Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000
FXUS61 KPHI 201546
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1146 AM EDT WED MAY 20 2015

.SYNOPSIS...
HIGH PRESSURE ACROSS THE MIDWEST WILL EXTEND INTO THE NORTHERN
MID ATLANTIC LATER TODAY. A WEAK LOW PRESSURE SYSTEM IS THEN
FORECAST TO TRACK TO OUR SOUTH AND EAST THURSDAY AND THURSDAY
NIGHT. HIGH PRESSURE BUILDS INTO OUR AREA FOR FRIDAY NIGHT AND
MOST OF SATURDAY BEFORE SHIFTING OFFSHORE. A COLD FRONT SHOULD
DROP DOWN FROM THE NORTH LATE SUNDAY INTO MONDAY, THEN LIFT BACK
NORTH AS A WARM FRONT MONDAY NIGHT. A COLD FRONT WILL BE TO OUR
WEST DURING TUESDAY.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
HIGH PRESSURE WILL CONTINUE TO NOSE INTO OUR REGION FROM THE WEST
FOR TODAY.

A NORTHWEST WIND AROUND 10 TO 15 MPH IS ANTICIPATED WITH GUSTS UP
AROUND 20 MPH. THE NORTHWEST FLOW WILL CONTINUE TO DRAW COOL DRY
AIR INTO OUR REGION. MAXIMUM TEMPERATURES ARE FORECAST TO BE
MAINLY IN THE UPPER 60S AND LOWER 70S WITH DEW POINT READINGS
MOSTLY IN THE 30S AND LOWER 40S.

THE DECK OF STRATOCUMULUS/CUMULUS THAT WAS TRAPPED UNDER THE
TEMPERATURE INVERSION BEGAN TO THIN LATE THIS MORNING. THE TREND
SHOULD CONTINUE AS DRYING OCCURS AT THAT LEVEL.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM THURSDAY/...
CLEAR TO START WITH RADIATIONAL COOLING HALTED BY RAPIDLY
INCREASING AND LOWERING CIRRUS TO AC AFTER 06Z. NO FROST
ANTICIPATED UNLESS SKIES REMAIN CLEAR THROUGH 09Z AT WALPACK AND
PEQUEST IN NW NJ. THOSE ARE TWO OF THE MOST TYPICALLY COLDER LOW
LYING LOCATIONS IN NJ NJ.

SO 50 50 BLENDED MOS GUIDANCE LEANING TOWARD THE WARMER GFS MOS
TEMPS.

CONFIDENCE: AVERAGE.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
THE SYNOPTIC SETUP IS COMPRISED OF A CLOSED LOW ACROSS EASTERN
CANADA WHICH AMPLIFIES SOME ACROSS THE NORTHEAST, THEN IT SHIFTS
EASTWARD FRIDAY AND OVER THE WEEKEND AS ENERGY STARTS TO EJECT
INTO THE CENTRAL AND SOUTHERN PLAINS. THE LATTER WILL TEND TO
BUILD A RIDGE FROM NEAR FLORIDA NORTHWESTWARD TOWARD THE MIDWEST
SUNDAY INTO MONDAY, THEN IT SHIFTS EASTWARD INTO TUESDAY WITH THE
NORTHERN PORTION OF IT FLATTENING SOME. THE MAIN FEATURES OF
INTEREST IS WEAK LOW PRESSURE THAT TRACKS TO OUR SOUTH AND EAST
THURSDAY AND THURSDAY NIGHT, THEN A WEAK BACKDOOR FRONT LATE
SUNDAY INTO MONDAY. WE USED A MODEL BLEND FOR THURSDAY THROUGH
SATURDAY, THEN THE 00Z WPC GUIDANCE WITH CONTINUITY THEREAFTER.
SOME TWEAKS WERE THEN MADE FOLLOWING ADDITIONAL COLLABORATION WITH
OUR NEIGHBORING OFFICES.

FOR THURSDAY...A CLOSED LOW NEAR HUDSON BAY WILL SLOWLY SHIFT
EASTWARD. A SHORT WAVE TROUGH EMBEDDED IN THE LARGE SCALE TROUGH
IS FORECAST TO SWING ACROSS THE UPPER OHIO VALLEY DURING THE DAY
AND THEN NEAR THE NORTHERN MID ATLANTIC IN THE EVENING. THIS
FEATURE IS FORECAST TO DRIVE WEAK SURFACE LOW PRESSURE EASTWARD
ACROSS VIRGINIA AND NORTH CAROLINA. THERE IS A WINDOW OF
OPPORTUNITY FOR INCREASING ISENTROPIC LIFT WITHIN SOME LARGER
SCALE LIFT/PVA TO INDUCE AN AREA OF SHOWERS. THERE COULD BE ENOUGH
INSTABILITY AT LEAST ALOFT FOR A BIT MORE CONVECTIVE CONTRIBUTION.
THE BETTER SETUP IS ACROSS THE DELMARVA AND INTO FAR SOUTHERN NEW
JERSEY. THIS MAY ADJUST FARTHER NORTH SOME IF THE SHORT WAVE IS A
BIT SHARPER, AS SOME GUIDANCE INDICATES. THEREFORE WE INCREASED
THE POPS AND BROUGHT THEM NORTHWARD. THE HIGHEST POPS IN THE LOW
LIKELY RANGE ARE ACROSS THE FAR SOUTH AND SOUTHEAST AREAS, AND
THEN THEY DECREASE NORTHWARD. THE FEATURE PULLS AWAY AT NIGHT WITH
ANY SHOWERS SHIFTING OFFSHORE WITH SOME CLEARING THEREAFTER. WE
ARE EXPECTING THICKENING CLOUDS DURING THE DAY WITH MUCH OF THE
AREA PROBABLY GOING CLOUDY FOR A TIME, WHICH WILL KEEP HIGH
TEMPERATURES ON THE MUCH COOLER SIDE.

FOR FRIDAY AND SATURDAY...THE CLOSED LOW TO OUR NORTH IS FORECAST
TO BE SHIFTING EASTWARD DURING THIS TIME FRAME AS ENERGY EJECTS
INTO THE CENTRAL AND SOUTHERN PLAINS. THIS WILL TAKE SURFACE LOW
PRESSURE INTO THE CANADIAN MARITIMES FRIDAY AND A COLD FRONT
THROUGH OUR AREA, WITH A TIGHTENED PRESSURE GRADIENT IN PLACE.
THIS RELAXES FRIDAY NIGHT AND SATURDAY AS SURFACE HIGH PRESSURE
MOVES OVERHEAD. THIS MAY SET THE STAGE FOR A CHILLY LATE FRIDAY
NIGHT AND EARLY SATURDAY WITH PERHAPS PATCHY FROST ACROSS THE FAR
NORTHERN AREAS. HIGH PRESSURE THEN BEGINS TO SHIFT OFFSHORE LATE
SATURDAY AS RIDGING BUILDS TO OUR WEST.

FOR SUNDAY AND MONDAY...A RIDGE TO OUR WEST RESULTS FROM A TROUGH
ACROSS THE WEST AND ANOTHER TROUGH IN PORTIONS OF EASTERN CANADA.
THE LATTER WILL SHARPEN A BIT SUNDAY ACROSS NORTHERN NEW ENGLAND
AND THIS SHOULD SET THE STAGE FOR A BACKDOOR FRONT. IT APPEARS
THIS BOUNDARY ARRIVES IN OUR AREA SUNDAY NIGHT INTO MONDAY,
ALTHOUGH IT MAY BE WEAKER THAN THE RECENT ONE THAT AFFECTED OUR
AREA. HOWEVER, WITH THE RIDGE BUILDING AND REPOSITIONING ITSELF
OFF THE COAST OF THE SOUTHEASTERN STATES, THE BOUNDARY SHOULD
MIGRATE NORTHWARD AS A WARM FRONT. THIS SHOULD BE ASSISTED BY LOW
PRESSURE LIFTING ACROSS THE MIDWEST AND WESTERN GREAT LAKES REGION
AND DEEPENING SOUTHWESTERLY FLOW ACROSS THE EAST. SOME CONVECTION
MAY OCCUR SUNDAY NIGHT AND MONDAY ALONG THE BACKDOOR FRONT DUE TO
A POSSIBLE INSTABILITY GRADIENT AND LOW- LEVEL CONVERGENCE,
HOWEVER MUCH OF THE LIFT SHOULD BE TO OUR WEST CLOSER TO THE
WESTERN EDGE OF THE RIDGE. A WARMER AIR MASS SHOULD OVERSPREAD
THE AREA ESPECIALLY MONDAY AS THE FRONT LIFTS NORTHWARD, AND SOME
INCREASE IN THE DEW POINTS WILL ALSO OCCUR.

FOR TUESDAY...WE SHOULD BE IN THE WARM SECTOR DURING THIS TIME
FRAME AS A SHORT WAVE ALOFT AND SURFACE LOW PRESSURE TRACK TO OUR
NORTH. THIS WILL FLATTEN THE RIDGE SOME AND WHILE THE SURFACE COLD
FRONT IS CURRENTLY FORECAST TO STAY TO OUR WEST, SOME CONVECTION
CANNOT BE RULED OUT WITH SOUTHWESTERLY FLOW OF WARMER AND MORE
HUMID AIR. SOME PLACES MAY MAKE A RUN AT 90 DEGREES IN THE
AFTERNOON.

&&

.AVIATION /16Z WEDNESDAY THROUGH SUNDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.

BEFORE 17Z TODAY...NW GUSTS AROUND 20 KT AND GENERALLY BKN TO SCT
WITH CIGS AROUND 4500 FT.

AFTER 17Z TODAY...VFR FEW OR SCT SC AOA 5000 FT. NORTHWEST WIND
GUSTS 20-25 KT.

TONIGHT...VFR CLEAR TO START THEN CIGS AOA 10000 FT ARRIVING
AFTER 06Z. NORTHWEST WIND GUSTS 15-20KT DIMINISHES AND TURNS NORTH
NORTHEAST LATE.

CONFIDENCE: ABOVE AVERAGE.

OUTLOOK...
THURSDAY...CLOUDS THICKEN AND LOWER, HOWEVER AS OF NOW MAINLY
VFR. SHOWERS POSSIBLE ESPECIALLY FROM ABOUT KPHL SOUTHWARD, THEN
ENDING AT NIGHT.

FRIDAY...VFR. NORTHWEST WIND GUSTS TO AROUND 20 KNOTS,
DIMINISHING IN THE EVENING.

SATURDAY AND SUNDAY...VFR OVERALL, HOWEVER A FRONT SETTLES
SOUTHWARD SUNDAY NIGHT WITH A CHANCE OF SOME SHOWERS AND A
THUNDERSTORM.

&&

.MARINE...
TODAY...NORTHWEST WINDS GUSTY TO AROUND 20 KT.

TONIGHT...NORTHWEST WINDS GUSTY 20 KT TURN N-NE AND DIMINISH TO
LESS THAN 15 KT BY THURSDAY MORNING.

OUTLOOK...
THURSDAY AND FRIDAY...WEAK LOW PRESSURE TRACKS TO OUR SOUTH AND
EAST THURSDAY AND THURSDAY NIGHT WITH SOME INCREASE IN THE WINDS
MAINLY ACROSS THE SOUTH, THEN NORTHWEST WINDS TURN GUSTY ON
FRIDAY. DESPITE THE INCREASE IN WINDS AND SOME BUILDING OF THE
SEAS, THE CONDITIONS ARE ANTICIPATED TO BE BELOW SMALL CRAFT
ADVISORY CRITERIA.

SATURDAY AND SUNDAY...HIGH PRESSURE BUILDS OVERHEAD SATURDAY
BEFORE SHIFTING OFFSHORE SATURDAY NIGHT INTO SUNDAY. THIS MAY
ALLOW FOR SOME SEA/BAY BREEZE ENHANCED WINDS SATURDAY AFTERNOON
NEARSHORE. THE WINDS AND SEAS ARE FORECAST TO BE BELOW CRITERIA,
ALTHOUGH SOUTHWESTERLY WINDS SUNDAY SHOULD INCREASE WITH GUSTS TO
ABOUT 20 KNOTS.

&&

.FIRE WEATHER...
TODAY...WE`LL SEE WINDS GUSTING TO 20 MPH AND DRY FINE FUELS
ACROSS PORTIONS OF THE REGION, WITH MINIMUM RH`S FORECAST TO BE IN
THE 28-35 PERCENT RANGE. WE WILL NOT ISSUE ANY SPECIAL FIRE
WEATHER PRODUCTS FOR TODAY SINCE CONDITIONS ARE EXPECTED TO BE
MARGINAL.

FOR FRIDAY AFTERNOON, A NORTHWESTERLY WIND WITH GUSTS TO 20-25
MPH. THIS WILL COMBINE WITH RELATIVE HUMIDITY VALUES NEARING 30
PERCENT IN SOME AREAS ALONG WITH DRY FINE FUELS.

&&

.RIP CURRENTS...
SST`S ABOVE NORMAL AND JUST OFF THE COAST SSTS WELL ABOVE NORMAL
BY ALMOST 3C. THIS IS NOT GOOD ONCE IT TURNS HOT AND BEACHES ARE
UNGUARDED, SWIMMERS MAY TAKE CHANCES AT UNGUARDED LOCATIONS. BE
SMART ABOUT ANY SWIMMING EARLY THIS SEASON. ATLANTIC COASTAL WATER
TEMPS ARE WARMING --UPPER 50S TO MID 60S.

RIP CURRENT AWARENESS WEEK FOR MT HOLLY IS JUNE 7-13 WITH PSAS
VIA PUBLIC INFORMATION STATEMENTS, SOCIAL MEDIA, NOAA WEATHER
RADIO AND ANY MEDIA INTERVIEWS DESIRED (CONTACT OFFICE).

FOR RIP CURRENTS: DESPITE ANTICIPATED PROJECTIONS OF LOW OR
MODERATE RISK THROUGH THE MEMORIAL DAY WEEKEND, EARLY SEASON
FATALITIES OCCUR WHEN SWIMMING AT UNGUARDED TIMES/LOCATIONS.
WEAKER SWIMMERS OR SWIMMING IN AREAS WHERE RIP CURRENTS ARE
STRONGER (JETTIES) CAN QUICKLY BECOME LIFE THREATENING. WHEN
TRAINED LIFEGUARDS ARE NOT NEARBY, TIMELY RESCUE IS MUCH LESS
LIKELY. LETS GET THROUGH THE MONTH OF MAY WITH ALL SWIMMERS SAFE!
SWIM IN THE PRESENCE OF LIFE GUARDS! THANK YOU.

&&

.CLIMATE...
**TOP 10 WARMEST MAY APPEARS LIKELY IN PTNS OF THE FORECAST
AREA**

THE FIRST 19 DAYS OF MAY IN OUR FORECAST AREA ARE AVERAGING
WITHIN ABOUT 1/2 DEGREE OF 7 DEGREES ABOVE NORMAL.

BASED ON THE ENSEMBLE AND A FORECAST THAT IS DETERMINISTICALLY
CONSERVATIVE INCLUDING OUR 330 PM MAY 19 PROJECTIONS THROUGH THE
26TH AND THEN THE CONSERVATIVE FTPRHA THEREAFTER THROUGH THE 29TH
AND NORMAL TEMPS THE 30TH AND 31ST...OUTLOOKS A TOP 10 WARMEST MAY
ON RECORD. IN ACTUALITY, WE THINK TEMPS WILL BE ABOVE NORMAL THOSE
LAST TWO DAYS OF THE MONTH ALMOST ASSURING A TOP 10 WARMEST MAY.

FOR PHILADELPHIA...PERIOD OF RECORD BACK TO 1874. PROJECTING AN
AVG TEMP OF 68.7 OR NEARLY 5 DEGREES ABOVE NORMAL (4.8) AND 3RD
WARMEST ON RECORD. WARMEST WAS 70.8 IN 1991. THEN 69.2 2004.

FOR ALLENTOWN...POR TO 1922. PROJECTING 65.0 OR 5.1 DEGREES ABOVE
NORMAL AND 8TH WARMEST ON RECORD. WARMEST WAS 67.2 IN 1991.

NORMAL FIRST DATE OF 90 OR HIGHER.

PHILADELPHIA MAY 29
ALLENTOWN MAY 30
WILMINGTON JUNE 4
ATLANTIC CITY JUNE 11.

&&

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

&&

$$

SYNOPSIS...GORSE
NEAR TERM...IOVINO
SHORT TERM...DRAG
LONG TERM...GORSE
AVIATION...DRAG/GORSE
MARINE...DRAG/GORSE
FIRE WEATHER...DRAG/GORSE
RIP CURRENTS...DRAG
CLIMATE...DRAG


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