FXUS61 KBOX 241342
AFDBOX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
840 AM EST THU DEC 24 2009
.SYNOPSIS...
HIGH PRESSURE BUILDS SOUTH INTO NEW ENGLAND TODAY PUSHING OUT
CLOUDS AND PROVIDING DRY WEATHER. THIS WILL ALSO BRING MODERATING
TEMPERATURES THROUGH FRIDAY. LOW PRESSURE WILL TRACK UP THE EASTERN
SEABOARD THIS WEEKEND...BRINGING A PERIOD OF WINTRY WEATHER INLAND
WITH MAINLY RAIN AND WIND ALONG THE COAST. THE LOW AND ITS
PRECIPITATION SHOULD DEPART THE REGION SOMETIME LATER SUNDAY.
ANOTHER HIGH WILL BUILD OUT OF CANADA...BRINGING MORE DRY BUT
BLUSTERY AND COLD WEATHER INTO THE MIDDLE OF NEXT WEEK.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
WATCHED A BAND OF SNOW SHOWERS SET UP ACROSS MASSACHUSETTS AND CAPE
COD BAYS INTO THE LOWER AND MID CAPE ON BOTH KBOX AND TBOS RADARS
STARTING AROUND 10Z. ALSO SAW VSBYS LOWER TO 1 1/2-2SM AT BOTH KFMH
AND KHYA IN THE SNOW SHOWERS. CAN ALSO SEE SOME N-S ENHANCEMENT WHEN
CLOSELY LOOKING AT THE IR SATELLITE. WITH TEMPS RISING...ALREADY
SEEING THE SNOW MIXING OR CHANGING TO RAIN ON THE OUTER CAPE AT
KCQX.
THIS APPEARS TO BE A LEFTOVER SHORT WAVE MOVING AROUND THE POLAR
VORTEX MOVING E OF CAPE COD ALONG WITH A BIT OF OCEAN ENHANCEMENT
CAUSING THIS SNOW BAND DEVELOPMENT. CAN SEE THE MOISTURE FEEDER
ROTATING ACROSS THE GULF OF MAINE INTO MA BAY ON THE WATER VAPOR
SATELLITE. NOTED THE SNOW THAT MOVED OFF DOWNEAST MAINE...THOUGH
RETURNS LIKELY PASSING BELOW THE RADAR BEAMS NOW.
WITH THE BAND CONCENTRATING ON THE LOWER CAPE...HAVE UPDATED THE
ZONES AND GRIDS TO INCLUDE CHANCE TO LIKELY POPS THROUGH THIS
MORNING...THEN WILL TAPER OFF THIS AFTERNOON AS THE VORTEX AND ITS
MOISTURE FEED PUSHES E. HAVE ALSO MENTIONED A MIX OF RAIN ON THE
OUTER CAPE.
ALSO UPDATED TEMPS/DEWPTS AND WINDS. NOTED N-NW WIND GUSTS UP TO
25-27 KT AT BOTH KPVC AND KACK AT 13Z.
FROM PREVIOUS DISCUSSION...
POLAR VORTEX NOW MOVING OUT ACROSS GEORGES BANK. LINGERING LOW LEVEL
MOISTURE IN PLACE AT THE START OF THE DAY...SO EXPECT CLOUDS AT
FIRST. BUT WITH THE LOW MOVING AWAY AND WITH CANADIAN HIGH PRESSURE
BUILDING SOUTH ACROSS NEW ENGLAND...AND WITH DRYING ABOVE 925 MB...WE
SHOULD SEE THE CLOUDS DECREASE THROUGH THE DAY.
WITH THE COLD CORE OFFSHORE AND 850 MB TEMPS WARMING ABOVE -6C THIS
MORNING...AND WITH SST/S AROUND 5C...EXPECT AN EARLY END TO ANY
OCEAN SNOW SHOWERS AROUND THE OUTER CAPE.
LOW LEVEL TEMPS SUPPORT MAX TEMPS AROUND 40F. TEMPERATURES ARE A
BLEND OF NAM AND GFS MOS.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/...
HIGH PRESSURE IN CONTROL MOST OF THE PERIOD...DRY WEATHER WITH A
DEVELOPING NORTHEAST FLOW OFF MASSACHUSETTS BAY. HIGH CLOUDS SHOULD
INCREASE THROUGH THE DAY...ESPECIALLY IN THE AFTERNOON/EVENING...AS
THE MIDWEST STORM PUSHES ITS CLOUD SHIELD EAST.
DEWPOINTS IN THE MID TEENS INLAND TO NEAR 30 CAPE/ISLANDS...THIS
SHOULD BE THE LIMIT FOR NIGHTTIME MIN TEMPS. TEMPS AT 925 MB REMAIN
AROUND -2C TO -3C FRIDAY...SIMILAR TO TODAY...SO EXPECT MAX TEMPS
XMAS DAY IN THE MID 30S TO AROUND 40.
IF THERE IS ANY UNCERTAINTY IN THIS PART OF THE FORECAST IT WOULD BE
THE POTENTIAL FOR MARINE INFLUENCE AT LOW LEVELS ESPECIALLY IN
EASTERN MASS. IF THE NORTHEAST FLOW IS ABLE TO MAINTAIN ENOUGH
MOISTURE IN THE LOWEST LAYERS IT COULD MAKE XMAS DAY CLOUDIER WITH
POTENTIAL DRIZZLE ALONG THE SOUTH COAST. LOW CONFIDENCE IN THIS
SCENARIO SO WE WILL GO WITH THE DRIER FORECAST.
&&
.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
MEDIUM RANGE MODEL SOLUTIONS SHOWING A BIT BETTER CONTINUITY ON THE
TIMING OF VERY STRONG LOW PRES MOVING THROUGH THE MISSISSIPPI VALLEY
AND GREAT LAKES FOR CHRISTMAS AND INTO THIS WEEKEND. ANOTHER WEAKER
LOW AND FRONT WILL SWING AROUND THIS LOW TOWARD THE REGION. THE
UPPER LEVEL PATTERN CONTINUES HIGHLY AMPLIFIED...WHICH MEANS SLOW
MOVEMENT OF WEATHER SYSTEMS ACROSS THE LOWER 48. LOOKS TO BE A
RATHER WET...AND POTENTIALLY WINTRY PORTION OF THIS WEEKEND. BEYOND
THIS...STILL DEPENDING UPON HOW THE STRONG LOW MOVES INTO CANADA...
APPEARS DRY BUT RATHER COLD WEATHER WILL RETURN INTO THE MIDDLE OF
NEXT WEEK.
FRIDAY NIGHT...APPEARS THE PRECIP WILL HOLD OFF THROUGH MOST OF THE
NIGHT...BUT COULD SEE SOME MIXED PRECIP SNEAK INTO THE CT VALLEY AND
E SLOPES OF THE BERKSHIRES LATE. WILL BE A SHARP ONSET LINE THANKS
TO THE STRONG HIGH TO THE E. WILL TAKE A WHILE TO MOISTEN THE LOWER
ATMOSPHERE...BUT WINDS SHIFTING TO EAST WILL HELP IN THIS PROCESS.
MIGHT SEE SOME DRIZZLE SNEAK IN WELL AHEAD OF THE MAIN PRECIP...
WHICH COULD CAUSE SOME PROBLEMS ESPECIALLY INLAND IF A MIXED
FREEZING DRIZZLE OCCURS.
THIS WEEKEND...AS LOW LEVEL MOISTURE CONTINUES TO INCREASE...EXPECT
STEADY PRECIPITATION TO STEADILY MOVE EAST ACROSS THE REGION DURING
SATURDAY. STILL SOME TIMING ISSUES WITH THE ONSET OF THE PRECIP...
BUT HAVE FORECASTED THE START DURING THE MORNING HOURS ACROSS S
NH/CENTRAL-W MA AND N CT. TEMPS MAY STILL BE CLOSE TO OR BELOW
FREEZING AT THE START...SO HAVE FORECASTED A WINTRY MIX FOR SOME
AREAS. SHOULD SEE TEMPS RISE ABOVE FREEZING BY AROUND MIDDAY AS THE
EAST WINDS FRESHEN...HELPING TO SCOUR OUT THE COLD AIR. HOWEVER...
COULD SEE TRAVEL PROBLEMS WITH A THIN LAYER OF ICE OR SNOW.
WILL SEE THE HEAVIEST PRECIPITATION SATURDAY NIGHT WITH GOOD LOW
LEVEL MOISTURE CONVERGENCE. ACROSS E MA/RI INTO N CT...COULD SEE
AREAS OF HEAVY RAINFALL OVERNIGHT WHICH MAY CAUSE AREAS OF URBAN AND
POOR DRAINAGE FLOODING...ESPECIALLY SINCE THE AREAS THAT RECEIVED
HEAVY SNOWFALL EARLIER THIS WEEK. MAY SEE UP TO AN INCH OF QPF...
MAINLY ACROSS CENTRAL AND SOUTHERN AREAS. HOWEVER...TEMPERATURES MAY
REACH CRITICAL LEVELS ACROSS FAR INLAND AREAS...SO COULD SEE THE
WINTRY MIX RETURN FOR AT LEAST PART OF THE NIGHT. TEMPS WILL LIKELY
HOLD STEADY BUT SHOULD SLOWLY RISE OVERNIGHT...SO THE MIX MAY BE
BRIEF. THIS WILL DEFINITELY BE SOMETHING TO WATCH CLOSELY.
AT THIS POINT...THE WEAK LOW WILL CROSS THE REGION...SO WILL SEE THE
HEAVY PRECIP SHIFT INTO NORTHERN NEW ENGLAND EARLY SUNDAY MORNING...
THEN WILL TAPER OFF FROM SW-NE DURING THE DAY. CLOUDS WILL LINGER
INTO SUNDAY NIGHT AND MONDAY AS THE LOW REMAINS ACROSS EASTERN
CANADA. TEMPS WILL FALL BACK A BIT...BUT NOT DRAMATICALLY FOR NOW.
MONDAY...CLOUDS WILL TEND TO BREAK...BUT WILL LINGER ACROSS SOUTHERN
NEW HAMPSHIRE AS ANOTHER SHORT WAVE APPROACHES OUT OF CANADA. NOTING
ANOTHER SHOT OF ARCTIC AIR WORKING S FROM CENTRAL CANADA...AS H85
TEMPS DROP TO -24C TO -27C. THE SHORT WAVE WILL SPIN UP A FRONT...
WHICH WILL BRING MORE CLOUDS AND AN AREA OF SNOW SHOWERS ACROSS THE
REGION LATE MONDAY INTO MONDAY NIGHT. WITH THE STRONG LAPSE RATES...
MAY SEE A WINDEX EVENT AS THE COLDER AIR WORKS IN MONDAY NIGHT.
TUESDAY-WEDNESDAY...RIGHT NOW...MAY SEE LEFTOVER SNOW SHOWERS ACROSS
THE E COAST EARLY TUESDAY...OTHERWISE APPEARS THAT ARCTIC AIR WILL
BRING ANOTHER ROUND OF DRY BUT COLD WEATHER TO THE REGION. TEMPS
DROP WELL BELOW NORMAL FOR LATE DECEMBER...AND WILL LIKELY SEE W-NW
WINDS KICK UP AS WELL. STILL SOME TIMING ISSUES THIS FAR OUT AS THE
BLOCKING PATTERN APPEARS TO TRY TO BREAK DOWN.
&&
.AVIATION /13Z THURSDAY THROUGH MONDAY/...
TODAY...
HAVE LOWERED CIGS TO MVFR-IFR ON THE CAPE AND ISLANDS WITH SNOW AND
MIX RAIN/SNOW SHOWERS. HAVE SLOWED THE EASTWARD MOVEMENT OF THE LOW
CLOUDS TIL AROUND MIDDAY OR SO...EVEN AS LATE AS 21Z AT KACK ON THE
12Z TAF UPDATE. WILL SEE CIGS IMPROVE TO VFR ACROSS N CENTRAL CT/W
MA/SW NH BY MIDDAY...WITH VFR CONDITIONS MOVING E DURING THE
AFTERNOON. MENTIONED N-NW WIND GUSTS UP TO 25 KT ON THE CAPE AND
NANTUCKET. WILL SEE WINDS VEER TO N AND DIMINISH DURING THE
AFTERNOON.
TONIGHT...
MEDIUM TO HIGH CONFIDENCE IN CLEARING SKIES AND DIMINISHING WIND.
FRIDAY...
VFR WITH INCREASING AFTERNOON/EVENING CLOUDS AT 25K FEET.
OUTLOOK...FRIDAY NIGHT THROUGH MONDAY...
FRIDAY NIGHT...VFR CIGS.
SATURDAY...VFR OR MVFR CIGS TO START...LOWERING TO MVFR OR IFR FROM
W-E AS RAIN OR MIXED PRECIPITATION ACROSS WESTERN AREAS IN THE
MORNING...PUSHING E IN THE AFTERNOON. MODERATE CONFIDENCE ON TIMING.
SATURDAY NIGHT AND SUNDAY...IFR CIGS AND MVFR-IFR VSBYS WITH RAIN OR
MIXED PRECIPITATION. LOW TO MODERATE CONFIDENCE ON TIMING.
CONDITIONS MAY IMPROVE TO MVFR-VFR ACROSS WESTERN AREAS SUNDAY
AFTERNOON.
MONDAY...VFR...BUT POSSIBLE MVFR IN SNOW SHOWERS AT TIMES.
&&
.MARINE...
TODAY...
NORTHWEST WINDS BECOME NORTH WITH GUST POTENTIAL TO 25 KT...EXCEPT
GUSTS TO 20 KNOTS BOSTON HARBOR AND NARRAGANSETT BAY. HAVE INCLUDED
MENTION OF RAIN/SNOW SHOWERS THROUGH THE MORNING WITH REDUCED VSBYS.
TONIGHT...
NORTH TO NORTHEAST WINDS DIMINISH AS CANADIAN HIGH PRES BUILDS INTO
NEW ENGLAND. SEAS REMAIN AT OR ABOVE 5 FEET ON THE OUTER WATERS
THROUGH THE NIGHT.
FRIDAY...
LIGHT NORTHEAST TO EAST WINDS. SEAS STILL AT OR ABOVE 5 FEET...MAINLY
ON OUTER WATERS.
OUTLOOK...FRIDAY NIGHT THROUGH MONDAY...
FRIDAY NIGHT...SMALL CRAFT WINDS AND SEAS CONTINUE.
SATURDAY-SUNDAY...EAST TO SOUTHEAST WINDS LIKELY INCREASE TO GALE
SATURDAY NIGHT AND CONTINUE INTO SUNDAY.
MONDAY...SMALL CRAFT WINDS AND SEAS.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
MA...NONE.
NH...NONE.
RI...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 11 PM EST THIS EVENING FOR
ANZ231>235-237-256.
SMALL CRAFT ADVISORY UNTIL 11 AM EST FRIDAY FOR ANZ250-251-
254-255.
&&
$$
SYNOPSIS...WTB/EVT
NEAR TERM...WTB/EVT
SHORT TERM...WTB
LONG TERM...EVT
AVIATION...WTB/EVT
MARINE...WTB/EVT
