Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000
FXUS61 KPHI 272316
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
616 PM EST FRI FEB 27 2015

.SYNOPSIS...
STRONG AND EXTENSIVE HIGH PRESSURE CENTERED OVER THE MIDWEST ARRIVES
ALONG THE MID ATLANTIC COAST THIS WEEKEND. A WEAK WARM FRONT LIFTS
THROUGH OUR AREA LATE SUNDAY NIGHT FOLLOWED QUICKLY BY A COLD FRONT
MONDAY MORNING. COLD HIGH PRESSURE RETURNS MONDAY NIGHT. LOW
PRESSURE IN THE CENTRAL PLAINS TUESDAY MOVES TO OUR NORTH WEDNESDAY.
ITS COLD FRONT PASSES THROUGH OUR AREA WEDNESDAY NIGHT, POSSIBLY
WITH AN ATTENDANT WAVE OF LOW PRESSURE. EXPANSIVE HIGH PRESSURE IN
THE CENTRAL PLAINS SLOWLY FILTERS INTO OUR AREA LATE NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
JUST SOME TEMPERATURE SMOOTHING WITH THIS UPDATE. FORECAST IS
ON/CLOSE TO SCHEDULE.

HIGH PRESSURE WILL GRADUALLY BUILD EASTWARD FROM THE OHIO VALLEY
THIS EVENING. THIS WILL ALLOW FOR MOSTLY CLEAR SKIES TONIGHT AS
CLOUDS ALONG THE COAST MOVE OFFSHORE. CONDITIONS WILL BE FAVORABLE
FOR RADIATIONAL COOLING AS WELL WITH NORTHWEST WINDS UNDER 10 MPH.
TEMPERATURES INCORPORATE THE GFS MODELED TWO METER TEMPERATURES
WHICH SEEM TO HAVE BETTER HANDLED THE SNOWCOVER AND THE MET/MAV
GUIDANCE SETS. SINGLE DIGITS FOR MOST OUTSIDE OF PHILADELPHIA
TONIGHT. CLIMATE SECTION HAS MORE ON THE THREAT FOR ANY RECORDS.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/...
SATURDAY LOOKS LIKE A PLEASANT BUT COLD DAY ACROSS THE REGION.
NORTHWEST WINDS WILL CONTINUE TO BE UNDER 10 MPH, PERHAPS SHIFTING
TO MORE WESTERLY LATE. WITH THE HIGH PRESSURE IN PLACE ONLY SOME
HIGH CIRRUS IS EXPECTED WITH SOME ADVECTING MID AND UPPER LEVEL
MOISTURE IN THE AFTERNOON. THE MET AND MAV GUIDANCE SETS HAVE BEEN
TO COOL WITH HIGHS IN RECENT SUNNY DAYS, WENT A COUPLE DEGREES
WARMER WITH HIGHS DUE TO RECENT TRENDS.

&&

.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
**WINTERY WX EVENTS SLATED FOR SUNDAY NIGHT AND TUESDAY NIGHT AT
  LEAST IN EASTERN PA AND NW NJ**

500MB: A SHORT WAVE IN SOUTH CENTRAL CANADA SATURDAY NIGHT MOVES
TO NEW ENGLAND MONDAY; THEN A PARTIAL PHASING OF SOUTHERN AND
NORTHERN STREAM SHORT WAVES OCCURS MONDAY NIGHT AND TUESDAY IN
THE PLAINS STATES. THAT TROUGH MOVES TO QUEBEC WEDNESDAY WHILE A
TRAILING SHORT WAVE FOLLOWS TO THE EAST COAST THURSDAY. BROAD
NORTHWESTERLY FLOW FOLLOWS NEXT FRIDAY ACROSS EASTERN NORTH
AMERICA.

TEMPERATURES: WE`RE IN THE PROCESS OF CLOSING OUT THE TOP 5 OR 6
COLDEST FEBRUARY IN LONG TERM CLIMAT HISTORY DATING BACK TO THE
1870S; THE CALENDAR DAY AVERAGE TEMPERATURE SUNDAY SHOULD BE CLOSE
TO 15 DEGREES BELOW NORMAL WITH A SMALL CHANCE OF RECORD LOWS SUNDAY
MORNING IN THE RADIATIONAL COOLING COUNTRYSIDE NEAR ATLANTIC CITY
AND MAYBE NEAR TRENTON, DEPENDENT ON WHETHER THICK CLOUD COVER
ARRIVES AT 06Z OR 9Z. A LATER ARRIVAL PERMITS A BETTER CHC OF RECORDS.
MONDAY SHOULD BE CLOSE TO OR SLIGHTLY BELOW NORMAL BUT IT COOLS
AGAIN ON TUESDAY TO ABOUT 10 DEGREES BELOW NORMAL. WEDNESDAY IS
PROBABLY THE WARMEST DAY OF THE WORKWEEK, WITH POTENTIAL 50S TO
LOWER 60S I-95 SEWD AND CALENDAR DAY AVERAGE TEMPS SEVERAL DEGREES
ABOVE NORMAL. THEREAFTER, THE 12Z/27 ECMWF ECMWF OPERATIONAL RUN
HAS COME INTO GREATER AGREEMENT WITH THE GFS ON ANOTHER COLD SHOT
AT THE END OF NEXT WEEK, DAYTIME MAX TEMP COLD BIAS
NOTWITHSTANDING. TEMPS MAY RUN 5 DEGREES OR MORE BELOW NORMAL BOTH
THURSDAY AND FRIDAY.

FORECAST BASIS: UNLESS OTHERWISE NOTED, 50 50 BLEND 12Z/27
GFS/NAM MOS GUIDANCE SATURDAY NIGHT-SUNDAY NIGHT, 12Z/27 MEX MOS
MONDAY AND MONDAY NIGHT THEN THE 15Z/27 WPC GRIDDED ELEMENTS OF
MAX/MIN TEMP, 12 HOUR POP, 6 HOUR DEWPOINT-SKY-WIND FROM TUESDAY-
NEXT FRIDAY.

THE DAILIES...

SATURDAY NIGHT...CLEAR TO PARTLY CLOUDY (CIRRUS EARLY EVENING)
WITH STRONG COUNTRYSIDE RADIATIONAL COOLING AND NEAR RECORD LOWS
POSSIBLE KTTN AND KACY, THEN CLOUDING UP RAPIDLY TOWARD SUNRISE.
LIGHT WIND. RECORDS DEPENDENT ON TIMING OF THE ARRIVAL OF THICK
CLOUD COVER. THE WARMER NAM TEMPS WERE NOT FACTORED INTO THIS
SATURDAY NIGHT FORECAST AT ALL. GFS 2M TEMPS ARE A SIGNIFICANT
INDICATOR OF RADIATIONAL COOLING.

ADVISORY EVENT HIGHLY PROBABLY SUNDAY AFTERNOON AND NIGHT.

SUNDAY AND SUNDAY NIGHT...CLOUDY: PRECIPITATION DEVELOPS MIDDAY OR
SUNDAY AFTERNOON. PHL SEWD A TINY BIT OF SNOW CHANGING TO SLEET AND
FREEZING RAIN. MOSTLY LIGHT SOUTH WIND. MEANWHILE SNOW ACCUMULATES
NW OF I-95 AND WHILE WE JUST DON`T KNOW HOW MUCH (2 TO 6"--HEAVIEST
SOMEWHERE N OF I-78), WE DO SEE THE NAM THERMAL PROFILES ARE SUBFREEZING
FOR QUITE A BIT OF TIME SO THAT EVEN IF A WARM ABOVE FREEZING NOSE
POKES NORTHWARD, WE ARE THEN LOOKING AT ICE. LIGHT WIND.

MOST OF THE SNOW ACCUMULATION IS PROBABLY 5 PM TO MIDNIGHT.

THERE IS CONCERN THAT THIS EVENT WILL END UP MOSTLY SNOW AND LESS
FREEZING RAIN. HOWEVER...SE OF I95 WE SHOULD WARM ENOUGH TO
EXPERIENCE A BIT OF NON FREEZING RAIN AFTER 08Z MONDAY.

ONE CAUSE OF THE PCPN IS AN INSTABILITY BURST HEADED FOR THE DELMARVA.

MONDAY...ANY LEFTOVER SHOWERS AT SUNRISE QUICKLY END ALONG THE
COAST, THEN AT LEAST PARTIAL CLEARING WITH NW WINDS GUSTING
AROUND 35 MPH DURING THE AFTERNOON WITH STRONG CAA.

MONDAY NIGHT...CLEAR RADIATIONAL COOLING FOLLOWED BY INCREASING HIGH
CLOUDS AFTER MIDNIGHT.   LIGHT WIND.

TUESDAY...THICKENING CLOUDS.  CHANCE OF SNOW LATE IN THE DAY?  LIGHT
SOUTH WIND.

TUESDAY NIGHT...ANY MIXED WINTRY PCPN QUICKLY CHANGES TO RAIN I-95
SEWD BUT NW OF I-95 SNOW CHANGES TO ICE AND THEN PROBABLY RAIN.
TIMING UNCERTAIN. LIGHT SOUTH WIND SHIFT SW LATE. ANOTHER STRONG
INSTABILITY BURST THAT NOSES TO THE DELMARVA.

WEDNESDAY...CONSIDERABLE CLOUDINESS AND MILDER. HOW MILD IS A BIT
UNCERTAIN BUT POTENTIALLY FLIRTING WITH 60 PHL SEWD?, COOLER TO
THE NORTH AND WARMTH DEPENDENT IN PART ON SOUTHWEST FLOW MIXING.
SW WIND SHIFTS TO NW.

WEDNESDAY NIGHT-THURSDAY MORNING...THE CFP TO BE ACCOMPANIED BY A
PERIOD OF SHOWERS. IF A WAVE FORMS ON THE FRONT THEN POSSIBLY
ENDING AS A TOUCH OF SNOW?

THURSDAY AFTERNOON...TURNING MUCH COLDER. NW WIND GUSTY 25-30
MPH.

FRIDAY...FAIR AND COLD.  W-NW WIND GUST 20 MPH.

&&

.AVIATION /23Z FRIDAY THROUGH WEDNESDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE,
KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS.

THE 00Z TAFS ARE VFR WITH TRANQUIL WEATHER CONDITIONS ASIDE FROM
THE UNSEASONABLY COLD TEMPERATURES.

FOR TONIGHT...CLEAR SKIES THIS EVENING. POSSIBLY SOME CIRRUS/HIGH
BASED ALTOCU FROM THE LOWER OHIO VALLEY OVERNIGHT. WINDS WILL VEER
MORE TO THE NORTH. FORECAST GROUP SHOWS AN AVERAGE WIND DIRECTION
FOR THE ENTIRE FORECAST PERIOD. SPEEDS ARE WEIGHED MORE TO THE
EVENING, OVERALL THOUGH SHOULD BE LESS THAN 10 KNOTS AND MORE
RURAL TERMINALS AND AIRPORTS WILL GO LIGHT AND VARIABLE LATER
TONIGHT. NO VSBY RESTRICTIONS.

SATURDAY...VFR. POSSIBLY SLIGHTLY MORE CIRRUS OR HIGH BASED ALTO
CU. WINDS WILL BE LIGHT FROM THE NORTH AVERAGING AROUND 5 KNOTS.

OUTLOOK...
SATURDAY NIGHT - SUNDAY MORNING...VFR CLEAR TO START WITH LIGHT
WIND THEN RAPIDLY LOWERING CIGS TO NEAR 5000 FT FROM WEST TO EAST
IN THE 09Z-17Z TIME FRAME.

SUNDAY AFTERNOON AND NIGHT...MVFR OR IFR CONDS IN SNOW CHANGING TO
RAIN VCNTY KPHL SOUTH AND EAST AND SNOW CHANGING TO ICE
KRDG/KABE/KTTN/KPNE. LIGHT WIND.

MONDAY...BECOMING VFR WITH A GUSTY NW WIND 30 TO POSSIBLY 35 KT
IN THE AFTERNOON.

TUESDAY...VFR CIRRUS THEN MVFR OR IFR CONDS DEVELOPING IN SNOW LATE
IN THE DAY CHANGING TO ICE OR RAIN AT NIGHT. LIGHT SOUTH WIND.

WEDNESDAY...VFR CIGS DEVELOPING AFTER ANY LEFTOVER MORNING IFR OR
MVFR CONDS IN SHOWERS? SW WIND SHIFTING NW.

&&

.MARINE...
THE SCA WILL BE EXTENDED FOR A COUPLE MORE HOURS AS SEAS CONTINUE
TO LINGER AT AROUND 5 FEET ON THE OCEAN.

SEAS HAVE LOWERED TO AROUND FIVE FEET AND WILL CONTINUE TO SLOWLY
GET LOWER THROUGHOUT THE NIGHT. WAVEWATCH GUIDANCE LOOKS TO QUICK
TO LOWER THE SEAS THROUGH SATURDAY MORNING. SEAS AND WINDS WILL
REMAIN BELOW SCA CRITERIA THROUGH SATURDAY. CONTINUED
NORTHWESTERLY WINDS ON SATURDAY AROUND 10 KNOTS.OUTLOOK...

OUTLOOK...
SATURDAY NIGHT - SUNDAY...SUB-SCA EXPECTED.

SUNDAY NIGHT - MONDAY...POSSIBLE SCA CONDITIONS LATE ON SUNDAY
AHEAD OF AN APPROACHING COLD FRONT WITH INCREASING SOUTHERLY
WINDS AND BUILDING SEAS EXPECTED.

NW GALE POTENTIAL FOR ABOUT 6 HOURS MONDAY MIDDAY AND AFTERNOON.

TUESDAY...SUB-SCA EXPECTED.

&&

.HYDROLOGY...
TWO PRECIPITATION EVENTS ARE EXPECTED DURING THE EXTENDED PERIOD,
ONE ON SUNDAY AFTERNOON INTO MONDAY MORNING AND A SECOND ONE ON
TUESDAY NIGHT INTO WEDNESDAY NIGHT.

THE INITIAL EVENT LOOKS TO BE ONE WITH SNOW OR MIXED WINTRY
PRECIPITATION. THE SECOND EVENT ON TUESDAY NIGHT INTO WEDNESDAY
NIGHT LOOKS TO BE ON THE LIQUID SIDE WITH TEMPERATURES WELL ABOVE
FREEZING AFTER AN INITIAL WINTRY START. ALTHOUGH THIS SECOND
EVENT IS ABOUT 5 DAYS OUT, WE WANTED TO HIGHLIGHT THAT SOME OF THE
SOLUTIONS WE`RE SEEING ARE PRODUCING LOCALLY HEAVY RAINFALL.

THE COMBINATION OF A BRIEF WARM UP ON WEDNESDAY, LOCALLY HEAVY
RAIN, MELTING SNOW, A FROZEN GROUND, ABOVE NORMAL ICE IN CREEKS,
STREAMS, AND RIVERS COULD LEAD TO INCREASED RUNOFF AND FLOODING.

INCREASED FLOW 0N AREA CREEKS, STREAMS, AND RIVERS COULD ALSO
START TO MOVE ICE, AND IN A WORST CASE SCENARIO, CREATE
RESTRICTIONS OR JAMS.

AGAIN, THIS SECOND EVENT BRINGING WARMTH AND RAIN IS ABOUT 5 DAYS
OUT. THINGS CAN CHANGE. CONTINUE TO MONITOR FORECASTS. KEEP IN MIND
THAT SNOWMELT AND WARMTH, BY THEMSELVES, TYPICALLY DON`T CAUSE
FLOODING. HOW MUCH RAIN WE GET WILL BE THE DETERMINING FACTOR.

&&

.CLIMATE...
MIN TEMP RECORDS FOR FRI/27TH AND SAT/28TH. NO RECORDS WERE SET
TODAY ALTHOUGH KACY WAS CLOSE...3 DEGREES OFF THIS MORNING. THERE
IS A GREATER CHANCE OF RECORDS ON SATURDAY.

POR / SITE  /  FEB 27          /  FEB 28

1872 / KPHL /  6 1900  NO RER  /  9 1934 RECORD IN JEOPARDY
1874 / KACY /  7 1934* NO RER  /  2 1934
1894 / KILG /  5 1934  NO RER  / -5 1934
1922 / KABE / -2 1963  NO RER  /-10 1934
1869 / KRDG /  4 1934* NO RER  /  3 1934 RECORD IN JEOPARDY
1865 / KTTN /  6 1934  NO RER  /  1 1934
1948 / KGED / 10 1963  NO RER  /  8 1950
1901 / KMPO / -9 1993  NO RER  /-15 1907

KACY RER FOR 3/1 IS 5 IN 1980 AND KTTN 8 IN 1972.

NOTE: * INDICATE AND OTHER YEARS.
NOTE: POR = PERIOD OF RECORD, THE YEAR OFFICIAL CLIMATE OBS BEGAN.

THE FOLLOWING IS A TABLE OF THE ***PROJECTED*** TOP 5 COLDEST
FEBRUARY`S ON RECORD, BASED ON THE CURRENT FORECAST, AND THUS
SUBJECT TO CHANGE. EACH RANKING DENOTES THE MEAN FEBRUARY
TEMPERATURE (F) AND YEAR OF OCCURRENCE.

WE REREVIEWED THESE PROJECTIONS LISTED BELOW USING THIS FRIDAY
AFTERNOONS (27TH) MINS AND THE PHI FCST AS SEEN ON NDFD AND
SFT`S. WE SEE PHL/ABE/ILG ALL VERY CLOSE TO PRIOR PROJECTIONS.

POR  / SITE  / 1ST RANK / 2ND RANK / 3RD RANK / 4TH RANK / 5TH RANK

1872 / KPHL / 22.2(1934) 23.0(1979) 24.3(1885) 24.6(1978) 25.4(1895)
1874 / KACY / 21.6(1979) 23.6(1934) 23.8(1978) 24.9(2015) 25.5(1875)
1894 / KILG / 20.2(1934) 22.1(1979) 22.7(1978) 24.7(2015) 24.9(1936)
1922 / KABE / 16.6(1934) 19.0(2015) 20.4(1979) 21.6(1936) 22.0(1963)

PER THE ABOVE TABLE, ABE IS EASILY ON TRACK FOR THE SECOND COLDEST
FEBRUARY, BOTH ACY AND ILG 4TH COLDEST, AND PHL THE SIXTH COLDEST
PROJECTED AT 25.5F (NOT SHOWN IN THE TABLE ABOVE).

THE FOLLOWING IS A TABLE OF THE ***PROJECTED*** MEAN FEBRUARY 2015
TEMPERATURES (F) AND DEPARTURES FROM NORMAL. THIS IS ALSO BASED ON
THE CURRENT FORECAST, AND THUS SUBJECT TO CHANGE. JANUARY 2015 MEAN
TEMPERATURES ARE ALSO INCLUDED FOR COMPARISON PURPOSES.

POR  / SITE / FEB MEAN(F) / FEB NORMAL(F) / FEB DEP (F) / JAN MEAN(F)

1872 / KPHL / 25.5        / 35.7          / -10.2       / 30.9
1874 / KACY / 24.9        / 35.3          / -10.4       / 30.2
1894 / KILG / 24.7        / 35.1          / -10.4       / 30.3
1922 / KABE / 19.0        / 30.7          / -11.7       / 25.9

IN GENERAL, MEAN TEMPERATURES AT OUR FOUR MAJOR CLIMATE SITES ARE ON
TRACK TO BE AROUND 10 TO 12 DEGREES BELOW NORMAL FOR FEBRUARY 2015.

IT`S ALSO INTERESTING TO NOTE THAT THE PROJECTED FEBRUARY 2015 MEAN
TEMPERATURES WILL BE WELL BELOW THE JANUARY 2015 MEAN TEMPERATURES.
TO PUT THIS IN PERSPECTIVE, NORMAL MEAN FEBRUARY TEMPERATURES AT OUR
FOUR MAJOR CLIMATE SITES ARE ON AVERAGE ABOUT 2 TO 3 DEGREES WARMER
THAN JANUARY. THE CONVERSE IS SHAPING UP TO BE THE CASE FOR FEBRUARY
2015, AS MEAN TEMPS WILL BE 2 TO 3 DEGREES BELOW THOSE OBSERVED IN
JANUARY.

THE FOLLOWING IS FOR ANY METEOROLOGICAL WINTER MONTH, NOT JUST
JANUARY OR FEBRUARY.

ALSO OF INTEREST, THIS WOULD ALSO BE THE SECOND OR THIRD COLDEST
MONTHLY MEAN TEMPERATURE ON RECORD AT ALLENTOWN SINCE RECORDS
BEGAN IN 1922, WITH FEBRUARY 1934 BEING THE COLDEST! OUR OTHER
SITES RANK AS FOLLOWS:

PHILADELPHIA PROJECTS AROUND 12TH COLDEST MONTHLY MEAN SINCE RECORDS
BEGAN IN 1873.

ATLANTIC CITY AROUND 7TH COLDEST MONTHLY MEAN SINCE RECORDS BEGAN
IN 1874.

WILMINGTON HAS MISSING DATA IN ITS DATABASE (1897-1916), AND SO WE
DON`T FOCUS AS MUCH ATTENTION ON THAT RECORD.

&&

.EQUIPMENT...
KGED SUNSHINE MAXIMUM TEMPS LOOK FAR TOO WARM. A TROUBLE TICKET
IS POSTED ON THIS TEMPERATURE SENSOR.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 10 PM EST THIS
     EVENING FOR ANZ450>455.

&&

$$
SYNOPSIS...DRAG
NEAR TERM...GAINES/GIGI
SHORT TERM...GAINES
LONG TERM...DRAG
AVIATION...DRAG/GAINES
MARINE...DRAG/GAINES/GIGI
HYDROLOGY...KRUZDLO
CLIMATE...DRAG/FRANCK
EQUIPMENT...


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