Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS61 KPHI 192035
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
335 PM EST WED NOV 19 2014

.SYNOPSIS...
HIGH PRESSURE SLIDES OFFSHORE TONIGHT AND IS FOLLOWED BY A COLD
FRONTAL PASSAGE ON THURSDAY. BEHIND THIS FRONT, A STRONGER HIGH
PRESSURE SYSTEM WILL MOVE IN FROM THE WEST ON FRIDAY, AND CREST
OVER THE REGION ON SATURDAY BEFORE MOVING OFFSHORE ON SUNDAY.
MEANWHILE, LOW PRESSURE WILL DEVELOP ACROSS THE INTER-MOUNTAIN
WEST, AND TRACK NORTHEASTWARD TO LAKE MICHIGAN. THIS LOW WILL
BRING A COLD FRONT THROUGH THE REGION EARLY NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
THE MAIN FEATURE WORKING THROUGH OUR REGION IN THIS PERIOD
WILL BE A WARM FRONT COMING IN FROM THE SOUTHWEST, THE ASSOCIATED
LOW PRESSURE SYSTEM WILL PASS WELL TO OUR NORTHWEST. THIS WARM FRONT
WILL RESULT IN THE INCREASE OF MID AND HIGH LEVEL CLOUDS. WE
CURRENTLY HAVE A VERY DRY AIRMASS IN PLACE, MARKED WITH DEWPOINTS AT
OR UNDER 15 DEGREES. THIS WILL TEND TO LIMIT ANY PRECIPITATION. THE
ONE EXCEPTION WOULD WITH THE AID OF TERRAIN IN THE POCONOS AND NW NJ
LEADING TO SOME PATCHY FLURRIES. THE RGEM AND NAM ARE MOST
AGGRESSIVE WITH THIS CHANCE. STILL OUTSIDE THE RANGE OF THE HRRR AND
RAP MODELS ATTM. BOTH THE GFS AND ECMWF AGREE ON TEMPERATURES
FALLING A LITTLE DUE TO RADIATIONAL COOLING DURING THE EVENING THEN
RISING WITH THE WARM FRONTAL PASSAGE AROUND MIDNIGHT AND THEN
FALLING SOMEWHAT TOWARD SUNRISE. TOOK THIS TREND INTO ACCOUNT BUT
STAYED CLOSE TO THE MAV AND MET GOING A TOUCH COOLER IN SPOTS
FAVORABLE FOR RADIATIONAL COOLING.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/...
SOUTHERLY FLOW WILL GIVE WAY ONCE AGAIN TO WESTERLY BEHIND
THE COLD FRONT. STILL VERY DRY NO PRECIPITATION EXPECTED FROM THIS
WITH THE EXCEPTION OF A FLURRY FOR THE POCONOS AND MORNING CLOUDS. THE
MAIN CHALLENGE WILL BE THE FRONTAL TIMING AND TEMPERATURES. THE
ECMWF IS SLOWER AND WARMER GIVING PHL A GOOD SHOT TO GET WELL INTO
THE 40`S. HOWEVER THE GFS IS FASTER WITH PHL BARELY HITTING 40.
FRONTAL PASSAGE NW OF PHL SHOULD OCCUR IN THE MORNING, LIMITING THE
MODEL SPREAD FOR TEMPERATURES IN THIS REGION. A SLOWER FRONTAL
PASSAGE ALLOWS FOR COASTAL AREAS TO SEE MORE SOUTHERLY FLOW AND MAKE
A RUN AT 50. WENT A COUPLE OF DEGREES BELOW MAV/MET NORTHWEST GIVEN
NW FLOW AND WENT ABOVE MAV/MET ALONG THE COAST DUE TO THE
SOUTHERLY FLOW.

&&

.LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/...

HIGHLIGHTS...

* TEMPERATURES WELL BELOW NORMAL FRIDAY W/SNOW SHOWERS POSSIBLE IN
  THE POCONOS
* CHANCE OF RAIN LATE SUNDAY INTO EARLY NEXT WEEK W/TEMPERATURES
  ABOVE NORMAL
* TEMPERATURES PROJECTED TO RETURN TO SEASONABLE LEVELS MID-WEEK

DETAILS...

A PATTERN CHANGE IS UNDERWAY AS THE PERSISTENT BLOCKING PATTERN
ALONG THE WEST COAST OF NOAM /POSITIVE HEIGHT ANOMALIES/ BREAKS
DOWN...ALLOWING A VIGOROUS S/WV TO MOVE INTO THE FOUR CORNERS
REGION ON SATURDAY...LEADING TO STRONG DOWNSTREAM HEIGHT RISES
ACROSS THE E CONUS, W/THE MID-LEVEL TROUGH GRADUALLY LIFTING TO
THE NORTHEAST ON FRIDAY AND RIDGING TAKING ITS PLACE BY MONDAY.
THIS WILL LEAD TO A WARMING TREND...WITH MAXIMUM TEMPERATURES
WELL BELOW NORMAL ON FRIDAY MODERATING TO ABOVE NORMAL LEVELS
BY MONDAY.

THE GFS...ECMWF AND THEIR RESPECTIVE ENSEMBLES ARE IN GENERAL
AGREEMENT ON TAKING THE SOUTHERN STREAM S/WV INTO THE FOUR-
CORNERS REGION ON SATURDAY...BUT DIFFER ON THE STRENGTH OF THE
NORTHERN STREAM S/WV COMING ASHORE IN THE PACIFIC NORTHWEST
AT THAT TIME. THIS HAS IMPLICATIONS FOR THE DEGREE OF DOWNSTREAM
PHASING OVER THE UPPER MS VALLEY ON SUNDAY AND THE EVOLUTION
OF THE RESULTANT STORM SYSTEM. THE MODELS AGREE ON A STORM TRACK
OVER THE MICHIGAN PENINSULA...BUT THE WEAKER NORTHERN STREAM
SHORTWAVE HAS LEAD TO A FASTER SOLUTION BY 24-HOURS...W/THE LOW
NOW PROGGED OVER THE MICHIGAN PENINSULA AT 12Z MONDAY. BUT AT
D+5 IT/S TOUGH TO SPECULATE IF THIS TRACK AND TIMING WILL HOLD.

NEVERTHELESS...THE PATTERN FAVORS A STORM TRACK TO THE WEST OF
THE APPALACHIANS AS WELL AS WARMER AIR MOVING INTO THE E CONUS...
BUT UNCERTAINTY IN THE TRACK AND STRENGTH OF THIS STORM SYSTEM
TRANSLATES INTO UNCERTAINTY IN THE TEMPERATURE FORECAST SUNDAY AND
BEYOND. LOOKING AHEAD TO TUESDAY AND WEDNESDAY...A FRONTAL PASSAGE
DURING THIS TIME FRAME LOOKS TO DELIVER A REINFORCING SHOT OF COLD
AIR...WHILE CYCLOGENSIS MAY TAKE PLACE INVOF THE EAST COAST, WHICH
BEARS WATCHING AS THE NAO IS PROJECTED TO GO NEGATIVE.

&&

.AVIATION /21Z WEDNESDAY THROUGH MONDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.

CLEAR SKIES THIS AFTERNOON AND EVENING WILL GIVE WAY TO SCATTERED
AND BROKEN MID TO HIGH LEVEL CLOUDS WITH THE PASSAGE OF A WARM
FRONT TONIGHT. THIS WILL ALSO RESULT IN A WIND SHIFT TO THE
SOUTHWEST. AFTER SOME GUSTS AROUND 15 KNOTS THIS AFTERNOON, WINDS
SHOULD SUBSIDE TO AROUND 10 KNOTS TONIGHT. VFR.

ON THURSDAY, WITH THE PASSAGE OF A COLD FRONT THE WINDS WILL
GRADUALLY SHIFT BACK TO THE WEST BY AFTERNOON WITH INCREASING
GUSTS REACHING 25 KNOTS. MID TO HIGH LEVEL CLOUDS WILL CLEAR OUT
BY DAYS END. VFR.

OUTLOOK...

FRIDAY...VFR. NORTHWEST WINDS MAY GUST TO 25 KNOTS DURING THE
LATE MORNING THRU EARLY AFTERNOON HOURS.

SATURDAY...VFR.

SUNDAY AND MONDAY...MVFR POSSIBLE IN LOW CEILINGS AND -SHRA
ESPECIALLY LATE SUNDAY AND PARTICULARLY ON MONDAY.

&&

.MARINE...
SEAS AND WINDS SHOULD INCREASE THIS EVENING. THE ENVIRONMENT WILL
BE FAVORABLE FOR SOME SOUTHWEST GALE FORCE WIND GUSTS AROUND 35
KNOTS ON THE OCEAN WATERS FROM 04-12Z THURSDAY. A GALE WARNING IS
IN EFFECT. THE GALE GUSTS MAY NOT BE SUSTAINED THROUGH THIS WHOLE
PERIOD BUT MAY BE MORE OF A INTERMITTENT VARIETY. SCA CONDITIONS
LIKELY WILL CONTINUE THROUGHOUT THE DAY THURSDAY WITH
NORTHWESTERLY WINDS.

OUTLOOK...

FRIDAY...SCA WINDS AND SEAS LIKELY THURSDAY NIGHT AND FRIDAY...
SLOWLY SUBSIDING TO SUB-SCA CONDITIONS FRIDAY NIGHT.

SATURDAY AND SUNDAY...SUB-SCA CONDITIONS ARE ANTICIPATED ATTM.

MONDAY...A GALE WARNING MAY BE NEEDED.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...GALE WARNING FROM 11 PM THIS EVENING TO 7 AM EST THURSDAY FOR
     ANZ450>455.
     SMALL CRAFT ADVISORY FROM 7 PM THIS EVENING TO 7 AM EST
     THURSDAY FOR ANZ430-431.

&&

$$
SYNOPSIS...FRANCK
NEAR TERM...GAINES
SHORT TERM...GAINES
LONG TERM...FRANCK
AVIATION...FRANCK/GAINES
MARINE...FRANCK/GAINES





USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.