Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000
FXUS61 KPHI 130952
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
552 AM EDT SUN JUL 13 2014

.SYNOPSIS...
A WEAK WARM FRONT WILL LIFT NORTH OF OUR AREA TODAY. A COLD FRONT
WILL SLOWLY MOVE INTO A PORTION OF OUR AREA LATER MONDAY, THEN A
SECOND COLD FRONT MOVES THROUGH TUESDAY AFTERNOON INTO WEDNESDAY.
THE FRONT SHOULD MOVE FARTHER OFFSHORE DURING WEDNESDAY AND
THURSDAY. HIGH PRESSURE WILL THEN BUILD INTO OUR REGION THURSDAY
AND FRIDAY, THEN GRADUALLY SHIFT EASTWARD THROUGH SATURDAY.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
MID AND HIGH LEVEL CLOUDS CONTINUED TO DRIFT OVERHEAD FROM THE
WEST EARLY THIS MORNING. MEANWHILE, THE MOIST SOUTHERLY LOW LEVEL
FLOW WAS CAUSING PATCHY STRATUS TO DEVELOP OVER OUR REGION. ALSO,
THERE WERE SCATTERED SHOWERS AROUND THE UPPER PART OF CHESAPEAKE
BAY AROUND 545 AM. NOT MUCH CHANGE IS ANTICIPATED DURING THE
EARLY MORNING HOURS WITH ADDITIONAL SHOWERS POSSIBLE IN THE
UPSLOPE REGIONS ON EASTERN PENNSYLVANIA AND NORTHERN NEW JERSEY.

THE LOW CLOUDS SHOULD DISSIPATE BY MID MORNING AND THE MID AND
HIGH LEVEL CLOUDS ARE EXPECTED TO THIN ALLOWING FOR SOME SUNSHINE.

IF THE LINE OF THUNDERSTORMS THAT WAS OVER THE EASTERN AND
SOUTHERN GREAT LAKES REGION EARLY THIS MORNING HOLDS TOGETHER IT
SHOULD REACH OUR FORECAST AREA DURING THE LATE AFTERNOON AND EARLY
EVENING HOURS. HOWEVER, ENOUGH INSTABILITY IS FORECAST FROM THE
INTERSTATE 95 CORRIDOR NORTHWESTWARD DURING THE AFTERNOON TO
RESULT IN THE POSSIBLE DEVELOPMENT OF SCATTERED SHOWERS AND
THUNDERSTORMS AHEAD OF THE MAIN LINE. MIXED LAYER CAPE VALUES ARE
EXPECTED TO NEAR 1000 J/KG AT THAT TIME. ALSO, PLENTY OF MOISTURE
WILL BE AVAILABLE IN THE LOW LEVEL SOUTHERLY FLOW. PRECIPITABLE
WATER VALUES ARE ANTICIPATED TO RISE TO AROUND 2 INCH LATE IN THE
DAY.

WE HAVE FAVORED THE HIGH END OF THE TEMPERATURE GUIDANCE FOR
TODAY WHICH BRINGS MUCH OF OUR REGION INTO THE 85 TO 90 DEGREE
RANGE. READINGS MAY PEAK IN THE UPPER 70S IN THE ELEVATED TERRAIN
OF THE POCONOS.

A SOUTH TO SOUTHWEST SURFACE WIND IS EXPECTED TO INCREASE TO 10
TO 15 MPH FOR LATE THIS MORNING AND THIS AFTERNOON. GUSTS OF 20 TO
25 MPH ARE POSSIBLE.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM MONDAY/...
CONVECTION IS EXPECTED TO BE ONGOING IN OUR REGION THIS EVENING.
THE 4 KM WRF-NMM SUGGESTS THAT THE LINE OF THUNDERSTORMS FROM THE
NORTHWEST WILL BE ALONG THE INTERSTATE 95 CORRIDOR IN THE 7 TO 9
O`CLOCK TIME FRAME. THE CONVECTION SHOULD MOVE TO OUR EAST AND
WEAKEN LATE THIS EVENING WITH PERHAPS SOME LINGERING SHOWERS AND
ISOLATED THUNDER OVERNIGHT. PATCHY FOG IS POSSIBLE, ESPECIALLY AT
THOSE LOCATIONS THAT RECEIVE A FAIR AMOUNT OF RAINFALL.

IT WILL REMAIN QUITE HUMID TONIGHT WITH A LIGHT SOUTH TO
SOUTHWEST WIND. TEMPERATURES SHOULD NOT FALL BELOW THE LOWER AND
MIDDLE 70S AT MOST SPOTS.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
THE OVERALL SYNOPTIC SETUP IS COMPRISED OF A POTENT UPPER-LEVEL
LOW THAT SWINGS ACROSS THE MIDWEST AND GREAT LAKES MONDAY, THEN
GRADUALLY SHIFTS EAST AND NORTHEASTWARD TUESDAY AND WEDNESDAY.
THIS TROUGH IS THEN FORECAST TO GRADUALLY LIFT OUT THURSDAY AND
FRIDAY WITH THE FLOW TRENDING MORE ZONAL THEREAFTER. OVERALL, IT
APPEARS THE DIFFERENCES IN THE MODEL GUIDANCE ARE FADING WITH
BETTER CONSENSUS NOW REGARDING THE TUESDAY COLD FRONT. THERE
REMAINS THE POTENTIAL FOR STRONG TO SEVERE THUNDERSTORMS MONDAY
AND TUESDAY GIVEN A FAVORABLE SYNOPTIC SETUP, HOWEVER THE DETAILS
CARRY MORE UNCERTAINTY. WE USED A MODEL BLEND FOR MONDAY INTO
WEDNESDAY, THEN MOSTLY BLENDED THE 00Z WPC GUIDANCE INTO
CONTINUITY THEREAFTER.

FOR MONDAY AND TUESDAY...A POTENT UPPER-LEVEL LOW IS FORECAST TO
SWING ACROSS THE GREAT LAKES REGION AND THEN TOWARD THE NORTHEAST
DURING THIS TIME FRAME. THIS WILL DRIVE TWO COLD FRONTS INTO OUR
AREA, THE FIRST ONE APPROACHES LATER MONDAY WHICH MAY WEAKEN OR
DISSIPATE AS THE MAIN COLD FRONT ARRIVES TUESDAY. THE PRESENCE OF
STRENGTHENING CYCLONIC FLOW IN COMBINATION WITH AN INCREASINGLY
UNSTABLE AIR MASS WILL INITIATE SHOWERS AND THUNDERSTORMS. THIS
SHOULD ALSO BE TIED TO A LEE SIDE TROUGH MONDAY OR RESIDUAL
BOUNDARIES FROM EARLIER CONVECTION. THE EXTENT OF DEBRIS
CLOUDINESS FROM PREVIOUS DAY CONVECTION IS UNCERTAIN, HOWEVER IF
CLOUDS LINGER LATER INTO THE DAY THAN CURRENTLY ANTICIPATED THE
FORECAST HIGH TEMPERATURES MAY BE COOLER THAN CURRENTLY INDICATED.
GIVEN THE STRONGER SOUTHWESTERLY FLOW THOUGH, WE ASSUME SUFFICIENT
BREAKS IN THE CLOUD COVER OCCURS AND THIS WILL LEAD TO MODERATE TO
STRONG INSTABILITY. THE CONVECTION WOULD TEND TO DEVELOP ALONG A
LEE SIDE TROUGH DURING MONDAY AFTERNOON WITH SOME POSSIBLE
INTERSECTING WITH AN INITIAL COLD FRONT. AS STRONGER SOUTHWESTERLY
WINDS ALOFT SPREAD EASTWARD AHEAD OF THE TROUGH, THE DEEP-LAYER
SHEAR WILL INCREASE OVER THE AREA. THE GREATEST SHEAR IS FORECAST
TO BE NORTHWEST OF THE INTERSTATE 95 CORRIDOR. AS A RESULT, THERE
REMAINS THE POTENTIAL FOR SEVERE THUNDERSTORMS MONDAY AFTERNOON
AND EVENING GIVEN THE FORECAST ENVIRONMENT.

BASED ON THE FORECAST SOUNDINGS AND SHEAR PROFILES, IT APPEARS
THAT MULTICELLS AND LINE SEGMENTS WILL BE THE MAIN STORM MODE.
THIS MAY INCLUDE BOWING STRUCTURES, AND THEREFORE DAMAGING WINDS
SHOULD BE THE MAIN THREAT. THE PW VALUES ARE FORECAST TO INCREASE
TO AROUND 2 INCHES MONDAY INTO TUESDAY, WHICH WILL ALLOW FOR AREAS
OF TORRENTIAL DOWNPOURS TO OCCUR WITH THE RISK OF SOME FLOODING.
THIS COULD ALSO INCREASE THE THREAT FOR WATER LOADED DOWNDRAFTS,
AND IF ENOUGH INSTABILITY IS REALIZED EVEN COLD POOL DEVELOPMENT.
THIS MAY RELOAD ON TUESDAY, HOWEVER CONVECTION DURING THIS DAY
WILL DEPEND ON THE TIMING OF THE ACTUAL COLD FRONT AND ALSO HOW
WORKED OVER THE AIR MASS IS AND HOW IT RECOVERS. WE WILL MAINTAIN A
MENTION IN THE HAZARDOUS WEATHER OUTLOOK FOR THESE HAZARDS, AND
ALSO ADDED GUSTY WINDS AND HEAVY RAIN TO THE FORECAST FOR MONDAY.
AT LEAST SOME SHOWERS AND THUNDERSTORMS LOOK TO MAINTAIN
THEMSELVES TUESDAY NIGHT GIVEN PLENTY OF FORCING.

FOR WEDNESDAY...THE COLD FRONT SHOULD BE EASING FARTHER TO OUR
SOUTH AND EAST, WITH DRYING ARRIVING FROM THE NORTHWEST. HOWEVER,
SHORT WAVE ENERGY ROTATING AROUND THE BASE OF THE STRONG TROUGH
COULD ALLOW A WEAK SURFACE LOW TO DEVELOP ALONG THE FRONT AS IT
SHIFTS EASTWARD. THIS WOULD SLOW ITS FORWARD MOTION DOWN SOME
WEDNESDAY AND ALSO HANG BACK SHOWERS/THUNDER ESPECIALLY FOR OUR
EASTERN ZONES. THEREFORE SOME POPS WERE MAINTAINED WEDNESDAY /BUT
DECREASE THROUGH THE DAY/, WITH THE HIGHEST ACROSS THE EASTERN
AREAS. A DECENT AMOUNT OF CLOUDS MAY ALSO LINGER AS THE FLOW
REMAINS SOUTHWESTERLY ON THE EAST SIDE OF THE TROUGH AND THE AIR
ALOFT IS COOLER. OVERALL, A COOLER AND LESS HUMID AIR MASS FOLLOWS
THE FRONT.

FOR THURSDAY THROUGH SATURDAY...THE PRONOUNCED UPPER-LEVEL TROUGH
IS FORECAST TO GRADUALLY LIFT NORTHWARD AWAY FROM OUR AREA DURING
THURSDAY AND FRIDAY, ALLOWING SURFACE HIGH PRESSURE TO BUILD IN.
WE WILL STILL BE WITHIN THE CYCLONIC FLOW THURSDAY AS THE TROUGH
AXIS MOVES THROUGH, AND THERE COULD BE A FEW INSTABILITY SHOWERS.
FOR NOW, WE CONTINUED WITH A DRY FORECAST. THE FLOW THEN TRIES TO
TURN MORE ZONAL WITH EVEN SOME RIDGING ARRIVING. THIS SHOULD ALLOW
SURFACE HIGH PRESSURE OVER OUR AREA INITIALLY TO SHIFT EASTWARD
DURING FRIDAY. SOME RETURN FLOW HOWEVER SHOULD GET WAA GOING NEAR
THE OHIO VALLEY AND A LINGERING BOUNDARY MAY TRY AND WORK
NORTHWARD SATURDAY. THIS COULD BE A FOCUS FOR SOME CONVECTION.
THEREFORE, SOME LOW POPS WERE CARRIED FOR FRIDAY NIGHT AND
SATURDAY.

&&

.AVIATION /10Z SUNDAY THROUGH THURSDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.

PATCHY LOW CLOUDS DEVELOPED OVER OUR REGION DURING THE NIGHT WITH
CEILINGS MAINLY IN THE 800 TO 1500 FOOT RANGE. WHILE THE LOW
CLOUDS WILL NOT BE THE PREVAILING CONDITIONS, THEY WILL AFFECT OUR
TAF SITES AT TIMES UNTIL AROUND 1200Z OR 1300Z. OTHERWISE, VFR
CONDITIONS ARE ANTICIPATED FOR MUCH OF THE DAY.

SCATTERED THUNDERSTORMS MAY DEVELOP IN EASTERN PENNSYLVANIA AND
NORTHERN NEW JERSEY DURING THE AFTERNOON. THERE IS THE POTENTIAL
THAT A LINE OF THUNDERSTORMS FROM THE NORTHWEST WILL MOVE THROUGH
OUR REGION DURING THE LATE AFTERNOON AND EVENING HOURS. WE HAVE
MENTIONED A TWO HOUR WINDOW WITH THUNDERSTORMS IN OUR TAFS TO
INDICATE THE MOST LIKELY TIME FRAME FOR THEIR OCCURRENCE.

LINGERING CLOUDS AND SHOWERS ARE ANTICIPATED FOR TONIGHT, ALONG
WITH PATCHY FOG.

A SOUTH TO SOUTHWEST WIND IS EXPECTED TO INCREASE TO 10 TO 15
KNOTS FOR LATE THIS MORNING AND THIS AFTERNOON. WIND GUSTS OF 20
TO 25 KNOTS ARE POSSIBLE. WIND SPEEDS ARE EXPECTED TO DIMINISH
INTO THE 5 TO 10 KNOT RANGE FOR TONIGHT.

OUTLOOK...
MONDAY AND TUESDAY...SHOWERS AND THUNDERSTORMS ARE EXPECTED WITH
TIMES OF MVFR/IFR CONDITIONS. SOUTHWESTERLY WINDS 10-15 KNOTS
AHEAD OF A COLD FRONT, HOWEVER DECREASING SOME AT NIGHT. THE WINDS
SHOULD TURN MORE WEST/NORTHWEST LATER TUESDAY.

WEDNESDAY AND THURSDAY...OVERALL VFR. A CEILING MAY LINGER THOUGH
WEDNESDAY MORNING WITH SOME SHOWERS ESPECIALLY CLOSER TO THE
COAST. NORTHWESTERLY WINDS GENERALLY 10 KNOTS OR LESS.

&&

.MARINE...
AN INCREASING SOUTHERLY FLOW IS EXPECTED FOR TODAY AND TONIGHT.
AS A RESULT, WE WILL MAINTAIN THE SMALL CRAFT ADVISORY ON OUR
OCEAN WATERS FROM NOON TODAY UNTIL 600 AM MONDAY. WIND CONDITIONS
ARE ANTICIPATED TO BE JUST BELOW THE SMALL CRAFT ADVISORY
CRITERION ON DELAWARE BAY.

OUTLOOK...
MONDAY AND TUESDAY...A SOUTHERLY WIND WILL CONTINUE AHEAD OF A
COLD FRONT, AND SOME INCREASE IS FORECAST AGAIN MONDAY AFTERNOON
AND EVENING. THIS MAY BE CLOSE TO ADVISORY LEVEL GUSTS, HOWEVER IT
APPEARS TO BE MARGINAL ATTM. IN ADDITION, THE CONTINUED SOUTHERLY
FLOW WILL BUILD THE SEAS BUT AGAIN THIS APPEARS TO BE MARGINAL
ATTM. WE WOULD LIKE TO SEE HOW THE WINDS AND SEAS DEVELOP AND
REACT THROUGH TODAY AND TONIGHT, THEREFORE WE HELD OFF ON
EXTENDING THE SMALL CRAFT ADVISORY. A COLD FRONT MOVES THROUGH
LATER TUESDAY WITH A WIND SHIFT TO THE WEST AND NORTHWEST. THE
CONDITIONS SHOULD THEN BE BELOW ADVISORY CRITERIA.

WEDNESDAY AND THURSDAY...A COLD FRONT WILL SETTLE FARTHER TO OUR
SOUTH AND EAST. THIS WILL ALLOW A NORTHWESTERLY FLOW TO OCCUR
DURING MUCH OF THIS TIME, HOWEVER WINDS AND SEAS ARE ANTICIPATED
TO BE BELOW ADVISORY CRITERIA.

&&

.HYDROLOGY...
A MOISTURE LADEN AIR MASS IS FORECAST TO BE IN PLACE MONDAY AND
TUESDAY AHEAD OF A COLD FRONT. THIS IS CHARACTERIZED BY PW VALUES
AROUND 2.00 INCHES. THE PRESENCE OF A LEE SIDE TROUGH MONDAY MAY
HELP FOCUS HEAVY RAIN PRODUCING CONVECTION ALONG AND NORTHWEST OF
INTERSTATE 95 CORRIDOR, POTENTIALLY RESULTING IN AN INCREASED
FLASH FLOOD THREAT. THE FLOW IS FORECAST TO INCREASE THEREFORE THE
STORM MOTIONS SHOULD BE DECENT, HOWEVER CONVECTION SHOULD BE
EFFICIENT RAINFALL PRODUCERS. THERE ARE AREAS PARTICULARLY IN
PORTIONS OF SOUTHEASTERN AND NORTHEASTERN PENNSYLVANIA AND ALSO
NORTHERN NEW JERSEY WHERE THE 1-HOUR FLASH FLOOD GUIDANCE IS 1.50
INCHES OR LESS. THE HIGHLY URBAN AREAS ALONG THE INTERSTATE 95
CORRIDOR ARE ALSO VULNERABLE TO QUICK RUNOFF DURING TORRENTIAL
DOWNPOURS. THE UNCERTAINTY REVOLVES AROUND WHERE THE AXIS OF
HEAVIER RAIN OCCURS AS THERE IS SOME MODEL SPREAD, AND ALSO THE
ORGANIZATION OF THE CONVECTION. THEREFORE, NO FLASH FLOOD WATCH
ATTM FOR MONDAY BUT WILL MAINTAIN A MENTION IN THE HAZARDOUS
WEATHER OUTLOOK. THIS WILL BE REVISITED LATER TODAY.

&&

.TIDES/COASTAL FLOODING...
THE HIGH ASTRONOMICAL TIDES ASSOCIATED WITH THE FULL MOON MAY
RESULT IN ISOLATED TIDAL FLOODING ALONG THE NEW JERSEY AND
DELAWARE OCEANFRONT AND ON DELAWARE BAY FROM THIS EVENING INTO
TONIGHT. HOWEVER, WATER LEVELS SHOULD NOT WARRANT A COASTAL FLOOD
ADVISORY.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY FROM NOON TODAY TO 6 AM EDT MONDAY FOR
     ANZ450>455.

&&

$$

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





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