHANCE TO LOW CHANCE POPS FOR ISOLATED/SCATTERED SHOWERS. BY LATER SATURDAY NIGHT AND EARLY SUNDAY, THE UPPER LEVEL TROUGH/CLOSED LOW IS FORECAST TO MOVE EAST AND OFF THE NEW ENGLAND COAST AS HIGH PRESSURE NOSING DOWN FROM CANADA BEGINS TO INFLUENCE OUR REGION. WEAK HIGH PRESSURE IS PROGGED TO REMAIN ACROSS THE MID ATLANTIC THROUGH THE DAYTIME SUNDAY THROUGH MONDAY, AND WE MAINTAIN A DRY FORECAST THROUGH THIS PERIOD WITH TEMPERATURES OVERALL RUNNING A FEW DEGREES BELOW LATE APRIL NORMALS. A MORE ACTIVE AND UNSETTLED PATTERN LOOKS TO TAKE SHAPE THROUGH THE MIDWEEK PERIOD AS A SLOW-MOVING LOW PRESSURE SYSTEM ORGANIZES ACROSS THE PLAINS STATES MONDAY AND THEN GRADUALLY PROGRESSES EAST. WE HAVE KEPT THE MENTION OF SLIGHT CHANCE/LOW CHANCE POPS FOR SHOWERS IN THE FORECAST FOR LATE MONDAY NIGHT AS MORE OF AN ONSHORE FLOW DEVELOPS ACROSS OUR REGION. FROM THERE, POPS INCREASE MOSTLY INTO THE HIGH CHANCE/LOW LIKELY RANGE FOR THE TUESDAY THROUGH THURSDAY TIMEFRAME AS THE SURFACE AND UPPER LEVEL LOWS ADVANCE INTO THE MISSISSIPPI VALLEY AND A FEW MID/UPPER SHORTWAVES PASS NEAR OR OVER OUR REGION BRINGING ROUNDS OF SCATTERED SHOWERS. WHILE SOME EMBEDDED THUNDER IS POSSIBLE AT TIMES WITH THIS ACTIVITY, WE HAVE NOT INCLUDED THUNDER AT THIS EXTENDED TIMEFRAME AS THERE IS STILL UNCERTAINTY REGARDING THE AMOUNT OF INSTABILITY PRESENT AS AN ONSHORE, EASTERLY FLOW LOOKS TO HOLD ON THROUGH MIDWEEK. WITH CLOUDS AND SHOWERS AROUND, DAYTIME TEMPERATURES ARE EXPECTED TO RUN WELL BELOW AVERAGE, WITH HIGHS ONLY IN THE 50S FOR MUCH OF THE REGION, ESPECIALLY TUESDAY AND WEDNESDAY. && .AVIATION /08Z FRIDAY THROUGH TUESDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. VFR CONDS ARE EXPECTED FOR THE FIRST PORTION OF THE TAF PD WITH HIGH PRES OVER THE REGION, GRADUALLY MOVG EWD. THEN CONDS WILL DETERIORATE AS LOW PRES, OVER THE OH VLY MOVES EWD AND BRINGS RAIN TO THE REGION. CONDS WILL DROP TO MVFR AND PSBL IFR BEGINNING LATE THIS AFTN/ERLY THIS EVE FROM W TO E. RAIN SHUD END FROM SW TO NE DURING THE OVERNIGHT HOURS. THE WIND WILL BE MUCH LOWER THAN THE LAST 2 DAYS WITH SELY WIND GUSTS PSBLY AS HIGH AS 15 TO 20 KTS DURG THE DAY. THE WIND WILL THEN BECOME LESS THAN 10 KTS THIS EVE AND MAY EVEN BECOME LIGHT AND VARIABLE FOR A TIME BEFORE SHIFTING TO THE NW AFTER CFP LATE TONIGHT. OUTLOOK... SATURDAY...ANY SUB-VFR CONDITIONS IMPROVE BACK TO VFR EARLY SATURDAY MORNING. SOME SCATTERED SHOWERS ARE POSSIBLE FOR SATURDAY AFTERNOON, BUT CONDITIONS SHOULD REMAIN MAINLY VFR. SUNDAY AND MONDAY...MAINLY VFR CONDITIONS WITH WEAK HIGH PRESSURE. AN ONSHORE FLOW IS EXPECTED TO DEVELOP MONDAY NIGHT WITH SOME MVFR CEILINGS POSSIBLE INTO EARLY TUESDAY. TUESDAY...MVFR CEILINGS ANTICIPATED TO DEVELOP WITH AN ONSHORE FLOW. SOME RAIN IS FORECAST TO OVERSPREAD THE AREA FROM SOUTH TO NORTH, WITH CONTINUED MVFR CONDITIONS. && .MARINE... NO MARINE HEADLINES WILL BE CARRIED FOR THE NEAR AND SHORT TERM PDS WITH HIGH PRES OVER THE AREA MOVG SLOWLY EWD. BY THE END OF THE PD...ERLY SAT MRNG, WIND MAY INCREASE AS LOW PRES MOVES THRU THE REGION AND WE MAY APPROACH SCA CRITERIA. HOWEVER, CONFIDENCE WAS NOT HIGH ENOUGH TO ISSUE A AN ADVY ATTM. OUTLOOK... SATURDAY...POSSIBLE SCA CONDITIONS MAY BEGIN THE DAY ACROSS THE AREA WATERS AS LOW PRESSURE PASSES BY TO THE NORTHEAST, BUT IMPROVEMENT TO SUB-SCA SHOULD BE RELATIVELY QUICK BY SATURDAY AFTERNOON/EVENING. SUNDAY AND MONDAY...MAINLY SUB-ADVISORY CONDITIONS ARE EXPECTED. TUESDAY...AN EASTERLY ONSHORE FLOW IS EXPECTED; ALTHOUGH, WIND GUSTS LOOK TO REMAIN SUB-ADVISORY AT THIS TIME. SEAS, HOWEVER, ARE EXPECTED TO BUILD FOR THE COASTAL WATERS INTO THE 5 FOOT RANGE. && .FIRE WEATHER... THERE LOOKS TO BE AN ELEVATED FIRE RISK AGAIN TODAY, THOUGH LESS THAN YESTERDAY, ESPECIALLY FOR EASTERN PENNSYLVANIA AND NEW JERSEY. TEMPERATURES WILL BE A FE DEGREES WARMER. BUT THE WIND IS ONLY EXPECTED TO GUST IN THE 15 TO 20 MPH RANGE FROM LAT THIS MORNING INTO THE EARLY AFTERNOON. THE AIRMASS IS STILL VERY DRY AND RELATIVE HUMIDITY VALUES ARE EXPECTED TO DROP INTO THE 20S FOR A TIME. HOWEVER, LOW PRESSURE WIS APPROACHING FROM THE WEST AND BY LATE AFTERNOON, HUMIDITY VALUES ARE EXPECTED TO INCREASE AND RAIN IS ANTICIPATED BY LATE AFTN/ERLY EVE. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...FREEZE WARNING UNTIL 8 AM EDT THIS MORNING FOR NJZ001-007. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...KLINE NEAR TERM...NIERENBERG SHORT TERM...NIERENBERG LONG TERM...KLINE AVIATION...KLINE/NIERENBERG MARINE...KLINE/NIERENBERG FIRE WEATHER...

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