National Weather Service Forecast Discussion for the Philadelphia Area
NWS Area Weather Forecast Discussion
County Warning Area [CWA]: PHI
Regional NWS Weather Office: Philadelphia, PA/Mt Holly, NJ
County Warning Area [CWA]: PHI
Regional NWS Weather Office: Philadelphia, PA/Mt Holly, NJ
000
FXUS61 KPHI 230555
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1255 AM EST THU FEB 23 2012
.SYNOPSIS...
AN AREA OF LOW PRESSURE OVER THE OHIO VALLEY WILL MOVE INTO NEW
ENGLAND THURSDAY MORNING AND SEND A COLD FRONT THROUGH OUR AREA.
ANOTHER LOW PRESSURE SYSTEM WILL FORM OVER THE PLAINS AND MOVE
NORTHEAST PASSING THROUGH NEW ENGLAND AROUND FRIDAY NIGHT. ITS
COLD FRONT SHOULD CLEAR THE NORTHEAST BY SATURDAY MORNING. A HIGH
PRESSURE SYSTEM WILL THEN BUILD SLOWLY EAST AND REACH THE MIDDLE
ATLANTIC STATES SUNDAY BEFORE MOVING OFFSHORE ON MONDAY. ANOTHER
COLD FRONT SHOULD MOVE THROUGH THE AREA ABOUT TUESDAY.
&&
.NEAR TERM /UNTIL 6 AM THIS MORNING/...
THE FORECAST WAS UPDATED TO INCLUDE AN ISOLATED MENTION OF THUNDER
FOR PORTIONS OF NORTHEAST MARYLAND AND SOUTHERNMOST DELAWARE. SOUNDINGS
IN THE AREA ARE DRY AND FOR THE MOST PART STABLE. IT WOULD APPEAR THAT
THE DISCRETE CELL(S) AHEAD OF THE AREA OF SHOWERS MOVING NORTHEAST
FROM VIRGINIA AND SOUTHERN MARYLAND IS TAKING ADVANTAGE OF THE LOW
INSTABILITY/HIGH SHEAR ENVIRONMENT. 0000 UTC SOUNDINGS SHOW THAT
THE MINUS 20 TEMPERATURE HEIGHT IS NEAR 16000 FEET...AND TOPS ARE
JUST GETTING TO THIS LEVEL...ALLOWING FOR CHARGE SEPARATION.
THE SAME APPEARS TO BE OCCURRING OVER WEST VIRGINIA...WHICH IS
CLOSER TO THE MID LEVEL SHORT WAVE DRIVING THE SHOWERS. IN THIS
AREA...SURFACED BASED INSTABILITY IS LIMITED...BUT SHEAR SEEMS TO
BE KEEPING THESE CELLS TOGETHER. FOR NOW...WILL NOT INCLUDE A
MENTION OF THUNDER ANY FURTHER NORTH THAN WAS MENTIONED IN THE
UPDATE.
OTHERWISE...THE SHOWERS SHOULD PASS OFF THE COAST BEFORE DAYBREAK
BASED ON THE LATEST MODEL GUIDANCE. NO SIGNIFICANT CHANGES WERE
MADE TO THE TEMPERATURE OR WIND FORECASTS FOR THE OVERNIGHT.
&&
.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM FRIDAY/...
THURSDAY...TRAILING AND LAST BIT OF SHOWERS ASSTD WITH THE CFP
DRY OUT EARLY IN THE DAY NORTH. DRY FORENOON-REST OF THE DAY WITH
GUSTY W WIND 20-30 MPH. A P-M/SUNNY DAY. FCST TEMPS MIGHT B A TAD
WARM BUT FIGURED ON WLY DOWNSLOPE ASSISTING.
WE MAY HAVE A FWX PBLM OF SORTS MIDDAY/AFTN AS RH`S DIP INTO THE
UPPER 20 PERCENT RANGE.
&&
.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
THE MDL GUIDANCE HAS COME INTO SOMEWHAT BETTER AGREEMENT WITH THE
22/12Z MDL CYCLE, BUT THERE ARE STILL SOME DIFFS THAT MAKE THIS A
CHALLENGING FCST WITH THE STORM BEGINNING TO IMPACT OUR AREA AT
THE START OF THE PD.
THE GFS DEVELOPS A STORM OVER THE MIDWEST AT 24/00Z AND THE WARM
FRONT IS CLOSE TO OUR REGION AT THAT TIME. IT MOVES THE LOW ENEWD
AND KEEPS MOST OF THE RAIN OVER NRN AREAS THU NIGHT AND FRIDAY AND
BRINGS THE CFP THRU FRI AFTN AND THEN RAPIDLY CLEARS THINGS OUT.
FRIDAY NIGHT INTO SATURDAY. IT ALSO THEN HAS A DOUBLE-BARRELLED
LOW STRUCTURE OVER NEW ENG/CAN MARITIMES. THE GFS IS ALONE IN BOTH
THE DOUBLE BARRELLED LOW STRUCTURE AND THE FASTER TIMING CLEARING
EVERYTHING OUT.
THE CMC ALSO DEVELOPS THE LOW IN THE MIDWEST AND IS SLOWER MOVG
IT THOUGH THE REGION AND HAS A MORE WIDESPREAD PRECIP SHIELD THAT
LINGERS INT FRIDAY EVENING WITH CFP OCCURRING FRI EVENING. THE
UKMET IS VERY SIMILAR TO THE CMC, THOUGH IT APPEARS TO BE SLOWER
WITH THE CFP FRI EVENING.
THE 22/12Z ECMWF HAS COME INTO BETTER, BUT NOT COMPLETE,
AGREEMENT THIS RUN. IT DEVELOPS THE LOW ON THU IN ABOUT THE SAME
PLACE. AND IS SIMILAR TO THE UKMET/CMC SOLN AT 24/18Z. WHILE IT IS
THE SLOWEST OF THE MDLS WITH THE CFP, IT ALSO LINGERS PRECIP THE
LONGEST FRI EVENING.
THE NAM/WRF HAS SOME PRECIP THU NIGHT AND THEN VIRTUALLY NOTHING
AND ITS SOLN SEEMS OUT OF PLACE AND IS BEING REJECTED.
SO ATTM, WE WILL BE TRENDING THE FCST TO A BLEND OF THE
CMC/UKMET/ECMWF WITH LESS PRECIP THAN THE ECMWF IS INDICATING
BEHIND THE CFP. CONFIDENCE HAS INCREASED IN THE DETAILS AS THE
MDLS ARE CONVERGING ON A SOLN, BUT THERE ARE STILL ENOUGH DIFFS IN
THE DETAILS. BEHIND THE CDFNT, PRECIP TYPE BECOMES AN ISSUE OVER
THE NRN AND WRN AREAS, AND IT WOULD BE EVEN MORE SO, WERE THE ECMWF
SOLN TO COME TO FRUITION. TEMPS WILL DROP BEHIND THE FRONT AND
WINDS WILL INCREASE. ANY PRECIP IN THESE AREAS WILL BE OF THE
WINTRY TYPE AND DEPENDING ON HOW MUCH MOISTURE IS LEFT THERE COULD
BE A FEW INCHES OF SNOW AND SOME ICE CAN NOT BE RULED OUT
DEPENDING ON HOW THE THERMAL PROFILES WORK OUT, AND THOSE DETAILS
WILL NEED TO BE RESOLVED AS THE TIME GETS CLOSER DUE TO THE TIMING
DIFFS AND AMT OF MOISTURE DIFFS INDICATED IN THE INDIVIDUAL MDL
SOLNS.
HIGH PRESSURE WILL BUILD IN BEHIND THE DEPARTING LOW/FRONT AND
THE PGRAD BEHIND THE STRONG LOW OVER THE CANADIAN MARITIMES AND
THE HIGH TO THE W WILL MAKE FOR A STRONG NW FLOW AND A WINDY DAY
ON SAT, BUT IT WILL GENLY BE DRY. HOWEVER, WITH STRONG NWLY FLOW
SOME RAIN OR SNOW SHOWERS CAN NOT BE RULED OUT IF THERE IS ENOUGH
INSTABILITY AROUND, BUT OVERALL AREAL COVERAGE AND POPS SHOULD BE
LOW.
THE HIGH WILL MOVE CLOSER TO THE REGION SATURDAY NIGH AND
OVERHEAD ON SUNDAY, SO THE WIND WILL DECREASE AND SATURDAY NIGHT
AND SUNDAY LOOK DRY.
THE HIGH MOVES OFF THE COAST ON MONDAY AND WHILE MONDAY STARTS
OUT DRY, CONSIDERABLE UNCERTAINTY RETURNS TO THE FCST AFTER THAT.
THE GFS BRINGS A QUICK MOVG LOW AND WK CDFNT BY MAINLY TO THE N,
WHICH COULD TRIGGER SOME PRECIP, WHILE THE ECMWF BRINGS A MORE
ROBUST LOW AND STRONGER FRONT THRU WITH MORE PRECIP AND THE CMC IS
COMPLETELY DRY. SO FOR NOW, WILL JUST CARRY VERY LOW POPS.
TUESDAY SEES HIGH PRESSURE MOVE BACK OVER THE REGION IN BOTH THE
GFS AND ECMWF. THEN ONCE AGAIN, WHILE BOTH MDLS HAVE A STORM
DEVELOPING AND IMPACTING THE REGION DURG THE MIDWEEK PERIOD, THE
CURRENT SOLUTIONS ARE HUNDREDS OF MILES APART AND ARE AS DIFFERENT
AS NIGHT AND DAY, SO FOR NOW, WILL NOT MAKE ANY SIGNIFICANT
CHANGES TO THESE PDS EXCEPT TO ADD SOME LOW POPS. IF MDL TRENDS
WITH FRIDAY`S SYSTEM ARE ANY INDICATION, IT MAY BE AWHILE UNTIL WE
KNOW HOW THE MIDWEEK SYSTEM WILL ULTIMATELY PLAY OUT.
TEMPS WILL START OUT MUCH ABOVE NRML, THEN FALL TO AROUND OR
SLIGHTLY BELOW NRML BEHIND THE CFP THEN REBOUND AGAIN TO ABOVE
NRML FOR EARLY NEXT WEEK.
&&
.AVIATION /06Z THURSDAY THROUGH MONDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.
A BATCH OF SHOWERS WILL CROSS SOUTHERN AREAS EARLY THIS MORNING. THE
AREA OF SHOWERS COULD BRING AN HOUR OR TWO OF MVFR CONDITIONS TO
KMIV AND KACY...BUT THE OTHER TERMINALS SHOULD MISS OUT ON THE MVFR
CONDITIONS...THOUGH SHOWERS COULD TOUCH KILG...KPHL AND PERHAPS
KPNE.
OTHERWISE...VFR CONDITIONS ARE EXPECTED TODAY. AFTER A WEAK FRONT
CROSSES THE AREA THIS MORNING...THE GRADIENT WIND WILL INCREASE AND
SUPPORT GUSTS BETWEEN 1500 UTC AND 2200 UTC AT JUST ABOUT ALL
TERMINALS. MODEL SOUNDINGS SUGGEST TOP GUSTS SHOULD COME IN BETWEEN
22 AND 25 KNOTS...WITH THE HIGHEST GUSTS AT KPHL AND KACY.
VFR CONDITIONS ARE EXPECTED FOR THE FIRST PART OF THE NIGHT...AS
CLOUDS INCREASE AHEAD OF A WARM FRONT. MVFR CONDITIONS ARE POSSIBLE
AFTER 0400 UTC FRIDAY...AND IFR CONDITIONS ARE POSSIBLE AFTER 0900
UTC...AND CEILINGS AND VISIBILITIES LOWER IN RAIN. A LOW LEVEL JET
COULD PRODUCE LOW LEVEL WIND SHEAR BETWEEN 0800 AND 1200 UTC FRIDAY.
A FEW THUNDERSTORMS ARE POSSIBLE SOUTH OF THE TERMINALS LATE TONIGHT
AND EARLY FRIDAY MORNING.
OUTLOOK...
A STRONG CDFNT WILL CROSS THE REGION MOST LIKELY FRIDAY EVENING.
EXPECT MAINLY MVFR/IFR DURG FRI THRU COLD FRONTAL PASSAGE. THERE
WILL LIKELY BE SOME PDS OF VFR, BUT CAN`T BE CONFIDENT ON WHERE
THEY WILL OCCUR AND HOW WIDESPREAD THEY WILL BE. GENERAL VFR
CONDITIONS ARE NOT EXPECTED TO RETURN UNTIL AFTER THE FRONT PASSES
AROUND FRIDAY EVENING. BEHIND THE FRONT, A STRONG NORTHWESTERLY
FLOW WILL DEVELOP AND FRIDAY NIGHT AND ESPECIALLY SATURDAY COULD
BE QUITE WINDY WITH GUSTS EXCEEDING 30 KTS. VFR CONDITIONS SHOULD
PREVAIL SATURDAY NIGHT AND SUNDAY WITH DECREASING WINDS.
&&
.MARINE...
BASED ON OBSERVATIONS FROM THE DELAWARE BAY...A SMALL CRAFT
ADVISORY HAS BEEN ISSUED FOR THE REST OF THE OVERNIGHT. NO DOUBT
SOME OF THE WIND GUSTS ARE CONVECTIVELY BASED...BUT THE GRADIENT
IS AT ABOUT ITS TIGHTEST. NO OTHER CHANGES TO THE REMAINDER OF THE
FORECAST.
ON THU...COULD SEE NEARSHORE GUSTS ARD 25 KTS.
MAY NEED TO ADD SCA TO UPPER DE BAY.
WINDS DIMINISH EVERYWHERE LATE IN THE DAY.
OUTLOOK...
SMALL CRAFT CONDITIONS ARE LOOK LIKELY IN THE SOUTHWEST FLOW IN
ADVANCE OF AN AREA OF LOW PRESSURE AND CDFNT WHICH WILL AFFECT THE
REGION BEGINNING THURSDAY NIGHT, WITH THE CDFNT CROSSING THE
COASTAL WATERS FRIDAY EVENING. AS THE AREA OF LOW PRESSURE DEEPENS
OVER THE CANADIAN MARITIMES AND HIGH PRESSURE BUILDS IN FROM THE
W, THE PRESSURE GRADIENT WILL TIGHTEN AND A STRONG NWLY FLOW WILL
DEVELOP FRIDAY NIGHT AND ESPECIALLY SATURDAY. GALE CONDS ARE PSBL
DURG THIS TIME. WINDS SHOULD DECREASE ON SATURDAY NIGHT BACK INTO
SMALL CRAFT ADVISORY CRITERIA AND BY SUNDAY INTO MONDAY WE MIGHT
NOT NEED ANY MARINE HEADLINES AT ALL.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 4 PM EST THIS AFTERNOON FOR
ANZ450>455.
SMALL CRAFT ADVISORY UNTIL 7 AM EST THIS MORNING FOR ANZ430-
431.
&&
$$
SYNOPSIS...NIERENBERG
NEAR TERM...IOVINO/HAYES
SHORT TERM...DRAG
LONG TERM...NIERENBERG
AVIATION...IOVINO/NIERENBERG
MARINE...HAYES/NIERENBERG| Forecast Discussion from: NOAA-NWS | Script developed by: El Dorado Weather |