FXUS61 KPHI 031140
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
640 AM EST THU DEC 3 2009
.SYNOPSIS...
A LOW PRESSURE SYSTEM WILL QUICKLY LIFT NORTH OF OUR AREA DURING THE
MORNING AS AN ASSOCIATED COLD FRONT MOVES TO OUR EAST TODAY. HIGH
PRESSURE SETTLING INTO THE CENTRAL AND SOUTHERN PLAINS FRIDAY WILL
GRADUALLY BUILD EASTWARD INTO OUR AREA. AS ENERGY MOVES ACROSS THE
GULF OF MEXICO, ANOTHER LOW PRESSURE SYSTEM IS FORECAST TO DEVELOP
AND TRACK NORTHEASTWARD. THE TRACK OF THIS SYSTEM IS A LITTLE
UNCERTAIN, HOWEVER AT LEAST SOME PRECIPITATION LOOKS TO OVERSPREAD
THE AREA SATURDAY AND SATURDAY NIGHT. HIGH PRESSURE WILL THEN BUILD
IN SUNDAY AND GRADUALLY SLIDE EASTWARD THROUGH EARLY NEXT WEEK.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
A 07Z SURFACE ANALYSIS PLACED A 989 MB LOW OVER LAKE ERIE. AN
OCCLUDED FRONT STRETCHED FROM THIS LOW TO NORTHERN VIRGINIA, THEN A
WARM FRONT WAS UP INTO SOUTHERN NEW JERSEY. A COLD FRONT WAS DOWN
ACROSS SOUTHEASTERN VIRGINIA ON SOUTHWARD, WHILE A SECONDARY COLD
FRONT WAS ACROSS EASTERN OHIO SOUTHWARD TO NORTHERN ALABAMA. AN
UPPER AIR ANALYSIS PLACED A STRONG 300 MB JET FROM THE NORTHERN GULF
OF MEXICO ALL THE WAY INTO SOUTHEASTERN CANADA. A LARGE TROUGH WAS
CENTERED OVER THE MIDWEST, HOWEVER A STRONG SHORT WAVE WAS LOCATED
FROM OHIO TO WESTERN VIRGINIA. THE WATER VAPOR IMAGERY SHOWS THE
POTENT SHORT WAVE WELL DEFINED WITH A DRY SLOT WORKING INTO
SOUTH-CENTRAL PENNSYLVANIA AS OF 08Z. STRONG WAA IS FROM
NORTHEASTERN PENNSYLVANIA ON NORTHWARD.
A RATHER DYNAMIC SYSTEM AS A TREMENDOUS SURGE OF THETA-E ADVECTION,
WAA AND A POTENT WIND FIELD ALL TEAMED UP TO PROVIDE ENHANCED LIFT.
THE STRONG WAA HAS ALLOWED THE TEMPERATURES TO CLIMB THROUGH THE
NIGHT WITH MANY AREAS FROM ABOUT INTERSTATE 95 ON SOUTH AND EASTWARD
ARE IN THE 60S ATTM. THE DEW POINTS HAVE ALSO SURGED UP AND THE MOS
GUIDANCE HAS BEEN TO LOW, THEREFORE WE WENT CLOSER TO THE RUC
GUIDANCE EARLY THIS MORNING AND ALSO UTILIZED OBSERVATIONAL TRENDS.
THE LAMP GUIDANCE IS GRADUALLY CATCHING ON TO THE MUCH HIGHER DEW
POINTS. THE ADVECTION OF WARMER AND MORE MOIST AIR HAS ALLOWED FOR
MOSTLY SOME ELEVATED CAPE TO OVERSPREAD THE AREA AND THERE HAVE BEEN
ISOLATED THUNDERSTORMS. THE VAD WIND PROFILE OFF OF THE FORT DIX
DOPPLER RADAR INDICATES 55 KNOTS AT 2,000 FEET AS OF 08Z. THE
INTENSE LOW-LEVEL WIND FIELD IS FORECAST TO WEAKEN THROUGH THE
MORNING AS THE MAIN ENERGY/WAA SURGE GETS SHUNTED TO OUR EAST. THE
RAIN WILL TAPER TO SHOWERS FROM SOUTHWEST TO NORTHEAST EARLY ON AND
WE INCLUDED A SLIGHT CHC OF THUNDER EARLY GIVEN THE ISOLATED
POTENTIAL. THE ADVECTION OF WARMER AIR OVER COOLER WATER APPEARS TO
BE KEEPING THE STRONGER WINDS FROM REACHING THE SURFACE /I.E. LESS
VERTICAL MIXING/ ALONG THE IMMEDIATE COAST, THEREFORE WE WILL BE
CANCELING THE WIND ADVISORY. WE ARE NOTING SOME GUSTS AROUND 40
KNOTS AT 08Z THOUGH JUST TO OUR SOUTH AND THIS APPEARS TO BE ALONG
THE BACK EDGE OF THE INTENSE WIND FIELD AND SHOULD BE MORE ISOLATED
AND SHORT-LIVED. IT APPEARS WIDESPREAD GUSTS IN EXCESS OF 45 MPH IS
NO LONGER EXPECTED, THEREFORE WILL CARRY SOME 40 MPH GUSTS FOR A
TIME THIS MORNING. WE WILL MONITOR THE HEAVIER SHOWERS AND ANY
THUNDERSTORMS EARLY THIS MORNING AS THESE COULD TRANSPORT STRONGER
WINDS DOWN TO THE SURFACE FOR A BRIEF TIME.
THE MAIN COLD FRONT WILL CROSS THE ENTIRE AREA LATER THIS MORNING AND
THAT WILL SHIFT THE WINDS TO THE WEST AND NORTHWEST. SOME CAA
SETTLES IN DURING THE COURSE OF THE DAY, HOWEVER THIS IS NOT
FORECAST TO BE ALL THAT STRONG. THE FORECAST SOUNDINGS INDICATE THAT
ENOUGH VERTICAL MIXING WILL BE MAINTAINED THROUGH THE DAY TO KEEP
SOME GUSTINESS TO THE WINDS /BUT BELOW ADVISORY CRITERIA/.
AS FOR TEMPERATURES, A RATHER TRICKY ONE AS THEY HAVE SPIKED UP
QUITE A BIT ACROSS NEARLY THE ENTIRE CWA EARLY THIS MORNING. SOME
AREAS ARE WITHIN ABOUT 3-5 DEGREES OF THEIR RECORD HIGH FOR THIS
DATE ALREADY THIS MORNING. THERE WILL BE SOME INCREASE THIS MORNING
BEFORE SOME LEVELING OFF, HOWEVER THE CAA IS NOT FORECAST TO BE ALL
THAT STRONG AND WITH THE WIND GOING WESTERLY, SOME DOWNSLOPING WILL
OCCUR. THEREFORE, WE DID NOT INDICATE MUCH IN THE WAY OF FALLING
TEMPERATURES TODAY.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY/...
THE STRONG AREA OF LOW PRESSURE WILL BE QUICKLY MOVING THROUGH THE
CANADIAN MARITIMES TONIGHT. THE CYCLONIC LOW-LEVEL FLOW WILL
GRADUALLY WEAKEN AS THE PRESSURE GRADIENT RELAXES. THE UPPER-LEVEL
PATTERN THEN LOOKS TO RELOAD AS A SOUTHWEST FLOW ALOFT IS EXPECTED
TO CONTINUE TONIGHT THROUGH FRIDAY AS ENERGY DROPS SOUTHEASTWARD
ACROSS THE CENTRAL AND SOUTHERN PLAINS. THIS ENERGY WILL ENERGIZE A
BAROCLINIC ZONE FROM THE GULF OF MEXICO TO OFF THE SOUTHEASTERN
UNITED STATES COAST. MEANWHILE, THE CORE OF THE UPPER-LEVEL TROUGH
WILL BE NEAR HUDSON BAY AND TRYING TO SETTLE SOUTHWARD SOME.
DRIER AIR WILL CONTINUE TO SETTLE INTO OUR AREA TONIGHT WITH ANY
LINGERING CLOUDS ON THE DECREASE. GIVEN THE SOUTHWESTERLY FLOW ALOFT
HOWEVER, WE MAY KEEP SOME HIGH LEVEL CLOUDINESS. THE CENTER OF
HIGH PRESSURE IN THE CENTRAL/SOUTHERN PLAINS FRIDAY WILL BUILD
EASTWARD TO THE MID ATLANTIC. THIS SURFACE HIGH WILL THEN TEND TO
TRANSLATE NORTHEASTWARD AS THE UPPER-LEVEL TROUGH AMPLIFIES SOME
ACROSS THE OHIO AND TENNESSEE VALLEYS. THERE APPEARS TO BE PLENTY OF
MOISTURE CONVERGENCE NEAR THE GULF COAST STATES AS THE BAROCLINIC
ZONE BECOMES ACTIVE AND AS A SURFACE LOW DEVELOPS. THE TRAJECTORY OF
THE MID TO UPPER-LEVEL WINDS WILL TEND TO PULL AT LEAST HIGH LEVEL
MOISTURE OUR WAY DURING FRIDAY. AS A RESULT, WE WILL BEGIN TO SEE AN
INCREASE IN CLOUDS, ESPECIALLY LATER IN THE DAY AND AT NIGHT. THINGS
THEN BEGIN TO TURN MORE INTERESTING.
DURING THE PAST FEW DAYS, THE MODEL GUIDANCE HAS BEEN SHOWING SHORT
WAVE ENERGY DROPPING SOUTHEASTWARD AND ENERGIZING A BAROCLINIC ZONE
FROM NEAR THE GULF COAST AREA TO THE SOUTHEASTERN UNITED STATES
COAST. A SURFACE LOW IS FORECAST TO DEVELOP ALONG THIS BOUNDARY AND
THEN WAS SHUNTED NORTHEASTWARD AND WELL TO OUR EAST, PLACING OUR
AREA ON THE WESTERN FRINGE OF THE PRECIPITATION SHIELD. THE MODEL
GUIDANCE APPEARS TO BE SHOWING MORE SHARPENING OF THE UPPER-LEVEL
TROUGH FROM THE OHIO AND TENNESSEE VALLEYS. THIS TENDS TO PULL THE
SURFACE LOW TRACK A BIT FARTHER TO THE WEST, ALLOWING THE
PRECIPITATION SHIELD ALSO TO BE PULLED BACK WESTWARD. THE GFS,
NAM/WRF AND UKMET DO SHOW THIS MORE SHARPENING OCCURRING, ALTHOUGH
THE SURFACE LOW ATTM IS NOT FORECAST TO REALLY RAMP UP AS IT TRACKS
EAST OF OUR REGION. THIS WOULD LIMIT THE WAA FROM ARRIVING INTO OUR
AREA FROM THE EAST, AND THE FORECAST SOUNDING INDICATE A MORE
NORTHERLY WIND COMPONENT TO THE WIND. THE ECMWF ALSO APPEARS A BIT
SHARPER WITH THE UPPER-LEVEL TROUGH. INTERESTING TO NOTE THAT THE
WEDNESDAY GFS ENSEMBLES ARE MORE OFFSHORE ALTHOUGH THERE ARE SOME
MEMBERS THAT ARE A CLOSE CALL. THE FORECAST SOUNDINGS AND ALSO THE
MODEL PLAN VIEWS OF THE THERMAL FIELDS INDICATE THAT PERHAPS
BOUNDARY LAYER TEMPERATURES MAY NOT BE A PROBLEM IN MANY AREAS,
REGARDING FROZEN PRECIPITATION FALLING. THE TIMING OF THIS SYSTEM
ALSO HAS SLOWED SOME PROBABLY DUE TO THE FACT THAT THE TROUGH IS A
BIT SHARPER NOW. THIS WOULD PLACE THE BULK OF THE PRECIPITATION
OCCURRING LATER SATURDAY AND SATURDAY NIGHT. THE FORECAST SOUNDINGS
DO SHOW LITTLE EVAPORATIONAL COOLING TAKING PLACE INITIALLY, AND
PERHAPS THE LOW-LEVEL TEMPERATURES MAY BE A BIT COLD GIVEN CLOUDS ON
THE INCREASE FRIDAY NIGHT. IF THE CLOUDS HOLD OFF AND WE CAN GET
DECENT RADIATIONAL COOLING FOR AWHILE FRIDAY NIGHT, THEN THE CLOUDS
ROLL IN, THAT LOW-LEVEL COLDER AIR PERHAPS CAN GET TRAPPED. AN
EXAMINATION OF THE SURFACE THERMAL FIELDS OF THE GFS AND NAM/WRF, DO
INDICATE COLD ENOUGH TEMPERATURES TO SUPPORT SNOW ALTHOUGH STILL
THINK SOME RAIN WILL EITHER START OR MIX IN ESPECIALLY CLOSER TO THE
COAST. GIVEN THE TRACK OF THE STORM, WE WILL STAY CLOSE TO
CONTINUITY WITH MOSTLY SLIGHT CHC POPS ACROSS THE FAR NORTHWEST AND
CHC SOUTHEASTWARD. WE DID EDGE UP THE POPS SOME ACROSS THE EASTERN
AND SOUTHERN AREAS BUT KEPT THEM NO HIGHER THAN CHC ATTM. WE ALSO
CHANGED THE SNOW/RAIN SHOWER WORDING TO SNOW AND/OR RAIN GIVEN THE
FORECAST PRECIPITATION SHIELD. IF SNOW DOES OCCUR, ACCUMULATIONS
COULD BE TOUGHER AS SURFACE TEMPERATURES MAY BE AT OR ABOVE FREEZING
DURING THE DURATION AND INTENSITY COULD BE ON THE LIGHT SIDE.
ALTHOUGH THIS COULD CHANGE ESPECIALLY IF A SLOWER ARRIVAL OF THE
PRECIPITATION OCCURS AND IT FALLS MOSTLY AT NIGHT. STAY TUNED. WE
WILL ADD A MENTION IN THE HAZARDOUS WEATHER OUTLOOK TO ALLOW FOR
MORE ADVERTISEMENT OF THIS POTENTIAL STORM.
AS FOR TEMPERATURES, WE MOSTLY UTILIZED AN EVENLY WEIGHTED BLEND OF
THE GFS AND NAM MOS. HOWEVER, DID LEAN CLOSER TO THE COOLER NAM MOS
FOR SATURDAY GIVEN THE INCREASED CLOUDS AND NORTHERLY FLOW.
&&
.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
THIS TIME FRAME BEGINS WITH THE GRADUAL DEPARTURE OF THE LOW
PRESSURE SYSTEM FROM THE SHORT TERM WELL OFFSHORE AND THE ARRIVAL OF
SURFACE HIGH PRESSURE. THIS HIGH WILL DOMINATE OUR WEATHER SUNDAY,
THEN GRADUALLY SHIFT EASTWARD MONDAY INTO TUESDAY. AS UPPER-LEVEL
TROUGHING AMPLIFIES INTO THE EAST WEDNESDAY, A SURFACE LOW IS
FORECAST TO DIVE SOUTHEASTWARD WITH A WARM FRONT TO OUR SOUTH. WE
WILL HAVE TO SEE IF THIS TROUGH CAN SHARPEN UP AND ALLOW THE SURFACE
LOW TO DEVELOP FURTHER SOUTH AND POTENTIALLY TURN UP THE COAST.
WITH THE COOLER/COLDER AIR, SNOW AND/OR RAIN IS FORECAST ACROSS THE
CWA SATURDAY NIGHT AS THE SYSTEM PULLS AWAY FROM THE AREA. THEN
PERHAPS SOME MIXED PRECIPITATION WITH THE TUESDAY NIGHT/WEDNESDAY
SYSTEM. WE CHANGED THE SNOW/RAIN SHOWERS WORDING SATURDAY NIGHT TO
SNOW/RAIN WORDING TO MESH WITH THE END OF THE SHORT TERM TIME FRAME.
OTHERWISE, NO SIGNIFICANT CHANGES WERE MADE, ALTHOUGH WE BLENDED IN
A SMALL PERCENTAGE OF THE 00Z MOSGUIDE FOR SOME FIELDS TO INTRODUCE
SOME NEWER GUIDANCE INTO THE FORECAST.
&&
.AVIATION /12Z THURSDAY THROUGH MONDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.
AT 1130Z, A FRONTAL BOUNDARY WAS PUSHING TO OUR EAST AND CONDITIONS
WERE VFR AT OUR EIGHT TAF SITES. THEY SHOULD REMAIN IN THE VFR
CATEGORY THROUGH THE TAF PERIOD AS DRY AIR BUILDS INTO OUR REGION
FROM THE WEST.
THE WIND WILL BE FROM THE WEST TODAY WITH SUSTAINED SPEEDS IN THE
TEENS AND GUSTS WELL INTO THE 20S.
FOR TONIGHT THE SKY IS FORECAST TO BECOME CLEAR AND THE WEST WIND
SHOULD DIMINISH TO LESS THAN 10 KNOTS.
OUTLOOK...
DRY WEATHER IS EXPECTED FOR FRIDAY AND FRIDAY NIGHT. LOW PRESSURE
OFF THE COAST MAY BRING SOME RAIN AND SNOW TO OUR REGION FROM
SATURDAY INTO SATURDAY NIGHT. DRY WEATHER SHOULD RETURN FOR SUNDAY
AND MONDAY.
&&
.MARINE...
STRONG LOW PRESSURE, LOCATED OVER THE EASTERN GREAT LAKES DURING THE
NIGHT, WILL RACE TO THE NORTHEAST AND IT SHOULD REACH THE MARITIME
PROVINCES BY THIS EVENING. GALE FORCE WIND GUSTS REMAIN POSSIBLE ON
OUR OCEAN WATERS INTO THE EARLY AFTERNOON. ON DELAWARE BAY, THE GALE
FORCE GUSTS SHOULD BE CONFINED TO THE EARLY MORNING HOURS. THE GALE
WARNING REMAINS IN EFFECT ON OUR OCEAN WATERS UNTIL 1:00 PM AND ON
DELAWARE BAY UNTIL 9:00 AM. A SMALL CRAFT ADVISORY WILL LIKELY BE
NEEDED ONCE THE GALE WARNINGS EXPIRE. THE SMALL CRAFT ADVISORY
CONDITIONS ARE EXPECTED TO LAST UNTIL AROUND MIDNIGHT.
HIGH PRESSURE IS FORECAST TO NOSE IN FROM THE WEST FOR FRIDAY AND
FRIDAY NIGHT, BRINGING A BRIEF PERIOD OF RELATIVELY TRANQUIL
CONDITIONS.
LOW PRESSURE IS EXPECTED TO DEVELOP OFF THE SOUTHEAST COAST ON
FRIDAY NIGHT AND SATURDAY. THE LOW SHOULD MOVE TO THE NORTHEAST,
PASSING WELL TO THE EAST OF DELAWARE AND NEW JERSEY ON SATURDAY
NIGHT OR SUNDAY MORNING. SMALL CRAFT ADVISORY CONDITIONS ARE LIKELY
OVER THE WEEKEND.
&&
.TIDES/COASTAL FLOODING...
A STRONG ONSHORE FLOW COMBINED WITH THE HIGH ASTRONOMICAL TIDES
ASSOCIATED WITH THE FULL MOON MAY RESULT IN MINOR TIDAL FLOODING
AROUND THE TIME OF HIGH TIDE THIS MORNING.
HIGH TIDE ALONG THE NEW JERSEY AND DELAWARE OCEANFRONT OCCURS
BETWEEN 7:15 AND 8:15 AM. HIGH TIDE ON THE BACK BAYS AND ALONG
DELAWARE BAY OCCURS LATER THAN IT DOES ON THE OCEANFRONT.
THE WIND IS EXPECTED TO BECOME SOUTHWEST TO WEST FOR TODAY. AS A
RESULT, NO PROBLEMS ARE ANTICIPATED AROUND THIS EVENING'S HIGH TIDE.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...COASTAL FLOOD ADVISORY UNTIL 10 AM EST THIS MORNING FOR NJZ013-
014-020>027.
DE...COASTAL FLOOD ADVISORY UNTIL 10 AM EST THIS MORNING FOR
DEZ002>004.
MD...NONE.
MARINE...GALE WARNING UNTIL 1 PM EST THIS AFTERNOON FOR ANZ450>455.
GALE WARNING UNTIL 9 AM EST THIS MORNING FOR ANZ430-431.
&&
$$
SYNOPSIS...GORSE
NEAR TERM...GORSE
SHORT TERM...GORSE
LONG TERM...GORSE/KRUZDLO
AVIATION...IOVINO
MARINE...IOVINO
TIDES/COASTAL FLOODING...IOVINO
