694 
FXUS61 KPHI 112027
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
327 PM EST MON FEB 11 2013

.SYNOPSIS...
LOW PRESSURE LOCATED OVER THE GREAT LAKES IS FORECAST TO PULL A
WARM FRONT INTO OUR REGION TODAY, FOLLOWED BY A COLD FRONT THIS
EVENING. WEAK HIGH PRESSURE IS EXPECTED FOR TUESDAY INTO
WEDNESDAY. LOW PRESSURE FROM THE WEST IS FORECAST TO TRACK OFF THE
MID ATLANTIC COAST WEDNESDAY NIGHT. ANOTHER WEAK AREA OF HIGH
PRESSURE IS EXPECTED TO FOLLOW FOR THURSDAY INTO FRIDAY. A COLD
FRONT FROM THE WEST IS ANTICIPATED TO ARRIVE FRIDAY NIGHT WITH A
COLD NORTHWEST FLOW FORECAST FOR THE COMING WEEKEND.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
A 19Z SURFACE ANALYSIS PLACED LOW PRESSURE JUST NORTH OF THE CENTRAL 
GREAT LAKES WITH A COLD FRONT ACROSS WESTERN NEW YORK TO WESTERN 
VIRGINIA AND THE CAROLINAS. A WARM FRONT WAS DRAPED FROM CENTRAL 
PENNSYLVANIA, ACROSS THE DELMARVA, THEN NORTHWARD ACROSS EASTERN NEW 
JERSEY. AN UPPER AIR ANALYSIS PLACED A CLOSED LOW OVER THE GREAT 
LAKES WITH ANOTHER TROUGH ACROSS THE WEST. A STRONG 250 MB JET WAS 
FROM THE TENNESSEE VALLEY TO SOUTHERN NEW ENGLAND. THE WAA PUSH AT 
850 MB WAS LOCATED IN NEW ENGLAND AND OFF OF OUR COAST.

AN INTERESTING AND CHALLENGING SETUP TODAY AS THE WARM FRONT PRETTY 
MUCH HALTED ACROSS THE EASTERN AND FAR SOUTHERN ZONES. DESPITE HIGH 
PRESSURE TO OUR EAST AND A DEEP SOUTHERLY FLOW OCCURRING, A COLD AIR 
DAMMING SITUATION UNFOLDED. THIS WAS PROBABLY ENHANCED BY THE 
LINGERING SNOW COVER OVER PARTS OF THE AREA AND THE COLDER MORE 
DENSE AIR THAT WAS IN PLACE EARLY THIS MORNING. THE END RESULT WAS 
THE MILDER AIR STREAMING IN ALOFT STRENGTHENED THE LOW-LEVEL 
INVERSION AND KEPT THE MIXING FROM ALLOWING THE WARM FRONT TO JUMP 
NORTHWARD. THE WARM FRONT HAS GOTTEN INLAND ACROSS NEW JERSEY AND 
DELMARVA WITH THESE LOCALES IN THE 40S AND 50S, AND SOME ADDITIONAL 
WARMING IS OCCURRING ACROSS SOUTHEASTERN PENNSYLVANIA. FARTHER 
NORTH, TEMPERATURES HAVE BEEN STUCK IN THE 30S WITH A VERY SLOW RISE 
SO FAR. A WEALTH OF LOW CLOUDS AND FOG HAVE BEEN STUCK ACROSS THE 
AREA, WITH EVEN SOME DRIZZLE. THE VISIBLE SATELLITE IMAGERY SHOWS 
THE WESTERN EDGE OF THE LOW CLOUDS IN CENTRAL PENNSYLVANIA, WHICH 
HAS SHOWN A VERY SLOW EROSION SO FAR TOWARD NORTHEASTERN 
PENNSYLVANIA.

A STACKED LOW ACROSS THE GREAT LAKES WILL SLIDE EASTWARD AND TRACK 
WELL TO OUR NORTH THROUGH TONIGHT. THE ASSOCIATED COLD FRONT MAY END 
UP BEING AN OCCLUSION WHEN IT SLIDES ACROSS OUR AREA LATER THIS 
EVENING. AS THIS OCCURS, LOCALES THAT REALLY DID NOT GET INTO THE 
TRUE WARMER AIR MAY ACTUALLY HAVE THEIR TEMPERATURES SPIKE FOR A 
TIME TONIGHT. THE BULK OF THE LIFT HAS SHIFTED NORTHEAST OF OUR AREA 
ALONG WITH THE ROBUST LOW-LEVEL JET, WITH JUST A FEW ISOLATED 
SHOWERS ACROSS THE EASTERN ZONES. THE FLOW AROUND 925 MB IS FORECAST
TO GENERALLY REMAIN IN THE 30-40 KNOT RANGE THROUGH THE NIGHT, BUT 
THIS WILL BE VEERING WITH TIME. THE FORECAST SOUNDINGS MAINTAIN THE 
RATHER MOIST LOW-LEVEL PROFILE AT LEAST THROUGH EARLY THIS EVENING 
THEN DRYING OCCURS. WE BELIEVE THE NAM IS OVERDONE WITH SOCKING IN 
THE LOW CLOUDS MUCH LONGER ACROSS MUCH OF THE CWA. WE THEREFORE 
MAINTAINED LOTS OF CLOUDS AND CARRIED SOME FOG INTO AT LEAST THE 
EARLY EVENING. THE FOG IS LOCALLY DENSE, BUT CHECKING TRAFFIC 
CAMERAS IT APPEARS FOR THE MOST PART THE FOG IS NOT QUITE AS DENSE 
AS THE REPORTED VISIBILITIES SUGGEST. THEREFORE, WE WILL HOLD WITH 
THE SPECIAL WEATHER STATEMENT FOR NOW. IT APPEARS THAT SOME RESIDUAL 
DRIZZLE WILL CONTINUE, ALTHOUGH AN ISOLATED SHOWER CANNOT BE RULED
OUT AHEAD OF AN WITH THE FRONT. WE OPTED TO KEEP POPS BELOW SLIGHT 
CHC FOR MOST AND CARRIED PATCHY DRIZZLE FOR AWHILE LONGER /UNTIL THE 
FRONT MOVES THROUGH/. THE TIMING OF THE CLEARING IS OF LOWER 
CONFIDENCE, BUT ONCE THE FRONT MOVES THROUGH AND THE FLOW TURNS 
WESTERLY THE LOW CLOUDS SHOULD ERODE. THE CAA LATER TONIGHT ALONG 
WITH A WEST-NORTHWEST FLOW MAY HELP TO BRING SOME CLOUDS AND 
FLURRIES TOWARD THE POCONOS.

AS FOR LOW TEMPERATURES, WE BLENDED THE NAM/GFS MOS WITH JUST SOME 
TWEAKS MADE. THE HOURLY GRIDS WERE RESET TO THE CURRENT OBS WITH 
SOME INCORPORATION OF THE LAV/LAMP GUIDANCE TO HELP ASSIST WITH THE 
ONGOING TRENDS.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/...
AN UPPER-LEVEL TROUGH WILL BE MOVING THROUGH DURING THE COURSE OF 
THIS TIME FRAME, WITH ITS AXIS PROBABLY TO OUR EAST BY MIDDAY. LOW 
PRESSURE WILL TRACK INTO THE CANADIAN MARITIMES WITH CYCLONIC FLOW 
IN ITS WAKE. THE CAA WILL CONTINUE ESPECIALLY THROUGH THE FIRST HALF 
OF THE DAY, ALTHOUGH A SECOND SURGE OF THIS COULD SLIDE ACROSS OUR 
NORTHERN ZONES IN THE AFTERNOON. THE COLDER AIR ALOFT WILL TEAM UP 
WITH ENOUGH WARMTH IN THE BOUNDARY LAYER, WHICH WILL STEEPEN THE 
LOW-LEVEL LAPSE RATES THROUGH THE MORNING. THIS IN COMBINATION WITH 
A TIGHT PRESSURE GRADIENT FOR MUCH OF THE DAY WILL RESULT IN BREEZY 
TO WINDY CONDITIONS. THE FORECAST SOUNDINGS INDICATE THAT WIND GUSTS 
SHOULD PEAK AT ABOUT 30 KNOTS.

A FRONTAL BOUNDARY LOOKS TO BE STALLED TO OUR SOUTH AND A THERMAL 
GRADIENT IS FORECAST TO TIGHTEN THERE. THIS MAY RESULT IN SOME 
OVERRUNNING WELL TO OUR SOUTH AND SOUTHWEST, AND GIVEN THE WESTERLY
FLOW THE CLOUDS ASSOCIATED WITH THAT SHOULD TEND TO STAY TO OUR 
SOUTH. THERE SHOULD BE SOME LAKE EFFECT RESPONSE DURING THE DAY WITH 
WEST-NORTHWEST FLOW OF COLDER AIR IN PLACE. THE FLOW ABOVE THE 
SURFACE IS FORECAST TO BE ON THE STRONGER SIDE, THEREFORE PERHAPS 
MORE CLOUDS MAKE IT TO NORTHEASTERN PENNSYLVANIA ALONG WITH SOME 
FLURRIES OR A SNOW SHOWER.

AS FOR TEMPERATURES, WE GENERALLY TOOK AN EVEN BLEND OF THE NAM/GFS 
MOS.

&&

.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
WINDS SHOULD DIMINISH FOR TUESDAY NIGHT AS WEAK HIGH PRESSURE
INFLUENCES OUR REGION.

THERE REMAINS SOME DIFFERENCE IN THE MODELS REGARDING THE MID
WEEK SYSTEM. LOW PRESSURE IS FORECAST TO TAKE SHAPE OVER THE
SOUTHEASTERN STATES ON WEDNESDAY BEFORE PASSING OFF THE MIDDLE
ATLANTIC COAST ON WEDNESDAY EVENING. PRECIPITATION SHOULD BEGIN TO
OVERSPREAD OUR REGION ON WEDNESDAY AFTERNOON. AT THE ONSET,
BOUNDARY LAYER TEMPERATURE ARE ANTICIPATED TO SUPPORT RAIN IN ALL
BUT OUR FAR NORTH. DURING THE COURSE OF WEDNESDAY NIGHT, COLD AIR
SHOULD BE DRAWN INTO OUR REGION ON A NORTHEAST TO NORTH WIND
CAUSING THE RAIN TO CHANGE TO SNOW FROM NORTH TO SOUTH. IF
PRECIPITATION RATES INCREASE ON WEDNESDAY NIGHT, ADDITIONAL
COOLING FROM ALOFT IS POSSIBLE. AS A RESULT, FORECASTING THE
CHANGE-OVER TIMES AND AMOUNTS REMAINS QUITE TRICKY AT THIS POINT.
NEVERTHELESS, BASED ON THE SYSTEM'S EXPECTED TRACK AND TIMING, IT
APPEARS QUITE POSSIBLE THAT WE COULD RECEIVE OF SWATH OF A FEW
INCHES OF SNOW ACROSS A PORTION OF OUR REGION, PERHAPS FROM THE
PHILADELPHIA METROPOLITAN AREA INTO CENTRAL NEW JERSEY AND POINTS
TO THE NORTH.

ONCE THE MID WEEK SYSTEM PASSES, WE SHOULD BE IN ANOTHER BRIEF
LULL FROM THURSDAY INTO THURSDAY NIGHT. A LONG WAVE TROUGH IS
FORECAST TO SETTLE OVER THE EASTERN STATES FOR FRIDAY INTO THE
WEEKEND. A COLD FRONT FROM THE WEST IS EXPECTED TO ARRIVE ON
FRIDAY NIGHT WITH COLD AIR BUILDING INTO OUR REGION IN STEPS OVER
THE WEEKEND. WE ARE ANTICIPATING SOME CLOUDS AND SHOWERS IN THE
COLD ADVECTION. WE MAY SEE SNOW SHOWERS IN THE NORTH ON SATURDAY
WITH A MIX OF SNOW AND RAIN ELSEWHERE. IT SHOULD BE COLD ENOUGH
FOR ALL SNOW SHOWERS ON SUNDAY.

&&

.AVIATION /21Z MONDAY THROUGH SATURDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.

REST OF THIS AFTERNOON...A LOWER CONFIDENCE FORECAST. LOW CLOUDS
AND FOG AFFECTING ALL OUR TERMINALS. THIS IS RESULTING IN IFR TO 
LIFR CEILINGS. THE VISIBILITIES SHOULD VARY FROM MVFR TO IFR. MAINLY 
SOME DRIZZLE WILL CONTINUE THROUGH AT LEAST EARLY THIS EVENING. THE 
CEILINGS MAY TRY TO IMPROVE SOME TOWARD EVENING, HOWEVER CONFIDENCE 
IS RATHER LOW ON THIS. THE INLAND TERMINALS WILL TEND TO HAVE LIGHT 
AND VARIABLE WINDS THAT SHOULD TURN SOUTHERLY, WITH 10-15 KNOT WINDS 
MAINLY AT KMIV AND KACY. VISIBLE SATELLITE IMAGERY SHOWING CLOUDS 
CLEARING IN CENTRAL PENNSYLVANIA TOWARD NORTHEAST PENNSYLVANIA, AND 
THIS IS EXPECTED TO EVENTUALLY REACH OUR AREA.

TONIGHT...A COLD FRONT WILL MOVE THROUGH LATER THIS EVENING, HOWEVER 
MOISTURE STUCK NEAR THE GROUND MAY NOT MIX OUT UNTIL AFTER THE FRONT 
SHIFTS TO OUR EAST. AS A RESULT, IMPROVEMENTS WILL PROBABLY DELAYED
UNTIL THEN. LOW CONFIDENCE ON THE TIMING OF IMPROVEMENT TO VFR. 
SOUTH-SOUTHWEST WINDS WILL BECOME WEST-NORTHWEST AT AROUND 10 KNOTS.

TUESDAY...VFR. WEST-NORTHWEST WINDS 15-20 KNOTS WITH GUSTS TO
30 KNOTS.

OUTLOOK...
TUESDAY NIGHT AND WEDNESDAY...MAINLY VFR WITH LIGHT RAIN BUILDING
UP FROM THE SOUTH ON WEDNESDAY AFTERNOON.

WEDNESDAY NIGHT...RAIN CHANGING TO SNOW FROM NORTH TO SOUTH.
WIDESPREAD IFR CONDITIONS ARE POSSIBLE.

THURSDAY AND FRIDAY...MAINLY VFR.

&&

.MARINE...
LOW PRESSURE WILL TRACK WELL NORTH OF OUR AREA TONIGHT, WITH AN 
ASSOCIATED COLD FRONT SLIDING ACROSS DURING THIS EVENING. A POTENT 
LOW-LEVEL JET AROUND 925 MB WILL CONTINUE TO SHIFT TO THE EAST INTO 
THIS EVENING. THIS HAS HELPED TO MIX DOWN SOME OF THE STRONGER WINDS 
TO THE SURFACE DESPITE THE WARMING ALOFT. IT APPEARS ITS INFLUENCE 
HAS BACKED OFF THOUGH AS THE WINDS LOOKED TO ALREADY HAVE PEAKED. 
THE INCREASED SOUTHERLY FLOW THOUGH HAS ALLOWED THE SEAS TO BUILD TO 
THE 5-7 FOOT RANGE ON THE OCEAN. THE SOUTHERLY FLOW WILL CONTINUE 
AHEAD OF THE FRONT, THEN A SHIFT TO THE WEST IS EXPECTED LATER THIS 
EVENING WITH THE PASSAGE OF THE COLD FRONT. WE THEN WAIT FOR THE CAA
TO KICK IN, WHICH LOOKS TO BE THE STRONGEST STARTING AROUND 06Z 
TONIGHT. AS THIS OCCURS, THE LOW-LEVEL LAPSE RATES WILL STEEPEN AND 
BE MUCH MORE CONDUCIVE FOR DEEPER MIXING. THE MOST IDEAL TIME FRAME 
FOR THIS TO OCCUR THOUGH IS DURING THE DAY TUESDAY. ON DELAWARE BAY, 
WE MAY END UP HAVING TO WAIT FOR THIS TO OCCUR TUESDAY INSTEAD OF 
LATER TONIGHT. SINCE THE WINDS HAVE COME DOWN FOR THE MOST PART ON 
THE BAY, WE OPTED TO CANCEL THE CURRENT ADVISORY AND HOIST A NEW ONE 
FOR THE DAY TUESDAY. THE ADVISORY ON THE OCEAN CONTINUES AT LEAST 
THROUGH TUESDAY. 

OUTLOOK...
FOLLOWING A BRIEF BREAK, WE MAY APPROACH OR REACH SMALL CRAFT
ADVISORY CONDITIONS AGAIN FROM WEDNESDAY NIGHT INTO THURSDAY AS
LOW PRESSURE FROM THE WEST PASS OFF THE MIDDLE ATLANTIC COAST.

WIND SPEEDS AND WAVE HEIGHTS SHOULD BE BELOW THE SMALL CRAFT
ADVISORY CRITERIA FOR THURSDAY NIGHT INTO FRIDAY EVEN AS A COLD
FRONT APPROACHES FROM THE WEST.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EST TUESDAY FOR ANZ450>455.
     SMALL CRAFT ADVISORY FROM 5 AM TO 6 PM EST TUESDAY FOR ANZ430-
     431.

&&

$$
SYNOPSIS...IOVINO
NEAR TERM...GORSE
SHORT TERM...GORSE
LONG TERM...IOVINO
AVIATION...GORSE/IOVINO
MARINE...GORSE/IOVINO