Small Craft Advisory 77, NWS Gray, ME

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE GRAY ME
1153 PM EST SAT DEC 15 2012

.SYNOPSIS...
HIGH PRESSURE WILL BUILD SOUTHEAST ACROSS THE REGION THROUGH
TONIGHT BEFORE SLIDING OFFSHORE ON SUNDAY. IT WILL TURN MORE
WINTRY BY LATE SUNDAY AS LOW PRESSURE APPROACHES FROM THE UPPER
MIDWEST, THEN REDEVELOPS ALONG THE MID ATLANTIC COAST MONDAY. A
SECOND AND MORE SIGNIFICANT COASTAL SYSTEM FOLLOWS FOR THE MIDWEEK
PERIOD.

&&

.NEAR TERM /THROUGH SUNDAY/...
UPDATE...A FEW MINOR CHANGES TO ACCOUNT FOR CURRENT OBSERVATIONAL
TRENDS.

PREVIOUS DISCUSSION...

AT 19Z...A 1034 MILLIBAR HIGH WAS CENTERED OVER QUEBEC AND
EXTENDED SOUTHWARD INTO THE FORECAST AREA WITH DRY COLD AIR AND
CLEAR SKIES. THE HIGH WILL SLIDE OFFSHORE OVERNIGHT ALLOWING HIGH
AND MID CLOUD...AHEAD OF A 998 MILLIBAR LOW OVER IOWA...TO GRADUALLY
SPREAD EAST FROM THE GREAT LAKES INTO THE FORECAST AREA. WE'LL
SEE A QUICK DROP IN TEMPERATURES THIS EVENING AS SURFACE WINDS
DECOUPLE AND WITH DEW POINTS MAINLY IN THE SINGLE NUMBERS.

&&

.SHORT TERM /SUNDAY NIGHT/...
WARM AIR ADVECTION CLOUDS WILL THICKEN AND LOWER FROM SOUTHWEST-
TO-NORTHEAST DURING THE DAY WITH ANY MORNING SUNSHINE CONFINED TO
EASTERN AND NORTHERN MAINE ZONES. THE LOW LEVELS WILL BE DRY TO
START...AND IT WILL BE SOME TIME GIVEN THE LIGHT QPF FORECAST FOR
SNOW TO REACH THE GROUND. HAVE LIMITED LIKELY POPS FOR SNOW TO
SOUTHWESTERN NEW HAMPSHIRE AND THE CONNECTICUT VALLEY AREA WHERE
SOME LIGHT ACCUMULATIONS ARE POSSIBLE BY DARK. FOR THE REMAINDER
OF THE AREA...SNOW WILL NOT ARRIVE TO AFTER DARK...AND AFTER
MIDNIGHT OVER MAINE ZONES VICINITY OF THE KENNEBEC VALLEY. THE
FORECAST COLUMN IS SUFFICIENTLY COLD AND DRY ACROSS THE ENTIRE
AREA FOR PRECIPITATION TO BEGIN AS SNOW. WARMING ALOFT AFTER 06Z
MONDAY OVER SOUTHERN NEW HAMPSHIRE SHOULD RESULT IN SNOW MIXING
WITH SLEET THERE AND WILL LIMIT SNOW TOTALS. ALONG THE NEW
HAMPSHIRE SEACOAST...WARMING ALOFT AND AT THE SURFACE WILL ALSO
LIMIT SNOW TOTALS AS A MIX WITH SLEET AND RAIN OCCURS. STILL SOME
UNCERTAINTIES REGARDING FORECAST QPF AND MIXING OF PRECIPITATION
AND WE CONTINUE WITH THE CURRENT WATCH FROM LATE TOMORROW INTO
TUESDAY. TEMPERATURES WERE MANUALLY DERIVED STARTING WITH A
MET/MAV BLEND THAT LEANED TOWARDS THE COLDER NAM SOLUTION GIVEN
THE ANTICIPATED COLD AIR DAMMING.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
SOME SIGNIFICANT SNOWFALL IS SHAPING UP FOR MONDAY AND TUESDAY. CIPS
SNOWFALL ANALOGS OF MONDAY'S EVENT ARE VERY SIMILAR TO THE 15/00Z
GFS.

COLD AIR DAMMING WILL REMAIN SHARPLY ENTRENCHED OVER THE MOUNTAINS
AND FOOTHILLS OF NH AND MAINE MONDAY WHERE SNOW WILL CONTINUE IN AN
OVERUNNING REGIME. TOP-DOWN METHODOLOGY INDICATES A MIX OF SNOW AND
SLEET IS LIKELY FARTHER SOUTH OVER SOUTHERN NH AND SOUTHERN MAINE
BEFORE THE COASTAL FRONT ATTEMPTS TO PUSH ONSHORE AND CHANGE COASTAL
AREAS TO RAIN IN THE AFTERNOON. WE WILL SEE A LIGHTENING OF THE
PRECIPITATION IF NOT A BREAK IN PRECIPITATION LATE IN THE AFTERNOON
BEFORE THE NEXT WAVE APPROACHES.

WARM AIR ADVECTION WILL REINTENSIFY LATE MONDAY NIGHT INTO VERY
EARLY TUESDAY MORNING AS A WARM FRONT LIFTS NORTH. MODELS ARE
INDICATING THAT SURFACE HIGH PRESSURE TO OUR NE AND RELATED COLD AIR
DAMMING WILL HAVE WEAKENED SOMEWHAT BY THIS TIME. WARMING UPPER
LEVELS WILL HAVE TO CONTEND WITH THE LEFT EXIT REGION OF AN UPPER
LEVEL JET STREAK WHICH WILL HELP INCREASE LIFT AND ENHANCE SNOWFALL.
SREF PROBABILITIES AND TEMPERATURE PROFILES INDICATE THAT RAIN
BECOMES MORE LIKELY OVER THE COASTAL PLAIN AS TUESDAY WEARS ON WITH
SNOW EVENTUALLY CONFINED TO THE HIGHER TERRAIN BY THE AFTERNOON.
NEVERTHELESS MOST AREAS WILL SEE A FEW INCHES OF SNOW OUT OF THIS
SYSTEM CREATING SLICK DRIVING CONDITIONS.

TEMPERATURES FOR MONDAY AND TUESDAY WERE DERIVED USING A BLEND OF
THE THE LOCAL WRF AND NAM12 WHICH SHOULD HANDLE THE COLD AIR DAMMING
BETTER THAN REGIONAL MODELS. ALSO A NON-DIURNAL TREND WAS FOLLOWED.

PRECIPITATION ENDS WEDNESDAY WITH HIGH PRESSURE OVER US ON THURSDAY.
A VERTICALLY STACKED LOW PRESSURE SYSTEM IS EXPECTED TO MOVE JUST
NORTH OF THE REGION FRIDAY. THIS LOW WOULD BRING RAIN TO MOST OF THE
AREA EXCEPT OVERNIGHT WHEN A FEW SNOW SHOWERS MAY DEVELOP OVER THE
COASTAL PLAIN.

&&

.AVIATION /06Z SUNDAY THROUGH THURSDAY/...
SHORT TERM /THROUGH 11Z MON/...MAINLY VFR THROUGH SUN...EXCEPT FOR
CONN VALLEY AND SW NH WHERE MVFR IN SNOW AND LCL IFR CONDITIONS
ARE LIKELY AFT 21Z SUN. IFR CONDITIONS IN SNOW WILL SPREAD
GRADUALLY NE SUN NIGHT ARRIVING AT KAUG AND KRKD AFT 06Z MON.

LONG TERM...IFR OR LOWER CONDITIONS LIKELY IN SNOW AND FOG MONDAY
THROUGH WEDNESDAY. WINDS MAY GUST ALONG COAST TO NEAR 25 KT.

&&

.MARINE...
SHORT TERM /THROUGH SUNDAY NIGHT/...QUIET UNTIL SUNDAY NIGHT WHEN
WINDS AND SEAS SHOULD GRADUALLY INCREASE TO SMALL CRAFT VALUES
AFTER MIDNIGHT.

LONG TERM...SMALL CRAFT ADVISORY WILL BE NEEDED ON MONDAY BEFORE
GALES DEVELOP ON TUESDAY.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...WINTER STORM WATCH FROM SUNDAY AFTERNOON THROUGH TUESDAY
     MORNING FOR MEZ007>009-012>014-019>021.
NH...WINTER STORM WATCH FROM SUNDAY AFTERNOON THROUGH TUESDAY
     MORNING FOR NHZ001>006-009.
MARINE...NONE.

&&

NEAR TERM...LEGRO