Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 250143
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
943 PM EDT FRI APR 24 2015

.SYNOPSIS...
HIGH PRESSURE EXTENDING OVER THE GREAT LAKES WILL BRIEFLY BUILD
ACROSS OUR REGION SATURDAY. A LOW PRESSURE SYSTEM WILL PASS BY TO
OUR SOUTH FROM SATURDAY NIGHT INTO SUNDAY, TRACKING FROM AROUND THE
TENNESSEE VALLEY TO OFF THE CAROLINA COAST. AN UPPER LEVEL
DISTURBANCE IS EXPECTED TO PASS OVER THE NORTHEAST STATES ON MONDAY,
FOLLOWED BY WEAK HIGH PRESSURE AFFECTING THE REGION ON TUESDAY. A
DEVELOPING LOW PRESSURE SYSTEM IS THEN FORECAST TO MOVE ACROSS THE
NORTHERN GULF OF MEXICO REGION WEDNESDAY BEFORE EMERGING OFF THE
SOUTHEASTERN SEABOARD THURSDAY.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
A CUTOFF LOW CONTINUING TO SPIN OVER NORTHERN NEW ENGLAND/SOUTHEAST
CANADA THIS EVENING HAS NOT MOVED MUCH IN THE PAST 24 HOURS. OUR
REGION CAN`T ESCAPE THE COLD OWING TO THE PERSISTENT NORTHWEST
FLOW AROUND THE LOW.

AN IMPRESSIVE 175 KT UPPER-LEVEL JET STREAK THAT WAS CAPTURED ON THE
00Z IAD RAOB WILL PROGRESS TOWARD THE MID-ATLANTIC COAST. ANTICIPATE
SOME JET-INDUCED HIGH CLOUDS TO SPREAD INTO THE AREA LATER TONIGHT.

WHILE THE GUSTY WINDS HAVE SUBSIDED AFTER SUNSET, THEY STILL
REMAIN IN THE 5-15 MPH RANGE EVERYWHERE. THESE WINDS HAVE KEPT
TEMPS UP THUS FAR. THE RIDGE AXIS ASSOCIATED WITH HIGH PRESSURE
OVER THE GREAT LAKES IS FORECAST TO BUILD DOWN INTO WESTERN PA AND
THE BLUE RIDGE MOUNTAINS OVERNIGHT. ALTHOUGH THE PRESSURE GRADIENT
WILL BE WEAKENING, THERE IS STILL UNCERTAINTY IF WE`LL BE ABLE TO
RADIATE 100 PERCENT EFFECTIVELY DUE TO A LIGHT NORTHWEST WIND THAT
WILL LIKELY PERSIST THROUGHOUT THE NIGHT. TWEAKED MIN TEMPS UPWARD,
ESPECIALLY OUTSIDE OF THE SHELTERED VALLEYS. IT WAS NOT ENOUGH TO
MAKE CHANGES TO THE FREEZE WARNINGS THAT WERE ISSUED PREVIOUSLY.
WE ARE ALSO NOT ENTIRELY SURE HOW MUCH FROST WILL DEVELOP BY
MORNING IF WE DO NOT DECOUPLE AND SINCE THE AIRMASS IS SO DRY
AIRMASS. REGARDLESS, IT`S STILL A GOOD IDEA TO TAKE PRECAUTIONS
NECESSARY TO PROTECT EARLY SEASON VEGETATION THAT IS SUSCEPTIBLE
TO THE COLD.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/...
STUCK IN BETWEEN TWO LOWS, THE ONE TO OUR NE WHICH WILL CONTINUE TO
FILL, AND THE LOW TO OUR SW, WHICH WILL REMAIN WELL TO OUR WEST
TOMORROW, WE WILL CONTINUE TO SEE A RATHER WEAK PRESSURE GRADIENT,
AND THUS RATHER LIGHT WINDS THROUGH THE DAY TOMORROW. DECREASED
HIGHS SLIGHTLY AS WE`RE ONLY RELYING ON WEAK DOWNSLOPE FLOW FOR ANY
WARMING TREND, SO TEMPERATURES SHOULD ONLY BE SLIGHTLY HIGHER THAN
TODAY.

&&

.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
A COUPLE OF LOW PRESSURE SYSTEMS ARE EXPECTED TO AFFECT THE REGION
DURING THE LONG TERM PERIOD, THE FIRST OF WHICH WILL LIKELY AFFECT
MAINLY OUR SOUTHERN CWA AS THIS SYSTEM SWINGS BY TO OUR SOUTH, BUT A
POTENTIALLY STRONGER, COASTAL SYSTEM MAY REACH THE AREA FOR THE
MIDDLE OF NEXT WEEK.

INTO SATURDAY NIGHT, AN AREA OF LOW PRESSURE WILL BE APPROACHING
FROM AROUND THE OHIO/TENNESSEE VALLEY REGION. AS THIS SURFACE LOW
PROGRESSES EASTWARD THROUGH THE NIGHT, A SECONDARY LOW IS FORECAST
TO DEVELOP EAST OFF THE NORTH CAROLINA COAST BY SUNDAY MORNING. THE
NORTHERN EDGE OF PRECIPITATION ASSOCIATED WITH THESE SYSTEMS IS
EXPECTED TO EXTEND MAINLY INTO OUR SOUTHERN CWA, ESPECIALLY ACROSS
OUR DELMARVA ZONES AND SOUTHERN NEW JERSEY, AND WE HAVE CHANCE TO
LIKELY POPS FROM NORTH TO SOUTH SATURDAY NIGHT FOR THESE AREAS. THE
LOW PRESSURE WILL THEN EXIT EAST AND OUT TO SEA THROUGH THE COURSE
OF SUNDAY, BUT THERE COULD BE SOME LEFTOVER PRECIP THAT LINGERS OVER
THE DELMARVA INTO SUNDAY MORNING, AND WE GRADUALLY DIMINISH POPS TO
CHANCE AND THEN LOWER THROUGH THIS PERIOD. ELSEWHERE THROUGH THE
FORECAST AREA, A DRY SUNDAY IS ANTICIPATED WITH SOME CLOUDS AND
GENERALLY LIGHT NORTHERLY WINDS.

MONDAY COULD PRESENT A FEW SHOWERS FOR OUR AREA AS AN UPPER
DISTURBANCE/UPPER LOW LINGERS AROUND THE NORTHEAST STATES OR JUST TO
THEIR EAST. MODEL FORECAST SOUNDINGS PREDICT CONVECTIVE TEMPERATURES
TO BE REACHED MONDAY, SO THERE WILL BE INCREASING CLOUDS THROUGH THE
DAY ALONG WITH SOME ISOLATED/SCATTERED SHOWERS EXPECTED AS COOLER
AIR ALOFT ASSOCIATED WITH THE UPPER LOW LINGERS NEARBY.

THE UPPER LOW PULLS AWAY OUT TO SEA INTO TUESDAY, AND WEAK HIGH
PRESSURE FROM THE WEST GRADUALLY BUILDS ACROSS OUR REGION, LASTING
THROUGH THE DAYTIME WEDNESDAY. WE HAVE KEPT A DRY FORECAST THROUGH
THIS PERIOD, WITH RATHER LIGHT NORTHERLY WINDS AND NEAR AVERAGE END
OF APRIL TEMPERATURES. THE TRICKY AND HIGHLY UNCERTAIN PART OF THE
FORECAST THEN INVOLVES THE DEVELOPMENT AND TRACK OF A POTENTIALLY
STRONG COASTAL SYSTEM THAT MAY BEGIN TO AFFECT OUR REGION WEDNESDAY
NIGHT AND LASTING THROUGH THURSDAY TO THURSDAY NIGHT. THERE
CONTINUES TO BE A WIDE RANGE OF SOLUTIONS FROM THE OPERATIONAL
MODELS TO VARIOUS ENSEMBLE DATA REGARDING THE TRACK, EVOLUTION, AND
INTENSIFICATION OF LOW PRESSURE, MOST LIKELY FROM AROUND THE
NORTHERN GULF OF MEXICO REGION WEDNESDAY BEFORE ITS POTENTIAL
EMERGENCE OFF THE EAST COAST THURSDAY. WITH THE GREATER UNCERTAINTY
THROUGH THIS PERIOD, WE LEANED MORE TOWARD WPC GUIDANCE FOR MOST
ELEMENTS, INCLUDING TEMPERATURES, WINDS, AND POPS, WITH ADDITIONAL
COLLABORATION WITH NEIGHBORING OFFICES.

&&

.AVIATION /01Z SATURDAY THROUGH WEDNESDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.

GUSTY NW WINDS HAVE DIMINISHED THIS EVENING. THEY WILL STILL BE
AROUND 10 KT OVER THE NEXT HOUR OR TWO AND THEN CLOSER TO 5 KT
OVERNIGHT. WINDS WILL INCREASE A BIT DURING THE DAY TOMORROW ,
WITH WIND GUSTS AROUND 15KT POSSIBLE IN THE AFTERNOON.

OUTLOOK...
SATURDAY NIGHT...PRIMARILY VFR CONDITIONS, EXCEPT SOME RAIN AND SUB-
VFR POSSIBLE MAINLY SOUTH OF A KILG/KACY LINE, INCLUDING THE
DELMARVA.

SUNDAY...MAINLY VFR CONDITIONS, AS ANY SUB-VFR IN RAIN TO START
ACROSS SOUTHERN AREAS WILL IMPROVE BACK TO VFR.

MONDAY...MAINLY VFR CONDITIONS; ALTHOUGH, SOME ISOLATED SHOWERS ARE
POSSIBLE. GUSTY NORTH TO NORTHWEST WINDS, WITH GUSTS TO 20 KNOTS.

TUESDAY AND WEDNESDAY...MAINLY VFR EXPECTED; ALTHOUGH, CONDITIONS
MAY DETERIORATE LATE WEDNESDAY NIGHT DEPENDING ON THE TIMING AND
TRACK OF A POSSIBLE COASTAL LOW PRESSURE.

&&

.MARINE...
WINDS HAVE GRADUALLY DIMINISHED OVER THE PAST COUPLE OF HOURS THIS
EVENING. SCA CONDITIONS NO LONGER BEING OBSERVED IN THE DELAWARE
BAY, WHERE THE SCA WAS ALLOWED TO EXPIRE EARLIER. ON THE OCEAN
WATERS, SCA CONDITIONS EXPECTED TO LINGER INTO THE EARLY MORNING
HOURS. SUB-SCA CONDITIONS ARE EXPECTED DURING THE DAY TOMORROW.

OUTLOOK...
SATURDAY NIGHT AND SUNDAY...SUB-ADVISORY CONDITIONS ARE EXPECTED AT
THIS TIME. AN AREA OF LOW PRESSURE IS FORECAST TO PASS BY TO OUR
SOUTH, BUT IT SHOULD NOT BE CLOSE ENOUGH TO RAISE WINDS OR SEAS TO
SCA LEVELS.

MONDAY...CONTINUED MAINLY SUB-SCA CONDITIONS; ALTHOUGH, SOME WIND
GUSTS TO AROUND 20 KNOTS PLUS ARE POSSIBLE.

TUESDAY AND WEDNESDAY...MOSTLY SUB-ADVISORY CONDITIONS THROUGH THIS
PERIOD; ALTHOUGH, SOME HIGHER WINDS AND SEAS MAY BEGIN TO OCCUR LATE
WEDNESDAY NIGHT DEPENDING ON THE TIMING AND TRACK OF POSSIBLE
COASTAL LOW PRESSURE. LOW CONFIDENCE.

&&

.FIRE WEATHER...
DRY CONDITIONS ARE EXPECTED ONCE AGAIN TOMORROW, WITH MINIMUM RH
VALUES ONCE AGAIN RANGING FROM 20 TO 30 PERCENT. HOWEVER, WINDS
WILL BE CONSIDERABLY LIGHTER TOMORROW, WITH WIND GUSTS GENERALLY
NEAR OR BELOW 15 MPH THROUGH THE DAY TOMORROW.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...FREEZE WARNING FROM 2 AM TO 8 AM EDT SATURDAY FOR PAZ060>062-
     101>106.
     FROST ADVISORY FROM 2 AM TO 8 AM EDT SATURDAY FOR PAZ070-071.
NJ...FREEZE WARNING FROM 2 AM TO 8 AM EDT SATURDAY FOR NJZ001-
     007>010-012-013-015>022-027.
     FROST ADVISORY FROM 2 AM TO 8 AM EDT SATURDAY FOR NJZ014-
     023>026.
DE...FROST ADVISORY FROM 2 AM TO 8 AM EDT SATURDAY FOR DEZ001>004.
MD...FREEZE WARNING FROM 2 AM TO 8 AM EDT SATURDAY FOR MDZ008.
     FROST ADVISORY FROM 2 AM TO 8 AM EDT SATURDAY FOR MDZ012-015-
     019-020.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT SATURDAY FOR ANZ450>455.

&&

$$
SYNOPSIS...KLINE
NEAR TERM...KLEIN
SHORT TERM...JOHNSON
LONG TERM...KLINE
AVIATION...KLEIN/KLINE
MARINE...KLEIN/JOHNSON/KLINE
FIRE WEATHER...JOHNSON



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