447  
FXUS61 KPHI 031300  
AFDPHI  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ  
900 AM EDT TUE MAY 3 2016  
   
SYNOPSIS
 
 
BROAD LOW PRESSURE CENTERED NEAR DELAWARE BAY AT MID MORNING WILL  
PASS OFF THE COAST WITH ANOTHER LOW DEVELOPING IN THE MID ATLANTIC  
REGION LATER TODAY. A PIECE OF THE LOW MAY MOVE NORTHEAST TOWARD  
CAPE COD LATE WEDNESDAY WHILE THE PRIMARY LOW PRESSURE SYSTEM  
DEVELOPS OFF THE NEW JERSEY COAST LATER THIS WEEK. THE LOW MOVES  
OUT TO SEA SATURDAY WITH A WEAK COLD FRONTAL PASSAGE FOLLOWING  
SUNDAY MORNING. HIGH PRESSURE SHOULD BECOME DOMINANT HERE EARLY  
NEXT WEEK.  
 

 
   
NEAR TERM /UNTIL 6 PM THIS EVENING/
 
 
LOW PRESSURE WAS CENTERED IN THE DELAWARE BAY VICINITY AROUND 830  
AM. THE LOW WILL DRIFT EASTWARD AND OUT TO SEA TODAY. A SECONDARY  
LOW IS FORECAST TO DEVELOP OVER SOUTHEASTERN VIRGINIA AND  
NORTHEASTERN NORTH CAROLINA THIS AFTERNOON.  
 
THE CIRCULATION AROUND THE DEPARTING LOW WILL KEEP OUR FORECAST  
AREA IN A NORTHEASTERLY SURFACE FLOW. SOMEWHAT MILDER AIR ABOVE  
THE MARINE LAYER SHOULD MAINTAIN THE LOW CLOUDS OVER OUR REGION.  
 
THE MAIN AREA OF RAIN SHOWERS WAS MOVING NORTHEASTWARD AND OUT OF  
OUR AREA AT MID MORNING. WE ARE NOT ANTICIPATING MUCH IN THE WAY  
OF RAIN SHOWER ACTIVITY THROUGH THE BALANCE OF THE DAYLIGHT HOURS.  
HOWEVER, SHOWERS AND PERHAPS THUNDERSTORMS MAY BEGIN TO APPROACH  
NORTHEASTERN MARYLAND AND DELAWARE FROM THE WEST LATE IN THE DAY  
BASED ON SOME OF THE MODEL GUIDANCE.  
 
THE CLOUD COVER AND NORTHEASTERLY FLOW WILL KEEP TEMPERATURES  
FROM GETTING MUCH ABOVE THE UPPER 50S AND LOWER 60S IN OUR  
FORECAST AREA.  
 

 
   
SHORT TERM /6 PM THIS EVENING THROUGH 6 AM WEDNESDAY/
 
 
THE AFOREMENTIONED UPPER-LEVEL TROUGH IS FORECAST TO SHARPEN SOME  
TO OUR WEST DURING THE COURSE OF TONIGHT. THERE DOES NOT APPEAR TO  
BE A MORE FOCUSED SHORT WAVE WITHIN THE SOUTHWESTERLY FLOW ALOFT  
UNTIL TOWARD MORNING. THE 250 MB JET IS FORECAST TO MOVE RIGHT  
OVER OUR AREA TONIGHT, REMOVING THE REGION FROM THE MORE FAVORABLE  
AREA OF LIFT. AS A RESULT, WE KEPT POPS IN THE SLIGHT CHC TO LOW  
CHC RANGE AS SOME SHOWERS CANNOT BE RULED OUT. THE IDEA OF LOW  
CLOUDS CONTINUES ACROSS THE AREA GIVEN THE MARINE INFLUENCE, AND  
THEREFORE SOME DRIZZLE IS POSSIBLE AS THE FORECAST SOUNDINGS  
INDICATE SOME MID LEVEL DRYING IN PLACE.  
 
WHILE SOME FOG MAY BE AROUND IT IS NOT ANTICIPATED TO BE  
SIGNIFICANT AS THE STRATUS MAY LIMIT THE ACTUAL DEVELOPMENT  
OVERALL. THEREFORE, OPTED TO NOT INCLUDE FOG ATTM BUT THIS WILL BE  
REVISITED LATER. AS FOR THE LOW TEMPERATURES, WE USED A MOS BLEND  
OVERALL. TEMPERATURES SHOULD NOT FALL A LOT GIVEN THE CLOUD COVER  
AND DEW POINTS GENERALLY REMAINING UP DUE TO NEAR LOW-LEVEL  
SATURATION.  
 

 
   
LONG TERM /WEDNESDAY THROUGH MONDAY/
 
 
CONFIDENCE IN ANY DETAILS OF THIS FORECAST FROM WEDNESDAY THROUGH  
EARLY NEXT WEEK IS AVERAGE TO BELOW AVERAGE.  
 
A VERTICALLY DEEP CLOSED LOW WILL FORM ALONG THE MID ATLANTIC  
COAST LATER THIS WEEK THEN WEAKEN EASTWARD THIS COMING WEEKEND IN  
RESPONSE TO INTERACTION WITH A CLOSED LOW SHORT WAVE OVER HUDSON  
BAY.  
 
CALENDAR DAY AVERAGE TEMPS: ABOUT 5 DEGREES BELOW NORMAL WED-  
FRI, NEAR NORMAL SAT-MON.  
 
CONSIDERABLE CLOUDINESS WILL DOMINATE WEDNESDAY THROUGH AT LEAST  
FRIDAY EVENING WITH SEVERAL PERIODS OF SHOWERS AFFECTING THE  
REGION.  
 
SHOWER/RAIN GENERATION IS BLAMED IN PART ON INSTABILITY AS THE  
COLD POOL EVOLVES OVERHEAD WITH THE 500MB TEMP AT PHL -14C THIS  
MORNING COOLING TO -23C FRIDAY, AND SOME OF IT ATLANTIC INFLOW AS  
THE 850-700MB LOW MAY HUG THE MID ATLANTIC COAST WITH DEEP  
MOISTURE JUST TO THE LEFT OF THE TRACK.  
 
MUCH OF THE TIME FROM WEDNESDAY THROUGH FRIDAY NIGHT MAY BE  
RAIN-FREE BUT TIMING THE PERIODIC LULLS IN RAINFALL WAS NOT  
CONFIDENTLY ASSESSED THIS MORNING.  
 
IF IT CLEARS A BIT FOR A FEW HOURS AT NIGHT, THEN FOG COULD  
DEVELOP.  
 
OVERALL, DAYTIME TEMPERATURES WILL BE COOLER THAN NORMAL AND  
NIGHTTIME MINS NEAR NORMAL (NARROW DIURNALS DUE TO MOISTURE)  
 
NEXT WEEKEND INTO EARLY NEXT WEEK...IT SHOULD BRIGHTEN AND WARM  
UP TO NEAR NORMAL AS THE LOW PRESSURE SYSTEM HEADS EAST. A WEAK  
COLD FRONT COULD BRING A FEW SHOWERS WITH ITS PASSAGE SUNDAY  
MORNING BUT AT THIS TIME ANY RAIN OCCURRENCE DOES NOT LOOK TO BE  
AS PROLONGED AS WHAT MAY OCCUR LATER THIS WORK WEEK.  
 

 
   
AVIATION /13Z TUESDAY THROUGH SATURDAY/
 
 
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,  
KILG, KMIV, KACY AND SURROUNDING AREAS.  
 
TODAY...MVFR/IFR CEILINGS, WITH SOME IMPROVEMENT POSSIBLE THIS  
AFTERNOON. THE VISIBILITY WILL FAVOR VFR NOW THAT THE RAIN SHOWERS  
ARE MOVING TO THE NORTHEAST OF OUR REGION. OUR CONFIDENCE HOWEVER  
ON THE EXTENT OF THE CEILING IMPROVEMENTS BY LATE THIS AFTERNOON  
IS ON THE LOWER SIDE. EAST TO NORTHEAST WINDS MAINLY 10 KNOTS OR  
LESS.  
 
TONIGHT...MVFR TO IFR CEILINGS WITH A CONTINUED ONSHORE FLOW. A  
COUPLE OF SHOWERS OR SOME DRIZZLE POSSIBLE, WITH LOCAL MVFR  
VISIBILITY AT TIMES. NORTHEAST WINDS 3-6 KNOTS OVERALL.  
 
OUTLOOK...  
WEDNESDAY THROUGH FRIDAY...VARYING BETWEEN VFR CIGS AND MVFR  
CONDITIONS WITH THE POTENTIAL FOR RAIN SHOWERS DURING THE PERIOD.  
CONDITIONS MAY DROP TO IFR AT TIMES IN THE RAIN SHOWERS. IN A  
GENERAL A NORTHEAST WIND, WHICH MAY BECOME GUSTY 15 TO 20 KT AT  
TIMES, ESPECIALLY FRIDAY.  
 
SATURDAY...MAINLY VFR.  
 

 
   
MARINE
 
 
A WEAK LOW PRESSURE SYSTEM OVER THE AREA TODAY INTO TONIGHT WILL  
KEEP AN ONSHORE FLOW IN PLACE. WHILE THIS MAY SOME INCREASE FOR A  
TIME ESPECIALLY LATER TODAY AND TONIGHT ACROSS THE NORTHERN  
ATLANTIC COASTAL WATERS, IT SHOULD REMAIN BELOW 25 KNOTS. SINCE  
THE FLOW IS FORECAST TO BE WEAK ENOUGH, SEAS ARE ANTICIPATED TO BE  
4 FEET OR LESS. THEREFORE, THE CONDITIONS ARE EXPECTED TO BE BELOW  
SMALL CRAFT ADVISORY CRITERIA THROUGH TONIGHT.  
 
OUTLOOK...  
WEDNESDAY THROUGH THURSDAY...WAVE HEIGHTS ON OUR OCEAN WATERS MAY  
BUILD AROUND 5 FEET IN THE NORTHEASTERLY FLOW.  
 
THURSDAY NIGHT AND FRIDAY...SCA PROBABLE IN RESPONSE TO LOW  
PRESSURE ORGANIZING OFF THE NJ COAST. ATLANTIC SEAS WERE CAPPED AT  
6 FEET, 1-2 FT BELOW GUIDANCE, DUE TO LOW CONFIDENCE REGARDING THE  
WIND FIELDS ASSOCIATED WITH THE MID ATLANTIC COASTAL LOW.  
 
SATURDAY...NO MARINE HEADLINES ANTICIPATED AT THIS TIME.  
 

 
   
TIDES/COASTAL FLOODING
 
 
A LONG DURATION NORTHEASTERLY FETCH IS EXPECTED TO DEVELOP OFF  
OUR MID ATLANTIC COAST WEDNESDAY THROUGH FRIDAY. ASTRONOMICAL  
TIDES WILL BE ON THE INCREASE AS WE APPROACH THE NEW MOON ON  
FRIDAY. AS A RESULT, THERE COULD BE SOME MINOR TIDAL FLOODING  
AROUND THE TIMES OF HIGH TIDE (6-7 PM EDT) ON WEDNESDAY EVENING,  
THURSDAY EVENING AND MORE LIKELY FRIDAY EVENING (WITHIN 1 HOUR OF  
THE HIGH TIDE NEAR 8PM), PENDING MODELS CONTINUING TO FOCUS LOW  
PRESSURE DEVELOPMENT SOUTH OF LONG ISLAND LATER THIS WEEK. THE  
FRIDAY EVENING HIGH TIDE CYCLE WILL ONLY NEED A SURGE OF .7 FEET  
TO RAISE THE WATER LEVEL TO MINOR THRESHOLD. THERE IS EVEN A  
SLIGHT CHANCE OF REACHING A MODERATE THRESHOLD FRIDAY EVENING BUT  
WE CANT SAY THIS WITH CONFIDENCE SINCE ITS ALL DEPENDENT ON THE  
POSITION AND STRENGTH OF THE LOW FORMING ALONG THE MID ATLANTIC  
COAST.  
 
AS A SIDE NOTE: IT IS OUR UNDERSTANDING THAT EVENTUALLY WE WILL  
BEGIN REFERENCING COASTAL FLOODING WITH RESPECT TO MHHW WHICH WILL  
EQUATE TO INUNDATION DEPTH WITH RESPECT TO NORMALLY DRY GROUND.  
THERE WILL LIKELY BE TRAINING REFERENCES DURING THE TRANSITION.  
 

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

 
 

 
 
SYNOPSIS...DRAG  
NEAR TERM...IOVINO  
SHORT TERM...GORSE  
LONG TERM...DRAG  
AVIATION...DRAG/GORSE/IOVINO  
MARINE...DRAG/GORSE  
TIDES/COASTAL FLOODING...DRAG  
 
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