000
FXUS61 KBOX 160156
AFDBOX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
956 PM EDT WED OCT 15 2008
.SYNOPSIS...
WEAK HIGH PRESSURE WILL MOVE OVER NEW ENGLAND THIS EVENING. A COLD
FRONT WILL THEN MOVE ACROSS NEW ENGLAND ON THURSDAY BRINGING SHOWERS.
HIGH PRESSURE FROM THE NORTHERN PLAINS WILL BRING FAIR AND COOLER
WEATHER FOR THE WEEKEND. THE NEXT COLD FRONT WILL THEN MOVE THROUGH
LATE MONDAY OR EARLY TUESDAY.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
LEADING EDGE OF SHOWERS ASSOCIATED WITH THE COLD FRONT STILL BACK
ACROSS EASTERN GREAT LAKES AND NOT LIKELY TO MOVE INTO OUR NW ZONES
UNTIL AFTER 6 AM. 18Z GFS/NAM AND 21Z SREF SUPPORT THIS TIMING SO WE
HAVE DROPPED POPS FROM THE FORECAST TONIGHT AS IT SHOULD REMAIN DRY
BEFORE 6 AM.
PREVIOUS DISCUSSION BELOW:
AFTER REVIEWING THE LATEST 18Z SUITE OF MODEL DATA HAVE MADE SOME
CHANGES TO THE CURRENT CLOUD FORECAST. AN AREA OF STRATUS THAT
AFFECTED THE CAPE/ISLANDS TODAY LOOKS TO EXPAND FURTHER NORTHWEST
ONTO PORTIONS OF THE COASTAL PLAIN AND POSSIBLY EVEN FURTHER WEST
OVERNIGHT. THE NAM BOUNDARY LAYER RELATIVE HUMIDITIES SHOW THIS
NICELY AND WITH DEWPOINTS IN THE 50S THIS SCENARIO SEEMS TO MAKE
SENSE. THEREFORE...WILL SHOW LOW STRATUS GRADUALLY SPREADING INTO
PORTIONS OF THE REGION. IN ADDITION...THE SREF PROBABILITIES ARE
SHOWING SOME DECENT NUMBERS FOR THE POTENTIAL OF PATCHY FOG
DEVELOPING AS WELL.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
COLD FRONT MOVES THROUGH NEW ENGLAND TUESDAY AFTERNOON AND EVENING.
THE MAIN LOW PRESSURE CENTER PULLING THE LOW HAS ELECTED TO PASS WELL
NORTH OF THE CANADIAN BORDER. BUT THE FRONT WILL BE SUPPORTED BY A
110 KNOT JET MOVING OUT OF THE OHIO VALLEY AND ACROSS SOUTHERN NEW
ENGLAND. PRECIPITABLE WATER VALUES ARE FORECAST BETWEEN 1.5 AND 1.75
INCHES IN A PLUME OF MOISTURE FROM THE WESTERN GULF OF MEXICO. WITH
THIS COMBINATION OF MOISTURE AND LIFT IN THE NEXT 24 HOURS...WE WILL
GO WITH CATEGORICAL POPS UNDER THE LEFT EXIT REGION OF THE JET AND
LIKELY POPS FARTHER SOUTH. CLOUDS WILL LIMIT MAX TEMPS THURSDAY...BUT
WITH 12C ALOFT AND A SOUTHWEST WIND WE SHOULD STILL REACH THE
60S...WITH A FEW WARMER SPOTS IN THE UPPER 60S.
THE FRONT MOVES OFF THURSDAY NIGHT. EXPECT CLEARING SKIES AFTER FROPA
AND COOLING TEMPERATURES. TEMPS LAST NIGHT UPSTREAM IN MINNESOTA AND
THE EASTERN DAKOTAS WERE IN THE UPPER 30S TO MID 40S...WHICH SEEMS A
GOOD RANGE TO USE FOR THURSDAY NIGHT.
WINDS OVER THE CAPE AND ISLANDS AND OTHER SOUTHEAST SECTIONS SHOW
SOME MIXING POTENTIAL IN THE COLD ADVECTION BEHIND THE FRONT. WINDS
AT 950 MB ARE FORECAST 20 TO 25 KNOTS. WE WILL GO CLOSE TO
THIS...WITHIN THE RANGE OF 15 TO 25 KNOTS.
&&
.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
FRIDAY...
A DRY AND COOL PUSH OF AIR WILL FOLLOW BEHIND A COLD FRONT FOR
FRIDAY. SKIES SHOULD BE PARTLY TO MOSTLY SUNNY ACROSS THE REGION.
HOWEVER...WITH 850 MB TEMPERATURES BETWEEN 0C AND -2C HIGHS SHOULD
BE HELP IN THE UPPER 50S TO AROUND 60.
FRIDAY NIGHT...
HIGH PRESSURE NOSING IN FROM THE GREAT LAKES WILL PROVIDE FOR A
CHILLY NIGHT. SKIES SHOULD BE PARTLY CLOUDY AS THE MODELS DO SHOW
AN INCREASE IN HIGH CLOUDS OUT AHEAD OF THE AXIS OF THE TROUGH
AXIS. NONETHELESS...AIRMASS IS COLD ENOUGH TO SUPPORT LOWS AROUND
30 ACROSS PORTIONS OR SOUTHWEST NH/NORTHWEST MA...TO THE LOWER 40S
IN THE URBAN HEAT ISLAND OF BOSTON/OUTER CAPE/NANTUCKET. MUCH OF
THE REST OF THE REGION WILL SEE LOWS WELL DOWN INTO THE 30S.
SATURDAY AND SATURDAY NIGHT...
A REINFORCING SHOT OF COOL AIR WILL BE USHERED INTO THE REGION. 850
MB TEMPERATURES DROP TO BETWEEN -3C AND -4C. SKIES SHOULD PARTLY
SUNNY ACROSS MUCH OF THE REGION...BUT WE DO EXPECT SOME SCATTERED
STRATO-CUMULUS CLOUDS. IN ADDITION...SKIES MAY REMAIN MOSTLY CLOUDY
ACROSS PORTIONS OF THE CAPE AND NANTUCKET WITH SOME OCEAN EFFECT
CLOUDINESS AS LAPSE RATES STEEPEN. WOULD NOT EVEN BE SURPRISED IF WE
SEE SOME OCEAN EFFECT SPRINKLES/VERY LIGHT RAIN SHOWERS SATURDAY
NIGHT AS THE LATEST ECMWF DOES HAVE SOME VERY LIGHT QPF. NOT
SURE...BUT DID ADD A 20 POP FOR THIS REGION SATURDAY NIGHT WHEN
LAPSE RATES ARE THE STEEPEST FOR A PASSING SPRINKLE/LIGHT RAIN
SHOWER. CERTAINLY NOT A BIG DEAL THOUGH. EXPECT HIGH TEMPERATURES
TO ONLY RECOVER INTO THE LOW TO MID 50S FOR SATURDAY. THESE
TEMPERATURES ARE ABOUT 5 TO 10 DEGREES BELOW NORMAL FOR THIS TIME OF
YEAR.
QUITE A CHILLY NIGHT IS IN STORE FOR SOUTHERN NEW ENGLAND SATURDAY
NIGHT. LARGE HIGH PRESSURE BUILDING INTO THE REGION AND MOSTLY
CLEAR SKIES WILL PROVIDE FOR AN IDEAL NIGHT OF RADIATIONAL COOLING.
THE EXCEPTION WILL BE FOR PORTIONS OF THE CAPE/NANTUCKET WHERE OCEAN
EFFECT CLOUDS WILL AFFECT THE REGION. LOWS SHOULD RANGE FROM THE
MID 20S ACROSS SOUTHWEST NH/NORTHWEST MA...TO MAINLY WELL DOWN INTO
THE 30S ELSEWHERE. EVEN DOWNTOWN BOSTON SHOULD SEE THE MERCURY FALL
TO AROUND 40.
SUNDAY AND MONDAY...
HIGH PRESSURE WILL BEGIN TO MOVE OFF THE COAST ON SUNDAY ALLOWING
FOR WARMING MID LEVEL TEMPERATURES. HOWEVER...MIXING WILL NOT BE
GREAT AND WITH A COLD START THE SURFACE WILL TAKE BIT MORE TIME TO
WARM. SKIES SHOULD BE MOSTLY SUNNY ON SUNDAY...BUT WITH HIGHS IN
THE MID TO UPPER 50S. ON MONDAY...WE SHOULD SEE TEMPERATURES
REBOUND INTO THE LOWER TO MID 60S ON THE COASTAL PLAIN AHEAD OF AN
APPROACHING COLD FRONT.
MONDAY NIGHT THROUGH WEDNESDAY...
THE ECMWF/GFS SHOW A STRONG COLD FRONT MOVING THROUGH THE REGION
LATE MONDAY OR TUESDAY. THEY DIFFER A BIT ON THE TIMING WITH THE
GFS ABOUT 6 TO 12 HOURS FASTER. MAINTAINED A 30 POP AS THE FRONT
COULD BE ACCOMPANIED BY A BRIEF BAND OF RAIN SHOWERS LATE MONDAY OR EARLY
TUESDAY. OTHERWISE...A CHILLY AIRMASS WILL BE USHERED BACK INTO THE
REGION ON TUESDAY AND WEDNESDAY WITH HIGHS ONLY IN THE 50S.
&&
.AVIATION /02Z THURSDAY THROUGH MONDAY/...
TONIGHT...BASED ON 18Z SUITE OF MODEL DATA WILL BE MAKING SOME
MODIFICATIONS TO THE AVIATION FORECAST. LOW STRATUS THAT AFFECTED
THE CAPE/ISLANDS LOOKS TO EXPAND FURTHER NORTHWEST TONIGHT ONTO
PORTIONS OF THE COASTAL PLAIN AND POSSIBLY A BIT FURTHER.
THEREFORE...WILL INDICATE MVFR CEILINGS FOR MUCH OF THE COASTAL
SITES OVERNIGHT. IN ADDITION...LOCALIZED IFR CONDITIONS ARE
POSSIBLE PARTICULARLY ON THE CAPE/ISLANDS.
DEVELOPING MVFR IN CLOUDS AND SHOWERS THURSDAY. BRIEF IFR POSSIBLE IN
HEAVIER SHOWERS. CONDITIONS LINGER INTO THE EVENING...ENDING FROM
WEST TO EAST.
CLEARING SKIES LATER THURSDAY NIGHT WITH VFR MOST SPOTS. POSSIBLE IFR
IN PATCHY FOG LATE THURSDAY NIGHT ESPECIALLY IN THE CT VALLEY.
OUTLOOK...FRIDAY THROUGH MONDAY
VFR THE VAST MAJORITY OF THE TIME. THE ONLY EXCEPTIONS ARE SOME
ISOLATED EARLY MORNING FOG PATCHES IN THE TYPICALLY PRONE
LOCATIONS. THERE ALSO MAY BE A PERIOD OF MARGINAL MVFR/VFR OCEAN
EFFECT CLOUDS ON THE OUTER-CAPE/NANTUCKET FRIDAY NIGHT INTO EARLY
SUNDAY.
&&
.MARINE...
WINDS AND SEAS REMAIN BELOW SMALL CRAFT LEVELS TONIGHT AND THURSDAY.
A COLD FRONT MOVES ACROSS THE WATERS THURSDAY EVENING OR EARLY NIGHT.
COLD ADVECTION BEHIND THE FRONT WILL PROMOTE NORTHWEST GUSTS TO 20 OR
25 KNOTS ACROSS THE WATERS...A SMALL CRAFT ADVISORY MAY BE NEEDED AT
THAT TIME.
OUTLOOK...FRIDAY THROUGH MONDAY
FRIDAY AND SATURDAY...
NORTHERLY WINDS WITH GUSTS OF 20 TO 25 KNOTS ARE EXPECTED FOR MUCH
OF THE TIME AS COOL ADVECTION WILL PROVIDE FOR GOOD MIXING. THE
STRONGEST WINDS MAY OCCUR FRIDAY MORNING AND THEN AGAIN LATE
SATURDAY AND SATURDAY NIGHT WITH ANOTHER SURGE OF CHILLY AIR.
SUNDAY AND MONDAY...
WINDS SHOULD DIMINISH ON SUNDAY AS HIGH PRESSURE BUILDS OVER THE REGION.
HOWEVER...GRADIENT WILL INCREASE ON MONDAY AHEAD OF AN APPROACHING
COLD FRONT. THEREFORE...WE MAY SEE SCA SEAS ALONG WITH 25 TO 30
KNOT SOUTHWEST WIND GUSTS DEVELOP.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
MA...NONE.
NH...NONE.
RI...NONE.
MARINE...NONE.
&&
$$
SYNOPSIS...WTB/FRANK
NEAR TERM...WTB/FRANK
SHORT TERM...WTB
LONG TERM...FRANK
AVIATION...KJC
MARINE...WTB/FRANK
