NOWPHI/ WAS ISSUED EARLIER...

A VERY SHARP UPPER-LEVEL TROUGH /AS SEEN IN WATER VAPOR IMAGERY/ 
WILL CONTINUE TO LIFT AWAY FROM THE REGION THIS EVENING AS HIGH 
PRESSURE MOVES EASTWARD FROM THE OHIO AND TENNESSEE VALLEY'S.
AS THE WAA STRENGTHENED EARLY THIS MORNING AND MOVED TO THE COAST, 
A NARROW LINE OF CONVECTION QUICKLY FORMED JUST OFF THE NEW JERSEY 
COAST AND THEN MOVED NORTHEASTWARD INTO PORTIONS OF SOUTHERN NEW 
ENGLAND. IN ASSOCIATION WITH THE UPPER TROUGH SWINGING THROUGH THIS 
AFTERNOON AND EARLY THIS EVENING, SOME SUNSHINE HAS ALLOWED SOME 
INSTABILITY TO DEVELOP WITH STEEPER LOW-LEVEL LAPSE RATES AND A MID 
LEVEL COLD POOL /-22C AT 500 MB/. YESTERDAY THIS WAS ENOUGH TO POP 
SOME SCATTERED CONVECTION TO OUR WEST AND WE ARE NOTING SOME SHOWERS 
POPPING THIS AFTERNOON, MAINLY ACROSS SOUTHERN NEW YORK AND CENTRAL 
PENNSYLVANIA. THIS WILL BE MOVING SOUTHEASTWARD, BUT DIMINISH AS WE 
LOOSE THE DAYTIME HEATING EARLY THIS EVENING AND A VORT MAX ON THE 
BACKSIDE OF THE UPPER TROUGH LIFTS OUT. LOW-LEVEL COLD/DRY ADVECTION 
SHOULD MINIMIZE DEEP CONVECTION AND MAY EVEN PUT A LID ON THE AREAL 
EXTENT OF SHOWERS INTO THIS EVENING. SOME MODEL GUIDANCE HOWEVER 
MAINTAINS THE CHC OF SOME LOW-TOPPED SHOWERS OR A THUNDERSTORM INTO 
EARLY THIS EVENING, AND WILL JUST GO WITH ISOLATED SHOWERS FOR THE 
CENTRAL ZONES WITH A LOW CHC POP UP NORTH.

ONCE ANY SHOWERS QUICKLY DISSIPATE EARLY THIS EVENING, WE ARE 
EXPECTING A MAINLY CLEAR SKY AS HIGH PRESSURE AT THE SURFACE BUILDS 
TOWARDS OUR AREA AND HEIGHTS INCREASE. SOME CLOUDS MAY HOLD 
OVERNIGHT UP ACROSS THE FAR NORTHWEST ZONES AS SOME MOISTURE GETS 
TRAPPED ON A DEVELOPING INVERSION. THE AIRMASS APPEARS TO UNDERGO A 
FAIRLY QUICK RECOVERY VERY LATE TONIGHT ALOFT AND ESPECIALLY ON 
MONDAY. THIS IS IN RESPONSE TO WAA GETTING ORGANIZED ACROSS THE OHIO 
VALLEY AS A WARM FRONT DEVELOPS. THIS COULD SPILL SOME HIGH CLOUDS 
ACROSS MAINLY THE NORTHWEST ZONES TOWARD DAYBREAK. OTHERWISE A GOOD 
AMOUNT OF SUNSHINE IS EXPECTED ON MONDAY FOR MOST OF THE REGION AS
BUFKIT PROFILES ARE RATHER DRY AND AN INVERSION IS LOCATED NEAR 850 
MB. DECENT WAA ADVECTION EVIDENT ON MODEL PROGS DURING MONDAY AS 850 
MB TEMPERATURES RISE TO NEAR +12C BY DAYS END. THIS WILL PROMOTE A 
MILDER AFTERNOON.

BOTH THE GFS AND NAM-WRF INDICATE A WARM FRONT MOVING NORTH OF THE 
AREA DURING TUESDAY. THE MODEL GUIDANCE PROGS THE 850 MB TEMPERATURES
CLIMBING TO +14 TO +16C DURING THE DAY ON TUESDAY. WITH A GOOD 
AMOUNT OF SUNSHINE AND A STRENGTHENING SOUTHWESTERLY FLOW, SURFACE 
TEMPERATURES WILL TOP OUT IN THE LOWER 80S FOR MANY PLACES, EXCEPT A 
BIT COOLER ACROSS THE HIGHER TERRAIN. OUR REGION REMAINS IN THE 
'MILD' AIRMASS TUESDAY NIGHT AHEAD OF A COLD FRONT THAT SHOULD BE 
LOCATED NEAR LAKE ERIE AT 12Z WEDNESDAY. BASED ON THE MODELS SLOWING 
THE PROGRESSION OF THE COLD FRONT SOME, WE REMOVED THE SLIGHT CHC 
POP ACROSS THE NORTHWEST ZONES TUESDAY NIGHT.

TEMPERATURES WERE MAINLY A BLEND OF THE MAV/MET GUIDANCE ALTHOUGH 
DID NOT GO AS HIGH WITH THE DEW POINTS TUESDAY AS THE MAV DEPICTED.

 
LONG TERM /WEDNESDAY THROUGH SUNDAY/...
GENERALLY FOLLOWED THE HPC GUIDANCE WHICH LEANED TOWARD THE 00Z 
ENSEMBLE MEAN SOLUTION, HOWEVER DID MAKE SOME ADJUSTMENTS ESPECIALLY
FOR LOCAL EFFECTS AND SKY COVER.

PER HPC DISCUSSIONS, THE KEY FEATURES ALOFT INCLUDE THE DEVELOPMENT 
AND EVENTUAL EJECTION OF A CLOSED SOUTHERN STREAM WESTERN U.S. 
TROUGH TOWARD/OVER AN AMPLIFIED DOWNSTREAM EAST-CENTRAL U.S. RIDGE. 
THIS IS WHILE EMBEDDED SYSTEMS WITHIN THE NORTHERN STREAM FROM THE
PACIFIC THROUGH WEST-CENTRAL CANADA EASE INTO AN EASTERN NORTH 
AMERICA TROUGH. THE 00Z ENSEMBLE MEAN AND CANADIAN GLOBAL MODEL 
HANDLE THESE FEATURES WELL. THEIR AGREEMENT IS A REASONABLE 
SOLUTION, ESPECIALLY CONSIDERING THE HIGH RUN TO RUN VARIANCE OF THE 
RECENT GFS AND ECMWF GUIDANCE VERSUS THE MUCH MORE STEADFAST ENSEMBLE
MEAN.

EXAMINING THE POTENT WESTERN U.S. TROUGH, MOST GUIDANCE IS IN BETTER 
LARGE SCALE AGREEMENT NOW AND ALLOW AN EARLY WEEK CLOSED SYSTEM 
DEVELOPMENT. THE 00Z ECMWF AND RECENT ECMWF ENSEMBLE MEANS STILL 
CONTINUE TO EJECT THE WESTERN U.S. TROUGH ENERGY OUT MORE 
PROGRESSIVELY THAN THE GFS AND ENSEMBLE MEAN. OVERALL, HPC HAS 
PREFERRED A SOLUTION CLOSE TO THE ENSEMBLE MEAN AS THE ECMWF 
GUIDANCE, AND TO A LESSER EXTENT THE GFS, HAS OFFERED NOT GREAT 
RECENT RUN TO RUN CONSISTENCY LATER IN THE WEEK/NEXT WEEKEND 
UPSTREAM NEAR THE GULF OF ALASKA.

REGARDING THE NORTHERN STREAM FLOW, WHERE THE 00Z GFS AND ECMWF ARE 
ACTUALLY IN BETTER LARGE SCALE AGREEMENT FOR MUCH OF NORTH AMERICA 
NOW FOR MUCH OF THE WEEK. HOWEVER, THEY DO DIFFER MORE FROM THE 
PREFERRED 00Z ENSEMBLE MEAN, CANADIAN, AND SIMILAR ECMWF ENSEMBLE 
MEAN IN RAISING THE HEIGHTS MUCH FASTER CENTERED NEAR QUEBEC AROUND 
FRIDAY. HPC HAS POINTED OUT THAT THE MID LEVEL CONTOURS NEAR THE 
SAINT LAWRENCE VALLEY ARE CURVED CYCLONICALLY WITH THE ENSEMBLE 
MEANS/CANADIAN VERSUS THE DECIDEDLY ANTICYCLONIC GFS/ECMWF. THIS 
DIFFERENCE TRANSLATES TO COOLER NORTHEAST U.S. TEMPERATURES INTO 
NEXT WEEKEND WITH SHORT WAVE ENERGY MORE PRONE TO DIG TO THE LEE OF 
THE EAST-CENTRAL NORTH AMERICAN RIDGE.

THE HPC GUIDANCE AS WELL AS OTHER MODEL GUIDANCE SUGGEST THAT THE 
COLD FRONT ON WEDNESDAY IS A LITTLE SLOWER IN ITS ARRIVAL. THIS 
SLIGHT SLOWING OF THE COLD FRONT APPEARS TO NOT HAVE MUCH CHANGE IN 
THE OVERALL SHOWER CHC AS IT CROSSES OUR CWA LATE WEDNESDAY INTO 
EARLY THURSDAY. AS A RESULT, THIS FORECAST PACKAGE PRETTY MUCH 
MAINTAINS THE LOW CHC POPS TO ALLOW FOR SCATTERED SHOWERS WITH THE 
FRONT FROM NORTHWEST TO SOUTHEAST WEDNESDAY AFTERNOON TO EARLY 
THURSDAY MORNING. THE COLD FRONT THEN SETTLES SOUTHEASTWARD 
WEDNESDAY NIGHT AND MAY STILL LINGER FOR A LITTLE BIT THURSDAY 
MORNING ACROSS OUR DELMARVA ZONES. THE SLIGHT CHC IN THE GRIDS 
SHOULD COVER THAT POTENTIAL. THE FRONTAL BOUNDARY SHOULD BE PUSHED 
FAIRLY FAR SOUTH OF OUR REGION DURING THE DAY THURSDAY AS A LARGE 
ANTICYCLONE BUILDS ACROSS THE GREAT LAKES. THIS WILL PRODUCE A 
NORTHERLY WIND ACROSS OUR AREA. THIS ANTICYCLONE WILL DOMINATE OUR 
WEATHER FRIDAY AND RIGHT THROUGH NEXT WEEKEND AS RIDGING ALOFT 
BUILDS INTO THE NORTHEAST AND MID ATLANTIC. WITH A MAINLY CLEAR SKY, 
LIGHT WINDS AND LOW DEW POINTS, THIS MAY LEAD TO SOME FROST 
POTENTIAL THURSDAY NIGHT AND FRIDAY NIGHT, PARTICULARLY ACROSS THE 
NORTHWESTERN ZONES. THE BUILDING OF THE UPPER RIDGE THEN NEXT 
WEEKEND SHOULD ALLOW FOR SOME MODERATING TEMPERATURES.

THAT IS ALL FOR NOW. THANKS TO THE SURROUNDING OFFICES/HPC FOR THE
COLLABORATION TODAY. HAVE A GOOD ONE!

 
AVIATION...
MARGINAL VFR CEILINGS WITH AND JUST BEHIND THIS MORNING'S COLD FRONT 
IMPROVED TO VFR CEILINGS WELL BEHIND THE FRONT AS DRIER AIR ARRIVED, 
WITH THE RESULTING STRATOCUMULUS SCATTERING OUT EARLY THIS 
AFTERNOON. THERE IS STILL SOME MARGINAL INSTABILITY AS COOLER AIR 
ARRIVES ALOFT, OFFSETTING THE LOW LEVEL COLD ADVECTION, WITH THAT 
LOW LEVEL AIR ITSELF MODIFIED BY EARLY OCTOBER SUNSHINE. THUS, A FEW 
BUILD-UPS HAVE FORMED, AND AN ISOLATED CB CANNOT BE RULED OUT UNTIL 
CLOSER TO SUNSET. THEN, SKIES SHOULD CLEAR OUT QUICKLY. A COUPLE OF 
PIECES OF THE STATISTICAL GUIDANCE, NAMELY THE METS, ARE INDICATING 
SOME LIGHT FOG AT A FEW TAF SITES, SO A TEMPO GROUP FOR MARGINAL VFR 
VISIBILITIES IN FOG WAS INCLUDED FOR RDG, ABE, AND MIV LATE TONIGHT.
THEN, JUST SOME SCATTERED CUMULUS AT WORST FOR LATER MONDAY MORNING.

MARINE...
CONDITION CONTINUE TO BE FORECAST TO REMAIN UNDER SMALL CRAFT 
ADVISORY CRITERIA AS THE POST-FRONTAL FLOW INCREASES DURING TONIGHT 
AND ESPECIALLY MONDAY, BEFORE RELAXING MONDAY NIGHT. OTHERWISE, 
HIGH PRESSURE BUILDING OVER THE AREA SHOULD PROVIDE BENIGN MARINE 
WEATHER CONDITIONS LATER MONDAY INTO WEDNESDAY. ANOTHER COLD FRONT 
IS INDICATED FOR WEDNESDAY NIGHT, BUT AGAIN NO SIGNIFICANT WINDS OR 
WAVES ARE ANTICIPATED WITH THIS FEATURE EITHER. STRONG AND COOL HIGH 
PRESSURE IS PROGGED FOR THE END OF THIS WEEK.

&&

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

$$