FXUS61 KBOX 230836
AFDBOX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
336 AM EST WED DEC 23 2009
.SYNOPSIS...
DRY AND COLD WEATHER WILL GRADUALLY MODERATE THURSDAY AND FRIDAY
ALONG WITH DIMINISHING WINDS...AS HIGH PRESSURE CRESTS OVER NEW
ENGLAND. LOW PRESSURE WILL APPROACH FROM THE SOUTHWEST
SATURDAY...WHICH WILL BRING A PERIOD OF WINTRY WEATHER INLAND AND
MAINLY RAIN AND WIND ALONG THE COAST. THE LOW AND ITS PRECIPITATION
MAY DEPART THE REGION LATER SUNDAY...FOLLOWED BY COLDER AND BLUSTERY
WEATHER EARLY NEXT WEEK.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
CLOSED UPPER LOW ALONG THE CANADIAN BORDER THIS MORNING SHIFTS
SOUTHEAST BY EVENING. CLOUDS ASSOCIATED WITH THE LOW EXTEND FROM
MAINE TO NORTHERN NEW YORK WITH LIGHT SNOW ALONG THE BORDER. AS THE
LOW TRANSLATES SOUTHEAST THESE CLOUDS SHOULD ALSO SHIFT OUR WAY.
EXTRAPOLATION OF EARLY MORNING MOVEMENT WOULD BRING THE CLOUD SHIELD
INTO SOUTHERN NH AROUND 11Z...TO THE MASS PIKE AROUND 14Z...AND TO
THE SOUTH COAST BY 18Z.
COLD POOL MOVES ACROSS ESPECIALLY THIS AFTERNOON. TIME SECTIONS SHOW
MOIST LAYER 925 MB TO 850 MB BUT WITH DRIER AIR AT SURFACE. 850-500
MB LAPSE RATES ARE AROUND 16-20C...NOT TOO IMPRESSIVE. MODEL VERTICAL
MOTION SHOWS LITTLE IN THE WAY OF LIFT. COULD BE SOME FLURRIES
ESPECIALLY OVER NH AND EASTERN MASS...BUT MOSTLY THIS LOOKS LIKE
CLOUDS AND DRY WEATHER.
EQUIVALENT 850 TEMPS FROM THE MIXED LAYER ARE IN THE -15C TO -20C
RANGE...WHICH WOULD SUPPORT MAX TEMPS MOSTLY IN THE 20S. WE USED A
BLEND OF NAM AND GFS MOS VALUES.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY/...
THE UPPER LOW MOVES EAST OUT TO SEA TONIGHT WHILE A GREAT LAKES UPPER
RIDGE BUILDS EAST. EXPECT CLEARING SKIES IN THE CT VALLEY AND OTHER
WESTERN SECTIONS. THERE MAY BE A CLEARING TREND LATER IN THE NIGHT
IN THE EAST...BUT WITH SURFACE WINDS SHIFTING FROM NORTHWEST TO
NORTHEAST BY MORNING THIS MAY RETARD THE DEPARTURE OF CLOUD COVER.
RIDGE BUILDS IN SURFACE AND ALOFT FOR THURSDAY AND FOR CHRISTMAS DAY
WITH THE SURFACE RIDGE PASSING NORTH OF NEW ENGLAND. THIS WILL BRING
OUR WINDS AROUND TO NORTHEAST OFF THE GULF OF MAINE. SO EVEN THOUGH
THE COLDEST AIR MOVES OFF WITH THE DEPARTING LOW...A COOL SURFACE
LAYER OF AIR SHOULD REMAIN. THIS AND THE EXISTING SNOWPACK WILL BE A
RESISTING INFLUENCE ON ANY LATE WEEK WARMING TREND. SKY COVER
FORECAST GRIDS LINGER IN THE 25-50 PERCENT RANGE ESPECIALLY FRIDAY IN
ANTICIPATION OF INCREASING CIRRUS. TEMPERATURES ARE AGAIN A BLEND OF
MOS.
&&
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
MAIN FORECAST CONCERN REVOLVES AROUND THE TIMING OF PRECIP AND
PRECIP TYPE ASSOCIATED WITH OUR NEXT LOW PRESSURE SYSTEM OVER THE
WEEKEND.
BIG CUTOFF LOW MEANDERS FROM THE UPPER MIDWEST INTO THE LAKES OVER
THE WEEKEND. THIS WILL AID IN PUSHING SFC LOW PRESSURE CLOSER TO
SNE...AS WELL AID IN THE DEVELOPMENT OF A DECENT SELY INFLOW JET. THE
VARIOUS GLOBAL MODELS AGREE IN THE GENERALITIES...BUT DETAILS WITH
SPECIFICS /ESPECIALLY TIMING/ STILL NEED TO BE IRONED OUT. THE GFS IS
PRETTY FAST WITH THE PRECIP SHIELD...BASICALLY BRINGING IT THROUGH
ALL OF SNE BY LATE SATURDAY NIGHT OR EARLY SUNDAY MORNING. THE 12Z
ECMWF IS CONSIDERABLE SLOWER...WITH THE MAIN EVENT OCCURRING DURING
THE DAY SUNDAY. WILL TAKE A COMPROMISE AS FAR AS TIMING OF POPS
GO...BUT TEND TO PREFER THE SLOWER END OF THE GUIDANCE ENVELOPE AS
THE UPPER AIR PATTERN LOOKS TO BE QUITE AMPLIFIED.
AS FAR AS PRECIP TYPE GOES...THIS IS PROBABLY GOING TO BE A MIXED
PRECIP EVENT FOR MUCH OF THE INTERIOR AS COLD SFC AIR PROBABLY GETS
LOCKED IN. WE WILL LIKELY SEE SOME SNOW AT THE START ACROSS THE
INTERIOR...PERHAPS EVEN AT THE COAST...BUT WARMING TEMPS ALOFT WILL
TURN THE PRECIP OVER TO RAIN ON THE COASTAL PLAIN AND FREEZING RAIN
AND SLEET ACROSS THE INTERIOR. THE HEAVIEST PRECIP WILL PROBABLY
OCCUR SATURDAY NIGHT. IT REMAINS TO BE SEEN HOW BIG OF AN ICE EVENT
THIS MAY BE...BUT IT COULD GET PRETTY DICEY ACROSS PORTIONS OF THE
FAR NW INTERIOR AS CLIMATOLOGY SAYS A SFC LOW TRACK CLOSER TO SE MAS
IS MORE LIKELY THAN SOMETHING CUTTING ACROSS THE FAR INTERIOR.
AFTER SUNDAY...FAIRER WEATHER RETURNS BUT WE WILL LIKELY SEE ANOTHER
COLD SHOT ALONG WITH WIND FOR EARLY NEXT WEEK.
&&
.AVIATION /08Z WEDNESDAY THROUGH SUNDAY/...
TODAY AND TONIGHT...
VFR CONDITIONS WITH CIGS EXPECTED AT 4K TO 5K FEET. THERE ARE 2K TO
3K FOOT CIGS IN THE MOUNTAINS AND NEAR OTTAWA CANADA...BUT THESE
SHOULD STAY NORTH OF OUR AREA. HIGH CONFIDENCE IN CIGS
DEVELOPING...MEDIUM CONFIDENCE THAT CONDITIONS REMAIN VFR. FLURRIES
POSSIBLE THIS AFTERNOON THROUGH EARLY TONIGHT MAINLY MHT-BOS-FMH-
HYA-ACK.
THURSDAY...VFR. WINDS BECOMING NORTHEAST BUT REMAINING BELOW 15
KNOTS.
CHRISTMAS DAY...VFR WITH INCREASING CIRRUS AT 25K FEET.
OUTLOOK...FRIDAY NIGHT THROUGH SUNDAY...
SATURDAY...VFR POSSIBLY BECOMING MVFR OR IFR LATE IN RAIN OR MIXED
PRECIPITATION.
SATURDAY NIGHT AND SUNDAY...IFR LIKELY SATURDAY NIGHT INTO EARLY
SUNDAY WITH RAIN OR MIXED PRECIP. IMPROVEMENT FORESEEN BY LATE
SUNDAY. CONFIDENCE LOW ON TIMING ATTM.
&&
.MARINE...
TODAY...
NORTHWEST WINDS 20 TO 25 KNOTS SLOWLY DIMINISHING. SMALL CRAFT
ADVISORY WILL CONTINUE TO MOST OF OUR WATERS. BOSTON HARBOR AND
NARRAGANSETT BAY WILL GUST NEAR 20 KNOTS BUT SHOULD REMAIN BELOW
SMALL CRAFT LEVELS.
TONIGHT...
HIGH PRESSURE BUILDS NORTH OF NEW ENGLAND. THIS WILL BRING WINDS
AROUND TO NORTH OVERNIGHT. FREEZING SPRAY POSSIBLE.
THURSDAY...WINDS INCREASE TO 20-30 KNOTS OVER MOST OF THE WATERS
ESPECIALLY THURSDAY MORNING. THIS BRINGS SEAS UP TO 5-10 FEET
ESPECIALLY EAST OF CAPE COD. WINDS AND SEAS DIMINISH BY THURSDAY
NIGHT.
CHRISTMAS DAY...LIGHT NORTHEAST TO EAST WINDS. SEAS ON MASSACHUSETTS
BAY AND THE OUTER WATERS WILL REMAIN AT 5 FEET OR HIGHER SO SMALL
CRAFT ADVISORIES WILL LINGER OVER THOSE WATERS.
OUTLOOK...FRIDAY NIGHT THROUGH SUNDAY...
SMALL CRAFT CONDITIONS LIKELY OVER MUCH OF THE PERIOD WITH
SOUTHEASTERLY GALES POSSIBLE SATURDAY NIGHT AND SUNDAY IN ADVANCE OF
APPROACHING SURFACE LOW PRESSURE.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
MA...NONE.
NH...NONE.
RI...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 4 PM EST THIS AFTERNOON FOR
ANZ231>235-251.
SMALL CRAFT ADVISORY UNTIL 4 AM EST EARLY THIS MORNING FOR
ANZ230-236.
SMALL CRAFT ADVISORY UNTIL 5 AM EST THURSDAY FOR ANZ237-250-
254>256.
&&
$$
SYNOPSIS...WTB
NEAR TERM...WTB
SHORT TERM...WTB
LONG TERM...EKSTER
AVIATION...WTB/EKSTER
MARINE...WTB/EKSTER
