342
FXUS61 KBOX 222341
AFDBOX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
641 PM EST SUN NOV 22 2009
SYNOPSIS
HIGH PRESSURE ACROSS THE SAINT LAWRENCE VALLEY WILL MOVE EAST OF
NOVA SCOTIA MONDAY. A LOW PRESSURE WILL APPROACH OUR REGION MONDAY
INTO TUESDAY. WEAK HIGH PRESSURE WILL BRIEFLY VISIT THE AREA TUESDAY
NIGHT INTO WEDNESDAY NIGHT...BEFORE ANOTHER LOW PRESSURE SYSTEM TRACKS
UP THE COAST LATER THURSDAY AND FRIDAY BRINGING THE CHANCE FOR
RAIN. COLD AND BLUSTERY WEATHER IS FORECAST BEHIND THE LOW ON
SATURDAY...WITH DRIER WEATHER FINISHING OFF NEXT WEEKEND.
NEAR TERM /UNTIL 6 AM MONDAY MORNING/
HIGH PRESSURE ACROSS THE SAINT LAWRENCE VALLEY THIS AFTERNOON WILL
MOVE TO NOVA SCOTIA OVERNIGHT. THIS WILL ALLOW NORTHEAST WINDS TO
BECOME MORE FROM THE EAST BY DAYBREAK. CURRENTLY WATCHING AN
EXPANSIVE AREA OF MARINE STRATUS ACROSS THE GULF OF MAINE AND GEORGES
BANK. LATEST VISIBLE IMAGERY SHOWING SOME OF THESE CLOUDS ARE DIURNAL
IN NATURE...AND SHOULD BRIEFLY DISSIPATE AROUND SUNSET...MAINLY
ACROSS THE INTERIOR.
HOWEVER...THE ONSHORE FLOW AND LOWERING TEMPERATURES WILL INCREASE
RELATIVE HUMIDITY AS THE EVENING WEARS ON. EXPECTING THESE LOWER
CLOUDS TO COME BACK LATE THIS EVENING AND LINGER THROUGH THE NIGHT.
SOME DRIZZLE IS POSSIBLE LATE TONIGHT...ESPECIALLY ALONG THE
IMMEDIATE COAST...BUT NOT OVERLY IMPRESSED WITH THE POTENTIAL.
A BLEND OF THE MAV/MET GUIDANCE LOOKS REASONABLE FOR TEMPERATURES.
SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/
STILL SOME UNCERTAINTY WITH THE TRACK AND INTENSITY OF A LOW PRESSURE
MOVING NORTHEAST FROM THE MID ATLANTIC COAST MONDAY NIGHT. FOR
NOW...USED A BLEND OF THE GFS AND NAM TO MINIMIZE FORECAST ERROR.
22/15Z SREF MEAN IS EVEN SLOWER AND WEAKER AND SLOWER THAN THAT
SOLUTION.
MOST 22/12Z MODELS BRING SOME RAINFALL TO SOUTHERN NEW ENGLAND DURING
THE DAY MONDAY...ESPECIALLY DURING THE AFTERNOON. GIVEN THE
UNCERTAINTY IN THE MODEL TIMING...DID TREND THE ARRIVAL OF THIS
PRECIPITATION FASTER THAN PREVIOUS FORECAST. THINKING THE BEST CHANCE
FOR THE ARRIVAL OF THIS RAIN WILL BE MONDAY NIGHT.
USED A BLEND OF THE MAV/MET GUIDANCE ONCE MORE FOR TEMPERATURES
DURING THIS PORTION OF THE FORECAST.
LONG TERM /TUESDAY THROUGH SUNDAY/
TUESDAY...LOW PRESSURE CENTER PROBABLY NEAR/SOUTH OF NANTUCKET 12Z
TUE THEN TRACKS GRADUALLY NORTHEASTWARD TOWARDS NOVA SCOTIA. NAM IS
A BIT WEAKER AND FURTHER INLAND THAN THE OTHER MODELS...TAKING LOW
OVER THE CAPE. FOR THIS PACKAGE GENERALLY LEANED TOWARDS THE
GFS/ECMWF/GGEM. STARTED OFF WITH CHANCE POPS OVER THE
INTERIOR...BUT STILL OPTED TO GO WITH LIKELY NEAR THE COAST. LOW
LEVEL MOISTURE SHOULD KEEP CLOUDS AROUND THROUGH THE DAY.
TUESDAY NIGHT/WEDNESDAY...LOW PRESSURE CONTINUES TO MOVE FURTHER
NORTH/EAST OF THE AREA...BEING REPLACED BY WEAK HIGH PRESSURE. NAM
INDICATES A LAYER OF LOW LEVEL MOISTURE JUST DEEP ENOUGH TO KEEP
CLOUDS AROUND FOR THESE 2 PERIODS...GFS MUCH DRIER. THINK THAT AT
LEAST SOME LOW LEVEL MOISTURE WILL LINGER...AND MID/HIGH CLOUDS
POSSIBLE WITH A SHORT WAVE. SO KEPT PARTLY TO MOSTLY CLOUDY SKIES IN
FORECAST. BUT LOW LEVEL MOISTURE LAYER LIKELY TOO THIN FOR MEASURABLE
PRECIP. TEMPERATURES ARE A BLEND OF MOS. CONTINUED WITH PREVIOUS
THINKING THAT WED WILL BE COOL AND RAW DURING THE AFTERNOON WITH
ONSHORE FLOW.
WEDNESDAY NIGHT THROUGH THANKSGIVING...MOSTLY CLOUDY SKIES/CHANCE
POPS DUE TO COMBINATION OF LOW LEVEL MOISTURE FROM EASTERLY FLOW AS
HIGH PRESSURE DEPARTS...AND AS LOW PRESSURE DEVELOPS OFF THE
CAROLINA COAST.
THURSDAY NIGHT THROUGH FRIDAY NIGHT...WENT WITH HPC GUIDANCE FOR
THIS PERIOD WITH A VIGOROUS LOW PRESSURE SYSTEM POTENTIALLY
AFFECTING OUR AREA. MODEL DISCREPANCIES EXIST...AS ECMWF AND GFS
SHOW SURFACE LOW TRACKING OVER SOUTHERN NEW ENGLAND BUT GGEM KEEPS
CENTER WELL TO THE SOUTH AND EAST. BUT AT THIS TIME HIGH CHANCE TO
LIKELY POPS SEEM PRUDENT FOR THU NIGHT THRU FRI. POSSIBILITY THAT
PRECIP COULD END AS A LIGHT RAIN/SNOW MIX FRI NIGHT IN INTERIOR AS
COLDER AIR SPILLS INTO THE AREA.
SATURDAY...POTENTIAL FOR BLUSTERY AND CHILLY WEATHER AS TIGHT
GRADIENT LINGERS WHILE SURFACE LOW PULLS TO THE NORTHEAST. BOTH
ECMWF AND GFS INDICATE A COLD POOL ALOFT AND LINGERING MOISTURE
WHICH COULD POTENTIALLY LEND ITSELF TO SOME SHOWERS. 1000-500 MB
THICKNESS ARE QUITE LOW...IF THIS SCENARIO PANS OUT CAN/T RULE OUT A
SOME SNOW SHOWERS IN THE FAR INTERIOR...BUT IT WOULD BE TOO WARM AT
THE SURFACE FOR ANY ACCUMULATION.
SUNDAY...HIGH PRESSURE WITH BELOW NORMAL TEMPS.
AVIATION /00Z MONDAY THROUGH FRIDAY/
TONIGHT...MVFR CIGS INITIALLY OVER BOS TO PVD AND SE WILL SPREAD
NORTHWEST OVERNIGHT.
MONDAY...EXPECT VFR CIGS NW MA/FAR SW NH...WHILE CONDITIONS LOWER TO
MVFR-IFR CIGS TO THE S AND E. LOCAL IFR CIGS ALONG THE S
COAST...CAPE COD AND THE ISLANDS DURING THE AFTERNOON. PATCHY RAIN
WILL APPROACH N CT/RI/SE MA DURING THE AFTERNOON WITH LOCAL MVFR
VSBYS.
MONDAY NIGHT...MVFR CIGS...LOWERING TO IFR EASTERN SECTIONS. AREAS
OF MVFR/IFR VSBYS IN RAIN AND FOG...ALSO MAINLY EASTERN SECTIONS.
OUTLOOK /TUESDAY THROUGH FRIDAY/...
TUESDAY...MVFR WITH AREAS OF IFR IN LOW CLOUDS AND SCATTERED SHOWERS.
TUE NIGHT THROUGH THU...MVFR-IFR CONDITIONS MAY LINGER IN LOW
CLOUDS THROUGH THIS PERIOD. MAY HAVE AREAS OF DRIZZLE AND FOG
DEVELOPING LATER WED/WED NIGHT.
THU NIGHT AND FRI...LOW TO MEDIUM CONFIDENCE OF IFR CEILINGS AND
VSBYS IN SHOWERS.
MARINE
NORTHEAST WINDS SHOULD SHIFT EAST OVERNIGHT. THE PERSISTENT ONSHORE
FLOW WILL CONTINUE TO BUILD SEAS OVERNIGHT ACROSS THE COASTAL WATERS
OF MA AND RI. A LOW PRESSURE MOVING NORTHEAST FROM THE MID ATLANTIC
COAST MONDAY AND MONDAY NIGHT WILL LIKELY INCREASE WINDS DURING THIS
TIME AS WELL. SMALL CRAFT ADVISORIES CONTINUE FOR MOST WATERS.
OUTLOOK /TUESDAY THROUGH FRIDAY/...
TUESDAY AND TUE NIGHT...SCA WINDS/SEAS LINGER TUE AS LOW PRESSURE TRACKS
TOWARDS NOVA SCOTIA. WINDS DIMINISH TUE NIGHT AND WED BUT SEAS WILL
BE SLOWER TO SUBSIDE.
WEDNESDAY THROUGH FRIDAY...PERSISTENT EASTERLY WINDS WILL
LIKELY CAUSE SEAS TO REMAIN ABOVE SCA THRESHOLDS ACROSS THE OUTER WATERS.
WINDS AND SEAS SHOULD INCREASE THANKSGIVING NIGHT AND FRIDAY IN
ADVANCE OF THE NEXT SYSTEM APPROACHING FROM THE SOUTH. POSSIBILITY OF
GALES FRI.
BOX WATCHES/WARNINGS/ADVISORIES
CT...NONE.
MA...NONE.
NH...NONE.
RI...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 5 AM TO 5 PM EST MONDAY FOR
ANZ232>235-237.
SMALL CRAFT ADVISORY UNTIL 5 PM EST MONDAY FOR ANZ250-254>256.
SYNOPSIS...BELK/NMB
NEAR TERM...BELK
SHORT TERM...BELK
LONG TERM...NMB
AVIATION...BELK/NMB
MARINE...BELK/NMB
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