138  
FXUS61 KPHI 190122  
AFDPHI  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ  
922 PM EDT FRI APR 18 2014  
   
SYNOPSIS
 
 
A DISSIPATING FRONTAL BOUNDARY WILL MOVES ACROSS THE REGION TONIGHT  
AND INTO THE FIRST HALF OF SATURDAY. SURFACE HIGH PRESSURE WILL  
BUILD ACROSS EASTERN CANADA DOWN THROUGH THE NORTHERN MID-ATLANTIC  
ON SATURDAY AFTERNOON. THE HIGH WILL SHIFT TO THE EASTERN SEABOARD  
SUNDAY THROUGH MONDAY. ANOTHER FRONTAL BOUNDARY IS THEN EXPECTED TO  
AFFECT THE AREA NEXT TUESDAY OR WEDNESDAY, FOLLOWED BY HIGH PRESSURE  
THURSDAY INTO FRIDAY.  
 

 
   
NEAR TERM /UNTIL 6 AM SATURDAY MORNING/
 
 
FOR THE 930 PM UPDATE...FEW CHANGES MADE. THE FRONT REMAINS WELL  
NORTHWEST OF THE REGION, CUTTING THROUGH WESTERN PA UP TO  
SYRACUSE, NY. THOUGH THERE IS SOME LIGHT PRECIPITATION ASSOCIATED  
WITH THE NORTHERN PART OF THIS FRONT, IT IS PRIMARILY LOCATIONS  
NEAR LAKE ONTARIO. THUS, DO NOT THINK THAT WE WILL SEE ANY PRECIPITATION  
WITH THE FRONT.  
 
THE WRF-NMMB INITIALIZATION WAS BETTER AT 500MB, BOTH THE WRF AND  
GFS ABOUT THE SAME AT 850MB AND THE GFS BETTER AT 925MB. OVERALL NOT  
THAT GREAT A DIFFERENCE TO SHOW MODELING IMPACT DIFFERENCES THROUGH  
THE SHORT TERM.  
 
NO HEADLINES FOR TONIGHT. WE DID ADD SOME PATCHY FROST IN THE PINE  
BARRENS. DEW POINTS AND UNCERTAINTIES TO CLOUD THICKNESSES SHOULD BE  
LIMITING FACTORS FOR WIDESPREAD FROST.  
 
THE STRATOCU LEVEL WINDS ARE IN THE PROCESS OF BECOMING OFFSHORE.  
COUPLED WITH LOWERING RAP FCST RH LEVELS AT THAT LEVEL TELL US THAT  
WHAT IS LEFT OF THOSE CLOUDS NEAR THE COAST SHOULD DRIFT OFFSHORE  
AND HAVE TO FIGHT AN INCREASINGLY WRLY FLOW TO ADVECT BACK. MUCH OF  
THE CLOUDINESS OVERNIGHT IS CIRRUS BASED. THERE MAY BE SOME DEBRIS  
STRATOCU FROM THE APPROACHING CDFNT LATER TONIGHT. OVERALL  
COVERAGE FROM THEM NOT EXPECTED TO BE MUCH.  
 
WINDS SHOULD BE LIGHT TONIGHT, SO IF THE CIRRUS THICKNESS WANES, WE  
MAY BE TOO HIGH WITH MIN TEMPS IN OUTLYING AREAS. DEW POINTS HAVE  
RESPONDED UPWARD IN THE EAST TO SOUTHERLY FLOW, SO WE DO HAVE A MUCH  
HIGHER FLOOR THAN WE HAVE HAD THE LAST COUPLE OF NIGHTS FOR MIN  
TEMPS.  
 

 
   
SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/
 
 
A DEFORMATION ZONE IS EXPECTED TO DEVELOP NORTH OF THE CLOSING LOW  
IN DELMARVA ON SATURDAY. THIS SHOULD BE THE CUT-OFF FOR ANY  
CLOUDINESS FROM THE SOUTHEAST COAST SYSTEM. BY THE MIDDLE OF  
SATURDAY MORNING CLOUDS SHOULD BE LIMITED TO DELMARVA AND BE CIRRUS.  
THE AIR MASS BEHIND THE COLD FRONT IS VERY DRY AND CONVECTIVE TEMPS  
ARE NOT PREDICTED TO BE REACHED. WE SIDED CLOSER TO 850MB FULL SUN  
MAX TEMP POTENTIAL THAN THE COLDER 925S GIVEN THE PREDICTED MIXING.  
MAX TEMPS ARE CLOSER TO HIGHER STAT GUIDANCE AND ALSO TOWARD THE  
FULL SUN SOUNDING FCST MACROS. THE BETTER MIXING WILL ALSO MAKE FOR  
A BREEZIER DAY, BUT NOT THAT FAR FROM TYPICAL FOR APRIL.  
 

 
   
LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/
 
 
THE PERIOD BEGINS WITH A SURFACE HIGH TO OUR NORTH AND A SURFACE LOW  
WELL TO OUR SOUTH. THE CENTER OF THE HIGH IS FORECAST TO MOVE OFF  
THE MAINE COAST ON SUNDAY. THE AXIS OF THE HIGH GETS STRETCHED ALONG  
THE EASTERN SEABOARD ON SUNDAY NIGHT. THIS HELPS TO PUSH THE LOW OFF  
THE CAROLINAS FURTHER OUT TO SEA. ON MONDAY, THE SURFACE HIGH STARTS  
TO WEAKEN, BUT REMAINS ACROSS THE REGION. ON MONDAY NIGHT, A SURFACE  
LOW IS FORECAST TO MOVE INTO THE GREAT LAKES AS A COLD FRONT TRACKS  
THROUGH THE OHIO VALLEY. AS OF NOW, IT LOOKS LIKE THIS COLD FRONT  
STAYS TO OUR WEST ON TUESDAY AND PASSES THROUGH TUESDAY NIGHT. THE  
UPPER LOW MOVES THROUGH ON WEDNESDAY. SURFACE HIGH PRESSURE IS  
FORECAST TO BUILD ONCE AGAIN ON WEDNESDAY NIGHT AND PERSIST AT LEAST  
THROUGH THURSDAY NIGHT.  
 
TEMPERATURES WILL BE SLIGHTLY BELOW NORMAL ON SUNDAY, NEAR NORMAL  
ON MONDAY, ABOVE NORMAL ON TUESDAY, NEAR NORMAL WEDNESDAY AND  
THURSDAY, AND ABOVE NORMAL ON FRIDAY.  
 
THE ONLY PRECIPITATION EXPECTED DURING THE EXTENDED IS ASSOCIATED  
WITH THE COLD FRONT ON TUESDAY NIGHT. AS OF NOW, WE WON'T MENTION  
ANY THUNDER AS THE BEST CAPE AND LI'S ARE SOUTH AND WEST OF THE  
REGION.  
 

 
   
AVIATION /01Z SATURDAY THROUGH WEDNESDAY/
 
 
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,  
KMIV, KACY AND SURROUNDING AREAS.  
 
PREDOMINATELY VFR CONDITIONS WITH THE 00Z TAFS.  
 
HIGH CIRRUS CLOUDS EXPECTED THROUGH MUCH OF THE 00Z TAF CYCLE. A  
SMALL RISK OF MVFR CEILINGS AND MVFR VISIBILITIES AFTER 06Z, BUT  
THE CHANCE OF THIS HAPPENING IS QUITE REMOTE SO HAVE NOT  
MENTIONED IT IN THE TAFS FOR NOW. WINDS WILL BE LIGHT...GENERALLY  
AT OR BELOW 5 KT, AND MAY BE VARIABLE AT TIMES AS THE GENERAL  
DIRECTION SHIFTS FROM SOUTHEASTERLY TO SOUTHWESTERLY TO  
NORTHWESTERLY.  
 
SATURDAY. A COLD FRONTAL PASSAGE EARLY WITH A BRISKER NORTH TO  
NORTHWEST WIND EXPECTED WITH PEAK GUSTS NEAR 20 KTS. NOT TOTALLY  
CONFIDENT ABOUT GUSTINESS, MAY END UP BEING A SUSTAINED 10 TO 15  
KT DAY. ANY SEA BREEZE FRONT WOULD FORM IN THE AFTERNOON AND BE  
CONFINED CLOSE TO THE COAST, INCLUDING KACY.  
 
OUTLOOK...  
SAT NIGHT THRU MON...MOSTLY VFR, BUT WITH A SURFACE HIGH  
SETTING UP TO THE NORTH, THEN NORTHEAST, SUNDAY INTO SUNDAY NIGHT,  
WE'LL NEED TO WATCH FOR ANY STRATUS DEVELOPMENT THAT COULD LOWER  
CEILINGS.  
MON NIGHT THROUGH WEDNESDAY...MOSTLY VFR WITH SCT SHOWERS LATE  
TUESDAY AND TUESDAY NIGHT.  
 

 
   
MARINE
 
 
WE WILL CONTINUE THE SCA FOR SEAS ON THE OCEAN THROUGH TONIGHT. WAVE  
WATCH CONTINUES TO BE SLIGHTLY TOO LOW, ALTHOUGH THE GAP IS CLOSING.  
 
EARLY THIS EVENING THERE MAY BE AN UP THE DELAWARE BAY WIND MAX,  
OTHERWISE WINDS TONIGHT WINDS SHOULD BE RELATIVELY LIGHT PRECEDING  
THE FRONT.  
 
ON SATURDAY, WINDS SHOULD START INCREASING BEHIND THE FRONT, BUT THE  
BETTER MIXING DURING THE DAYTIME WILL BE ON LAND. SEAS ON THE OCEAN  
SHOULD BE BELOW SMALL CRAFT ADVISORY CRITERIA FOR MOST OF THE  
DAYTIME HOURS.  
 
OUTLOOK...  
SATURDAY NIGHT...SUB-SCA CONDITIONS.  
SUNDAY AND SUNDAY NIGHT...SCA CONDITIONS ON THE OCEAN AND  
POTENTIALLY THE LOWER DELAWARE BAY.  
MONDAY THRU TUESDAY...SUB-SCA CONDITIONS.  
TUESDAY NIGHT INTO WEDNESDAY...SCA CONDITIONS.  
 

 
   
FIRE WEATHER
 
 
IN NJ AND PA FINE FUELS MOISTURE HAVE FALLEN WITHIN RED FLAG  
CRITERIA AND MEAN RH(S) ON SATURDAY AFTERNOON SHOULD FALL BELOW 30  
PERCENT. BUT WE ARE NOT CONFIDENT ABOUT FREQUENT GUSTS EXCEEDING 20  
MPH. WE WILL MAKE MENTION IN THE FIRE WEATHER FORECAST, BUT  
CONFIDENCE IS TOO LOW TO ISSUE A WATCH. IN DE AND MD, THE POTENTIAL  
AND CRITERIA FOR STRONGER WINDS DO NOT LOOK LIKE THEY WILL BE  
REACHED PLUS THE AFTN RH LEVELS MAY ALSO BE MORE MARGINAL.  
 

 
   
PHI WATCHES/WARNINGS/ADVISORIES
 
 
PA...NONE.  
NJ...NONE.  
DE...NONE.  
MD...NONE.  
MARINE...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 6 AM EDT  
SATURDAY FOR ANZ450>455.  
 

 
 

 
SYNOPSIS...KRUZDLO  
NEAR TERM...GIGI/JOHNSON  
SHORT TERM...GIGI  
LONG TERM...KRUZDLO  
AVIATION...GIGI/JOHNSON/KRUZDLO  
MARINE...DRAG/GAINES/GIGI/KRUZDLO  
FIRE WEATHER...  
 
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