National Weather Service National Headquarters

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KPHI 160136
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
936 PM EDT SAT JUN 15 2013

.SYNOPSIS...
-- Changed Discussion --
HIGH PRESSURE WILL BECOME SITUATED TO OUR SOUTH LATE TONIGHT AND
SUNDAY. AN AREA OF LOW PRESSURE IS THEN FORECAST TO TRACK ACROSS
THE GREAT LAKES REGION AND SOUTHEASTERN CANADA SUNDAY AND MONDAY.
THE ASSOCIATED COLD FRONT IS SCHEDULED TO MOVE THROUGH MONDAY
NIGHT AND TUESDAY MORNING. HIGH PRESSURE THEN SETTLES INTO OUR
AREA WEDNESDAY AND THURSDAY, BEFORE SHIFTING TO OUR EAST FRIDAY
INTO SATURDAY.
-- End Changed Discussion --

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
-- Changed Discussion --
WEATHER CONTINUES QUIET THIS EVENING UNDER A FAIR WEATHER RIDGE.
STRATOCU AND WIND GUSTS HAVE DISSIPATED WITH THE LOSS OF DAYTIME
HEATING. SOME SCATTERED HIGH CLOUDINESS HAS BEEN MOVING THROUGH
THE REGION. WE ARE WATCHING THE ADVANCEMENT OF A SHORTWAVE TROUGH
THROUGH THE UPPER GREAT LAKES REGION WHILE WEAK WARM AIR ADVECTION
TAKES PLACE TO OUR WEST. THIS SHOULD BEGIN TO INCREASE THE MID-
LEVEL MOISTURE AND BRING IN MORE CLOUDS FROM THE WEST.

WE EXPECT THE OVERNIGHT HOURS TO BE DRY THOUGH SURFACE DEWPOINTS
WILL BE CLIMBING UNDER THE LIGHT SOUTHWEST FLOW. THE CLOUD COVER
WILL PLAY MORE OF A FACTOR WITH OVERNIGHT LOWS. CURRENT FORECAST
IS ON TRACK AND THOUGH MINOR CHANGES WERE MADE TO THE EVENING
TEMPERATURES AND DEWPOINTS, OVERNIGHT LOW TEMPERATURES WERE LEFT
AS IS.
-- End Changed Discussion --

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH 6 PM SUNDAY/...
ZONAL FLOW ALOFT, AS MID-LEVEL RIDGING SLIDES FURTHER TO OUR SOUTH,
WILL ALLOW EMBEDDED SHORTWAVES TO TRAVERSE THE REGION TOMORROW. THE
MAJORITY OF THIS ENERGY, NOW ACROSS THE UPPER MID-WEST, STILL HAS A
QUITE A LONG WAY TO TRAVEL AND THE FLOW ALOFT IS NOT QUITE AS FAST
AS IN DAYS PAST. MODELS ARE SHOWING THE TIMING OF THE STRONGER
SHORTWAVE PUSHING THROUGH TO OUR NORTH BY MID-AFTERNOON WHILE A
POSSIBLE LEE-SIDE TROUGH SETS UP TO OUR WEST AND TRIES TO PUSH
THROUGH. THIS COULD PROVIDE ENOUGH OF A SURFACE FOCUS, COMBINED WITH
THE PASSING SHORTWAVE ALOFT TO PRODUCE SCATTERED SHOWERS WITH
EMBEDDED THUNDER. GIVEN THE ZONAL FLOW ALOFT THE TIMING OF THE
SHORTWAVES IS HARD TO PINPOINT THOUGH WE DO HAVE A HIGHER CONFIDENCE
ACROSS OUR NORTHWEST ZONES OF SEEING SHOWERS BY MID-AFTERNOON.

THE CONVECTIVE PARAMETERS TOMORROW ARE NOT ALL THAT SPECIAL THOUGH
THE NAM IS MORE ROBUST WITH ITS LOW-LEVEL LAPSE RATES WHEN COMPARED
TO THE GFS. IT HAS A NICE STRIPE OF NEARLY DRY ADIABATIC 1000-850MB
LAPSE RATES ACROSS A MAJORITY OF OUR REGION WHEREAS THE GFS CONFINES
THE BETTER RATES TO OUR SOUTHWEST. SURFACE BASED CAPE LOOKS TO BE
CAPPED AROUND 300-400J/KG, WHICH IS STILL ENOUGH TO GET DECENT
CHARGE SEPARATION, ESPECIALLY WITH THE SHALLOW COLD POOL MOVING
THROUGH (TIED TO THE SHORTWAVE). THE SHEAR PROFILE IS BETTER FURTHER
NORTH AND WEST OF OUR REGION BUT GIVEN THE INFLUX OF HIGHER
DEWPOINTS, STORMS MAY BE ABLE TO ADVECT INTO THE REGION AND MAINTAIN
THEIR ORGANIZED STRUCTURES. OTHERWISE IT LOOKS LIKE RUN OF THE MILL
CONVECTION.

&&

.LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...
THE OVERALL SYNOPTIC SETUP IS COMPRISED OF AN UPPER-LEVEL TROUGH
ACROSS EASTERN CANADA THAT TENDS TO PERSIST THROUGH MUCH OF THIS
TIME FRAME. THERE IS SOME AMPLIFICATION FORECAST AT TIMES, ALTHOUGH
THIS WILL DEPEND ON THE SHORT WAVE STRENGTH ROUNDING THE TROUGH BASE
AND ALSO THE TIMING. THE UPPER-LEVEL FLOW MAY TURN MORE ZONAL FOR A
TIME LATE IN THE WEEK AS THE TROUGH ACROSS CANADA AMPLIFIES AND
SHIFTS WESTWARD. MEANWHILE, A RIDGE ELONGATES ACROSS THE SOUTHERN
STATES. AS OF NOW THERE APPEARS TO BE TWO FEATURES TO WATCH, THE
FIRST A COLD FRONT MOVING THROUGH LATE MONDAY INTO TUESDAY. THE
SECOND ONE IS ENERGY PUSHING INTO THE OHIO VALLEY LATE FRIDAY AND
SATURDAY, WITH PERHAPS SOME SORT OF WEAKNESS TRACKING NEAR THE NORTH
CAROLINA COAST. WE USED A MODEL BLEND APPROACH SUNDAY NIGHT INTO
TUESDAY, THEN WENT WITH WPC GUIDANCE FROM TUESDAY NIGHT ONWARD. SOME
ADJUSTMENTS WERE THEN MADE BASED ON ADDITIONAL COLLABORATION WITH
OUR NEIGHBORING OFFICES.

FOR SUNDAY NIGHT...LOW PRESSURE IS FORECAST TO TRACK TO OUR NORTH
WITH A TRAILING SURFACE TROUGH MOVING THROUGH DURING THIS TIME
FRAME. SOME SHOWERS AND THUNDERSTORMS SHOULD BE ONGOING, WITH
PERHAPS SOME ORGANIZATION INTO CLUSTERS OR MULTICELL. THESE SHOULD
BE ON A DIMINISHING TREND DURING THE NIGHT AS THE TROUGH OR WEAK
FRONT SHIFTS TO OUR EAST. IT APPEARS THAT OUR REGION IS ON THE
SOUTHERN EDGE OF THE STRONGER FLOW, WHICH TENDS TO REMOVE OUR REGION
FROM THE LARGE SCALE LIFT/STRONGER SHEAR. AS A RESULT, WE PLACED THE
HIGHEST POPS DURING THE EVENING HOURS. THERE HAS BEEN HINTS IN SOME
OF THE GUIDANCE THAT AN MCS FEATURE ORGANIZES TO OUR WEST-NORTHWEST
AND THEN MOVES THROUGH DURING SUNDAY NIGHT. THIS WOULD BE FAVORABLE
GIVEN THE NORTHWESTERLY FLOW ALOFT BUT ESPECIALLY IF A STRONG ENOUGH
SHORT WAVE CAN TEAM UP WITH THE RIGHT THERMODYNAMIC CONDITIONS. AS
OF NOW, WE ARE NOT HITTING THIS POTENTIAL ALL THAT HARD.

FOR MONDAY AND TUESDAY...AS AN UPPER-LEVEL TROUGH AMPLIFIES ACROSS
SOUTHEASTERN CANADA, LOW PRESSURE WILL CONTINUE TO TRACK EASTWARD
ACROSS NEW ENGLAND MONDAY INTO TUESDAY. SINCE THE STRONGER FLOW IS
FARTHER NORTH FOR AWHILE, THE ASSOCIATED COLD FRONT MAY BE SLOW TO
SETTLE ACROSS THE AREA INITIALLY. AS A RESULT, THE BOUNDARY IS NOT
FORECAST TO CLEAR OUR ENTIRE AREA UNTIL LATER TUESDAY. A WARM AND
MORE MOIST AIRMASS SHOULD BE IN PLACE AHEAD OF THIS FRONT TO PRODUCE
SOME SHOWERS AND THUNDERSTORMS, ALTHOUGH THE COVERAGE IS SOMEWHAT
UNCERTAIN ATTM. IT MAY END UP BEING MOSTLY DRY MONDAY, BUT SOME
CONVECTION CANNOT BE RULED OUT AT THIS POINT. A SHORT WAVE SLIDING
SOUTHEASTWARD ON THE SOUTHERN EDGE OF THE UPPER-LEVEL TROUGH MAY
ALLOW A SURFACE WAVE TO FORM ALONG THIS FRONT. THIS IS FORECAST TO
SLIDE ACROSS THE DELMARVA REGION DURING TUESDAY. THE AMOUNT OF
FORCING AND PRECIPITATION WITH THIS IS STILL IN QUESTION, AND VIA
CHATS WITH WPC INDICATES THE GFS /ESPECIALLY EARLIER RUNS/ IS TO FAR
NORTH WITH ITS PRECIPITATION ASSOCIATED WITH THIS FEATURE. WE
THEREFORE CONTINUE WITH SLIGHT CHC TO LOW CHC POPS MONDAY THEN
INCREASE THE CHC POPS SOME MONDAY NIGHT AND TUESDAY.

FOR WEDNESDAY AND THURSDAY...AN NARROW UPPER-LEVEL RIDGE IS FORECAST
TO MOVE EAST ACROSS THE PLAINS AND MIDWEST WEDNESDAY AHEAD OF A
LARGE TROUGH IN THE WEST. THIS ALLOWS SURFACE HIGH PRESSURE TO
SETTLE OVER OUR AREA DURING THIS TIME FRAME, AND PUSH A COLD FRONT
WELL TO OUR SOUTH AND EAST. A PERSISTENT UPPER-LEVEL TROUGH HOWEVER
IS FORECAST TO BE ACROSS EASTERN CANADA, THEREFORE THE SURFACE HIGH
WILL TEND TO SETTLE TO OUR SOUTHEAST DURING THURSDAY. A LIGHT
NORTHERLY WIND WEDNESDAY WILL GIVE WAY TO A SOUTHERLY FLOW
DEVELOPING THURSDAY. THIS FLOW IS FORECAST TO BE LIGHT, AND ENOUGH
OF A THERMAL CONTRAST SHOULD DEVELOP BETWEEN LAND AND WATER TO ALLOW
A SEA/BAY BREEZE TO DEVELOP ESPECIALLY THURSDAY. THIS WOULD KEEP THE
COASTAL AREAS COOLER, HOWEVER SOME MODERATION OF THE AIRMASS IS
FORECAST TO TAKE PLACE OVERALL ESPECIALLY THURSDAY. SINCE HIGH
PRESSURE IS THE DOMINANT FEATURE, A DRY FORECAST WAS CARRIED.

FOR FRIDAY AND SATURDAY...THE RIDGE IN THE MIDWEST AREA SHOULD
FLATTEN OUT OR PUSH SOUTHWARD AS ENERGY EJECTS OUT OF THE WEST. AS
A RESULT, LOW PRESSURE IS FORECAST TO TRACK ACROSS THE NORTHERN
PLAINS AND MIDWEST DURING THIS TIME FRAME. MEANWHILE, HIGH PRESSURE
IS SITUATED TO OUR EAST WITH A RETURN FLOW OCCURRING ACROSS THE
NORTHEAST. IT APPEARS THAT A WARM FRONT LIFTS NORTHWARD DURING
SATURDAY, ALTHOUGH THE MAIN WAA PUSH MAY END UP STAYING WELL TO OUR
WEST. THERE IS THE POTENTIAL THAT SOME SORT OF WEAKNESS OR COASTAL
TROUGH DEVELOPS NEAR THE CAROLINAS WITH CONVECTION OCCURRING. SOME
OF THIS MOISTURE MAY EVENTUALLY GET DRAWN NORTHWARD AS LOW-LEVEL WAA
AND MOISTURE ADVECTION INCREASES WELL IN ADVANCE OF THE NEXT SYSTEM.
IN ADDITION, A WEAK BOUNDARY MAY APPROACH OUR NORTHERN ZONES AS A
SYSTEM ZIPS BY WELL NORTH OF THE CANADIAN/U.S. BORDER. BASED ON THIS
AND MORE UNCERTAINTY WITH THE DETAILS, WE CARRIED SLIGHT CHC POPS IN
THE DATABASE ACROSS THE NORTHERN AND WESTERN ZONES FRIDAY THEN SOME
EXPANSION SOUTH AND EAST FRIDAY NIGHT AND SATURDAY.

&&

.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
-- Changed Discussion --
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.

OVERNIGHT...VFR WITH A LIGHT SOUTHWESTERLY WIND.

SUNDAY...VFR. INCREASING MID-LEVEL CLOUDS FROM THE WEST WITH AN
INCREASE IN LOW-LEVEL MOISTURE EXPECTED. A WEAK SURFACE TROUGH WILL NEAR
LATER IN THE AFTERNOON AND MAY TOUCH OFF A FEW SHOWERS WITH POSSIBLY
A THUNDERSTORM. THESE WERE NOT ADDED TO THE TAF GIVEN THE SPATIAL
COVERAGE UNCERTAINTY AND INITIATION TIMING. DEEPER MIXING, UNDER
SOUTHWESTERLY FLOW, SURFACE AND ALOFT, MAY YIELD SOME GUSTINESS IN
THE LOW 20 KNOTS RANGE.

OUTLOOK...
SUNDAY NIGHT AND MONDAY...MOSTLY VFR. A FEW SHOWERS AND
THUNDERSTORMS MAINLY SUNDAY EVENING, THEN PERHAPS AGAIN MONDAY
AFTERNOON AND NIGHT. THIS MAY RESULT IN TIMES OF LOCAL MVFR.
WEST-NORTHWEST WINDS AROUND 5 KNOTS SUNDAY NIGHT, THEN BECOMING
SOUTHWEST AROUND 10 KNOTS MONDAY.

TUESDAY...OVERALL VFR, HOWEVER MVFR OR LOWER AT TIMES WITH SOME
SHOWERS AND THUNDERSTORMS. SOUTHWEST WINDS 10-15 KNOTS, BECOMING
WEST, THEN NORTH LATE.

WEDNESDAY AND THURSDAY...VFR WITH NORTHERLY WINDS AROUND
5 KNOTS WEDNESDAY, BECOMING SOUTHERLY THURSDAY. A BAY/SEA BREEZE
COULD DEVELOP EACH AFTERNOON.
-- End Changed Discussion --

&&

.MARINE...
-- Changed Discussion --
NO CHANGES TO PREVIOUS FORECAST. SUB-SMALL CRAFT CONDITIONS ARE
EXPECTED ON OUR WATERS TONIGHT AND TOMORROW. THE SURFACE FLOW WILL
TURN MORE SOUTHWESTERLY LATER TONIGHT AS HIGH PRESSURE BEGINS TO
SETTLE TO OUR SOUTH AND EAST. NOT EXPECTING A GREAT SURGE IN SEAS
TOMORROW THOUGH THEY SHOULD TOP OUT AROUND 4 FEET ON THE OCEAN
FRONT. WINDS WILL BE ON THE INCREASE TO 15-20 KTS AND GIVEN WARMER
AIR FLOWING IN ALOFT, WE LOSE THE BETTER VERTICAL MIXING. THIS
WOULD ALLOW FOR MINIMAL GUSTINESS.

OUTLOOK...
A SURFACE TROUGH LOOKS TO PUSH THROUGH SUNDAY NIGHT, THEN THE MAIN
COLD FRONT IS FORECAST TO MOVE THROUGH LATE MONDAY NIGHT AND
TUESDAY. THE FLOW AHEAD OF THE FRONT MAY BE ENOUGH TO BUILD THE SEAS
TO 5 FEET ON THE OCEAN FOR A TIME SUNDAY NIGHT INTO MONDAY. THE FLOW
WILL SHIFT TO THE NORTH BEHIND THE FRONT LATER TUESDAY INTO
WEDNESDAY WITH SOME INCREASE, HOWEVER AS OF NOW THE WINDS LOOK TO
REMAIN BELOW ADVISORY CRITERIA. THE WINDS SHOULD THEN TURN SOUTHERLY
THURSDAY AS HIGH PRESSURE STARTS TO SHIFT TO OUR SOUTHEAST.
-- End Changed Discussion --

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...NONE.

&&

$$
SYNOPSIS...GORSE
NEAR TERM...SZATKOWSKI/HEAVENER
SHORT TERM...HEAVENER
LONG TERM...GORSE
AVIATION...GORSE/SZATKOWSKI/HEAVENER
MARINE...GORSE/SZATKOWSKI/HEAVENER