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000
FXUS61 KPHI 252218
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
618 PM EDT FRI JUL 25 2014

.SYNOPSIS...
SURFACE HIGH PRESSURE OVERHEAD WILL MOVE OFFSHORE ON SATURDAY
SETTING UP A RETURN FLOW. A WARM FRONT CROSSES THE REGION LATE ON
SATURDAY WHILE THE PARENT LOW PRESSURE SYSTEM MOVES THROUGH THE
GREAT LAKES. THE ATTENDANT COLD FRONT SWINGS THROUGH LATE ON
SUNDAY INTO MONDAY FOLLOWED BY ANOTHER HIGH PRESSURE SYSTEM.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
THE WRF-NMMB INITIALIZATION DID LOOK BETTER THAN THE GFS AT
500MB, ESPECIALLY UPSTREAM. AT 850MB AND 925MB IT WAS A MIXED BAG
BETWEEN THE MODELS, BUT NEARLY ALL ERRORS THAT THERE WERE, WERE
1C. NO BIG CHANGES IN THE MODELS DP/DT FROM YESTERDAY. THE BEST OF
THIS AIR MASS IS NOW BEHIND US.

TONIGHT IS A FLIP OF LAST NIGHT AS THE EVENING SHOULD BE THE
CLEARER HALF BEFORE HIGH CLOUDS FROM THE FORMER AND ONGOING MCS IN
THE MIDWEST WORK THEIR WAY INTO OUR CWA OVERNIGHT. THE WRF-NMMB
ESPECIALLY AND THE GFS SOMEWHAT ALSO TAKE SOME OF THE LOWER LEVEL
MOISTURE IN SOUTHWEST VIRGINIA AND ADVECT IT INTO OUR CWA LATE
TONIGHT. DONT SEE MUCH OMEGA AT THAT LEVEL, SO EMPHASIS REMAINS
MORE WITH THE HIGH CLOUDS. THAT BEING SAID, WE HAD TEMPS DROP
OVERNIGHT IN THE MORE TRADITIONAL TYPICAL FASHION. DEW POINT
ERRORS TODAY HAVE BEEN TOO LOW AND THEY ARE RISING TO THE LEE OF
THE SEA BREEZE FRONT. SO WE DID NOT BUY INTO THE LOWER RADIATIONAL
COOLING MINS ON STAT GUIDANCE FOR THIS REASON.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/...
CONFIDENCE IS NOT HIGH IN EITHER DIRECTION ABOUT CONVECTION AND
THE END RESULT FOR NOW IS A RATHER GENERIC VANILLA SUMMER`S DAY
FORECAST FOR SATURDAY.

THE MODELS HAVE BEEN PRETTY CONSISTENT IN POOLING DEW POINTS AS
SATURDAY PROGRESSES IN OUR CWA. PARTLY BECAUSE OF THE
AFOREMENTIONED SHORT WAVES AND ALSO LOOKS TO BE SOME SFC WIND
CONVERGENCE. THEY ACTUAL SPIKE UPWARD HAS BECOME MORE LOGICAL FROM
YESTERDAY WHERE SOME OF THE MODEL FCST SFC DEW POINTS WERE
REACHING THE MID 70S. STILL MOS GUIDANCE IS FORECASTING DEW POINTS
5 TO 10F LOWER THAN THEIR OWN MODEL GUIDANCE. THIS PLUS TEETERING
CLOSE TO THE EDGE OF THE AVAILABLE CAPE FOR THUNDER AND WHETHER OR
NOT THE CAP WOULD HOLD. GIVEN THE SHORT WAVES ALOFT, THINKING THE
CAP WONT. THIS LEAVES THE DEW POINTS. IF THEY DONT GET INTO THE
MID 60S ALONG THE COASTAL PLAIN, CHANCES ARE THERE WONT BE ENOUGH
CAPE. NORTH AND WEST THERE IS ALWAYS THE OROGRAPHIC INFLUENCE THAT
MAY COMPENSATE FOR LOWER DEW POINTS. MODIFIED SOUNDING CONVECTIVE
TEMPS ARE PREDICTED TO BE REACHED, SO WE DID EXPAND THE MENTION OF
DURING THE AFTERNOON THUNDER GEOGRAPHICALLY. CONVERSELY SINCE MOST
MESOSCALE MODELS ARE CONVERGING SOUTH AND EAST TOWARD THE HIGHER
DEW POINT POOLING, WE DID LOWER POPS IN THE NORTHWEST PART OF OUR
CWA.

PREDICTED 1395 1000-850MB THICKNESSES ARE NOT BUYING MAX TEMPS AS
HIGH AS THEY HAVE DONE IN PAST SUMMERS. FULL SUN MACROS LOOK
OVERCOOKED AND MAX TEMPS WERE KEPT CLOSER TO 10-11C OVER PREDICTED
925MB TEMPS. THIS IS CLOSE TO STAT GUIDANCE AND CONTINUITY. GFS
THERMAL GUIDANCE WENT DOWN ABOUT 1-2C FROM THURSDAY`S LEVELS AOB
850MB.

&&

.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
SUNDAY...A DECAYING MCS SHOULD BE DIVING WELL TO THE SOUTHWEST OF
OUR REGION AS ONE MID-LEVEL SHORTWAVE CRUISES THROUGH. SURFACE
WARM FRONT SHOULD BE LIFTING THROUGH DURING THE EARLY PART OF THE
MORNING. MOISTURE WILL CONTINUE TO INCREASE WITH A SOUTHWEST
SURFACE FLOW WITH PWATS EXCEEDING 1.5 INCHES. EARLY MORNING
SHOWERS AND THUNDERSTORMS SHOULD BE WANING BY LATE MORNING AS MOST
OF THE OPERATIONAL GUIDANCE SHOWS THE REGION BREAKING OUT. NOT
QUITE SURE HOW LONG LIVED THE BREAK WILL BE AS CONVECTIVE
TEMPERATURES SHOULD EASILY BE MET AS HIGHS APPROACH 90F SO WE
CONTINUE WITH CHANCE POPS. BETTER FORCING MOVES IN ALOFT WITH A
MUCH STRONGER SHORTWAVE AND APPROACHING COLD FRONT LATER ON
SUNDAY. BETTER HEIGHT FALLS, SHEAR PROFILES AND LESS CAPPING
SHOULD ALLOW FOR MUCH MORE ORGANIZED CONVECTION TO OCCUR. SPC HAS
US IN DAY 3 OUTLOOK AT THIS TIME SO WILL CONTINUE WITH THE HWO
HIGHLIGHTING.

MONDAY...COLD FRONT WILL CONTINUE TO MOVE THROUGH THE REGION,
THOUGH NOT AT A BLISTERING PACE. WEAK SURFACE CYCLOGENESIS IS
POSSIBLE ON MONDAY AS THE FRONT SITS JUST TO OUR EAST SO WE KEEP
CHANCE POPS IN PLACE DURING THE DAY. TEMPERATURES SHOULD END UP
BEING AROUND AVERAGE ACROSS THE EAST AND SLIGHTLY BELOW ACROSS THE
WEST.

TUESDAY - THURSDAY...DRYING TREND SHOULD COMMENCES ACROSS A
MAJORITY OF THE REGION, BUT WITH THE MID-LEVEL TROUGH/COLD POOL
ALOFT, AND THE SLIGHTEST HINT OF INSTABILITY AROUND, ISOLATED
SHOWERS ARE POSSIBLE ON TUESDAY...BETTER FURTHER NORTH. THE
CHANCES FOR SHOWERS DECREASES EACH AFTERNOON THEREAFTER.
TEMPERATURES SHOULD END UP BEING BELOW NORMAL FOR LATE JULY
STANDARDS.

&&

.AVIATION /22Z FRIDAY THROUGH WEDNESDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.

TAFS CONTINUED VFR FORECAST.

SEA AND BAY BREEZE FRONTS HAVE FORMED. THE SEA BREEZE FRONT HAS
MADE DECENT PROGRESS AND IT EXTENDS ALONG THE NEW JERSEY TURNPIKE
FROM CENTRAL NEW JERSEY DOWN TO ABOUT KVAY AROUND 600 PM. IT THEN
BENDS SOUTHWARD TOWARD KMIV. THE FRONT SHOULD CONTINUE TO MOVE
NORTHWEST WITH A WEAKENED VERSION PREDICTED TO GET TO THE KPHL
AREA AIRPORTS AROUND 00Z. WIND SPEEDS EVEN BEHIND THE FRONT
SHOULD BE 10 KNOTS OR LESS. PRECEDING THE FRONT AND AT OTHER
TERMINALS LIGHT WEST TO SOUTHWEST WINDS WILL PREVAIL.

FOR TONIGHT WINDS WILL BECOME LIGHT AND VARIABLE, SOUTHWEST IF
THERE IS A DIRECTION. THE CIRRUS IN THE TAFS IS MORE FOR THE
SECOND HALF OF THE NIGHT. NO FOG IS EXPECTED TO FORM.

ON SATURDAY. VFR CIG EXPECTED. MOST OF THE REMAINING TAF TIME IT
SHOULD BE AT THE ALTOCU LEVEL. SOUTHWEST WINDS WILL BE INCREASING
AS THE MORNING PROGRESS. WINDS IN THE LAST FORECAST GROUP
REPRESENT MORE OF THE LATTER HALF OF THE MORNING/EARLY AFTERNOON
EXPECTATIONS.

ISOLATED SHOWERS AND THUNDERSTORMS SHOULD OCCUR, BUT COVERAGE FOR
NOW APPEARS TOO SMALL AND LIKELY AFTER 18Z TO INCLUDE IN ANY
TERMINALS. CONFIDENCE TOO LOW FOR KPHL INCLUSION.

OUTLOOK...
SUNDAY - MONDAY...SUB-VFR CONDITIONS EXPECTED IN AREAS OF SHOWERS
AND THUNDERSTORMS.

TUESDAY - WEDNESDAY...VFR.

&&

.MARINE...
SEA AND BAY BREEZE FLOW SHOULD DOMINATE THE NEARSHORE AND
DELAWARE BAY WATERS INTO THIS EVENING BEFORE WINDS BECOMING
LIGHTER OVERNIGHT.

THE HIGH PRESSURE SYSTEM WILL BE MOVING OFFSHORE AND A SLIGHTLY
STRONGER SYNOPTIC SCALE RETURN FLOW IS PREDICTED FOR SATURDAY. AS
IS TYPICALLY THE CASE, MODEL GUIDANCE OVER THE WATERS IS NORMALLY
OVERDONE IN CASES LIKE THIS AND WINDS AND SEAS WERE KEPT BELOW SCA
CRITERIA THRU THE DAY ON SATURDAY.

OUTLOOK...
SUNDAY...SUB-SCA EXPECTED WITH SCATTERED SHOWERS AND
THUNDERSTORMS.

MONDAY...SEAS MAY BUILD TO SCA LEVELS UNDER A STRENGTHENING
SOUTHWEST SURFACE FLOW.

TUESDAY - WEDNESDAY...SUB-SCA CONDITIONS EXPECTED.

&&

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

&&

$$

SYNOPSIS...HEAVENER
NEAR TERM...GIGI
SHORT TERM...GIGI
LONG TERM...HEAVENER
AVIATION...GIGI/HEAVENER
MARINE...GIGI/HEAVENER