National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS61 KPHI 132213
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
613 PM EDT THU JUN 13 2013

.SYNOPSIS...
AN AREA OF LOW PRESSURE WILL SLIDE ACROSS OUR AREA TONIGHT WITH AN
ASSOCIATED COLD FRONT SHIFTING TO OUR EAST. HIGH PRESSURE WILL THEN
ARRIVE FROM THE NORTHWEST LATER FRIDAY AND SATURDAY. THE NEXT COLD
FRONT AND LOW PRESSURE SYSTEM ARE FORECAST TO MOVE THROUGH LATER
TUESDAY. HIGH PRESSURE IS THEN FORECAST TO BUILD INTO OUR REGION
DURING WEDNESDAY AND THURSDAY.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...

WITH THIS UPDATE HAVE MADE SOME TWEAKS TO THE TEMPERATURES BASED ON
THE WARM FRONTAL LOCATION AND AREAS THAT HAVE SEEN THUNDERSTORMS
OVER THE PAST FEW HOURS. WITH CONVECTION ONGOING HAVE LEFT IN
ENHANCED WORDING. AFTER THE EARLY EVENING HOURS POPS WERE LOWERED
SLIGHTLY BASED ON CURRENT RADAR.

AFTER COORDINATING WITH SPC, WE HAVE EXPANDED SEVERE THUNDERSTORM
WATCH 306 INTO MOST OF OUR DELMARVA ZONES, IN EFFECT UNTIL 7 PM.

THROUGH THIS EVENING, STRONG SURFACE LOW PRESSURE AND ITS ASSOCIATED
COLD FRONT WILL CONTINUE TO TRACK SOUTHEASTWARD ACROSS OUR CWA,
EVENTUALLY MOVING OFFSHORE AROUND MIDNIGHT. FOR MUCH OF THE REGION
THROUGH NORTHERN TO CENTRAL NJ AND MUCH OF EASTERN PA, THE OVERALL
THREAT FOR SEVERE WX HAS ENDED. CONVECTION THAT OCCURRED EARLIER
THIS MORNING HELPED TO STABILIZE THE ATMOSPHERE ACROSS THESE AREAS,
AND WHILE WE CANNOT COMPLETELY RULE OUT A FEW SCATTERED T-STORMS
THROUGH THIS EVENING AS SURFACE LOW PRESSURE PUSHES ACROSS THE
REGION, WE DO NOT ANTICIPATE ANY STRONG CONVECTIVE ACTIVITY FOR
THESE LOCATIONS. FATHER SOUTH HOWEVER, INTO FAR SOUTHERN NJ AND OUR
DELMARVA ZONES, MORE INSTABILITY REMAINS, AND THESE AREAS ARE ALSO
IN THE WARM SECTOR. WE STILL ANTICIPATE DAMAGING WINDS, HAIL, AND
HEAVY RAIN TO BE A THREAT WITH ANY T-STORMS DEVELOPING AND MOVING
INTO THESE AREAS THROUGH THIS EVENING.

ONCE THE SURFACE LOW AND TRAILING COLD FRONT PUSH EAST AND OFFSHORE,
WINDS WILL BECOME MORE NORTHWESTERLY THROUGH THE OVERNIGHT HOURS,
ALLOWING MORE STABLE AIR TO SETTLE IN ACROSS THE REGION. PRECIP
CHANCES WILL DECREASE THROUGH THE OVERNIGHT, BUT WITH AN UPPER
TROUGH STILL PROGRESSING ACROSS THE FCST AREA, SOME SCATTERED SHOWER
MAY CONTINUE. FOR OVERNIGHT LOW TEMPERATURES, WE BLENDED MET/MAV
GUIDANCE WITH CONTINUITY, WITH LOWS RANGING FROM THE LOWER TO MID
50S NORTH TO THE LOWER 60S SOUTH.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/...
OVERALL, QUIETER WEATHER IS IN STORE FRIDAY AS SURFACE LOW PRESSURE
MOVES NORTHEAST AND OUT TO SEA. HOWEVER, A MID/UPPER TROUGH WILL BE
SLOW TO MOVE EAST AWAY FROM THE REGION. WITH THIS IN MIND, WE
THEREFORE HAVE MAINTAINED SLIGHT CHANCE TO CHANCE POPS FOR A FEW
SHOWERS ACROSS THE REGION, WITH HIGHEST POPS ACROSS THE NORTH.
COOLER AND DRIER AIR WILL CONTINUE TO OVERSPREAD THE REGION ON NORTH
TO NORTHWEST WINDS, WITH DEWPOINTS MAINLY IN THE 50S. WE USED A
BLEND OF MOS GUIDANCE WITH CONTINUITY FOR MAXIMUM TEMPERATURES, WITH
HIGHS EXPECTED TO BE MAINLY IN THE LOWER 70S ACROSS THE FCST AREA.

&&

.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
THE OVERALL SYNOPTIC SETUP IS COMPRISED OF A SHARP TROUGH IN THE
EAST TO START, HOWEVER THIS LIFTS OUT AND TENDS TO GO TOWARDS A
TROUGH FROM CENTRAL CANADA TO THE CANADIAN MARITIMES. THIS RESULTS
IN A MORE ZONAL FLOW ACROSS THE U.S. WITH AN ELONGATED UPPER-LEVEL
RIDGE ACROSS THE SOUTHERN STATES. THIS FLOW IS THEN FORECAST TO
BUCKLE LATE IN THE WEEKEND AND EARLY NEXT WEEK AS ENERGY ARRIVES
INTO THE WEST COAST, WITH A SHORT WAVE TROUGH DIGGING SOUTHEASTWARD
ACROSS THE GREAT LAKES REGION MONDAY INTO TUESDAY. THIS LOOKS TO
GRADUALLY LEAD TOWARD AN UPPER-LEVEL TROUGH ARRIVING INTO THE EAST
LATE TUESDAY AND LINGERING INTO THURSDAY. WE USED A MODEL BLEND
APPROACH FOR FRIDAY NIGHT INTO SATURDAY, THEN USED WPC GUIDANCE
THEREAFTER WITH JUST SOME MINOR TWEAKS.

FOR FRIDAY NIGHT AND SATURDAY...AN UPPER-LEVEL TROUGH SHOULD BE
SHIFTING TO OUR EAST DURING THIS TIME FRAME, WITH PERHAPS SOME
LINGERING SHOWERS/THUNDER FRIDAY EVENING. ANY ACTIVITY SHOULD BE
ISOLATED/SCATTERED BEFORE ENDING EARLY, THEN A NORTHWESTERLY FLOW
OCCURS WITH WEAK HIGH PRESSURE ARRIVING FOR SATURDAY.

FOR SUNDAY AND MONDAY...THE UPPER-LEVEL FLOW IS FORECAST TO BECOME
MORE ZONAL SUNDAY BEFORE STARTING TO AMPLIFY SOME ON MONDAY. SOME
SHORT WAVE ENERGY WITHIN THIS ZONAL FLOW MAY TEAM UP WITH JUST
ENOUGH INSTABILITY AND A LEE SIDE TROUGH SUNDAY AFTERNOON AND
EVENING TO PRODUCE A FEW SHOWERS AND STORMS. THESE SHOULD MOSTLY BE
DRIVEN BY DAYTIME HEATING WITH A DIMINISHING TREND SUNDAY NIGHT,
UNLESS A CONVECTIVE CLUSTER CAN ORGANIZE TO OUR NORTHWEST. A SHORT
WAVE TROUGH THEN STARTS TO AMPLIFY INTO A MAIN TROUGH ACROSS THE
GREAT LAKES LATE SUNDAY AND MONDAY. THIS WILL DRIVE A FRONTAL
BOUNDARY EASTWARD, ALTHOUGH IT APPEARS IT HANGS BACK FAR ENOUGH
MONDAY TO KEEP THE BULK OF THE PRECIPITATION TO OUR WEST. HOWEVER, A
LEE SIDE TROUGH MAY ONCE AGAIN BE IN PLACE MONDAY ALLOWING FOR THE
POTENTIAL FOR SOME ORGANIZED SHOWERS AND THUNDERSTORMS.

FOR TUESDAY AND WEDNESDAY...WE TENDED TO FOLLOW THE PRESSURE AND
FRONTS GUIDANCE FROM WPC, WHICH SHOWS A COLD FRONT ARRIVING LATER
TUESDAY. THIS BOUNDARY MAY HAVE A SURFACE LOW MOVING UP ALONG IT AS
AN UPPER-LEVEL TROUGH AMPLIFIES SOME. THERE LOOKS TO BE AMPLE
MOISTURE ADVECTING NORTHWARD AHEAD OF THIS FEATURE, THEREFORE
LOCALLY HEAVY RAIN WILL ONCE AGAIN BE POSSIBLE ON TUESDAY. WE MAY
EVENTUALLY HAVE THE POTENTIAL OF SOME STRONG TO SEVERE CONVECTION
TUESDAY, HOWEVER THIS WILL DEPEND ON THE TIMING, FORCING AND THERMAL
PROFILES. THE COLD FRONT IS FORECAST TO BE TO OUR EAST WEDNESDAY,
WITH HIGH PRESSURE BUILDING IN FROM THE UPPER OHIO VALLEY. WE KEPT
POPS TUESDAY AT CHC FOR NOW, THEN LOWERED THEM AT NIGHT AND WENT DRY
FOR WEDNESDAY.

FOR THURSDAY...AN UPPER-LEVEL TROUGH IN THE NORTHEAST WITH GENERALLY
CYCLONIC FLOW. AT THE SURFACE, HIGH PRESSURE IS FORECAST TO SETTLE
ACROSS OUR AREA AS A FRONTAL BOUNDARY IS PUSHED WELL TO OUR SOUTH.
WE GENERALLY FOLLOWED WPC GUIDANCE CLOSELY, WITH NO PRECIPITATION
ANTICIPATED.

&&

.AVIATION /22Z THURSDAY THROUGH TUESDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.

WHILE THE THREAT OF STRONG TO SEVERE T-STORMS HAS DIMINISHED ACROSS
MUCH OF THE REGION, SOME SCATTERED T-STORM ACTIVITY IS STILL
POSSIBLE THROUGH THIS EVENING, MAINLY FROM AROUND KPHL AND
SOUTHWARD. WE HAVE INCLUDED A TEMPO GROUP ON THE TIMING FOR POSSIBLE
T-STORMS FOR THESE SITES, ALTHOUGH CONFIDENCE ON THIS IS ONLY
AVERAGE. OTHERWISE, WE EXPECT SOME SCATTERED SHWR ACTIVITY THROUGH
LATE EVENING AND INTO THE OVERNIGHT, WITH CEILINGS LOWERING TO MVFR.

BY AROUND EARLY TO MID MORNING FRIDAY, CEILINGS SHOULD BEGIN TO RISE
BACK TO VFR. WINDS FOR FRIDAY WILL BE OUT OF THE NORTH-NORTHWEST,
WITH SOME GUSTS IN THE 20 TO 25 KNOT RANGE EXPECTED. SOME ISOLATED
SHOWERS MAY BE POSSIBLE DURING THE DAYTIME FRIDAY, BUT WE DO NOT
EXPECT COVERAGE TO BE WIDESPREAD.

OUTLOOK...
FRIDAY NIGHT...A FEW SHOWERS POSSIBLE EARLY, OTHERWISE VFR.
NORTHWEST WINDS AROUND 10 KNOTS.

SATURDAY...VFR. NORTHWEST WINDS NEAR 10 KNOTS, BECOMING LIGHT
SOUTHWESTERLY AT NIGHT.

SUNDAY AND MONDAY...OVERALL VFR. A FEW SHOWERS AND THUNDERSTORMS
POSSIBLE MAINLY EACH AFTERNOON WITH A CHANCE OF LOCAL MVFR AT TIMES.
SOUTHWEST WINDS MOSTLY 5-10 KNOTS.

TUESDAY...VFR TO START, THE AREAS OF MVFR WITH POSSIBLE SHOWERS AND
SOME THUNDERSTORMS. SOUTHERLY WINDS 10-15 KNOTS.

&&

.MARINE...
WITH STRONG SURFACE LOW PRESSURE AND A TRAILING COLD FRONT TRACKING
ACROSS OUR REGION AND COASTAL WATERS TONIGHT AND INTO EARLY FRIDAY,
THE GRADIENT WILL TIGHTEN ACROSS OUR COASTAL WATERS AND FOR A TIME
INTO LOWER DELAWARE BAY. WE THEREFORE MAINTAIN THE CURRENT SMALL
CRAFT ADVISORY FOR LOWER DELAWARE THROUGH THIS EVENING AND FOR OUR
COASTAL WATERS THROUGH FRIDAY EVENING. WIND GUSTS ON OUR COASTAL
WATERS WILL APPROACH 30 KNOTS AT TIMES DURING FRIDAY, WITH SEAS IN
THE 5 TO 6 FOOT RANGE.

OUTLOOK...
AS AN UPPER-LEVEL TROUGH GRADUALLY SHIFTS TO OUR EAST FRIDAY NIGHT,
ITS INFLUENCE WILL BE WANING. THE WINDS ARE ANTICIPATED TO BE BELOW
ADVISORY CRITERIA, AND THE SEAS ON THE OCEAN SHOULD BE SUBSIDING TO
UNDER 5 FEET EARLY FRIDAY EVENING. THEREFORE, WE MAINTAINED THE
SMALL CRAFT ADVISORY FOR THE OCEAN ZONES UNTIL 00Z SATURDAY. FOR
SATURDAY THROUGH TUESDAY, WINDS SHOULD REMAIN BELOW SMALL CRAFT
ADVISORY CRITERIA. HOWEVER WITH THE POTENTIAL FOR A PROLONGED
SOUTHERLY FLOW, THE SEAS WILL START TO BUILD AND COULD REACH OR
EXCEED 5 FEET EARLY NEXT WEEK.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 8 PM EDT
FRIDAY FOR ANZ450>455.

&&

$$
SYNOPSIS...GORSE
NEAR TERM...KLINE
SHORT TERM...KLINE
LONG TERM...GORSE
AVIATION...GORSE/KLINE
MARINE...GORSE/KLINE