FXUS61 KPHI 112032 CCA
AFDPHI
AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
328 PM EST FRI DEC 11 2009
.SYNOPSIS...
HIGH PRESSURE WILL CONTINUE TO MOVE INTO THE AREA FROM THE SOUTHWEST
TONIGHT, AND TAKE FULL CONTROL OF THE WEATHER ON SATURDAY. THE HIGH
WILL MOVE OFFSHORE SATURDAY NIGHT. A COASTAL LOW AND FRONTAL
BOUNDARY ARE EXPECTED TO AFFECT THE AREA SUNDAY INTO SUNDAY
NIGHT. HIGH PRESSURE WILL BRIEFLY MOVE INTO THE AREA MONDAY,
BEFORE A FRONTAL BOUNDARY MOVES THROUGH THE AREA TUESDAY. HIGH
PRESSURE IS EXPECTED TO REMAIN TO OUR WEST THROUGH THE MIDDLE OF
NEXT WEEK, PRODUCING A STRONG NORTHWEST FLOW ACROSS THE AREA.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
STRONG GUSTY WINDS AHEAD OF AN APPROACHING HIGH PRESSURE SYSTEM WILL
BEGIN TO SLOWLY DIMINISH AS WE GO THROUGH THE EVENING HOURS, BUT
WILL REMAIN GUSTY AROUND 25 TO 30 MPH LATE THIS AFTERNOON AND EARLY
EVENING. AFTER THE SUN SETS, IT MAY TAKE A FEW HOURS FOR THE WINDS
TO COMPLETELY DIE DOWN, BUT AS WE GET PAST MIDNIGHT, THE STRONG
GUSTS SHOULD HAVE DIMINISHED. THERE ARE SOME SCATTERED CLOUDS LATE
THIS AFTERNOON, BUT AFTER THE WINDS DIE DOWN OVERNIGHT, WE EXPECT
MOSTLY CLEAR SKIES, SO TEMPERATURES SHOULD BE ABLE TO DROP INTO THE
LOW TO MID 20S, WITH A FEW ISOLATED TEENS.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY/...
HIGH PRESSURE WILL MOVE JUST TO OUR SOUTH ON SATURDAY, BUT WILL
HAVE FULL CONTROL OF THE WEATHER. MOSTLY SUNNY SKIES AND DRY
WEATHER IS IN THE FORECAST FOR SATURDAY WHICH WILL ALLOW FOR
TEMPERATURES TO WARM INTO THE UPPER 30S TO LOWER 40S FOR MUCH OF
THE AREA, AND THE LOWER 30S FOR THE FAR NORTHERN PORTIONS OF THE
AREA. WITH THE HIGH PRESSURE MOVING INTO THE AREA, WINDS SHOULD BE
QUITE A BIT LOWER THAN THEY HAVE BEEN THE LAST SEVERAL DAYS. THERE
MAY STILL BE SOME GUSTS, BUT SHOULD NOT BE MORE THAN AROUND 20
MPH. THE HIGH PRESSURE WILL BE MOVING OFFSHORE ON SATURDAY NIGHT,
AS AN AREA OF LOW PRESSURE DEVELOPS ALONG THE SOUTHEAST COAST.
THIS LOW WILL RIDE ALONG THE EASTERN SEABOARD ON SUNDAY,
EVENTUALLY BRINGING OUR AREA ANOTHER SHOT OF PRECIPITATION.
TEMPERATURES ON SUNDAY SHOULD BE WARM ENOUGH TO KEEP THE
PRECIPITATION ALL RAIN DURING THE DAY, AND INTO THE EVENING
BEFORE IT ENDS. HOWEVER, IF THE PRECIPITATION MOVES IN QUICK
ENOUGH, WE MAY HAVE A VERY BRIEF PERIOD OF A WINTRY MIX. THIS
SHOULD HOPEFULLY BECOME MORE CERTAIN AS THE NEXT SEVERAL FORECASTS
PROGRESS. THIS SYSTEM WILL BE QUICK AND MOVE OUT OF THE AREA
SUNDAY NIGHT, ALLOWING HIGH PRESSURE TO BRIEFLY BUILD INTO THE
AREA ON MONDAY. THIS HIGH PRESSURE SHOULD KEEP THE WEATHER DRY AND
ALLOW TEMPERATURES TO WARM INTO THE MID TO UPPER 40S, WITH A FEW
50S AS WELL.
&&
.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
ANOTHER ARCTIC BLAST IS ON TAP FOR OUR CWA DURING THE LONG TERM. BUT
AT THE START OF THE LONG TERM, A RELATIVELY MILD NIGHT IS EXPECTED
MONDAY NIGHT. AS THE COLD FRONT APPROACHES, CHANCES FOR SHOWERS WILL
START INCREASING. THE LATEST ECMWF HAS SLOWED THE CDFNTL PASSAGE
CLOSER TO THE GFS'S TIMING. SO POPS FOR MONDAY NIGHT HAVE BEEN
LIMITED TO AFTER MIDNIGHT. THE AIR MASS ALOFT IS RELATIVELY MILD AND
PTYPE IS MAINLY RAIN. HIGHER TERRAIN LOCATIONS THE PTYPE ISSUE MIGHT
IN REALITY BE MORE FREEZING RAIN VS RAIN THAN RAIN VS SNOW. THIRD
DAY IN A ROW THAT THE SOUTHERN STREAM CONTRIBUTION TO THIS SYSTEM
REMAINS ON THE WEAK SIDE MAKING TUESDAY DAY ALMOST A TYPICAL COLD
FRONTAL TYPE OF DAY. THE ONLY MODEL THAT IS SHOWING A SHORT
ANAFRONT PRECIP SHOT IS THE CAN GGEM. BUT THAT MODEL AS OF TODAY
WOULD STILL HAVE PCPN CUT OFF BEFORE A WIDESPREAD CHANGE TO FROZEN
PRECIPITATION.
ON WEDNESDAY THROUGH FRIDAY OUR CWA WILL BE DOMINATED BY AN ARCTIC
HIGH PRESSURE SYSTEM THAT WILL WORK ITS WAY TO THE EASTERN SEABOARD.
THE LAKE EFFECT MACHINE SHOULD BE WORKING VERY WELL INTO THURSDAY
DAY AT THE LEAST. CHANCES ARE SOME LAKE EFFECT STREAMERS OR
RESIDUALS SHOULD MAKE IT INTO OUR CWA. FOR NOW WE LIMITED THE
MENTION OF FLURRIES (WHICH MIGHT BE SNOW SHOWERS) TO OUR HIGHER
TERRAIN.
ON FRIDAY, THE GFS IS FORECASTING AN ALBERTA TYPE LOW TO MAKE IT
INTO THE GREAT LAKES. THE LATEST ECMWF DOES NOT. THIS HAS TO
DO WITH HOW EACH MODEL IS HANDLING A POLAR VORTEX MOVING INTO THE
CANADIAN MARITIMES. BOTH RETROGRADE IT, BUT THE GFS IS FARTHER SOUTH
THAN THE ECMWF WITH ITS RETROGRESSION AND THUS PASSES THE LOW INTO
OUR CWA. THE ECMWF AND ALL OF THE OTHER MEDIUM RANGE MODELS ARE NOT
AS FAR SOUTH. FOR NOW WE KEPT FRIDAY DRY.
THE GFS REMAINS AT THE FOREFRONT OF THE COLDEST TEMPS DURING THIS
PERIOD WHICH STILL REMAINS LOGICAL GIVEN THIS HIGH PRESSURE IS
ARRIVING FROM THE NORTH POLE, WE LEANED CLOSER TO ITS THERMAL FIELDS
THAN THE ECMWF.
BEYOND OUR DETERMINISTIC FORECAST, THE NEGATIVE NAO PATTERN WHICH
NORMALLY MEANS COLDER WEATHER, IS EXPECTED TO PERSIST. THE CANADIAN
MARITIMES POLAR VORTEX IS ON THE SOUTH SIDE OF A FORECAST REX BLOCK
WITH A CLOSED RIDGE FORECAST TO BE OVER GREENLAND. BOTH ENMASS ARE
EXPECTED TO RETROGRADE WESTWARD AND WEAKEN SOMEWHAT. ON THE PACIFIC
SIDE THE STRONG (BASED ON CURRENT WEEKLY CPC VALUES) EL NINO KEEPS
ON TRYING TO SMASH THE PACIFIC RIDGE, THIS HAS CAUSED VERY LITTLE
RUN TO RUN CONTINUITY WITH ACTUAL GFS OR ECMWF MODEL RUNS. EITHER
WAY BLOCKING PATTERNS TAKE TIME TO UNRAVEL, SO OUR WEATHER SHOULD
REMAIN ON THE COLDER THAN NORMAL SIDE AS WE REACH ASTRONOMICAL
WINTER.
&&
.AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...
WITH HIGH PRESSURE PUSHING IN FROM THE TENNESSEE RIVER VALLEY, VFR
CONDITIONS ARE EXPECTED INTO SATURDAY NIGHT. STRONG WEST TO
NORTHWEST WINDS ARE THE ONLY CONCERN RIGHT NOW, GUSTING OVER 30 KT
FROM TIME TO TIME ACROSS MANY OF THE TAF SITES. MODEL GUIDANCE
SUGGESTS THESE WINDS WILL DIMINISH DURING THE EVENING HOURS TONIGHT,
BUT WE THINK THAT IS OPTIMISTIC. WE KEPT GUSTS AROUND 25KT THIS
EVENING, THEN DROPPED THEM DOWN TO AROUND 20KT DURING THE LATE
OVERNIGHT HOURS BEFORE ENDING THE GUSTS ALTOGETHER BY SATURDAY
MORNING. SATURDAY LOOKS LIKE A VERY NICE DAY, WITH WEST WINDS IN
THE 10KT TO 20KT RANGE AND MAINLY CLEAR SKIES.
OUTLOOK...
THE HIGH WILL BEGIN TO PUSH OFF TO THE EAST SATURDAY NIGHT. LOW
PRESSURE ALONG THE MID ATLANTIC COAST COULD BRING LOWERING
CIGS/VSBYS SUNDAY INTO SUNDAY NIGHT. HIGH PRESSURE WILL RETURN
MONDAY AND MONDAY NIGHT BEFORE A COLD FRONT APPROACHES FROM THE WEST
ON TUESDAY
&&
.MARINE...
WIND GUSTS IN THE RANGE OF 35 TO 40 KT CONTINUE THIS AFTERNOON BOTH
ON THE OCEAN FRONT AND DELAWARE BAY. FOR EXAMPLE, AT 2PM, GUSTS NEAR
40 KT WERE BEING REPORTED BY THE CAPE HENLOPEN TOWER, AND THE
BRANDYWINE SHOAL LIGHT WAS REPORTING GUSTS AT 35 KT. THE PRESSURE
GRADIENT IS FORECAST TO BE STRONGEST NOW INTO THE EARLY EVENING
HOURS, THEN GRADUALLY RELAX FROM SOUTH TO NORTH AS THE NIGHT WEARS
ON. WITH THIS IN MIND, WILL KEEP GALE WARNINGS UP ON THE DELAWARE
BAY AND OCEAN SOUTH OF GREAT EGG INLET UNTIL 7 PM. FOR THE REST OF
THE OCEAN WATERS NORTH OF GREAT EGG INLET, WILL CONTINUE THE GALE
WARNING THROUGH 9Z FOR RIGHT NOW, BUT THIS MAY BE A LITTLE LONGER
THAN NECESSARY.
AS A HIGH PRESSURE SYSTEM MOVES IN SATURDAY AND SATURDAY NIGHT,
RATHER TRANQUIL CONDITIONS WILL PREVAIL. WINDS AND SEAS COULD
APPROACH OR REACH ADVISORY CONDITIONS ONCE AGAIN LATE SUNDAY AND
SUNDAY NIGHT AS LOW PRESSURE MOVES ALONG THE MID ATLANTIC COAST,
THEN OUT TO SEA.
&&
.TIDES...
TIDAL DEPARTURES ON THE OCEAN WERE IN THE VICINITY OF MINUS 1.5 TO
MINUS 2.0 FEET EARLY THIS AFTERNOON. COMPUTER GUIDANCE SUGGESTS
THESE DEPARTURES WILL INCREASE A LITTLE MORE INTO THIS EVENING
BEFORE LEVELING OFF LATE THIS EVENING, THEN BEGIN A SLOW DECLINE
IN THE LATE OVERNIGHT HOURS. THIS MEANS THE NEXT LOW TIDE, WHICH
OCCURS BETWEEN 9 PM AND 11 PM, WILL BE OF MOST CONCERN FOR
BLOWOUT TIDES ON THE OCEAN FRONT. BY THE TIME THE NEXT LOW TIDE
OCCURS IN THE 9 AM TO 11 AM TIME FRAME SATURDAY MORNING, THE
DEPARTURES SHOULD BE JUST LOW ENOUGH NOT TO PRODUCE BLOWOUT
CONDITIONS. LATER SHIFTS WILL KEEP AN EYE ON THIS AND ISSUE UPDATES
AS NEEDED.
THE DELAWARE BAY AND TIDAL PORTIONS OF THE DELAWARE RIVER ARE
SLIGHTLY DIFFERENT IN THAT THE DEPARTURES MAY ACTUALLY INCREASE
THROUGH THE OVERNIGHT HOURS AND REACH THEIR PEAK DURING THE LOW TIDE
CYCLE EARLY SATURDAY MORNING AND CONTINUE AT RELATIVELY HIGH LEVELS
INTO SATURDAY AFTERNOON. THE LOW WATER ADVISORY WILL THEREFORE BE
EXTENDED UNTIL 6 PM SATURDAY IN THE DELAWARE BAY AND DELAWARE RIVER.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...LOW WATER ADVISORY UNTIL 3 AM EST SATURDAY FOR ANZ430-431-
450>455.
GALE WARNING UNTIL 4 AM EST SATURDAY FOR ANZ450>452.
GALE WARNING UNTIL 7 PM EST THIS EVENING FOR ANZ430-431-
453>455.
&&
$$
SYNOPSIS...ROBERTSON
NEAR TERM...ROBERTSON
SHORT TERM...ROBERTSON
LONG TERM...GIGI
AVIATION...MIKETTA
MARINE...MIKETTA
TIDES...MIKETTA
