Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000
FXUS61 KPHI 300814
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
414 AM EDT WED JUL 30 2014

.SYNOPSIS...
A BUILDING AREA OF HIGH PRESSURE OVER THE WESTERN ATLANTIC WILL PUSH
A WARM FRONT TOWARDS THE REGION THIS WEEKEND. MULTIPLE SURFACE WAVES
LOOK TO RIDE ALONG THIS FRONTAL BOUNDARY THROUGH THE WEEKEND. HIGH
PRESSURE SHOULD MAKE A RETURN TO THE REGION EARLY NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
A MID LEVEL SHORT WAVE TROUGH SHOULD LIFT NORTHEAST THROUGH THE DAY.
THE QUESTION IS THOUGH, EXACTLY HOW CLOSE WILL IT COME TO THE
REGION. BOTH THE NAM AND GFS SHOW THE TROUGH REMAINING NORTHWEST OF
THE REGION AS INDICATED BY THE Q VECTOR AND VORTICITY FIELDS AT 850
AND 700 MB. IN ADDITION TO THE QUESTION OF HOW CLOSE THE TROUGH WILL
BE TO THE REGION, THERE ARE A FEW OTHER LIMITING FACTORS FOR
SHOWER/THUNDERSTORM DEVELOPMENT. FIRST, THE LIFT IS LIMITED TO THE
MID LEVELS, AS THERE DOES NOT APPEAR TO BE A REFLECTION OF THIS
SHORT WAVE TROUGH AT 500 MB. IN ADDITION, ANY UPPER LEVEL JETS ARE
WELL SOUTH AND EAST OF THE REGION. SECOND, LOW LEVEL MOISTURE,
ALTHOUGH SLIGHTLY HIGHER THAN YESTERDAY IS STILL LIMITED, AND THUS
WILL LIMIT INSTABILITY.

AS FOR TEMPERATURES...SHOULD SEE HIGHS A FEW DEGREES HIGHER THAN
YESTERDAY AS CLOUD COVER SHOULD BE A BIT MORE LIMITED.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM THURSDAY/...
THE PREVIOUSLY MENTIONED MID LEVEL SHORT WAVE TROUGH COMES A LITTLE
CLOSER TO THE REGION THROUGH THE EVENING HOURS, BUT STILL REMAINS
JUST NORTHWEST OF THE REGION. INSTABILITY AFTER 00Z IS LIMITED TO
MEAGER ELEVATED INSTABILITY, SO ONLY EXPECT ISOLATED SHOWERS, IF
ANYTHING. MOISTURE CONTINUES TO INCREASE, SO DESPITE THE LIGHT WINDS
DO NOT EXPECT AS MUCH RADIATIONAL COOLING AS TUESDAY NIGHT, SO SHOULD
SEE TEMPERATURES A FEW DEGREES HIGHER THAN TUESDAY MORNING.

ANOTHER SHORTWAVE TROUGH BEGINS TO APPROACH THE REGION LATE TONIGHT,
AND WHILE IT SHOULD STAY WEST OF THE REGION THROUGH THE TONIGHT
PERIOD, THE COMBINATION OF THE HEIGHT FALLS IN ADVANCE OF THE
TROUGH, AND WEAK ELEVATED INSTABILITY MAY BE ENOUGH FOR SOME SHOWER
DEVELOPMENT AROUND SUNRISE THURSDAY MORNING, PRIMARILY IN THE NW
PORTIONS OF THE REGION.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
NO DRAMATIC SHIFTS IN THE GUIDANCE OVER THE PAST 24 HOURS THOUGH IT
IS BECOMING MORE APPARENT THAT THERE IS A SPLIT AMONGST THE NCEP VS.
NON-NCEP GUIDANCE FOR THIS WEEKEND. THE DOMINATE FEATURE/DRIVING
FORCE THROUGH THE END OF THE WORK WEEK. THEREAFTER, THE STRONGER
TROUGH BEGINS TO BREAK DOWN WITH ITS CLOSED LOW OPENING UP AND
MOVING OFF TOWARDS THE NORTH AND EAST OVER THE WEEKEND. A MUCH MORE
BROAD BASED TROUGH REMAINS OVERHEAD THROUGH THE END OF THE PERIOD.

THURSDAY...STRONGER SHORTWAVE INTERACTION WITH INCREASING COLUMN
MOISTURE AND BETTER, NOT GREAT, INSTABILITY SHOULD LEAD TO WIDELY
SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS...SOME AS EARLY AS LATE
MORNING. INCREASED POPS ACCORDINGLY AND SPED UP THE TIMING OF THE
SHOWERS DURING THE DAY...SREF PROBS AND PQPF FIELDS SHOW THIS TREND.
TEMPERATURES SHOULD END UP BEING SEVERAL DEGREES BELOW NORMAL WITH
AMPLE CLOUD COVER AND SHOWER ACTIVITY.

FRIDAY...DEEPER MOISTURE ADVECTS INTO THE REGION WITH RIDGING
OFFSHORE BUILDING AND HEIGHTS ACROSS THE EAST COAST BEGINNING TO
INCREASE. BETTER INSTABILITY OVER THE EASTERN SECTIONS OF THE CWA
WITH MORE MID-LEVEL IMPULSE ACTIVITY SHOULD LEAD TO EVEN MORE
SCATTERED CONVECTION DURING THE PEAK HEATING HOURS. WEAK SURFACE
CONVERGENCE UNDER A PREDOMINANT SOUTH-SOUTHEAST FLOW WILL AIDE IN
BETTER LIFT FOR SHOWER ACTIVITY ALONG THE HIGHER TERRAIN.
TEMPERATURES SHOULD AGAIN END UP COOLER THAN NORMAL.

SATURDAY - SUNDAY...UPPER LEVEL JET DYNAMICS COME INTO PLAY MORESO
THAN PREVIOUS DAYS WITH THE RIGHT ENTRANCE REGION SITTING ACROSS THE
MID-ATLANTIC. OFFSHORE RIDGE CONTINUES TO BUILD AND PUSHES THE
INVERTED TROUGH CLOSER TOWARDS THE REGION, AS A WARM FRONT OF SORTS.
NUMEROUS WAVES MOVE ALONG THIS BAROCLINIC ZONE WITH VARIOUS DEGREES
OF STRENGTH AND SPEED. AS STATED ABOVE THERE IS A SPLIT IN THE
NUMERICAL GUIDANCE IN REGARDS TO THE TIMING AND LOCATION OF THESE
WAVES. NCEP GUIDANCE HAS A SLOWER APPROACH THAN THE NON-NCEP MEMBERS
AND ALSO WITH THEIR QPF FIELDS. NOT TOO PRUDENT TO RELY ON THE QPF
OUTPUT STILL SEVERAL DAYS AWAY, BUT THE TREND MAY BE YOUR
FRIEND...WETTER SOLUTION FOR US THIS WEEKEND. STILL LOTS OF
UNCERTAINTY TO WORK WITH THOUGH THE GFS LOOKS IN LINE WITH THE GEFS
WHILE THE EC AND ITS ENSEMBLE MEMBERS ARE IN CLOSE AGREEMENT. WE
CONTINUE WITH THE CHANCE POPS GIVEN THE UNCERTAINTY BUT HAVE ADDED
MODERATE RAIN TO THE FORECAST WITH THE AMOUNT OF AVAILABLE MOISTURE
THAT COULD BE TAPPED INTO.

MONDAY - TUESDAY...SLIGHT DRYING TREND EXPECTED ON MONDAY THOUGH NOT
ENTIRELY VOID OF ANY SHOWERS WITH COLD AIR STILL ALOFT WITH A FEW
MORE SHORTWAVES SHEARING ACROSS OVERHEAD. HIGH PRESSURE SHOULD BE
NOSING IN BY TUESDAY TO ALLOW FOR BETTER DRYING. MORE MOISTURE AND
HEAT ADVECTS IN AND COULD PUSH TEMPERATURES BACK TO NORMAL.

&&

.AVIATION /08Z WEDNESDAY THROUGH SUNDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.

VFR CONDITIONS ARE EXPECTED THROUGH THE TAF PERIOD. ONCE
AGAIN...SHOULD SEE SCT TO POSSIBLY BKN CUMULUS CLOUDS AROUND 050.
THERE IS A SMALL RISK OF SHRA AND TSRA NEAR KABE AND KRDG BETWEEN 18
AND 03Z...BUT COVERAGE IS EXPECTED TO BE VERY LIMITED SO NO MENTION
IN THE TAFS FOR NOW.

EXPECT SOUTHWESTERLY WINDS OF 5 TO 10KT THROUGH 00Z, BEFORE WINDS
ONCE AGAIN BECOME LIGHT AND VRB.

OUTLOOK...
THURSDAY - FRIDAY...MOSTLY VFR WITH SCATTERED SHOWERS AND
THUNDERSTORMS POSSIBLE EACH AFTERNOON. LOCAL SUB-VFR CONDITIONS IN
SHOWERY ACTIVITY. MEDIUM CONFIDENCE.

SATURDAY - SUNDAY...MOSTLY VFR. POSSIBILITY FOR WIDESPREAD SHOWERS
AND THUNDERSTORMS EACH DAY CREATING MVFR/IFR CONDITIONS...SOME COULD
BE HEAVY. MEDIUM CONFIDENCE ON POSSIBILITY, LOW CONFIDENCE WITH
RESPECT TO COVERAGE.

&&

.MARINE...
EXPECT WINDS AND SEAS TO REMAIN BELOW SMALL CRAFT ADVISORY TODAY AND
TONIGHT WITH WINDS STAYING BELOW 15 KT AND SEAS BETWEEN 2 AND 3
FEET.

OUTLOOK...
THURSDAY - SUNDAY...SUB-SCA CONDITIONS ARE EXPECTED ACROSS OUR
WATERS THIS PERIOD.

&&

.CLIMATE...
RECORD LOWS FOR WEDNESDAY MORNING, JULY 30TH.

PHILADELPHIA, PA....58 DEGREES SET IN 1981 AND 1914.
WILMINGTON, DE......55 DEGREES SET IN 1956.
ALLENTOWN, PA.......50 DEGREES SET IN 1997 AND 1968.
READING, PA.........52 DEGREES SET IN 1981.
ATLANTIC CITY, NJ...53 DEGREES SET IN 1981 AND 1968.
TRENTON, NJ.........54 DEGREES SET IN 1997.
GEORGETOWN, DE......54 DEGREES SET IN 1981.
MOUNT POCONO, PA....42 DEGREES SET IN 1968.

&&

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

&&

$$
SYNOPSIS...HEAVENER
NEAR TERM...JOHNSON
SHORT TERM...JOHNSON
LONG TERM...HEAVENER
AVIATION...HEAVENER/JOHNSON
MARINE...HEAVENER/JOHNSON
CLIMATE...





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