Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 051446 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 946 AM EST THU MAR 5 2015 .SYNOPSIS... A COUPLE OF WAVES OF LOW PRESSURE WILL TRACK SOUTHEAST OF THE REGION TODAY AND THIS EVENING. A HIGH PRESSURE SYSTEM WILL MOVE INTO THE REGION ON FRIDAY AND THEN SINK TO THE SOUTHEAST ON SATURDAY. A WEAK CLIPPER TYPE LOW PRESSURE SYSTEM SHOULD PASS NORTH OF THE AREA ON SATURDAY NIGHT FOLLOWED BRIEFLY BY ANOTHER HIGH PRESSURE SYSTEM ON SUNDAY. A COLD FRONT SHOULD PASS THROUGH THE REGION ON MONDAY. ANOTHER HIGH PRESSURE SYSTEM SHOULD THEN BUILD INTO THE AREA ON TUESDAY AND WEDNESDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... SNOW IS IN PROGRESS ACROSS THE REGION WITH AREAS ACROSS SOUTHEAST NJ AND THE SOUTHERN DELMARVA CHANGING FROM SLEET AND RAIN TO SNOW IN THE NEXT FEW HOURS. THE BACK EDGE OF THE SNOW IS APPROACHING THE NORTHWEST PARTS OF THE REGION. CAA WILL CONTINUE TO PUSH INTO THE REGION BEHIND A COLD FRONT WITH A CONTINUING STREAM OF OVERRUNNING MOISTURE. TEMPERATURES WILL CONTINUE TO DROP TODAY ACROSS THE AREA AND ONLY A FEW ADJUSTMENTS WERE MADE WITH THE 9:30 AM UPDATE. PRECIPITATION SHOULD END VERY SLOWLY FROM NORTH TO SOUTH THIS AFTERNOON. WIND GUSTS AROUND 20 MPH HAVE ALSO BEEN REPORTED IN SPOTS AND THESE WERE INCREASED WITH THE 9:30 AM UPDATE. ONTO SNOW AMOUNTS IN THE ADVISORY AREA A FEW INCHES HAVE ALREADY FALLEN WITH THE POTENTIAL FOR SOME ADDITIONAL ACCUMULATION WITH TOTALS STILL LOOKING TO AVERAGE UNDER WARNING CRITERIA. FURTHER SOUTH TOWARD THE PHILADELPHIA METRO AREA MODERATE TO HEAVY SNOW BANDS HAVE SETUP ACROSS THIS REGION WITH REPORTS OF 1 TO AS MUCH AS 2 INCHES PER HOUR FOR SHORT INTERVALS. THE RAP AND HRRR BOTH INDICATE THAT THESE MESOSCALE BANDS WILL BE SOMEWHAT PROGRESSIVE BUT CONTINUE THROUGHOUT THE DAY TODAY. THESE BANDS ARE CAUSED BY SIGNIFICANT FRONTGENETICAL FORCING AND AMPLE ISENTROPIC LIFT. STORM TOTALS OF 6-8 INCHES STILL LOOK ON TRACK ATTM. ALSO PLEASE REFER TO MCD 124 FROM THE SPC AND THE SPS WE HAVE IN EFFECT. IN THE DELMARVA AND SOUTHEAST NJ, THE 9:30 AM UPDATE SLOWS THE CHANGEOVER AN HOUR OR SO. HOWEVER STILL DO NOT THINK THIS WILL CUT INTO TOTALS EXTENSIVELY ATTM. THIS IS DUE TO THE SAME MESOSCALE BANDING SIGNATURES SINKING FURTHER SOUTH FOR THE AFTERNOON HOURS. THIS IS PICKED UP WELL BY THE RAP, HRRR AND 06Z 800-600 MB FRONTGENETICAL FORCING ON THE 06Z NAM FROM EARLIER TODAY. SNOWFALL MAY ALSO FALL AROUND AN INCH FOR A TIME THIS AFTERNOON LEADING TO 4-8 INCHES OF SNOW BY EVENING. ROAD CONDITIONS WILL CONTINUE TO DETERIORATE TODAY WITH THE SNOW, ALLOW EXTRA TIME IF YOU HAVE TO TRAVEL. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM FRIDAY/... THE LAST OF THE STEADY SNOWS WILL PASS EAST OF THE FORECAST AREA THIS EVENING. SKIES WILL BE CLOUDY EARLY THEN THE CLOUDS WILL BREAK UP FROM N/W TO S/E OVERNIGHT. THE LACK OF CLOUDS LATE AND THE FRESH SNOW COVER SHOULD PRODUCE COLD TEMPS OVERNIGHT...WITH LOWS IN THE SINGLE DIGITS AND A FEW SUB-ZERO READINGS FAR NORTH. WIND CHILLS MAY DROP TO NEAR -12 TO -15 ACROSS MOUNT POCONO...BUT REMAIN MORE LIKE 0 TO -10 ELSEWHERE. WINDS WILL BE MOSTLY NRLY AT 5 TO 10 MPH. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... THE GFS INITIALIZATION LOOKED SLIGHTLY BETTER THERMALLY, BUT IT WAS A COLD OP RUN IN COMPARISON TO ITS ENSEMBLE MEAN AND OTHER MODELS. OVERALL AFTER TODAY, THE LONG TERM IS RELATIVELY QUIET WITH TEMPERATURES RETURNING TO NEAR NORMAL VALUES AND NOT MUCH PCPN EXPECTED. A BRIGHT SUNNY DAY IS EXPECTED ON FRIDAY WITH NOT MUCH WIND. THE ONE CATCH IS THAT TEMPERATURES WILL BE WELL BELOW AVERAGE, EVEN IF IT WERE STILL JANUARY. MAX TEMPS ARE CLOSE TO THE FULL SUN MACROS AND THE HIGHER NAM STAT GUIDANCE. ON FRIDAY NIGHT WE CONTINUED THE IDEA OF GOING EITHER WITH THE LOWER STAT GUIDANCE IN URBAN AREAS OR BELOW ALL FOR MINS GIVEN WE ARE EXPECTING RADIATIONAL COOLING CONDITIONS. THERE IS A SHORT WAVE TROF THAT MIGHT SPILL SOME CLOUDS THROUGH PART OF THE NIGHT, ONLY REASON WE DID NOT GO EVEN LOWER. SATURDAY THE AIR MASS RECOVERY WILL START AS A HIGH PRESSURE SYSTEM REACHES THE COAST. THERE SHOULD BE MORE CLOUDS AROUND ASSOCIATED WITH THE WAA PHASE OF THE CLIPPER WHICH SHOULD SLOW TEMP RISE A BIT. WE ARE CLOSER TO NAM STAT GUIDANCE FOR MAX TEMPS AS BY NOW THE GEFS MEAN IS WARMER THAN THE OP GFS. ON SATURDAY NIGHT, CONTINUED WITH THE IDEA THAT THE WEAKENING CLIPPER MIGHT BRING SOME SNOW SHOWERS TO THE NORTHERN PART OF OUR CWA. PRECIPITATION INTENSITY AS OF NOW APPEARS LIGHT IF THEY MAKE IT. SUNDAY, THE MODERATION TREND IS EXPECTED TO CONTINUE AS THE CLIPPER`S DEMISE SHOULD NOT BRING ANY COLDER AIR BACK INTO THE REGION. A NORTHERN STREAM COLD FRONT COULD BRING THE CHANCE OF SHOWERS BACK INTO THE AREA ON MONDAY AND BY THEN IT MIGHT BE WARM ENOUGH FOR THE PTYPE TO FALL AS RAIN. A SOUTHERN STREAM LOW PRESSURE SYSTEM IS EXPECTED TO REMAIN SEPARATE WITH ITS PREDICTED PCPN FOR NOW REMAINING SOUTHEAST OF OUR AREA. THEN A HIGH PRESSURE SYSTEM ENTERING FROM THE PACIFIC OCEAN (INSTEAD OF TAKING THE POLAR ROUTE) FOR A CHANGE IS EXPECTED TO BRING TEMPERATURES CLOSE TO SEASONAL LEVELS FOR TUESDAY AND WEDNESDAY. && .AVIATION /15Z THURSDAY THROUGH MONDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. CONDITIONS WILL CONTINUE TO DETERIORATE THIS MORNING WITH CIGS/VSBYS IN THE IFR/LIFR RANGE IN SNOW. THE CHANGE- OVER WILL OCCUR BY 15Z AT ACY WITH MOST LOCATIONS SEEING SNOW WELL INTO THE AFTERNOON. SOME LOWER VSBYS AROUND 1/4 MILE COULD BE OBSERVED AS WELL LOCALLY FOR SHORT INTERVALS, WHICH WERE NOT INCLUDED IN THE TAFS. ALSO, ISOLATED WIND GUSTS AROUND 20 KNOTS ARE POSSIBILE TODAYBUT COVERAGE LOOKS LOW ENOUGH NOT TO MENTION IN TAFS ATTM. IMPROVEMENT TO MVFR IS POSSIBLE AFTER 20Z WITH VFR CONDITIONS AROUND 00-03Z AS CLOUDS CLEAR. RUNWAY SNOW ACCUMULATION IS POSSIBLE TO LIKELY TODAY. OUTLOOK... FRIDAY THROUGH SATURDAY...PRIMARILY VFR. SATURDAY NIGHT...SOME MVFR CIGS POSSIBLE, MAINLY NORTH ALONG WITH A LOW CHANCE OF SNOW SHOWERS. SUNDAY AND SUNDAY NIGHT...PRIMARILY VFR. MONDAY...PRIMARILY VFR, LOCALLY MVFR IN SHOWERS. && .MARINE... WE WILL KEEP THE SCA FLAG FOR TODAY...AND EXTEND THE EXPIRATION TIME INTO TONIGHT. WINDS AND SEAS WILL INCREASE ACROSS THE WATERS AS CAA CONTINUES. IT APPEARS THAT GUSTS IN THE 25 TO 30 KNT RANGE ARE POSSIBLE ACROSS THE OCEAN WATERS AND AROUND 20 KTS ACROSS DEL BAY. THERE WILL BE RAIN/SNOW EARLY TODAY...THEN SNOW INTO THE AFTERNOON. FAIR WEATHER EXPECTED TONIGHT. OUTLOOK... FRIDAY AND FRIDAY NIGHT...CONDITIONS SHOULD RETURN TO SUB SMALL CRAFT ADVISORY LEVELS. FREEZING SPRAY IS LIKELY, NOT CONFIDENT ENOUGH ABOUT MODERATE FREEZING SPRAY OCCURRING ON FRIDAY MORNING TO ISSUE AN ADVISORY. SATURDAY THROUGH MONDAY...SUB SMALL CRAFT ADVISORY CONDITIONS ARE OUTLOOKED TO PREVAIL MAINLY DUE A COMBINATION OF RELATIVELY WEAK PRESSURE SYSTEMS AND ALSO WHERE THERE WILL BE STRONGER WINDS ABOVE THE BOUNDARY LEVEL, IT SHOULD BE AT TIMES WHEN THE AIR TEMPS WILL BE HIGHER THAN THE WATER TEMPS. && .HYDROLOGY... WITH THE TRANSITION BACK TO SNOW TODAY (IF NOT ALREADY), THE HYDROLOGICAL CONCERNS AT LEAST IN THE NEAR TERM ARE LESSENING. WE ARE STILL MONITORING GAGED SITES TO CHECK FOR JAMS. && .CLIMATE... CLIMATE: WITH A SNOWCOVER IN PLACE AND ANOTHER MODIFIED ARCTIC AIRMASS SETTLING INTO THE REGION AND RADIATIONAL COOLING OCCURRING, WE HAVE ANOTHER CHANCE FOR MORE RECORD LOWS ACROSS THE REGION. FRIDAY 3/6 RECORD LOWS ACY 10 1888 PHL 10 1978 ILG 11 1926 ABE 7 1960 TTN 7 1872 GED 10 1978 RDG 7 1978 MPO -5 1909 THE CURRENT FORECAST CURRENTLY HAS MOST LOCATIONS BREAKING THERE RECORD LOW ON FRIDAY MORNING. THE ONE EXCEPTION WOULD BE MOUNT POCONO. SATURDAY 3/7 RECORD LOWS ACY 10 1890 PHL 9 1960 ILG 11 1960 ABE 1 1960 TTN 7 1890 GED 3 1960 RDG 10 1989 MPO -18 1911 ASIDE FROM ATLANTIC CITY, MOST LOCATIONS ARE FORECASTED TO BE SEVERAL DEGREES WARMER THAN THE RECORD LOWS FOR SATURDAY MORNING. RECORD DAILY SNOWFALL FOR THURSDAY MARCH 5 KACY 0.3 - 1960 KILG 3.7 - 1981 KABE 7.0 - 1917 KPHL 8.8 - 1981 && .PHI WATCHES/WARNINGS/ADVISORIES... PA...WINTER WEATHER ADVISORY UNTIL 7 PM EST THIS EVENING FOR PAZ054- 055-061-062. WINTER STORM WARNING UNTIL 7 PM EST THIS EVENING FOR PAZ060- 070-071-101>106. NJ...WINTER WEATHER ADVISORY UNTIL 7 PM EST THIS EVENING FOR NJZ001- 007-008. WINTER STORM WARNING UNTIL 7 PM EST THIS EVENING FOR NJZ009- 010-012>027. DE...WINTER STORM WARNING UNTIL 7 PM EST THIS EVENING FOR DEZ001>004. MD...WINTER STORM WARNING UNTIL 7 PM EST THIS EVENING FOR MDZ008- 012-015-019-020. MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EST FRIDAY FOR ANZ450>455. && $$ SYNOPSIS...GIGI NEAR TERM...GAINES SHORT TERM...O`HARA LONG TERM...GIGI AVIATION...GAINES/GIGI/O`HARA MARINE...GIGI/O`HARA HYDROLOGY... CLIMATE...

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