Potential Historic Three Day New Years' Snowstorm Could Effect The Region This Weekend

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FXUS61 KCAR 302118
AFDCAR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CARIBOU ME
418 PM EST WED DEC 30 2009

.SYNOPSIS...
LOW PRESSURE OVER THE MARITIMES WILL CONTINUE MOVING NORTHEAST
TODAY...WHILE HIGH PRESSURE BUILDS TOWARD THE REGION. HIGH
PRESSURE WILL MOVE EAST OF THE REGION THURSDAY. LOW PRESSURE
WILL INTENSIFY SOUTHEAST OF THE REGION FRIDAY THROUGH
SATURDAY...THEN MOVE BACK TOWARD THE GULF OF MAINE SUNDAY.&&

.NEAR TERM /THROUGH THURSDAY/...
-- Changed Discussion --HIGH PRESSURE WILL SLOWLY SLIDE EASTWARD OVER MAINE THROUGH THE
NEAR TERM PERIOD WITH LITTLE MOISTURE AND SLACKENING WINDS. BY
LATE IN THE DAY THURSDAY MOISTURE WILL BEGIN TO SLIDE
NORTHEASTWARD AHEAD OF THE APPROACHING WEATHER SYSTEM FOR THE
WEEKEND. TEMPERATURES WILL BE VERY COLD WITH MOST INTERIOR AND
NORTHERN LOCATIONS EXPECTED TO DROP BELOW ZERO.-- End Changed Discussion --
&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
-- Changed Discussion --LOW PRESSURE IS EXPECTED TO DEVELOP OFF THE MID ATLANTIC COAST AT
THE BEGINNING OF THIS FORECAST PERIOD. THIS SYSTEM IS EXPECTED TO
MOVE NORTHEAST INTO THE GULF OF MAINE LATER IN THE DAY FRIDAY. AT
THE SAME TIME A STRENGTHENING UPPER LEVEL LOW WILL BE MOVING EAST
FRO M HE GREAT LAKES. MODELS DIFFER ON THE POSITION OF THE SURFACE
LOW AS THE UPPER SYSTEM PIVOTS TO THE SOUTH OF THE SURFACE SYSTEM
DURING THE DAY SATURDAY. THE SURFACE SYSTEM IS THEN CAPTURED BY
THE UPPER LOW SATURDAY NIGHT INTO THE DAY SUNDAY. A DEFORMATION
ZONE IS EXPECTED TO EXTEND FROM THE SURFACE LOW ACROSS CENTRAL AND
SOUTHERN PORTIONS OF THE FORECAST AREA SATURDAY RESULTING IN
FRONTAL BANDING. AS THE OCEAN LOW INTENSIFIES AND RETROGRADES TO
THE WEST SATURDAY NIGHT INTO SUNDAY MORNING...MARITIME AIR WILL
CIRCULATE AROUND THE NORTH SIDE OF THE LOW SETTING UP A ANOTHER
FRONTOGENIC BAND. PRIMARY DIFFICULTY WITH THIS SYSTEM IS
DETERMINATION OF LOCATION OF FRONTAL BANDS. HAVE SUFFICIENT
CONFIDENCE TO ISSUE WINTER STORM WATCH FOR SOUTHERN PORTION OF THE
FORECAST AREA ONLY AND FURTHER REFINEMENT WILL HAVE TO WAIT FOR
BETTER MODEL AGREEMENT. HAVE USED A BLEND OF THE NAM...GFS...GEM
AND ECMWF FOR QPF. SNOW AMOUNTS GENERATED USING A 10:1 RATIO FROM
QPF. WIND...TEMPERATURE AND DEW POINT GENERATED FROM GMOS.-- End Changed Discussion --
&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
-- Changed Discussion --THE WINTER STORM WATCH CONTINUES INTO THE NIGHT ON SATURDAY NIGHT
IN TO SUNDAY MORNING...WITH THAT IN PLACE WILL GO WITH HIGHER POPS
FOR SNOW ACROSS THE ENTIRE CWA. THE ONGOING WINTER STORM WILL
CONTINUE TO BRING SNOW AND HIGH WINDS ALL ACROSS THE CWA...WIND
GUSTS COULD BE UP TO 40 MPH INTO THE AREA MAINLY SATURDAY NIGHT
INTO SUNDAY MORNING. THERE ARE A FEW DIFFERENCES IN THE MODELS
THROUGH THE LONG TERM. THE GFS IS MORE AGGRESSIVE WITH KEEPING
MOISTURE IN PLACE WHILE THE ECMWF IS NOT AS AGGRESSIVE...WILL LEAN
MORE WITH GFS ATTM. THE LOW PRESSURE SYSTEM WILL BECOME ALMOST
STATIONARY OFF THE COAST AND WILL CONTINUE TO KEEP CLOUDS AND SNOW
IN THE FORECAST THROUGHOUT THE PERIOD AS THAT LOW IS SLOW TO MOVE
OUT...WILL KEEP A CHANCE OF SNOW SHOWERS THROUGH WEDNESDAY. USED
GMOS FOR TEMPS AND ADJUSTED AS NEEDED.-- End Changed Discussion --
&&

.AVIATION /21Z WEDNESDAY THROUGH MONDAY/...
-- Changed Discussion --VFR CONDITIONS ARE EXPECTED TO LAST THROUGH THURSDAY. SATURDAY
NIGHT THROUGH WEDNESDAY WITH SNOW IN THE FORECAST AND LOW CEILINGS
WILL ANTICIPATE AN EXTENDED PERIOD MVFR OR WORSE CONDITIONS.

LONG TERM: EXPECT MVFR/IFR CONDITIONS THURSDAY NIGHT. IFR
CONDITIONS ARE POSSIBLE FRIDAY THROUGH THE WEEKEND INTO MONDAY.-- End Changed Discussion --
&&

.MARINE...
-- Changed Discussion --HIGH PRESSURE WILL GIVE WAY TO AN APPROACHING STORM SYSTEM LATE
THURSDAY AND WAVES OF LOW PRESSURE WILL IMPACT THE SEAS THROUGH
THE WEEKEND. GUSTY WINDS WILL LINGER LONG ENOUGH THIS EVENING
LEADING TO A PERIOD OF SMALL CRAFT ADVISORY CONDITIONS.

SHORT TERM: HAVE USED A 50/50 BLEND OF THE NAM12 AND GFS40 TO
INITIALIZE WIND GRIDS. WILL INCREASE WINDS SPEED SEVERAL KNOTS
ABOVE MODEL BLEND IN NORTHEAST FLOW SATURDAY. FOR WAVES: WILL USE
WNA/4 TO INITIALIZE GRIDS. MODEL WIND SPEEDS ARE SUSPECTED TO BE A
LITTLE LOW OVER WEEKEND SO WILL INCREASE WAVE HEIGHTS 1 TO 2 FEET.-- End Changed Discussion --
&&

.CAR WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --ME...WINTER STORM WATCH FROM FRIDAY AFTERNOON THROUGH SUNDAY
MORNING FOR MEZ011-015>017-029>032.
MARINE...SMALL CRAFT ADVISORY UNTIL 4 AM EST THURSDAY FOR ANZ050>052.-- End Changed Discussion --

&&

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