[top]
000
FXUS61 KPHI 160955
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
555 AM EDT WED MAY 16 2012
.SYNOPSIS...
ANOTHER COLD FRONT WILL MOVE THROUGH THE REGION LATE TODAY WITH HIGH
PRESSURE MOVING IN BEHIND THE FRONT. THIS HIGH WILL SETTLE OVER THE
REGION THROUGH THE WEEKEND AND THE EARLY PART OF NEXT WEEK. IT WILL
GRADUALLY SLIDE TO THE EAST OVER THE NEXT FEW DAYS BEFORE ANOTHER
COLD FRONT MOVES TOWARDS US NEXT TUESDAY.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
THE EARLY MORNING FORECAST PROBLEM IS LOW CLOUDS AND FOG. SO
FAR...THE AREA OF FOG ALONG THE NEW JERSEY COAST DOES NOT APPEAR
TO HAVE BECOME ANY BETTER ORGANIZED. WHILE THERE COULD BE SOME
AREAS WHERE VISIBILITY DROP TO ONE-HALF MILE...FOR NOW NO
HEADLINES FOR FOG ARE ANTICIPATED. IN ADDITION...PATCHY FOG WILL
BE MENTIONED IN AREAS THAT RECEIVED HEAVY RAIN EARLY THIS
MORNING...AND TRENDS WILL BE FOLLOWED IN THESE AREAS.
THE LOW CLOUDS AND FOG SHOULD EXIT FAIRLY QUICKLY WITH THE STRONG
MID MAY SUN AND NOT MUCH IN THE WAY OF CLOUDS ABOVE IT. THIS SHOULD
ALSO RESULT IN STRONG LOW LEVEL WARMING...WHICH IN TURN SHOULD ALLOW
MIXING FROM ABOVE 850 MB. BASED ON THIS...WE RAISED HIGH
TEMPERATURES FOR TODAY...BRINGING THEM CLOSE TO THE MOS BLEND.
THE MAIN FORECAST QUESTION FOR THIS AFTERNOON/EVENING IS POTENTIAL
FOR MORE THUNDERSTORM ACTIVITY. THE SIGNALS ARE MIXED...AS LOW LEVEL
MOISTURE COULD ULTIMATELY BE THE LIMITING FACTOR FOR DEVELOPMENT.
THE BEST LOW LEVEL MOISTURE COULD BE SWEPT EAST THIS MORNING WITH
THE NOCTURNAL CONVECTION. MIXING IN THE STRONG SUNSHINE COULD ALSO
TEND TO LOWER DEW POINTS THIS AFTERNOON...WHICH COULD IN TURN CUT
DOWN ON THE LOW LEVEL MOISTURE AVAILABLE FOR CONVECTION.
THE BEST SURFACE CONVERGENCE SHOULD STRETCH FROM THE NORTHERN LEHIGH
VALLEY INTO NORTHERN NEW JERSEY DURING THE LATE AFTERNOON AND EARLY
EVENING. IN ADDITION...THE SHEAR INCREASES ACROSS THE NORTH AS A
SHORT WAVE PASSES NORTH OF THE AREA. BASED ON THE ABOVE...IT WOULD
APPEAR AS THOUGH THE BEST CHANCE OF ORGANIZED CONVECTION WOULD BE
HERE...BUT AS MENTIONED EARLIER MOISTURE COULD BE THE LIMITING
FACTOR.
FURTHER SOUTH...ACROSS NORTHERN DELAWARE...SOUTHEAST PENNSYLVANIA
AND SOUTHERN NEW JERSEY...INSTABILITY SHOULD BE IN BETTER SUPPLY.
MODIFIED SOUNDINGS SHOW MLCAPE VALUES OVER 1000 J/KG...WITH CAPE
PROFILES INDICATIVE OF GOOD UPDRAFTS. HOWEVER...SURFACE CONVERGENCE
HERE IS NOT AS GOOD...NOR IS THE BULK SHEAR. SO...FOR NOW THE BEST
CHANCE OF THUNDER WILL BE PLACED ACROSS THE NORTH...WITH A MENTIONED
RETAINED FURTHER SOUTH. FOR NOW...NO ENHANCED WORDING WILL BE PLACED
IN THE FORECAST.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM THURSDAY/...
THE FIRST PART OF THE EVENING WILL BE A CONTINUATION OF THE
CONVECTIVE POTENTIAL...WITH THE BEST CHANCE ACROSS THE NORTH. AS WAS
THE CASE LATE TUESDAY EVENING AND EARLY THIS MORNING...THE
INSTABILITY COULD LINGER...AND THE MENTION OF THUNDER WAS CONTINUED
INTO THE LATE EVENING HOURS.
THE FRONT SHOULD CROSS THE AREA BETWEEN 0300 UTC AND 0600 UTC
THURSDAY. THE PASSAGE OF THE FRONT SHOULD CUT OFF THE LOW LEVEL
INSTABILITY...AND A CHANCE OF SHOWERS WAS CARRIED WITH THE FRONT TO
THE COAST. BEHIND THE FRONT...THE AIRMASS CHANGE IS SLOW. THERE
COULD EVEN BE SOME PATCHY FOG AHEAD OF THE FRONT IN THE LATE
EVENING...BUT WILL NOT BE MENTIONED YET.
BEHIND THE FRONT...THE LOW LEVEL PUSH COULD ALLOW FOR GUSTY NORTH
WINDS DURING THE EARLY MORNING HOURS. FOR THE MOST PART...BECAUSE OF
THE SLOW AIRMASS CHANGE...LOWS WERE BASED ON A NOS BLEND.
&&
.LONG TERM /THURSDAY THROUGH TUESDAY/...
HIGH PRESSURE CENTERED OVER THE GREAT LAKES WILL GRADUALLY WORK ITS
WAY THROUGH OUR REGION DURING MOST OF THE EXTENDED PERIOD. SKIES
WILL BE MOSTLY CLEAR ALLOWING DAYTIME TEMPERATURES TO CLIMB INTO THE
MID TO UPPER 70S. THE ONLY CAVEAT ONE COULD SEE WOULD BE ON FRIDAY
AND SATURDAY WITH ONSHORE FLOW...WILL BE STRONGER IN THE AFTERNOON
WHEN PEAK HEATING WOULD TAKE PLACE ALLOWING A SEABREEZE TO MOVE
PRETTY FAR INLAND BOTH DAYS.
OTHERWISE, THE RETURN FLOW BEHIND THE DEPARTING HIGH PRESSURE SYSTEM
WILL BRING INCREASED MOISTURE ACROSS THE AREA EARLY NEXT WEEK. THE
UPPER HIGH WILL BE ON THE WANE WITH LOWERING HEIGHTS INDICATED AND A
WEAK LOW ON THE 12Z GFS. AN INCREASED CHC FOR SHOWERS/TSTMS WILL BE
OVER THE REGION THEN. SMALL CHC POPS ARE IN THE FCST FOR NOW
COVERING MON NGT INTO EARLY WED.
&&
.AVIATION /10Z WEDNESDAY THROUGH SUNDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.
CONTENDING WITH THE CONVECTIVE COMPLEX EARLY THIS MORNING NEAR THE
KPHL METRO AIRPORTS. FOR NOW...THE THUNDERSTORMS WILL BE INCLUDED
THROUGH ABOUT 0800 UTC...WITH MAINLY MVFR CONDITIONS WITH CEILINGS
AND VISIBILITY IN HEAVY RAIN.
ELSEWHERE...STARTING TO SEE IFR CONDITIONS IN SOUTHERN NEW JERSEY AT
KACY AND KMIV...AS WELL AS KABE. IT WOULD APPEAR AS THOUGH MOST
PLACES WILL SEE A PERIOD OF MVFR/IFR CONDITIONS THROUGH ABOUT 1300
UTC...AS THE LOW LEVEL MOISTENS ENOUGH FOR LOW CEILINGS. IT IS
POSSIBLE THAT KMIV AND KACY COULD SEE VISIBILITIES DROP BELOW 1SM IN
FOG...BUT LOW CONFIDENCE IN THIS MEANS IT STAYS OUT OF THE FORECAST
OF NOW.
THE LOW CLOUD AND FOG SHOULD BEGIN TO DISSIPATE BETWEEN 1200 UTC AND
1400 UTC...WITH LOW IFR CONDITIONS REMAINING IN PLACE AT KACY THE
LONGEST. AFTER THIS...WEST SOUTHWEST FLOW WILL DEVELOP AHEAD OF A
COLD FRONT. VFR CONDITIONS ARE EXPECTED FOR THE REMAINDER OF THE DAY.
SCATTERED THUNDERSTORMS COULD DEVELOP AHEAD OF THE FRONT LATE THIS
AFTERNOON AND THIS EVENING...MAINLY AFFECTING AREAS NORTH AND EAST
OF KPHL. FOR NOW...THE MENTION OF THUNDER WAS LEFT OUT OF THE
FORECAST...BUT THIS COULD BE REVISITED LATER.
ONCE THE FRONT PASSES LATE THIS EVENING...VFR CONDITIONS ARE
EXPECTED WITH A LIGHT NORTH BREEZE. THERE ARE SOME INDICATIONS THAT
MVFR FOG COULD DEVELOP JUST AHEAD OF THE FRONT IN PLACES LIKE KMIV
AND KACY...BUT THIS CAN BE REEVALUATED WITH THE 1200 UTC FORECASTS.
OUTLOOK...
THURSDAY THROUGH SUNDAY...VFR. A SEABREEZE MAY DEVELOP ON FRIDAY AND
SATURDAY.
&&
.MARINE...
WINDS REMAIN BELOW SMALL CRAFT LEVELS EARLY THIS MORNING...AS THE
THE COASTAL WATERS REMAINS ON THE WESTERN EDGE OF THE GRADIENT
ASSOCIATED WITH THE SURFACE HIGH WELL EAST OF THE WATERS.
HOWEVER...SEAS REMAIN NEAR THE 5 FOOT BENCHMARK FOR A SMALL CRAFT
ADVISORY.
IT IS A TOUGH CALL AS TO HOW LONG SEAS WILL REMAIN NEAR 5 FEET ON
THE OCEAN. THE WNAWAVE GUIDANCE SUGGESTS THAT THIS WILL OCCUR INTO
THIS EVENING...BUT THE 8 SECOND PERIOD SUGGESTS THAT TIME FRAME MAY
BE TOO LONG. FOR NOW...THE SMALL CRAFT ADVISORY WILL BE EXTENDED
INTO THE LATE MORNING...AND TRENDS CAN BE FOLLOWED DURING THE DAY
TO DETERMINE WHEN THE SEAS COULD DROP.
THE SOUTHWEST FLOW AHEAD OF AN APPROACHING COLD FRONT COULD APPROACH
15 KNOTS THIS AFTERNOON AND EVENING...BUT PROBABLY NOT MORE THAN
THAT AS THE WARM BOUNDARY LAYER RUNS OVER THE COOLER WATER. THE BEST
GUSTS SHOULD BE NEARSHORE ON THE OCEAN AND OVER THE DELAWARE BAY.
THE FRONT CROSSES THE AREA LATE THIS EVENING AND EARLY THURSDAY
MORNING. WITH THE FRONTAL PASSAGE...A FEW GUSTS TO 20 KNOTS ARE
POSSIBLE IN THE LOW LEVEL PUSH. AT THIS POINT...IT APPEARS THAT THE
NORTHERLY FLOW WILL REMAIN BELOW SMALL CRAFT LEVELS THROUGH SUNRISE.
OUTLOOK...
WITH HIGH PRESSURE OVER OUR WATERS ON THURSDAY, WE WILL CONTINUE
TO EXPERIENCE TRANQUIL CONDITIONS. WINDS WILL SWING TO THE EAST-
NORTHEAST ON FRIDAY AND REMAIN THERE THROUGH MONDAY.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 11 AM EDT THIS MORNING FOR
ANZ450>455.
&&
$$
SYNOPSIS...HEAVENER
NEAR TERM...HAYES
SHORT TERM...HAYES
LONG TERM...HEAVENER/O`HARA
AVIATION...HAYES/HEAVENER
MARINE...HAYES/HEAVENER
000
FXUS61 KPHI 160729
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
329 AM EDT WED MAY 16 2012
.SYNOPSIS...
ANOTHER COLD FRONT WILL MOVE THROUGH THE REGION LATE TODAY WITH HIGH
PRESSURE MOVING IN BEHIND THE FRONT. THIS HIGH WILL SETTLE OVER THE
REGION THROUGH THE WEEKEND AND THE EARLY PART OF NEXT WEEK. IT WILL
GRADUALLY SLIDE TO THE EAST OVER THE NEXT FEW DAYS BEFORE ANOTHER
COLD FRONT MOVES TOWARDS US NEXT TUESDAY.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
THE FIRST ORDER OF BUSINESS EARLY THIS MORNING IN THE DISPOSITION OF
THE LEFTOVER CONVECTION. THE BATCH OF CONVECTION...WHICH FORMED IN
THE LOW LEVEL CONVERGENCE ASSOCIATED WITH THE BEST REMAINING
INSTABILITY...PRODUCED VERY HEAVY RAIN. AS THE SHORT WAVE THAT
HELPED ORGANIZE THE BATCH MOVES NORTHEAST...A SLOW WEAKENING OF THE
ACTIVITY IS LIKELY...BUT IT MAY NOT BE COMPLETELY GONE BEFORE THE
NEXT FORECAST ISSUANCE.
THE NEXT FORECAST PROBLEM IS LOW CLOUDS AND FOG. SO FAR...THE AREA
OF FOG ALONG THE NEW JERSEY COAST DOES NOT APPEAR TO HAVE BECOME ANY
BETTER ORGANIZED. WHILE THERE COULD BE SOME AREAS WHERE VISIBILITY
DROP TO ONE-HALF MILE...FOR NOW NO HEADLINES FOR FOG ARE
ANTICIPATED. IN ADDITION...PATCHY FOG WILL BE MENTIONED IN AREAS
THAT RECEIVED HEAVY RAIN EARLY THIS MORNING...AND TRENDS WILL BE
FOLLOWED IN THESE AREAS.
THE LOW CLOUDS AND FOG SHOULD EXIT FAIRLY QUICKLY WITH THE STRONG
MID MAY SUN AND NOT MUCH IN THE WAY OF CLOUDS ABOVE IT. THIS SHOULD
ALSO RESULT IN STRONG LOW LEVEL WARMING...WHICH IN TURN SHOULD ALLOW
MIXING FROM ABOVE 850 MB. BASED ON THIS...WE RAISED HIGH
TEMPERATURES FOR TODAY...BRINGING THEM CLOSE TO THE MOS BLEND.
THE MAIN FORECAST QUESTION FOR THIS AFTERNOON/EVENING IS POTENTIAL
FOR MORE THUNDERSTORM ACTIVITY. THE SIGNALS ARE MIXED...AS LOW LEVEL
MOISTURE COULD ULTIMATELY BE THE LIMITING FACTOR FOR DEVELOPMENT.
THE BEST LOW LEVEL MOISTURE COULD BE SWEPT EAST THIS MORNING WITH
THE NOCTURNAL CONVECTION. MIXING IN THE STRONG SUNSHINE COULD ALSO
TEND TO LOWER DEW POINTS THIS AFTERNOON...WHICH COULD IN TURN CUT
DOWN ON THE LOW LEVEL MOISTURE AVAILABLE FOR CONVECTION.
THE BEST SURFACE CONVERGENCE SHOULD STRETCH FROM THE NORTHERN LEHIGH
VALLEY INTO NORTHERN NEW JERSEY DURING THE LATE AFTERNOON AND EARLY
EVENING. IN ADDITION...THE SHEAR INCREASES ACROSS THE NORTH AS A
SHORT WAVE PASSES NORTH OF THE AREA. BASED ON THE ABOVE...IT WOULD
APPEAR AS THOUGH THE BEST CHANCE OF ORGANIZED CONVECTION WOULD BE
HERE...BUT AS MENTIONED EARLIER MOISTURE COULD BE THE LIMITING
FACTOR.
FURTHER SOUTH...ACROSS NORTHERN DELAWARE...SOUTHEAST PENNSYLVANIA
AND SOUTHERN NEW JERSEY...INSTABILITY SHOULD BE IN BETTER SUPPLY.
MODIFIED SOUNDINGS SHOW MLCAPE VALUES OVER 1000 J/KG...WITH CAPE
PROFILES INDICATIVE OF GOOD UPDRAFTS. HOWEVER...SURFACE CONVERGENCE
HERE IS NOT AS GOOD...NOR IS THE BULK SHEAR. SO...FOR NOW THE BEST
CHANCE OF THUNDER WILL BE PLACED ACROSS THE NORTH...WITH A MENTIONED
RETAINED FURTHER SOUTH. FOR NOW...NO ENHANCED WORDING WILL BE PLACED
IN THE FORECAST.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM THURSDAY/...
THE FIRST PART OF THE EVENING WILL BE A CONTINUATION OF THE
CONVECTIVE POTENTIAL...WITH THE BEST CHANCE ACROSS THE NORTH. AS WAS
THE CASE LATE TUESDAY EVENING AND EARLY THIS MORNING...THE
INSTABILITY COULD LINGER...AND THE MENTION OF THUNDER WAS CONTINUED
INTO THE LATE EVENING HOURS.
THE FRONT SHOULD CROSS THE AREA BETWEEN 0300 UTC AND 0600 UTC
THURSDAY. THE PASSAGE OF THE FRONT SHOULD CUT OFF THE LOW LEVEL
INSTABILITY...AND A CHANCE OF SHOWERS WAS CARRIED WITH THE FRONT TO
THE COAST. BEHIND THE FRONT...THE AIRMASS CHANGE IS SLOW. THERE
COULD EVEN BE SOME PATCHY FOG AHEAD OF THE FRONT IN THE LATE
EVENING...BUT WILL NOT BE MENTIONED YET.
BEHIND THE FRONT...THE LOW LEVEL PUSH COULD ALLOW FOR GUSTY NORTH
WINDS DURING THE EARLY MORNING HOURS. FOR THE MOST PART...BECAUSE OF
THE SLOW AIRMASS CHANGE...LOWS WERE BASED ON A NOS BLEND.
&&
.LONG TERM /THURSDAY THROUGH TUESDAY/...
HIGH PRESSURE CENTERED OVER THE GREAT LAKES WILL GRADUALLY WORK ITS
WAY THROUGH OUR REGION DURING MOST OF THE EXTENDED PERIOD. SKIES
WILL BE MOSTLY CLEAR ALLOWING DAYTIME TEMPERATURES TO CLIMB INTO THE
MID TO UPPER 70S. THE ONLY CAVEAT ONE COULD SEE WOULD BE ON FRIDAY
AND SATURDAY WITH ONSHORE FLOW...WILL BE STRONGER IN THE AFTERNOON
WHEN PEAK HEATING WOULD TAKE PLACE ALLOWING A SEABREEZE TO MOVE
PRETTY FAR INLAND BOTH DAYS.
OTHERWISE, THE RETURN FLOW BEHIND THE DEPARTING HIGH PRESSURE SYSTEM
WILL BRING INCREASED MOISTURE ACROSS THE AREA EARLY NEXT WEEK. THE
UPPER HIGH WILL BE ON THE WANE WITH LOWERING HEIGHTS INDICATED AND A
WEAK LOW ON THE 12Z GFS. AN INCREASED CHC FOR SHOWERS/TSTMS WILL BE
OVER THE REGION THEN. SMALL CHC POPS ARE IN THE FCST FOR NOW
COVERING MON NGT INTO EARLY WED.
&&
.AVIATION /07Z WEDNESDAY THROUGH SUNDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.
CONTENDING WITH THE CONVECTIVE COMPLEX EARLY THIS MORNING NEAR THE
KPHL METRO AIRPORTS. FOR NOW...THE THUNDERSTORMS WILL BE INCLUDED
THROUGH ABOUT 0800 UTC...WITH MAINLY MVFR CONDITIONS WITH CEILINGS
AND VISIBILITY IN HEAVY RAIN.
ELSEWHERE...STARTING TO SEE IFR CONDITIONS IN SOUTHERN NEW JERSEY AT
KACY AND KMIV...AS WELL AS KABE. IT WOULD APPEAR AS THOUGH MOST
PLACES WILL SEE A PERIOD OF MVFR/IFR CONDITIONS THROUGH ABOUT 1300
UTC...AS THE LOW LEVEL MOISTENS ENOUGH FOR LOW CEILINGS. IT IS
POSSIBLE THAT KMIV AND KACY COULD SEE VISIBILITIES DROP BELOW 1SM IN
FOG...BUT LOW CONFIDENCE IN THIS MEANS IT STAYS OUT OF THE FORECAST
OF NOW.
THE LOW CLOUD AND FOG SHOULD BEGIN TO DISSIPATE BETWEEN 1200 UTC AND
1400 UTC...WITH LOW IFR CONDITIONS REMAINING IN PLACE AT KACY THE
LONGEST. AFTER THIS...WEST SOUTHWEST FLOW WILL DEVELOP AHEAD OF A
COLD FRONT. VFR CONDITIONS ARE EXPECTED FOR THE REMAINDER OF THE DAY.
SCATTERED THUNDERSTORMS COULD DEVELOP AHEAD OF THE FRONT LATE THIS
AFTERNOON AND THIS EVENING...MAINLY AFFECTING AREAS NORTH AND EAST
OF KPHL. FOR NOW...THE MENTION OF THUNDER WAS LEFT OUT OF THE
FORECAST...BUT THIS COULD BE REVISITED LATER.
ONCE THE FRONT PASSES LATE THIS EVENING...VFR CONDITIONS ARE
EXPECTED WITH A LIGHT NORTH BREEZE. THERE ARE SOME INDICATIONS THAT
MVFR FOG COULD DEVELOP JUST AHEAD OF THE FRONT IN PLACES LIKE KMIV
AND KACY...BUT THIS CAN BE REEVALUATED WITH THE 1200 UTC FORECASTS.
OUTLOOK...
THURSDAY THROUGH SUNDAY...VFR. A SEABREEZE MAY DEVELOP ON FRIDAY AND
SATURDAY.
&&
.MARINE...
WINDS REMAIN BELOW SMALL CRAFT LEVELS EARLY THIS MORNING...AS THE
THE COASTAL WATERS REMAINS ON THE WESTERN EDGE OF THE GRADIENT
ASSOCIATED WITH THE SURFACE HIGH WELL EAST OF THE WATERS.
HOWEVER...SEAS REMAIN NEAR THE 5 FOOT BENCHMARK FOR A SMALL CRAFT
ADVISORY.
IT IS A TOUGH CALL AS TO HOW LONG SEAS WILL REMAIN NEAR 5 FEET ON
THE OCEAN. THE WNAWAVE GUIDANCE SUGGESTS THAT THIS WILL OCCUR INTO
THIS EVENING...BUT THE 8 SECOND PERIOD SUGGESTS THAT TIME FRAME MAY
BE TOO LONG. FOR NOW...THE SMALL CRAFT ADVISORY WILL BE EXTENDED
INTO THE AFTERNOON...AND TRENDS CAN BE FOLLOWED DURING THE DAY TO
DETERMINE WHEN THE SEAS COULD DROP.
THE SOUTHWEST FLOW AHEAD OF AN APPROACHING COLD FRONT COULD APPROACH
15 KNOTS THIS AFTERNOON AND EVENING...BUT PROBABLY NOT MORE THAN
THAT AS THE WARM BOUNDARY LAYER RUNS OVER THE COOLER WATER. THE BEST
GUSTS SHOULD BE NEARSHORE ON THE OCEAN AND OVER THE DELAWARE BAY.
THE FRONT CROSSES THE AREA LATE THIS EVENING AND EARLY THURSDAY
MORNING. WITH THE FRONTAL PASSAGE...A FEW GUSTS TO 20 KNOTS ARE
POSSIBLE IN THE LOW LEVEL PUSH. AT THIS POINT...IT APPEARS THAT THE
NORTHERLY FLOW WILL REMAIN BELOW SMALL CRAFT LEVELS THROUGH SUNRISE.
OUTLOOK...
WITH HIGH PRESSURE OVER OUR WATERS ON THURSDAY, WE WILL CONTINUE
TO EXPERIENCE TRANQUIL CONDITIONS. WINDS WILL SWING TO THE EAST-
NORTHEAST ON FRIDAY AND REMAIN THERE THROUGH MONDAY.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT EARLY THIS MORNING FOR
ANZ450>455.
&&
$$
SYNOPSIS...HEAVENER
NEAR TERM...HAYES
SHORT TERM...HAYES
LONG TERM...HEAVENER/O`HARA
AVIATION...HAYES/HEAVENER
MARINE...HAYES/HEAVENER
000
FXUS61 KPHI 160534
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
134 AM EDT WED MAY 16 2012
.SYNOPSIS...
A WEAK FRONTAL SYSTEM AND LOW PRESSURE AREA ACROSS THE REGION
TONIGHT WILL REMAIN INTO EARLY WEDNESDAY BEFORE DISSIPATING. ANOTHER
COLD FRONT FROM THE GREAT LAKES WILL CROSS THE AREA LATER WEDNESDAY.
HIGH PRESSURE FROM THE UPPER GREAT LAKES WILL BUILD OVER THE AREA
THURSDAY AND FRIDAY. THE HIGH WILL CREST OVER THE AREA THIS WEEKEND
BEFORE MOVING OFF INTO THE ATLANTIC NEXT MONDAY. A WEAK AREA OF LOW
PRESSURE WILL APPROACH THE AREA DURING THE FIRST PART OF NEXT WEEK.
&&
.NEAR TERM /UNTIL 6 AM THIS MORNING/...
CONVECTION THAT DEVELOPED ON A LINE OF LOW LEVEL CONVERGENCE AHEAD
OF A WEAK SHORT WAVE OVER THE AREA IS STARTING TO WEAKEN. ANY
STRONG CONVECTION HAS MORPHED INTO A LOCALIZED FLOOD THREAT...WITH
PRECIPITABLE WATER VALUES NEAR 1.30 INCHES AND A RELATIVELY SLOW
MOVEMENT.
ANOTHER AREAS OF SHOWERS WITH HEAVY RAIN WILL AFFECT NORTHEAST
MARYLAND AND SOUTHERN AND CENTRAL DELAWARE. THE FORECAST WAS
UPDATED TO HIGHLIGHT THESE AREAS FOR THE NEXT COUPLE OF HOURS.
ALSO LATE THIS EVENING, THE SURFACE HIGH TO THE EAST WAS RIDGING
BACK INTO OUR AREA ENOUGH TO STRENGTHEN STABLE AIR NEAR THE
IMMEDIATE COAST. NAM SURFACE COMPUTED LI VALUES WERE MATCHING
OBSERVED VALUES FAIRLY CLOSELY, AND LOW CLOUDS AND SOME FOG WERE
ASSOCIATED WITH POSITIVE LI VALUES. WE USED THE MODEL`S DEPICTION
OF THE INDEX TO ARRIVE AT AN AREA WHERE LOW CLOUDS AND FOG ARE
FORECAST. AN SPS HAS BEEN ISSUED FOR WHAT BASICALLY IS EASTERN NJ.
TEMPERATURES TONIGHT WERE CHANGED TO ACCOUNT FOR THE MARINE LAYER;
OTHERWISE THEY LOOKED OKAY.
&&
.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM THIS EVENING/...
POTENTIALLY INTERESTING DAY TOMORROW IF A COUPLE OF PIECES CAN
COINCIDE BETTER. FIRST THE GFS WAS NOT USED BECAUSE ITS FORECAST SFC
DEW POINTS ARE TOO HIGH EVEN IF THERE WILL BE A LAG IN THE DROP
OFF. ITS MOS GUIDANCE IS ABOUT 10F LOWER THAN THE MODEL, WHICH MAY
BE A BIT MUCH ON THE OTHER END, BUT BELIEVE IT WILL VERIFY CLOSER.
IN THE CENTRAL AND SOUTHERN PART OF OUR CWA THE FORECAST 850MB AND
925MB WINDS ARE FORECAST TO BE WEST WHICH IS NOT A GOOD DIRECTION
FOR TSRAS TO BECOME ROBUST NEVERTHELESS EVEN FORM. WE SUPPOSE THAT
THERE COULD BE A WINDOW AROUND NOON WHEN DEW POINTS ARE STILL HIGHER
AND THE CONVECTIVE TEMP GETS REACHED. THEN ITS A WAITING GAME IF ANY
OF THE MORE ORGANIZED CONVECTION CAN GET HERE BEFORE DOWNSLOPING AND
A WESTERLY FLOW TAKES ITS TOLL. SUFFICE POPS WERE KEPT EITHER SLGT
CHC OR LOW CHANCE.
UP NORTH LATE IN THE AFTERNOON MIGHT BE MORE INTERESTING. UP THERE
BETTER FORECAST SHEAR, MORE OF A SW WIND FLOW AT 850MB AND 925MB,
THE ENTRANCE REGION OF THE 250MB JET MIGHT BE ABLE TO OVERCOME
DECREASING MOISTURE DURING THE AFTERNOON. WHILE IT IS FORECAST TO BE
DRIER ITS NOT THAT DRY. PLUS ALL OF THE FORECAST SOUNDINGS SHOWING
PLENTY OF DOWNDRAFT CAPE AND DRY AIR AT MID LEVELS WELL WITHING
PULSE SEVERE TSRA LEVELS. THE MESOSCALE CONVECTIVE MODELS OVERALL
FAVOR PLACES FARTHER TO THE NORTHEAST, BUT ITS TOUGH TO DRAW THAT
LINE IN THE SAND THIS EARLY. WHILE WE WILL NOT CARRY ENHANCED
WORDING BECAUSE OF LOW POPS, WE DID KEEP MENTION IN THE HWO IN LINE
WITH SPC`S CHANCES WITH US FAVORING THE POCONOS AND FAR NORTH NJ IF
THE MORE ROBUST STORMS CAN MAKE IT.
GIVEN THE WESTERLY FLOW AND UNANIMOUS FORECAST 925MB TEMPS, WE
UPPED MAX TEMPS UPWARD. SLIGHTLY LOWER THAN STAT GUIDANCE BECAUSE OF
THE FORMER AND THE HEAVIER RAIN OF THE PAST 24 TO 36 HOURS.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
MUCH OF THE EXTENDED PART OF THE FORECAST WILL FEATURE FAIR WEATHER
AS HIGH PRESSURE ALOFT AND AT THE SFC WORKS ITS WAY ACROSS THE
REGION. WEDNESDAY NIGHT...THERE WILL BE A FEW LINGERING SHOWERS AND
TSTMS ACROSS THE NJ/DE AREA AS THE SFC COLD FRONT CROSSES THE AREA.
DRIER AND COOLER AIR WILL ARRIVE FOR EARLY THU WITH OVERNIGHT LOWS
THU IN THE LOW TO MID 40S ACROSS THE NRN AREAS AND UPPER 40S TO LOW
50S OVER THE REST OF THE AREA.
UNDER MOSTLY SUNNY SKIES EACH DAY THU-SUN TEMPERATURES WILL RISE
INTO THE 70S OVER MOST AREAS WITH READINGS COOLER ACROSS THE SRN
POCONOS AND ALONG THE IMMEDIATE SHORELINE. OVERNIGHT LOWS WILL
MOSTLY BE IN THE 40S AND LOW 50S FRI MORNING AND IN THE 50S
REGION-WIDE SAT AND SUN MORNING.
THE RETURN FLOW BEHIND THE DEPARTING HIGH PRESSURE SYSTEM WILL BRING
INCREASED MOISTURE ACROSS THE AREA EARLY NEXT WEEK. THE UPPER HIGH
WILL BE ON THE WANE WITH LOWERING HEIGHTS INDICATED AND A WEAK LOW ON
THE 12Z GFS. AN INCREASED CHC FOR SHOWERS/TSTMS WILL BE OVER THE
REGION THEN. SMALL CHC POPS ARE IN THE FCST FOR NOW COVERING MON NGT
INTO EARLY WED.
&&
.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.
CONTENDING WITH THE CONVECTIVE COMPLEX EARLY THIS MORNING NEAR THE
KPHL METRO AIRPORTS. FOR NOW...THE THUNDERSTORMS WILL BE INCLUDED
THROUGH ABOUT 0800 UTC...WITH MAINLY MVFR CONDITIONS WITH CEILINGS
AND VISIBILITY IN HEAVY RAIN.
ELSEWHERE...STARTING TO SEE IFR CONDITIONS IN SOUTHERN NEW JERSEY AT
KACY AND KMIV...AS WELL AS KABE. IT WOULD APPEAR AS THOUGH MOST
PLACES WILL SEE A PERIOD OF MVFR/IFR CONDITIONS THROUGH ABOUT 1300
UTC...AS THE LOW LEVEL MOISTENS ENOUGH FOR LOW CEILINGS. IT IS
POSSIBLE THAT KMIV AND KACY COULD SEE VISIBILITIES DROP BELOW 1SM IN
FOG...BUT LOW CONFIDENCE IN THIS MEANS IT STAYS OUT OF THE FORECAST
OF NOW.
THE LOW CLOUD AND FOG SHOULD BEGIN TO DISSIPATE BETWEEN 1200 UTC AND
1400 UTC...WITH LOW IFR CONDITIONS REMAINING IN PLACE AT KACY THE
LONGEST. AFTER THIS...WEST SOUTHWEST FLOW WILL DEVELOP AHEAD OF A
COLD FRONT. VFR CONDITIONS ARE EXPECTED FOR THE REMAINDER OF THE DAY.
SCATTERED THUNDERSTORMS COULD DEVELOP AHEAD OF THE FRONT LATE THIS
AFTERNOON AND THIS EVENING...MAINLY AFFECTING AREAS NORTH AND EAST
OF KPHL. FOR NOW...THE MENTION OF THUNDER WAS LEFT OUT OF THE
FORECAST...BUT THIS COULD BE REVISITED LATER.
ONCE THE FRONT PASSES LATE THIS EVENING...VFR CONDITIONS ARE
EXPECTED WITH A LIGHT NORTH BREEZE. THERE ARE SOME INDICATIONS THAT
MVFR FOG COULD DEVELOP JUST AHEAD OF THE FRONT IN PLACES LIKE KMIV
AND KACY...BUT THIS CAN BE REEVALUATED WITH THE 1200 UTC FORECASTS.
OUTLOOK...
THU-SUN...VFR. PATCHY FOG POSSIBLE BEFORE DAWN FRI.
&&
.MARINE...
WE WILL LEAVE THE SCA MAINLY FOR SEAS UP THROUGH TONIGHT. THE SCA
SWELLS HAVE REACHED ALL WATERS. WE ALSO HAVE ADDED FOG TO THE
FORECAST, AND WE MAINTAIN THE POSSIBILITY OF SHOWERS/TSTMS
(ALTHOUGH WE BELIEVE ANY TSTMS WOULD BE WEAKENING AND ELEVATED).
BECAUSE WE HAD SUCH A HARD TIME REACHING THE SCA CRITERIA AND
WAVEWATCH IS NOW BACKING OFF ON SEAS ON WEDNESDAY, WE WILL NOT
EXTEND THE ADVISORY PAST TONIGHT WITH THIS PACKAGE. MOST OF THE
FORECAST FIVE FOOT SEAS ARE FORECAST TO BE NEAR THE EASTERN EDGE
OF OUR COASTAL WATERS. OTHERWISE, OUTSIDE OF ANY TSTMS, SOUTHERLY
WINDS ARE NOT EXPECTED TO REACH SMALL CRAFT ADVISORY CONDITIONS.
OUTLOOK...
HIGH PRESSURE WILL BUILD OVER THE WATERS WITH SUB-SCA CONDITIONS
EXPECTED FOR THE REGION WED NIGHT-SUN.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT EARLY THIS MORNING FOR
ANZ450>455.
&&
$$
SYNOPSIS...O`HARA
NEAR TERM...GIGI/HAYES
SHORT TERM...GIGI
LONG TERM...O`HARA
AVIATION...HAYES/O`HARA
MARINE...GIGI
000
FXUS61 KPHI 160338
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1138 PM EDT TUE MAY 15 2012
.SYNOPSIS...
A WEAK FRONTAL SYSTEM AND LOW PRESSURE AREA ACROSS THE REGION
TONIGHT WILL REMAIN INTO EARLY WEDNESDAY BEFORE DISSIPATING. ANOTHER
COLD FRONT FROM THE GREAT LAKES WILL CROSS THE AREA LATER WEDNESDAY.
HIGH PRESSURE FROM THE UPPER GREAT LAKES WILL BUILD OVER THE AREA
THURSDAY AND FRIDAY. THE HIGH WILL CREST OVER THE AREA THIS WEEKEND
BEFORE MOVING OFF INTO THE ATLANTIC NEXT MONDAY. A WEAK AREA OF LOW
PRESSURE WILL APPROACH THE AREA DURING THE FIRST PART OF NEXT WEEK.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
CONVECTION THAT DEVELOPED ON A LINE OF LOW LEVEL CONVERGENCE AHEAD
OF A WEAK SHORT WAVE OVER THE AREA IS STARTING TO WEAKEN. ANY
STRONG CONVECTION HAS MORPHED INTO A LOCALIZED FLOOD THREAT...WITH
PRECIPITABLE WATER VALUES NEAR 1.30 INCHES AND A RELATIVELY SLOW
MOVEMENT.
ANOTHER AREAS OF SHOWERS WITH HEAVY RAIN WILL AFFECT NORTHEAST
MARYLAND AND SOUTHERN AND CENTRAL DELAWARE. THE FORECAST WAS
UPDATED TO HIGHLIGHT THESE AREAS FOR THE NEXT COUPLE OF HOURS.
ALSO LATE THIS EVENING, THE SURFACE HIGH TO THE EAST WAS RIDGING
BACK INTO OUR AREA ENOUGH TO STRENGTHEN STABLE AIR NEAR THE
IMMEDIATE COAST. NAM SURFACE COMPUTED LI VALUES WERE MATCHING
OBSERVED VALUES FAIRLY CLOSELY, AND LOW CLOUDS AND SOME FOG WERE
ASSOCIATED WITH POSITIVE LI VALUES. WE USED THE MODEL`S DEPICTION
OF THE INDEX TO ARRIVE AT AN AREA WHERE LOW CLOUDS AND FOG ARE
FORECAST. AN SPS HAS BEEN ISSUED FOR WHAT BASICALLY IS EASTERN NJ.
TEMPERATURES TONIGHT WERE CHANGED TO ACCOUNT FOR THE MARINE LAYER;
OTHERWISE THEY LOOKED OKAY.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
POTENTIALLY INTERESTING DAY TOMORROW IF A COUPLE OF PIECES CAN
COINCIDE BETTER. FIRST THE GFS WAS NOT USED BECAUSE ITS FORECAST SFC
DEW POINTS ARE TOO HIGH EVEN IF THERE WILL BE A LAG IN THE DROP
OFF. ITS MOS GUIDANCE IS ABOUT 10F LOWER THAN THE MODEL, WHICH MAY
BE A BIT MUCH ON THE OTHER END, BUT BELIEVE IT WILL VERIFY CLOSER.
IN THE CENTRAL AND SOUTHERN PART OF OUR CWA THE FORECAST 850MB AND
925MB WINDS ARE FORECAST TO BE WEST WHICH IS NOT A GOOD DIRECTION
FOR TSRAS TO BECOME ROBUST NEVERTHELESS EVEN FORM. WE SUPPOSE THAT
THERE COULD BE A WINDOW AROUND NOON WHEN DEW POINTS ARE STILL HIGHER
AND THE CONVECTIVE TEMP GETS REACHED. THEN ITS A WAITING GAME IF ANY
OF THE MORE ORGANIZED CONVECTION CAN GET HERE BEFORE DOWNSLOPING AND
A WESTERLY FLOW TAKES ITS TOLL. SUFFICE POPS WERE KEPT EITHER SLGT
CHC OR LOW CHANCE.
UP NORTH LATE IN THE AFTERNOON MIGHT BE MORE INTERESTING. UP THERE
BETTER FORECAST SHEAR, MORE OF A SW WIND FLOW AT 850MB AND 925MB,
THE ENTRANCE REGION OF THE 250MB JET MIGHT BE ABLE TO OVERCOME
DECREASING MOISTURE DURING THE AFTERNOON. WHILE IT IS FORECAST TO BE
DRIER ITS NOT THAT DRY. PLUS ALL OF THE FORECAST SOUNDINGS SHOWING
PLENTY OF DOWNDRAFT CAPE AND DRY AIR AT MID LEVELS WELL WITHING
PULSE SEVERE TSRA LEVELS. THE MESOSCALE CONVECTIVE MODELS OVERALL
FAVOR PLACES FARTHER TO THE NORTHEAST, BUT ITS TOUGH TO DRAW THAT
LINE IN THE SAND THIS EARLY. WHILE WE WILL NOT CARRY ENHANCED
WORDING BECAUSE OF LOW POPS, WE DID KEEP MENTION IN THE HWO IN LINE
WITH SPC`S CHANCES WITH US FAVORING THE POCONOS AND FAR NORTH NJ IF
THE MORE ROBUST STORMS CAN MAKE IT.
GIVEN THE WESTERLY FLOW AND UNANIMOUS FORECAST 925MB TEMPS, WE
UPPED MAX TEMPS UPWARD. SLIGHTLY LOWER THAN STAT GUIDANCE BECAUSE OF
THE FORMER AND THE HEAVIER RAIN OF THE PAST 24 TO 36 HOURS.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
MUCH OF THE EXTENDED PART OF THE FORECAST WILL FEATURE FAIR WEATHER
AS HIGH PRESSURE ALOFT AND AT THE SFC WORKS ITS WAY ACROSS THE
REGION. WEDNESDAY NIGHT...THERE WILL BE A FEW LINGERING SHOWERS AND
TSTMS ACROSS THE NJ/DE AREA AS THE SFC COLD FRONT CROSSES THE AREA.
DRIER AND COOLER AIR WILL ARRIVE FOR EARLY THU WITH OVERNIGHT LOWS
THU IN THE LOW TO MID 40S ACROSS THE NRN AREAS AND UPPER 40S TO LOW
50S OVER THE REST OF THE AREA.
UNDER MOSTLY SUNNY SKIES EACH DAY THU-SUN TEMPERATURES WILL RISE
INTO THE 70S OVER MOST AREAS WITH READINGS COOLER ACROSS THE SRN
POCONOS AND ALONG THE IMMEDIATE SHORELINE. OVERNIGHT LOWS WILL
MOSTLY BE IN THE 40S AND LOW 50S FRI MORNING AND IN THE 50S
REGION-WIDE SAT AND SUN MORNING.
THE RETURN FLOW BEHIND THE DEPARTING HIGH PRESSURE SYSTEM WILL BRING
INCREASED MOISTURE ACROSS THE AREA EARLY NEXT WEEK. THE UPPER HIGH
WILL BE ON THE WANE WITH LOWERING HEIGHTS INDICATED AND A WEAK LOW ON
THE 12Z GFS. AN INCREASED CHC FOR SHOWERS/TSTMS WILL BE OVER THE
REGION THEN. SMALL CHC POPS ARE IN THE FCST FOR NOW COVERING MON NGT
INTO EARLY WED.
&&
.AVIATION /04Z WEDNESDAY THROUGH SUNDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.
WE ARE CONTINUING THE TREND TOWARD MVFR/IFR CONDITIONS LATE THIS
EVENING AND OVERNIGHT WITH THE WORST CONDITIONS FORECAST EAST.
FORECAST SOUNDINGS ARE PRETTY MOIST TOWARD THE GROUND AND WITH
LIGHT WINDS, WE DO FORECAST AN IFR CIG WITH SOME IFR VSBYS AT OUR
FOGGIER OUTLYING TERMINALS.
WITH WEST WINDS FORECAST TO OCCUR ON WEDNESDAY MORNING, WE BRING VFR
CONDITIONS RAPIDLY TO ALL THE TERMINALS BY THE MIDDLE OF THE
MORNING. WHILE THERE SHOULD BE SOME WIDELY SCATTERED CONVECTION
AROUND, THE COVERAGE IS TOO LOW TO INCLUDE IN THE TAFS AT THIS TIME.
BEST CHANCE NORTHERN TERMINALS AND AIRPORTS.
OUTLOOK...
WED NIGHT...SCATTERED SHOWERS DIMINISHING WITH MOSTLY VFR CONDITIONS
BEHIND A DEPARTING FRONT. PATCHY FOG IS POSSIBLE THU BEFORE DAWN
IF THE ARRIVING DRY AIR DOESN`T MIX DOWN FULLY OVERNIGHT.
THU-SUN...VFR. PATCHY FOG POSSIBLE BEFORE DAWN FRI.
&&
.MARINE...
WE WILL LEAVE THE SCA MAINLY FOR SEAS UP THROUGH TONIGHT. THE SCA
SWELLS HAVE REACHED ALL WATERS. WE ALSO HAVE ADDED FOG TO THE
FORECAST, AND WE MAINTAIN THE POSSIBILITY OF SHOWERS/TSTMS
(ALTHOUGH WE BELIEVE ANY TSTMS WOULD BE WEAKENING AND ELEVATED).
BECAUSE WE HAD SUCH A HARD TIME REACHING THE SCA CRITERIA AND
WAVEWATCH IS NOW BACKING OFF ON SEAS ON WEDNESDAY, WE WILL NOT
EXTEND THE ADVISORY PAST TONIGHT WITH THIS PACKAGE. MOST OF THE
FORECAST FIVE FOOT SEAS ARE FORECAST TO BE NEAR THE EASTERN EDGE
OF OUR COASTAL WATERS. OTHERWISE, OUTSIDE OF ANY TSTMS, SOUTHERLY
WINDS ARE NOT EXPECTED TO REACH SMALL CRAFT ADVISORY CONDITIONS.
OUTLOOK...
HIGH PRESSURE WILL BUILD OVER THE WATERS WITH SUB-SCA CONDITIONS
EXPECTED FOR THE REGION WED NIGHT-SUN.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT WEDNESDAY FOR ANZ450>455.
&&
$$
SYNOPSIS...O`HARA
NEAR TERM...GIGI/HAYES
SHORT TERM...GIGI
LONG TERM...O`HARA
AVIATION...GIGI
MARINE...GIGI
000
FXUS61 KPHI 160159
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
959 PM EDT TUE MAY 15 2012
.SYNOPSIS...
A WEAK FRONTAL SYSTEM AND LOW PRESSURE AREA ACROSS THE REGION
TONIGHT WILL REMAIN INTO EARLY WEDNESDAY BEFORE DISSIPATING. ANOTHER
COLD FRONT FROM THE GREAT LAKES WILL CROSS THE AREA LATER WEDNESDAY.
HIGH PRESSURE FROM THE UPPER GREAT LAKES WILL BUILD OVER THE AREA
THURSDAY AND FRIDAY. THE HIGH WILL CREST OVER THE AREA THIS WEEKEND
BEFORE MOVING OFF INTO THE ATLANTIC NEXT MONDAY. A WEAK AREA OF LOW
PRESSURE WILL APPROACH THE AREA DURING THE FIRST PART OF NEXT WEEK.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
LATE THIS EVENING, AN IMPULSE WAS APPROACHING FROM THE SOUTHWEST
AND WAS TAPPING DECENT INSTABILITY AND MOISTURE. THIS WAS
RESULTING IN CONVECTION FROM NORTH CENTRAL NEW JERSEY TO THE
MARYLAND WESTERN SHORE. WE THINK THIS ALL WILL LOSE SOME STRENGTH
OVERNIGHT, BUT THROUGH MIDNIGHT WE`VE INCREASED POPS AND PUT IN
THE MENTION OF POSSIBLE HEAVY RAIN MAINLY SOUTHWEST.
ALSO LATE THIS EVENING, THE SURFACE HIGH TO THE EAST WAS RIDGING
BACK INTO OUR AREA ENOUGH TO STRENGTHEN STABLE AIR NEAR THE
IMMEDIATE COAST. NAM SURFACE COMPUTED LI VALUES WERE MATCHING
OBSERVED VALUES FAIRLY CLOSELY, AND LOW CLOUDS AND SOME FOG WERE
ASSOCIATED WITH POSITIVE LI VALUES. WE USED THE MODEL`S DEPICTION
OF THE INDEX TO ARRIVE AT AN AREA WHERE LOW CLOUDS AND FOG ARE
FORECAST. AN SPS HAS BEEN ISSUED FOR WHAT BASICALLY IS EASTERN NJ.
TEMPERATURES TONIGHT WERE CHANGED TO ACCOUNT FOR THE MARINE LAYER;
OTHERWISE THEY LOOKED OKAY.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
POTENTIALLY INTERESTING DAY TOMORROW IF A COUPLE OF PIECES CAN
COINCIDE BETTER. FIRST THE GFS WAS NOT USED BECAUSE ITS FORECAST SFC
DEW POINTS ARE TOO HIGH EVEN IF THERE WILL BE A LAG IN THE DROP
OFF. ITS MOS GUIDANCE IS ABOUT 10F LOWER THAN THE MODEL, WHICH MAY
BE A BIT MUCH ON THE OTHER END, BUT BELIEVE IT WILL VERIFY CLOSER.
IN THE CENTRAL AND SOUTHERN PART OF OUR CWA THE FORECAST 850MB AND
925MB WINDS ARE FORECAST TO BE WEST WHICH IS NOT A GOOD DIRECTION
FOR TSRAS TO BECOME ROBUST NEVERTHELESS EVEN FORM. WE SUPPOSE THAT
THERE COULD BE A WINDOW AROUND NOON WHEN DEW POINTS ARE STILL HIGHER
AND THE CONVECTIVE TEMP GETS REACHED. THEN ITS A WAITING GAME IF ANY
OF THE MORE ORGANIZED CONVECTION CAN GET HERE BEFORE DOWNSLOPING AND
A WESTERLY FLOW TAKES ITS TOLL. SUFFICE POPS WERE KEPT EITHER SLGT
CHC OR LOW CHANCE.
UP NORTH LATE IN THE AFTERNOON MIGHT BE MORE INTERESTING. UP THERE
BETTER FORECAST SHEAR, MORE OF A SW WIND FLOW AT 850MB AND 925MB,
THE ENTRANCE REGION OF THE 250MB JET MIGHT BE ABLE TO OVERCOME
DECREASING MOISTURE DURING THE AFTERNOON. WHILE IT IS FORECAST TO BE
DRIER ITS NOT THAT DRY. PLUS ALL OF THE FORECAST SOUNDINGS SHOWING
PLENTY OF DOWNDRAFT CAPE AND DRY AIR AT MID LEVELS WELL WITHING
PULSE SEVERE TSRA LEVELS. THE MESOSCALE CONVECTIVE MODELS OVERALL
FAVOR PLACES FARTHER TO THE NORTHEAST, BUT ITS TOUGH TO DRAW THAT
LINE IN THE SAND THIS EARLY. WHILE WE WILL NOT CARRY ENHANCED
WORDING BECAUSE OF LOW POPS, WE DID KEEP MENTION IN THE HWO IN LINE
WITH SPC`S CHANCES WITH US FAVORING THE POCONOS AND FAR NORTH NJ IF
THE MORE ROBUST STORMS CAN MAKE IT.
GIVEN THE WESTERLY FLOW AND UNANIMOUS FORECAST 925MB TEMPS, WE
UPPED MAX TEMPS UPWARD. SLIGHTLY LOWER THAN STAT GUIDANCE BECAUSE OF
THE FORMER AND THE HEAVIER RAIN OF THE PAST 24 TO 36 HOURS.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
MUCH OF THE EXTENDED PART OF THE FORECAST WILL FEATURE FAIR WEATHER
AS HIGH PRESSURE ALOFT AND AT THE SFC WORKS ITS WAY ACROSS THE
REGION. WEDNESDAY NIGHT...THERE WILL BE A FEW LINGERING SHOWERS AND
TSTMS ACROSS THE NJ/DE AREA AS THE SFC COLD FRONT CROSSES THE AREA.
DRIER AND COOLER AIR WILL ARRIVE FOR EARLY THU WITH OVERNIGHT LOWS
THU IN THE LOW TO MID 40S ACROSS THE NRN AREAS AND UPPER 40S TO LOW
50S OVER THE REST OF THE AREA.
UNDER MOSTLY SUNNY SKIES EACH DAY THU-SUN TEMPERATURES WILL RISE
INTO THE 70S OVER MOST AREAS WITH READINGS COOLER ACROSS THE SRN
POCONOS AND ALONG THE IMMEDIATE SHORELINE. OVERNIGHT LOWS WILL
MOSTLY BE IN THE 40S AND LOW 50S FRI MORNING AND IN THE 50S
REGION-WIDE SAT AND SUN MORNING.
THE RETURN FLOW BEHIND THE DEPARTING HIGH PRESSURE SYSTEM WILL BRING
INCREASED MOISTURE ACROSS THE AREA EARLY NEXT WEEK. THE UPPER HIGH
WILL BE ON THE WANE WITH LOWERING HEIGHTS INDICATED AND A WEAK LOW ON
THE 12Z GFS. AN INCREASED CHC FOR SHOWERS/TSTMS WILL BE OVER THE
REGION THEN. SMALL CHC POPS ARE IN THE FCST FOR NOW COVERING MON NGT
INTO EARLY WED.
&&
.AVIATION /02Z WEDNESDAY THROUGH SUNDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.
WE ARE CONTINUING THE TREND TOWARD MFVR/IFR CONDITIONS LATE THIS
EVENING AND OVERNIGHT WITH THE WORST CONDITIONS FORECAST EAST.
FORECAST SOUNDINGS ARE PRETTY MOIST TOWARD THE GROUND AND WITH
LIGHT WINDS, WE DO FORECAST AN IFR CIG WITH SOME IFR VSBYS AT OUR
FOGGIER OUTLYING TERMINALS.
WITH WEST WINDS FORECAST TO OCCUR ON WEDNESDAY MORNING, WE BRING VFR
CONDITIONS RAPIDLY TO ALL THE TERMINALS BY THE MIDDLE OF THE
MORNING. WHILE THERE SHOULD BE SOME WIDELY SCATTERED CONVECTION
AROUND, THE COVERAGE IS TOO LOW TO INCLUDE IN THE TAFS AT THIS TIME.
BEST CHANCE NORTHERN TERMINALS AND AIRPORTS.
OUTLOOK...
WED NIGHT...SCATTERED SHOWERS DIMINISHING WITH MOSTLY VFR CONDITIONS
BEHIND A DEPARTING FRONT. PATCHY FOG IS POSSIBLE THU BEFORE DAWN
IF THE ARRIVING DRY AIR DOESN`T MIX DOWN FULLY OVERNIGHT.
THU-SUN...VFR. PATCHY FOG POSSIBLE BEFORE DAWN FRI.
&&
.MARINE...
WE WILL LEAVE THE SCA MAINLY FOR SEAS UP THROUGH TONIGHT. THE SCA
SWELLS HAVE REACHED ALL WATERS. WE ALSO HAVE ADDED FOG TO THE
FORECAST, AND WE MAINTAIN THE POSSIBILITY OF SHOWERS/TSTMS
(ALTHOUGH WE BELIEVE ANY TSTMS WOULD BE WEAKENING AND ELEVATED).
BECAUSE WE HAD SUCH A HARD TIME REACHING THE SCA CRITERIA AND
WAVEWATCH IS NOW BACKING OFF ON SEAS ON WEDNESDAY, WE WILL NOT
EXTEND THE ADVISORY PAST TONIGHT WITH THIS PACKAGE. MOST OF THE
FORECAST FIVE FOOT SEAS ARE FORECAST TO BE NEAR THE EASTERN EDGE
OF OUR COASTAL WATERS. OTHERWISE, OUTSIDE OF ANY TSTMS, SOUTHERLY
WINDS ARE NOT EXPECTED TO REACH SMALL CRAFT ADVISORY CONDITIONS.
OUTLOOK...
HIGH PRESSURE WILL BUILD OVER THE WATERS WITH SUB-SCA CONDITIONS
EXPECTED FOR THE REGION WED NIGHT-SUN.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT WEDNESDAY FOR ANZ450>455.
&&
$$
SYNOPSIS...O`HARA
NEAR TERM...GIGI/DELISI
SHORT TERM...GIGI
LONG TERM...O`HARA
AVIATION...GIGI/DELISI
MARINE...GIGI/DELISI
000
FXUS61 KPHI 151933
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
333 PM EDT TUE MAY 15 2012
.SYNOPSIS...
A WEAK FRONTAL SYSTEM AND LOW PRESSURE AREA ACROSS THE REGION
TONIGHT WILL REMAIN INTO EARLY WEDNESDAY BEFORE DISSIPATING. ANOTHER
COLD FRONT FROM THE GREAT LAKES WILL CROSS THE AREA LATER WEDNESDAY.
HIGH PRESSURE FROM THE UPPER GREAT LAKES WILL BUILD OVER THE AREA
THURSDAY AND FRIDAY. THE HIGH WILL CREST OVER THE AREA THIS WEEKEND
BEFORE MOVING OFF INTO THE ATLANTIC NEXT MONDAY. A WEAK AREA OF LOW
PRESSURE WILL APPROACH THE AREA DURING THE FIRST PART OF NEXT WEEK.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
THE GFS INITIALIZATION HAS NEVER BEEN ABLE TO OUTDO THE WRF-NMM WITH
THIS CENTRAL AND EASTERN TROF AND THE SAME TODAY. THUS WE HAVE
LEANED MORE TOWARD THE WRF-NMMB SOLUTION THAN THE GFS THRU THE SHORT
TERM.
GAZING AT THE MESOSCALE MODELING FOR TONIGHT, THE TWO FOCI FOR
BETTER ORGANIZED SHORTWAVE SUPPORTED CONVECTION ARE NEAR THE VA AND
NC COAST AND OVER THE CENTRAL APPALACHIANS WHERE DIFFERENTIAL
HEATING AND UPSLOPE FLOW HAS HELPED INITIATE PCPN. IN PA THERE WILL
BE SOME SHORT WAVES THAT MAY PROLONG THE CONVECTION, BUT OVERALL THE
TREND THROUGH THE NIGHT SHOULD BE DOWNWARD WITH LESS OVERALL
COVERAGE.
GIVEN THE FORECAST SOUNDINGS ARE PRETTY MOIST NEAR THE SURFACE WITH
NOT MUCH MIXING OF EVENTUAL DRIER AIR ALOFT, WE ARE EXPECTING LOW
CLOUDS AND OR FOG TO FORM. RIGHT NOW WE ARE THINKING THE FOG WILL
HAVE MORE OF AN AVIATION THAN A PUBLIC IMPACT AND HAVE NOT INCLUDED
ANY NOTEWORTHY FOG IN THE GRIDS. IN CONJUNCTION WITH THIS WE ARE
OPTING TO GO WITH THE MILDER STAT GUIDANCE FOR MINS.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
POTENTIALLY INTERESTING DAY TOMORROW IF A COUPLE OF PIECES CAN
COINCIDE BETTER. FIRST THE GFS WAS NOT USED BECAUSE ITS FORECAST SFC
DEW POINTS ARE TOO HIGH EVEN IF THERE WILL BE A LAG IN THE DROP
OFF. ITS MOS GUIDANCE IS ABOUT 10F LOWER THAN THE MODEL, WHICH MAY
BE A BIT MUCH ON THE OTHER END, BUT BELIEVE IT WILL VERIFY CLOSER.
IN THE CENTRAL AND SOUTHERN PART OF OUR CWA THE FORECAST 850MB AND
925MB WINDS ARE FORECAST TO BE WEST WHICH IS NOT A GOOD DIRECTION
FOR TSRAS TO BECOME ROBUST NEVERTHELESS EVEN FORM. WE SUPPOSE THAT
THERE COULD BE A WINDOW AROUND NOON WHEN DEW POINTS ARE STILL HIGHER
AND THE CONVECTIVE TEMP GETS REACHED. THEN ITS A WAITING GAME IF ANY
OF THE MORE ORGANIZED CONVECTION CAN GET HERE BEFORE DOWNSLOPING AND
A WESTERLY FLOW TAKES ITS TOLL. SUFFICE POPS WERE KEPT EITHER SLGT
CHC OR LOW CHANCE.
UP NORTH LATE IN THE AFTERNOON MIGHT BE MORE INTERESTING. UP THERE
BETTER FORECAST SHEAR, MORE OF A SW WIND FLOW AT 850MB AND 925MB,
THE ENTRANCE REGION OF THE 250MB JET MIGHT BE ABLE TO OVERCOME
DECREASING MOISTURE DURING THE AFTERNOON. WHILE IT IS FORECAST TO BE
DRIER ITS NOT THAT DRY. PLUS ALL OF THE FORECAST SOUNDINGS SHOWING
PLENTY OF DOWNDRAFT CAPE AND DRY AIR AT MID LEVELS WELL WITHING
PULSE SEVERE TSRA LEVELS. THE MESOSCALE CONVECTIVE MODELS OVERALL
FAVOR PLACES FARTHER TO THE NORTHEAST, BUT ITS TOUGH TO DRAW THAT
LINE IN THE SAND THIS EARLY. WHILE WE WILL NOT CARRY ENHANCED
WORDING BECAUSE OF LOW POPS, WE DID KEEP MENTION IN THE HWO IN LINE
WITH SPC`S CHANCES WITH US FAVORING THE POCONOS AND FAR NORTH NJ IF
THE MORE ROBUST STORMS CAN MAKE IT.
GIVEN THE WESTERLY FLOW AND UNANIMOUS FORECAST 925MB TEMPS, WE
UPPED MAX TEMPS UPWARD. SLIGHTLY LOWER THAN STAT GUIDANCE BECAUSE OF
THE FORMER AND THE HEAVIER RAIN OF THE PAST 24 TO 36 HOURS.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
MUCH OF THE EXTENDED PART OF THE FORECAST WILL FEATURE FAIR WEATHER
AS HIGH PRESSURE ALOFT AND AT THE SFC WORKS ITS WAY ACROSS THE
REGION. WEDNESDAY NIGHT...THERE WILL BE A FEW LINGERING SHOWERS AND
TSTMS ACROSS THE NJ/DE AREA AS THE SFC COLD FRONT CROSSES THE AREA.
DRIER AND COOLER AIR WILL ARRIVE FOR EARLY THU WITH OVERNIGHT LOWS
THU IN THE LOW TO MID 40S ACROSS THE NRN AREAS AND UPPER 40S TO LOW
50S OVER THE REST OF THE AREA.
UNDER MOSTLY SUNNY SKIES EACH DAY THU-SUN TEMPERATURES WILL RISE
INTO THE 70S OVER MOST AREAS WITH READINGS COOLER ACROSS THE SRN
POCONOS AND ALONG THE IMMEDIATE SHORELINE. OVERNIGHT LOWS WILL
MOSTLY BE IN THE 40S AND LOW 50S FRI MORNING AND IN THE 50S
REGION-WIDE SAT AND SUN MORNING.
THE RETURN FLOW BEHIND THE DEPARTING HIGH PRESSURE SYSTEM WILL BRING
INCREASED MOISTURE ACROSS THE AREA EARLY NEXT WEEK. THE UPPER HIGH
WILL BE ON THE WANE WITH LOWERING HEIGHTS INDICATED AND A WEAK LOW ON
THE 12Z GFS. AN INCREASED CHC FOR SHOWERS/TSTMS WILL BE OVER THE
REGION THEN. SMALL CHC POPS ARE IN THE FCST FOR NOW COVERING MON NGT
INTO EARLY WED.
&&
.AVIATION /19Z TUESDAY THROUGH SUNDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.
WE ARE SEEING IMPROVING CONDITIONS TO VFR THIS AFTERNOON AS ALL
AIRPORTS HAVE LOST THE IFR CIGS. NOT CONFIDENT WE WILL LOSE ALL
MVFR CIGS AS THE TEMPERATURE AND DEW POINT SPREADS ARE NOT THAT
LARGE. THERE WILL BE SCATTERED CONVECTION (TSTMS) AROUND THIS
AFTERNOON MAINLY WEST AND SOUTH OF ALL OUR TERMINALS. SO THE LEAST
CONFIDENT TAF SITES AT AVOIDING THEM ARE KRDG AND KACY. WINDS
OVERALL SHOULD BE LIGHT FROM THE SOUTH. WE HAVE AMENDED THE KRDG
TAF TO INCLUDE THUNDER.
WE ARE CONTINUING THE TREND TOWARD IFR CONDITIONS LATE THIS
EVENING AND OVERNIGHT. FORECAST SOUNDINGS ARE PRETTY MOIST TOWARD
THE GROUND AND WITH LIGHT WINDS, WE DO FORECAST AN IFR CIG WITH
SOME IFR VSBYS AT OUR FOGGIER OUTLYING TERMINALS.
WITH WEST WINDS FORECAST TO OCCUR ON WEDNESDAY MORNING, WE BRING VFR
CONDITIONS RAPIDLY TO ALL THE TERMINALS BY THE MIDDLE OF THE
MORNING. WHILE THERE SHOULD BE SOME WIDELY SCATTERED CONVECTION
AROUND, THE COVERAGE IS TOO LOW TO INCLUDE IN THE TAFS AT THIS TIME.
BEST CHANCE NORTHERN TERMINALS AND AIRPORTS.
OUTLOOK...
WED NIGHT...SCATTERED SHOWERS DIMINISHING WITH MOSTLY VFR CONDITIONS
BEHIND A DEPARTING FRONT. PATCHY FOG IS POSSIBLE THU BEFORE DAWN
IF THE ARRIVING DRY AIR DOESN`T MIX DOWN FULLY OVERNIGHT.
THU-SUN...VFR. PATCHY FOG POSSIBLE BEFORE DAWN FRI.
&&
.MARINE...
WE WILL LEAVE THE SCA MAINLY FOR SEAS UP THROUGH TONIGHT. THE SCA
SWELLS HAVE REACHED OUR SOUTHERN WATERS, BUT NOT OUR NORTHERN WATERS
YET. WAVEWATCH HAS BEEN TOO BULLISH WITH THE SWELLS, BUT THE
SOUTHERLY WIND DIRECTION IS EXPECTED TO PERSIST AT NEAR SMALL CRAFT
ADVISORY SPEEDS INTO THIS EVENING AND THIS MAY BE ENOUGH FOR THE
SWELLS TO GET TO CRITERIA.
BECAUSE WE ARE HAVING SUCH A HARD TIME REACHING THE SCA CRITERIA AND
WAVEWATCH IS NOW BACKING OFF ON SEAS ON WEDNESDAY, WE WILL NOT
EXTEND THE ADVISORY PAST TONIGHT WITH THIS PACKAGE. MOST OF THE
FORECAST FIVE FOOT SEAS ARE FORECAST TO BE NEAR THE EASTERN EDGE OF
OUR COASTAL WATERS. OTHERWISE, OUTSIDE OF ANY TSTMS, SOUTHERLY WINDS
ARE NOT EXPECTED TO REACH SMALL CRAFT ADVISORY CONDITIONS.
OUTLOOK...
HIGH PRESSURE WILL BUILD OVER THE WATERS WITH SUB-SCA CONDITIONS
EXPECTED FOR THE REGION WED NIGHT-SUN.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT WEDNESDAY FOR ANZ450>455.
&&
$$
SYNOPSIS...O`HARA
NEAR TERM...GIGI
SHORT TERM...GIGI
LONG TERM...O`HARA
AVIATION...GIGI
MARINE...GIGI
000
FXUS61 KPHI 151710
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
110 PM EDT TUE MAY 15 2012
.SYNOPSIS...
A WEAK FRONTAL BOUNDARY REMAINS NEAR THE AREA THROUGH TODAY. A WEAK
LOW PRESSURE SYSTEM WILL TRACK ALONG THIS FRONT, WHICH WILL SHIFT
EAST OF OUR REGION TONIGHT INTO WEDNESDAY. A SECONDARY COLD FRONT
WILL THEN SWEEP ACROSS THE AREA LATER WEDNESDAY. HIGH PRESSURE THEN
BUILDS INTO THE REGION THURSDAY AND FRIDAY, BEFORE SHIFTING INTO NEW
ENGLAND AND THE CANADIAN MARITIMES LATER SATURDAY AND SUNDAY. A LOW
PRESSURE SYSTEM MAY DEVELOP OFF THE SOUTHEASTERN UNITED STATES COAST
DURING THE WEEKEND AND EARLY NEXT WEEK.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
HEAVY RAIN IS MOVING THROUGH THE AREA NOW ASSOCIATED WITH A SHORT
WAVE/VORT MAX CROSSING THE AREA. THERE IS SOME INSTABILITY IN THE
ATMOSPHERE, SO THERE HAS BEEN SOME OCCASIONAL STRIKES OF
LIGHTNING ASSOCIATED WITH THE RAINFALL. THE ATMOSPHERE REMAINS
MOIST WITH PWATS AROUND 1.5 INCHES, SO THERE IS HEAVY RAINFALL
ASSOCIATED WITH THESE SHOWERS AND ISOLATED THUNDERSTORMS. THE GOOD
NEWS IS THE RAIN IS MOVING AT A STEADY PACE TO THE NORTHEAST.
AMOUNTS WITH THIS AREA OF RAIN SHOULD BE AROUND ONE-HALF OF AN
INCH, WITH SOME LOCALLY HIGHER AMOUNTS. WITH THESE AMOUNTS, WE
WILL HAVE PONDING ON ROAD WAYS AND STANDING WATER IN LOW LYING AND
URBAN AREAS. THE GRIDS WERE UPDATED FOR THE NEXT SEVERAL HOURS TO
FOLLOW THIS AREA OF RAINFALL, WHICH SHOULD EXIT THE AREA LATER
THIS MORNING OR EARLY THIS AFTERNOON.
AFTER THE SHORT WAVE EXITS EARLY THIS AFTERNOON...THERE COULD BE A
FAIRLY SUBSTANTIAL BREAK IN THE RAIN. WHILE THE AIRMASS REMAINS
MOIST (PRECIPITABLE WATER VALUES DO NOT CHANGE MUCH)...IT COULD BE
THAT LACK OF AN ORGANIZING TRIGGER THAT LOWER RAIN SHOWER CHANCES.
IN FACT...THERE IS SOME HINT THAT THE CLOUDS COULD BREAK FOR SOME
SUNSHINE THIS AFTERNOON...ESPECIALLY ACROSS WESTERN AREAS.
THE SUNSHINE COULD HELP WITH DESTABILIZATION OF AN ALREADY
MARGINALLY UNSTABLE AIRMASS. THE BEST INSTABILITY SHOULD LIE JUST
WEST OF THE AREA...WHERE BREAKS IN THE CLOUDS ARE MORE LIKELY. IN
THIS AREA...THE BEST BULK SHEAR PROBABLY EXITS WITH THE SHORT WAVE
THIS AFTERNOON...THOUGH SHEAR COULD REMAIN BORDERLINE INTO THE
EVENING. MID LEVEL LAPSE RATES APPEAR AS THOUGH THEY WILL BE
MARGINAL AT BEST AS WELL.
SO...AT THIS POINT...THE BEST CHANCE OF THUNDERSTORM DEVELOPS LOOKS
TO BE JUST WEST OF THE AREA...OR ACROSS THE LEHIGH VALLEY. MODIFIED
MODEL SOUNDINGS WEST OF THE DELAWARE RIVER SHOW MARGINAL
INSTABILITY...MARGINAL SHEAR...AND RELATIVELY LOW MEAN LAYER CAPE
VALUES. THIS WOULD SUGGEST SCATTERED THUNDERSTORMS ACROSS WESTERN
AREAS THIS AFTERNOON AND THIS EVENING.. THERE IS A LOW POTENTIAL FOR
GUSTY WINDS (SOME MID LEVEL DRYING AND INCREASING DELTA EPT VALUES)
AND SMALL HAIL (WET BULB ZERO VALUES NEAR 9500 FEET). HOWEVER...
SINCE MOST MODIFIED SOUNDINGS SHOW A TALL THIN CAPE (SUGGESTING
SHORT LIVED CONVECTIVE CELLS)...NO ENHANCED WORDING WILL BE ADDED AT
THIS TIME.
THE HIGH TEMPERATURE FORECAST WILL BE TIED TO THE AMOUNT OF CLEARING
TODAY (IF ANY SIGNIFICANT CLEARING CAN OCCUR). FOR NOW...HIGHS WERE
BASED MAINLY ON THE MOS BLEND...DUE TO LOW CONFIDENCE LEVELS. RIGHT
NOW...THE HIGHER GFS MOS NUMBERS APPEAR TOO HIGH...BUT MORE BREAKS
COULD EASILY SEND HIGHS TO THOSE LEVELS.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM WEDNESDAY/...
THE POTENTIAL FOR EVENING CONVECTION STANDS AS THE BEST CHANCE FOR
MEANINGFUL RAIN CHANCES FOR THIS PERIOD. SCATTERED SHOWERS AND
THUNDERSTORMS SHOULD BE CLOSE TO THE DELAWARE RIVER THIS EVENING. AS
THE BEST INSTABILITY IS EXHAUSTED...THE SHOWERS AND THUNDERSTORMS
SHOULD WEAKEN AS THEY MOVE EAST. THE LAST OF WHATEVER IS LEFT COULD
REACH THE COAST BY ABOUT 0500 UTC.
AFTER THIS...THERE MAY NOT BE MUCH IN THE WAY OF SHOWER ACTIVITY
OVERNIGHT. THE 0000 UTC NAM DOES SHOW SOME PRECIPITATION NEAR THE
NEW JERSEY COAST (OSTENSIBLY ASSOCIATED WITH A WEAK WARM FRONT THAT
ARRIVES FROM THE NORTH CAROLINA COAST). THE 0000 GFS TAKES THIS
OFFSHORE...AND FOR NOW THIS SOLUTION IS ACCEPTED.
THE CLOUD COVER FORECAST MAY ALSO BE A PROBLEM. THERE COULD BE
BREAKS THIS EVENING...BUT MOS GUIDANCE SUGGESTS THIS IS PAVED OVER
BY LOW CLOUDS. THIS IS ACCEPTED FOR NOW...BUT COULD BE OVERDONE ON A
SOUTH TO SOUTHWEST BOUNDARY LAYER FLOW. AT THIS POINT...WILL NOT HIT
THE FOG HARD...BUT AREAS THAT DO GET RAIN TODAY COULD SEE PATCHY FOG
TONIGHT...ESPECIALLY WITH CLOUDS BREAKS. FOR THE MOST PART...LOWS
WERE BASED ON THE MOS BLEND.
&&
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
THE OVERALL SYNOPTIC SETUP IS COMPRISED OF A TROUGH AMPLIFYING
ACROSS EASTERN CANADA AND INTO THE NORTHEAST WEDNESDAY INTO
THURSDAY. THIS FEATURE THEN STARTS TO LIFT OUT LATER THURSDAY AS
RIDGING IN THE MIDWEST SLIDES EASTWARD WHILE A TROUGH DIGS ACROSS
THE WEST. THE MAIN SENSIBLE WEATHER ACROSS OUR AREA IS WEDNESDAY,
WHICH IS TIED TO THE AMPLIFYING TROUGH AND ASSOCIATED SURFACE COLD
FRONT. THE PATTERN THEN TRANSITIONS TO MORE OF A RIDGE BUILDING INTO
THE EAST AS THE TROUGH SETTLES ACROSS THE WEST AND EVENTUALLY INTO
THE PLAINS. A POTENTIAL FLY IN THE OINTMENT THOUGH IS A POCKET OF
ENERGY THAT MAY UNDERCUT THE BUILDING RIDGE AND GET STUCK NEAR THE
SOUTHEASTERN U.S. COAST THIS WEEKEND AND EARLY NEXT WEEK. THIS MAY
LEAD TO AN UPPER-LEVEL LOW AND SURFACE LOW REFLECTION, ALTHOUGH
THERE IS MORE UNCERTAINTY WITH THIS EVOLUTION.
FOR WEDNESDAY, THE MAIN MOISTURE PLUME AND SHORT WAVE ENERGY WILL BE
SHIFTING TO OUR NORTHEAST TO START THE DAY THEREFORE PERHAPS SOME
SHOWERS EARLY ON. AS THE UPPER-LEVEL TROUGH HOWEVER AMPLIFIES INTO
THE NORTHEAST, A SURFACE COLD FRONT WILL SWEEP ACROSS OUR AREA BY
MID EVENING. THERE IS SOME CONVECTIVE POTENTIAL ALONG AND AHEAD OF
THIS SECONDARY COLD FRONT, HOWEVER THE COVERAGE AND INTENSITY WILL
DEPEND ON A FEW THINGS INCLUDING THE AMOUNT OF INSTABILITY.
THE DAY MAY START WITH SOME FOG AND LOW CLOUDS, BUT ENOUGH BOUNDARY
LAYER HEATING SHOULD RESULT IN AT LEAST SOME SUNSHINE DEVELOPING
ALONG WITH BETTER MIXING LEADING TO STEEPENING LOW-LEVEL LAPSE RATES.
THE MODEL GUIDANCE DEVELOPS INSTABILITY ACROSS THE REGION, WITH A
MORE PRONOUNCED INSTABILITY AXIS NOTED MOSTLY ACROSS THE WESTERN
HALF OF THE CWA. WHILE THERE COULD BE SOME SHOWERS AND THUNDER
WITHIN THIS ZONE, WE MAY HAVE TO WAIT FOR THE MAIN COLD FRONT TO
ARRIVE TO HELP FOCUS ANY CONVECTION. THE AIRMASS IS FORECAST TO DRY
OUT ESPECIALLY IN THE MID LEVELS, ALTHOUGH THE SURFACE DEW POINTS
MAY LOWER SOME DURING THE DAY WITH IMPROVED MIXING, AND THE SHEAR
DOES INCREASE AHEAD OF THE FRONT. IF THE FORCING IS STRONG ENOUGH
AND WE REACH OUR FORECAST HIGHS, LOCALLY STRONG CONVECTION COULD
DEVELOP BUT THIS MAY NOT BE REAL ORGANIZED. BASED ON THE FORECAST
SOUNDINGS, THE MOSTLY UNIDIRECTIONAL FLOW FROM THE SOUTHWEST BEING
PRESENT MAY ALLOW FOR A FEW CONVECTIVE LINES IF MORE ROBUST
UPDRAFTS CAN BE SUSTAINED. THIS MAY FAVOR LOCALLY GUSTY WINDS AND
SOME HAIL WITH ANY STRONGER CONVECTIVE CORES. WE WILL CARRY LOW CHC
POPS ACROSS THE AREA FOR SCATTERED SHOWERS AND THUNDERSTORMS AHEAD
OF THE FRONT, BUT NOT INCLUDE ANY ENHANCED WORDING IN THE FORECAST
ATTM DUE TO UNCERTAINTY IN THE CONVECTIVE EVOLUTION. WE WILL HOWEVER
CONTINUE A MENTION IN THE HAZARDOUS WEATHER OUTLOOK. THE POPS
QUICKLY LOWER AND END DURING THE EVENING AS THE FRONT CLEARS THE
REGION AND DRIER AIR ADVECTS IN. THE WINDS WILL SHIFT TO THE
NORTHWEST AND NORTH FOLLOWING THE COLD FRONTAL PASSAGE.
FOR THURSDAY AND FRIDAY, THE UPPER-LEVEL TROUGH BEGINS TO LIFT
NORTHEASTWARD THURSDAY AND HIGH PRESSURE ARRIVES FROM THE WEST. AS
MID LEVEL RIDGING GRADUALLY SLIDES EASTWARD, THE SURFACE HIGH WILL
TEND TO RELOCATE OFF THE NEW ENGLAND COAST BUT STILL EXTEND DOWN
INTO THE MID ATLANTIC. THIS WILL RESULT IN LIGHT WINDS AND MILD
TEMPERATURES, ALTHOUGH THE LACK OF A PRESSURE GRADIENT WILL PROBABLY
LEAD TO SEA BREEZE CIRCULATIONS DEVELOPING ESPECIALLY FRIDAY
AFTERNOON.
FOR SATURDAY AND SUNDAY, HIGH PRESSURE FROM THE MID ATLANTIC TO NEAR
THE CANADIAN MARITIMES WILL REMAIN NEARLY STATIONARY. HOWEVER, THE
UPPER-LEVEL RIDGE NEARS THE EAST COAST SUNDAY WHICH WOULD PUSH THE
SURFACE HIGH A BIT TO THE EAST ALLOWING FOR MORE OF A RETURN FLOW TO
DEVELOP. INTERESTINGLY ENOUGH, SOME OF THE MODEL GUIDANCE DEVELOPS
DIURNAL CONVECTION NEAR THE OUTER EDGE OF THE UPPER-LEVEL RIDGE.
THIS LOOKS TO BE TIED MORE TO TERRAIN CIRCULATIONS, WHICH SOME
DEVELOPMENT GETS VERY CLOSE TO OUR NORTHWEST ZONES. GIVEN THE
PLACEMENT OF THE RIDGE, THINK THE CHC OF THIS IS RATHER LOW ATTM
THEREFORE WE MAINTAINED A DRY FORECAST. SOME OF THE MODEL GUIDANCE
SUGGEST THAT ENERGY UNDERCUTTING THE RIDGE BECOMES CUT OFF AND TENDS
TO SPIN UP A SURFACE LOW IN THE VICINITY OF THE SOUTHEASTERN U.S.
COAST. THIS FEATURE MAY END UP REMAINING WEAK, WHICH WOULD LEAD TO
MORE UNCERTAINTY REGARDING ITS MOVEMENT. AT THIS POINT GIVEN THE
RIDGE FORECAST TO BE IN PLACE TO THE NORTH, WE ARE NOT ANTICIPATING
ANY REAL IMPACTS FROM THIS POTENTIAL DEVELOPMENT.
FOR MONDAY, THE ENTIRE RIDGE AND SURFACE HIGH ARE NUDGED FARTHER TO
OUR EAST AS SOME TROUGHING PUSHES THROUGH THE GREAT LAKES REGION.
THIS WILL SEND A COLD FRONT EASTBOUND, HOWEVER THIS LOOKS TO STAY
FAIRLY FAR TO OUR WEST DURING THIS TIME FRAME. THE MILD CONDITIONS
WILL CONTINUE THOUGH GIVEN A RETURN FLOW OCCURRING.
&&
.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.
WE ARE EXPECTING IMPROVING CONDITIONS TO VFR AT TIMES THIS
AFTERNOON. THE LAST AIRPORTS TO LOSE IFR CIGS SHOULD BE OUR NEW
JERSEY TERMINALS AND OTHER AIRPORTS TOWARD NYC. NOT CONFIDENT WE
WILL LOSE ALL MVFR CIGS AS THE TEMPERATURE AND DEW POINT SPREADS
ARE NOT THAT LARGE. THERE WILL BE SCATTERED CONVECTION (TSTMS)
AROUND THIS AFTERNOON MAINLY WEST AND SOUTH OF ALL OUR TERMINALS.
SO THE LEAST CONFIDENT TAF SITES AT AVOIDING THEM ARE KRDG AND KACY.
WINDS OVERALL SHOULD BE LIGHT FROM THE SOUTH.
WE ARE CONTINUING THE TREND TOWARD IFR CONDITIONS LATE THIS
EVENING AND OVERNIGHT. FORECAST SOUNDINGS ARE PRETTY MOIST TOWARD
THE GROUND AND WITH LIGHT WINDS, WE DO FORECAST AN IFR CIG WITH
SOME IFR VSBYS AT OUR FOGGIER OUTLYING TERMINALS.
WITH STRONG WEST WINDS FORECAST TO OCCUR ON WEDNESDAY MORNING, WE
BRING VFR CONDITIONS RAPIDLY TO ALL THE TERMINALS BY THE MIDDLE OF
THE MORNING. WHILE THERE SHOULD BE SOME WIDELY SCATTERED
CONVECTION AROUND, THE COVERAGE IS TOO LOW TO INCLUDE IN THE TAFS
AT THIS TIME.
OUTLOOK...
WEDNESDAY...SUB-VFR POSSIBLE TO START DUE TO LOW CLOUDS OR FOG, THEN
IMPROVING TO VFR. A FEW SHOWERS OR THUNDERSTORMS ARE POSSIBLE WITH
LOCAL AND BRIEF SUB-VFR INTO THE EARLY EVENING. VFR AT NIGHT AS THE
WINDS SHIFT TO THE NORTH.
THURSDAY AND FRIDAY...VFR. LIGHT WINDS ESPECIALLY FRIDAY MAY
RESULT IN SEA AND/OR BAY BREEZES.
SATURDAY...VFR WITH LIGHT WINDS.
&&
.MARINE...
THE SURGE OF SMALL CRAFT WIND GUSTS ASSOCIATED WITH A LOW LEVEL
JET HAS PASSED NORTHEAST OF THE BAY. THE SECOND SURGE DEPICTED ON
THE PREVIOUS GUIDANCE WEAKENED AND BASED ON WEAKENING VAD WINDS AT
KDOX AND 12Z BUFKIT FCST SOUNDINGS AT KDOV COINCIDING WELL WITH
CURRENT GUSTS AT BRANDYWINE AND SHIP JOHNS, WE WILL END THE SMALL
CRAFT ADVISORY EARLY.
THE SOUTHEAST FLOW PROBABLY DOES NOT INCREASE THAT MUCH
TODAY...AND WIND SPEEDS ARE EXPECTED TO REMAIN MAINLY BELOW SMALL
CRAFT LEVELS. SEAS HAVE JUST STARTED TO REACH SMALL CRAFT ADVISORY
LEVELS AND THIS SHOULD SPREAD AS THE DAY PROGRESSES...ADMITTEDLY ITS
BEEN SLOW.
WINDS MAY TEND TO DROP OFF LATER TONIGHT AS THE SURFACE GRADIENT
BACKS OFF AHEAD OF A WEAK COLD FRONT TO THE WEST. AGAIN THE
FORECAST QUESTION FOR TONIGHT IS WHETHER SEAS GET TO/MAINTAIN SMALL
CRAFT CRITERION. FOR NOW...WILL CONTINUE WITH THE SAME FORECAST
RATIONALE FOR TONIGHT.
OUTLOOK...
THE SOUTHERLY FLOW PRIOR TO A COLD FRONTAL PASSAGE LATER WEDNESDAY
MAY RESULT IN SEAS ON THE OCEAN AROUND 5 FEET. THE SEAS HAVE BEEN
SLOW TO RESPONSE SO FAR IN THE SOUTHERLY FLOW IN THE NEAR TERM,
THEREFORE WE DECIDED NOT TO EXTEND THE SMALL CRAFT ADVISORY INTO
WEDNESDAY AT THIS POINT. THE COLD FRONT SWEEPS EAST OF THE REGION
WEDNESDAY EVENING WITH A NORTHERLY FLOW OCCURRING. THIS DOES NOT
APPEAR STRONG ENOUGH TO GENERATE SMALL CRAFT CONDITIONS CAUSED BY
EITHER SEAS OR WINDS. HIGH PRESSURE THEN SETTLES IN THURSDAY AND
FRIDAY, ALTHOUGH THE NORTHERLY WINDS MAY TEND TO TURN ONSHORE AS THE
FLOW WEAKENS AND POSSIBLE SEA BREEZE CIRCULATIONS DEVELOP. THE
SURFACE HIGH BUILDS EASTWARD FRIDAY AND SATURDAY, ALLOWING FOR MORE
OF A SOUTHEAST FLOW TO OCCUR. A PIECE OF ENERGY POSSIBLY
UNDERCUTTING THE BUILDING RIDGE MAY RESULT IN A SURFACE LOW
DEVELOPING OFF THE SOUTHEASTERN U.S. COAST OVER THE WEEKEND. IT
APPEARS THOUGH THE SURFACE HIGH REMAINS CLOSE ENOUGH TO OUR REGION,
WHICH WOULD NOT GENERATE MUCH OF A LONG ONSHORE FETCH FOR OUR AREA.
&&
.HYDROLOGY...
HEAVY RAIN...TIED TO A SHORT WAVE IN THE MID LEVELS HAS NOW MOVED
ACROSS THE AREA. THIS BATCH HAS SOME ELEVATED INSTABILITY ASSOCIATED
WITH IT...AND PRECIPITABLE WATER VALUES INCREASE TO NEAR 1.50
INCHES. THE SPECTER OF HEAVY RAIN IS STILL IN PLACE FOR THIS
BATCH...WHICH SHOULD CLEAR NORTHERN ZONES BY LATE MORNING OR EARLY
AFTERNOON.
WE WOULD PROBABLY NEED ANOTHER 1.50 TO 2.00 INCHES OF BASIN AVERAGE
RAINFALL ACROSS THE SOUTHERN POCONOS AND NORTHWEST NEW JERSEY BEFORE
PROBLEMS START (BASED ON THE LATEST HEADWATER GUIDANCE). WHILE NOT
OUT OF THE QUESTION DUE TO THE MOISTURE BLOB TO THE SOUTHWEST...IT
IS LOOKING LESS LIKELY THAN 24 HOURS AGO.
ONCE THAT SHOWER BATCH EXITS...CONVECTIVE ELEMENTS ARE POSSIBLE
LATER THIS AFTERNOON AND THIS EVENING. HOWEVER...IT DOES NOT APPEAR
AS THROUGH THE CONVECTION WILL BE WIDESPREAD ENOUGH TO POSE A
THREAT. THAT HAVING BEEN STATED...THERE ARE NO PLANS FOR HYDROLOGY
HEADLINES TODAY WITH RESPECT TO THE NEXT BATCH OF RAIN.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT WEDNESDAY FOR ANZ450>455.
&&
$$
SYNOPSIS...GORSE
NEAR TERM...HAYES/ROBERTSON
SHORT TERM...HAYES
LONG TERM...GORSE
AVIATION...GIGI/GORSE
MARINE...GIGI/GORSE/HAYES
HYDROLOGY...
000
FXUS61 KPHI 151523
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1123 AM EDT TUE MAY 15 2012
.SYNOPSIS...
A WEAK FRONTAL BOUNDARY REMAINS NEAR THE AREA THROUGH TODAY. A WEAK
LOW PRESSURE SYSTEM WILL TRACK ALONG THIS FRONT, WHICH WILL SHIFT
EAST OF OUR REGION TONIGHT INTO WEDNESDAY. A SECONDARY COLD FRONT
WILL THEN SWEEP ACROSS THE AREA LATER WEDNESDAY. HIGH PRESSURE THEN
BUILDS INTO THE REGION THURSDAY AND FRIDAY, BEFORE SHIFTING INTO NEW
ENGLAND AND THE CANADIAN MARITIMES LATER SATURDAY AND SUNDAY. A LOW
PRESSURE SYSTEM MAY DEVELOP OFF THE SOUTHEASTERN UNITED STATES COAST
DURING THE WEEKEND AND EARLY NEXT WEEK.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
HEAVY RAIN IS MOVING THROUGH THE AREA NOW ASSOCIATED WITH A SHORT
WAVE/VORT MAX CROSSING THE AREA. THERE IS SOME INSTABILITY IN THE
ATMOSPHERE, SO THERE HAS BEEN SOME OCCASIONAL STRIKES OF
LIGHTNING ASSOCIATED WITH THE RAINFALL. THE ATMOSPHERE REMAINS
MOIST WITH PWATS AROUND 1.5 INCHES, SO THERE IS HEAVY RAINFALL
ASSOCIATED WITH THESE SHOWERS AND ISOLATED THUNDERSTORMS. THE GOOD
NEWS IS THE RAIN IS MOVING AT A STEADY PACE TO THE NORTHEAST.
AMOUNTS WITH THIS AREA OF RAIN SHOULD BE AROUND ONE-HALF OF AN
INCH, WITH SOME LOCALLY HIGHER AMOUNTS. WITH THESE AMOUNTS, WE
WILL HAVE PONDING ON ROAD WAYS AND STANDING WATER IN LOW LYING AND
URBAN AREAS. THE GRIDS WERE UPDATED FOR THE NEXT SEVERAL HOURS TO
FOLLOW THIS AREA OF RAINFALL, WHICH SHOULD EXIT THE AREA LATER
THIS MORNING OR EARLY THIS AFTERNOON.
AFTER THE SHORT WAVE EXITS EARLY THIS AFTERNOON...THERE COULD BE A
FAIRLY SUBSTANTIAL BREAK IN THE RAIN. WHILE THE AIRMASS REMAINS
MOIST (PRECIPITABLE WATER VALUES DO NOT CHANGE MUCH)...IT COULD BE
THAT LACK OF AN ORGANIZING TRIGGER THAT LOWER RAIN SHOWER CHANCES.
IN FACT...THERE IS SOME HINT THAT THE CLOUDS COULD BREAK FOR SOME
SUNSHINE THIS AFTERNOON...ESPECIALLY ACROSS WESTERN AREAS.
THE SUNSHINE COULD HELP WITH DESTABILIZATION OF AN ALREADY
MARGINALLY UNSTABLE AIRMASS. THE BEST INSTABILITY SHOULD LIE JUST
WEST OF THE AREA...WHERE BREAKS IN THE CLOUDS ARE MORE LIKELY. IN
THIS AREA...THE BEST BULK SHEAR PROBABLY EXITS WITH THE SHORT WAVE
THIS AFTERNOON...THOUGH SHEAR COULD REMAIN BORDERLINE INTO THE
EVENING. MID LEVEL LAPSE RATES APPEAR AS THOUGH THEY WILL BE
MARGINAL AT BEST AS WELL.
SO...AT THIS POINT...THE BEST CHANCE OF THUNDERSTORM DEVELOPS LOOKS
TO BE JUST WEST OF THE AREA...OR ACROSS THE LEHIGH VALLEY. MODIFIED
MODEL SOUNDINGS WEST OF THE DELAWARE RIVER SHOW MARGINAL
INSTABILITY...MARGINAL SHEAR...AND RELATIVELY LOW MEAN LAYER CAPE
VALUES. THIS WOULD SUGGEST SCATTERED THUNDERSTORMS ACROSS WESTERN
AREAS THIS AFTERNOON AND THIS EVENING.. THERE IS A LOW POTENTIAL FOR
GUSTY WINDS (SOME MID LEVEL DRYING AND INCREASING DELTA EPT VALUES)
AND SMALL HAIL (WET BULB ZERO VALUES NEAR 9500 FEET). HOWEVER...
SINCE MOST MODIFIED SOUNDINGS SHOW A TALL THIN CAPE (SUGGESTING
SHORT LIVED CONVECTIVE CELLS)...NO ENHANCED WORDING WILL BE ADDED AT
THIS TIME.
THE HIGH TEMPERATURE FORECAST WILL BE TIED TO THE AMOUNT OF CLEARING
TODAY (IF ANY SIGNIFICANT CLEARING CAN OCCUR). FOR NOW...HIGHS WERE
BASED MAINLY ON THE MOS BLEND...DUE TO LOW CONFIDENCE LEVELS. RIGHT
NOW...THE HIGHER GFS MOS NUMBERS APPEAR TOO HIGH...BUT MORE BREAKS
COULD EASILY SEND HIGHS TO THOSE LEVELS.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM WEDNESDAY/...
THE POTENTIAL FOR EVENING CONVECTION STANDS AS THE BEST CHANCE FOR
MEANINGFUL RAIN CHANCES FOR THIS PERIOD. SCATTERED SHOWERS AND
THUNDERSTORMS SHOULD BE CLOSE TO THE DELAWARE RIVER THIS EVENING. AS
THE BEST INSTABILITY IS EXHAUSTED...THE SHOWERS AND THUNDERSTORMS
SHOULD WEAKEN AS THEY MOVE EAST. THE LAST OF WHATEVER IS LEFT COULD
REACH THE COAST BY ABOUT 0500 UTC.
AFTER THIS...THERE MAY NOT BE MUCH IN THE WAY OF SHOWER ACTIVITY
OVERNIGHT. THE 0000 UTC NAM DOES SHOW SOME PRECIPITATION NEAR THE
NEW JERSEY COAST (OSTENSIBLY ASSOCIATED WITH A WEAK WARM FRONT THAT
ARRIVES FROM THE NORTH CAROLINA COAST). THE 0000 GFS TAKES THIS
OFFSHORE...AND FOR NOW THIS SOLUTION IS ACCEPTED.
THE CLOUD COVER FORECAST MAY ALSO BE A PROBLEM. THERE COULD BE
BREAKS THIS EVENING...BUT MOS GUIDANCE SUGGESTS THIS IS PAVED OVER
BY LOW CLOUDS. THIS IS ACCEPTED FOR NOW...BUT COULD BE OVERDONE ON A
SOUTH TO SOUTHWEST BOUNDARY LAYER FLOW. AT THIS POINT...WILL NOT HIT
THE FOG HARD...BUT AREAS THAT DO GET RAIN TODAY COULD SEE PATCHY FOG
TONIGHT...ESPECIALLY WITH CLOUDS BREAKS. FOR THE MOST PART...LOWS
WERE BASED ON THE MOS BLEND.
&&
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
THE OVERALL SYNOPTIC SETUP IS COMPRISED OF A TROUGH AMPLIFYING
ACROSS EASTERN CANADA AND INTO THE NORTHEAST WEDNESDAY INTO
THURSDAY. THIS FEATURE THEN STARTS TO LIFT OUT LATER THURSDAY AS
RIDGING IN THE MIDWEST SLIDES EASTWARD WHILE A TROUGH DIGS ACROSS
THE WEST. THE MAIN SENSIBLE WEATHER ACROSS OUR AREA IS WEDNESDAY,
WHICH IS TIED TO THE AMPLIFYING TROUGH AND ASSOCIATED SURFACE COLD
FRONT. THE PATTERN THEN TRANSITIONS TO MORE OF A RIDGE BUILDING INTO
THE EAST AS THE TROUGH SETTLES ACROSS THE WEST AND EVENTUALLY INTO
THE PLAINS. A POTENTIAL FLY IN THE OINTMENT THOUGH IS A POCKET OF
ENERGY THAT MAY UNDERCUT THE BUILDING RIDGE AND GET STUCK NEAR THE
SOUTHEASTERN U.S. COAST THIS WEEKEND AND EARLY NEXT WEEK. THIS MAY
LEAD TO AN UPPER-LEVEL LOW AND SURFACE LOW REFLECTION, ALTHOUGH
THERE IS MORE UNCERTAINTY WITH THIS EVOLUTION.
FOR WEDNESDAY, THE MAIN MOISTURE PLUME AND SHORT WAVE ENERGY WILL BE
SHIFTING TO OUR NORTHEAST TO START THE DAY THEREFORE PERHAPS SOME
SHOWERS EARLY ON. AS THE UPPER-LEVEL TROUGH HOWEVER AMPLIFIES INTO
THE NORTHEAST, A SURFACE COLD FRONT WILL SWEEP ACROSS OUR AREA BY
MID EVENING. THERE IS SOME CONVECTIVE POTENTIAL ALONG AND AHEAD OF
THIS SECONDARY COLD FRONT, HOWEVER THE COVERAGE AND INTENSITY WILL
DEPEND ON A FEW THINGS INCLUDING THE AMOUNT OF INSTABILITY.
THE DAY MAY START WITH SOME FOG AND LOW CLOUDS, BUT ENOUGH BOUNDARY
LAYER HEATING SHOULD RESULT IN AT LEAST SOME SUNSHINE DEVELOPING
ALONG WITH BETTER MIXING LEADING TO STEEPENING LOW-LEVEL LAPSE RATES.
THE MODEL GUIDANCE DEVELOPS INSTABILITY ACROSS THE REGION, WITH A
MORE PRONOUNCED INSTABILITY AXIS NOTED MOSTLY ACROSS THE WESTERN
HALF OF THE CWA. WHILE THERE COULD BE SOME SHOWERS AND THUNDER
WITHIN THIS ZONE, WE MAY HAVE TO WAIT FOR THE MAIN COLD FRONT TO
ARRIVE TO HELP FOCUS ANY CONVECTION. THE AIRMASS IS FORECAST TO DRY
OUT ESPECIALLY IN THE MID LEVELS, ALTHOUGH THE SURFACE DEW POINTS
MAY LOWER SOME DURING THE DAY WITH IMPROVED MIXING, AND THE SHEAR
DOES INCREASE AHEAD OF THE FRONT. IF THE FORCING IS STRONG ENOUGH
AND WE REACH OUR FORECAST HIGHS, LOCALLY STRONG CONVECTION COULD
DEVELOP BUT THIS MAY NOT BE REAL ORGANIZED. BASED ON THE FORECAST
SOUNDINGS, THE MOSTLY UNIDIRECTIONAL FLOW FROM THE SOUTHWEST BEING
PRESENT MAY ALLOW FOR A FEW CONVECTIVE LINES IF MORE ROBUST
UPDRAFTS CAN BE SUSTAINED. THIS MAY FAVOR LOCALLY GUSTY WINDS AND
SOME HAIL WITH ANY STRONGER CONVECTIVE CORES. WE WILL CARRY LOW CHC
POPS ACROSS THE AREA FOR SCATTERED SHOWERS AND THUNDERSTORMS AHEAD
OF THE FRONT, BUT NOT INCLUDE ANY ENHANCED WORDING IN THE FORECAST
ATTM DUE TO UNCERTAINTY IN THE CONVECTIVE EVOLUTION. WE WILL HOWEVER
CONTINUE A MENTION IN THE HAZARDOUS WEATHER OUTLOOK. THE POPS
QUICKLY LOWER AND END DURING THE EVENING AS THE FRONT CLEARS THE
REGION AND DRIER AIR ADVECTS IN. THE WINDS WILL SHIFT TO THE
NORTHWEST AND NORTH FOLLOWING THE COLD FRONTAL PASSAGE.
FOR THURSDAY AND FRIDAY, THE UPPER-LEVEL TROUGH BEGINS TO LIFT
NORTHEASTWARD THURSDAY AND HIGH PRESSURE ARRIVES FROM THE WEST. AS
MID LEVEL RIDGING GRADUALLY SLIDES EASTWARD, THE SURFACE HIGH WILL
TEND TO RELOCATE OFF THE NEW ENGLAND COAST BUT STILL EXTEND DOWN
INTO THE MID ATLANTIC. THIS WILL RESULT IN LIGHT WINDS AND MILD
TEMPERATURES, ALTHOUGH THE LACK OF A PRESSURE GRADIENT WILL PROBABLY
LEAD TO SEA BREEZE CIRCULATIONS DEVELOPING ESPECIALLY FRIDAY
AFTERNOON.
FOR SATURDAY AND SUNDAY, HIGH PRESSURE FROM THE MID ATLANTIC TO NEAR
THE CANADIAN MARITIMES WILL REMAIN NEARLY STATIONARY. HOWEVER, THE
UPPER-LEVEL RIDGE NEARS THE EAST COAST SUNDAY WHICH WOULD PUSH THE
SURFACE HIGH A BIT TO THE EAST ALLOWING FOR MORE OF A RETURN FLOW TO
DEVELOP. INTERESTINGLY ENOUGH, SOME OF THE MODEL GUIDANCE DEVELOPS
DIURNAL CONVECTION NEAR THE OUTER EDGE OF THE UPPER-LEVEL RIDGE.
THIS LOOKS TO BE TIED MORE TO TERRAIN CIRCULATIONS, WHICH SOME
DEVELOPMENT GETS VERY CLOSE TO OUR NORTHWEST ZONES. GIVEN THE
PLACEMENT OF THE RIDGE, THINK THE CHC OF THIS IS RATHER LOW ATTM
THEREFORE WE MAINTAINED A DRY FORECAST. SOME OF THE MODEL GUIDANCE
SUGGEST THAT ENERGY UNDERCUTTING THE RIDGE BECOMES CUT OFF AND TENDS
TO SPIN UP A SURFACE LOW IN THE VICINITY OF THE SOUTHEASTERN U.S.
COAST. THIS FEATURE MAY END UP REMAINING WEAK, WHICH WOULD LEAD TO
MORE UNCERTAINTY REGARDING ITS MOVEMENT. AT THIS POINT GIVEN THE
RIDGE FORECAST TO BE IN PLACE TO THE NORTH, WE ARE NOT ANTICIPATING
ANY REAL IMPACTS FROM THIS POTENTIAL DEVELOPMENT.
FOR MONDAY, THE ENTIRE RIDGE AND SURFACE HIGH ARE NUDGED FARTHER TO
OUR EAST AS SOME TROUGHING PUSHES THROUGH THE GREAT LAKES REGION.
THIS WILL SEND A COLD FRONT EASTBOUND, HOWEVER THIS LOOKS TO STAY
FAIRLY FAR TO OUR WEST DURING THIS TIME FRAME. THE MILD CONDITIONS
WILL CONTINUE THOUGH GIVEN A RETURN FLOW OCCURRING.
&&
.AVIATION /15Z TUESDAY THROUGH SATURDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.
AFTER THE IFR TO MVFR CONDITIONS LATE THIS MORNING...CONDITIONS
MAY TRY TO IMPROVE TO NEAR VFR...ESPECIALLY SOUTH AND EAST OF
KPHL. CONSIDERING HOW SLOWLY CONDITIONS HAVE BEEN TO DROP...THIS
DOES NOT SEEM IMPLAUSIBLE...BUT CONFIDENCE IN VFR CONDITIONS THIS
AFTERNOON IS STILL LOW. SCATTERED THUNDERSTORMS MAY TRY TO FROM
WEST OF THE AREA THIS AFTERNOON...AND COULD IMPACT KPHL METRO
TERMINALS AFTER 0000 UTC. HOWEVER...CONFIDENCE WAS NOT HIGH ENOUGH
FOR INCLUSION IN THE 0600 UTC TERMINAL FORECASTS.
AFTER THE POTENTIAL FOR CONVECTION EXITS...CONDITIONS SHOULD SETTLE
BACK TO MVFR AFTER 0300 UTC WEDNESDAY. STATISTICAL GUIDANCE SUGGEST
CONDITIONS COULD LOWER TO IFR...BUT FOR NOW THIS WAS NOT INCLUDED IN
THE FORECAST.
OUTLOOK...
WEDNESDAY...SUB-VFR POSSIBLE TO START DUE TO LOW CLOUDS OR FOG, THEN
IMPROVING TO VFR. A FEW SHOWERS OR THUNDERSTORMS ARE POSSIBLE WITH
LOCAL AND BRIEF SUB-VFR INTO THE EARLY EVENING. VFR AT NIGHT AS THE
WINDS SHIFT TO THE NORTH.
THURSDAY AND FRIDAY...VFR. LIGHT WINDS ESPECIALLY FRIDAY MAY
RESULT IN SEA AND/OR BAY BREEZES.
SATURDAY...VFR WITH LIGHT WINDS.
&&
.MARINE...
THE SURGE OF SMALL CRAFT WIND GUSTS ASSOCIATED WITH A LOW LEVEL
JET HAS PASSED NORTHEAST OF THE BAY. THE SECOND SURGE DEPICTED ON
THE PREVIOUS GUIDANCE WEAKENED AND BASED ON WEAKENING VAD WINDS AT
KDOX AND 12Z BUFKIT FCST SOUNDINGS AT KDOV COINCIDING WELL WITH
CURRENT GUSTS AT BRANDYWINE AND SHIP JOHNS, WE WILL END THE SMALL
CRAFT ADVISORY EARLY.
THE SOUTHEAST FLOW PROBABLY DOES NOT INCREASE THAT MUCH
TODAY...AND WIND SPEEDS ARE EXPECTED TO REMAIN MAINLY BELOW SMALL
CRAFT LEVELS. SEAS HAVE JUST STARTED TO REACH SMALL CRAFT ADVISORY
LEVELS AND THIS SHOULD SPREAD AS THE DAY PROGRESSES...ADMITTEDLY ITS
BEEN SLOW.
WINDS MAY TEND TO DROP OFF LATER TONIGHT AS THE SURFACE GRADIENT
BACKS OFF AHEAD OF A WEAK COLD FRONT TO THE WEST. AGAIN THE
FORECAST QUESTION FOR TONIGHT IS WHETHER SEAS GET TO/MAINTAIN SMALL
CRAFT CRITERION. FOR NOW...WILL CONTINUE WITH THE SAME FORECAST
RATIONALE FOR TONIGHT.
OUTLOOK...
THE SOUTHERLY FLOW PRIOR TO A COLD FRONTAL PASSAGE LATER WEDNESDAY
MAY RESULT IN SEAS ON THE OCEAN AROUND 5 FEET. THE SEAS HAVE BEEN
SLOW TO RESPONSE SO FAR IN THE SOUTHERLY FLOW IN THE NEAR TERM,
THEREFORE WE DECIDED NOT TO EXTEND THE SMALL CRAFT ADVISORY INTO
WEDNESDAY AT THIS POINT. THE COLD FRONT SWEEPS EAST OF THE REGION
WEDNESDAY EVENING WITH A NORTHERLY FLOW OCCURRING. THIS DOES NOT
APPEAR STRONG ENOUGH TO GENERATE SMALL CRAFT CONDITIONS CAUSED BY
EITHER SEAS OR WINDS. HIGH PRESSURE THEN SETTLES IN THURSDAY AND
FRIDAY, ALTHOUGH THE NORTHERLY WINDS MAY TEND TO TURN ONSHORE AS THE
FLOW WEAKENS AND POSSIBLE SEA BREEZE CIRCULATIONS DEVELOP. THE
SURFACE HIGH BUILDS EASTWARD FRIDAY AND SATURDAY, ALLOWING FOR MORE
OF A SOUTHEAST FLOW TO OCCUR. A PIECE OF ENERGY POSSIBLY
UNDERCUTTING THE BUILDING RIDGE MAY RESULT IN A SURFACE LOW
DEVELOPING OFF THE SOUTHEASTERN U.S. COAST OVER THE WEEKEND. IT
APPEARS THOUGH THE SURFACE HIGH REMAINS CLOSE ENOUGH TO OUR REGION,
WHICH WOULD NOT GENERATE MUCH OF A LONG ONSHORE FETCH FOR OUR AREA.
&&
.HYDROLOGY...
HEAVY RAIN...TIED TO A SHORT WAVE IN THE MID LEVELS HAS NOW MOVED
ACROSS THE AREA. THIS BATCH HAS SOME ELEVATED INSTABILITY ASSOCIATED
WITH IT...AND PRECIPITABLE WATER VALUES INCREASE TO NEAR 1.50
INCHES. THE SPECTER OF HEAVY RAIN IS STILL IN PLACE FOR THIS
BATCH...WHICH SHOULD CLEAR NORTHERN ZONES BY LATE MORNING OR EARLY
AFTERNOON.
WE WOULD PROBABLY NEED ANOTHER 1.50 TO 2.00 INCHES OF BASIN AVERAGE
RAINFALL ACROSS THE SOUTHERN POCONOS AND NORTHWEST NEW JERSEY BEFORE
PROBLEMS START (BASED ON THE LATEST HEADWATER GUIDANCE). WHILE NOT
OUT OF THE QUESTION DUE TO THE MOISTURE BLOB TO THE SOUTHWEST...IT
IS LOOKING LESS LIKELY THAN 24 HOURS AGO.
ONCE THAT SHOWER BATCH EXITS...CONVECTIVE ELEMENTS ARE POSSIBLE
LATER THIS AFTERNOON AND THIS EVENING. HOWEVER...IT DOES NOT APPEAR
AS THROUGH THE CONVECTION WILL BE WIDESPREAD ENOUGH TO POSE A
THREAT. THAT HAVING BEEN STATED...THERE ARE NO PLANS FOR HYDROLOGY
HEADLINES TODAY WITH RESPECT TO THE NEXT BATCH OF RAIN.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT WEDNESDAY FOR ANZ450>455.
&&
$$
SYNOPSIS...GORSE
NEAR TERM...HAYES/ROBERTSON
SHORT TERM...HAYES
LONG TERM...GORSE
AVIATION...GORSE/HAYES
MARINE...GIGI/GORSE/HAYES
HYDROLOGY...
000
FXUS61 KPHI 151349
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
949 AM EDT TUE MAY 15 2012
.SYNOPSIS...
A WEAK FRONTAL BOUNDARY REMAINS NEAR THE AREA THROUGH TODAY. A WEAK
LOW PRESSURE SYSTEM WILL TRACK ALONG THIS FRONT, WHICH WILL SHIFT
EAST OF OUR REGION TONIGHT INTO WEDNESDAY. A SECONDARY COLD FRONT
WILL THEN SWEEP ACROSS THE AREA LATER WEDNESDAY. HIGH PRESSURE THEN
BUILDS INTO THE REGION THURSDAY AND FRIDAY, BEFORE SHIFTING INTO NEW
ENGLAND AND THE CANADIAN MARITIMES LATER SATURDAY AND SUNDAY. A LOW
PRESSURE SYSTEM MAY DEVELOP OFF THE SOUTHEASTERN UNITED STATES COAST
DURING THE WEEKEND AND EARLY NEXT WEEK.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
HEAVY RAIN IS MOVING THROUGH THE AREA NOW ASSOCIATED WITH A SHORT
WAVE/VORT MAX CROSSING THE AREA. THERE IS SOME INSTABILITY IN THE
ATMOSPHERE, SO THERE HAS BEEN SOME OCCASIONAL STRIKES OF
LIGHTNING ASSOCIATED WITH THE RAINFALL. THE ATMOSPHERE REMAINS
MOIST WITH PWATS AROUND 1.5 INCHES, SO THERE IS HEAVY RAINFALL
ASSOCIATED WITH THESE SHOWERS AND ISOLATED THUNDERSTORMS. THE GOOD
NEWS IS THE RAIN IS MOVING AT A STEADY PACE TO THE NORTHEAST.
AMOUNTS WITH THIS AREA OF RAIN SHOULD BE AROUND ONE-HALF OF AN
INCH, WITH SOME LOCALLY HIGHER AMOUNTS. WITH THESE AMOUNTS, WE
WILL HAVE PONDING ON ROAD WAYS AND STANDING WATER IN LOW LYING AND
URBAN AREAS. THE GRIDS WERE UPDATED FOR THE NEXT SEVERAL HOURS TO
FOLLOW THIS AREA OF RAINFALL, WHICH SHOULD EXIT THE AREA LATER
THIS MORNING OR EARLY THIS AFTERNOON.
AFTER THE SHORT WAVE EXITS EARLY THIS AFTERNOON...THERE COULD BE A
FAIRLY SUBSTANTIAL BREAK IN THE RAIN. WHILE THE AIRMASS REMAINS
MOIST (PRECIPITABLE WATER VALUES DO NOT CHANGE MUCH)...IT COULD BE
THAT LACK OF AN ORGANIZING TRIGGER THAT LOWER RAIN SHOWER CHANCES.
IN FACT...THERE IS SOME HINT THAT THE CLOUDS COULD BREAK FOR SOME
SUNSHINE THIS AFTERNOON...ESPECIALLY ACROSS WESTERN AREAS.
THE SUNSHINE COULD HELP WITH DESTABILIZATION OF AN ALREADY
MARGINALLY UNSTABLE AIRMASS. THE BEST INSTABILITY SHOULD LIE JUST
WEST OF THE AREA...WHERE BREAKS IN THE CLOUDS ARE MORE LIKELY. IN
THIS AREA...THE BEST BULK SHEAR PROBABLY EXITS WITH THE SHORT WAVE
THIS AFTERNOON...THOUGH SHEAR COULD REMAIN BORDERLINE INTO THE
EVENING. MID LEVEL LAPSE RATES APPEAR AS THOUGH THEY WILL BE
MARGINAL AT BEST AS WELL.
SO...AT THIS POINT...THE BEST CHANCE OF THUNDERSTORM DEVELOPS LOOKS
TO BE JUST WEST OF THE AREA...OR ACROSS THE LEHIGH VALLEY. MODIFIED
MODEL SOUNDINGS WEST OF THE DELAWARE RIVER SHOW MARGINAL
INSTABILITY...MARGINAL SHEAR...AND RELATIVELY LOW MEAN LAYER CAPE
VALUES. THIS WOULD SUGGEST SCATTERED THUNDERSTORMS ACROSS WESTERN
AREAS THIS AFTERNOON AND THIS EVENING.. THERE IS A LOW POTENTIAL FOR
GUSTY WINDS (SOME MID LEVEL DRYING AND INCREASING DELTA EPT VALUES)
AND SMALL HAIL (WET BULB ZERO VALUES NEAR 9500 FEET). HOWEVER...
SINCE MOST MODIFIED SOUNDINGS SHOW A TALL THIN CAPE (SUGGESTING
SHORT LIVED CONVECTIVE CELLS)...NO ENHANCED WORDING WILL BE ADDED AT
THIS TIME.
THE HIGH TEMPERATURE FORECAST WILL BE TIED TO THE AMOUNT OF CLEARING
TODAY (IF ANY SIGNIFICANT CLEARING CAN OCCUR). FOR NOW...HIGHS WERE
BASED MAINLY ON THE MOS BLEND...DUE TO LOW CONFIDENCE LEVELS. RIGHT
NOW...THE HIGHER GFS MOS NUMBERS APPEAR TOO HIGH...BUT MORE BREAKS
COULD EASILY SEND HIGHS TO THOSE LEVELS.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM WEDNESDAY/...
THE POTENTIAL FOR EVENING CONVECTION STANDS AS THE BEST CHANCE FOR
MEANINGFUL RAIN CHANCES FOR THIS PERIOD. SCATTERED SHOWERS AND
THUNDERSTORMS SHOULD BE CLOSE TO THE DELAWARE RIVER THIS EVENING. AS
THE BEST INSTABILITY IS EXHAUSTED...THE SHOWERS AND THUNDERSTORMS
SHOULD WEAKEN AS THEY MOVE EAST. THE LAST OF WHATEVER IS LEFT COULD
REACH THE COAST BY ABOUT 0500 UTC.
AFTER THIS...THERE MAY NOT BE MUCH IN THE WAY OF SHOWER ACTIVITY
OVERNIGHT. THE 0000 UTC NAM DOES SHOW SOME PRECIPITATION NEAR THE
NEW JERSEY COAST (OSTENSIBLY ASSOCIATED WITH A WEAK WARM FRONT THAT
ARRIVES FROM THE NORTH CAROLINA COAST). THE 0000 GFS TAKES THIS
OFFSHORE...AND FOR NOW THIS SOLUTION IS ACCEPTED.
THE CLOUD COVER FORECAST MAY ALSO BE A PROBLEM. THERE COULD BE
BREAKS THIS EVENING...BUT MOS GUIDANCE SUGGESTS THIS IS PAVED OVER
BY LOW CLOUDS. THIS IS ACCEPTED FOR NOW...BUT COULD BE OVERDONE ON A
SOUTH TO SOUTHWEST BOUNDARY LAYER FLOW. AT THIS POINT...WILL NOT HIT
THE FOG HARD...BUT AREAS THAT DO GET RAIN TODAY COULD SEE PATCHY FOG
TONIGHT...ESPECIALLY WITH CLOUDS BREAKS. FOR THE MOST PART...LOWS
WERE BASED ON THE MOS BLEND.
&&
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
THE OVERALL SYNOPTIC SETUP IS COMPRISED OF A TROUGH AMPLIFYING
ACROSS EASTERN CANADA AND INTO THE NORTHEAST WEDNESDAY INTO
THURSDAY. THIS FEATURE THEN STARTS TO LIFT OUT LATER THURSDAY AS
RIDGING IN THE MIDWEST SLIDES EASTWARD WHILE A TROUGH DIGS ACROSS
THE WEST. THE MAIN SENSIBLE WEATHER ACROSS OUR AREA IS WEDNESDAY,
WHICH IS TIED TO THE AMPLIFYING TROUGH AND ASSOCIATED SURFACE COLD
FRONT. THE PATTERN THEN TRANSITIONS TO MORE OF A RIDGE BUILDING INTO
THE EAST AS THE TROUGH SETTLES ACROSS THE WEST AND EVENTUALLY INTO
THE PLAINS. A POTENTIAL FLY IN THE OINTMENT THOUGH IS A POCKET OF
ENERGY THAT MAY UNDERCUT THE BUILDING RIDGE AND GET STUCK NEAR THE
SOUTHEASTERN U.S. COAST THIS WEEKEND AND EARLY NEXT WEEK. THIS MAY
LEAD TO AN UPPER-LEVEL LOW AND SURFACE LOW REFLECTION, ALTHOUGH
THERE IS MORE UNCERTAINTY WITH THIS EVOLUTION.
FOR WEDNESDAY, THE MAIN MOISTURE PLUME AND SHORT WAVE ENERGY WILL BE
SHIFTING TO OUR NORTHEAST TO START THE DAY THEREFORE PERHAPS SOME
SHOWERS EARLY ON. AS THE UPPER-LEVEL TROUGH HOWEVER AMPLIFIES INTO
THE NORTHEAST, A SURFACE COLD FRONT WILL SWEEP ACROSS OUR AREA BY
MID EVENING. THERE IS SOME CONVECTIVE POTENTIAL ALONG AND AHEAD OF
THIS SECONDARY COLD FRONT, HOWEVER THE COVERAGE AND INTENSITY WILL
DEPEND ON A FEW THINGS INCLUDING THE AMOUNT OF INSTABILITY.
THE DAY MAY START WITH SOME FOG AND LOW CLOUDS, BUT ENOUGH BOUNDARY
LAYER HEATING SHOULD RESULT IN AT LEAST SOME SUNSHINE DEVELOPING
ALONG WITH BETTER MIXING LEADING TO STEEPENING LOW-LEVEL LAPSE RATES.
THE MODEL GUIDANCE DEVELOPS INSTABILITY ACROSS THE REGION, WITH A
MORE PRONOUNCED INSTABILITY AXIS NOTED MOSTLY ACROSS THE WESTERN
HALF OF THE CWA. WHILE THERE COULD BE SOME SHOWERS AND THUNDER
WITHIN THIS ZONE, WE MAY HAVE TO WAIT FOR THE MAIN COLD FRONT TO
ARRIVE TO HELP FOCUS ANY CONVECTION. THE AIRMASS IS FORECAST TO DRY
OUT ESPECIALLY IN THE MID LEVELS, ALTHOUGH THE SURFACE DEW POINTS
MAY LOWER SOME DURING THE DAY WITH IMPROVED MIXING, AND THE SHEAR
DOES INCREASE AHEAD OF THE FRONT. IF THE FORCING IS STRONG ENOUGH
AND WE REACH OUR FORECAST HIGHS, LOCALLY STRONG CONVECTION COULD
DEVELOP BUT THIS MAY NOT BE REAL ORGANIZED. BASED ON THE FORECAST
SOUNDINGS, THE MOSTLY UNIDIRECTIONAL FLOW FROM THE SOUTHWEST BEING
PRESENT MAY ALLOW FOR A FEW CONVECTIVE LINES IF MORE ROBUST
UPDRAFTS CAN BE SUSTAINED. THIS MAY FAVOR LOCALLY GUSTY WINDS AND
SOME HAIL WITH ANY STRONGER CONVECTIVE CORES. WE WILL CARRY LOW CHC
POPS ACROSS THE AREA FOR SCATTERED SHOWERS AND THUNDERSTORMS AHEAD
OF THE FRONT, BUT NOT INCLUDE ANY ENHANCED WORDING IN THE FORECAST
ATTM DUE TO UNCERTAINTY IN THE CONVECTIVE EVOLUTION. WE WILL HOWEVER
CONTINUE A MENTION IN THE HAZARDOUS WEATHER OUTLOOK. THE POPS
QUICKLY LOWER AND END DURING THE EVENING AS THE FRONT CLEARS THE
REGION AND DRIER AIR ADVECTS IN. THE WINDS WILL SHIFT TO THE
NORTHWEST AND NORTH FOLLOWING THE COLD FRONTAL PASSAGE.
FOR THURSDAY AND FRIDAY, THE UPPER-LEVEL TROUGH BEGINS TO LIFT
NORTHEASTWARD THURSDAY AND HIGH PRESSURE ARRIVES FROM THE WEST. AS
MID LEVEL RIDGING GRADUALLY SLIDES EASTWARD, THE SURFACE HIGH WILL
TEND TO RELOCATE OFF THE NEW ENGLAND COAST BUT STILL EXTEND DOWN
INTO THE MID ATLANTIC. THIS WILL RESULT IN LIGHT WINDS AND MILD
TEMPERATURES, ALTHOUGH THE LACK OF A PRESSURE GRADIENT WILL PROBABLY
LEAD TO SEA BREEZE CIRCULATIONS DEVELOPING ESPECIALLY FRIDAY
AFTERNOON.
FOR SATURDAY AND SUNDAY, HIGH PRESSURE FROM THE MID ATLANTIC TO NEAR
THE CANADIAN MARITIMES WILL REMAIN NEARLY STATIONARY. HOWEVER, THE
UPPER-LEVEL RIDGE NEARS THE EAST COAST SUNDAY WHICH WOULD PUSH THE
SURFACE HIGH A BIT TO THE EAST ALLOWING FOR MORE OF A RETURN FLOW TO
DEVELOP. INTERESTINGLY ENOUGH, SOME OF THE MODEL GUIDANCE DEVELOPS
DIURNAL CONVECTION NEAR THE OUTER EDGE OF THE UPPER-LEVEL RIDGE.
THIS LOOKS TO BE TIED MORE TO TERRAIN CIRCULATIONS, WHICH SOME
DEVELOPMENT GETS VERY CLOSE TO OUR NORTHWEST ZONES. GIVEN THE
PLACEMENT OF THE RIDGE, THINK THE CHC OF THIS IS RATHER LOW ATTM
THEREFORE WE MAINTAINED A DRY FORECAST. SOME OF THE MODEL GUIDANCE
SUGGEST THAT ENERGY UNDERCUTTING THE RIDGE BECOMES CUT OFF AND TENDS
TO SPIN UP A SURFACE LOW IN THE VICINITY OF THE SOUTHEASTERN U.S.
COAST. THIS FEATURE MAY END UP REMAINING WEAK, WHICH WOULD LEAD TO
MORE UNCERTAINTY REGARDING ITS MOVEMENT. AT THIS POINT GIVEN THE
RIDGE FORECAST TO BE IN PLACE TO THE NORTH, WE ARE NOT ANTICIPATING
ANY REAL IMPACTS FROM THIS POTENTIAL DEVELOPMENT.
FOR MONDAY, THE ENTIRE RIDGE AND SURFACE HIGH ARE NUDGED FARTHER TO
OUR EAST AS SOME TROUGHING PUSHES THROUGH THE GREAT LAKES REGION.
THIS WILL SEND A COLD FRONT EASTBOUND, HOWEVER THIS LOOKS TO STAY
FAIRLY FAR TO OUR WEST DURING THIS TIME FRAME. THE MILD CONDITIONS
WILL CONTINUE THOUGH GIVEN A RETURN FLOW OCCURRING.
&&
.AVIATION /14Z TUESDAY THROUGH SATURDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.
CONDITIONS ARE VARIABLE ACROSS THE AREA EARLY THIS MORNING...BUT FOR
THE MOST PART VFR CONDITIONS CONTINUE AT MOST LOCATIONS. LOCAL
SOUNDINGS SUGGEST THAT THE LOWER LEVELS HAVE NOT YET SUFFICIENTLY
SATURATED FOR MORE WIDESPREAD MVFR/IFR CONDITIONS.
THE FORECAST REMAINS TRICKY...AS STATISTICAL GUIDANCE SUGGESTS A LOW
DESCENT INTO MVFR AND LOCAL IFR CONDITIONS. FOR NOW...THIS TREND WAS
SLOWED...AS OBSERVATIONS DO NOT SUPPORT DROPPING AS QUICKLY AS
GUIDANCE. MOST LOCATIONS WERE DROPPED TO MVFR BEFORE 1100 UTC...AND
SHOULD REMAIN THERE UNTIL ABOUT 1600 OR 1700 UTC.
AFTER THIS...CONDITIONS MAY TRY TO IMPROVE TO NEAR VFR...ESPECIALLY
SOUTH AND EAST OF KPHL. CONSIDERING HOW SLOWLY CONDITIONS HAVE BEEN
TO DROP...THIS DOES NOT SEEM IMPLAUSIBLE...BUT CONFIDENCE IN VFR
CONDITIONS THIS AFTERNOON IS STILL LOW. SCATTERED THUNDERSTORMS MAY
TRY TO FROM WEST OF THE AREA THIS AFTERNOON...AND COULD IMPACT KPHL
METRO TERMINALS AFTER 0000 UTC. HOWEVER...CONFIDENCE WAS NOT HIGH
ENOUGH FOR INCLUSION IN THE 0600 UTC TERMINAL FORECASTS.
AFTER THE POTENTIAL FOR CONVECTION EXITS...CONDITIONS SHOULD SETTLE
BACK TO MVFR AFTER 0300 UTC WEDNESDAY. STATISTICAL GUIDANCE SUGGEST
CONDITIONS COULD LOWER TO IFR...BUT FOR NOW THIS WAS NOT INCLUDED IN
THE FORECAST.
OUTLOOK...
WEDNESDAY...SUB-VFR POSSIBLE TO START DUE TO LOW CLOUDS OR FOG, THEN
IMPROVING TO VFR. A FEW SHOWERS OR THUNDERSTORMS ARE POSSIBLE WITH
LOCAL AND BRIEF SUB-VFR INTO THE EARLY EVENING. VFR AT NIGHT AS THE
WINDS SHIFT TO THE NORTH.
THURSDAY AND FRIDAY...VFR WITH NORTHERLY WINDS UP TO KNOTS THURSDAY
POSSIBLY BECOME VARIABLE BY EVENING. LIGHT WINDS ESPECIALLY FRIDAY
MAY RESULT IN SEA AND/OR BAY BREEZES.
SATURDAY...VFR WITH LIGHT WINDS BECOMING SOUTHERLY NEAR 10 KNOTS.
&&
.MARINE...
SMALL CRAFT ADVISORY ISSUED FOR DELAWARE BAY AS WINDS ARE FUNNELING
UP IT AND THE KDOX VWP SHOWING 25 KTS. WE USED THE 06Z NAM FCST OF
THE LLJ TO END IT DURING THE AFTERNOON.
THE SOUTHEAST SOUTHEAST FLOW PROBABLY DOES NOT INCREASE THAT MUCH
TODAY...AND WIND SPEEDS ARE EXPECTED TO REMAIN MAINLY BELOW SMALL
CRAFT LEVELS. SEAS HAVE JUST STARTED TO REACH SMALL CRAFT ADVISORY
LEVELS AND THIS SHOULD SPREAD AS THE DAY PROGRESSES.
WINDS MAY TEND TO DROP OFF LATER TONIGHT AS THE SURFACE GRADIENT
BACKS OFF AHEAD OF A WEAK COLD FRONT TO THE WEST. AGAIN THE
FORECAST QUESTION FOR TONIGHT IS WHETHER SEAS GET TO/MAINTAIN SMALL
CRAFT CRITERION. FOR NOW...WILL CONTINUE WITH THE SAME FORECAST
RATIONALE FOR TONIGHT.
OUTLOOK...
THE SOUTHERLY FLOW PRIOR TO A COLD FRONTAL PASSAGE LATER WEDNESDAY
MAY RESULT IN SEAS ON THE OCEAN AROUND 5 FEET. THE SEAS HAVE BEEN
SLOW TO RESPONSE SO FAR IN THE SOUTHERLY FLOW IN THE NEAR TERM,
THEREFORE WE DECIDED NOT TO EXTEND THE SMALL CRAFT ADVISORY INTO
WEDNESDAY AT THIS POINT. THE COLD FRONT SWEEPS EAST OF THE REGION
WEDNESDAY EVENING WITH A NORTHERLY FLOW OCCURRING. THIS DOES NOT
APPEAR STRONG ENOUGH TO GENERATE SMALL CRAFT CONDITIONS CAUSED BY
EITHER SEAS OR WINDS. HIGH PRESSURE THEN SETTLES IN THURSDAY AND
FRIDAY, ALTHOUGH THE NORTHERLY WINDS MAY TEND TO TURN ONSHORE AS THE
FLOW WEAKENS AND POSSIBLE SEA BREEZE CIRCULATIONS DEVELOP. THE
SURFACE HIGH BUILDS EASTWARD FRIDAY AND SATURDAY, ALLOWING FOR MORE
OF A SOUTHEAST FLOW TO OCCUR. A PIECE OF ENERGY POSSIBLY
UNDERCUTTING THE BUILDING RIDGE MAY RESULT IN A SURFACE LOW
DEVELOPING OFF THE SOUTHEASTERN U.S. COAST OVER THE WEEKEND. IT
APPEARS THOUGH THE SURFACE HIGH REMAINS CLOSE ENOUGH TO OUR REGION,
WHICH WOULD NOT GENERATE MUCH OF A LONG ONSHORE FETCH FOR OUR AREA.
&&
.HYDROLOGY...
HEAVY RAIN...TIED TO A SHORT WAVE IN THE MID LEVELS HAS NOW MOVED
ACROSS THE AREA. THIS BATCH HAS SOME ELEVATED INSTABILITY ASSOCIATED
WITH IT...AND PRECIPITABLE WATER VALUES INCREASE TO NEAR 1.50
INCHES. THE SPECTER OF HEAVY RAIN IS STILL IN PLACE FOR THIS
BATCH...WHICH SHOULD CLEAR NORTHERN ZONES BY LATE MORNING OR EARLY
AFTERNOON.
WE WOULD PROBABLY NEED ANOTHER 1.50 TO 2.00 INCHES OF BASIN AVERAGE
RAINFALL ACROSS THE SOUTHERN POCONOS AND NORTHWEST NEW JERSEY BEFORE
PROBLEMS START (BASED ON THE LATEST HEADWATER GUIDANCE). WHILE NOT
OUT OF THE QUESTION DUE TO THE MOISTURE BLOB TO THE SOUTHWEST...IT
IS LOOKING LESS LIKELY THAN 24 HOURS AGO.
ONCE THAT SHOWER BATCH EXITS...CONVECTIVE ELEMENTS ARE POSSIBLE
LATER THIS AFTERNOON AND THIS EVENING. HOWEVER...IT DOES NOT APPEAR
AS THROUGH THE CONVECTION WILL BE WIDESPREAD ENOUGH TO POSE A
THREAT. THAT HAVING BEEN STATED...THERE ARE NO PLANS FOR HYDROLOGY
HEADLINES TODAY WITH RESPECT TO THE NEXT BATCH OF RAIN.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT WEDNESDAY FOR ANZ450>455.
SMALL CRAFT ADVISORY UNTIL 4 PM EDT THIS AFTERNOON FOR ANZ430-
431.
&&
$$
SYNOPSIS...GORSE
NEAR TERM...HAYES/ROBERTSON
SHORT TERM...HAYES
LONG TERM...GORSE
AVIATION...GORSE/HAYES
MARINE...GIGI/GORSE/HAYES
HYDROLOGY...HAYES
000
FXUS61 KPHI 151216
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
816 AM EDT TUE MAY 15 2012
.SYNOPSIS...
A WEAK FRONTAL BOUNDARY REMAINS NEAR THE AREA THROUGH TODAY. A WEAK
LOW PRESSURE SYSTEM WILL TRACK ALONG THIS FRONT, WHICH WILL SHIFT
EAST OF OUR REGION TONIGHT INTO WEDNESDAY. A SECONDARY COLD FRONT
WILL THEN SWEEP ACROSS THE AREA LATER WEDNESDAY. HIGH PRESSURE THEN
BUILDS INTO THE REGION THURSDAY AND FRIDAY, BEFORE SHIFTING INTO NEW
ENGLAND AND THE CANADIAN MARITIMES LATER SATURDAY AND SUNDAY. A LOW
PRESSURE SYSTEM MAY DEVELOP OFF THE SOUTHEASTERN UNITED STATES COAST
DURING THE WEEKEND AND EARLY NEXT WEEK.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
THE NEXT BATCH OF POTENTIALLY SIGNIFICANT RAIN EXTENDED FROM THE
NORTHERN VIRGINIA DOWN INTO NORTH CENTRAL NORTH CAROLINA...AHEAD
OF A SHORT WAVE. THE AIRMASS IS FAIRLY MOIST (0000 UTC SOUNDINGS
SHOWED PRECIPITABLE WATER VALUES NEAR 1.40 INCHES) AND POSSESSES
SOME INSTABILITY. THE CONVECTION IS DEVELOPING/HOLDING TOGETHER
ACROSS SOUTHEAST VIRGINIA...AND IS JUST ABOUT TO MOVE INTO
SOUTHERN MARYLAND. SINCE THERE IS MORE LIGHTNING THAN EARLIER
ANTICIPATED WITH THIS BATCH...THE FORECAST WAS UPDATED TO BEEF UP
THE MENTION OF THUNDER IN NORTHEAST MARYLAND...DELAWARE AND
SOUTHERNMOST NEW JERSEY. AT THIS POINT...LOCALLY HEAVY RAIN
APPEARS TO BE THE MAIN THREAT...WITH NOT MUCH IN THE WAY OF WIND
WITH THE STORMS (BASED ON SURFACE OBSERVATIONS).
THE AREA HAS SOME COLD CLOUD TOPS ON THE IR IMAGE...BUT IS HAS NOT
COOLED MUCH IN THE PAST COUPLE OF HOURS. EXTRAPOLATION OF THE SHORT
WAVE BRINGS IT JUST WEST OF THE AREA LATER THIS MORNING...EXITING
THE AREA EARLY THIS AFTERNOON. SHORT TERM MODELS SHOW AS MUCH AS
1.50 INCHES OF RAIN WITH THIS AREA AS IT CROSSES THE WESTERN LEHIGH
VALLEY...AS WELL AS THE SOUTHERN POCONOS AND NORTHWEST NEW JERSEY.
WHILE THERE IS CERTAINLY THE POTENTIAL FOR HEAVY RAIN WITH THIS
SHORT WAVE (GIVEN THE MOISTURE AND INSTABILITY CURRENTLY AVAILABLE)
IT APPEARS AS THOUGH THE HEAVIEST RAIN WILL FALL WEST OF THE AREA.
WITH THIS IN MIND...NO HYDROLOGY HEADLINES ARE ANTICIPATED THIS
MORNING. MORE IN THE POTENTIAL HAS BEEN INCLUDED IN THE HYDROLOGY
SECTION BELOW.
AFTER THE SHORT WAVE EXITS EARLY THIS AFTERNOON...THERE COULD BE A
FAIRLY SUBSTANTIAL BREAK IN THE RAIN. WHILE THE AIRMASS REMAINS
MOIST (PRECIPITABLE WATER VALUES DO NOT CHANGE MUCH)...IT COULD BE
THAT LACK OF AN ORGANIZING TRIGGER THAT LOWER RAIN SHOWER CHANCES.
IN FACT...THERE IS SOME HINT THAT THE CLOUDS COULD BREAK FOR SOME
SUNSHINE THIS AFTERNOON...ESPECIALLY ACROSS WESTERN AREAS.
THE SUNSHINE COULD HELP WITH DESTABILIZATION OF AN ALREADY
MARGINALLY UNSTABLE AIRMASS. THE BEST INSTABILITY SHOULD LIE JUST
WEST OF THE AREA...WHERE BREAKS IN THE CLOUDS ARE MORE LIKELY. IN
THIS AREA...THE BEST BULK SHEAR PROBABLY EXITS WITH THE SHORT WAVE
THIS AFTERNOON...THOUGH SHEAR COULD REMAIN BORDERLINE INTO THE
EVENING. MID LEVEL LAPSE RATES APPEAR AS THOUGH THEY WILL BE
MARGINAL AT BEST AS WELL.
SO...AT THIS POINT...THE BEST CHANCE OF THUNDERSTORM DEVELOPS LOOKS
TO BE JUST WEST OF THE AREA...OR ACROSS THE LEHIGH VALLEY. MODIFIED
MODEL SOUNDINGS WEST OF THE DELAWARE RIVER SHOW MARGINAL
INSTABILITY...MARGINAL SHEAR...AND RELATIVELY LOW MEAN LAYER CAPE
VALUES. THIS WOULD SUGGEST SCATTERED THUNDERSTORMS ACROSS WESTERN
AREAS THIS AFTERNOON AND THIS EVENING.. THERE IS A LOW POTENTIAL FOR
GUSTY WINDS (SOME MID LEVEL DRYING AND INCREASING DELTA EPT VALUES)
AND SMALL HAIL (WET BULB ZERO VALUES NEAR 9500 FEET). HOWEVER...
SINCE MOST MODIFIED SOUNDINGS SHOW A TALL THIN CAPE (SUGGESTING
SHORT LIVED CONVECTIVE CELLS)...NO ENHANCED WORDING WILL BE ADDED AT
THIS TIME.
THE HIGH TEMPERATURE FORECAST WILL BE TIED TO THE AMOUNT OF CLEARING
TODAY (IF ANY SIGNIFICANT CLEARING CAN OCCUR). FOR NOW...HIGHS WERE
BASED MAINLY ON THE MOS BLEND...DUE TO LOW CONFIDENCE LEVELS. RIGHT
NOW...THE HIGHER GFS MOS NUMBERS APPEAR TOO HIGH...BUT MORE BREAKS
COULD EASILY SEND HIGHS TO THOSE LEVELS.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM WEDNESDAY/...
THE POTENTIAL FOR EVENING CONVECTION STANDS AS THE BEST CHANCE FOR
MEANINGFUL RAIN CHANCES FOR THIS PERIOD. SCATTERED SHOWERS AND
THUNDERSTORMS SHOULD BE CLOSE TO THE DELAWARE RIVER THIS EVENING. AS
THE BEST INSTABILITY IS EXHAUSTED...THE SHOWERS AND THUNDERSTORMS
SHOULD WEAKEN AS THEY MOVE EAST. THE LAST OF WHATEVER IS LEFT COULD
REACH THE COAST BY ABOUT 0500 UTC.
AFTER THIS...THERE MAY NOT BE MUCH IN THE WAY OF SHOWER ACTIVITY
OVERNIGHT. THE 0000 UTC NAM DOES SHOW SOME PRECIPITATION NEAR THE
NEW JERSEY COAST (OSTENSIBLY ASSOCIATED WITH A WEAK WARM FRONT THAT
ARRIVES FROM THE NORTH CAROLINA COAST). THE 0000 GFS TAKES THIS
OFFSHORE...AND FOR NOW THIS SOLUTION IS ACCEPTED.
THE CLOUD COVER FORECAST MAY ALSO BE A PROBLEM. THERE COULD BE
BREAKS THIS EVENING...BUT MOS GUIDANCE SUGGESTS THIS IS PAVED OVER
BY LOW CLOUDS. THIS IS ACCEPTED FOR NOW...BUT COULD BE OVERDONE ON A
SOUTH TO SOUTHWEST BOUNDARY LAYER FLOW. AT THIS POINT...WILL NOT HIT
THE FOG HARD...BUT AREAS THAT DO GET RAIN TODAY COULD SEE PATCHY FOG
TONIGHT...ESPECIALLY WITH CLOUDS BREAKS. FOR THE MOST PART...LOWS
WERE BASED ON THE MOS BLEND.
&&
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
THE OVERALL SYNOPTIC SETUP IS COMPRISED OF A TROUGH AMPLIFYING
ACROSS EASTERN CANADA AND INTO THE NORTHEAST WEDNESDAY INTO
THURSDAY. THIS FEATURE THEN STARTS TO LIFT OUT LATER THURSDAY AS
RIDGING IN THE MIDWEST SLIDES EASTWARD WHILE A TROUGH DIGS ACROSS
THE WEST. THE MAIN SENSIBLE WEATHER ACROSS OUR AREA IS WEDNESDAY,
WHICH IS TIED TO THE AMPLIFYING TROUGH AND ASSOCIATED SURFACE COLD
FRONT. THE PATTERN THEN TRANSITIONS TO MORE OF A RIDGE BUILDING INTO
THE EAST AS THE TROUGH SETTLES ACROSS THE WEST AND EVENTUALLY INTO
THE PLAINS. A POTENTIAL FLY IN THE OINTMENT THOUGH IS A POCKET OF
ENERGY THAT MAY UNDERCUT THE BUILDING RIDGE AND GET STUCK NEAR THE
SOUTHEASTERN U.S. COAST THIS WEEKEND AND EARLY NEXT WEEK. THIS MAY
LEAD TO AN UPPER-LEVEL LOW AND SURFACE LOW REFLECTION, ALTHOUGH
THERE IS MORE UNCERTAINTY WITH THIS EVOLUTION.
FOR WEDNESDAY, THE MAIN MOISTURE PLUME AND SHORT WAVE ENERGY WILL BE
SHIFTING TO OUR NORTHEAST TO START THE DAY THEREFORE PERHAPS SOME
SHOWERS EARLY ON. AS THE UPPER-LEVEL TROUGH HOWEVER AMPLIFIES INTO
THE NORTHEAST, A SURFACE COLD FRONT WILL SWEEP ACROSS OUR AREA BY
MID EVENING. THERE IS SOME CONVECTIVE POTENTIAL ALONG AND AHEAD OF
THIS SECONDARY COLD FRONT, HOWEVER THE COVERAGE AND INTENSITY WILL
DEPEND ON A FEW THINGS INCLUDING THE AMOUNT OF INSTABILITY.
THE DAY MAY START WITH SOME FOG AND LOW CLOUDS, BUT ENOUGH BOUNDARY
LAYER HEATING SHOULD RESULT IN AT LEAST SOME SUNSHINE DEVELOPING
ALONG WITH BETTER MIXING LEADING TO STEEPENING LOW-LEVEL LAPSE RATES.
THE MODEL GUIDANCE DEVELOPS INSTABILITY ACROSS THE REGION, WITH A
MORE PRONOUNCED INSTABILITY AXIS NOTED MOSTLY ACROSS THE WESTERN
HALF OF THE CWA. WHILE THERE COULD BE SOME SHOWERS AND THUNDER
WITHIN THIS ZONE, WE MAY HAVE TO WAIT FOR THE MAIN COLD FRONT TO
ARRIVE TO HELP FOCUS ANY CONVECTION. THE AIRMASS IS FORECAST TO DRY
OUT ESPECIALLY IN THE MID LEVELS, ALTHOUGH THE SURFACE DEW POINTS
MAY LOWER SOME DURING THE DAY WITH IMPROVED MIXING, AND THE SHEAR
DOES INCREASE AHEAD OF THE FRONT. IF THE FORCING IS STRONG ENOUGH
AND WE REACH OUR FORECAST HIGHS, LOCALLY STRONG CONVECTION COULD
DEVELOP BUT THIS MAY NOT BE REAL ORGANIZED. BASED ON THE FORECAST
SOUNDINGS, THE MOSTLY UNIDIRECTIONAL FLOW FROM THE SOUTHWEST BEING
PRESENT MAY ALLOW FOR A FEW CONVECTIVE LINES IF MORE ROBUST
UPDRAFTS CAN BE SUSTAINED. THIS MAY FAVOR LOCALLY GUSTY WINDS AND
SOME HAIL WITH ANY STRONGER CONVECTIVE CORES. WE WILL CARRY LOW CHC
POPS ACROSS THE AREA FOR SCATTERED SHOWERS AND THUNDERSTORMS AHEAD
OF THE FRONT, BUT NOT INCLUDE ANY ENHANCED WORDING IN THE FORECAST
ATTM DUE TO UNCERTAINTY IN THE CONVECTIVE EVOLUTION. WE WILL HOWEVER
CONTINUE A MENTION IN THE HAZARDOUS WEATHER OUTLOOK. THE POPS
QUICKLY LOWER AND END DURING THE EVENING AS THE FRONT CLEARS THE
REGION AND DRIER AIR ADVECTS IN. THE WINDS WILL SHIFT TO THE
NORTHWEST AND NORTH FOLLOWING THE COLD FRONTAL PASSAGE.
FOR THURSDAY AND FRIDAY, THE UPPER-LEVEL TROUGH BEGINS TO LIFT
NORTHEASTWARD THURSDAY AND HIGH PRESSURE ARRIVES FROM THE WEST. AS
MID LEVEL RIDGING GRADUALLY SLIDES EASTWARD, THE SURFACE HIGH WILL
TEND TO RELOCATE OFF THE NEW ENGLAND COAST BUT STILL EXTEND DOWN
INTO THE MID ATLANTIC. THIS WILL RESULT IN LIGHT WINDS AND MILD
TEMPERATURES, ALTHOUGH THE LACK OF A PRESSURE GRADIENT WILL PROBABLY
LEAD TO SEA BREEZE CIRCULATIONS DEVELOPING ESPECIALLY FRIDAY
AFTERNOON.
FOR SATURDAY AND SUNDAY, HIGH PRESSURE FROM THE MID ATLANTIC TO NEAR
THE CANADIAN MARITIMES WILL REMAIN NEARLY STATIONARY. HOWEVER, THE
UPPER-LEVEL RIDGE NEARS THE EAST COAST SUNDAY WHICH WOULD PUSH THE
SURFACE HIGH A BIT TO THE EAST ALLOWING FOR MORE OF A RETURN FLOW TO
DEVELOP. INTERESTINGLY ENOUGH, SOME OF THE MODEL GUIDANCE DEVELOPS
DIURNAL CONVECTION NEAR THE OUTER EDGE OF THE UPPER-LEVEL RIDGE.
THIS LOOKS TO BE TIED MORE TO TERRAIN CIRCULATIONS, WHICH SOME
DEVELOPMENT GETS VERY CLOSE TO OUR NORTHWEST ZONES. GIVEN THE
PLACEMENT OF THE RIDGE, THINK THE CHC OF THIS IS RATHER LOW ATTM
THEREFORE WE MAINTAINED A DRY FORECAST. SOME OF THE MODEL GUIDANCE
SUGGEST THAT ENERGY UNDERCUTTING THE RIDGE BECOMES CUT OFF AND TENDS
TO SPIN UP A SURFACE LOW IN THE VICINITY OF THE SOUTHEASTERN U.S.
COAST. THIS FEATURE MAY END UP REMAINING WEAK, WHICH WOULD LEAD TO
MORE UNCERTAINTY REGARDING ITS MOVEMENT. AT THIS POINT GIVEN THE
RIDGE FORECAST TO BE IN PLACE TO THE NORTH, WE ARE NOT ANTICIPATING
ANY REAL IMPACTS FROM THIS POTENTIAL DEVELOPMENT.
FOR MONDAY, THE ENTIRE RIDGE AND SURFACE HIGH ARE NUDGED FARTHER TO
OUR EAST AS SOME TROUGHING PUSHES THROUGH THE GREAT LAKES REGION.
THIS WILL SEND A COLD FRONT EASTBOUND, HOWEVER THIS LOOKS TO STAY
FAIRLY FAR TO OUR WEST DURING THIS TIME FRAME. THE MILD CONDITIONS
WILL CONTINUE THOUGH GIVEN A RETURN FLOW OCCURRING.
&&
.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.
CONDITIONS ARE VARIABLE ACROSS THE AREA EARLY THIS MORNING...BUT FOR
THE MOST PART VFR CONDITIONS CONTINUE AT MOST LOCATIONS. LOCAL
SOUNDINGS SUGGEST THAT THE LOWER LEVELS HAVE NOT YET SUFFICIENTLY
SATURATED FOR MORE WIDESPREAD MVFR/IFR CONDITIONS.
THE FORECAST REMAINS TRICKY...AS STATISTICAL GUIDANCE SUGGESTS A LOW
DESCENT INTO MVFR AND LOCAL IFR CONDITIONS. FOR NOW...THIS TREND WAS
SLOWED...AS OBSERVATIONS DO NOT SUPPORT DROPPING AS QUICKLY AS
GUIDANCE. MOST LOCATIONS WERE DROPPED TO MVFR BEFORE 1100 UTC...AND
SHOULD REMAIN THERE UNTIL ABOUT 1600 OR 1700 UTC.
AFTER THIS...CONDITIONS MAY TRY TO IMPROVE TO NEAR VFR...ESPECIALLY
SOUTH AND EAST OF KPHL. CONSIDERING HOW SLOWLY CONDITIONS HAVE BEEN
TO DROP...THIS DOES NOT SEEM IMPLAUSIBLE...BUT CONFIDENCE IN VFR
CONDITIONS THIS AFTERNOON IS STILL LOW. SCATTERED THUNDERSTORMS MAY
TRY TO FROM WEST OF THE AREA THIS AFTERNOON...AND COULD IMPACT KPHL
METRO TERMINALS AFTER 0000 UTC. HOWEVER...CONFIDENCE WAS NOT HIGH
ENOUGH FOR INCLUSION IN THE 0600 UTC TERMINAL FORECASTS.
AFTER THE POTENTIAL FOR CONVECTION EXITS...CONDITIONS SHOULD SETTLE
BACK TO MVFR AFTER 0300 UTC WEDNESDAY. STATISTICAL GUIDANCE SUGGEST
CONDITIONS COULD LOWER TO IFR...BUT FOR NOW THIS WAS NOT INCLUDED IN
THE FORECAST.
OUTLOOK...
WEDNESDAY...SUB-VFR POSSIBLE TO START DUE TO LOW CLOUDS OR FOG, THEN
IMPROVING TO VFR. A FEW SHOWERS OR THUNDERSTORMS ARE POSSIBLE WITH
LOCAL AND BRIEF SUB-VFR INTO THE EARLY EVENING. VFR AT NIGHT AS THE
WINDS SHIFT TO THE NORTH.
THURSDAY AND FRIDAY...VFR WITH NORTHERLY WINDS UP TO KNOTS THURSDAY
POSSIBLY BECOME VARIABLE BY EVENING. LIGHT WINDS ESPECIALLY FRIDAY
MAY RESULT IN SEA AND/OR BAY BREEZES.
SATURDAY...VFR WITH LIGHT WINDS BECOMING SOUTHERLY NEAR 10 KNOTS.
&&
.MARINE...
SMALL CRAFT ADVISORY ISSUED FOR DELAWARE BAY AS WINDS ARE FUNNELING
UP IT AND THE KDOX VWP SHOWING 25 KTS. WE USED THE 06Z NAM FCST OF
THE LLJ TO END IT DURING THE AFTERNOON.
THE SOUTHEAST SOUTHEAST FLOW PROBABLY DOES NOT INCREASE THAT MUCH
TODAY...AND WIND SPEEDS ARE EXPECTED TO REMAIN MAINLY BELOW SMALL
CRAFT LEVELS. SEAS HAVE JUST STARTED TO REACH SMALL CRAFT ADVISORY
LEVELS AND THIS SHOULD SPREAD AS THE DAY PROGRESSES.
WINDS MAY TEND TO DROP OFF LATER TONIGHT AS THE SURFACE GRADIENT
BACKS OFF AHEAD OF A WEAK COLD FRONT TO THE WEST. AGAIN THE
FORECAST QUESTION FOR TONIGHT IS WHETHER SEAS GET TO/MAINTAIN SMALL
CRAFT CRITERION. FOR NOW...WILL CONTINUE WITH THE SAME FORECAST
RATIONALE FOR TONIGHT.
OUTLOOK...
THE SOUTHERLY FLOW PRIOR TO A COLD FRONTAL PASSAGE LATER WEDNESDAY
MAY RESULT IN SEAS ON THE OCEAN AROUND 5 FEET. THE SEAS HAVE BEEN
SLOW TO RESPONSE SO FAR IN THE SOUTHERLY FLOW IN THE NEAR TERM,
THEREFORE WE DECIDED NOT TO EXTEND THE SMALL CRAFT ADVISORY INTO
WEDNESDAY AT THIS POINT. THE COLD FRONT SWEEPS EAST OF THE REGION
WEDNESDAY EVENING WITH A NORTHERLY FLOW OCCURRING. THIS DOES NOT
APPEAR STRONG ENOUGH TO GENERATE SMALL CRAFT CONDITIONS CAUSED BY
EITHER SEAS OR WINDS. HIGH PRESSURE THEN SETTLES IN THURSDAY AND
FRIDAY, ALTHOUGH THE NORTHERLY WINDS MAY TEND TO TURN ONSHORE AS THE
FLOW WEAKENS AND POSSIBLE SEA BREEZE CIRCULATIONS DEVELOP. THE
SURFACE HIGH BUILDS EASTWARD FRIDAY AND SATURDAY, ALLOWING FOR MORE
OF A SOUTHEAST FLOW TO OCCUR. A PIECE OF ENERGY POSSIBLY
UNDERCUTTING THE BUILDING RIDGE MAY RESULT IN A SURFACE LOW
DEVELOPING OFF THE SOUTHEASTERN U.S. COAST OVER THE WEEKEND. IT
APPEARS THOUGH THE SURFACE HIGH REMAINS CLOSE ENOUGH TO OUR REGION,
WHICH WOULD NOT GENERATE MUCH OF A LONG ONSHORE FETCH FOR OUR AREA.
&&
.HYDROLOGY...
THE FIRST BATCH OF RAIN HAS MOVED TO THE NORTHEAST OF THE AREA.
THROUGH 0500 UTC...ONE-HALF TO ONE INCH OF RAIN HAD FALLEN ACROSS
THE SOUTHERN POCONOS AND NORTHWEST NEW JERSEY...WITH LESSER AMOUNTS
TO THE SOUTHEAST.
THE NEXT BATCH OF RAIN...TIED TO A SHORT WAVE IN THE MID LEVELS OVER
CENTRAL NORTH CAROLINA EARLY THIS MORNING...SHOULD ARRIVE ACROSS
SOUTHWEST AREAS AFTER 1000 UTC. THIS BATCH HAS SOME ELEVATED
INSTABILITY ASSOCIATED WITH IT...AND PRECIPITABLE WATER VALUES
INCREASE TO NEAR 1.50 INCHES. THE SPECTER OF HEAVY RAIN IS STILL IN
PLACE FOR THIS BATCH...WHICH SHOULD CLEAR NORTHERN ZONES BY LATE
MORNING OR EARLY AFTERNOON.
WE WOULD PROBABLY NEED ANOTHER 1.50 TO 2.00 INCHES OF BASIN AVERAGE
RAINFALL ACROSS THE SOUTHERN POCONOS AND NORTHWEST NEW JERSEY BEFORE
PROBLEMS START (BASED ON THE LATEST HEADWATER GUIDANCE). WHILE NOT
OUT OF THE QUESTION DUE TO THE MOISTURE BLOB TO THE SOUTHWEST...IT
IS LOOKING LESS LIKELY THAN 24 HOURS AGO.
ONCE THAT SHOWER BATCH EXITS...CONVECTIVE ELEMENTS ARE POSSIBLE
LATER THIS AFTERNOON AND THIS EVENING. HOWEVER...IT DOES NOT APPEAR
AS THROUGH THE CONVECTION WILL BE WIDESPREAD ENOUGH TO POSE A
THREAT. THAT HAVING BEEN STATED...THERE ARE NO PLANS FOR HYDROLOGY
HEADLINES TODAY WITH RESPECT TO THE NEXT BATCH OF RAIN.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT WEDNESDAY FOR ANZ450>455.
SMALL CRAFT ADVISORY UNTIL 4 PM EDT THIS AFTERNOON FOR ANZ430-
431.
&&
$$
SYNOPSIS...GORSE
NEAR TERM...HAYES
SHORT TERM...HAYES
LONG TERM...GORSE
AVIATION...GORSE/HAYES
MARINE...GIGI/GORSE/HAYES
HYDROLOGY...
000
FXUS61 KPHI 150929
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
529 AM EDT TUE MAY 15 2012
.SYNOPSIS...
A WEAK FRONTAL BOUNDARY REMAINS NEAR THE AREA THROUGH TODAY. A WEAK
LOW PRESSURE SYSTEM WILL TRACK ALONG THIS FRONT, WHICH WILL SHIFT
EAST OF OUR REGION TONIGHT INTO WEDNESDAY. A SECONDARY COLD FRONT
WILL THEN SWEEP ACROSS THE AREA LATER WEDNESDAY. HIGH PRESSURE THEN
BUILDS INTO THE REGION THURSDAY AND FRIDAY, BEFORE SHIFTING INTO NEW
ENGLAND AND THE CANADIAN MARITIMES LATER SATURDAY AND SUNDAY. A LOW
PRESSURE SYSTEM MAY DEVELOP OFF THE SOUTHEASTERN UNITED STATES COAST
DURING THE WEEKEND AND EARLY NEXT WEEK.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
THE NEXT BATCH OF POTENTIALLY SIGNIFICANT RAIN EXTENDED FROM THE
NORTHERN VIRGINIA DOWN INTO NORTH CENTRAL NORTH CAROLINA...AHEAD
OF A SHORT WAVE. THE AIRMASS IS FAIRLY MOIST (0000 UTC SOUNDINGS
SHOWED PRECIPITABLE WATER VALUES NEAR 1.40 INCHES) AND POSSESSES
SOME INSTABILITY. THE CONVECTION IS DEVELOPING/HOLDING TOGETHER
ACROSS SOUTHEAST VIRGINIA...AND IS JUST ABOUT TO MOVE INTO
SOUTHERN MARYLAND. SINCE THERE IS MORE LIGHTNING THAN EARLIER
ANTICIPATED WITH THIS BATCH...THE FORECAST WAS UPDATED TO BEEF UP
THE MENTION OF THUNDER IN NORTHEAST MARYLAND...DELAWARE AND
SOUTHERNMOST NEW JERSEY. AT THIS POINT...LOCALLY HEAVY RAIN
APPEARS TO BE THE MAIN THREAT...WITH NOT MUCH IN THE WAY OF WIND
WITH THE STORMS (BASED ON SURFACE OBSERVATIONS).
THE AREA HAS SOME COLD CLOUD TOPS ON THE IR IMAGE...BUT IS HAS NOT
COOLED MUCH IN THE PAST COUPLE OF HOURS. EXTRAPOLATION OF THE SHORT
WAVE BRINGS IT JUST WEST OF THE AREA LATER THIS MORNING...EXITING
THE AREA EARLY THIS AFTERNOON. SHORT TERM MODELS SHOW AS MUCH AS
1.50 INCHES OF RAIN WITH THIS AREA AS IT CROSSES THE WESTERN LEHIGH
VALLEY...AS WELL AS THE SOUTHERN POCONOS AND NORTHWEST NEW JERSEY.
WHILE THERE IS CERTAINLY THE POTENTIAL FOR HEAVY RAIN WITH THIS
SHORT WAVE (GIVEN THE MOISTURE AND INSTABILITY CURRENTLY AVAILABLE)
IT APPEARS AS THOUGH THE HEAVIEST RAIN WILL FALL WEST OF THE AREA.
WITH THIS IN MIND...NO HYDROLOGY HEADLINES ARE ANTICIPATED THIS
MORNING. MORE IN THE POTENTIAL HAS BEEN INCLUDED IN THE HYDROLOGY
SECTION BELOW.
AFTER THE SHORT WAVE EXITS EARLY THIS AFTERNOON...THERE COULD BE A
FAIRLY SUBSTANTIAL BREAK IN THE RAIN. WHILE THE AIRMASS REMAINS
MOIST (PRECIPITABLE WATER VALUES DO NOT CHANGE MUCH)...IT COULD BE
THAT LACK OF AN ORGANIZING TRIGGER THAT LOWER RAIN SHOWER CHANCES.
IN FACT...THERE IS SOME HINT THAT THE CLOUDS COULD BREAK FOR SOME
SUNSHINE THIS AFTERNOON...ESPECIALLY ACROSS WESTERN AREAS.
THE SUNSHINE COULD HELP WITH DESTABILIZATION OF AN ALREADY
MARGINALLY UNSTABLE AIRMASS. THE BEST INSTABILITY SHOULD LIE JUST
WEST OF THE AREA...WHERE BREAKS IN THE CLOUDS ARE MORE LIKELY. IN
THIS AREA...THE BEST BULK SHEAR PROBABLY EXITS WITH THE SHORT WAVE
THIS AFTERNOON...THOUGH SHEAR COULD REMAIN BORDERLINE INTO THE
EVENING. MID LEVEL LAPSE RATES APPEAR AS THOUGH THEY WILL BE
MARGINAL AT BEST AS WELL.
SO...AT THIS POINT...THE BEST CHANCE OF THUNDERSTORM DEVELOPS LOOKS
TO BE JUST WEST OF THE AREA...OR ACROSS THE LEHIGH VALLEY. MODIFIED
MODEL SOUNDINGS WEST OF THE DELAWARE RIVER SHOW MARGINAL
INSTABILITY...MARGINAL SHEAR...AND RELATIVELY LOW MEAN LAYER CAPE
VALUES. THIS WOULD SUGGEST SCATTERED THUNDERSTORMS ACROSS WESTERN
AREAS THIS AFTERNOON AND THIS EVENING.. THERE IS A LOW POTENTIAL FOR
GUSTY WINDS (SOME MID LEVEL DRYING AND INCREASING DELTA EPT VALUES)
AND SMALL HAIL (WET BULB ZERO VALUES NEAR 9500 FEET). HOWEVER...
SINCE MOST MODIFIED SOUNDINGS SHOW A TALL THIN CAPE (SUGGESTING
SHORT LIVED CONVECTIVE CELLS)...NO ENHANCED WORDING WILL BE ADDED AT
THIS TIME.
THE HIGH TEMPERATURE FORECAST WILL BE TIED TO THE AMOUNT OF CLEARING
TODAY (IF ANY SIGNIFICANT CLEARING CAN OCCUR). FOR NOW...HIGHS WERE
BASED MAINLY ON THE MOS BLEND...DUE TO LOW CONFIDENCE LEVELS. RIGHT
NOW...THE HIGHER GFS MOS NUMBERS APPEAR TOO HIGH...BUT MORE BREAKS
COULD EASILY SEND HIGHS TO THOSE LEVELS.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM WEDNESDAY/...
THE POTENTIAL FOR EVENING CONVECTION STANDS AS THE BEST CHANCE FOR
MEANINGFUL RAIN CHANCES FOR THIS PERIOD. SCATTERED SHOWERS AND
THUNDERSTORMS SHOULD BE CLOSE TO THE DELAWARE RIVER THIS EVENING. AS
THE BEST INSTABILITY IS EXHAUSTED...THE SHOWERS AND THUNDERSTORMS
SHOULD WEAKEN AS THEY MOVE EAST. THE LAST OF WHATEVER IS LEFT COULD
REACH THE COAST BY ABOUT 0500 UTC.
AFTER THIS...THERE MAY NOT BE MUCH IN THE WAY OF SHOWER ACTIVITY
OVERNIGHT. THE 0000 UTC NAM DOES SHOW SOME PRECIPITATION NEAR THE
NEW JERSEY COAST (OSTENSIBLY ASSOCIATED WITH A WEAK WARM FRONT THAT
ARRIVES FROM THE NORTH CAROLINA COAST). THE 0000 GFS TAKES THIS
OFFSHORE...AND FOR NOW THIS SOLUTION IS ACCEPTED.
THE CLOUD COVER FORECAST MAY ALSO BE A PROBLEM. THERE COULD BE
BREAKS THIS EVENING...BUT MOS GUIDANCE SUGGESTS THIS IS PAVED OVER
BY LOW CLOUDS. THIS IS ACCEPTED FOR NOW...BUT COULD BE OVERDONE ON A
SOUTH TO SOUTHWEST BOUNDARY LAYER FLOW. AT THIS POINT...WILL NOT HIT
THE FOG HARD...BUT AREAS THAT DO GET RAIN TODAY COULD SEE PATCHY FOG
TONIGHT...ESPECIALLY WITH CLOUDS BREAKS. FOR THE MOST PART...LOWS
WERE BASED ON THE MOS BLEND.
&&
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
THE OVERALL SYNOPTIC SETUP IS COMPRISED OF A TROUGH AMPLIFYING
ACROSS EASTERN CANADA AND INTO THE NORTHEAST WEDNESDAY INTO
THURSDAY. THIS FEATURE THEN STARTS TO LIFT OUT LATER THURSDAY AS
RIDGING IN THE MIDWEST SLIDES EASTWARD WHILE A TROUGH DIGS ACROSS
THE WEST. THE MAIN SENSIBLE WEATHER ACROSS OUR AREA IS WEDNESDAY,
WHICH IS TIED TO THE AMPLIFYING TROUGH AND ASSOCIATED SURFACE COLD
FRONT. THE PATTERN THEN TRANSITIONS TO MORE OF A RIDGE BUILDING INTO
THE EAST AS THE TROUGH SETTLES ACROSS THE WEST AND EVENTUALLY INTO
THE PLAINS. A POTENTIAL FLY IN THE OINTMENT THOUGH IS A POCKET OF
ENERGY THAT MAY UNDERCUT THE BUILDING RIDGE AND GET STUCK NEAR THE
SOUTHEASTERN U.S. COAST THIS WEEKEND AND EARLY NEXT WEEK. THIS MAY
LEAD TO AN UPPER-LEVEL LOW AND SURFACE LOW REFLECTION, ALTHOUGH
THERE IS MORE UNCERTAINTY WITH THIS EVOLUTION.
FOR WEDNESDAY, THE MAIN MOISTURE PLUME AND SHORT WAVE ENERGY WILL BE
SHIFTING TO OUR NORTHEAST TO START THE DAY THEREFORE PERHAPS SOME
SHOWERS EARLY ON. AS THE UPPER-LEVEL TROUGH HOWEVER AMPLIFIES INTO
THE NORTHEAST, A SURFACE COLD FRONT WILL SWEEP ACROSS OUR AREA BY
MID EVENING. THERE IS SOME CONVECTIVE POTENTIAL ALONG AND AHEAD OF
THIS SECONDARY COLD FRONT, HOWEVER THE COVERAGE AND INTENSITY WILL
DEPEND ON A FEW THINGS INCLUDING THE AMOUNT OF INSTABILITY.
THE DAY MAY START WITH SOME FOG AND LOW CLOUDS, BUT ENOUGH BOUNDARY
LAYER HEATING SHOULD RESULT IN AT LEAST SOME SUNSHINE DEVELOPING
ALONG WITH BETTER MIXING LEADING TO STEEPENING LOW-LEVEL LAPSE RATES.
THE MODEL GUIDANCE DEVELOPS INSTABILITY ACROSS THE REGION, WITH A
MORE PRONOUNCED INSTABILITY AXIS NOTED MOSTLY ACROSS THE WESTERN
HALF OF THE CWA. WHILE THERE COULD BE SOME SHOWERS AND THUNDER
WITHIN THIS ZONE, WE MAY HAVE TO WAIT FOR THE MAIN COLD FRONT TO
ARRIVE TO HELP FOCUS ANY CONVECTION. THE AIRMASS IS FORECAST TO DRY
OUT ESPECIALLY IN THE MID LEVELS, ALTHOUGH THE SURFACE DEW POINTS
MAY LOWER SOME DURING THE DAY WITH IMPROVED MIXING, AND THE SHEAR
DOES INCREASE AHEAD OF THE FRONT. IF THE FORCING IS STRONG ENOUGH
AND WE REACH OUR FORECAST HIGHS, LOCALLY STRONG CONVECTION COULD
DEVELOP BUT THIS MAY NOT BE REAL ORGANIZED. BASED ON THE FORECAST
SOUNDINGS, THE MOSTLY UNIDIRECTIONAL FLOW FROM THE SOUTHWEST BEING
PRESENT MAY ALLOW FOR A FEW CONVECTIVE LINES IF MORE ROBUST
UPDRAFTS CAN BE SUSTAINED. THIS MAY FAVOR LOCALLY GUSTY WINDS AND
SOME HAIL WITH ANY STRONGER CONVECTIVE CORES. WE WILL CARRY LOW CHC
POPS ACROSS THE AREA FOR SCATTERED SHOWERS AND THUNDERSTORMS AHEAD
OF THE FRONT, BUT NOT INCLUDE ANY ENHANCED WORDING IN THE FORECAST
ATTM DUE TO UNCERTAINTY IN THE CONVECTIVE EVOLUTION. WE WILL HOWEVER
CONTINUE A MENTION IN THE HAZARDOUS WEATHER OUTLOOK. THE POPS
QUICKLY LOWER AND END DURING THE EVENING AS THE FRONT CLEARS THE
REGION AND DRIER AIR ADVECTS IN. THE WINDS WILL SHIFT TO THE
NORTHWEST AND NORTH FOLLOWING THE COLD FRONTAL PASSAGE.
FOR THURSDAY AND FRIDAY, THE UPPER-LEVEL TROUGH BEGINS TO LIFT
NORTHEASTWARD THURSDAY AND HIGH PRESSURE ARRIVES FROM THE WEST. AS
MID LEVEL RIDGING GRADUALLY SLIDES EASTWARD, THE SURFACE HIGH WILL
TEND TO RELOCATE OFF THE NEW ENGLAND COAST BUT STILL EXTEND DOWN
INTO THE MID ATLANTIC. THIS WILL RESULT IN LIGHT WINDS AND MILD
TEMPERATURES, ALTHOUGH THE LACK OF A PRESSURE GRADIENT WILL PROBABLY
LEAD TO SEA BREEZE CIRCULATIONS DEVELOPING ESPECIALLY FRIDAY
AFTERNOON.
FOR SATURDAY AND SUNDAY, HIGH PRESSURE FROM THE MID ATLANTIC TO NEAR
THE CANADIAN MARITIMES WILL REMAIN NEARLY STATIONARY. HOWEVER, THE
UPPER-LEVEL RIDGE NEARS THE EAST COAST SUNDAY WHICH WOULD PUSH THE
SURFACE HIGH A BIT TO THE EAST ALLOWING FOR MORE OF A RETURN FLOW TO
DEVELOP. INTERESTINGLY ENOUGH, SOME OF THE MODEL GUIDANCE DEVELOPS
DIURNAL CONVECTION NEAR THE OUTER EDGE OF THE UPPER-LEVEL RIDGE.
THIS LOOKS TO BE TIED MORE TO TERRAIN CIRCULATIONS, WHICH SOME
DEVELOPMENT GETS VERY CLOSE TO OUR NORTHWEST ZONES. GIVEN THE
PLACEMENT OF THE RIDGE, THINK THE CHC OF THIS IS RATHER LOW ATTM
THEREFORE WE MAINTAINED A DRY FORECAST. SOME OF THE MODEL GUIDANCE
SUGGEST THAT ENERGY UNDERCUTTING THE RIDGE BECOMES CUT OFF AND TENDS
TO SPIN UP A SURFACE LOW IN THE VICINITY OF THE SOUTHEASTERN U.S.
COAST. THIS FEATURE MAY END UP REMAINING WEAK, WHICH WOULD LEAD TO
MORE UNCERTAINTY REGARDING ITS MOVEMENT. AT THIS POINT GIVEN THE
RIDGE FORECAST TO BE IN PLACE TO THE NORTH, WE ARE NOT ANTICIPATING
ANY REAL IMPACTS FROM THIS POTENTIAL DEVELOPMENT.
FOR MONDAY, THE ENTIRE RIDGE AND SURFACE HIGH ARE NUDGED FARTHER TO
OUR EAST AS SOME TROUGHING PUSHES THROUGH THE GREAT LAKES REGION.
THIS WILL SEND A COLD FRONT EASTBOUND, HOWEVER THIS LOOKS TO STAY
FAIRLY FAR TO OUR WEST DURING THIS TIME FRAME. THE MILD CONDITIONS
WILL CONTINUE THOUGH GIVEN A RETURN FLOW OCCURRING.
&&
.AVIATION /10Z TUESDAY THROUGH SATURDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.
CONDITIONS ARE VARIABLE ACROSS THE AREA EARLY THIS MORNING...BUT FOR
THE MOST PART VFR CONDITIONS CONTINUE AT MOST LOCATIONS. LOCAL
SOUNDINGS SUGGEST THAT THE LOWER LEVELS HAVE NOT YET SUFFICIENTLY
SATURATED FOR MORE WIDESPREAD MVFR/IFR CONDITIONS.
THE FORECAST REMAINS TRICKY...AS STATISTICAL GUIDANCE SUGGESTS A LOW
DESCENT INTO MVFR AND LOCAL IFR CONDITIONS. FOR NOW...THIS TREND WAS
SLOWED...AS OBSERVATIONS DO NOT SUPPORT DROPPING AS QUICKLY AS
GUIDANCE. MOST LOCATIONS WERE DROPPED TO MVFR BEFORE 1100 UTC...AND
SHOULD REMAIN THERE UNTIL ABOUT 1600 OR 1700 UTC.
AFTER THIS...CONDITIONS MAY TRY TO IMPROVE TO NEAR VFR...ESPECIALLY
SOUTH AND EAST OF KPHL. CONSIDERING HOW SLOWLY CONDITIONS HAVE BEEN
TO DROP...THIS DOES NOT SEEM IMPLAUSIBLE...BUT CONFIDENCE IN VFR
CONDITIONS THIS AFTERNOON IS STILL LOW. SCATTERED THUNDERSTORMS MAY
TRY TO FROM WEST OF THE AREA THIS AFTERNOON...AND COULD IMPACT KPHL
METRO TERMINALS AFTER 0000 UTC. HOWEVER...CONFIDENCE WAS NOT HIGH
ENOUGH FOR INCLUSION IN THE 0600 UTC TERMINAL FORECASTS.
AFTER THE POTENTIAL FOR CONVECTION EXITS...CONDITIONS SHOULD SETTLE
BACK TO MVFR AFTER 0300 UTC WEDNESDAY. STATISTICAL GUIDANCE SUGGEST
CONDITIONS COULD LOWER TO IFR...BUT FOR NOW THIS WAS NOT INCLUDED IN
THE FORECAST.
OUTLOOK...
WEDNESDAY...SUB-VFR POSSIBLE TO START DUE TO LOW CLOUDS OR FOG, THEN
IMPROVING TO VFR. A FEW SHOWERS OR THUNDERSTORMS ARE POSSIBLE WITH
LOCAL AND BRIEF SUB-VFR INTO THE EARLY EVENING. VFR AT NIGHT AS THE
WINDS SHIFT TO THE NORTH.
THURSDAY AND FRIDAY...VFR WITH NORTHERLY WINDS UP TO KNOTS THURSDAY
POSSIBLY BECOME VARIABLE BY EVENING. LIGHT WINDS ESPECIALLY FRIDAY
MAY RESULT IN SEA AND/OR BAY BREEZES.
SATURDAY...VFR WITH LIGHT WINDS BECOMING SOUTHERLY NEAR 10 KNOTS.
&&
.MARINE...
WELL...THE SOUTHERLY FETCH WAS NOT ENOUGH TO DEVELOP SEAS AS
EXPECTED MONDAY AFTERNOON OR EVENING. TYPICALLY IT IS TOUGH FOR
MOMENTUM TO MIX DOWN IN THE SOUTHERLY FLOW (AS THE DEPTH OF THE
MARINE MIXED LAYER IS USUALLY LOW)...AND THIS WAS NO EXCEPTION.
THE SOUTHEAST SOUTHEAST FLOW PROBABLY DOES NOT INCREASE THAT MUCH
TODAY...AND WIND SPEEDS ARE EXPECTED TO REMAIN BELOW SMALL CRAFT
LEVELS. THE QUESTION BECOMES WHETHER SEAS ACTUALLY GET TO 5 FEET ON
THE OCEAN. WNAWAVE GUIDANCE SUGGESTS THIS WILL INDEED HAPPEN LATER
THIS MORNING OR EARLY THIS AFTERNOON. WITH SOME SKEPTICISM...THE
SMALL CRAFT ADVISORY WILL REMAIN IN PLACE FOR NOW. IT IS POSSIBLE...
HOWEVER...IT IS POSSIBLE SEAS MAY NOT QUITE MAKE IT...AND LATER
SHIFTS MAY BE ABLE TO TAKE THIS DOWN.
WINDS MAY TEND TO DROP OFF LATER TONIGHT AS THE SURFACE GRADIENT
BACKS OFF AHEAD OF A WEAK COLD FRONT TO THE WEST. AGAIN THE
FORECAST QUESTION FOR TONIGHT IS WHETHER SEAS GET TO/MAINTAIN SMALL
CRAFT CRITERION. FOR NOW...WILL CONTINUE WITH THE SAME FORECAST
RATIONALE FOR TONIGHT.
OUTLOOK...
THE SOUTHERLY FLOW PRIOR TO A COLD FRONTAL PASSAGE LATER WEDNESDAY
MAY RESULT IN SEAS ON THE OCEAN AROUND 5 FEET. THE SEAS HAVE BEEN
SLOW TO RESPONSE SO FAR IN THE SOUTHERLY FLOW IN THE NEAR TERM,
THEREFORE WE DECIDED NOT TO EXTEND THE SMALL CRAFT ADVISORY INTO
WEDNESDAY AT THIS POINT. THE COLD FRONT SWEEPS EAST OF THE REGION
WEDNESDAY EVENING WITH A NORTHERLY FLOW OCCURRING. THIS DOES NOT
APPEAR STRONG ENOUGH TO GENERATE SMALL CRAFT CONDITIONS CAUSED BY
EITHER SEAS OR WINDS. HIGH PRESSURE THEN SETTLES IN THURSDAY AND
FRIDAY, ALTHOUGH THE NORTHERLY WINDS MAY TEND TO TURN ONSHORE AS THE
FLOW WEAKENS AND POSSIBLE SEA BREEZE CIRCULATIONS DEVELOP. THE
SURFACE HIGH BUILDS EASTWARD FRIDAY AND SATURDAY, ALLOWING FOR MORE
OF A SOUTHEAST FLOW TO OCCUR. A PIECE OF ENERGY POSSIBLY
UNDERCUTTING THE BUILDING RIDGE MAY RESULT IN A SURFACE LOW
DEVELOPING OFF THE SOUTHEASTERN U.S. COAST OVER THE WEEKEND. IT
APPEARS THOUGH THE SURFACE HIGH REMAINS CLOSE ENOUGH TO OUR REGION,
WHICH WOULD NOT GENERATE MUCH OF A LONG ONSHORE FETCH FOR OUR AREA.
&&
.HYDROLOGY...
THE FIRST BATCH OF RAIN HAS MOVED TO THE NORTHEAST OF THE AREA.
THROUGH 0500 UTC...ONE-HALF TO ONE INCH OF RAIN HAD FALLEN ACROSS
THE SOUTHERN POCONOS AND NORTHWEST NEW JERSEY...WITH LESSER AMOUNTS
TO THE SOUTHEAST.
THE NEXT BATCH OF RAIN...TIED TO A SHORT WAVE IN THE MID LEVELS OVER
CENTRAL NORTH CAROLINA EARLY THIS MORNING...SHOULD ARRIVE ACROSS
SOUTHWEST AREAS AFTER 1000 UTC. THIS BATCH HAS SOME ELEVATED
INSTABILITY ASSOCIATED WITH IT...AND PRECIPITABLE WATER VALUES
INCREASE TO NEAR 1.50 INCHES. THE SPECTER OF HEAVY RAIN IS STILL IN
PLACE FOR THIS BATCH...WHICH SHOULD CLEAR NORTHERN ZONES BY LATE
MORNING OR EARLY AFTERNOON.
WE WOULD PROBABLY NEED ANOTHER 1.50 TO 2.00 INCHES OF BASIN AVERAGE
RAINFALL ACROSS THE SOUTHERN POCONOS AND NORTHWEST NEW JERSEY BEFORE
PROBLEMS START (BASED ON THE LATEST HEADWATER GUIDANCE). WHILE NOT
OUT OF THE QUESTION DUE TO THE MOISTURE BLOB TO THE SOUTHWEST...IT
IS LOOKING LESS LIKELY THAN 24 HOURS AGO.
ONCE THAT SHOWER BATCH EXITS...CONVECTIVE ELEMENTS ARE POSSIBLE
LATER THIS AFTERNOON AND THIS EVENING. HOWEVER...IT DOES NOT APPEAR
AS THROUGH THE CONVECTION WILL BE WIDESPREAD ENOUGH TO POSE A
THREAT. THAT HAVING BEEN STATED...THERE ARE NO PLANS FOR HYDROLOGY
HEADLINES TODAY WITH RESPECT TO THE NEXT BATCH OF RAIN.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT WEDNESDAY FOR ANZ450>455.
&&
$$
SYNOPSIS...GORSE
NEAR TERM...HAYES
SHORT TERM...HAYES
LONG TERM...GORSE
AVIATION...GORSE/HAYES
MARINE...GORSE/HAYES
HYDROLOGY...HAYES
000
FXUS61 KPHI 150737
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
337 AM EDT TUE MAY 15 2012
.SYNOPSIS...
A WEAK FRONTAL BOUNDARY REMAINS NEAR THE AREA THROUGH TODAY. A WEAK
LOW PRESSURE SYSTEM WILL TRACK ALONG THIS FRONT, WHICH WILL SHIFT
EAST OF OUR REGION TONIGHT INTO WEDNESDAY. A SECONDARY COLD FRONT
WILL THEN SWEEP ACROSS THE AREA LATER WEDNESDAY. HIGH PRESSURE THEN
BUILDS INTO THE REGION THURSDAY AND FRIDAY, BEFORE SHIFTING INTO NEW
ENGLAND AND THE CANADIAN MARITIMES LATER SATURDAY AND SUNDAY. A LOW
PRESSURE SYSTEM MAY DEVELOP OFF THE SOUTHEASTERN UNITED STATES COAST
DURING THE WEEKEND AND EARLY NEXT WEEK.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
THE FIRST BATCH OF SHOWERS HAS EXITED THE REGION...WITH SCATTERED
SHOWERS FALLING ACROSS THE WESTERN HALF OF THE AREA IN ITS WAKE. THE
NEXT BATCH OF POTENTIALLY SIGNIFICANT RAIN EXTENDED FROM THE NORTHERN
VIRGINIA DOWN INTO NORTH CENTRAL NORTH CAROLINA...AHEAD OF A SHORT
WAVE. THE AIRMASS IS FAIRLY MOIST (0000 UTC SOUNDINGS SHOWED
PRECIPITABLE WATER VALUES NEAR 1.40 INCHES) AND POSSESSES SOME
INSTABILITY.
THE AREA HAS SOME COLD CLOUD TOPS ON THE IR IMAGE...BUT IS HAS NOT
COOLED MUCH IN THE PAST COUPLE OF HOURS. EXTRAPOLATION OF THE SHORT
WAVE BRINGS IT JUST WEST OF THE AREA LATER THIS MORNING...EXITING
THE AREA EARLY THIS AFTERNOON. SHORT TERM MODELS SHOW AS MUCH AS
1.50 INCHES OF RAIN WITH THIS AREA AS IT CROSSES THE WESTERN LEHIGH
VALLEY...AS WELL AS THE SOUTHERN POCONOS AND NORTHWEST NEW JERSEY.
WHILE THERE IS CERTAINLY THE POTENTIAL FOR HEAVY RAIN WITH THIS
SHORT WAVE (GIVEN THE MOISTURE AND INSTABILITY CURRENTLY AVAILABLE)
IT APPEARS AS THOUGH THE HEAVIEST RAIN WILL FALL WEST OF THE AREA.
WITH THIS IN MIND...NO HYDROLOGY HEADLINES ARE ANTICIPATED THIS
MORNING. MORE IN THE POTENTIAL HAS BEEN INCLUDED IN THE HYDROLOGY
SECTION BELOW.
AFTER THE SHORT WAVE EXITS EARLY THIS AFTERNOON...THERE COULD BE A
FAIRLY SUBSTANTIAL BREAK IN THE RAIN. WHILE THE AIRMASS REMAINS
MOIST (PRECIPITABLE WATER VALUES DO NOT CHANGE MUCH)...IT COULD BE
THAT LACK OF AN ORGANIZING TRIGGER THAT LOWER RAIN SHOWER CHANCES.
IN FACT...THERE IS SOME HINT THAT THE CLOUDS COULD BREAK FOR SOME
SUNSHINE THIS AFTERNOON...ESPECIALLY ACROSS WESTERN AREAS.
THE SUNSHINE COULD HELP WITH DESTABILIZATION OF AN ALREADY
MARGINALLY UNSTABLE AIRMASS. THE BEST INSTABILITY SHOULD LIE JUST
WEST OF THE AREA...WHERE BREAKS IN THE CLOUDS ARE MORE LIKELY. IN
THIS AREA...THE BEST BULK SHEAR PROBABLY EXITS WITH THE SHORT WAVE
THIS AFTERNOON...THOUGH SHEAR COULD REMAIN BORDERLINE INTO THE
EVENING. MID LEVEL LAPSE RATES APPEAR AS THOUGH THEY WILL BE
MARGINAL AT BEST AS WELL.
SO...AT THIS POINT...THE BEST CHANCE OF THUNDERSTORM DEVELOPS LOOKS
TO BE JUST WEST OF THE AREA...OR ACROSS THE LEHIGH VALLEY. MODIFIED
MODEL SOUNDINGS WEST OF THE DELAWARE RIVER SHOW MARGINAL
INSTABILITY...MARGINAL SHEAR...AND RELATIVELY LOW MEAN LAYER CAPE
VALUES. THIS WOULD SUGGEST SCATTERED THUNDERSTORMS ACROSS WESTERN
AREAS THIS AFTERNOON AND THIS EVENING.. THERE IS A LOW POTENTIAL FOR
GUSTY WINDS (SOME MID LEVEL DRYING AND INCREASING DELTA EPT VALUES)
AND SMALL HAIL (WET BULB ZERO VALUES NEAR 9500 FEET). HOWEVER...
SINCE MOST MODIFIED SOUNDINGS SHOW A TALL THIN CAPE (SUGGESTING
SHORT LIVED CONVECTIVE CELLS)...NO ENHANCED WORDING WILL BE ADDED AT
THIS TIME.
THE HIGH TEMPERATURE FORECAST WILL BE TIED TO THE AMOUNT OF CLEARING
TODAY (IF ANY SIGNIFICANT CLEARING CAN OCCUR). FOR NOW...HIGHS WERE
BASED MAINLY ON THE MOS BLEND...DUE TO LOW CONFIDENCE LEVELS. RIGHT
NOW...THE HIGHER GFS MOS NUMBERS APPEAR TOO HIGH...BUT MORE BREAKS
COULD EASILY SEND HIGHS TO THOSE LEVELS.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM WEDNESDAY/...
THE POTENTIAL FOR EVENING CONVECTION STANDS AS THE BEST CHANCE FOR
MEANINGFUL RAIN CHANCES FOR THIS PERIOD. SCATTERED SHOWERS AND
THUNDERSTORMS SHOULD BE CLOSE TO THE DELAWARE RIVER THIS EVENING. AS
THE BEST INSTABILITY IS EXHAUSTED...THE SHOWERS AND THUNDERSTORMS
SHOULD WEAKEN AS THEY MOVE EAST. THE LAST OF WHATEVER IS LEFT COULD
REACH THE COAST BY ABOUT 0500 UTC.
AFTER THIS...THERE MAY NOT BE MUCH IN THE WAY OF SHOWER ACTIVITY
OVERNIGHT. THE 0000 UTC NAM DOES SHOW SOME PRECIPITATION NEAR THE
NEW JERSEY COAST (OSTENSIBLY ASSOCIATED WITH A WEAK WARM FRONT THAT
ARRIVES FROM THE NORTH CAROLINA COAST). THE 0000 GFS TAKES THIS
OFFSHORE...AND FOR NOW THIS SOLUTION IS ACCEPTED.
THE CLOUD COVER FORECAST MAY ALSO BE A PROBLEM. THERE COULD BE
BREAKS THIS EVENING...BUT MOS GUIDANCE SUGGESTS THIS IS PAVED OVER
BY LOW CLOUDS. THIS IS ACCEPTED FOR NOW...BUT COULD BE OVERDONE ON A
SOUTH TO SOUTHWEST BOUNDARY LAYER FLOW. AT THIS POINT...WILL NOT HIT
THE FOG HARD...BUT AREAS THAT DO GET RAIN TODAY COULD SEE PATCHY FOG
TONIGHT...ESPECIALLY WITH CLOUDS BREAKS. FOR THE MOST PART...LOWS
WERE BASED ON THE MOS BLEND.
&&
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
THE OVERALL SYNOPTIC SETUP IS COMPRISED OF A TROUGH AMPLIFYING
ACROSS EASTERN CANADA AND INTO THE NORTHEAST WEDNESDAY INTO
THURSDAY. THIS FEATURE THEN STARTS TO LIFT OUT LATER THURSDAY AS
RIDGING IN THE MIDWEST SLIDES EASTWARD WHILE A TROUGH DIGS ACROSS
THE WEST. THE MAIN SENSIBLE WEATHER ACROSS OUR AREA IS WEDNESDAY,
WHICH IS TIED TO THE AMPLIFYING TROUGH AND ASSOCIATED SURFACE COLD
FRONT. THE PATTERN THEN TRANSITIONS TO MORE OF A RIDGE BUILDING INTO
THE EAST AS THE TROUGH SETTLES ACROSS THE WEST AND EVENTUALLY INTO
THE PLAINS. A POTENTIAL FLY IN THE OINTMENT THOUGH IS A POCKET OF
ENERGY THAT MAY UNDERCUT THE BUILDING RIDGE AND GET STUCK NEAR THE
SOUTHEASTERN U.S. COAST THIS WEEKEND AND EARLY NEXT WEEK. THIS MAY
LEAD TO AN UPPER-LEVEL LOW AND SURFACE LOW REFLECTION, ALTHOUGH
THERE IS MORE UNCERTAINTY WITH THIS EVOLUTION.
FOR WEDNESDAY, THE MAIN MOISTURE PLUME AND SHORT WAVE ENERGY WILL BE
SHIFTING TO OUR NORTHEAST TO START THE DAY THEREFORE PERHAPS SOME
SHOWERS EARLY ON. AS THE UPPER-LEVEL TROUGH HOWEVER AMPLIFIES INTO
THE NORTHEAST, A SURFACE COLD FRONT WILL SWEEP ACROSS OUR AREA BY
MID EVENING. THERE IS SOME CONVECTIVE POTENTIAL ALONG AND AHEAD OF
THIS SECONDARY COLD FRONT, HOWEVER THE COVERAGE AND INTENSITY WILL
DEPEND ON A FEW THINGS INCLUDING THE AMOUNT OF INSTABILITY.
THE DAY MAY START WITH SOME FOG AND LOW CLOUDS, BUT ENOUGH BOUNDARY
LAYER HEATING SHOULD RESULT IN AT LEAST SOME SUNSHINE DEVELOPING
ALONG WITH BETTER MIXING LEADING TO STEEPENING LOW-LEVEL LAPSE RATES.
THE MODEL GUIDANCE DEVELOPS INSTABILITY ACROSS THE REGION, WITH A
MORE PRONOUNCED INSTABILITY AXIS NOTED MOSTLY ACROSS THE WESTERN
HALF OF THE CWA. WHILE THERE COULD BE SOME SHOWERS AND THUNDER
WITHIN THIS ZONE, WE MAY HAVE TO WAIT FOR THE MAIN COLD FRONT TO
ARRIVE TO HELP FOCUS ANY CONVECTION. THE AIRMASS IS FORECAST TO DRY
OUT ESPECIALLY IN THE MID LEVELS, ALTHOUGH THE SURFACE DEW POINTS
MAY LOWER SOME DURING THE DAY WITH IMPROVED MIXING, AND THE SHEAR
DOES INCREASE AHEAD OF THE FRONT. IF THE FORCING IS STRONG ENOUGH
AND WE REACH OUR FORECAST HIGHS, LOCALLY STRONG CONVECTION COULD
DEVELOP BUT THIS MAY NOT BE REAL ORGANIZED. BASED ON THE FORECAST
SOUNDINGS, THE MOSTLY UNIDIRECTIONAL FLOW FROM THE SOUTHWEST BEING
PRESENT MAY ALLOW FOR A FEW CONVECTIVE LINES IF MORE ROBUST
UPDRAFTS CAN BE SUSTAINED. THIS MAY FAVOR LOCALLY GUSTY WINDS AND
SOME HAIL WITH ANY STRONGER CONVECTIVE CORES. WE WILL CARRY LOW CHC
POPS ACROSS THE AREA FOR SCATTERED SHOWERS AND THUNDERSTORMS AHEAD
OF THE FRONT, BUT NOT INCLUDE ANY ENHANCED WORDING IN THE FORECAST
ATTM DUE TO UNCERTAINTY IN THE CONVECTIVE EVOLUTION. WE WILL HOWEVER
CONTINUE A MENTION IN THE HAZARDOUS WEATHER OUTLOOK. THE POPS
QUICKLY LOWER AND END DURING THE EVENING AS THE FRONT CLEARS THE
REGION AND DRIER AIR ADVECTS IN. THE WINDS WILL SHIFT TO THE
NORTHWEST AND NORTH FOLLOWING THE COLD FRONTAL PASSAGE.
FOR THURSDAY AND FRIDAY, THE UPPER-LEVEL TROUGH BEGINS TO LIFT
NORTHEASTWARD THURSDAY AND HIGH PRESSURE ARRIVES FROM THE WEST. AS
MID LEVEL RIDGING GRADUALLY SLIDES EASTWARD, THE SURFACE HIGH WILL
TEND TO RELOCATE OFF THE NEW ENGLAND COAST BUT STILL EXTEND DOWN
INTO THE MID ATLANTIC. THIS WILL RESULT IN LIGHT WINDS AND MILD
TEMPERATURES, ALTHOUGH THE LACK OF A PRESSURE GRADIENT WILL PROBABLY
LEAD TO SEA BREEZE CIRCULATIONS DEVELOPING ESPECIALLY FRIDAY
AFTERNOON.
FOR SATURDAY AND SUNDAY, HIGH PRESSURE FROM THE MID ATLANTIC TO NEAR
THE CANADIAN MARITIMES WILL REMAIN NEARLY STATIONARY. HOWEVER, THE
UPPER-LEVEL RIDGE NEARS THE EAST COAST SUNDAY WHICH WOULD PUSH THE
SURFACE HIGH A BIT TO THE EAST ALLOWING FOR MORE OF A RETURN FLOW TO
DEVELOP. INTERESTINGLY ENOUGH, SOME OF THE MODEL GUIDANCE DEVELOPS
DIURNAL CONVECTION NEAR THE OUTER EDGE OF THE UPPER-LEVEL RIDGE.
THIS LOOKS TO BE TIED MORE TO TERRAIN CIRCULATIONS, WHICH SOME
DEVELOPMENT GETS VERY CLOSE TO OUR NORTHWEST ZONES. GIVEN THE
PLACEMENT OF THE RIDGE, THINK THE CHC OF THIS IS RATHER LOW ATTM
THEREFORE WE MAINTAINED A DRY FORECAST. SOME OF THE MODEL GUIDANCE
SUGGEST THAT ENERGY UNDERCUTTING THE RIDGE BECOMES CUT OFF AND TENDS
TO SPIN UP A SURFACE LOW IN THE VICINITY OF THE SOUTHEASTERN U.S.
COAST. THIS FEATURE MAY END UP REMAINING WEAK, WHICH WOULD LEAD TO
MORE UNCERTAINTY REGARDING ITS MOVEMENT. AT THIS POINT GIVEN THE
RIDGE FORECAST TO BE IN PLACE TO THE NORTH, WE ARE NOT ANTICIPATING
ANY REAL IMPACTS FROM THIS POTENTIAL DEVELOPMENT.
FOR MONDAY, THE ENTIRE RIDGE AND SURFACE HIGH ARE NUDGED FARTHER TO
OUR EAST AS SOME TROUGHING PUSHES THROUGH THE GREAT LAKES REGION.
THIS WILL SEND A COLD FRONT EASTBOUND, HOWEVER THIS LOOKS TO STAY
FAIRLY FAR TO OUR WEST DURING THIS TIME FRAME. THE MILD CONDITIONS
WILL CONTINUE THOUGH GIVEN A RETURN FLOW OCCURRING.
&&
.AVIATION /08Z TUESDAY THROUGH SATURDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.
CONDITIONS ARE VARIABLE ACROSS THE AREA EARLY THIS MORNING...BUT FOR
THE MOST PART VFR CONDITIONS CONTINUE AT MOST LOCATIONS. LOCAL
SOUNDINGS SUGGEST THAT THE LOWER LEVELS HAVE NOT YET SUFFICIENTLY
SATURATED FOR MORE WIDESPREAD MVFR/IFR CONDITIONS.
THE FORECAST REMAINS TRICKY...AS STATISTICAL GUIDANCE SUGGESTS A LOW
DESCENT INTO MVFR AND LOCAL IFR CONDITIONS. FOR NOW...THIS TREND WAS
SLOWED...AS OBSERVATIONS DO NOT SUPPORT DROPPING AS QUICKLY AS
GUIDANCE. MOST LOCATIONS WERE DROPPED TO MVFR BEFORE 1100 UTC...AND
SHOULD REMAIN THERE UNTIL ABOUT 1600 OR 1700 UTC.
AFTER THIS...CONDITIONS MAY TRY TO IMPROVE TO NEAR VFR...ESPECIALLY
SOUTH AND EAST OF KPHL. CONSIDERING HOW SLOWLY CONDITIONS HAVE BEEN
TO DROP...THIS DOES NOT SEEM IMPLAUSIBLE...BUT CONFIDENCE IN VFR
CONDITIONS THIS AFTERNOON IS STILL LOW. SCATTERED THUNDERSTORMS MAY
TRY TO FROM WEST OF THE AREA THIS AFTERNOON...AND COULD IMPACT KPHL
METRO TERMINALS AFTER 0000 UTC. HOWEVER...CONFIDENCE WAS NOT HIGH
ENOUGH FOR INCLUSION IN THE 0600 UTC TERMINAL FORECASTS.
AFTER THE POTENTIAL FOR CONVECTION EXITS...CONDITIONS SHOULD SETTLE
BACK TO MVFR AFTER 0300 UTC WEDNESDAY. STATISTICAL GUIDANCE SUGGEST
CONDITIONS COULD LOWER TO IFR...BUT FOR NOW THIS WAS NOT INCLUDED IN
THE FORECAST.
OUTLOOK...
WEDNESDAY...SUB-VFR POSSIBLE TO START DUE TO LOW CLOUDS OR FOG, THEN
IMPROVING TO VFR. A FEW SHOWERS OR THUNDERSTORMS ARE POSSIBLE WITH
LOCAL AND BRIEF SUB-VFR INTO THE EARLY EVENING. VFR AT NIGHT AS THE
WINDS SHIFT TO THE NORTH.
THURSDAY AND FRIDAY...VFR WITH NORTHERLY WINDS UP TO KNOTS THURSDAY
POSSIBLY BECOME VARIABLE BY EVENING. LIGHT WINDS ESPECIALLY FRIDAY
MAY RESULT IN SEA AND/OR BAY BREEZES.
SATURDAY...VFR WITH LIGHT WINDS BECOMING SOUTHERLY NEAR 10 KNOTS.
&&
.MARINE...
WELL...THE SOUTHERLY FETCH WAS NOT ENOUGH TO DEVELOP SEAS AS
EXPECTED MONDAY AFTERNOON OR EVENING. TYPICALLY IT IS TOUGH FOR
MOMENTUM TO MIX DOWN IN THE SOUTHERLY FLOW (AS THE DEPTH OF THE
MARINE MIXED LAYER IS USUALLY LOW)...AND THIS WAS NO EXCEPTION.
THE SOUTHEAST SOUTHEAST FLOW PROBABLY DOES NOT INCREASE THAT MUCH
TODAY...AND WIND SPEEDS ARE EXPECTED TO REMAIN BELOW SMALL CRAFT
LEVELS. THE QUESTION BECOMES WHETHER SEAS ACTUALLY GET TO 5 FEET ON
THE OCEAN. WNAWAVE GUIDANCE SUGGESTS THIS WILL INDEED HAPPEN LATER
THIS MORNING OR EARLY THIS AFTERNOON. WITH SOME SKEPTICISM...THE
SMALL CRAFT ADVISORY WILL REMAIN IN PLACE FOR NOW. IT IS POSSIBLE...
HOWEVER...IT IS POSSIBLE SEAS MAY NOT QUITE MAKE IT...AND LATER
SHIFTS MAY BE ABLE TO TAKE THIS DOWN.
WINDS MAY TEND TO DROP OFF LATER TONIGHT AS THE SURFACE GRADIENT
BACKS OFF AHEAD OF A WEAK COLD FRONT TO THE WEST. AGAIN THE
FORECAST QUESTION FOR TONIGHT IS WHETHER SEAS GET TO/MAINTAIN SMALL
CRAFT CRITERION. FOR NOW...WILL CONTINUE WITH THE SAME FORECAST
RATIONALE FOR TONIGHT.
OUTLOOK...
THE SOUTHERLY FLOW PRIOR TO A COLD FRONTAL PASSAGE LATER WEDNESDAY
MAY RESULT IN SEAS ON THE OCEAN AROUND 5 FEET. THE SEAS HAVE BEEN
SLOW TO RESPONSE SO FAR IN THE SOUTHERLY FLOW IN THE NEAR TERM,
THEREFORE WE DECIDED NOT TO EXTEND THE SMALL CRAFT ADVISORY INTO
WEDNESDAY AT THIS POINT. THE COLD FRONT SWEEPS EAST OF THE REGION
WEDNESDAY EVENING WITH A NORTHERLY FLOW OCCURRING. THIS DOES NOT
APPEAR STRONG ENOUGH TO GENERATE SMALL CRAFT CONDITIONS CAUSED BY
EITHER SEAS OR WINDS. HIGH PRESSURE THEN SETTLES IN THURSDAY AND
FRIDAY, ALTHOUGH THE NORTHERLY WINDS MAY TEND TO TURN ONSHORE AS THE
FLOW WEAKENS AND POSSIBLE SEA BREEZE CIRCULATIONS DEVELOP. THE
SURFACE HIGH BUILDS EASTWARD FRIDAY AND SATURDAY, ALLOWING FOR MORE
OF A SOUTHEAST FLOW TO OCCUR. A PIECE OF ENERGY POSSIBLY
UNDERCUTTING THE BUILDING RIDGE MAY RESULT IN A SURFACE LOW
DEVELOPING OFF THE SOUTHEASTERN U.S. COAST OVER THE WEEKEND. IT
APPEARS THOUGH THE SURFACE HIGH REMAINS CLOSE ENOUGH TO OUR REGION,
WHICH WOULD NOT GENERATE MUCH OF A LONG ONSHORE FETCH FOR OUR AREA.
&&
.HYDROLOGY...
THE FIRST BATCH OF RAIN HAS MOVED TO THE NORTHEAST OF THE AREA.
THROUGH 0500 UTC...ONE-HALF TO ONE INCH OF RAIN HAD FALLEN ACROSS
THE SOUTHERN POCONOS AND NORTHWEST NEW JERSEY...WITH LESSER AMOUNTS
TO THE SOUTHEAST.
THE NEXT BATCH OF RAIN...TIED TO A SHORT WAVE IN THE MID LEVELS OVER
CENTRAL NORTH CAROLINA EARLY THIS MORNING...SHOULD ARRIVE ACROSS
SOUTHWEST AREAS AFTER 1000 UTC. THIS BATCH HAS SOME ELEVATED
INSTABILITY ASSOCIATED WITH IT...AND PRECIPITABLE WATER VALUES
INCREASE TO NEAR 1.50 INCHES. THE SPECTER OF HEAVY RAIN IS STILL IN
PLACE FOR THIS BATCH...WHICH SHOULD CLEAR NORTHERN ZONES BY LATE
MORNING OR EARLY AFTERNOON.
WE WOULD PROBABLY NEED ANOTHER 1.50 TO 2.00 INCHES OF BASIN AVERAGE
RAINFALL ACROSS THE SOUTHERN POCONOS AND NORTHWEST NEW JERSEY BEFORE
PROBLEMS START (BASED ON THE LATEST HEADWATER GUIDANCE). WHILE NOT
OUT OF THE QUESTION DUE TO THE MOISTURE BLOB TO THE SOUTHWEST...IT
IS LOOKING LESS LIKELY THAN 24 HOURS AGO.
ONCE THAT SHOWER BATCH EXITS...CONVECTIVE ELEMENTS ARE POSSIBLE
LATER THIS AFTERNOON AND THIS EVENING. HOWEVER...IT DOES NOT APPEAR
AS THROUGH THE CONVECTION WILL BE WIDESPREAD ENOUGH TO POSE A
THREAT. THAT HAVING BEEN STATED...THERE ARE NO PLANS FOR HYDROLOGY
HEADLINES TODAY WITH RESPECT TO THE NEXT BATCH OF RAIN.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT WEDNESDAY FOR ANZ450>455.
&&
$$
SYNOPSIS...GORSE
NEAR TERM...HAYES
SHORT TERM...HAYES
LONG TERM...GORSE
AVIATION...GORSE/HAYES
MARINE...GORSE/HAYES
HYDROLOGY...HAYES
000
FXUS61 KPHI 150519
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
119 AM EDT TUE MAY 15 2012
.SYNOPSIS...
A FRONTAL BOUNDARY WILL STALL OVER THE FORECAST AREA THROUGH TUESDAY
AS A WEAK AREA OF LOW PRESSURE TRACKS ALONG IT. THE FRONT AND LOW
WILL THEN MOVE AWAY FROM THE MID ATLANTIC TUESDAY NIGHT, AND A SECONDARY
COLD FRONT WILL MOVE THROUGH LATER ON WEDNESDAY. HIGH PRESSURE IS
FORECAST TO BUILD INTO THE REGION THURSDAY AND FRIDAY, THEN SHIFT
INTO NEW ENGLAND AND THE CANADIAN MARITIMES ON SUNDAY AND MONDAY.
A LOW PRESSURE SYSTEM IS FORECAST TO DEVELOP OFF THE SOUTHEASTERN
UNITED STATES COAST DURING THE WEEKEND AND THEN DRIFT SLOWLY
OFFSHORE THROUGH MONDAY.
&&
.NEAR TERM /UNTIL 6 AM THIS MORNING/...
THE FIRST SHOT OF RAIN IS MOVING INTO SOUTHEAST NEW YORK...MORE OR
LESS ON SCHEDULE. WHILE THERE ARE SCATTERED SHOWERS ACROSS THE
AREA NOW...A MORE CONCENTRATED AREA OF SHOWERS AND EMBEDDED
THUNDERSTORMS ASSOCIATED WITH A SHORT WAVE WILL AFFECT THE AREA
DURING THE EARLY MORNING. FOR NOW...THE MENTION OF THUNDER WAS
LEFT OUT OF THE FORECAST...AS THE BEST RESIDUAL INSTABILITY
REMAINS WELL TO THE SOUTHWEST OF THE AREA.
FOR QPF AMOUNTS AND HYDROLOGICAL INFORMATION, PLEASE REFER TO THE
HYDROLOGY SECTION.
LOW TEMPERATURES WERE NUDGED DOWN A TAD TO ACCOUNT FOR CURRENT
TEMPERATURES AND TRENDS.
&&
.SHORT TERM /6 AM THIS MORNING THROUGH 6 AM WEDNESDAY/...
WE EXPECT RAIN TO BE ONGOING ACROSS MUCH OF THE AREA AT DAYBREAK
TUESDAY. THE AFOREMENTIONED SHORT WAVE WILL MAKE ITS WAY THROUGH THE
AREA EARLY IN THE DAY, BUT THE STALLED OUT BOUNDARY WILL REMAIN
ALONG THE WESTERN AREA OF THE FORECAST AREA. ANOTHER WEAK SHORT WAVE
MAY MOVE THROUGH DURING THE DAY, AND WITH THE PWATS REMAINING
RELATIVELY HIGH, WE SHOULD CONTINUE TO GET SHOWERS THROUGH MUCH OF
THE DAY. HOWEVER, AS MENTIONED BEFORE, THE HIGHEST PWATS ARE
EXPECTED TO BE THROUGH THE MORNING, SO THIS MAY BE THE TIME OF
HEAVIEST RAIN.
THERE IS SOME INSTABILITY FORECAST FOR THE AFTERNOON, SO WE WILL
INCLUDED A CHANCE OF THUNDERSTORMS ACROSS THE ENTIRE FORECAST AREA.
THE SPC HAS OUR OUR AREA UNDER MOSTLY GENERAL THUNDERSTORM, WITH
/SEE TEXT/ EXTENDING ACROSS OUR SOUTHERN HALF/TWO-THIRDS. IF ANY
THUNDERSTORMS DO DEVELOP, THEY COULD CONTAIN HEAVY RAIN, GUSTY
WINDS, IN ADDITION TO THE FREQUENT LIGHTNING. MID-LEVEL LAPSE RATES
LOOK LIKE THEY MAY STEEPEN SLIGHTLY DURING THE AFTERNOON, SO SOME
SMALL HAIL IS NOT OUT OF THE QUESTION.
FOR TEMPERATURES, WE BLENDED THE STAT GUIDANCE, WITH A BIT OF THE
COOLER ECMWF, BUT KEPT CLOSER `WARMER` GFS.
&&
.LONG TERM /WEDNESDAY THROUGH TUESDAY/...
ALL OF THE ACTIVE WEATHER IN THE LONG TERM REMAINS AT THE START. THE
WRF-NMMB 500MB INITIALIZATION LOOKS SLIGHTLY BETTER THAN THE GFS.
THE GFS QPF VERIFICATION THOUGH IS OFF TO A BETTER START THAN THE
WRF-NMMB. DP/DTING THE EVOLUTION OF THE CENTRAL CONUS TROF IS
FINDING IT NOT AS SHARP WITH VERIFYING TIME. CONVERSELY THE
TRAILING FRONT AND TROF IS DEEPENING. SUFFICE WITHOUT A CLEAR
WINNER, WE ARE GOING TO GO WITH A MODELING CONSENSUS IN THIS PART
OF THE FORECAST.
THE DOMESTIC MODELS ARE SLOWER THAN OTHER MODELS IN ENDING THE PCPN
ON TUESDAY NIGHT. WHILE THE STRONGER SYNOPTIC SCALE FORCING APPEARS
TO BE DONE BY THEN, DO NOT BELIEVE IT WILL ALL SHUT DOWN THAT
QUICKLY, SO WE WILL COMPROMISE BETWEEN CONTINUITY AND LATEST
GUIDANCE AND TRAIL OFF CHANCES AS THE NIGHT CONTINUES. FCST
INSTABILITY ALOFT WOULD SUPPORT THUNDER THROUGH THE NIGHT, BUT
WITHOUT ANY FCST WAA, WE TRANSITIONED TO JUST SHOWERS AFTER
MIDNIGHT. NO AIR MASS CHANGE, SO WE BELIEVE THE HIGHER STAT GUIDANCE
STANDS A BETTER CHANCE OF OCCURRING.
THE 12Z RUNS ARE MAKING WEDNESDAY A SLIGHTLY MORE INTERESTING
CONVECTIVE DAY PENDING WE REACH FORECAST MAX TEMPS. ON THE PLUS SIDE
OUR CWA IS FORECAST TO BE IN THE ENTRANCE REGION OF THE H2.5 JET,
HAVE DECENT FORECAST MID LEVEL DRY AIR AND A LINGERING THETA E AXIS
OVER NJ AND DE. ON THE MINUS SIDE FORECAST 850MB WINDS ARE FORECAST
TO BE WEST AND WE HAVE ALREADY SEEN INSTANCES WHERE THIS HAS MUTED
CONVECTIVE STRENGTH AND EVEN OCCURRENCE SO FAR THIS YEAR. MAY BE WHY
WHILE 12HR STAT POPS ARE LIKELY, THE SIX HOUR FORMULAS REMAIN CLOSER
TO LOW CHANCE. ITS SOMETHING TO FOLLOW IN THE DAYS AHEAD. WHILE THE
GFS FCST SFC DEW POINTS ARE TOO HIGH, THE WRF-NMMB SEEM MORE LOGICAL
AND WITH THEIR STRONGER WIND FIELD SOME PULSE TYPE STRONG MAYBE SEVERE
TSTMS COULD HAPPEN. AGAIN PERFECT PROGGING CAPS OR THE LACK
THEREOF AT 54-60HRS IS FRAUGHT WITH DANGER, RIGHT NOW IT DOES NOT
DEVELOP IN TIME. FCST 925MB TEMPS AND A WARM START SUPPORT STAT
GUIDANCE MAX TEMPS.
WE WILL MAINTAIN LOW CHANCES EARLY WEDNESDAY NIGHT AND THEN CLEAR
OUR CWA LATE. GETTING CLOSER TO THOSE SUMMER TIME SCENARIOS WHERE
THE DRY(ER) AIR IS NOT REALIZED UNTIL MIXING THE NEXT DAY. WITH THAT
SAID BELIEVE BECAUSE OF HIER DEWPOINTS GFS MOS LOOKS TOO LOW WITH
MINS.
AFTER THAT THE MODELS HAVE BEEN PRETTY CONSISTENT WITH GIVING OUR
CWA TWO SEASONABLY PLEASANT DAYS ON THURSDAY AND FRIDAY WITH GREATER
UNCERTAINTY AS TO THE SOUTHEAST ATLANTIC SYSTEM AS WE MOVE THROUGH
THE WEEKEND AND EARLY NEXT WEEK. THE HIGH PRESSURE SYSTEM IS NOW
FORECAST TO BUILD MORE OVER THE FORECAST AREA ON SATURDAY SO THE
ONSHORE FLOW DOES NOT LOOK AS IMPRESSIVE. THEN THE QUESTION COMES
TO THE EVOLUTION OF THE SYSTEM BEYOND THAT. THE 00Z MODEL RUNS
WERE IN BETTER AGREEMENT ABOUT THE SYSTEM GOING TOO FAR OFFSHORE
TO AFFECT US. THE 12Z RUN IS BACK TO A MORE OF A DIVERGENT LOOK
WITH THE GFS AND CAN GGEM REMAINING MORE PROGRESSIVE, THE UKMET
CAPTURING THE LOW CLOSER TO THE COAST WITH THE ECMWF COMING CLOSE
TO THE LEGAL LIMITS FOR RETROGRADING A LOW WESTWARD. THIS IS
OBVIOUSLY TOWARD THE END OF THE DETERMINISTIC FORECASTS AND UNCERTAINTY
DOES EXIST. THE UKMET SOLUTION WOULD BE A MORE METEOROLOGICALLY
CONSISTENT SOLUTION IF THE LOW WAS TO AFFECT US. GIVEN THAT THE
ENSEMBLE MEANS, EVEN THE ECMWF`S ARE MORE PROGRESSIVE AND OR SHOW A
REX BLOCK PROTECTING US, WE WILL KEEP THE FORECAST DRY FOR NOW.
&&
.AVIATION /05Z TUESDAY THROUGH SATURDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.
CONDITIONS ARE VARIABLE ACROSS THE AREA EARLY THIS MORNING...BUT FOR
THE MOST PART VFR CONDITIONS CONTINUE AT MOST LOCATIONS. LOCAL
SOUNDINGS SUGGEST THAT THE LOWER LEVELS HAVE NOT YET SUFFICIENTLY
SATURATED FOR MORE WIDESPREAD MVFR/IFR CONDITIONS.
THE FORECAST REMAINS TRICKY...AS STATISTICAL GUIDANCE SUGGESTS A LOW
DESCENT INTO MVFR AND LOCAL IFR CONDITIONS. FOR NOW...THIS TREND WAS
SLOWED...AS OBSERVATIONS DO NOT SUPPORT DROPPING AS QUICKLY AS
GUIDANCE. MOST LOCATIONS WERE DROPPED TO MVFR BEFORE 1100 UTC...AND
SHOULD REMAIN THERE UNTIL ABOUT 1600 OR 1700 UTC.
AFTER THIS...CONDITIONS MAY TRY TO IMPROVE TO NEAR VFR...ESPECIALLY
SOUTH AND EAST OF KPHL. CONSIDERING HOW SLOWLY CONDITIONS HAVE BEEN
TO DROP...THIS DOES NOT SEEM IMPLAUSIBLE...BUT CONFIDENCE IN VFR
CONDITIONS THIS AFTERNOON IS STILL LOW. SCATTERED THUNDERSTORMS MAY
TRY TO FROM WEST OF THE AREA THIS AFTERNOON...AND COULD IMPACT KPHL
METRO TERMINALS AFTER 0000 UTC. HOWEVER...CONFIDENCE WAS NOT HIGH
ENOUGH FOR INCLUSION IN THE 0600 UTC TERMINAL FORECASTS.
AFTER THE POTENTIAL FOR CONVECTION EXITS...CONDITIONS SHOULD SETTLE
BACK TO MVFR AFTER 0300 UTC WEDNESDAY. STATISTICAL GUIDANCE SUGGEST
CONDITIONS COULD LOWER TO IFR...BUT FOR NOW THIS WAS NOT INCLUDED IN
THE FORECAST.
OUTLOOK...
WEDNESDAY...MVFR TO LOCALLY IFR IN POSSIBLE MORNING LOW CLOUDS
OR FOG, THEN IMPROVING TO VFR. A FEW SHOWERS OR THUNDERSTORMS ARE
POSSIBLE WITH MVFR CONDITIONS LATER IN THE DAY INTO THE EARLY
EVENING. AVERAGE CONFIDENCE.
WEDNESDAY NIGHT...VFR WITH MVFR POSSIBLE AT MORE RURAL AIRPORTS.
AVERAGE CONFIDENCE.
THURSDAY THROUGH SATURDAY...VFR. HIGH CONFIDENCE FOR THURSDAY AND
FRIDAY. AVERAGE CONFIDENCE SATURDAY.
&&
.MARINE...
A SMALL CRAFT ADVISORY WILL REMAIN IN EFFECT FOR THE OCEAN THROUGH
TUESDAY NIGHT FOR SEAS. SEAS WERE SLOW TO BUILD AND REMAINED AT
2 TO 3 FEET OVER THE ATLANTIC WATERS THIS EVENING. NATIONAL
GUIDANCE TAKES THEM TO 5 FEET OVERNIGHT AND KEEPS THEM THERE FOR
THE NEXT COUPLE OF DAYS.
WINDS ARE EXPECTED TO INCREASE AND MAY GET CLOSE TO 25 KNOTS LATE
TONIGHT INTO TUESDAY.
OUTLOOK...
SMALL CRAFT ADVISORY CONDITIONS PARTICULARLY FOR THE SOUTHERLY SWELL
SEAS ON OUR OCEAN WATERS SHOULD CONTINUE INTO TUESDAY NIGHT INTO
WEDNESDAY AND MAY VERY WELL LINGER INTO MOST OF WEDNESDAY NIGHT.
AFTER THE SECONDARY FRONT CLEARS THE REGION, THE NORTHERLY FLOW DOES
NOT APPEAR STRONG ENOUGH TO GENERATE SMALL CRAFT CONDITIONS
CAUSED BY EITHER SEAS OR WINDS. WHILE UNCERTAINTY EXISTS ABOUT THE
SOUTHEAST COAST SYSTEM FOR SUNDAY AND MONDAY, THROUGH SATURDAY IT
LOOKS AS THOUGH THE HIGH PRESSURE SYSTEM WILL SETTLE CLOSE ENOUGH
TO THE AREA TO NOT BE ABLE TO GENERATE MUCH OF A LONG ONSHORE
FETCH FOR OUR MARINE AREA INTO SATURDAY.
&&
.HYDROLOGY...
THE SURFACE FRONT THAT HAS STALLED ACROSS THE SOUTHERN POCONOS AND
LEHIGH VALLEY WILL ACT AS A CONDUIT FOR THE POTENTIAL FOR HEAVY
RAIN TONIGHT INTO TUESDAY. AT THIS TIME...MODEL OVERALL QPF HAS
EITHER LOWERED OR HAS THE AXIS OF HEAVIEST RAIN POSITIONED
NORTHWEST OF THE AREA.
THE SURFACE FRONT IS EXPECTED TO STALL OVER EVEN BE NUDGED BACK WEST
BY THE SURFACE HIGH OFF THE MID ATLANTIC COAST. THE POSITIONING OF
THE FRONT WILL BE ONE OF THE KEYS TO THE HEAVY RAIN FORECAST...AS IT
ACTS AS THE FOCUSING MECHANISM FOR THE MOIST THETA E LADEN AIR. A
WEAK SHORT WAVE RIDING OUT AHEAD OF THE THE LONG WAVE TROUGH CARVED
OUT OVER THE MISSISSIPPI VALLEY WILL FOCUS THE HEAVY RAIN LATE
THIS EVENING...JUST TO THE SOUTHWEST OF THE AREA.
AT ABOUT THE SAME TIME...A LOW LEVEL JET WILL STREAK NORTHEAST JUST
TO THE EAST OF THE SURFACE FRONT. WHILE THERE COULD BE SOME ELEVATED
INSTABILITY ASSOCIATED WITH THE LOW LEVEL JET...IT DOES NOT SEEM AS
THOUGH DEEP CONVECTION WILL BE AN IMPORTANT COMPONENT TO THE HEAVY
RAIN THREAT. INSTEAD...WARM PROCESSES SHOULD DOMINATE THE
PRECIPITATION GENERATION...AS PRECIPITABLE WATER VALUES REACH AROUND
1.50 INCHES.
AS THE SHORT WAVE PASSES LATE TONIGHT...THE CORE OF THE HEAVIEST
RAIN SHOULD BE JUST AHEAD OF IT. THE AREAS MOST LIKELY TO BE
IMPACTED BY THE HEAVY RAIN ARE THE LEHIGH VALLEY...SOUTHERN POCONOS
AND POSSIBLY NORTHWEST NEW JERSEY. THIS SLUG OF HEAVY RAIN PROBABLY
EXITS TO THE NORTHEAST TUESDAY MORNING.
AS THIS POINT...IT APPEARS AS THOUGH AS MUCH AS 2 INCHES OF RAIN
COULD FALL OVER PORTIONS OF THE LEHIGH VALLEY AND THE HIGHER TERRAIN
(IN ABOUT 12 HOURS). THIS NUMBER IS CONSIDERABLY BELOW THE FLASH
FLOOD AND HEADWATER GUIDANCE NUMBERS FOR THE 12 HOUR PERIOD ENDING
TUESDAY MORNING. WHILE SOME OF THE MEMBERS OF THE MMEFS GUIDANCE
SUGGEST THAT SOME OF OUR FORECAST POINTS COULD REACH CAUTION STAGE
WITH THE HEAVY RAIN...THE LATEST RIVER FORECASTS DO NOT.
SHOULD THE AXIS OF HEAVIEST RAIN FALL FURTHER TO THE EAST...THE
SMALLER RIVERS AND CREEKS OF NORTHERN DELAWARE AND SOUTHEAST
PENNSYLVANIA COULD BE AFFECTED. RIGHT NOW...APPEARS AS THOUGH WE WOULD
NEED CLOSE TO 2.5 INCHES IN ABOUT 12 HOURS FOR THESE QUICK
RESPONDERS TO BECOME A PROBLEM. AS OF THIS AFTERNOON...WE DO NOT
EXPECT THAT TO HAPPEN. FOR TUESDAY, PERIODS OF RAIN SOME OF WHICH
COULD BE HEAVY WILL BE SLIDING EASTWARD ACROSS THE REGION ALONG
WITH THE LOW-LEVEL JET. IT APPEARS THAT THE HEAVIER RAIN MAY BE
SPREAD OUT ENOUGH DESPITE PERHAPS SOME EMBEDDED CONVECTIVE
ELEMENTS. THEREFORE BASED ON ALL OF THE ABOVE, WE WILL HOLD OFF ON
THE FLOOD WATCH AND CONTINUE A MENTION IN THE HAZARDOUS WEATHER
OUTLOOK.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT WEDNESDAY FOR ANZ450>455.
&&
$$
SYNOPSIS...GIGI/GORSE
NEAR TERM...ROBERTSON
SHORT TERM...ROBERTSON
LONG TERM...GIGI
AVIATION...GIGI/HAYES
MARINE...GIGI/ROBERTSON
HYDROLOGY...GIGI/GORSE
000
FXUS61 KPHI 150037
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
837 PM EDT MON MAY 14 2012
.SYNOPSIS...
A FRONTAL BOUNDARY WILL STALL OVER THE FORECAST AREA THROUGH TUESDAY
AS A WEAK AREA OF LOW PRESSURE TRACKS ALONG IT. THE FRONT AND LOW
WILL THEN MOVE AWAY FROM THE MID ATLANTIC TUESDAY NIGHT, AND A SECONDARY
COLD FRONT WILL MOVE THROUGH LATER ON WEDNESDAY. HIGH PRESSURE IS
FORECAST TO BUILD INTO THE REGION THURSDAY AND FRIDAY, THEN SHIFT
INTO NEW ENGLAND AND THE CANADIAN MARITIMES ON SUNDAY AND MONDAY.
A LOW PRESSURE SYSTEM IS FORECAST TO DEVELOP OFF THE SOUTHEASTERN
UNITED STATES COAST DURING THE WEEKEND AND THEN DRIFT SLOWLY
OFFSHORE THROUGH MONDAY.
&&
.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
QUITE AN UNSETTLED PERIOD EXPECTED TONIGHT THROUGH TUESDAY.
SYNOPTICALLY WE HAVE A WEAK STATIONARY BOUNDARY THAT IS BEGINNING TO
WASH OUT ON OUR WESTERN BORDERS, WITH A BROAD MID/UPPER TROUGH
EXTENDING FORM THE OHIO RIVER VALLEY SOUTHWESTWARD THROUGH THE
SOUTHERN PLAINS. SEVERAL SHORT WAVES ARE EXPECTED TO CROSS OUR AREA
IN THE FLOW ALOFT, WHICH WILL GIVE US A FEW PERIODS OF PRECIPITATION.
THE FIRST WAVE OF PRECIPITATION CONTINUED TO AFFECT AREAS MAINLY
NEAR AND NORTHWEST OF THE I-95 CORRIDOR THIS EVENING. A SECOND ONE
WAS MOVING NORTHEAST UP THE WESTERN SPINE OF VIRGINIA. THE SECOND
ONE IS MORE CLOSELY TIED TO A STRONGER SHORT WAVE ALOFT AND
ASSOCIATED SURFACE WAVE. WE EXPECT THIS ONE TO BRING HEAVIER RAIN
TO MORE OF THE AREA OVERNIGHT. THE NAM WOULD HAVE SOME OVERNIGHT
THUNDER WITH THIS, BUT WE HAVEN`T ADDED THAT TO THE FORECAST YET.
FOR QPF AMOUNTS AND HYDROLOGICAL INFORMATION, PLEASE REFER TO THE
HYDROLOGY SECTION.
WE NUDGED TEMPERATURES UP JUST A LITTLE FROM CONTINUITY ESPECIALLY
NORTHWEST WHERE THE TEMPERATURE/DEW POINT SPREAD HAD APPROACHED
NIL.
&&
.SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/...
WE EXPECT RAIN TO BE ONGOING ACROSS MUCH OF THE AREA AT DAYBREAK
TUESDAY. THE AFOREMENTIONED SHORT WAVE WILL MAKE ITS WAY THROUGH THE
AREA EARLY IN THE DAY, BUT THE STALLED OUT BOUNDARY WILL REMAIN
ALONG THE WESTERN AREA OF THE FORECAST AREA. ANOTHER WEAK SHORT WAVE
MAY MOVE THROUGH DURING THE DAY, AND WITH THE PWATS REMAINING
RELATIVELY HIGH, WE SHOULD CONTINUE TO GET SHOWERS THROUGH MUCH OF
THE DAY. HOWEVER, AS MENTIONED BEFORE, THE HIGHEST PWATS ARE
EXPECTED TO BE THROUGH THE MORNING, SO THIS MAY BE THE TIME OF
HEAVIEST RAIN.
THERE IS SOME INSTABILITY FORECAST FOR THE AFTERNOON, SO WE WILL
INCLUDED A CHANCE OF THUNDERSTORMS ACROSS THE ENTIRE FORECAST AREA.
THE SPC HAS OUR OUR AREA UNDER MOSTLY GENERAL THUNDERSTORM, WITH
/SEE TEXT/ EXTENDING ACROSS OUR SOUTHERN HALF/TWO-THIRDS. IF ANY
THUNDERSTORMS DO DEVELOP, THEY COULD CONTAIN HEAVY RAIN, GUSTY
WINDS, IN ADDITION TO THE FREQUENT LIGHTNING. MID-LEVEL LAPSE RATES
LOOK LIKE THEY MAY STEEPEN SLIGHTLY DURING THE AFTERNOON, SO SOME
SMALL HAIL IS NOT OUT OF THE QUESTION.
FOR TEMPERATURES, WE BLENDED THE STAT GUIDANCE, WITH A BIT OF THE
COOLER ECMWF, BUT KEPT CLOSER `WARMER` GFS.
&&
.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
ALL OF THE ACTIVE WEATHER IN THE LONG TERM REMAINS AT THE START. THE
WRF-NMMB 500MB INITIALIZATION LOOKS SLIGHTLY BETTER THAN THE GFS.
THE GFS QPF VERIFICATION THOUGH IS OFF TO A BETTER START THAN THE
WRF-NMMB. DP/DTING THE EVOLUTION OF THE CENTRAL CONUS TROF IS
FINDING IT NOT AS SHARP WITH VERIFYING TIME. CONVERSELY THE
TRAILING FRONT AND TROF IS DEEPENING. SUFFICE WITHOUT A CLEAR
WINNER, WE ARE GOING TO GO WITH A MODELING CONSENSUS IN THIS PART
OF THE FORECAST.
THE DOMESTIC MODELS ARE SLOWER THAN OTHER MODELS IN ENDING THE PCPN
ON TUESDAY NIGHT. WHILE THE STRONGER SYNOPTIC SCALE FORCING APPEARS
TO BE DONE BY THEN, DO NOT BELIEVE IT WILL ALL SHUT DOWN THAT
QUICKLY, SO WE WILL COMPROMISE BETWEEN CONTINUITY AND LATEST
GUIDANCE AND TRAIL OFF CHANCES AS THE NIGHT CONTINUES. FCST
INSTABILITY ALOFT WOULD SUPPORT THUNDER THROUGH THE NIGHT, BUT
WITHOUT ANY FCST WAA, WE TRANSITIONED TO JUST SHOWERS AFTER
MIDNIGHT. NO AIR MASS CHANGE, SO WE BELIEVE THE HIGHER STAT GUIDANCE
STANDS A BETTER CHANCE OF OCCURRING.
THE 12Z RUNS ARE MAKING WEDNESDAY A SLIGHTLY MORE INTERESTING
CONVECTIVE DAY PENDING WE REACH FORECAST MAX TEMPS. ON THE PLUS SIDE
OUR CWA IS FORECAST TO BE IN THE ENTRANCE REGION OF THE H2.5 JET,
HAVE DECENT FORECAST MID LEVEL DRY AIR AND A LINGERING THETA E AXIS
OVER NJ AND DE. ON THE MINUS SIDE FORECAST 850MB WINDS ARE FORECAST
TO BE WEST AND WE HAVE ALREADY SEEN INSTANCES WHERE THIS HAS MUTED
CONVECTIVE STRENGTH AND EVEN OCCURRENCE SO FAR THIS YEAR. MAY BE WHY
WHILE 12HR STAT POPS ARE LIKELY, THE SIX HOUR FORMULAS REMAIN CLOSER
TO LOW CHANCE. ITS SOMETHING TO FOLLOW IN THE DAYS AHEAD. WHILE THE
GFS FCST SFC DEW POINTS ARE TOO HIGH, THE WRF-NMMB SEEM MORE LOGICAL
AND WITH THEIR STRONGER WIND FIELD SOME PULSE TYPE STRONG MAYBE SEVERE
TSTMS COULD HAPPEN. AGAIN PERFECT PROGGING CAPS OR THE LACK
THEREOF AT 54-60HRS IS FRAUGHT WITH DANGER, RIGHT NOW IT DOES NOT
DEVELOP IN TIME. FCST 925MB TEMPS AND A WARM START SUPPORT STAT
GUIDANCE MAX TEMPS.
WE WILL MAINTAIN LOW CHANCES EARLY WEDNESDAY NIGHT AND THEN CLEAR
OUR CWA LATE. GETTING CLOSER TO THOSE SUMMER TIME SCENARIOS WHERE
THE DRY(ER) AIR IS NOT REALIZED UNTIL MIXING THE NEXT DAY. WITH THAT
SAID BELIEVE BECAUSE OF HIER DEWPOINTS GFS MOS LOOKS TOO LOW WITH
MINS.
AFTER THAT THE MODELS HAVE BEEN PRETTY CONSISTENT WITH GIVING OUR
CWA TWO SEASONABLY PLEASANT DAYS ON THURSDAY AND FRIDAY WITH GREATER
UNCERTAINTY AS TO THE SOUTHEAST ATLANTIC SYSTEM AS WE MOVE THROUGH
THE WEEKEND AND EARLY NEXT WEEK. THE HIGH PRESSURE SYSTEM IS NOW
FORECAST TO BUILD MORE OVER THE FORECAST AREA ON SATURDAY SO THE
ONSHORE FLOW DOES NOT LOOK AS IMPRESSIVE. THEN THE QUESTION COMES
TO THE EVOLUTION OF THE SYSTEM BEYOND THAT. THE 00Z MODEL RUNS
WERE IN BETTER AGREEMENT ABOUT THE SYSTEM GOING TOO FAR OFFSHORE
TO AFFECT US. THE 12Z RUN IS BACK TO A MORE OF A DIVERGENT LOOK
WITH THE GFS AND CAN GGEM REMAINING MORE PROGRESSIVE, THE UKMET
CAPTURING THE LOW CLOSER TO THE COAST WITH THE ECMWF COMING CLOSE
TO THE LEGAL LIMITS FOR RETROGRADING A LOW WESTWARD. THIS IS
OBVIOUSLY TOWARD THE END OF THE DETERMINISTIC FORECASTS AND UNCERTAINTY
DOES EXIST. THE UKMET SOLUTION WOULD BE A MORE METEOROLOGICALLY
CONSISTENT SOLUTION IF THE LOW WAS TO AFFECT US. GIVEN THAT THE
ENSEMBLE MEANS, EVEN THE ECMWF`S ARE MORE PROGRESSIVE AND OR SHOW A
REX BLOCK PROTECTING US, WE WILL KEEP THE FORECAST DRY FOR NOW.
&&
.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.
MOSTLY VFR CONDITIONS ARE STARTING OFF THE FORECAST, WITH SOME
SCATTERED MVFR AND/OR IFR NORTHWEST. WE HAVE SLOWED THE
DETERIORATION IN CONDITIONS FROM NORTHWEST TO SOUTHEAST, BUT WE
DO EVENTUALLY BRING ALL SITES DOWN TO IFR AFTER MIDNIGHT. ANOTHER
BATCH OF RAIN THAT IS MOVING NORTHEAST FROM WESTERN VIRGINIA IS
EXPECTED TO BE HEAVIER IN NATURE. IT IS FORECAST INTO OUR AREA
AFTER MIDNIGHT TONIGHT, AND SHOULD CONTINUE THROUGH THE MORNING
HOURS TUESDAY.
ONCE CONDITIONS DROP TO IFR TONIGHT, THEY SHOULD CONTINUE INTO THE
MORNING TUESDAY, THEN EVENTUALLY LIFT TO MVFR BY MID-DAY. ACTUALLY
BY THE AFTERNOON, WE MAY BECOME VFR AT MANY PLACES. THERE IS THE
POSSIBILITY OF THUNDERSTORMS ON TUESDAY.
OUTLOOK...
TUESDAY (REST OF) AFTERNOON AND NIGHT...MVFR WITH IFR AT TIMES
FIRST WITH PERIODS OF RAIN AND PERHAPS A THUNDERSTORM, THEN MAINLY
DUE TO LOW CLOUDS AT NIGHT. THE RAIN IS EXPECTED TO TAPER OFF BY
TUESDAY NIGHT. HIGH CONFIDENCE.
WEDNESDAY...MVFR TO LOCALLY IFR IN POSSIBLE MORNING LOW CLOUDS OR
FOG, THEN IMPROVING TO VFR. A FEW SHOWERS OR THUNDERSTORMS ARE
POSSIBLE WITH MVFR CONDITIONS LATER IN THE DAY INTO THE EARLY EVENING.
AVERAGE CONFIDENCE.
WEDNESDAY NIGHT...VFR WITH MVFR POSSIBLE AT MORE RURAL AIRPORTS.
AVERAGE CONFIDENCE.
THURSDAY THROUGH SATURDAY...VFR. HIGH CONFIDENCE FOR THURSDAY AND
FRIDAY. AVERAGE CONFIDENCE SATURDAY.
&&
.MARINE...
A SMALL CRAFT ADVISORY WILL REMAIN IN EFFECT FOR THE OCEAN THROUGH
TUESDAY NIGHT FOR SEAS. SEAS WERE SLOW TO BUILD AND REMAINED AT
2 TO 3 FEET OVER THE ATLANTIC WATERS THIS EVENING. NATIONAL
GUIDANCE TAKES THEM TO 5 FEET OVERNIGHT AND KEEPS THEM THERE FOR
THE NEXT COUPLE OF DAYS.
WINDS ARE EXPECTED TO INCREASE AND MAY GET CLOSE TO 25 KNOTS LATE
TONIGHT INTO TUESDAY.
OUTLOOK...
SMALL CRAFT ADVISORY CONDITIONS PARTICULARLY FOR THE SOUTHERLY SWELL
SEAS ON OUR OCEAN WATERS SHOULD CONTINUE INTO TUESDAY NIGHT INTO
WEDNESDAY AND MAY VERY WELL LINGER INTO MOST OF WEDNESDAY NIGHT.
AFTER THE SECONDARY FRONT CLEARS THE REGION, THE NORTHERLY FLOW DOES
NOT APPEAR STRONG ENOUGH TO GENERATE SMALL CRAFT CONDITIONS
CAUSED BY EITHER SEAS OR WINDS. WHILE UNCERTAINTY EXISTS ABOUT THE
SOUTHEAST COAST SYSTEM FOR SUNDAY AND MONDAY, THROUGH SATURDAY IT
LOOKS AS THOUGH THE HIGH PRESSURE SYSTEM WILL SETTLE CLOSE ENOUGH
TO THE AREA TO NOT BE ABLE TO GENERATE MUCH OF A LONG ONSHORE
FETCH FOR OUR MARINE AREA INTO SATURDAY.
&&
.HYDROLOGY...
THE SURFACE FRONT THAT HAS STALLED ACROSS THE SOUTHERN POCONOS AND
LEHIGH VALLEY WILL ACT AS A CONDUIT FOR THE POTENTIAL FOR HEAVY
RAIN TONIGHT INTO TUESDAY. AT THIS TIME...MODEL OVERALL QPF HAS
EITHER LOWERED OR HAS THE AXIS OF HEAVIEST RAIN POSITIONED
NORTHWEST OF THE AREA.
THE SURFACE FRONT IS EXPECTED TO STALL OVER EVEN BE NUDGED BACK WEST
BY THE SURFACE HIGH OFF THE MID ATLANTIC COAST. THE POSITIONING OF
THE FRONT WILL BE ONE OF THE KEYS TO THE HEAVY RAIN FORECAST...AS IT
ACTS AS THE FOCUSING MECHANISM FOR THE MOIST THETA E LADEN AIR. A
WEAK SHORT WAVE RIDING OUT AHEAD OF THE THE LONG WAVE TROUGH CARVED
OUT OVER THE MISSISSIPPI VALLEY WILL FOCUS THE HEAVY RAIN LATE
THIS EVENING...JUST TO THE SOUTHWEST OF THE AREA.
AT ABOUT THE SAME TIME...A LOW LEVEL JET WILL STREAK NORTHEAST JUST
TO THE EAST OF THE SURFACE FRONT. WHILE THERE COULD BE SOME ELEVATED
INSTABILITY ASSOCIATED WITH THE LOW LEVEL JET...IT DOES NOT SEEM AS
THOUGH DEEP CONVECTION WILL BE AN IMPORTANT COMPONENT TO THE HEAVY
RAIN THREAT. INSTEAD...WARM PROCESSES SHOULD DOMINATE THE
PRECIPITATION GENERATION...AS PRECIPITABLE WATER VALUES REACH AROUND
1.50 INCHES.
AS THE SHORT WAVE PASSES LATE TONIGHT...THE CORE OF THE HEAVIEST
RAIN SHOULD BE JUST AHEAD OF IT. THE AREAS MOST LIKELY TO BE
IMPACTED BY THE HEAVY RAIN ARE THE LEHIGH VALLEY...SOUTHERN POCONOS
AND POSSIBLY NORTHWEST NEW JERSEY. THIS SLUG OF HEAVY RAIN PROBABLY
EXITS TO THE NORTHEAST TUESDAY MORNING.
AS THIS POINT...IT APPEARS AS THOUGH AS MUCH AS 2 INCHES OF RAIN
COULD FALL OVER PORTIONS OF THE LEHIGH VALLEY AND THE HIGHER TERRAIN
(IN ABOUT 12 HOURS). THIS NUMBER IS CONSIDERABLY BELOW THE FLASH
FLOOD AND HEADWATER GUIDANCE NUMBERS FOR THE 12 HOUR PERIOD ENDING
TUESDAY MORNING. WHILE SOME OF THE MEMBERS OF THE MMEFS GUIDANCE
SUGGEST THAT SOME OF OUR FORECAST POINTS COULD REACH CAUTION STAGE
WITH THE HEAVY RAIN...THE LATEST RIVER FORECASTS DO NOT.
SHOULD THE AXIS OF HEAVIEST RAIN FALL FURTHER TO THE EAST...THE
SMALLER RIVERS AND CREEKS OF NORTHERN DELAWARE AND SOUTHEAST
PENNSYLVANIA COULD BE AFFECTED. RIGHT NOW...APPEARS AS THOUGH WE WOULD
NEED CLOSE TO 2.5 INCHES IN ABOUT 12 HOURS FOR THESE QUICK
RESPONDERS TO BECOME A PROBLEM. AS OF THIS AFTERNOON...WE DO NOT
EXPECT THAT TO HAPPEN. FOR TUESDAY, PERIODS OF RAIN SOME OF WHICH
COULD BE HEAVY WILL BE SLIDING EASTWARD ACROSS THE REGION ALONG
WITH THE LOW-LEVEL JET. IT APPEARS THAT THE HEAVIER RAIN MAY BE
SPREAD OUT ENOUGH DESPITE PERHAPS SOME EMBEDDED CONVECTIVE
ELEMENTS. THEREFORE BASED ON ALL OF THE ABOVE, WE WILL HOLD OFF ON
THE FLOOD WATCH AND CONTINUE A MENTION IN THE HAZARDOUS WEATHER
OUTLOOK.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT WEDNESDAY FOR ANZ450>455.
&&
$$
SYNOPSIS...GIGI/GORSE
NEAR TERM...ROBERTSON/DELISI
SHORT TERM...ROBERTSON
LONG TERM...GIGI
AVIATION...GIGI/GORSE/ROBERTSON/DELISI
MARINE...GIGI/ROBERTSON/DELISI
HYDROLOGY...GIGI/GORSE/HAYES
000
FXUS61 KPHI 142045
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
445 PM EDT MON MAY 14 2012
.SYNOPSIS...
A FRONTAL BOUNDARY WILL STALL OVER THE FORECAST AREA THROUGH TUESDAY
AS A WEAK AREA OF LOW PRESSURE TRACKS ALONG IT. THE FRONT AND LOW
WILL THEN MOVE AWAY FROM THE MID ATLANTIC TUESDAY NIGHT AS A
SECONDARY COLD FRONT MOVES THROUGH LATER ON WEDNESDAY. HIGH
PRESSURE IS FORECAST TO BUILD INTO THE REGION THURSDAY AND FRIDAY,
THEN SHIFT INTO NEW ENGLAND AND THE CANADIAN MARITIMES ON SUNDAY AND
MONDAY. A LOW PRESSURE SYSTEM IS FORECAST TO DEVELOP OFF THE
SOUTHEASTERN UNITED STATES COAST DURING THE WEEKEND AND THEN DRIFT
SLOWLY OFFSHORE THROUGH MONDAY.
&&
.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
QUITE AN UNSETTLED PERIOD EXPECTED TONIGHT THROUGH TUESDAY.
SYNOPTICALLY WE HAVE A WEAK STATIONARY BOUNDARY THAT IS BEGINNING TO
WASH OUT ON OUR WESTERN BORDERS, WITH A BROAD MID/UPPER TROUGH
EXTENDING FORM THE OHIO RIVER VALLEY SOUTHWESTWARD THROUGH THE
SOUTHERN PLAINS. SEVERAL SHORT WAVES ARE EXPECTED TO CROSS OUR AREA
IN THE FLOW ALOFT, WHICH WILL GIVE US A FEW PERIODS OF PRECIPITATION.
THE FIRST WAVE OF PRECIPITATION IS MOVING ACROSS OUR WESTERN ZONES
AND JUST TO OUR WEST THIS AFTERNOON AND WILL CONTINUE INTO THE
EVENING AHEAD OF A WEAK VORT MAX/SHORT WAVE. THE HEAVIEST AND MOST
WIDESPREAD RAIN WILL REMAIN MOSTLY TO OUR WEST, BUT THERE STILL
COULD BE SOME SHOWER ACTIVITY ACROSS THE ENTIRE AREA. THEREFORE WE
HAVE THE HIGHEST POPS OUT WEST, WITH LOWEST EAST THIS EVENING.
THE NEXT ROUND IS EXPECTED TO MOVE INTO THE AREA AROUND OR SHORTLY
AFTER MIDNIGHT WITH THE NEXT VORT MAX/SHORT WAVE. ANOTHER WAVE OF
LOW PRESSURE IS EXPECTED TO DEVELOP ALONG THE STALLED OUT BOUNDARY
AND MOVE TOWARD OUR AREA, WHILE THE PWATS INCREASE AHEAD OF THIS
SHORTWAVE. THEREFORE, WE EXPECT THE HEAVIEST RAIN TO BEGIN TO SPREAD
ACROSS THE AREA AROUND MIDNIGHT AND CONTINUE THROUGH DAYBREAK AS
THESE FEATURES SLOWLY MOVE EASTWARD.
FOR QPF AMOUNTS AND HYDROLOGICAL INFORMATION, PLEASE REFER TO THE
HYDROLOGY SECTION.
FOR TEMPERATURES TONIGHT, WE DECIDED TO TAKE A BLEND OF THE STAT
GUIDANCE SINCE THEY WERE RELATIVELY CLOSE, THOUGH WE DID STAY CLOSER
TO THE `SLIGHTLY` COOLER GFS.
&&
.SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/...
WE EXPECT RAIN TO BE ONGOING ACROSS MUCH OF THE AREA AT DAYBREAK
TUESDAY. THE AFOREMENTIONED SHORT WAVE WILL MAKE ITS WAY THROUGH THE
AREA EARLY IN THE DAY, BUT THE STALLED OUT BOUNDARY WILL REMAIN
ALONG THE WESTERN AREA OF THE FORECAST AREA. ANOTHER WEAK SHORT WAVE
MAY MOVE THROUGH DURING THE DAY, AND WITH THE PWATS REMAINING
RELATIVELY HIGH, WE SHOULD CONTINUE TO GET SHOWERS THROUGH MUCH OF
THE DAY. HOWEVER, AS MENTIONED BEFORE, THE HIGHEST PWATS ARE
EXPECTED TO BE THROUGH THE MORNING, SO THIS MAY BE THE TIME OF
HEAVIEST RAIN.
THERE IS SOME INSTABILITY FORECAST FOR THE AFTERNOON, SO WE WILL
INCLUDED A CHANCE OF THUNDERSTORMS ACROSS THE ENTIRE FORECAST AREA.
THE SPC HAS OUR OUR AREA UNDER MOSTLY GENERAL THUNDERSTORM, WITH
/SEE TEXT/ EXTENDING ACROSS OUR SOUTHERN HALF/TWO-THIRDS. IF ANY
THUNDERSTORMS DO DEVELOP, THEY COULD CONTAIN HEAVY RAIN, GUSTY
WINDS, IN ADDITION TO THE FREQUENT LIGHTNING. MID-LEVEL LAPSE RATES
LOOK LIKE THEY MAY STEEPEN SLIGHTLY DURING THE AFTERNOON, SO SOME
SMALL HAIL IS NOT OUT OF THE QUESTION.
FOR TEMPERATURES, WE BLENDED THE STAT GUIDANCE, WITH A BIT OF THE
COOLER ECMWF, BUT KEPT CLOSER `WARMER` GFS.
&&
.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
ALL OF THE ACTIVE WEATHER IN THE LONG TERM REMAINS AT THE START. THE
WRF-NMMB 500MB INITIALIZATION LOOKS SLIGHTLY BETTER THAN THE GFS.
THE GFS QPF VERIFICATION THOUGH IS OFF TO A BETTER START THAN THE
WRF-NMMB. DP/DTING THE EVOLUTION OF THE CENTRAL CONUS TROF IS
FINDING IT NOT AS SHARP WITH VERIFYING TIME. CONVERSELY THE
TRAILING FRONT AND TROF IS DEEPENING. SUFFICE WITHOUT A CLEAR
WINNER, WE ARE GOING TO GO WITH A MODELING CONSENSUS IN THIS PART
OF THE FORECAST.
THE DOMESTIC MODELS ARE SLOWER THAN OTHER MODELS IN ENDING THE PCPN
ON TUESDAY NIGHT. WHILE THE STRONGER SYNOPTIC SCALE FORCING APPEARS
TO BE DONE BY THEN, DO NOT BELIEVE IT WILL ALL SHUT DOWN THAT
QUICKLY, SO WE WILL COMPROMISE BETWEEN CONTINUITY AND LATEST
GUIDANCE AND TRAIL OFF CHANCES AS THE NIGHT CONTINUES. FCST
INSTABILITY ALOFT WOULD SUPPORT THUNDER THROUGH THE NIGHT, BUT
WITHOUT ANY FCST WAA, WE TRANSITIONED TO JUST SHOWERS AFTER
MIDNIGHT. NO AIR MASS CHANGE, SO WE BELIEVE THE HIGHER STAT GUIDANCE
STANDS A BETTER CHANCE OF OCCURRING.
THE 12Z RUNS ARE MAKING WEDNESDAY A SLIGHTLY MORE INTERESTING
CONVECTIVE DAY PENDING WE REACH FORECAST MAX TEMPS. ON THE PLUS SIDE
OUR CWA IS FORECAST TO BE IN THE ENTRANCE REGION OF THE H2.5 JET,
HAVE DECENT FORECAST MID LEVEL DRY AIR AND A LINGERING THETA E AXIS
OVER NJ AND DE. ON THE MINUS SIDE FORECAST 850MB WINDS ARE FORECAST
TO BE WEST AND WE HAVE ALREADY SEEN INSTANCES WHERE THIS HAS MUTED
CONVECTIVE STRENGTH AND EVEN OCCURRENCE SO FAR THIS YEAR. MAY BE WHY
WHILE 12HR STAT POPS ARE LIKELY, THE SIX HOUR FORMULAS REMAIN CLOSER
TO LOW CHANCE. ITS SOMETHING TO FOLLOW IN THE DAYS AHEAD. WHILE THE
GFS FCST SFC DEW POINTS ARE TOO HIGH, THE WRF-NMMB SEEM MORE LOGICAL
AND WITH THEIR STRONGER WIND FIELD SOME PULSE TYPE STRONG MAYBE SEVERE
TSTMS COULD HAPPEN. AGAIN PERFECT PROGGING CAPS OR THE LACK
THEREOF AT 54-60HRS IS FRAUGHT WITH DANGER, RIGHT NOW IT DOES NOT
DEVELOP IN TIME. FCST 925MB TEMPS AND A WARM START SUPPORT STAT
GUIDANCE MAX TEMPS.
WE WILL MAINTAIN LOW CHANCES EARLY WEDNESDAY NIGHT AND THEN CLEAR
OUR CWA LATE. GETTING CLOSER TO THOSE SUMMER TIME SCENARIOS WHERE
THE DRY(ER) AIR IS NOT REALIZED UNTIL MIXING THE NEXT DAY. WITH THAT
SAID BELIEVE BECAUSE OF HIER DEWPOINTS GFS MOS LOOKS TOO LOW WITH
MINS.
AFTER THAT THE MODELS HAVE BEEN PRETTY CONSISTENT WITH GIVING OUR
CWA TWO SEASONABLY PLEASANT DAYS ON THURSDAY AND FRIDAY WITH GREATER
UNCERTAINTY AS TO THE SOUTHEAST ATLANTIC SYSTEM AS WE MOVE THROUGH
THE WEEKEND AND EARLY NEXT WEEK. THE HIGH PRESSURE SYSTEM IS NOW
FORECAST TO BUILD MORE OVER THE FORECAST AREA ON SATURDAY SO THE
ONSHORE FLOW DOES NOT LOOK AS IMPRESSIVE. THEN THE QUESTION COMES
TO THE EVOLUTION OF THE SYSTEM BEYOND THAT. THE 00Z MODEL RUNS
WERE IN BETTER AGREEMENT ABOUT THE SYSTEM GOING TOO FAR OFFSHORE
TO AFFECT US. THE 12Z RUN IS BACK TO A MORE OF A DIVERGENT LOOK
WITH THE GFS AND CAN GGEM REMAINING MORE PROGRESSIVE, THE UKMET
CAPTURING THE LOW CLOSER TO THE COAST WITH THE ECMWF COMING CLOSE
TO THE LEGAL LIMITS FOR RETROGRADING A LOW WESTWARD. THIS IS
OBVIOUSLY TOWARD THE END OF THE DETERMINISTIC FORECASTS AND UNCERTAINTY
DOES EXIST. THE UKMET SOLUTION WOULD BE A MORE METEOROLOGICALLY
CONSISTENT SOLUTION IF THE LOW WAS TO AFFECT US. GIVEN THAT THE
ENSEMBLE MEANS, EVEN THE ECMWF`S ARE MORE PROGRESSIVE AND OR SHOW A
REX BLOCK PROTECTING US, WE WILL KEEP THE FORECAST DRY FOR NOW.
&&
.AVIATION /21Z MONDAY THROUGH SATURDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.
MOSTLY VFR CONDITIONS ARE STARTING OFF THE FORECAST, WITH SOME
SCATTERED MVFR AND/OR IFR AT A FEW PLACES. WITH THE SCATTERED
SHOWERS ACROSS THE AREA, WE ARE NOT CONFIDENT ENOUGH THAT MVFR
CONDITIONS WILL NOT OCCUR, SO WE WILL KEEP A TEMPO GROUP FOR MVFR
CONDITIONS, IFR WHERE IT OCCURS, FOR THE REMAINDER OF THE AFTERNOON.
GUIDANCE DOES INDICATE THAT WE SHOULD EVENTUALLY LOWER TO MVFR
EVERYWHERE THIS EVENING, THEN LOWER TO IFR TONIGHT INTO TUESDAY AS
MODERATE/HEAVY RAIN MOVES IN.
ONE INITIAL ROUND OF RAIN IS MOVING THROUGH NOW, WHICH IS PROVIDING
THE BRIEF SCATTERED MVFR/IFR CONDITIONS. ANOTHER BATCH OF RAIN THAT
IS OVER CENTRAL VIRGINA MAY MOVE INTO OUR AREA AROUND SUNSET THIS
EVENING. ANOTHER ROUND OF RAIN, WHICH MAY BE THE HEAVIEST SHOULD
MOVE INTO OUR AREA AFTER MIDNIGHT TONIGHT, AND SHOULD CONTINUE
THROUGH THE MORNING HOURS TUESDAY.
ONCE CONDITIONS DROP TO IFR TONIGHT, THEY SHOULD CONTINUE INTO THE
MORNING TUESDAY, THEN EVENTUALLY LIFT TO MVFR BY MID-DAY. ACTUALLY
BY THE AFTERNOON, WE MAY BECOME VFR AT MANY PLACES. THERE IS THE
POSSIBILITY FOR THUNDERSTORMS ON TUESDAY, BUT WE DO NOT HAVE THEM IN
THE TAFS SINCE IT IS A SMALL CHANCE AT THIS TIME.
OUTLOOK...
TUESDAY (REST OF) AFTERNOON AND NIGHT...MVFR WITH IFR AT TIMES
FIRST WITH PERIODS OF RAIN AND PERHAPS A THUNDERSTORM, THEN MAINLY
DUE TO LOW CLOUDS AT NIGHT. THE RAIN IS EXPECTED TO TAPER OFF BY
TUESDAY NIGHT. HIGH CONFIDENCE.
WEDNESDAY...MVFR TO LOCALLY IFR IN POSSIBLE MORNING LOW CLOUDS OR
FOG, THEN IMPROVING TO VFR. A FEW SHOWERS OR THUNDERSTORMS ARE
POSSIBLE WITH MVFR CONDITIONS LATER IN THE DAY INTO THE EARLY EVENING.
AVERAGE CONFIDENCE.
WEDNESDAY NIGHT...VFR MVFR POSSIBLE AT MORE RURAL AIRPORTS.
CONFIDENCE AVERAGE.
THURSDAY THROUGH SATURDAY...VFR. HIGH CONFIDENCE FOR THURSDAY AND
FRIDAY. AVERAGE CONFIDENCE SATURDAY.
&&
.MARINE...
A SMALL CRAFT ADVISORY WILL REMAIN IN EFFECT FOR THE OCEAN THROUGH
TUESDAY NIGHT FOR SEAS. EVEN THROUGH SEAS ARE ONLY AROUND 2-3 FEET
LATE THIS AFTERNOON, THEY ARE FORECAST TO INCREASE TO 5 FEET
TONIGHT, AND SHOULD REMAIN ABOVE 5 FEET FOR THE NEXT COUPLE OF DAYS.
WINDS ARE EXPECTED TO INCREASE THROUGH TONIGHT INTO TUESDAY, AND MAY
GET CLOSE TO 25 KNOTS, MAINLY ALONG THE OCEAN FRONT, LATE TONIGHT
INTO TUESDAY. WE ARE NOT EXPECTING THE WINDS TO INCREASE TO SMALL
CRAFT LEVELS ON THE DELAWARE BAY, BUT THEY MAY GET CLOSE WITH GUSTS
AROUND 20-25 KNOTS.
OUTLOOK...
SMALL CRAFT ADVISORY CONDITIONS PARTICULARLY FOR THE SOUTHERLY SWELL
SEAS ON OUR OCEAN WATERS SHOULD CONTINUE INTO TUESDAY NIGHT INTO
WEDNESDAY AND MAY VERY WELL LINGER INTO MOST OF WEDNESDAY NIGHT.
AFTER THE SECONDARY FRONT CLEARS THE REGION, THE NORTHERLY FLOW DOES
NOT APPEAR STRONG ENOUGH TO GENERATE SMALL CRAFT CONDITIONS
CAUSED BY EITHER SEAS OR WINDS. WHILE UNCERTAINTY EXISTS ABOUT THE
SOUTHEAST COAST SYSTEM FOR SUNDAY AND MONDAY, THROUGH SATURDAY IT
LOOKS AS THOUGH THE HIGH PRESSURE SYSTEM WILL SETTLE CLOSE ENOUGH
TO THE AREA TO NOT BE ABLE TO GENERATE MUCH OF A LONG ONSHORE
FETCH FOR OUR MARINE AREA INTO SATURDAY.
&&
.HYDROLOGY...
THE SURFACE FRONT THAT HAS STALLED ACROSS THE SOUTHERN POCONOS AND
LEHIGH VALLEY WILL ACT AS A CONDUIT FOR THE POTENTIAL FOR HEAVY RAIN
TONIGHT INTO TUESDAY. AT THIS TIME...MODEL OVERALL QPF HAS EITHER
LOWERED OR HAS THE AXIS OF HEAVIEST RAIN POSITIONED NORTHWEST OF
THE AREA. FOR THAT REASON...NO FLOOD WATCH WILL BE ISSUED.
THE SURFACE FRONT IS EXPECTED TO STALL OVER EVEN BE NUDGED BACK WEST
BY THE SURFACE HIGH OFF THE MID ATLANTIC COAST. THE POSITIONING OF
THE FRONT WILL BE ONE OF THE KEYS TO THE HEAVY RAIN FORECAST...AS IT
ACTS AS THE FOCUSING MECHANISM FOR THE MOIST THETA E LADEN AIR. A
WEAK SHORT WAVE RIDING OUT AHEAD OF THE THE LONG WAVE TROUGH CARVED
OUT OVER THE MISSISSIPPI VALLEY WILL FOCUS THE HEAVY RAIN LATE
THIS EVENING...JUST TO THE SOUTHWEST OF THE AREA.
AT ABOUT THE SAME TIME...A LOW LEVEL JET WILL STREAK NORTHEAST JUST
TO THE EAST OF THE SURFACE FRONT. WHILE THERE COULD BE SOME ELEVATED
INSTABILITY ASSOCIATED WITH THE LOW LEVEL JET...IT DOES NOT SEEM AS
THOUGH DEEP CONVECTION WILL BE AN IMPORTANT COMPONENT TO THE HEAVY
RAIN THREAT. INSTEAD...WARM PROCESSES SHOULD DOMINATE THE
PRECIPITATION GENERATION...AS PRECIPITABLE WATER VALUES REACH AROUND
1.50 INCHES.
AS THE SHORT WAVE PASSES LATE TONIGHT...THE CORE OF THE HEAVIEST
RAIN SHOULD BE JUST AHEAD OF IT. THE AREAS MOST LIKELY TO BE
IMPACTED BY THE HEAVY RAIN ARE THE LEHIGH VALLEY...SOUTHERN POCONOS
AND POSSIBLY NORTHWEST NEW JERSEY. THIS SLUG OF HEAVY RAIN PROBABLY
EXITS TO THE NORTHEAST TUESDAY MORNING.
AS THIS POINT...IT APPEARS AS THOUGH AS MUCH AS 2 INCHES OF RAIN
COULD FALL OVER PORTIONS OF THE LEHIGH VALLEY AND THE HIGHER TERRAIN
(IN ABOUT 12 HOURS). THIS NUMBER IS CONSIDERABLY BELOW THE FLASH
FLOOD AND HEADWATER GUIDANCE NUMBERS FOR THE 12 HOUR PERIOD ENDING
TUESDAY MORNING. WHILE SOME OF THE MEMBERS OF THE MMEFS GUIDANCE
SUGGEST THAT SOME OF OUR FORECAST POINTS COULD REACH CAUTION STAGE
WITH THE HEAVY RAIN...THE LATEST RIVER FORECASTS DO NOT.
SHOULD THE AXIS OF HEAVIEST RAIN FALL FURTHER TO THE EAST...THE
SMALLER RIVERS AND CREEKS OF NORTHERN DELAWARE AND SOUTHEAST
PENNSYLVANIA COULD BE AFFECT. RIGHT NOW...APPEARS AS THOUGH WE WOULD
NEED CLOSE TO 2.5 INCHES IN ABOUT 12 HOURS FOR THESE QUICK
RESPONDERS TO BECOME A PROBLEM. AS OF THIS AFTERNOON...WE DO NOT
EXPECT THAT TO HAPPEN. FOR TUESDAY, PERIODS OF RAIN SOME OF WHICH
COULD BE HEAVY WILL BE SLIDING EASTWARD ACROSS THE REGION ALONG
WITH THE LOW-LEVEL JET. IT APPEARS THAT THE HEAVIER RAIN MAY BE
SPREAD OUT ENOUGH DESPITE PERHAPS SOME EMBEDDED CONVECTIVE
ELEMENTS. THEREFORE BASED ON ALL OF THE ABOVE, WE WILL HOLD OFF ON
THE FLOOD WATCH AND CONTINUE A MENTION IN THE HAZARDOUS WEATHER
OUTLOOK.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT WEDNESDAY FOR ANZ450>455.
&&
$$
SYNOPSIS...GIGI/GORSE
NEAR TERM...ROBERTSON
SHORT TERM...ROBERTSON
LONG TERM...GIGI
AVIATION...GIGI/GORSE/ROBERTSON
MARINE...GIGI/ROBERTSON
HYDROLOGY...GIGI/GORSE/HAYES
000
FXUS61 KPHI 141938
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
338 PM EDT MON MAY 14 2012
.SYNOPSIS...
A FRONTAL BOUNDARY WILL STALL OVER THE FORECAST AREA THROUGH TUESDAY
AS A WEAK AREA OF LOW PRESSURE TRACKS ALONG IT. THE FRONT AND LOW
WILL THEN MOVE AWAY FROM THE MID ATLANTIC TUESDAY NIGHT AS A
SECONDARY COLD FRONT MOVES THROUGH LATER ON WEDNESDAY. HIGH
PRESSURE IS FORECAST TO BUILD INTO THE REGION THURSDAY AND FRIDAY,
THEN SHIFT INTO NEW ENGLAND AND THE CANADIAN MARITIMES ON SUNDAY AND
MONDAY. A LOW PRESSURE SYSTEM IS FORECAST TO DEVELOP OFF THE
SOUTHEASTERN UNITED STATES COAST DURING THE WEEKEND AND THEN DRIFT
SLOWLY OFFSHORE THROUGH MONDAY.
&&
.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
QUITE AN UNSETTLED PERIOD EXPECTED TONIGHT THROUGH TUESDAY.
SYNOPTICALLY WE HAVE A WEAK STATIONARY BOUNDARY THAT IS BEGINNING TO
WASH OUT ON OUR WESTERN BORDERS, WITH A BROAD MID/UPPER TROUGH
EXTENDING FORM THE OHIO RIVER VALLEY SOUTHWESTWARD THROUGH THE
SOUTHERN PLAINS. SEVERAL SHORT WAVES ARE EXPECTED TO CROSS OUR AREA
IN THE FLOW ALOFT, WHICH WILL GIVE US A FEW PERIODS OF PRECIPITATION.
THE FIRST WAVE OF PRECIPITATION IS MOVING ACROSS OUR WESTERN ZONES
AND JUST TO OUR WEST THIS AFTERNOON AND WILL CONTINUE INTO THE
EVENING AHEAD OF A WEAK VORT MAX/SHORT WAVE. THE HEAVIEST AND MOST
WIDESPREAD RAIN WILL REMAIN MOSTLY TO OUR WEST, BUT THERE STILL
COULD BE SOME SHOWER ACTIVITY ACROSS THE ENTIRE AREA. THEREFORE WE
HAVE THE HIGHEST POPS OUT WEST, WITH LOWEST EAST THIS EVENING.
THE NEXT ROUND IS EXPECTED TO MOVE INTO THE AREA AROUND OR SHORTLY
AFTER MIDNIGHT WITH THE NEXT VORT MAX/SHORT WAVE. ANOTHER WAVE OF
LOW PRESSURE IS EXPECTED TO DEVELOP ALONG THE STALLED OUT BOUNDARY
AND MOVE TOWARD OUR AREA, WHILE THE PWATS INCREASE AHEAD OF THIS
SHORTWAVE. THEREFORE, WE EXPECT THE HEAVIEST RAIN TO BEGIN TO SPREAD
ACROSS THE AREA AROUND MIDNIGHT AND CONTINUE THROUGH DAYBREAK AS
THESE FEATURES SLOWLY MOVE EASTWARD.
FOR QPF AMOUNTS AND HYDROLOGICAL INFORMATION, PLEASE REFER TO THE
HYDROLOGY SECTION.
FOR TEMPERATURES TONIGHT, WE DECIDED TO TAKE A BLEND OF THE STAT
GUIDANCE SINCE THEY WERE RELATIVELY CLOSE, THOUGH WE DID STAY CLOSER
TO THE `SLIGHTLY` COOLER GFS.
&&
.SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/...
WE EXPECT RAIN TO BE ONGOING ACROSS MUCH OF THE AREA AT DAYBREAK
TUESDAY. THE AFOREMENTIONED SHORT WAVE WILL MAKE ITS WAY THROUGH THE
AREA EARLY IN THE DAY, BUT THE STALLED OUT BOUNDARY WILL REMAIN
ALONG THE WESTERN AREA OF THE FORECAST AREA. ANOTHER WEAK SHORT WAVE
MAY MOVE THROUGH DURING THE DAY, AND WITH THE PWATS REMAINING
RELATIVELY HIGH, WE SHOULD CONTINUE TO GET SHOWERS THROUGH MUCH OF
THE DAY. HOWEVER, AS MENTIONED BEFORE, THE HIGHEST PWATS ARE
EXPECTED TO BE THROUGH THE MORNING, SO THIS MAY BE THE TIME OF
HEAVIEST RAIN.
THERE IS SOME INSTABILITY FORECAST FOR THE AFTERNOON, SO WE WILL
INCLUDED A CHANCE OF THUNDERSTORMS ACROSS THE ENTIRE FORECAST AREA.
THE SPC HAS OUR OUR AREA UNDER MOSTLY GENERAL THUNDERSTORM, WITH
/SEE TEXT/ EXTENDING ACROSS OUR SOUTHERN HALF/TWO-THIRDS. IF ANY
THUNDERSTORMS DO DEVELOP, THEY COULD CONTAIN HEAVY RAIN, GUSTY
WINDS, IN ADDITION TO THE FREQUENT LIGHTNING. MID-LEVEL LAPSE RATES
LOOK LIKE THEY MAY STEEPEN SLIGHTLY DURING THE AFTERNOON, SO SOME
SMALL HAIL IS NOT OUT OF THE QUESTION.
FOR TEMPERATURES, WE BLENDED THE STAT GUIDANCE, WITH A BIT OF THE
COOLER ECMWF, BUT KEPT CLOSER `WARMER` GFS.
&&
.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
ALL OF THE ACTIVE WEATHER IN THE LONG TERM REMAINS AT THE START. THE
WRF-NMMB 500MB INITIALIZATION LOOKS SLIGHTLY BETTER THAN THE GFS.
THE GFS QPF VERIFICATION THOUGH IS OFF TO A BETTER START THAN THE
WRF-NMMB. DP/DTING THE EVOLUTION OF THE CENTRAL CONUS TROF IS
FINDING IT NOT AS SHARP WITH VERIFYING TIME. CONVERSELY THE
TRAILING FRONT AND TROF IS DEEPENING. SUFFICE WITHOUT A CLEAR
WINNER, WE ARE GOING TO GO WITH A MODELING CONSENSUS IN THIS PART
OF THE FORECAST.
THE DOMESTIC MODELS ARE SLOWER THAN OTHER MODELS IN ENDING THE PCPN
ON TUESDAY NIGHT. WHILE THE STRONGER SYNOPTIC SCALE FORCING APPEARS
TO BE DONE BY THEN, DO NOT BELIEVE IT WILL ALL SHUT DOWN THAT
QUICKLY, SO WE WILL COMPROMISE BETWEEN CONTINUITY AND LATEST
GUIDANCE AND TRAIL OFF CHANCES AS THE NIGHT CONTINUES. FCST
INSTABILITY ALOFT WOULD SUPPORT THUNDER THROUGH THE NIGHT, BUT
WITHOUT ANY FCST WAA, WE TRANSITIONED TO JUST SHOWERS AFTER
MIDNIGHT. NO AIR MASS CHANGE, SO WE BELIEVE THE HIGHER STAT GUIDANCE
STANDS A BETTER CHANCE OF OCCURRING.
THE 12Z RUNS ARE MAKING WEDNESDAY A SLIGHTLY MORE INTERESTING
CONVECTIVE DAY PENDING WE REACH FORECAST MAX TEMPS. ON THE PLUS SIDE
OUR CWA IS FORECAST TO BE IN THE ENTRANCE REGION OF THE H2.5 JET,
HAVE DECENT FORECAST MID LEVEL DRY AIR AND A LINGERING THETA E AXIS
OVER NJ AND DE. ON THE MINUS SIDE FORECAST 850MB WINDS ARE FORECAST
TO BE WEST AND WE HAVE ALREADY SEEN INSTANCES WHERE THIS HAS MUTED
CONVECTIVE STRENGTH AND EVEN OCCURRENCE SO FAR THIS YEAR. MAY BE WHY
WHILE 12HR STAT POPS ARE LIKELY, THE SIX HOUR FORMULAS REMAIN CLOSER
TO LOW CHANCE. ITS SOMETHING TO FOLLOW IN THE DAYS AHEAD. WHILE THE
GFS FCST SFC DEW POINTS ARE TOO HIGH, THE WRF-NMMB SEEM MORE LOGICAL
AND WITH THEIR STRONGER WIND FIELD SOME PULSE TYPE STRONG MAYBE SEVERE
TSTMS COULD HAPPEN. AGAIN PERFECT PROGGING CAPS OR THE LACK
THEREOF AT 54-60HRS IS FRAUGHT WITH DANGER, RIGHT NOW IT DOES NOT
DEVELOP IN TIME. FCST 925MB TEMPS AND A WARM START SUPPORT STAT
GUIDANCE MAX TEMPS.
WE WILL MAINTAIN LOW CHANCES EARLY WEDNESDAY NIGHT AND THEN CLEAR
OUR CWA LATE. GETTING CLOSER TO THOSE SUMMER TIME SCENARIOS WHERE
THE DRY(ER) AIR IS NOT REALIZED UNTIL MIXING THE NEXT DAY. WITH THAT
SAID BELIEVE BECAUSE OF HIER DEWPOINTS GFS MOS LOOKS TOO LOW WITH
MINS.
AFTER THAT THE MODELS HAVE BEEN PRETTY CONSISTENT WITH GIVING OUR
CWA TWO SEASONABLY PLEASANT DAYS ON THURSDAY AND FRIDAY WITH GREATER
UNCERTAINTY AS TO THE SOUTHEAST ATLANTIC SYSTEM AS WE MOVE THROUGH
THE WEEKEND AND EARLY NEXT WEEK. THE HIGH PRESSURE SYSTEM IS NOW
FORECAST TO BUILD MORE OVER THE FORECAST AREA ON SATURDAY SO THE
ONSHORE FLOW DOES NOT LOOK AS IMPRESSIVE. THEN THE QUESTION COMES
TO THE EVOLUTION OF THE SYSTEM BEYOND THAT. THE 00Z MODEL RUNS
WERE IN BETTER AGREEMENT ABOUT THE SYSTEM GOING TOO FAR OFFSHORE
TO AFFECT US. THE 12Z RUN IS BACK TO A MORE OF A DIVERGENT LOOK
WITH THE GFS AND CAN GGEM REMAINING MORE PROGRESSIVE, THE UKMET
CAPTURING THE LOW CLOSER TO THE COAST WITH THE ECMWF COMING CLOSE
TO THE LEGAL LIMITS FOR RETROGRADING A LOW WESTWARD. THIS IS
OBVIOUSLY TOWARD THE END OF THE DETERMINISTIC FORECASTS AND UNCERTAINTY
DOES EXIST. THE UKMET SOLUTION WOULD BE A MORE METEOROLOGICALLY
CONSISTENT SOLUTION IF THE LOW WAS TO AFFECT US. GIVEN THAT THE
ENSEMBLE MEANS, EVEN THE ECMWF`S ARE MORE PROGRESSIVE AND OR SHOW A
REX BLOCK PROTECTING US, WE WILL KEEP THE FORECAST DRY FOR NOW.
&&
.AVIATION /20Z MONDAY THROUGH SATURDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.
OUTLOOK...
TUESDAY (REST OF) AFTERNOON AND NIGHT...MVFR WITH IFR AT TIMES
FIRST WITH PERIODS OF RAIN AND PERHAPS A THUNDERSTORM, THEN MAINLY
DUE TO LOW CLOUDS AT NIGHT. THE RAIN IS EXPECTED TO TAPER OFF BY
TUESDAY NIGHT. HIGH CONFIDENCE.
WEDNESDAY...MVFR TO LOCALLY IFR IN POSSIBLE MORNING LOW CLOUDS OR
FOG, THEN IMPROVING TO VFR. A FEW SHOWERS OR THUNDERSTORMS ARE
POSSIBLE WITH MVFR CONDITIONS LATER IN THE DAY INTO THE EARLY EVENING.
AVERAGE CONFIDENCE.
WEDNESDAY NIGHT...VFR MVFR POSSIBLE AT MORE RURAL AIRPORTS.
CONFIDENCE AVERAGE.
THURSDAY THROUGH SATURDAY...VFR. HIGH CONFIDENCE FOR THURSDAY AND
FRIDAY. AVERAGE CONFIDENCE SATURDAY.
&&
.MARINE...
OUTLOOK...
SMALL CRAFT ADVISORY CONDITIONS PARTICULARLY FOR THE SOUTHERLY SWELL
SEAS ON OUR OCEAN WATERS SHOULD CONTINUE INTO TUESDAY NIGHT INTO
WEDNESDAY AND MAY VERY WELL LINGER INTO MOST OF WEDNESDAY NIGHT.
AFTER THE SECONDARY FRONT CLEARS THE REGION, THE NORTHERLY FLOW DOES
NOT APPEAR STRONG ENOUGH TO GENERATE SMALL CRAFT CONDITIONS
CAUSED BY EITHER SEAS OR WINDS. WHILE UNCERTAINTY EXISTS ABOUT THE
SOUTHEAST COAST SYSTEM FOR SUNDAY AND MONDAY, THROUGH SATURDAY IT
LOOKS AS THOUGH THE HIGH PRESSURE SYSTEM WILL SETTLE CLOSE ENOUGH
TO THE AREA TO NOT BE ABLE TO GENERATE MUCH OF A LONG ONSHORE
FETCH FOR OUR MARINE AREA INTO SATURDAY.
&&
.HYDROLOGY...
THE SURFACE FRONT THAT HAS STALLED ACROSS THE SOUTHERN POCONOS AND
LEHIGH VALLEY WILL ACT AS A CONDUIT FOR THE POTENTIAL FOR HEAVY RAIN
TONIGHT INTO TUESDAY. AT THIS TIME...MODEL OVERALL QPF HAS EITHER
LOWERED OR HAS THE AXIS OF HEAVIEST RAIN POSITIONED NORTHWEST OF
THE AREA. FOR THAT REASON...NO FLOOD WATCH WILL BE ISSUED.
THE SURFACE FRONT IS EXPECTED TO STALL OVER EVEN BE NUDGED BACK WEST
BY THE SURFACE HIGH OFF THE MID ATLANTIC COAST. THE POSITIONING OF
THE FRONT WILL BE ONE OF THE KEYS TO THE HEAVY RAIN FORECAST...AS IT
ACTS AS THE FOCUSING MECHANISM FOR THE MOIST THETA E LADEN AIR. A
WEAK SHORT WAVE RIDING OUT AHEAD OF THE THE LONG WAVE TROUGH CARVED
OUT OVER THE MISSISSIPPI VALLEY WILL FOCUS THE HEAVY RAIN LATE
THIS EVENING...JUST TO THE SOUTHWEST OF THE AREA.
AT ABOUT THE SAME TIME...A LOW LEVEL JET WILL STREAK NORTHEAST JUST
TO THE EAST OF THE SURFACE FRONT. WHILE THERE COULD BE SOME ELEVATED
INSTABILITY ASSOCIATED WITH THE LOW LEVEL JET...IT DOES NOT SEEM AS
THOUGH DEEP CONVECTION WILL BE AN IMPORTANT COMPONENT TO THE HEAVY
RAIN THREAT. INSTEAD...WARM PROCESSES SHOULD DOMINATE THE
PRECIPITATION GENERATION...AS PRECIPITABLE WATER VALUES REACH AROUND
1.50 INCHES.
AS THE SHORT WAVE PASSES LATE TONIGHT...THE CORE OF THE HEAVIEST
RAIN SHOULD BE JUST AHEAD OF IT. THE AREAS MOST LIKELY TO BE
IMPACTED BY THE HEAVY RAIN ARE THE LEHIGH VALLEY...SOUTHERN POCONOS
AND POSSIBLY NORTHWEST NEW JERSEY. THIS SLUG OF HEAVY RAIN PROBABLY
EXITS TO THE NORTHEAST TUESDAY MORNING.
AS THIS POINT...IT APPEARS AS THOUGH AS MUCH AS 2 INCHES OF RAIN
COULD FALL OVER PORTIONS OF THE LEHIGH VALLEY AND THE HIGHER TERRAIN
(IN ABOUT 12 HOURS). THIS NUMBER IS CONSIDERABLY BELOW THE FLASH
FLOOD AND HEADWATER GUIDANCE NUMBERS FOR THE 12 HOUR PERIOD ENDING
TUESDAY MORNING. WHILE SOME OF THE MEMBERS OF THE MMEFS GUIDANCE
SUGGEST THAT SOME OF OUR FORECAST POINTS COULD REACH CAUTION STAGE
WITH THE HEAVY RAIN...THE LATEST RIVER FORECASTS DO NOT.
SHOULD THE AXIS OF HEAVIEST RAIN FALL FURTHER TO THE EAST...THE
SMALLER RIVERS AND CREEKS OF NORTHERN DELAWARE AND SOUTHEAST
PENNSYLVANIA COULD BE AFFECT. RIGHT NOW...APPEARS AS THOUGH WE WOULD
NEED CLOSE TO 2.5 INCHES IN ABOUT 12 HOURS FOR THESE QUICK
RESPONDERS TO BECOME A PROBLEM. AS OF THIS AFTERNOON...WE DO NOT
EXPECT THAT TO HAPPEN. FOR TUESDAY, PERIODS OF RAIN SOME OF WHICH
COULD BE HEAVY WILL BE SLIDING EASTWARD ACROSS THE REGION ALONG
WITH THE LOW-LEVEL JET. IT APPEARS THAT THE HEAVIER RAIN MAY BE
SPREAD OUT ENOUGH DESPITE PERHAPS SOME EMBEDDED CONVECTIVE
ELEMENTS. THEREFORE BASED ON ALL OF THE ABOVE, WE WILL HOLD OFF ON
THE FLOOD WATCH AND CONTINUE A MENTION IN THE HAZARDOUS WEATHER
OUTLOOK.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EDT TUESDAY FOR ANZ450>455.
&&
$$
SYNOPSIS...GIGI/GORSE
NEAR TERM...ROBERTSON
SHORT TERM...ROBERTSON
LONG TERM...GIGI
AVIATION...GIGI/GORSE/ROBERTSON
MARINE...GIGI/ROBERTSON
HYDROLOGY...GIG/GORSE/HAYES
000
FXUS61 KPHI 141712
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
112 PM EDT MON MAY 14 2012
.SYNOPSIS...
A FRONTAL BOUNDARY WILL STALL IN OUR VICINITY THROUGH TUESDAY AS
A WEAK AREA OF LOW PRESSURE TRACKS ALONG IT. THE FRONT AND LOW
WILL THEN MOVE AWAY FROM THE MID ATLANTIC TUESDAY NIGHT AS A
SECONDARY COLD FRONT MOVES THROUGH LATER WEDNESDAY. HIGH PRESSURE
IS FORECAST TO BUILD INTO THE REGION THURSDAY AND FRIDAY, THEN
SHIFT INTO NEW ENGLAND AND THE CANADIAN MARITIMES DURING THE
WEEKEND. A LOW PRESSURE SYSTEM IS FORECAST TO DEVELOP OFF THE
SOUTHEASTERN UNITED STATES COAST DURING THE WEEKEND.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
A FRONTAL BOUNDARY REMAINS NEARLY STATIONARY RIGHT ALONG OUR
WEST/NORTHWESTERN ZONES AND SHOULD NOT MOVE MUCH THROUGH THE DAY.
SHOWERS CONTINUE ACROSS THE AREA INCREASING IN COVERAGE, MAINLY
ACROSS OUR WESTERN AREAS, AS RAIN CONTINUES TO MOVE NORTHEASTWARD
THROUGH THE REGION.
THE FORECAST FOR LATER TODAY AND ESPECIALLY TONIGHT IS THE
POTENTIAL FOR HEAVY RAIN. FOR NOW...WE WILL FORGO THE FLOOD WATCH
ROUTE...AS IT APPEARS AS THOUGH THE AXIS OF HEAVIEST RAIN COULD
FALL JUST TO THE WEST. MORE ON THE FLOOD THREAT IS CONTAINED IN
THE HYDROLOGY SECTION BELOW.
A LARGE AREA OF RAIN MOVING NORTHEASTWARD THROUGH CENTRAL
PENNSYLVANIA, APPEARS TO HAVE A TIE TO THE LOW LEVEL INFLOW OF
MOIST THETA E RICH AIR FROM THE CENTRAL AND EASTERN GULF OF
MEXICO. HOWEVER...IT APPEARS AS THOUGH THE HEAVIEST RAIN WILL HAVE
TO WAIT FOR A SHORT WAVE IN THE DEEP MID LEVEL SOUTHWEST
FLOW...AND THAT MAY NOT ARRIVE UNTIL LATE THIS AFTERNOON OR THIS
EVENING.
JUST EAST OF THE FRONT...NEAR AND SHORT TERM MODELS ARE SHOWING
MARGINAL INSTABILITY...MAINLY CLOSE TO WHERE BREAKS IN THE CLOUDS
COULD OCCUR. WHILE THE POTENTIAL FOR THUNDER IS NOT HIGH (MARGINAL
SHEAR ARRIVING LATE AND POOR MID LEVEL LAPSE RATES)...A SLIGHT
CHANCE OF THUNDER WAS RETAINED IN THE FORECAST FOR THE ABOVE
REASONS.
NEAR AND SHORT TERM MODELS ARE SHOWING LOW LEVEL DRYING...NOW OVER
EASTERN NORTH CAROLINA (WHERE SKIES ARE CLEAR) WILL CROSS SOUTHERN
DELAWARE AND EASTERN JERSEY THROUGH THIS AFTERNOON. THE DRY AIR
SHOULD KEEP THE RAIN AT BAY IN THESE AREAS...AND COULD EVEN ALLOW
THE ABOVE MENTIONED AREAS TO SEE PARTLY SUNNY SKIES FOR A TIME.
ELSEWHERE...SKIES SHOULD REMAIN MOSTLY CLOUDY. FOR THE MOST PART...A
BLEND OF MOS TEMPERATURES WAS USED FOR HIGHS. HOWEVER...THERE IS A
CAVEAT. IF SKIES OVER SOUTHERN AND CENTRAL DELAWARE AND EASTERN NEW
JERSEY CLEAR FOR A TIME...HIGHS IN THESE AREAS COULD BE CLOSER TO
THE WARMER NAM MOS NUMBERS.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM TUESDAY/...
THE MAIN EVENT IS TONIGHT. AS MENTIONED EARLIER...THE HEAVIEST RAIN
APPEARS TO BE TIED TO THE PASSAGE OF A SHORT WAVE NEAR THE FRONT.
THE HIGHEST THETA E AIR RIDES NORTH JUST AHEAD OF THE SHORT WAVE AND
EAST OF THE FRONT. SHORT TERM MODELS (AS WELL AS THE HPC QPF) APPEAR
TO REFLECT THE ABOVE THINKING. AGAIN...THERE COULD BE SOME ELEVATED
CONVECTION AHEAD OF THE SHORT WAVE (AS INSTABILITY IN THE RISING AIR
IS RELEASED)...BUT IT DOES NOT APPEAR TO BE A SIGNIFICANT
CONTRIBUTOR TO THE HEAVY RAIN PROCESS.
RIGHT NOW...IT APPEARS AS THOUGH THE AXIS OF HEAVIEST QPF WILL GALL
WEST OF THE I-95 CORRIDOR (OR THE FALL LINE)...CLOSEST TO THE FRONT.
THIS IS WHERE THE HIGHEST RAIN CHANCES WERE PLACES. FURTHER
EAST...THE RAIN FORECAST BECOMES A BIT MORE NEBULOUS. WITH MOST OF
THE FORCING (AND THE LOW LEVEL FOCUS) TO THE WEST...PARTS OF
SOUTHERN DELAWARE AND EASTERN NEW JERSEY COULD HAVE A FAIRLY RAIN
FREE EVENING.
THE AXIS OF BEST LOW LEVEL THETA E SHOULD SHIFT TO THE EAST AFTER
0600 UTC...AND BE CENTERED ACROSS NORTHERN NEW JERSEY LATE TONIGHT
(IN THE RIGHT REAR QUADRANT OF AN EXITING 200 MB JET) THE SHORT TERM
MODEL QPF FORECAST FOLLOW THIS...AND THE BEST CHANCE OF HEAVY RAIN
LATE TONIGHT SHOULD SHIFT INTO NEW JERSEY. THIS IS WHEN EASTERN
SECTIONS HAVE THE BEST SHOT AT STEADIER RAIN.
FOR THE MOST PART...WITH LITTLE CHANGE IN AIRMASS OVERNIGHT...LOWS
WERE COMPRISED OF A BLEND OF MOS GUIDANCE AN PERSISTENCE.
&&
.LONG TERM /TUESDAY THROUGH SUNDAY/...
THIS TIME FRAME IS ANTICIPATED TO START ON THE UNSETTLED SIDE, THEN
IMPROVING CONDITIONS OCCUR FOR A TIME. THE OVERALL SYNOPTIC SETUP
INVOLVES AN UPPER-LEVEL TROUGH AMPLIFYING FROM THE GREAT LAKES AND
EASTERN CANADA INTO THE NORTHEAST TUESDAY AND WEDNESDAY. THIS WILL
EVENTUALLY KICK OUT A STALLED FRONT AS ANOTHER COLD FRONT EXITS THE
COAST DURING WEDNESDAY. THE TROUGH LOOKS TO WEAKEN SOME THURSDAY
THROUGH FRIDAY, THEN RIDGING ACROSS THE PLAINS SLIDES EASTWARD
SATURDAY AND SUNDAY AS SOME TROUGHING TAKES PLACE INTO THE NORTHERN
PLAINS. A PIECE OF ENERGY HOWEVER SLIDING ACROSS THE SOUTHERN STATES
BECOMES CUT OFF FROM THE MAIN FLOW, AND THIS LOOKS TO TURN INTO A
CLOSED LOW WITH TIME ALONG WITH A SURFACE LOW DEVELOPING OFF THE
SOUTHEASTERN U.S. COAST SATURDAY AND SUNDAY.
FOR TUESDAY, IT APPEARS THE LAST SHORT WAVE ROLLS UP THE STALLED
FRONT ALONG WITH A WEAK LOW REFLECTED AT THE SURFACE. AN AREA OF LOW
TO MID LEVEL CONVERGENCE VERY SLOWLY WORKS ITS WAY EASTWARD ALONG
WITH SOMEWHAT OF A THERMAL RIDGE. THE PW VALUES ARE FORECAST TO BE
AROUND 1.5 INCHES, AND AS AN UPPER-LEVEL TROUGH SHARPENS SOME THE
LOW-LEVEL JET WILL GRADUALLY BE SHIFTING TO OUR EAST WITH TIME. THIS
ALL LEADS TO PLENTY OF LIFT TO ALLOW FOR PERIODS OF RAIN TO MOVE
ACROSS THE REGION. THE MOST ORGANIZED LOOKS TO HOLD INLAND FOR AWHILE
AND TIED CLOSER TO THE LOW TO MID LEVEL CONVERGENCE AXIS. A DEEP
SOUTHERLY FLOW MAY TEND TO FOCUS THE RAIN IN SOUTH TO NORTH BANDS
/TRAINING/, WHICH MAY ENHANCE THE LOCAL RAINFALL FOR AWHILE
ESPECIALLY IF A CONVECTIVE CONTRIBUTION IS PRESENT. THEREFORE, WILL
CARRY A POSSIBLE HEAVY RAIN MENTION FOR MOST OF THE DAY ESPECIALLY
FROM ABOUT THE INTERSTATE 95 CORRIDOR ON WESTWARD. THE RAIN MAY END
UP BEING SPREAD OUT OVER A LONG ENOUGH TIME, THEREFORE NO FLOOD
WATCH WILL BE ISSUED ATTM. THE FORECAST SOUNDINGS REVEAL A RATHER
MOIST ATMOSPHERIC PROFILE. WHILE THERE IS INSTABILITY ALOFT THAT MAY
BECOME SURFACE BASED, THE SHAPE OF THE CAPE IS FORECAST TO BE MOSTLY
SKINNY. THIS MAY RESULT IN NOT ENOUGH ENERGY TO PROMOTE STRONG
ENOUGH UPDRAFTS, THEREFORE LIMITING THE CHARGE SEPARATION THAT CAN
BE ACHIEVED. IF THIS IS THE CASE, WE MAY BE ABLE TO REMOVE THE
THUNDER MENTION. FOR NOW THOUGH, WE INCLUDED A SLIGHT CHC OR
ISOLATED THUNDER FOR MOST OF THE AREA IN THE FORECAST DATABASE.
BASED ON THE SYSTEM MOVING EASTWARD GRADUALLY, THE RAIN SHOULD BE
ON A DOWNWARD TREND TUESDAY NIGHT ESPECIALLY AS THE BETTER FORCING
BEGINS TO SHIFT TO OUR NORTHEAST. THEREFORE WE LOWERED THE POPS
THROUGH THE NIGHT. THERE LOOKS TO BE AN ABUNDANCE OF MOISTURE
REMAINING THOUGH AND WITH LITTLE WIND AT THE SURFACE, LOW CLOUDS AND
SOME FOG MAY REMAIN THROUGH THE NIGHT. GIVEN SOME LOWER CONFIDENCE
IN HOW THIS MAY PLAY OUT, WE DID NOT INTRODUCE FOG ATTM.
FOR WEDNESDAY, THE LEFTOVER INITIAL BOUNDARY SHOULD BE EAST OF OUR
REGION HOWEVER A SECONDARY COLD FRONT WILL MOVE THROUGH LATER IN
THE DAY. THE DAY MAY START OUT WITH AREAS OF LOW CLOUDS AND FOG,
HOWEVER A LOW-LEVEL INVERSION SHOULD BREAK WITH ENOUGH BOUNDARY
LAYER HEATING. THE WINDS LOOK FAIRLY WEAK IN THE LOWER LEVELS,
THEREFORE REAL DEEP MIXING IS NOT ANTICIPATING BUT A FAIR AMOUNT OF
DRYING MAY OCCUR AS THE FLOW STARTS TO TURN WESTERLY. WHILE SOME
INSTABILITY IS FORECAST TO DEVELOP DURING THE DAY AND AHEAD OF THE
SECONDARY FRONT, THE AIRMASS MAY BE A BIT TO DRY ESPECIALLY IN THE
MID LEVELS TO GET MUCH IN THE WAY OF SHOWERS OR THUNDER GOING. IN
ADDITION, THE LOW-LEVEL FLOW MAY TURN WESTERLY WHICH WOULD TEND TO
LIMIT THE CONVERGENCE. FOR NOW, CARRIED LOW CHC POPS DUE TO THE
POTENTIAL FOR A FEW SHOWERS OR A THUNDERSTORM.
FOR THURSDAY AND FRIDAY, AN UPPER-LEVEL TROUGH GRADUALLY LIFTS OUT
OF THE NORTHEAST. A MID LEVEL RIDGE ACROSS THE PLAINS WILL SLIDE
EASTWARD, ALLOWING HIGH PRESSURE AT THE SURFACE TO BUILD INTO THE
NORTHEAST AND MID ATLANTIC. THIS WILL TEND TO BRING QUIET WEATHER TO
THE REGION ALONG WITH LIGHTER WINDS. THE MILD AFTERNOONS COMBINED
WITH LIGHT ENOUGH WINDS MAY ALLOW FOR A SEA BREEZE TO DEVELOP EACH
AFTERNOON, WITH PERHAPS MORE OF AN OVERALL ONSHORE FLOW STARTING TO
TAKE SHAPE AS WE GO THROUGH FRIDAY.
FOR SATURDAY AND SUNDAY, HIGH PRESSURE IS FORECAST TO BUILD INTO NEW
ENGLAND AND THE CANADIAN MARITIMES AS AN AREA OF LOW PRESSURE
DEVELOPS OFF THE SOUTHEASTERN U.S. COAST. THIS LOW LOOKS TO GET
CAPTURED BY A CLOSING OFF UPPER-LEVEL LOW THAT MAY TEND TO MEANDER
TO OUR SOUTH. THE COMBINATION OF HIGH PRESSURE TO THE NORTH AND LOW
PRESSURE TO OUR SOUTH WILL TEND TO INCREASE THE ONSHORE FLOW. THESE
TYPES OF SYSTEMS ARE TOUGH TO FORECAST GIVEN THE TENDENCY FOR A
GRADUAL DRIFT IN FORWARD MOTION. IF THE INCOMING UPPER-LEVEL RIDGE
AMPLIFIES ENOUGH, THE SLOW MOVING LOW TO OUR SOUTH MAY GET HELD AT
BAY OR EVEN SHUNTED OFF TO THE NORTHEAST INSTEAD OF MOVING TO THE
NORTH. EITHER WAY, WE MAY HAVE TO BE ON THE LOOKOUT FOR SOME SHOWERS
TRYING TO MOVE NORTHWARD LATE IN THE WEEKEND. THE ONSHORE FLOW WILL
EVENTUALLY INCREASE THE LOW-LEVEL MOISTURE AND PROBABLY SOME
CLOUDINESS PARTICULARLY FOR THE SECOND HALF OF THE WEEKEND. OUR
CONFIDENCE IS LOWER AS WE GO THROUGH THIS TIME FRAME.
&&
.AVIATION /17Z MONDAY THROUGH FRIDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.
MOSTLY VFR CONDITIONS ARE OCCURRING ACROSS THE TAF SITES, ALTHOUGH
WE CONTINUE TO HAVE SOME IN AND OUT MVFR CONDITIONS AS SHOWERS
MOVE OVER THE TAF SITES, ESPECIALLY WEST OF PHL. WE EXPECT
SHOWERS TO CONTINUE FOR MUCH OF THE DAY, ALTHOUGH COVERAGE MAY
INCREASE MORE TOWARD RDG/ABE DURING THE AFTERNOON AS AN AREA OF
RAIN MOVES NORTHEASTWARD FROM CENTRAL/WESTERN VIRGINIA. THESE
AREAS MAY BECOME PREVAILING MVFR DURING THE AFTERNOON.
ELSEWHERE... SHOWERS ARE EXPECTED TO BE MUCH LESS ORGANIZED. IN
FACT...SHORT TERM MODEL GUIDANCE SUGGESTS DRYING FOR AREAS EAST OF
KPHL.
THE DRY AIR EXITS THIS AFTERNOON...AND ALL TERMINALS SHOULD SEE
MVFR CONDITION FROM EARLY AFTERNOON INTO THE EVENING HOURS.
SOUTHERLY WINDS COULD APPROACH 10 KNOTS THIS AFTERNOON AT
KPHL...POSSIBLY AFFECTING OPERATIONS. FOR TONIGHT....AN AREA OF
RAIN WILL FOLLOW A STALLED FRONT WEST OF KPHL. THIS MEANS IFR
CONDITIONS FOR KRDG AND KABE...AND MAINLY MVFR CONDITIONS
ELSEWHERE.
OUTLOOK...
TUESDAY...MVFR WITH IFR AT TIMES FIRST WITH PERIODS OF RAIN AND
PERHAPS A THUNDERSTORM DURING THE DAY, THEN MAINLY DUE TO LOW CLOUDS
AT NIGHT. THE RAIN IS EXPECTED TO TAPER OFF TUESDAY NIGHT.
WEDNESDAY...MVFR TO LOCALLY IFR IN POSSIBLE MORNING LOW CLOUDS OR
FOG, THEN IMPROVING TO VFR. A FEW SHOWERS OR A THUNDERSTORM ARE
STILL POSSIBLE AS A SECONDARY COLD FRONT MOVES THROUGH LATER IN THE
DAY.
THURSDAY THROUGH FRIDAY...VFR. NORTH WINDS NEAR 10 KNOTS BECOMING
NORTHEAST OR EAST.
&&
.MARINE...
WINDS AND SEAS REMAIN BELOW SMALL CRAFT LIMITS THIS MORNING. THE
LOW LEVEL FLOW SHOULD REMAIN FROM THE SOUTH AND SOUTHWEST
TODAY...AS A LOW LEVEL JET PASSES OVERHEAD LATE THIS AFTERNOON AND
THIS EVENING. MODEL SOUNDINGS SHOW THAT LOW LEVEL STABILITY SHOULD
PRECLUDE MUCH MOMENTUM TRANSFER. THE BEST CHANCE FOR SIGNIFICANT
MOMENTUM TRANSFER LOOKS TO OCCUR BETWEEN 2000 UTC TO ABOUT 0200
UTC MONDAY. AT THIS POINT IT APPEARS AS THOUGH WINDS GUSTS WILL
STAY BELOW 25 KNOTS.
THE CONTINUING SOUTHERLY FETCH WILL...HOWEVER...RESULT IN BUILDING
SEAS THIS AFTERNOON AND THIS EVENING. WHILE THE WNAWAVE MODEL SEAS
HEIGHTS START A BIT HIGH THIS MORNING...BASED ON THE DEVELOPING
FETCH IT IS REASONABLE TO ASSUME THAT SEAS ON THE OCEAN WILL REACH 5
FEET BY LATE AFTERNOON. FOR THIS REASON...A SMALL CRAFT ADVISORY
WILL BE ISSUED FOR THE OCEAN WATERS FOR THIS AFTERNOON AND TONIGHT.
WINDS MAY TEND TO BACK OFF LATER TONIGHT AS THE LOW LEVEL JET
EXITS...AND THIS COULD ALLOW WIND GUSTS TO DROP BELOW 20
KNOTS...ESPECIALLY FOR THE SOUTHERN OCEAN WATERS. THE SOUTHERLY FLOW
SHOULD HAVE BEEN IN PLACE LONG ENOUGH FOR A NEARLY FULLY DEVELOPED
SEA ON THE OCEAN WATERS. FOR NOW...THE OUTPUT FROM THE WNAWAVE MODEL
WAS UNDERCUT A BIT (AS IT TENDS TO OVERDO SEAS ON A SOUTHERLY FLOW).
OUTLOOK...
THE SOUTHERLY FLOW AHEAD OF THE SLOW MOVING FRONTAL BOUNDARY AND
WEAK SURFACE LOW WILL CONTINUE TUESDAY. THIS IS EXPECTED TO CONTINUE
TO BUILD THE SEAS. A LOW-LEVEL JET IS FORECAST TO MOVE ACROSS THE
REGION DURING TUESDAY BEFORE WEAKENING AND SHIFTING TO OUR NORTHEAST
TUESDAY NIGHT INTO WEDNESDAY. THE WINDS AT 925 MB ARE FORECAST TO
INCREASE TO AROUND 30 KNOTS TUESDAY. THE FORECAST SOUNDINGS INDICATE
NEAR SURFACE STABILITY WHICH WOULD TEND TO LIMIT THE VERTICAL
MIXING. WHILE SOME WIND GUSTS COULD NEAR 25 KNOTS TUESDAY, IT
APPEARS ELEVATED SEAS WILL BE THE MAIN HAZARD. THEREFORE, THE SMALL
CRAFT ADVISORY FOR THE OCEAN ZONES WILL GO THROUGH THE DAY TUESDAY
FOR NOW. DESPITE THE WINDS ABOVE THE SURFACE WEAKENING TUESDAY NIGHT
AS THE LOW-LEVEL JET LEAVES THE AREA, ELEVATED SEAS SHOULD TEND TO
GRADUALLY LOWER HOWEVER THE ADVISORY MAY NEED TO BE EXTENDED. A
SECONDARY COLD FRONT THEN MOVES THROUGH LATE WEDNESDAY, HOWEVER THE
PRESSURE GRADIENT BEHIND IT IS NOT FORECAST TO BE ALL THAT STRONG,
THEREFORE THE SEAS SHOULD DROP BELOW ADVISORY CRITERIA DURING
WEDNESDAY AND CONTINUE THURSDAY AND FRIDAY. THE LOW-LEVEL FLOW
THOUGH MAY START TO BECOME ONSHORE LATER THURSDAY AND FRIDAY.
&&
.HYDROLOGY...
THE SURFACE FRONT THAT HAS STALLED ACROSS THE SOUTHERN POCONOS AND
LEHIGH VALLEY WILL ACT AS A CONDUIT FOR THE POTENTIAL FOR HEAVY RAIN
TONIGHT AND EARLY TUESDAY MORNING. AT THIS TIME...IT APPEARS AS
THOUGH THE AXIS OF HEAVIEST RAIN WILL POSITION ITSELF JUST WEST OF
THE AREA. FOR THAT REASON...WE WILL FORGO THE FLOOD WATCH THIS
MORNING.
THE SURFACE FRONT IS EXPECTED TO STALL OVER EVEN BE NUDGED BACK WEST
BY THE SURFACE HIGH OFF THE MID ATLANTIC COAST. THE POSITIONING OF
THE FRONT WILL BE ONE OF THE KEYS TO THE HEAVY RAIN FORECAST...AS IT
ACTS AS THE FOCUSING MECHANISM FOR THE MOIST THETA E LADEN AIR. A
WEAK SHORT WAVE RIDING OUT AHEAD OF THE THE LONG WAVE TROUGH CARVED
OUT OVER THE MISSISSIPPI VALLEY WILL FOCUS THE HEAVY RAIN LATE THIS
AFTERNOON INTO THIS EVENING...JUST TO THE SOUTHWEST OF THE AREA.
AT ABOUT THE SAME TIME...A LOW LEVEL JET WILL STREAK NORTHEAST JUST
TO THE EAST OF THE SURFACE FRONT. WHILE THERE COULD BE SOME ELEVATED
INSTABILITY ASSOCIATED WITH THE LOW LEVEL JET...IT DOES NOT SEEM AS
THOUGH DEEP CONVECTION WILL BE AN IMPORTANT COMPONENT TO THE HEAVY
RAIN THREAT. INSTEAD...WARM PROCESSES SHOULD DOMINATE THE
PRECIPITATION GENERATION...AS PRECIPITABLE WATER VALUES APPROACH
1.60 INCHES.
AS THE SHORT WAVE PASSES TONIGHT...THE CORE OF THE HEAVIEST RAIN
SHOULD BE JUST AHEAD OF IT. THE AREAS MOST LIKELY TO BE IMPACTED BY
THE HEAVY RAIN ARE THE LEHIGH VALLEY...SOUTHERN POCONOS AND POSSIBLY
NORTHWEST NEW JERSEY. THIS SLUG OF HEAVY RAIN PROBABLY EXITS TO THE
NORTHEAST TUESDAY MORNING.
AS THIS POINT...IT APPEARS AS THOUGH AS MUCH AS 2 INCHES OF RAIN
COULD FALL OVER PORTIONS OF THE LEHIGH VALLEY AND THE HIGHER TERRAIN
(IN ABOUT 12 HOURS). THIS NUMBER IS CONSIDERABLY BELOW THE FLASH
FLOOD AND HEADWATER GUIDANCE NUMBERS FOR THE 12 HOUR PERIOD ENDING
TUESDAY MORNING. WHILE SOME OF THE MEMBERS OF THE MMEFS GUIDANCE
SUGGEST THAT SOME OF OUR FORECAST POINTS COULD REACH CAUTION STAGE
WITH THE HEAVY RAIN...THE LATEST RIVER FORECASTS DO NOT.
SHOULD THE AXIS OF HEAVIEST RAIN FALL FURTHER TO THE EAST...THE
SMALLER RIVERS AND CREEKS OF NORTHERN DELAWARE AND SOUTHEAST
PENNSYLVANIA COULD BE AFFECT. RIGHT NOW...APPEARS AS THOUGH WE WOULD
NEED CLOSE TO 2.5 INCHES IN ABOUT 12 HOURS FOR THESE QUICK
RESPONDERS TO BECOME A PROBLEM. AS OF THIS MORNING...WE DO NOT
EXPECT THAT TO HAPPEN. FOR TUESDAY, PERIODS OF RAIN SOME OF WHICH
COULD BE HEAVY WILL BE SLIDING EASTWARD ACROSS THE REGION ALONG
WITH THE LOW-LEVEL JET. IT APPEARS THAT THE HEAVIER RAIN MAY BE
SPREAD OUT ENOUGH DESPITE PERHAPS SOME EMBEDDED CONVECTIVE
ELEMENTS. THEREFORE BASED ON ALL OF THE ABOVE, WE WILL HOLD OFF ON
THE FLOOD WATCH AND CONTINUE A MENTION IN THE HAZARDOUS WEATHER
OUTLOOK.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EDT TUESDAY FOR ANZ450>455.
&&
$$
SYNOPSIS...GORSE
NEAR TERM...HAYES/ROBERTSON/MEOLA
SHORT TERM...HAYES
LONG TERM...GORSE
AVIATION...GORSE/HAYES/ROBERTSON
MARINE...GORSE/HAYES
HYDROLOGY...HAYES/GORSE
000
FXUS61 KPHI 141451
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1051 AM EDT MON MAY 14 2012
.SYNOPSIS...
A FRONTAL BOUNDARY WILL TEND TO STALL IN OUR VICINITY TODAY THROUGH
TUESDAY AS A WEAK AREA OF LOW PRESSURE TRACKS ALONG IT. THE FRONT
AND LOW WILL THEN MOVE AWAY FROM THE MID ATLANTIC TUESDAY NIGHT AS A
SECONDARY COLD FRONT MOVES THROUGH LATER WEDNESDAY. HIGH PRESSURE IS
FORECAST TO BUILD INTO THE REGION THURSDAY AND FRIDAY, THEN SHIFT
INTO NEW ENGLAND AND THE CANADIAN MARITIMES DURING THE WEEKEND. A
LOW PRESSURE SYSTEM IS FORECAST TO DEVELOP OFF THE SOUTHEASTERN
UNITED STATES COAST DURING THE WEEKEND.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
A FRONTAL BOUNDARY REMAINS NEARLY STATIONARY RIGHT ALONG OUR
WEST/NORTHWESTERN ZONES THIS MORNING, AND SHOULD NOT MOVE MUCH
THROUGH THE DAY. NOT MUCH OF A SIGNIFICANT CHANGE TO THE FORECAST
THIS MORNING. SHOWERS CONTINUE ACROSS THE AREA FOR THE EARLY PART
OF THE DAY, WHICH SHOULD INCREASE IN COVERAGE, ESPECIALLY FOR OUR
WESTERN AREAS, AS A BATCH OF RAIN MOVES NORTHEASTWARD FROM
CENTRAL/WESTERN VIRGINIA. WE MADE SOME HOURLY GRID CHANGES BASED
ON CURRENT OBSERVATIONS, BUT OVERALL KEEPING IT STATUS QUO. BELOW
IS PREVIOUS DISCUSSION FOR OVERALL SITUATIONAL AWARENESS.
THE FORECAST FOR LATER TODAY AND ESPECIALLY TONIGHT IS THE
POTENTIAL FOR HEAVY RAIN. FOR NOW...WE WILL FORGO THE FLOOD WATCH
ROUTE...AS IT APPEARS AS THOUGH THE AXIS OF HEAVIEST RAIN COULD
FALL JUST TO THE WEST. MORE ON THE FLOOD THREAT IS CONTAINED IN
THE HYDROLOGY SECTION BELOW.
THE FIRST BATCH OF RAIN IS RIDING NORTH AHEAD OF A WEAK MID LEVEL
SHORT WAVE IN THE DEEPENING SOUTHWEST FLOW AT THAT LEVEL. AS THE
BATCH EXITS TO THE NORTHEAST...THE NEXT BATCH OF RAIN...MAINLY
DERIVED FROM ISENTROPIC LIFT...SHOULD AFFECT SOUTHERN AREAS LATER
THIS MORNING. IN BOTH CASES...THE QPF SHOULD BE FAIRLY LIGHT.
A LARGER AREA OF RAIN FORMING OVER SOUTHERN VIRGINIA AND NORTHEAST
NORTH CAROLINA SHOULD ARRIVE ACROSS WESTERN SECTIONS LATE THIS
MORNING OR EARLY THIS AFTERNOON. THIS ACTIVITY APPEARS TO HAVE A TIE
TO THE LOW LEVEL INFLOW OF MOIST THETA E RICH AIR FROM THE CENTRAL
AND EASTERN GULF OF MEXICO. HOWEVER...IT APPEARS AS THOUGH THE
HEAVIEST RAIN WILL HAVE TO WAIT FOR A SHORT WAVE IN THE DEEP MID
LEVEL SOUTHWEST FLOW...AND THAT MAY NOT ARRIVE UNTIL LATE THIS
AFTERNOON OR THIS EVENING.
JUST EAST OF THE FRONT...NEAR AND SHORT TERM MODELS ARE SHOWING
MARGINAL INSTABILITY...MAINLY CLOSE TO WHERE BREAKS IN THE CLOUDS
COULD OCCUR. WHILE THE POTENTIAL FOR THUNDER IS NOT HIGH (MARGINAL
SHEAR ARRIVING LATE AND POOR MID LEVEL LAPSE RATES)...A SLIGHT
CHANCE OF THUNDER WAS RETAINED IN THE FORECAST FOR THE ABOVE
REASONS.
NEAR AND SHORT TERM MODELS ARE SHOWING LOW LEVEL DRYING...NOW OVER
EASTERN NORTH CAROLINA (WHERE SKIES ARE CLEAR) WILL CROSS SOUTHERN
DELAWARE AND EASTERN JERSEY LATE THIS MORNING AND THIS AFTERNOON.
THE DRY AIR SHOULD KEEP THE RAIN AT BAY IN THESE AREAS...AND COULD
EVEN ALLOW THE ABOVE MENTIONED AREAS TO SEE PARTLY SUNNY SKIES
FOR A TIME.
ELSEWHERE...SKIES SHOULD REMAIN MOSTLY CLOUDY. FOR THE MOST PART...A
BLEND OF MOS TEMPERATURES WAS USED FOR HIGHS. HOWEVER...THERE IS A
CAVEAT. IF SKIES OVER SOUTHERN AND CENTRAL DELAWARE AND EASTERN NEW
JERSEY CLEAR FOR A TIME...HIGHS IN THESE AREAS COULD BE CLOSER TO
THE WARMER NAM MOS NUMBERS.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM TUESDAY/...
THE MAIN EVENT IS TONIGHT. AS MENTIONED EARLIER...THE HEAVIEST RAIN
APPEARS TO BE TIED TO THE PASSAGE OF A SHORT WAVE NEAR THE FRONT.
THE HIGHEST THETA E AIR RIDES NORTH JUST AHEAD OF THE SHORT WAVE AND
EAST OF THE FRONT. SHORT TERM MODELS (AS WELL AS THE HPC QPF) APPEAR
TO REFLECT THE ABOVE THINKING. AGAIN...THERE COULD BE SOME ELEVATED
CONVECTION AHEAD OF THE SHORT WAVE (AS INSTABILITY IN THE RISING AIR
IS RELEASED)...BUT IT DOES NOT APPEAR TO BE A SIGNIFICANT
CONTRIBUTOR TO THE HEAVY RAIN PROCESS.
RIGHT NOW...IT APPEARS AS THOUGH THE AXIS OF HEAVIEST QPF WILL GALL
WEST OF THE I-95 CORRIDOR (OR THE FALL LINE)...CLOSEST TO THE FRONT.
THIS IS WHERE THE HIGHEST RAIN CHANCES WERE PLACES. FURTHER
EAST...THE RAIN FORECAST BECOMES A BIT MORE NEBULOUS. WITH MOST OF
THE FORCING (AND THE LOW LEVEL FOCUS) TO THE WEST...PARTS OF
SOUTHERN DELAWARE AND EASTERN NEW JERSEY COULD HAVE A FAIRLY RAIN
FREE EVENING.
THE AXIS OF BEST LOW LEVEL THETA E SHOULD SHIFT TO THE EAST AFTER
0600 UTC...AND BE CENTERED ACROSS NORTHERN NEW JERSEY LATE TONIGHT
(IN THE RIGHT REAR QUADRANT OF AN EXITING 200 MB JET) THE SHORT TERM
MODEL QPF FORECAST FOLLOW THIS...AND THE BEST CHANCE OF HEAVY RAIN
LATE TONIGHT SHOULD SHIFT INTO NEW JERSEY. THIS IS WHEN EASTERN
SECTIONS HAVE THE BEST SHOT AT STEADIER RAIN.
FOR THE MOST PART...WITH LITTLE CHANGE IN AIRMASS OVERNIGHT...LOWS
WERE COMPRISED OF A BLEND OF MOS GUIDANCE AN PERSISTENCE.
&&
.LONG TERM /TUESDAY THROUGH SUNDAY/...
THIS TIME FRAME IS ANTICIPATED TO START ON THE UNSETTLED SIDE, THEN
IMPROVING CONDITIONS OCCUR FOR A TIME. THE OVERALL SYNOPTIC SETUP
INVOLVES AN UPPER-LEVEL TROUGH AMPLIFYING FROM THE GREAT LAKES AND
EASTERN CANADA INTO THE NORTHEAST TUESDAY AND WEDNESDAY. THIS WILL
EVENTUALLY KICK OUT A STALLED FRONT AS ANOTHER COLD FRONT EXITS THE
COAST DURING WEDNESDAY. THE TROUGH LOOKS TO WEAKEN SOME THURSDAY
THROUGH FRIDAY, THEN RIDGING ACROSS THE PLAINS SLIDES EASTWARD
SATURDAY AND SUNDAY AS SOME TROUGHING TAKES PLACE INTO THE NORTHERN
PLAINS. A PIECE OF ENERGY HOWEVER SLIDING ACROSS THE SOUTHERN STATES
BECOMES CUT OFF FROM THE MAIN FLOW, AND THIS LOOKS TO TURN INTO A
CLOSED LOW WITH TIME ALONG WITH A SURFACE LOW DEVELOPING OFF THE
SOUTHEASTERN U.S. COAST SATURDAY AND SUNDAY.
FOR TUESDAY, IT APPEARS THE LAST SHORT WAVE ROLLS UP THE STALLED
FRONT ALONG WITH A WEAK LOW REFLECTED AT THE SURFACE. AN AREA OF LOW
TO MID LEVEL CONVERGENCE VERY SLOWLY WORKS ITS WAY EASTWARD ALONG
WITH SOMEWHAT OF A THERMAL RIDGE. THE PW VALUES ARE FORECAST TO BE
AROUND 1.5 INCHES, AND AS AN UPPER-LEVEL TROUGH SHARPENS SOME THE
LOW-LEVEL JET WILL GRADUALLY BE SHIFTING TO OUR EAST WITH TIME. THIS
ALL LEADS TO PLENTY OF LIFT TO ALLOW FOR PERIODS OF RAIN TO MOVE
ACROSS THE REGION. THE MOST ORGANIZED LOOKS TO HOLD INLAND FOR AWHILE
AND TIED CLOSER TO THE LOW TO MID LEVEL CONVERGENCE AXIS. A DEEP
SOUTHERLY FLOW MAY TEND TO FOCUS THE RAIN IN SOUTH TO NORTH BANDS
/TRAINING/, WHICH MAY ENHANCE THE LOCAL RAINFALL FOR AWHILE
ESPECIALLY IF A CONVECTIVE CONTRIBUTION IS PRESENT. THEREFORE, WILL
CARRY A POSSIBLE HEAVY RAIN MENTION FOR MOST OF THE DAY ESPECIALLY
FROM ABOUT THE INTERSTATE 95 CORRIDOR ON WESTWARD. THE RAIN MAY END
UP BEING SPREAD OUT OVER A LONG ENOUGH TIME, THEREFORE NO FLOOD
WATCH WILL BE ISSUED ATTM. THE FORECAST SOUNDINGS REVEAL A RATHER
MOIST ATMOSPHERIC PROFILE. WHILE THERE IS INSTABILITY ALOFT THAT MAY
BECOME SURFACE BASED, THE SHAPE OF THE CAPE IS FORECAST TO BE MOSTLY
SKINNY. THIS MAY RESULT IN NOT ENOUGH ENERGY TO PROMOTE STRONG
ENOUGH UPDRAFTS, THEREFORE LIMITING THE CHARGE SEPARATION THAT CAN
BE ACHIEVED. IF THIS IS THE CASE, WE MAY BE ABLE TO REMOVE THE
THUNDER MENTION. FOR NOW THOUGH, WE INCLUDED A SLIGHT CHC OR
ISOLATED THUNDER FOR MOST OF THE AREA IN THE FORECAST DATABASE.
BASED ON THE SYSTEM MOVING EASTWARD GRADUALLY, THE RAIN SHOULD BE
ON A DOWNWARD TREND TUESDAY NIGHT ESPECIALLY AS THE BETTER FORCING
BEGINS TO SHIFT TO OUR NORTHEAST. THEREFORE WE LOWERED THE POPS
THROUGH THE NIGHT. THERE LOOKS TO BE AN ABUNDANCE OF MOISTURE
REMAINING THOUGH AND WITH LITTLE WIND AT THE SURFACE, LOW CLOUDS AND
SOME FOG MAY REMAIN THROUGH THE NIGHT. GIVEN SOME LOWER CONFIDENCE
IN HOW THIS MAY PLAY OUT, WE DID NOT INTRODUCE FOG ATTM.
FOR WEDNESDAY, THE LEFTOVER INITIAL BOUNDARY SHOULD BE EAST OF OUR
REGION HOWEVER A SECONDARY COLD FRONT WILL MOVE THROUGH LATER IN
THE DAY. THE DAY MAY START OUT WITH AREAS OF LOW CLOUDS AND FOG,
HOWEVER A LOW-LEVEL INVERSION SHOULD BREAK WITH ENOUGH BOUNDARY
LAYER HEATING. THE WINDS LOOK FAIRLY WEAK IN THE LOWER LEVELS,
THEREFORE REAL DEEP MIXING IS NOT ANTICIPATING BUT A FAIR AMOUNT OF
DRYING MAY OCCUR AS THE FLOW STARTS TO TURN WESTERLY. WHILE SOME
INSTABILITY IS FORECAST TO DEVELOP DURING THE DAY AND AHEAD OF THE
SECONDARY FRONT, THE AIRMASS MAY BE A BIT TO DRY ESPECIALLY IN THE
MID LEVELS TO GET MUCH IN THE WAY OF SHOWERS OR THUNDER GOING. IN
ADDITION, THE LOW-LEVEL FLOW MAY TURN WESTERLY WHICH WOULD TEND TO
LIMIT THE CONVERGENCE. FOR NOW, CARRIED LOW CHC POPS DUE TO THE
POTENTIAL FOR A FEW SHOWERS OR A THUNDERSTORM.
FOR THURSDAY AND FRIDAY, AN UPPER-LEVEL TROUGH GRADUALLY LIFTS OUT
OF THE NORTHEAST. A MID LEVEL RIDGE ACROSS THE PLAINS WILL SLIDE
EASTWARD, ALLOWING HIGH PRESSURE AT THE SURFACE TO BUILD INTO THE
NORTHEAST AND MID ATLANTIC. THIS WILL TEND TO BRING QUIET WEATHER TO
THE REGION ALONG WITH LIGHTER WINDS. THE MILD AFTERNOONS COMBINED
WITH LIGHT ENOUGH WINDS MAY ALLOW FOR A SEA BREEZE TO DEVELOP EACH
AFTERNOON, WITH PERHAPS MORE OF AN OVERALL ONSHORE FLOW STARTING TO
TAKE SHAPE AS WE GO THROUGH FRIDAY.
FOR SATURDAY AND SUNDAY, HIGH PRESSURE IS FORECAST TO BUILD INTO NEW
ENGLAND AND THE CANADIAN MARITIMES AS AN AREA OF LOW PRESSURE
DEVELOPS OFF THE SOUTHEASTERN U.S. COAST. THIS LOW LOOKS TO GET
CAPTURED BY A CLOSING OFF UPPER-LEVEL LOW THAT MAY TEND TO MEANDER
TO OUR SOUTH. THE COMBINATION OF HIGH PRESSURE TO THE NORTH AND LOW
PRESSURE TO OUR SOUTH WILL TEND TO INCREASE THE ONSHORE FLOW. THESE
TYPES OF SYSTEMS ARE TOUGH TO FORECAST GIVEN THE TENDENCY FOR A
GRADUAL DRIFT IN FORWARD MOTION. IF THE INCOMING UPPER-LEVEL RIDGE
AMPLIFIES ENOUGH, THE SLOW MOVING LOW TO OUR SOUTH MAY GET HELD AT
BAY OR EVEN SHUNTED OFF TO THE NORTHEAST INSTEAD OF MOVING TO THE
NORTH. EITHER WAY, WE MAY HAVE TO BE ON THE LOOKOUT FOR SOME SHOWERS
TRYING TO MOVE NORTHWARD LATE IN THE WEEKEND. THE ONSHORE FLOW WILL
EVENTUALLY INCREASE THE LOW-LEVEL MOISTURE AND PROBABLY SOME
CLOUDINESS PARTICULARLY FOR THE SECOND HALF OF THE WEEKEND. OUR
CONFIDENCE IS LOWER AS WE GO THROUGH THIS TIME FRAME.
&&
.AVIATION /14Z MONDAY THROUGH FRIDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.
MOSTLY VFR CONDITIONS ARE OCCURRING ACROSS THE TAF SITES, ALTHOUGH
WE CONTINUE TO HAVE SOME IN AND OUT MVFR CONDITIONS AS SHOWERS
MOVE OVER THE TAF SITES, ESPECIALLY WEST OF PHL. WE EXPECT
SHOWERS TO CONTINUE FOR MUCH OF THE DAY, ALTHOUGH COVERAGE MAY
INCREASE MORE TOWARD RDG/ABE DURING THE AFTERNOON AS AN AREA OF
RAIN MOVES NORTHEASTWARD FROM CENTRAL/WESTERN VIRGINIA. THESE
AREAS MAY BECOME PREVAILING MVFR DURING THE AFTERNOON.
ELSEWHERE... SHOWERS ARE EXPECTED TO BE MUCH LESS ORGANIZED. IN
FACT...SHORT TERM MODEL GUIDANCE SUGGESTS DRYING FOR AREAS EAST OF
KPHL.
THE DRY AIR EXITS THIS AFTERNOON...AND ALL TERMINALS SHOULD SEE
MVFR CONDITION FROM EARLY AFTERNOON INTO THE EVENING HOURS.
SOUTHERLY WINDS COULD APPROACH 10 KNOTS THIS AFTERNOON AT
KPHL...POSSIBLY AFFECTING OPERATIONS. FOR TONIGHT....AN AREA OF
RAIN WILL FOLLOW A STALLED FRONT WEST OF KPHL. THIS MEANS IFR
CONDITIONS FOR KRDG AND KABE...AND MAINLY MVFR CONDITIONS
ELSEWHERE.
OUTLOOK...
TUESDAY...MVFR WITH IFR AT TIMES FIRST WITH PERIODS OF RAIN AND
PERHAPS A THUNDERSTORM DURING THE DAY, THEN MAINLY DUE TO LOW CLOUDS
AT NIGHT. THE RAIN IS EXPECTED TO TAPER OFF TUESDAY NIGHT.
WEDNESDAY...MVFR TO LOCALLY IFR IN POSSIBLE MORNING LOW CLOUDS OR
FOG, THEN IMPROVING TO VFR. A FEW SHOWERS OR A THUNDERSTORM ARE
STILL POSSIBLE AS A SECONDARY COLD FRONT MOVES THROUGH LATER IN THE
DAY.
THURSDAY THROUGH FRIDAY...VFR. NORTH WINDS NEAR 10 KNOTS BECOMING
NORTHEAST OR EAST.
&&
.MARINE...
WINDS AND SEAS REMAIN BELOW SMALL CRAFT LIMITS THIS MORNING. THE
LOW LEVEL FLOW SHOULD REMAIN FROM THE SOUTH AND SOUTHWEST
TODAY...AS A LOW LEVEL JET PASSES OVERHEAD LATE THIS AFTERNOON AND
THIS EVENING. MODEL SOUNDINGS SHOW THAT LOW LEVEL STABILITY SHOULD
PRECLUDE MUCH MOMENTUM TRANSFER. THE BEST CHANCE FOR SIGNIFICANT
MOMENTUM TRANSFER LOOKS TO OCCUR BETWEEN 2000 UTC TO ABOUT 0200
UTC MONDAY. AT THIS POINT IT APPEARS AS THOUGH WINDS GUSTS WILL
STAY BELOW 25 KNOTS.
THE CONTINUING SOUTHERLY FETCH WILL...HOWEVER...RESULT IN BUILDING
SEAS THIS AFTERNOON AND THIS EVENING. WHILE THE WNAWAVE MODEL SEAS
HEIGHTS START A BIT HIGH THIS MORNING...BASED ON THE DEVELOPING
FETCH IT IS REASONABLE TO ASSUME THAT SEAS ON THE OCEAN WILL REACH 5
FEET BY LATE AFTERNOON. FOR THIS REASON...A SMALL CRAFT ADVISORY
WILL BE ISSUED FOR THE OCEAN WATERS FOR THIS AFTERNOON AND TONIGHT.
WINDS MAY TEND TO BACK OFF LATER TONIGHT AS THE LOW LEVEL JET
EXITS...AND THIS COULD ALLOW WIND GUSTS TO DROP BELOW 20
KNOTS...ESPECIALLY FOR THE SOUTHERN OCEAN WATERS. THE SOUTHERLY FLOW
SHOULD HAVE BEEN IN PLACE LONG ENOUGH FOR A NEARLY FULLY DEVELOPED
SEA ON THE OCEAN WATERS. FOR NOW...THE OUTPUT FROM THE WNAWAVE MODEL
WAS UNDERCUT A BIT (AS IT TENDS TO OVERDO SEAS ON A SOUTHERLY FLOW).
OUTLOOK...
THE SOUTHERLY FLOW AHEAD OF THE SLOW MOVING FRONTAL BOUNDARY AND
WEAK SURFACE LOW WILL CONTINUE TUESDAY. THIS IS EXPECTED TO CONTINUE
TO BUILD THE SEAS. A LOW-LEVEL JET IS FORECAST TO MOVE ACROSS THE
REGION DURING TUESDAY BEFORE WEAKENING AND SHIFTING TO OUR NORTHEAST
TUESDAY NIGHT INTO WEDNESDAY. THE WINDS AT 925 MB ARE FORECAST TO
INCREASE TO AROUND 30 KNOTS TUESDAY. THE FORECAST SOUNDINGS INDICATE
NEAR SURFACE STABILITY WHICH WOULD TEND TO LIMIT THE VERTICAL
MIXING. WHILE SOME WIND GUSTS COULD NEAR 25 KNOTS TUESDAY, IT
APPEARS ELEVATED SEAS WILL BE THE MAIN HAZARD. THEREFORE, THE SMALL
CRAFT ADVISORY FOR THE OCEAN ZONES WILL GO THROUGH THE DAY TUESDAY
FOR NOW. DESPITE THE WINDS ABOVE THE SURFACE WEAKENING TUESDAY NIGHT
AS THE LOW-LEVEL JET LEAVES THE AREA, ELEVATED SEAS SHOULD TEND TO
GRADUALLY LOWER HOWEVER THE ADVISORY MAY NEED TO BE EXTENDED. A
SECONDARY COLD FRONT THEN MOVES THROUGH LATE WEDNESDAY, HOWEVER THE
PRESSURE GRADIENT BEHIND IT IS NOT FORECAST TO BE ALL THAT STRONG,
THEREFORE THE SEAS SHOULD DROP BELOW ADVISORY CRITERIA DURING
WEDNESDAY AND CONTINUE THURSDAY AND FRIDAY. THE LOW-LEVEL FLOW
THOUGH MAY START TO BECOME ONSHORE LATER THURSDAY AND FRIDAY.
&&
.HYDROLOGY...
THE SURFACE FRONT THAT HAS STALLED ACROSS THE SOUTHERN POCONOS AND
LEHIGH VALLEY WILL ACT AS A CONDUIT FOR THE POTENTIAL FOR HEAVY RAIN
TONIGHT AND EARLY TUESDAY MORNING. AT THIS TIME...IT APPEARS AS
THOUGH THE AXIS OF HEAVIEST RAIN WILL POSITION ITSELF JUST WEST OF
THE AREA. FOR THAT REASON...WE WILL FORGO THE FLOOD WATCH THIS
MORNING.
THE SURFACE FRONT IS EXPECTED TO STALL OVER EVEN BE NUDGED BACK WEST
BY THE SURFACE HIGH OFF THE MID ATLANTIC COAST. THE POSITIONING OF
THE FRONT WILL BE ONE OF THE KEYS TO THE HEAVY RAIN FORECAST...AS IT
ACTS AS THE FOCUSING MECHANISM FOR THE MOIST THETA E LADEN AIR. A
WEAK SHORT WAVE RIDING OUT AHEAD OF THE THE LONG WAVE TROUGH CARVED
OUT OVER THE MISSISSIPPI VALLEY WILL FOCUS THE HEAVY RAIN LATE THIS
AFTERNOON INTO THIS EVENING...JUST TO THE SOUTHWEST OF THE AREA.
AT ABOUT THE SAME TIME...A LOW LEVEL JET WILL STREAK NORTHEAST JUST
TO THE EAST OF THE SURFACE FRONT. WHILE THERE COULD BE SOME ELEVATED
INSTABILITY ASSOCIATED WITH THE LOW LEVEL JET...IT DOES NOT SEEM AS
THOUGH DEEP CONVECTION WILL BE AN IMPORTANT COMPONENT TO THE HEAVY
RAIN THREAT. INSTEAD...WARM PROCESSES SHOULD DOMINATE THE
PRECIPITATION GENERATION...AS PRECIPITABLE WATER VALUES APPROACH
1.60 INCHES.
AS THE SHORT WAVE PASSES TONIGHT...THE CORE OF THE HEAVIEST RAIN
SHOULD BE JUST AHEAD OF IT. THE AREAS MOST LIKELY TO BE IMPACTED BY
THE HEAVY RAIN ARE THE LEHIGH VALLEY...SOUTHERN POCONOS AND POSSIBLY
NORTHWEST NEW JERSEY. THIS SLUG OF HEAVY RAIN PROBABLY EXITS TO THE
NORTHEAST TUESDAY MORNING.
AS THIS POINT...IT APPEARS AS THOUGH AS MUCH AS 2 INCHES OF RAIN
COULD FALL OVER PORTIONS OF THE LEHIGH VALLEY AND THE HIGHER TERRAIN
(IN ABOUT 12 HOURS). THIS NUMBER IS CONSIDERABLY BELOW THE FLASH
FLOOD AND HEADWATER GUIDANCE NUMBERS FOR THE 12 HOUR PERIOD ENDING
TUESDAY MORNING. WHILE SOME OF THE MEMBERS OF THE MMEFS GUIDANCE
SUGGEST THAT SOME OF OUR FORECAST POINTS COULD REACH CAUTION STAGE
WITH THE HEAVY RAIN...THE LATEST RIVER FORECASTS DO NOT.
SHOULD THE AXIS OF HEAVIEST RAIN FALL FURTHER TO THE EAST...THE
SMALLER RIVERS AND CREEKS OF NORTHERN DELAWARE AND SOUTHEAST
PENNSYLVANIA COULD BE AFFECT. RIGHT NOW...APPEARS AS THOUGH WE WOULD
NEED CLOSE TO 2.5 INCHES IN ABOUT 12 HOURS FOR THESE QUICK
RESPONDERS TO BECOME A PROBLEM. AS OF THIS MORNING...WE DO NOT
EXPECT THAT TO HAPPEN. FOR TUESDAY, PERIODS OF RAIN SOME OF WHICH
COULD BE HEAVY WILL BE SLIDING EASTWARD ACROSS THE REGION ALONG
WITH THE LOW-LEVEL JET. IT APPEARS THAT THE HEAVIER RAIN MAY BE
SPREAD OUT ENOUGH DESPITE PERHAPS SOME EMBEDDED CONVECTIVE
ELEMENTS. THEREFORE BASED ON ALL OF THE ABOVE, WE WILL HOLD OFF ON
THE FLOOD WATCH AND CONTINUE A MENTION IN THE HAZARDOUS WEATHER
OUTLOOK.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 4 PM THIS AFTERNOON TO 6 PM EDT
TUESDAY FOR ANZ450>455.
&&
$$
SYNOPSIS...GORSE
NEAR TERM...HAYES
SHORT TERM...HAYES
LONG TERM...GORSE
AVIATION...GORSE/HAYES
MARINE...GORSE/HAYES
HYDROLOGY...
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