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 041725
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1225 PM EST THU FEB 4 2016

.SYNOPSIS...
A COLD FRONT WILL PUSH EAST OF THE MID-ATLANTIC EARLY TODAY BUT
REMAIN NEARBY OFFSHORE INTO TONIGHT. AN AREA OF LOW PRESSURE IS THEN
FORECAST TO DEVELOP ALONG THE OFFSHORE FRONT LATE TONIGHT AND MOVE
OUT TO SEA FRIDAY. HIGH PRESSURE WILL GRADUALLY BUILD INTO OUR AREA
FROM THE SOUTHWEST LATE FRIDAY AND SATURDAY. A WEAK COLD FRONT FROM
THE NORTHWEST MAY CROSS THE AREA EARLY SUNDAY, FOLLOWED BY A LOW
PRESSURE SYSTEM POSSIBLY AFFECTING THE REGION EARLY NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...

THIS AFTERNOON A COLD FRONTAL BOUNDARY IS LOCATED JUST OFFSHORE.
AS A RESULT, CLOUDS WILL CONTINUE TO LINGER THROUGH THE REMAINDER
OF THE DAY ACROSS THE REGION. SHORT RANGE MESOSCALE MODELS
CONTINUE TO SHOW SOME ISOLATED SHOWERS IN COASTAL SECTIONS, SO
WILL KEEP THE LOW CHANCE IN THE FORECAST THROUGH THE AFTERNOON.
TEMPERATURES AND DEWPOINTS WERE LOWERED A FEW DEGREES THIS
AFTERNOON AS WELL BASED ON CURRENT OBSERVATIONS.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM FRIDAY/...
SHORTWAVE ENERGY ASSOCIATED WITH THE UPPER TROUGH WILL PROGRESS
TOWARD THE EASTERN SEABOARD TONIGHT. THE MODELS CONTINUE TO SHOW
SECONDARY CYCLOGENESIS ALONG THE SOUTHEAST COAST BY EARLY THIS
EVENING. THE SURFACE LOW IS EXPECTED TO DEEPEN AS IT MOVES TO THE NE
ALONG THE STALLED FRONTAL BOUNDARY OFFSHORE. THE TRACK OF THE LOW
IS FORECAST TO BE FAR ENOUGH OFF THE COAST TO SPARE OUR AREA FROM
THE GREATEST IMPACTS (I.E., HEAVY PRECIP AND STRONG WINDS) BUT WE
WON`T BE COMPLETELY MISSED.

THE MODEL GUIDANCE HAS COME INTO GOOD GENERAL AGREEMENT WITH
RESPECT TO THE EVOLUTION OF THERMAL PROFILES, THE TIMING OF PRECIP
AND THE PLACEMENT OF THE PRECIP SHIELD. WE CAN SAY WITH REASONABLE
CONFIDENCE THAT PRECIP SHOULD EXPAND NEWD INTO THE DELMARVA AND
COASTAL NJ THIS EVENING. THE WESTERN EDGE OF THE PRECIP SHIELD
WILL LIKELY SET UP SOMEWHERE NEAR OR JUST WEST OF THE I-95
CORRIDOR OVERNIGHT. THE THERMAL PROFILES WILL INITIALLY BE WARM
ENOUGH FOR IT TO START OUT AS RAIN EVERYWHERE IN THE EVENING.
HOWEVER, HIGH PRESSURE BUILDS IN FROM THE WEST AND NW WINDS WILL
ADVECT COLDER AIR INTO THE AREA OVERNIGHT. THUS, WE EXPECT THE
RAIN TO MIX WITH AND EVENTUALLY CHANGE OVER TO SNOW FROM WEST TO
EAST OVERNIGHT.

HOWEVER, THERE IS STILL UNCERTAINTY IN SOME OF THE FINER DETAILS
WHICH WILL ULTIMATELY DECIDE HOW MUCH OF THE PRECIP WILL FALL AS
RAIN VS SNOW AND HOW MUCH OF THE SNOW WILL BE ABLE TO ACCUMULATE
WITH MARGINAL BOUNDARY LAYER TEMPERATURES. MOST OF THE UNCERTAINTY
RESIDES IN THE 06Z-12Z FRIDAY TIME FRAME AND IS TIED TO THE WILD
CARD OF DYNAMICAL COOLING. THE 00Z GUIDANCE HAS TRENDED A LITTLE
BIT HIGHER WITH THE QPF FOR THE 06-12Z PERIOD WITH AROUND 0.5 INCH
FORECAST ALONG THE COAST. ALSO, THE 03Z SREF MEAN AND 06Z NAM HAS
TRENDED WETTER AND SNOWIER. WE TRENDED SLIGHTLY HIGHER WITH OUR
FORECAST SNOWFALL AMOUNTS OF 1-2 INCHES (LOCALLY 2-3 INCHES) IN
THE COASTAL PLAIN. HOWEVER, THERE IS STILL A REASONABLE WORST-
CASE SCENARIO (I.E., OUR MAX SNOWFALL PROBABILISTIC GRAPHIC) THAT
SOME LOCATIONS GET DOUBLE THESE FORECAST AMOUNTS IF THE EFFECTS
FROM DYNAMICAL COOLING WINDS UP BEING EVEN GREATER AND PRECIP
TRANSITIONS TO SNOW MUCH MORE RAPIDLY THAN INDICATED BY THE 00Z
GUIDANCE. CONVERSELY, WE`VE SEEN MODELS SOMETIMES BEING TOO
BULLISH WITH SNOWFALL ACCUMULATIONS IN RAIN-CHANGING-TO-SNOW
EVENTS, ESPECIALLY WHEN THE BOUNDARY LAYER IS WARM AT THE ONSET.

THE UNCERTAINTY STILL SEEMS TOO HIGH TO ISSUE ANY WINTER WEATHER
ADVISORY THIS FAR OUT BUT ONE MAY NEED TO BE ISSUED LATER TODAY.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
AN OVERALL ACTIVE PATTERN LOOKS TO BE IN PLACE THROUGH THE LONG
TERM PERIOD, ESPECIALLY FROM THE LATTER HALF OF THE WEEKEND AND
INTO EARLY NEXT WEEK. FOR FRIDAY MORNING, AN AREA OF LOW PRESSURE
IS FORECAST TO BE OFF OF THE MID-ATLANTIC COAST, EAST OF VIRGINA,
ALONG AN OLD COLD FRONTAL BOUNDARY. WHILE THIS LOW PRESSURE IS
FORECAST TO TRACK NORTHEAST AND FARTHER OUT TO SEA THROUGH THE
COURSE OF THE DAY, THE PROXIMITY OF THIS SYSTEM TO THE NEW JERSEY
AND DELAWARE COASTS FRIDAY MORNING MAY ALLOW FOR SOME LINGERING
LIGHT SNOW ACROSS EASTERN NJ AND SOUTHEAST DE BEFORE THE SYSTEM
DEPARTS FARTHER EAST BY LATE MORNING TO MIDDAY. TOTAL ACCUMULATION
AMOUNTS FOR THESE AREAS FROM LATE THURSDAY NIGHT THROUGH EARLY
FRIDAY MAY REACH BETWEEN ONE TO TWO INCHES, BUT WITH SOME
UNCERTAINTY REGARDING TRACK AND QPF AMOUNTS, WE WILL HOLD OFF ON
ANY ADVISORY HEADLINES AT THIS TIME. OTHERWISE, THE REMAINDER OF
FRIDAY SHOULD BE DRY WITH GRADUAL CLEARING FROM WEST TO EAST
ACROSS THE REGION AS AN AREA OF HIGH PRESSURE TO OUR SOUTHWEST
BUILDS TOWARD THE MID-ATLANTIC. THIS HIGH PRESSURE IS EXPECTED TO
STICK AROUND THROUGH SATURDAY ACROSS THE AREA, YIELDING DRY AND
QUIET CONDITIONS WITH JUST SOME CLOUDS ADVANCING IN FROM THE
NORTHWEST AS THE DAY WEARS ON. DAYTIME MAXIMUM TEMPERATURES ARE
EXPECTED TO BE PRETTY SIMILAR BOTH FRIDAY AND SATURDAY, MAINLY IN
THE 40S ACROSS THE REGION, EXCEPT SOME TEMPS MAXING OUT IN THE 30S
OVER THE HIGHER TERRAIN IN THE POCONOS.

BY EARLY SUNDAY, A WEAK COLD FRONT MAY APPROACH OUR REGION FROM THE
NORTHWEST, BUT WITH LIMITED MOISTURE ASSOCIATED WITH THIS BOUNDARY,
WE HAVE KEPT A DRY FORECAST FOR SUNDAY, WITH DAYTIME HIGHS REACHING
MAINLY IN THE 40S. OF NOTE, THE GFS AND ECMWF CONTINUE TO DEVELOP AN
AREA OF LOW PRESSURE OF VARYING INTENSITY OFF THE SOUTHEASTERN
SEABOARD SUNDAY, TAKING IT OUT TO SEA LATER SUNDAY NIGHT. LITTLE OR
NO IMPACT IS STILL EXPECTED FOR OUR REGION, EXCEPT PERHAPS SOME
INCREASING CLOUDINESS, ESPECIALLY OVER THE SOUTHERN HALF OF OUR CWA.

THROUGH THE REMAINDER OF THE LONG TERM PERIOD, THERE CONTINUES TO BE
SIGNIFICANT MODEL DIFFERENCES WITH REGARDS TO A POSSIBLE LOW
PRESSURE SYSTEM PASSING ACROSS THE GREAT LAKES MONDAY AND ANOTHER
AREA OF LOW PRESSURE POSSIBLY DEVELOPING OFF THE EAST COAST TUESDAY.
WHILE THE TIMING OF PRECIPITATION ACROSS OUR REGION REMAINS A LOW
CONFIDENCE FORECAST AT THIS TIME, THE OVERALL PATTERN AND A BROAD
LONGWAVE TROUGH OVER THE GREAT LAKES TO NORTHEAST AND MID-ATLANTIC
SUGGESTS A COLDER TREND INTO EARLY/MID NEXT WEEK, AND WE GENERALLY
FOLLOWED SUPERBLEND AND/OR WPC GUIDANCE WITH REGARDS TO TEMPS AND
POPS AT THIS EXTENDED TIME RANGE.

&&

.AVIATION /17Z THURSDAY THROUGH MONDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.

A COLD FRONT HAD JUST MOVED THRU RDG AND ABE AS NOTED BY THE W-NW
WIND SHIFT. THE FRONT WILL PROGRESS THRU THE I-95 TERMINALS BEFORE
12Z AND ACY/MIV SHORTLY AFTER. LOW CLOUDS AND FOG ALONG AND AHEAD
OF THE FRONT HAS RESULTED IN LIFR RESTRICTIONS EARLY THIS MORNING
BUT THEY SHOULD IMPROVE IN WAKE OF FROPA FROM WEST TO EAST TOWARD
DAYBREAK. A BRIEF SHOWER POSSIBLE EARLY THIS MORNING WITH FROPA.
EXPECT VFR CONDITIONS FROM MID MORNING THRU THE AFTERNOON.

RAIN WILL MOVE BACK TOWARD ACY/MIV AFTER 23Z AND THEN TOWARD THE
PHILA TERMINALS AFTER 03Z. CURRENTLY NOT EXPECTING THE PRECIP TO
REACH ABE AND RDG. THE RAIN IS EXPECTED TO MIX WITH AND THEN
TRANSITION TO SNOW FROM WEST TO EAST OVERNIGHT INTO EARLY FRIDAY
MORNING. IFR OR EVEN RESTRICTIONS POSSIBLE ONCE IT CHANGES TO
SNOW. NW WINDS 5-10 KT IN THE EVENING WILL BECOME NLY AND INCREASE
TO 10-15 KT LATE.

OUTLOOK...
FRIDAY...MAINLY VFR, EXCEPT POSSIBLE SUB-VFR IN LIGHT SNOW IN THE
MORNING FOR EASTERN SITES, ESPECIALLY KACY/KMIV.

SATURDAY AND SUNDAY...MAINLY VFR CONDITIONS ARE EXPECTED.

MONDAY...MAINLY VFR, BUT CONDITIONS MAY LOWER AS THE DAY WEARS ON
DUE TO POSSIBLE LOW PRESSURE APPROACHING THE REGION. IN ADDITION TO
POSSIBLE LOWER CIGS DEVELOPING, LOWER VSBYS MAY ALSO OCCUR IN
RAIN/SNOW.

&&

.MARINE...
SCA REMAINS IN EFFECT FOR THE ATLANTIC COASTAL WATERS FOR TODAY
AND TONIGHT. FOR THE ZONES UNDER A SCA, THE WINDS ARE CURRENTLY
SW AND BELOW 25 KT BUT THE SEAS ARE STILL 5-7 FT. THE WINDS MAY
BRIEFLY GUST AOA 20 KT AS THEY TURN NWLY BEHIND A COLD FRONT
DURING THE EARLY AND MID MORNING.

NW WINDS BECOME NLY TONIGHT AND INCREASE AS LOW PRESSURE DEVELOPS
OF THE SOUTHERN MID-ATLANTIC COAST. GUSTS 25-30 KT ARE POSSIBLE IN
THE ATLANTIC COASTAL WATERS. THE SCA MAY NEED TO BE EXPANDED INTO
THE DE BAY FOR LATE THURSDAY NIGHT IF THE LOW STRENGTHENS FURTHER
THAN FORECAST OR TRENDS CLOSER TO THE COAST.

OUTLOOK...
FRIDAY...BREEZY NORTHWEST WINDS ARE EXPECTED, AND GUSTS BETWEEN
25 TO 30 KNOTS ARE EXPECTED FOR THE ATLANTIC COASTAL WATERS. WE
HAVE EXTENDED THE SCA THROUGH 6PM FRIDAY.

SATURDAY...SUB-ADVISORY CONDITIONS ARE EXPECTED.

SUNDAY AND MONDAY...WINDS AND SEAS LOOK TO REMAIN BELOW ADVISORY
CRITERIA FOR MUCH OF SUNDAY, BUT THERE IS SOME POTENTIAL FOR
OFFSHORE LOW PRESSURE TO PASS EAST OF OUR WATERS SUNDAY NIGHT INTO
MONDAY, WHICH COULD ENHANCE SEAS AND WIND GUSTS.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EST FRIDAY FOR ANZ450>455.

&&

$$
SYNOPSIS...KLINE
NEAR TERM...GAINES
SHORT TERM...KLEIN
LONG TERM...KLINE
AVIATION...KLEIN/KLINE
MARINE...KLEIN/KLINE


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