FXUS61 KBOX 220907
AFDBOX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
407 AM EST TUE DEC 22 2009
.SYNOPSIS...
DRY AND COLD WEATHER MIDWEEK WILL GRADUALLY MODERATE 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 PM THIS EVENING/...
LOW PRESSURE EAST OF NOVA SCOTIA SLOWLY PULLS AWAY TODAY WITH A
NORTHWEST SURFACE FLOW IN POSITION THROUGH THE DAY. MIXING TODAY WILL
BE CONCENTRATED AT OR BELOW 925 MB WITH WINDS IN THIS MIXING LAYER
AROUND 25 KNOTS...POSSIBLY NEAR 30 KNOTS AT TIMES. TEMPERATURES IN
THIS MIXED LAYER ARE THE EQUIVILENT OF -13C TO -15C AT 850 MB...SO
MAX TEMPS WILL STRUGGLE TO BREAK FREEZING. MAX TEMPS ARE BASED ON GFS
MOS.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/...
CLOSED UPPER LOW/POLAR VORTEX DIVES OUT OF ONTARIO TODAY AND CROSSES
SOUTHERN NEW ENGLAND LATER TONIGHT AND WEDNESDAY. DEEPER MOISTURE IS
SLOW TO MOVE IN...SO SKIES TONIGHT MAY START MOSTLY CLEAR. BUT THE
TREND SHOULD BE TOWARD INCREASING CLOUDS. THE UPPER LOW CROSSES VT/NH
WEDNESDAY AND PASSES EAST OF MASS ON WEDNESDAY...WITH ITS ATTENDING
COLD POOL MOVING ACROSS OUR NORTHERN AND EASTERN AREAS. THIS SHOULD
BE THE AREA OF BEST FORCING. TIME CROSS-SECTIONS SHOW HIGH RH VALUES
SURFACE TO 850 MB WEDNESDAY. EXPECT MOSTLY CLOUDY SKIES WITH CHANCE
POPS FOR SNOW SHOWERS NORTH AND EAST.
AS FOR TEMPS...AGAIN USED THE GFS MOS GUIDENCE.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
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 /09Z TUESDAY THROUGH SATURDAY/...
TODAY...VFR WITH MOSTLY CLEAR SKIES. HIGH CONFIDENCE OF NORTHWEST
WINDS WITH GUSTS AROUND 25 KNOTS.
TONIGHT...VFR WITH DIMINISHING NORTHWEST WIND. LOW CONFIDENCE OF VFR
CIGS IN MHT AND BAF TOWARD SUNRISE.
WEDNESDAY...HIGH CONFIDENCE OF VFR CIGS. SCATTERED SNOW SHOWERS WITH
BEST CONFIDENCE AT MHT AND BOS IN THE AFTERNOON.
OUTLOOK...WEDNESDAY NIGHT THROUGH SATURDAY...
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...
TODAY...NORTHWEST WINDS GUSTING 30 KNOTS THIS MORNING AND 25 KNOTS THIS
AFTERNOON. SEAS SLOWLY DIMINISHING BUT REMAINING ABOVE 5 FEET ON THE
OUTER WATERS THROUGH THE DAY. CONTINUED CHANCE OF FREEZING SPRAY.
TONIGHT...NORTHWEST WINDS WITH GUSTS 20 TO 25 KNOTS ON MOST OF THE
WATERS. SEAS SLOWLY DIMINISHING. FREEZING SPRAY POSSIBLE. SMALL CRAFT
ADVISORY CONTINUES FOR MOST OF THE WATERS.
WEDNESDAY...NORTHWEST WINDS CONTINUE WITH GUSTS 20 TO 25 KNOTS ON
MOST OF THE WATERS. SEAS BUILD SLOWLY IN THE AFTERNOON.
OUTLOOK...WEDNESDAY NIGHT 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 5 PM EST WEDNESDAY FOR ANZ231>235-
237-250-254>256.
SMALL CRAFT ADVISORY UNTIL 6 PM EST THIS EVENING FOR ANZ230-
236-251.
&&
$$
SYNOPSIS...WTB/KJC
NEAR TERM...WTB
SHORT TERM...WTB
LONG TERM...KJC
AVIATION...WTB/KJC
MARINE...WTB/KJC
