FXUS61 KBOX 220249
AFDBOX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
949 PM EST MON DEC 21 2009
.SYNOPSIS...
UNSEASONABLY COLD...BLUSTERY AND MAINLY DRY WEATHER THROUGH MID WEEK
IS FOLLOWED BY A GRADUAL MODERATING TREND AND LESS WIND TOWARD THE
END OF THE WEEK. A PERIOD OF WINTRY WEATHER IS POSSIBLE...ESPECIALLY
ACROSS THE INTERIOR THIS WEEKEND AS LOW PRESSURE APPROACHES FROM THE
SOUTHWEST.
&&
.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
MOST OF SOUTHERN NEW ENGLAND REMAINS CLEAR...JUST AN AREA OF CLOUDS
EAST OF A MHT-BOS-FMH LINE. THIS IS LIKELY ASSOCIATED WITH A GULF OF
MAINE SHORTWAVE ROTATING AROUND THE STORM EAST OF NOVA SCOTIA. BOX
RADAR ALSO SHOWS SOME LIGHT ECHOES ACROSS THE MA NORTH SHORE
EXTENDING TO PROVINCETOWN AND TRURO AND MOVING SOUTHEAST...COULD BE A
FEW FLURRIES FROM CAPE ANN ACROSS MASS BAY TO THE OUTER CAPE.
EAST COASTAL MASS WILL HAVE THESE PATCHY CLOUDS THROUGH 1 AM...THE
TIME THE TROF AXIS PASSES THROUGH. BY 7 AM/12Z THE 850-925 MB RH
TRENDS TO DRYING IN THE EAST SO THE TREND SHOULD BE TOWARD CLEARING
ALTHOUGH CLOUDS MAY HANG TOUGH AROUND THE OUTER CAPE OVERNIGHT.
OVERALL THE FORECAST GRIDS LOOK FINE. MAY MAKE A FEW MINOR
ADJUSTMENTS. MAINTAINING THE TEMPERATURE FORECAST...WHICH IS A BLEND
OF THE WARMER GFS MOS WITH THE COOLER NAM MOS.
&&
.SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...
TUESDAY...
ANOTHER QUIET WEATHER DAY IS ON TAP TOMORROW AS SOUTHERN NEW ENGLAND
IS UNDER THE INFLUENCE OF SHORT WAVE RIDGING ACROSS THE REGION. BY
LATER IN THE DAY A PIECE OF THE POLAR VORTEX CURRENTLY OVER THE
NORTHERN GREAT LAKES APPROACHES FROM THE WEST. BOTH NAM AND GFS
INDICATE MODEST MID AND UPPER LEVEL QG FORCING EXTENDING SOUTH INTO
NORTHERN MA AND SOUTHWEST NH. HOWEVER COLUMN REMAINS VERY DRY WITH
RH VALUES LESS THAN 30 PERCENT.
REGARDING TEMPS...AS THE PREVIOUS SHIFT NOTED...DESPITE SEASONABLE
850 TEMPS THIS COLD AIRMASS IS FAIRLY SHALLOW WITH 925 MB TEMPS
ACTUALLY COLDER THAN 850. SO DID A BLEND OF THE WARMER GFS MOS WITH THE
COOLER NAM MOS. THE WARMER GFS MOS VERIFIED BETTER THIS AFTERNOON.
EXPECT HIGHS TO BE FAIRLY CLOSE TO TODAY OR PERHAPS JUST A FEW DEGS
COOLER.
TUESDAY NIGHT...
POLAR VORTEX MOVES ACROSS NORTHERN NEW ENGLAND WITH BULK OF ITS
ASSOCIATED MOISTURE NORTH OF OUR REGION. THIS IS FARTHER NORTH THAN
PREVIOUS MODEL RUNS. ALTHOUGH THE SOUTHERN EDGE OF THE MID LEVEL
FORCING AND MOISTURE WILL GRAZE SOUTHWEST NH...NORTHEAST MA AND
SOUTHEAST ACROSS CAPE COD. THEREFORE COULD SEE SOME FLURRIES TOWARD
WED MORNING ACROSS THIS REGION. ALTHOUGH THE BETTER CHANCE APPEARS
TO BE WED...SO FOR NOW KEPT TUE NIGHT DRY.
AS FOR TEMPS...AGAIN A BLEND OF THE COLDER NAM MOS WITH THE WARMER GFS
MOS.
&&
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
WED AND WED NIGHT...VORTEX MOVES SE ACROSS EASTERN NEW ENG AND THE
ADJACENT WATERS. DEEPER MOISTURE INITIALLY TO THE NORTH EARLY WED
BUT EVENTUALLY SLIDES SWD ACROSS AREA WED AFTERNOON AND NIGHT.
INVERTED TROF EXTENDING WWD FROM OFFSHORE LOW MAY PROVIDE ENOUGH LOW
LEVEL CONVERGENCE ALONG WITH WEAK ISENTROPIC LIFT IN NORTHERLY FLOW
TO BRING CHC LIGHT SNOW ESPECIALLY FROM S NH TO E MA WHERE DEEPER
MOISTURE IS LOCATED.
WE USED A MAV/MET BLEND FOR MAXES WED AND CLOSE TO MAV FOR MINS WED
NIGHT. LOOKS LIKE A CHILLY DAY ON WED WITH INCREASING CLOUD
COVER...ESPECIALLY NORTH AND EAST.
THU...HIGH PRES TO THE NORTH WITH N/NE FLOW ACROSS SNE. LEFTOVER
MOISTURE WILL LIKELY MAINTAIN LOTS OF CLOUD COVER ACROSS EASTERN NEW
ENG WITH SOME SNOW SHOWERS POSSIBLE EARLY ACROSS THE CAPE. LESS
CLOUDS AND MORE SUN CT VALLEY.
HIGH AMPLITUDE PATTERN SETTING UP FOR FRI THROUGH THE WEEKEND WITH
STRONG RIDGE MOVING EWD ACROSS NEW ENG FRI FOLLOWED BY MID LEVEL LOW
LIFTING NE FROM THE GT LAKES. THERE IS CONSIDERABLE MODEL SPREAD
WITH THE TIMING OF NEXT SYSTEM SO FORECAST DETAILS ARE UNCERTAIN BUT
IT DOES APPEAR THIS WILL BE A SIGNIFICANT PRECIP EVENT AS STRONG LOW
LEVEL JET TRANSPORTS ABUNDANT MOISTURE NORTHWARN INTO REGION. ICING
WILL BE A CONCERN...ESPECIALLY IN THE INTERIOR.
FOR FRI XMAS DAY...WE OPTED FOR A DRY FCST AS SFC RIDGING NOSING
DOWN ACROSS SNE SHOULD KEEP MOISTURE TO THE SOUTH AND WEST.
POPS INCREASING FRI NIGHT BUT WE WILL HAVE HIGHEST POPS DURING SAT
AS WE ARE TRENDING SLOWER WITH THE PRECIP ONSET. ECMWF/UKMET ARE
SLOWEST AND DONT BRING IN THE BULK OF PRECIP TIL SAT NIGHT/SUN BUT
WE BLENDED THE GFS/ECMWF FOR TIMING WHICH IS STILL SLOWER THAN GFS.
INITIALLY...COLD HIGH TO THE NORTHEAST WITH DAMMING SIGNATURE
SUGGESTS PRECIP MAY START AS SNOW/ICE...BUT CHANGE TO RAIN NEAR THE
COAST. COLD AIR IS SHALLOW FOR THIS EVENT SO NOT EXPECTING MUCH
INTERIOR SNOW...BUT ICING MAY BE A PROBLEM ESPECIALLY IF SECONDARY
LOW DEVELOPS TO THE SOUTH TO HELP LOCK IN LOW LEVEL COLD FOR AN
EXTENDED PERIOD. EVENTUALLY EXPECT ALL AREAS WILL CHANGE TO RAIN AS
SOUTHERLY LOW LEVEL JET OVERWHELMS THE BOUNDARY LAYER.
THERE CONCERN FOR AT LEAST SOME URBAN AND POOR DRAINAGE
FLOODING...ESPECIALLY WHERE HEAVY SNOW HAS RECENTLY FALLEN.
LOW CONFIDENCE FORECAST SUN DUE TO TIMING DIFFERENCES OF OCCLUSION
MOVING THROUGH. EC/UK ARE SLOW AND WET FOR SUN WHILE GFS/GGEM ARE
FASTER AND DRY.
MON...COLDER AND DRY WESTERLY FLOW.
&&
.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
TONIGHT...HIGH CONFIDENCE IN VFR CONDITIONS. GUSTS TO 25 KT SHOULD
DIMINISH BY 06Z BUT CONTINUE AT HYA-FMH-ACK.
TUESDAY...HIGH CONFIDENCE IN NORTHWEST WIND GUSTS OF 20-30 KNOTS. VFR
CONDITIONS EXPECTED.
TUESDAY NIGHT...
HIGH CONFIDENCE OF VFR CONDITIONS. HOWEVER THERE IS A LOW PROBABILITY
OF CIGS040-050 FROM MHT-BOS-PVC. NORTHWEST WIND GUSTS 20-30 KT WILL
BE RESTRICTED TO HYA AND ACK.
OUTLOOK...WEDNESDAY THROUGH SATURDAY...
WED...MAINLY VFR CIGS DEVELOPING.
WED NIGHT...MODERATE CONFIDENCE OF CIGS LOWERING TO MVFR ESPECIALLY
FROM S NH SWD THROUGH EASTERN MA. SCT SNOW SHOWERS POSSIBLE. VFR
CT VALLEY.
THURSDAY...MODERATE CONFIDENCE MVFR CIGS EASTERN NEW ENG WITH VFR CT
VALLEY.
FRIDAY...VFR.
SAT...MODERATE CONFIDENCE OF MVFR/IFR CONDITIONS DEVELOPING.
&&
.MARINE...
TONIGHT...
LOW END GALES CONTINUE THIS EVENING WITH GUSTS AROUND 35 KT. WINDS
THEN LOWER TO 20-30 KT AFTER MIDNIGHT. ROUGH SEA CONDITIONS WITH A
COMBINATION OF LARGE NW WIND WAVES AND LEFTOVER NE SWELLS FROM
WEEKEND STORM. SOME FREEZING SPRAY LIKELY.
TUESDAY...
NW WINDS 20-25 KT EXPECTED. NE SWELLS LINGER BUT SUBSIDE.
TUESDAY NIGHT...
NW WINDS 20-25 KT CONTINUE. SOME FREEZING SPRAY POSSIBLE.
OUTLOOK...WEDNESDAY THROUGH SATURDAY...
SCA CONDITIONS PERSIST THROUGH THE PERIOD WITH NW FLOW WED/WED
NIGHT...NLY FLOW THU...NE/E FLOW FRI BECOMING SE SAT. LOW PROB OF
GALES SAT.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
MA...NONE.
NH...NONE.
RI...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 7 PM EST TUESDAY FOR ANZ230>237.
GALE WARNING UNTIL MIDNIGHT EST TONIGHT FOR ANZ250-251-254>256.
&&
$$
SYNOPSIS...KJC/NOCERA
NEAR TERM...WTB
SHORT TERM...NOCERA
LONG TERM...KJC
AVIATION...KJC/NOCERA
MARINE...KJC/NOCERA
