460 
FXUS61 KPHI 231036
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
636 AM EDT SAT MAR 23 2013

.SYNOPSIS...
WEAK HIGH PRESSURE WILL APPROACH FROM THE WEST, REACH THE AREA ON 
SUNDAY AND THEN MOVE EAST. COMPLEX LOW PRESSURE WILL APPROACH FROM 
THE SOUTHWEST ON SUNDAY, CONSOLIDATE AS LOW PRESSURE OFF THE 
NORTHERN MID ATLANTIC COAST ON MONDAY AND THEN DEEPEN AND MOVE AWAY 
FROM THE COAST. HIGH PRESSURE TO OUR WEST WILL STRUGGLE TO BUILD IN 
THROUGH THE REMAINDER OF NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
OVERALL, A RELATIVELY QUIET DAY IS IN STORE AS HIGH PRESSURE TO OUR 
NORTHWEST CONTINUES TO INFLUENCE OUR REGION. A WEST-NORTHWEST FLOW 
WILL BE MAINTAINED THROUGH THE DAY WITH AMPLE SUNSHINE ACROSS THE 
REGION, ESPECIALLY EARLY IN THE DAY. MODEL SOUNDINGS INDICATE THAT 
CONVECTIVE TEMPERATURES WILL LIKELY BE REACHED ACROSS THE FORECAST 
AREA, INITIALLY FOR OUR NORTHERN LOCALES LATE MORNING TO MIDDAY AND 
THEN DURING THE EARLY AFTERNOON THROUGH THE REMAINDER OF THE REGION. 
WE THEREFORE STEP-UP SKY COVER A BIT THROUGH THE LATE MORNING TO 
AFTERNOON ACROSS THE CWA, BUT WE STILL EXPECT A FAIR AMOUNT OF SUN, 
WITH THE DEVELOPING STRATOCUMULUS TO BE MORE OF THE SCATTERED RATHER 
THAN BROKEN VARIETY. WE HAVE KEPT THE POSSIBILITY OF FLURRIES IN THE 
FORECAST FOR THE POCONOS AROUND MIDDAY WITH THE DEVELOPING 
STRATOCUMULUS AND BOTH THE GFS AND NAM SHOWING CHANNELIZED VORTICITY 
JUST TO OUR NORTH. DAYTIME TEMPERATURES ARE EXPECTED TO BE A BIT 
MILDER THAN RECENT DAYS, BUT WE WILL STILL BE RUNNING SEVERAL 
DEGREES BELOW AVERAGE HIGHS FOR LATE MARCH. WE GENERALLY TOOK A 
BLEND OF STAT GUIDANCE WITH CONTINUITY ACROSS THE REGION FOR MAX 
TEMPERATURES WITH SOME LOCAL ADJUSTMENTS. HIGH TEMPS ARE EXPECTED TO 
RANGE FROM THE MIDDLE TO UPPER 30S IN THE SOUTHERN POCONOS TO THE 
LOWER 50S IN OUR SOUTHERN DELMARVA ZONES.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SUNDAY/...
DRY AND FAIR CONDITIONS ARE EXPECTED TONIGHT AS HIGH PRESSURE WILL 
REMAIN TO OUR NORTHWEST. MODEL SOUNDINGS INDICATE CLEARING SKIES 
DURING THE EVENING HOURS, AND WINDS WILL BE LIGHT AND OUT OF A 
NORTHWEST DIRECTION. MINIMUM TEMPERATURES WERE A BLEND OF MET/MAV 
GUIDANCE, WITH LOWS RANGING FROM THE LOWER 20S ACROSS OUR NORTHWEST 
ZONES TO THE LOWER 30S IN DELAWARE AND THE EASTERN SHORE OF 
MARYLAND.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
OF THE TWO U.S. MODELS AND THE ECMWF, THE NAM IS THE MODEL THAT ONE 
WANTS TO VERIFY IF ONE WANTS THE BIG SNOW STORM THAT HAS ELUDED US 
THIS WINTER. HOWEVER, IT STANDS ALONE AS THE COLDEST AND THE WETTEST 
OF THE THREE. ALL HAVE NICE SUPPORT FROM AN UPPER JET, STRONG MID 
LEVEL Q-VECTOR CONVERGENCE, DECENT INTERSECTION OF H8 THETA E 
ADVECTION AND A PV ANOMALY ALOFT WHERE THE SECONDARY LOW GETS GOING, 
A DECENT TROWAL, A NICE MID LEVEL DRY SLOT TO THE SOUTHEAST, AND 
GOOD LOW TO MID LEVEL FRONTOGENESIS GOING, ALL OF WHICH ARE USHERED 
IN ON THE SKIRTS OF DECENT I295K LIFT. THE NAM IS FURTHER WEST THAN 
THE OTHER TWO (BUT STILL OFF THE COAST) AND ULTIMATELY DEEPER WITH 
THE DEVELOPING SECONDARY, AND THAT, IN PART, ALLOWS IT TO PUT OUR 
AREA UNDER EXCELLENT FORCING WITH A LOT OF MOISTURE WITHOUT 
SACRIFICING ITS COLD AIR. IF WE ACCEPTED THE NAM AND USED A SNOW TO 
LIQUID RATIO OF 7 TO 1 AT PHL, THEN WE WOULD FORECAST A FOOT OF SNOW 
THERE. CLIMATOLOGY AND THE FACT THAT THE NAM IS THE OUTLIER JUST 
WOULDN'T LET THIS FORECASTER DO THAT, BUT OF COURSE WE WILL WATCH 
THE MODELS' SOLUTIONS EVOLVE WITH INTEREST. WE'VE GONE WITH A 
GFS/ECMWF BLEND WITH THIS PASS AT THE EVENT. 

WE BASICALLY ARE FORECASTING ADVISORY LEVEL SNOWFALL NORTHWEST OF 
THE I-95 CORRIDOR (WHERE P-TYPE IS FORECAST TO STAY SNOW THROUGH THE 
EVENT) AND AND INCH OR LESS FROM THE I-95 CORRIDOR SOUTH (WHERE 
P-TYPE MAY START AS AND END AS SNOW). THIS PRESERVES CONTINUITY AND 
HAS A BASIS IN THE MODELS WE THINK ARE CLOSEST TO THE CORRECT 
SOLUTION. THE EVENT STARTS ON SUNDAY NIGHT AND ENDS ON MONDAY NIGHT. 
WINDS ON LAND WILL START TO PICK UP ON MONDAY AS THE SECONDARY LOW 
STRENGTHENS OFF THE COAST, BUT WE AREN'T EXPECTING LAND ADVISORY 
WINDS. REGARDING TEMPERATURES, WE HAVE GONE WITH A 
GUIDANCE/CONTINUITY BLEND ON SUNDAY, SUNDAY NIGHT AND MONDAY NIGHT, 
BUT HAVE GONE COLDER ON MONDAY AS WE WILL BE UNDER THE BRUNT OF THE 
COMPLEX SYSTEM BY THEN.

NO SIGNIFICANT CHANGES WERE MADE TO THE FORECAST BEYOND MONDAY 
NIGHT. FOR TUESDAY...LOW PRES IS FCST TO MOVE OUT TO SEA BUT THERE 
IS SOME LINGERING TROFINESS ALOFT AND WEAK UVV SO A SLIGHT CHC FOR 
RAIN OR SNOW SHOWERS IS MAINTAINED OVER THE FORECAST AREA.

FOR WEDNESDAY THROUGH FRIDAY...THERE IS LITTLE CHANGE IN THE
LARGE-SCALE PATTERN WITH NW FLOW AT THE SURFACE AND ALOFT
CONTINUING THROUGH THE PERIOD. LOW LEVEL COLD ADVECTION WITH THE
NW FLOW WILL FAVOR A FEW SNOW SHOWERS OR FLURRIES IN THE POCONOS.
TEMPERATURES SHOULD CONTINUE TO BE SOMEWHAT BELOW NORMAL AS WELL.

&&

.AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.

VFR CONDITIONS ARE FORECAST THROUGH THE TAF PERIOD. MAINLY CLEAR 
SKIES ARE EXPECTED FOR MUCH OF THE REGION THROUGH THE MID-MORNING 
HOURS; ALTHOUGH, VFR CEILINGS AROUND 4000 FEET WILL LIKELY BE IN 
PLACE FOR OUR NORTHWEST SITES OF KRDG AND KABE. THEREAFTER FROM LATE 
MORNING AND INTO THE AFTERNOON, SCATTERED STRATOCUMULUS WITH BASES 
MAINLY AROUND 5000 FEET WILL LIKELY DEVELOP FOR THE REMAINDER OF OUR 
SITES AS WE REACH CONVECTIVE TEMPERATURES. 

WITH RESPECT TO WINDS, A LIGHT WEST-NORTHWEST WIND UNDER 10 KNOTS 
WILL BE IN PLACE ACROSS THE REGION THROUGH ABOUT MID-MORNING. THE 
WEST-NORTHWEST WINDS WILL INCREASE LATE MORNING AND THROUGH THE 
AFTERNOON TO AROUND 10 TO 12 KNOTS WITH GUSTS AROUND 20 KNOTS. WINDS 
WILL THEN LIKELY DIMINISH AROUND SUNSET AND BE UNDER 10 KNOTS 
SATURDAY EVENING AND NIGHT, WITH VFR CONDITIONS CONTINUING.
 
OUTLOOK...
SUNDAY...MAINLY VFR. CONDITIONS EXPECTED TO LOWER SUNDAY NIGHT WITH 
POSSIBLE RAIN/SNOW. CONFIDENCE IS MODERATE. 

MONDAY...LIKELY IFR CONDITIONS WITH AREAS OF RAIN/SNOW. BRISK BUT 
SUB-ADVISORY NORTHEAST WINDS EXPECTED. CONFIDENCE IS MODERATE. 

TUESDAY...GENERALLY VFR CONDITIONS BUT POSSIBLY MVFR AT TIMES. 
CONFIDENCE IS MODERATE. 

WEDNESDAY...VFR CONDITIONS BUT NORTHWEST WINDS POSSIBLY GUSTING 20 
TO 25 KT. CONFIDENCE IS MODERATE.

&&

.MARINE...
HIGH PRESSURE EXTENDING OVER THE REGION TODAY AND TONIGHT WILL 
PROVIDE FOR FAIR WEATHER. WINDS WILL GENERALLY BE OUT OF A 
WEST-NORTHWEST DIRECTION THROUGH TONIGHT AND AVERAGING AROUND 10 TO 
15 KNOTS WITH GUSTS AROUND 20 KNOTS. SEAS ARE EXPECTED TO BE IN THE 
2 TO 3 FOOT RANGE. MOST OF THE AREA WATERS THEREFORE ARE FORECAST TO 
BE BELOW SCA CRITERIA. FOR OUR TWO NORTHERN MARINE ZONES FROM LITTLE 
EGG INLET NORTHWARD TO SANDY HOOK, MORE EFFICIENT MIXING AND A
TIGHTER PRESSURE GRADIENT ARE EXPECTED LATER TODAY. WE HAVE
THEREFORE DECIDED TO EXTEND THE SMALL CRAFT ADVISORY FOR ANZ450
AND 451 THROUGH 0Z AS NAM BUFKIT SOUNDINGS ARE SHOWING GUSTINESS
REACHING AROUND 25 KNOTS FOR LATE MORNING AND THIS AFTERNOON AT
BUOY 44065.

OUTLOOK...
FAIR WEATHER SATURDAY NIGHT INTO SUNDAY WILL GIVE WAY TO
DEVELOPING LOW PRESSURE OFF THE DELMARVA COAST ON MONDAY. THE
INTENSIFYING LOW WILL RESULT IN INCREASING NE WINDS AND ROUGH SEAS 
WITH POSSIBLE GALE CONDITIONS DEVELOPING, CENTERED ON MONDAY AND 
MONDAY NIGHT. ADVISORY CONDITIONS MAY BE THE RULE RATHER THAN THE 
EXCEPTION AFTER THAT AS SEAS WILL BE SLOW TO SUBSIDE AND A GUSTY NW 
WIND SHOULD DEVELOP.

&&

.FIRE WEATHER...
FORECAST TEN HOUR FUEL MOISTURE IS EXPECTED TO BE FALLING TODAY 
ACROSS THE REGION, WITH THE DRIEST CONDITIONS EXPECTED IN DELAWARE 
AND MARYLAND AND INTO PORTIONS OF NJ. TODAYS FORECAST RELATIVE 
HUMIDITIES ARE EXPECTED TO FALL INTO THE 30S THIS AFTERNOON, BUT 
SHOULD NOT DROP BELOW 30 PERCENT. WHILE A FEW WIND GUSTS AROUND 20 
MPH MAY OCCUR ACROSS THE REGION TODAY, SUSTAINED WINDS AND/OR 
FREQUENT GUSTS REACHING THIS LEVEL ARE NOT EXPECTED. TODAY LOOKS TO 
BE A MARGINAL DAY WITH REGARDS TO ENHANCED FIRE DANGER, AS WINDS AND 
RH VALUES SHOULD NOT REACH CRITERIA. FINE FUELS, THOUGH, WILL BE DRYING
ACROSS THE REGION.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR ANZ450-
     451.

&&

$$
SYNOPSIS...DELISI
NEAR TERM...KLINE
SHORT TERM...KLINE
LONG TERM...AMC/DELISI
AVIATION...AMC/DELISI/KLINE
MARINE...AMC/DELISI/KLINE
FIRE WEATHER...KLINE