FXUS61 KBOX 221035
AFDBOX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
535 AM EST TUE DEC 22 2009
.SYNOPSIS...
DRY AND COLD WEATHER MIDWEEK WILL GRADUALLY MODERATE BY THURSDAY.
LOW PRESSURE WILL APPROACH FROM THE SOUTHWEST CHRISTMAS DAY...WHICH
MAY BRING A PERIOD OF WINTRY WEATHER FRIDAY NIGHT AND SATURDAY. THIS
LOW WILL TAKE UP RESIDENCE OVER EASTERN CANADA BY EARLY NEXT
WEEK...WHICH WILL BRING ANOTHER PERIOD OF RELATIVELY DRY BUT COLD
WEATHER.
&&
.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 EQUIVALENT 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 GUIDANCE.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
MEDIUM RANGE MODEL SUITE SHOWS WIDENING SPREAD IN ITS SOLUTIONS OVER
TIME...ESPECIALLY THE ECMWF FROM CHRISTMAS DAY ONWARD WHICH IS
TENDING TO SLOW THE MOVEMENT OF WEATHER SYSTEMS DOWN DRAMATICALLY
ACROSS THE LOWER 48. FELT THAT THIS APPEARED TO BE A SLOW OUTLIER AS
COMPARED TO MOST OF THE OTHER GUIDANCE AS WELL AS THE SOLUTION
OFFERED BY HPC. USED A BLEND OF THE PREVIOUS FORECAST ALONG WITH THE
00Z GFS AND GGEM...WHICH WAS CLOSE TO CONSENSUS.
WEDNESDAY NIGHT-THURSDAY...HIGH PRES ACROSS CENTRAL QUEBEC WILL
SLOWLY SHIFT E DURING THIS PERIOD. WITH COLD AIR ADVECTION
CONTINUING ACROSS THE WATERS...ALONG WITH A WEAK SHORT WAVE MOVING
THROUGH...MAY BRING A CHANCE OF SNOW SHOWERS ALONG THE IMMEDIATE E
COAST AND ESPECIALLY ON CAPE COD AND THE ISLANDS WITH GENERAL N WIND
FLOW. WILL ALSO SEE A LOT OF CLOUDS ACROSS CENTRAL AND EASTERN AREAS
WITH LEFTOVER LOW AND MID LEVEL MOISTURE...WITH A BETTER CHANCE OF
SUN ACROSS THE CT VALLEY. CLOUDS WILL TEND TO MELT AWAY DURING
THURSDAY AFTERNOON.
TEMPS WILL START TO REBOUND AS THE HIGH PRES RIDGE BUILDS ACROSS THE
REGION...SHUTTING OFF THE CANADIAN COLD AIR /FOR NOW/. HIGHS ON
THURSDAY MAY APPROACH 40 ALONG THE E COAST...WITH MOST AREAS HAVING
A SHOT OF ABOVE FREEZING READINGS.
CHRISTMAS EVE...A FAIR NIGHT WITH PARTLY CLOUDY SKIES BUT CHILLY
READINGS...THOUGH A BIT MILDER THAN THE LAST SEVERAL NIGHTS.
FOR CHRISTMAS DAY AND BEYOND...MODELS HAVING TROUBLE RESOLVING
WEATHER SYSTEMS ACROSS NORTH AMERICA...ESPECIALLY INTO THE PACIFIC.
DOES APPEAR A HIGHLY AMPLIFIED BLOCKING PATTERN WILL SET UP BY THIS
WEEKEND. BIG QUESTION WILL BE HOW QUICKLY THE LONG WAVE RIDGE MOVES
E OF NEW ENGLAND...WHILE A COMPLEX LOW WORKS OUT OF THE MISSISSIPPI
VALLEY INTO THE GREAT LAKES. MODELS ARE STILL SIGNALING THE
POSSIBILITY OF A SIGNIFICANT MIXED PRECIPITATION EVENT ACROSS INLAND
AREAS /S NH INTO N CENTRAL AND WESTERN MASSACHUSETTS AS WELL AS N
CENTRAL CT/ FRIDAY NIGHT INTO SATURDAY MORNING.
FOR CHRISTMAS DAY...MORE CONFIDENCE OF A DRY AND SEASONABLE DAY AS
HIGH PRES RIDGE CONTINUES ACROSS THE REGION...BUT CLOUDS WILL BE
INCREASING.
AT THIS POINT...KEPT TIMING SOMEWHAT SIMILAR TO THE PREVIOUS
FORECAST. THIS BRINGS PRECIP INTO WESTERN AREAS DURING CHRISTMAS
EVENING...THEN PUSHING E AROUND OR AFTER MIDNIGHT. STILL SEEING THE
COLD AIR DAMMING SIGNAL...WHICH IS NOT SURPRISING CONSIDERING THE
DEEP SNOWPACK ACROSS CENTRAL AND EASTERN AREAS AS WELL AS INTO N CT.
STILL A CONCERN WITH ICING ACROSS THE INTERIOR.
AT THIS POINT...CONTINUED WITH LIKELY POPS FOR LATE FRI NIGHT INTO
AT LEAST MIDDAY SATURDAY...WITH HIGH CHANCE POPS INTO SAT NIGHT.
HAVE STARTED OFF WITH MIXED PRECIP DURING FRI NIGHT...THEN SHOULD
CHANGE OVER TO RAIN AS SE WINDS INCREASE ALONG THE COAST. MODELS
SHOW ANOTHER LOW FORMING ON THE FRONT AS IT WRAPS ACROSS THE REGION
SATURDAY AFTERNOON...BUT THE TIMING OF THIS IS CRITICAL. IF THIS LOW
FORMS EARLIER...THEN IT MAY LOCK THE COLDER AIR INLAND CAUSING A
LONGER PERIOD OF MIXED OR FREEZING PRECIP. SOMETHING TO CLOSELY
MONITOR. FEEL THAT LOW LEVEL WINDS WILL EVENTUALLY SHIFT TO S AND
PICK UP...WHICH WILL FINALLY SCOUR OUT THE LOW LEVEL COLD AIR DURING
SATURDAY.
MODELS ARE ALSO SIGNALING A GOOD SLUG OF PRECIP MOVING INTO THE
REGION WITH GOOD LOW LEVEL MOISTURE CONVERGENCE. IF THIS HAPPENS...
COULD HAVE PROBLEMS WITH URBAN AND POOR DRAINAGE FLOODING...
ESPECIALLY IF THE HEAVIER PRECIP FALLS ACROSS AREAS WHERE HEAVY SNOW
FELL THIS PAST SUNDAY-MONDAY.
SUNDAY-MONDAY...HAVE LEANED TOWARD A SOLUTION WHICH PARKS THE LOW
ACROSS EASTERN CANADA. SOME LEFTOVER SNOW SHOWERS EARLY SUNDAY
POSSIBLE...THEN HAVE FORECASTED A DRY BUT COOL FLOW ROTATING AROUND
THE BASE OF THE UPPER LEVEL VORTEX. HOWEVER...LOW CONFIDENCE DUE TO
MODEL TIMING ISSUES.
&&
.AVIATION /10Z 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...
WEDNESDAY NIGHT...CONTINUED MODERATE CONFIDENCE OF CIGS LOWERING TO
MVFR FROM S NH INTO EASTERN MA. SCT SNOW SHOWERS POSSIBLE. VFR
THURSDAY...MODERATE CONFIDENCE MVFR CIGS EASTERN MA INTO S CENTRAL
NH IN THE MORNING...IMPROVING TO VFR. CONTINUED VFR ELSEWHERE.
FRIDAY...VFR...LOWERING TO MVFR CIGS DURING THE AFTERNOON ACROSS
CT/W MA.
FRIDAY NIGHT...MODERATE CONFIDENCE OF MVFR CIGS MOVING FROM SW-NE.
LOW TO MODERATE CONFIDENCE OF MVFR-IFR VSBYS IN MIXED PRECIPITATION
MAINLY AFTER MIDNIGHT.
SATURDAY...MODERATE CONFIDENCE OF MVFR-IFR CONDITIONS AND MIXED
RAIN/SNOW SHOWERS...SOME MIX WITH FZRA WELL INLAND EARLY.
&&
.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...
WEDNESDAY NIGHT-THURSDAY NIGHT...N-NW WINDS GUSTING UP TO 25-30 KT.
FRIDAY-SATURDAY...NE WINDS VEER TO S-SE SATURDAY. SMALL CRAFT GUSTS
CONTINUE. LOW CHANCE OF GALE GUSTS ON THE OUTER WATERS SATURDAY.
&&
.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/EVT
NEAR TERM...WTB
SHORT TERM...WTB
LONG TERM...EVT
AVIATION...WTB/EVT
MARINE...WTB/EVT
