NWS Philadelphia/Mount Holly wrote its last area forecast discussion before the first event at Aug 1, 2:56 AM EST, 6 hours 4 minutes earlier.
Area forecast discussion, Aug 1, 2:56 AM EST, 6 hours 4 minutes before
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
356 AM EDT FRI AUG 1 2008
.SYNOPSIS...
A WEAK COLD FRONT WILL CONTINUE TO EASE ACROSS THE REGION EARLY
THIS MORNING BEFORE POSSIBLY DISSIPATING NEARBY. A WEAK AREA OF
HIGH PRESSURE WILL THEN BE NEAR THE REGION THIS AFTERNOON. A MUCH
STRONGER COLD FRONT IS THEN FORECAST TO CROSS OUR AREA ON
SATURDAY. HIGH PRESSURE AT THE SURFACE WILL THEN SLIDE OVER THE
REGION SUNDAY INTO MONDAY. A WARM FRONT MAY THEN MOVE THROUGH ON
TUESDAY, WITH A COLD FRONT GRADUALLY SETTLING THROUGH THE MID
ATLANTIC REGION WEDNESDAY AND THURSDAY.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
A SURFACE ANALYSIS EARLY THIS MORNING PLACED A WEAKENING COLD FRONT
FROM NEAR COASTAL SOUTHERN NEW ENGLAND SOUTHWESTWARD ACROSS
NORTH-CENTRAL NEW JERSEY AND THEN WESTWARD ACROSS PENNSYLVANIA.
AN UPPER AIR ANALYSIS SHOWED A TROUGH FROM THE MIDWEST TO THE
NORTHEAST WITH SHORT WAVE ENERGY EMBEDDED WITHIN THE NORTHWESTERLY
FLOW. MEANWHILE, A LARGE UPPER RIDGE REMAINS PARKED OVER THE
SOUTHWESTERN UNITED STATES.
SATELLITE IMAGERY SHOWS LITTLE IN THE WAY CLOUDS AROUND WITH THE
EXCEPTION OF SOME STRATOCUMULUS AND A FEW POCKETS OF MIDLEVEL
CLOUDS. THESE HAVE BEEN MAINLY TIED TO RATHER ISOLATED SHOWERS
THAT POPPED UP MUCH EARLIER IN THE LEHIGH VALLEY AS THE LOW-LEVEL
BOUNDARY SLOWLY SETTLES SOUTHEASTWARD. DEW POINTS HAVE LOWERED
SOME ACROSS THE FAR NORTHWESTERN ZONES AS SOME DRYING MAKES A
SOUTHWARD PUSH. THE WEAKENING CLOUD MASS OVER OHIO AND WESTERN NEW
YORK IS WHAT IS LEFT OF AN MCS, AND THE UPPER AIR ANALYSIS PLACED
A VORTICITY CENTER IN OHIO ASSOCIATED WITH THAT. THERE DOES NOT
APPEAR TO BE A DEFINED MCV ASSOCIATED WITH THAT HOWEVER. SOME
LIGHT HAZE AND FOG ARE BEING REPORTED EARLY THIS MORNING, HOWEVER
SOME DRYING IS WORKING ITS WAY INTO THE NORTHWEST ZONES. WE
DECIDED TO NOT CARRY A FOG MENTION EARLY THIS MORNING AS
VISIBILITIES AT THE MAJORITY OF THE REPORTING SITES ARE WELL ABOVE
2 MILES.
OVERALL TODAY IS EXPECTED TO BE TRANQUIL AS WE ARE IN BETWEEN
SYSTEMS SO TO SPEAK WITH THE AFOREMENTIONED WEAK FRONT EASING TO OUR
SOUTH AND EAST OR DISSIPATING AND THE UPPER TROUGH BEGINNING TO
AMPLIFY ACROSS THE GREAT LAKES. AS THIS AMPLIFICATION TAKES PLACE,
AN UPPER-LEVEL JET IS FORECAST TO STRENGTHEN ACROSS THE GREAT
LAKES WITH OUR NORTHERN AREAS ON THE SOUTHERN EDGE. THIS WILL
PROBABLY TOSS SOME HIGH-LEVEL CLOUDS ACROSS THE CWA. WE ARE NOT
ANTICIPATING AS MUCH CLOUDS TODAY AS WE SAW YESTERDAY. WHILE AN
ISOLATED SHOWER OR STORM CANNOT BE RULED OUT, COVERAGE WOULD
LIKELY BE SO SMALL THAT IT WILL NOT BE INCLUDED. THE LOCALLY RUN
WRF TRIES TO POP AN ISOLATED STORM ON A SEABREEZE THIS AFTERNOON.
WATER VAPOR IMAGERY SHOWING PLENTY OF DRY MIDLEVEL AIR, AND
FORECAST SOUNDINGS INDICATE GOOD VERTICAL MIXING OCCURRING TODAY
WITH AN OFFSHORE FLOW COMBINED WITH DAYTIME HEATING. THIS SHOULD
RESULT IN THE LOWERING OF THE SURFACE DEW POINTS SOME THROUGH THE
DAY AND WE LEANED TOWARD THE LOWER GFS MOS VALUES.
AS FOR HIGH TEMPERATURES, WE DECIDED TO LEAN CLOSER TOWARD THE
ETA MOS FOR MOST LOCALES AS THE GFS MOS SEEMED A BIT TO WARM AND
HAS BEEN SO IN THE PAST. WE DO NOTE THE FLOW IS OFFSHORE SO SOME
DOWNSLOPING MAY BE ABLE TO ADDED A FEW DEGREES. FOR NOW, WE WENT
WITH 90 TO 92 DEGREES ALONG THE INTERSTATE 95 CORRIDOR AND THE
COASTAL PLAIN. GIVEN THE WESTERLY FLOW JUST ABOVE THE SURFACE
TODAY, THIS SHOULD PROVIDE MORE OF A RESISTANCE TO ANY SEABREEZE
CIRCULATIONS.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY NIGHT/...
OUR ATTENTION QUICKLY TURNS TO THE NORTHWEST AS A FAIRLY
SIGNIFICANT SHORT WAVE IS FORECAST TO DIVE SOUTHEASTWARD IN THE
AMPLIFYING CYCLONIC FLOW. CONVECTION IS EXPECTED TO DEVELOP ACROSS
THE CENTRAL AND WESTERN GREAT LAKES IN RESPONSE TO INCREASING
SYNOPTIC SCALE FORCING. WE MAY EVENTUALLY SEE THE CONVECTIVE CLOUD
DEBRIS ARRIVE INTO OUR AREA LATE TONIGHT. THE MAIN FOCUS WILL THEN
BE ON THE POTENTIAL FOR AN MCS TYPE FEATURE /TIED TO THE SHORT
WAVE/ TO MOVE INTO THE UPPER OHIO VALLEY LATE TONIGHT AND THEN
INTO THE MID ATLANTIC SATURDAY.
THE GFS APPEARS TO BE OVERDOING THE SURFACE WAVE AS IT MAY BE
CONVECTIVELY INDUCED LEADING TO FEEDBACK, AND IS ALSO A BIT FASTER
THAN THE MAJORITY OF THE MODEL SUITE. AS A RESULT, WE WENT WITH A
SLOWER TIMING WITH THE FRONT. ON SATURDAY, STEEPENING MIDLEVEL
LAPSE RATES COUPLED WITH A STRENGTHENING MIDLEVEL WIND FIELD /AROUND
30 KNOTS OF DEEP LAYER SHEAR/ AND SBCAPE TO ABOUT 1500 J/KG SHOULD
LEAD TO AT LEAST SCATTERED SHOWERS AND THUNDERSTORMS. THIS
DEVELOPMENT SHOULD ALSO BE AIDED WITH LOW-LEVEL CONVERGENCE
ASSOCIATED WITH THE SURFACE FRONT MOVING THROUGH. THE PRECIPITATION
COVERAGE MAY WIND UP BEING MORE, BUT FOR NOW WE WENT WITH HIGH CHC
POPS FOR THE CENTRAL AND NORTHERN AREAS TO A 40 POP DOWN SOUTH.
WAA AT 850 MB IS NOT FORECAST TO BE ALL THAT PRONOUNCED AHEAD OF
THE SHORT WAVE, THEREFORE A WARM FRONTAL TYPE FEATURE NEARING FROM
THE SOUTHWEST MAY NOT BE THAT ACTIVE, INSTEAD CONVECTION WOULD BE
MORE TIED TO THE SHORT WAVE AND ASSOCIATED INCREASING WIND
FIELD/SYNOPTIC LIFT. MOISTURE IS ALSO FORECAST TO INCREASE AS
PRECIPITABLE WATER VALUES NEAR 2.0 INCHES ON SATURDAY, AND THIS
MAY HELP IN PRODUCING A GOOD AMOUNT OF CLOUDINESS. IF THIS WERE TO
OCCUR, THE SURFACE-BASED INSTABILITY WOULD BE HELD DOWN SOME,
HOWEVER AT THIS POINT ELEVATED INSTABILITY LOOKS DECENT. GIVEN THE
STRONG UPPER TROUGH FOR THIS TIME OF YEAR, AND OTHER PARAMETERS
COMING INTO PLAY, SPC HAS PLACED A SLIGHT RISK OF SEVERE
THUNDERSTORMS GENERALLY FROM THE DELAWARE RIVER EASTWARD. STRONG
TO PERHAPS SEVERE THUNDERSTORMS WILL BE POSSIBLE, AND THE EASTERN
ZONES MAY HAVE A BACKED LOW-LEVEL FLOW AS THE SHORT WAVE AND
SURFACE FRONT MOVE ACROSS THE AREA. WE WILL ADD IN A MENTION OF
STRONG TO POSSIBLY SEVERE STORMS INTO THE HAZARDOUS WEATHER
OUTLOOK.
SINCE WE LEANED MORE TOWARD A SLOWER FRONTAL PASSAGE, WE HELD ONTO
SOME LOW CHC POPS SATURDAY EVENING AS THE FRONT WILL BE GRADUALLY
CLEARING THE CWA. AS SOMEWHAT DRIER AIR ARRIVES SATURDAY NIGHT,
AT LEAST SOME CLEARING IS ANTICIPATED. HOWEVER, WITH THE UPPER
TROUGH AXIS SITTING OVERHEAD AND A POTENTIAL SHORT WAVE SCOOTING
NEAR OUR NORTHERN ZONES, SOME CLOUDINESS MAY PERSIST ESPECIALLY UP
NORTH.
AS FOR TEMPERATURES, WE GENERALLY UTILIZED A BLEND OF CONTINUITY AND
GRIDDED MOS. IF CLOUDS ARE MUCH MORE WIDESPREAD ON SATURDAY, CURRENTLY
ADVERTISED MAXIMUM TEMPERATURES MAY BE A BIT HIGH.
&&
.LONG TERM /SUNDAY THROUGH THURSDAY/...
THIS TIME FRAME IS EXPECTED TO START WITH A RATHER AMPLIFIED
UPPER-LEVEL TROUGH FOR THIS TIME OF THE YEAR. THE MODEL GUIDANCE
INCLUDING THE GFS ENSEMBLES CONTINUE TO SETTLE INTO THIS HIGHLY
AMPLIFIED PATTERN WHICH DEEPEN THE UPPER-LEVEL TROUGH ACROSS THE
NORTHEASTERN UNITED STATES. THIS AMPLIFICATION ACTUALLY TAKES PLACE
AT THE END OF THE SHORT TERM AS STRONG SHORT WAVE ENERGY DIVES
SOUTHEASTWARD THEN EASTWARD. AS WE GO THROUGH TIME THOUGH, THE
TROUGH SHOULD TEND TO LIFT NORTHEASTWARD AS ENERGY MOVING ACROSS THE
HIGH PLAINS SHOULD SHOVE THE RIDGE EASTWARD. THIS IS WHEN LOWER
CONFIDENCE ARRIVES AS THE DEGREE OF THIS RIDGE IS MORE UNCERTAIN.
EVEN THE GFS ENSEMBLES NEARLY ALL POINT TO SOME RIDGING SLIDING
INTO THE MID ATLANTIC, HOWEVER THEY DIFFER IN THERE AMPLITUDE.
REGARDLESS, THIS EVOLVING SETUP STILL APPEARS TO ADVERTISE THE MCS
POTENTIAL. SOME OF THE MODEL GUIDANCE SUGGEST THIS POTENTIAL
SOMETIME DURING THE NEW WEEK, HOWEVER IF THE UPPER RIDGE REMAINS
PROGRESSIVE ENOUGH, MCS DEVELOPMENT MAY NOT BE ABLE TO MAKE THE TURN
PAST THE RIDGE AXIS. AS OF NOW, THE MODELS ARE AT ODDS REGARDING
THE 500 MB JET AS SOME 50 KNOTS MAINLY STAYS ACROSS THE MIDWEST
AND THE GREAT LAKES. THE GFS IS A BIT MORE ROBUST IN SLIDING THIS
WIND FIELD FURTHER EAST TO THE LOWER GREAT LAKES LATE TUESDAY. WE
NEED TO MONITOR THIS THOUGH GIVEN THE NORTHWESTERLY FLOW ALOFT
THROUGH WEDNESDAY, ESPECIALLY IF WE MANAGE TO GET STRONGER WAA TO
OUR WEST WHICH THEN IMPINGES INTO OUR AREA. THE UPPER FLOW THEN
LOOKS TO BACK MORE TO THE WEST AS THE UPPER RIDGE GETS KNOCKED
DOWN.
THE UPPER-LEVEL TROUGHING ON SUNDAY WILL HAVE COLD AIR ALOFT /ABOUT
-12C OR 10F/ AT 500 MB. THIS MAY PROMOTE PLENTY OF CUMULUS
DEVELOPMENT AS DAYTIME HEATING TAKES PLACE AND IN CONCERT WITH
CYCLONIC FLOW. FOR NOW WE WILL PLAY THE SKY COVER CONSERVATIVE. AT
THE SURFACE, HIGH PRESSURE WILL BE APPROACHING FROM THE WEST ON
SUNDAY, THEN SLIDE OVER THE REGION ON MONDAY. THIS SHOULD THEN
MOVE TO THE EAST QUICKLY MONDAY NIGHT AS A WARM FRONT BECOMES
BETTER DEFINED IN THE OHIO VALLEY. THIS WARM FRONT MAY MAKE A RUN
AT OUR AREA TUESDAY, THEN A COLD FRONT PROBABLY GRADUALLY SETTLES
INTO OUR AREA WEDNESDAY AND THURSDAY. WITH AT LEAST SOME UPPER-
LEVEL RIDGE SPREADING EASTWARD, A HOTTER AIRMASS SHOULD BE ABLE TO
SPILL INTO THE MID ATLANTIC. SOME OF THE MODELS HAVE BEEN
ADVERTISING INCREASING HEAT NEXT WEEK HOWEVER EVEN THAT HAS BEEN
OF LOWER CONFIDENCE. THE ECMWF STILL REMAINS LESS AMPLIFIED WITH
THE MIDLEVEL RIDGE EARLY NEXT WEEK, KEEPING THE TRUE HEAT WELL
SOUTH OF OUR AREA. ATTM, WE DECIDED TO NOT MAKE ANY SIGNIFICANT
CHANGES HOWEVER WE DID IMPLEMENT SOME NEW MOSGUIDE DATA AND MADE
SOME ADJUSTMENTS FOR COLLABORATIVE PURPOSES.
THAT IS ALL FOR NOW. THANKS TO THE SURROUNDING OFFICES FOR THE
COLLABORATION EARLY THIS MORNING. HAVE A GOOD ONE
&&
.AVIATION /08Z FRIDAY THROUGH TUESDAY/...
AT 0700Z, A FRONTAL BOUNDARY WAS DROPPING THROUGH OUR REGION, WITH
SOME MID LEVEL CLOUDS ASSOCIATED WITH IT. THE WIND WAS LIGHT AND
GENERALLY FROM THE WEST. CONDITIONS WERE VFR AT KPHL, KILG, KPNE,
KTTN, KABE AND KRDG. THERE WERE MVFR VISIBILITY RESTRICTIONS AT
KMIV AND KACY.
WITH SLIGHTLY DRIER AIR BUILDING INTO OUR REGION DURING THE EARLY
MORNING HOURS, WE ARE NOT EXPECTING VISIBILITY VALUES TO DROP A
GREAT DEAL. WE HAVE INDICATED THE POSSIBILITY OF EARLY MORNING MVFR
VISIBILITIES AT KRDG, KABE, KTTN AND KILG. WE HAVE ALSO FORECAST
MVFR VISIBILITY VALUES TO CONTINUE AT KMIV AND KACY, WITH KMIV
POSSIBLY DROPPING INTO THE IFR RANGE FOR A TIME. BOTH KPHL AND KPNE
SHOULD REMAIN IN THE VFR RANGE EARLY THIS MORNING.
THE MORNING SUNSHINE SHOULD MIX OUT ANY VISIBILITY RESTRICTIONS BY
1400Z. FROM THAT POINT ONWARD, WE ARE EXPECTING VFR CONDITIONS AT
ALL EIGHT OF OUR TAF SITES DURING THE DAYLIGHT HOURS WITH PERHAPS
SOME CUMULUS DEVELOPING FOR THIS AFTERNOON. THE WIND SHOULD
CONTINUE TO FAVOR A WESTERLY DIRECTION, WITH SPEEDS GETTING UP INTO
THE 8 TO 10 KNOT RANGE.
AFTER SUNSET, THE WIND WILL LIKELY BECOME LIGHT AND THE DIRECTION
SHOULD VARY AT MOST LOCATIONS. CONDITIONS ARE EXPECTED TO REMAIN
VFR AT LEAST THROUGH 0600Z ON SATURDAY.
OUTLOOK...
ANOTHER FRONTAL BOUNDARY FROM THE NORTHWEST IS FORECAST TO ARRIVE ON
SATURDAY. THERE IS A CHANCE FOR SHOWERS AND THUNDERSTORMS FROM LATE
TONIGHT INTO SATURDAY EVENING. NO RAIN IS EXPECTED FOR SUNDAY,
MONDAY OR TUESDAY AS HIGH PRESSURE BUILDS DOWN FROM THE NORTHWEST.
&&
.MARINE...
A FRONTAL BOUNDARY FROM THE NORTHWEST DROPPED INTO OUR REGION DURING
THE NIGHT. WEAK HIGH PRESSURE SHOULD INFLUENCE THE COASTAL WATERS
OF NEW JERSEY AND DELAWARE FROM THIS MORNING INTO EARLY TONIGHT.
ANOTHER FRONT FROM THE NORTHWEST IS FORECAST TO ARRIVE ON SATURDAY
WITH A MORE SUBSTANTIAL AREA OF HIGH PRESSURE EXPECTED TO FOLLOW IN
ITS WAKE FOR SUNDAY AND FOR THE EARLY PART OF THE NEW WEEK.
CONDITIONS WILL REMAIN BELOW SMALL CRAFT ADVISORY CRITERIA THROUGH
AT LEAST TUESDAY.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...NONE.
&&
SYNOPSIS...GORSE
NEAR TERM...GORSE
SHORT TERM...GORSE
LONG TERM...GORSE
AVIATION...IOVINO
MARINE...IOVINO