Area Forecast Discussion
Issued by NWS Boston, MA

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FXUS61 KBOX 192349
AFDBOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
749 PM EDT SUN OCT 19 2014

.SYNOPSIS...
GUSTY NORTHWEST WINDS WILL BRING COLDER AIR TO SOUTHERN NEW
ENGLAND TONIGHT. HIGH PRESSURE MOVES OVER THE REGION ON MONDAY. A
DISTURBANCE DROPPING THROUGH THE GREAT LAKES WILL GENERATE A LONG
DURATION COASTAL STORM TUESDAY THROUGH FRIDAY WITH PERIODS OF
HEAVY RAIN. CONDITIONS LOOK TO IMPROVE SLOWLY BY NEXT WEEKEND.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
735 PM UPDATE...
NOTING GUSTY NW WINDS REMAIN IN PLACE ESPECIALLY ALONG THE COAST
AND ACROSS THE CT VALLEY AT 23Z DUE TO LEFTOVER PRES GRADIENT.
HIGH PRES RIDGE REMAINS ACROSS CENTRAL AND WESTERN NY/PA...BUT
SHOULD SHIFT SLOWLY E THROUGH THE REMAINDER OF THE NIGHT. SKIES
ARE BEGINNING TO CLEAR ACROSS CT/W MA AS SEEN ON LATEST IR
SATELLITE TRENDS...THOUGH NOTING LEADING EDGE OF CIRRUS INTRUDING
TOWARD THE RIDGE AXIS TO THE W.

SHOULD SEE THE WINDS DIMINISH AS RIDGE PUSHES SLOWLY E AS WELL AS
SKIES CONTINUING TO CLEAR. MAY SEE SOME CIRRUS WORK IN WITH THE
RIDGE TOWARD DAYBREAK. WHEN UPDATING CURRENT CONDITIONS...NOTING
THAT DEWPTS WERE ABOUT 2-4 DEGS LOWER THAN FORECAST WHERE SKIES
HAD CLEARED. UPDATED THOSE GRIDS THROUGH THE OVERNIGHT TO LOWER
DEWPTS A FEW DEGS. ALSO UPDATED SKY COVER TO BRING CURRENT BASED
ON SATELLITE.

REMAINING GRIDS WERE IN GOOD SHAPE...UPDATED TO BRING CURRENT.
AGREE WITH TEMP TRENDS AS READINGS TO FALL BELOW FREEZING ACROSS
GOOD PORTION OF THE INTERIOR AS SKIES CLEAR AND WINDS DIMINISH.
KEPT FROST AND FREEZE HEADLINES INTACT.

PREVIOUS DISCUSSION...
THE LIGHT WIND AND CLEAR SKIES WILL ALLOW FOR RADIATIONAL COOLING
ESPECIALLY AWAY FROM THE COAST. OBSERVED AFTERNOON DEW POINTS ARE
IN THE 30S WITH 20S UPSTREAM IN ONTARIO AND WESTERN NY. WITH THIS
VALUES ADVECTING OVER NEW ENGLAND...EXPECT PLENTY OF ROOM FOR
TEMPERATURES TO FALL BELOW FREEZING IN INTERIOR SOUTHERN NEW
ENGLAND WHILE COASTAL AREAS FALL INTO THE 30S. EXPECTED VALUES ARE
SIMILAR TO THE PREVIOUS TWO FORECASTS. FREEZE WARNING FOR MUCH OF
SOUTHERN NEW ENGLAND WITH FROST ADVISORY ALONG NARRAGANSETT BAY
AND THE MASS EAST COAST.

MODELS START TO BRING HIGH CLOUDS IN LATE AT NIGHT. WITH
SUFFICIENT THICKNESS...THESE CLOUDS COULD SLOW THE COOLING AND
KEEP SOME OF THE INTERIOR ABOVE FREEZING. BUT WE EXPECT THE
INITIAL CLOUDS TO BE THIN ENOUGH TO HAVE LITTLE EFFECT.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/...
MONDAY...
HIGH PRESSURE CRESTS OVER THE REGION. WINDS WILL SHIFT AROUND TO
SOUTHWEST DURING THE AFTERNOON. EXPECT SOME INCREASE IN MID AND
HIGH CLOUDS BUT OVERALL A FAIR WEATHER DAY. MIXING SHOULD REACH TO
925 MB...POSSIBLY A LITTLE HIGHER. TEMPS EQUIVALENT TO -1C/-3C AT
850 MB...SUPPORTS MAX TEMPS IN THE 50S.

MONDAY NIGHT...
RIDGE MOVES OFF TO THE EAST WHILE A TROUGH DIGS OVER THE GREAT
LAKES. THIS TURNS OUR UPPER FLOW INTO A SOUTHWEST FLOW. WEAK HINTS
IN THE MODEL DATA OF A 70-KNOT JET OVERHEAD OF THE NORTHEAST
USA. THE RIGHT ENTRANCE REGION OF THIS POSSIBLE JET IS LOCATED
SOUTH OF THE REGION SUGGESTING THE BEGINNING OF CYCLOGENESIS ALONG
THE MID ATLANTIC COAST. MEANWHILE THE SOUTHWEST FLOW WILL BE
TRANSPORTING MOISTURE UP THE COAST IN CLOUDS. EXPECT INCREASING
AND THICKENING CLOUDS THROUGH THE NIGHT WITH POTENTIAL FOR
INCREASING LIFT. THE MOISTURE AND LIFT WOULD LEAD TO A CHANCE OF
RAIN LATE AT NIGHT. TEMPS WILL INITIALLY COOL IN THE EVENING WITH
ENOUGH TIME TO DROP 10-15 DEGREES FROM DAYTIME HIGHS. WE USED A
RANGE OF MIN TEMPS IN THE UPPER 30S AND 40S.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
HIGHLIGHTS...

* A LONG DURATION COASTAL STORM WILL IMPACT NEW ENGLAND FROM TUE
  THROUGH AT LEAST THU. PERIODS OF HEAVY RAIN APPEAR TO BE THE
  PRIMARY THREAT. A BRIEF PERIOD OF GUSTY WINDS ARE ALSO POSSIBLE
  TUE NIGHT AND WED ALONG THE IMMEDIATE NE MASS COAST.
* THE LOW LOOKS TO PUSH SLOWLY NE DURING THU...THOUGH INCLEMENT
  WEATHER MAY LINGER INTO FRI AS THE UPPER LOW SLOWLY MOVES AWAY.
* EXPECT GENERALLY DRY WEATHER NEXT WEEKEND...THOUGH MAY SEE A FEW
  SHOWERS LATE SAT NIGHT/SUN AS COLD FRONT PASSES.

OVERVIEW AND MODEL PREFERENCES...

OVERALL 12Z OP MODELS AS WELL AS ENSEMBLE GUIDANCE CONTINUE TO
SIGNAL DEVELOPMENT OF H5 CUTOFF LOW PRES ACROSS NORTHEAST AND MID
ATLC STATES DURING MOST OF THIS TIMEFRAME. BY THE BEGINNING OF
THIS TIMEFRAME...THE UPPER LOW ALREADY TAKING SHAPE OVER THE
APPALACHIANS...PUSHING OFF THE NJ/DELMARVA COASTLINE BY MID WEEK.
QUESTION WILL BE WHERE THE SURFACE FEATURE FORMS AND EVENTUALLY
SETS UP SHOP. ANOTHER ISSUE WILL BE DEVELOPING STRONG E-NE LOW
LEVEL JET AND HOW CLOSE THIS WILL COME TO THE E COAST...OR IF IT
REMAINS N OF THE REGION LATE TUESDAY INTO WEDNESDAY. THE UPPER
SYSTEM AND SURFACE LOW MEANDER THROUGH LATE THU...THEN LOOKS TO
SLOWLY EXIT TO NOVA SCOTIA...THOUGH STILL SOME TIMING ISSUES NOTED
ON OPERATIONAL MODELS. GENERAL SIGNAL ON DETERMINISTIC AND
ENSEMBLE MODELS SIGNALING IMPROVED CONDITIONS BY NEXT WEEKEND.

USED A BLEND OF AVAILABLE GUIDANCE INTO THURSDAY...THEN
TRANSITIONED OVER TO ENSEMBLE GUIDANCE WHERE HIGHER TIMING
UNCERTAINTY STILL IN PLAY.

DAILIES...

TUESDAY...
VIGOROUS H5 SHORT WAVE TROUGH CONTINUES TO DIG AS IT SHIFTS SE
OUT THE EASTERN LAKES EARLY TUE. QUICKLY DEEPENING TROUGH TAKES
SHAPE LATE TUE/TUE NIGHT...WHILE SURFACE LOW STARTS TO FORM TUE
NIGHT SOMEWHERE OFF THE DELMARVA/NJ COAST. AREA OF RAIN CONTINUES
TO DEVELOP AND EXPAND FROM E-W ACROSS THE REGION. NOTING BAND OF
HEAVIER RAINFALL OFFSHORE...BUT QUESTION WILL BE WHETHER SOME OF
THIS WILL WORK INLAND. AT THIS POINT...SHOULD REMAIN OFFSHORE BUT
SOMETHING TO MONITOR. MAY SEE SOME HEAVIER PRECIP MAKE IT INTO NE
MA/S CENTRAL NH OVERNIGHT TUE NIGHT.

QUESTION REMAINS ABOUT STRONGER E-NE WINDS THAT MAY TRY TO WORK
ONSHORE WITH THE STRONG LOW LEVEL JET WORKING AROUND THE DEVELOP
CUTOFF UPPER LOW. AT THIS POINT...STILL LOOKS LIKE THEY WILL HAVE A
TOUGH TIME MIXING DOWN AS LAPSE RATES REMAIN LOW /AROUND 2-3C/KM/
BUT COULD SEE SOME GUSTY WINDS WORK DOWN WITH ANY HEAVIER RAINFALL
TUE NIGHT MAINLY ACROSS NE COASTAL MA.

HIGHS ON TUE WILL MAKE IT TO BETWEEN 60 AND 65 ALONG THE
COAST...BUT ONLY THE MID-UPPER 50S ACROSS THE HIGHER TERRAIN.

TUESDAY NIGHT THROUGH THURSDAY NIGHT...
EXACT TIMING AND STORM IMPACTS REMAIN UNCERTAIN...THOUGH DOES LOOK
LIKE THE MAIN THREAT WILL BE PERIODS OF HEAVY RAINFALL. USING A
BLEND OF AVAILABLE MODEL GUIDANCE...QPF TOTALS FOR THIS TIMEFRAME
LOOK TO BE A BIT LESS THAN PREVIOUS FORECAST...GENERALLY AROUND
1.25 INCHES ON THE S COAST RANGING UP TO 1.75 TO AROUND 2 INCHES
ACROSS NE MA INTO S NH. QPF COULD INCREASE IF HEAVIER RAIN BANDS
MOVE ACROSS...THOUGH. EXPECT STEADY RAIN FROM TUE NIGHT INTO THU
NIGHT...THEN SHOULD BEGIN TO TRANSITION TO SHOWERS ACROSS THE CT
VALLEY AFTER MIDNIGHT THU NIGHT AS THE SURFACE LOW LOOKS TO SLOWLY
HEAD NE WHILE THE UPPER LEVEL SYSTEM LINGERS ACROSS THE REGION.

MODELS CONTINUE TO SIGNAL THE STRONG WIND THREAT TO REMAIN N OF THE
REGION...BUT CAN NOT TOTALLY RULE OUT SOME GUSTS UP TO 25 KT OR SO
ACROSS NE MA INTO S CENTRAL NH DEPENDING UPON POSITION OF JET AXIS
DURING TUE NIGHT INTO WED. SOMETHING TO MONITOR.

WITH STRONGEST E-NE WINDS PUSHING N OF THE REGION...THREAT FOR
COASTAL FLOODING REMAINS LOW. SEAS DO BUILD OFF THE E MA COAST AND
COULD SEND SOME HIGHER SWELLS TOWARD THE SHORE BY WED/THU...AND WILL
CONTINUE TO MONITOR THE LOW LEVEL HIGH WIND AXIS TO SEE IF IT SHIFTS
FURTHER S.  WITH INCREASING SWELLS...RISK CONTINUES FOR COASTAL
BEACH EROSION WITH THE WAVE ACTION OVER SEVERAL HIGH TIDE CYCLES.

FRIDAY...
QUESTION AT THIS POINT IS HOW QUICKLY WILL THE SURFACE LOW DEPART
DURING FRIDAY. MODELS HAVE DIFFERENT TIMING ON THIS...BUT
GENERALLY LOOKS TO PUSH TOWARD NOVA SCOTIA BY LATE FRIDAY.
HOWEVER...COULD STILL SEE SOME LINGERING SHOWERS ON BACK SIDE INTO
FRI NIGHT ACROSS E MA/S CENTRAL NH AS UPPER LEVEL SYSTEM SLOWLY
PUSHES E. AT THIS POINT...SHOULD SEE IMPROVING CONDITIONS
OVERNIGHT FRI.

NEXT WEEKEND...
LOOKS TO BE A DRY SEASONABLE WEEKEND AS NW WINDS AT THE SURFACE
AND ALOFT TAKE OVER. SOME QUESTION AS TO APPROACH OF FAST MOVING
H5 SHORT WAVE AS ASSOCIATED SURFACE COLD FRONT QUICKLY CROSSING
THE REGION SAT NIGHT/EARLY SUN. NOT MUCH MOISTURE AT SURFACE...FOR
NOW...BUT COULD SEE A FEW SHOWERS ACROSS S NH/N MA AS THE FRONT
PASSES.

&&

.AVIATION /00Z MONDAY THROUGH FRIDAY/...
FORECASTER CONFIDENCE LEVELS...

LOW...LESS THAN 30 PERCENT.
MODERATE...30 TO 60 PERCENT.
HIGH...GREATER THAN 60 PERCENT.

SHORT TERM /THROUGH MONDAY/...HIGH CONFIDENCE.

THROUGH MIDNIGHT...LEFTOVER SCT-BKN CLOUDS AT 5-6KFT SHOULD BECOME
SKC. NW WINDS GUSTING TO 20-25 KT ALONG IMMEDIATE E COAST AND
ACROSS THE CT VALLEY...DIMINISHING BY AROUND MIDNIGHT.

REMAINDER OF THE NIGHT...VFR. CLEAR. LIGHT WINDS.

MONDAY...VFR. LIGHT WINDS BACKING TO SW. HIGH THIN CLOUDS MOVE IN
FROM W.

MONDAY NIGHT...VFR MOST OF THE NIGHT. PATCHES OF MVFR CIGS IN
LIGHT RAIN POSSIBLE LATE AT NIGHT.

KBOS...HIGH CONFIDENCE IN TAF.

KBDL...HIGH CONFIDENCE IN TAF.

OUTLOOK...TUESDAY THROUGH FRIDAY...

TUESDAY THROUGH THURSDAY...HIGH CONFIDENCE OVERALL AS CONDITIONS
LOWERING TO MVFR-IFR IN DEVELOPING RAIN DURING TUE...BUT LOW
CONFIDENCE ON EXACT TIMING OF DETAILS. LOW PROB OF E-NE WIND GUSTS
REACHING 20-25 KT ACROSS NE MA COAST TUE NIGHT/WED. CONDITIONS
SHOULD START TO IMPROVE OVER WESTERN AREAS THU NIGHT.

FRIDAY...MODERATE CONFIDENCE. EXPECT CONDITIONS TO IMPROVE TO VFR
ACROSS WESTERN AND CENTRAL AREAS BY MIDDAY. ACROSS E MA/S CENTRAL
NH...MVFR CONDITIONS IN LOW CLOUDS AND SCATTERED LINGERING SHOWERS
MAY CONTINUE INTO FRI NIGHT BEFORE IMPROVING.

&&

.MARINE...
FORECASTER CONFIDENCE LEVELS...

LOW...LESS THAN 30 PERCENT.
MODERATE...30 TO 60 PERCENT.
HIGH...GREATER THAN 60 PERCENT.

SHORT TERM /TODAY THROUGH MONDAY/...HIGH CONFIDENCE.

TONIGHT...
HIGH PRESSURE APPROACHES FROM THE W. EXPECT NORTHWEST WINDS TO
DIMINISH OVERNIGHT WITH GUSTS 15 TO 20 KNOTS AFTER MIDNIGHT.
LINGERING 5 FOOT SEAS ON THE OUTER WATERS...BUT WITH A DIMINISHING
TREND OVERNIGHT. SMALL CRAFT ADVISORY LINGERS THROUGH EARLY
TONIGHT...THEN DIMINISHES TO JUST THE OUTER WATERS LATE AT NIGHT.

MONDAY...
HIGH PRESSURE BUILDS OVER THE WATERS. DIMINISHING NORTHWEST WINDS
BECOME SOUTHWEST IN THE AFTERNOON. SEAS DIMINISH BELOW 5 FEET
DURING THE MORNING.

MONDAY NIGHT...
HIGH PRESSURE MOVES OFFSHORE. WINDS TURN SOUTHWEST BUT REMAIN
BELOW SMALL CRAFT THRESHOLDS. SEAS BUILD A LITTLE BUT REMAIN BELOW
5 FEET. LIGHT RAIN MOVES UP FROM THE MID ATLANTIC COAST LATE AT
NIGHT.

OUTLOOK...TUESDAY THROUGH FRIDAY...

TUESDAY...HIGH CONFIDENCE.
EXPECT SOUTHERLY WINDS TO GRADUALLY BACK AROUND TO E-SE BY
TUESDAY EVENING. WINDS AND SEAS WILL REMAIN BELOW SMALL CRAFT
CRITERIA.

TUESDAY NIGHT THROUGH WEDNESDAY NIGHT...MODERATE CONFIDENCE.
EXPECT E-NE WIND GUSTS TO AROUND 25 KT MAINLY ACROSS THE EASTERN
OUTER WATERS N OF BOSTON TO CAPE ANN. LOW PROB OF GUSTS TO 30 KT
OR EVEN TO GALE FORCE LATE THU NIGHT AND WED. SEAS WILL BUILD ON
THE EASTERN OPEN WATERS TO 5-8 FT BY EARLY WED...WITH THE HIGHEST
SEAS ON THE FAR OUTER WATERS...THEN UP TO 5 FT ON THE SOUTHERN
OUTER WATERS WED. WINDS SHOULD BEGIN TO DIMINISH WED NIGHT THOUGH
SEAS WILL REMAIN AOA 5 FT. PERIODS OF HEAVY RAIN AND PATCHY FOG
WILL REDUCE VSBY.

THURSDAY AND FRIDAY...MODERATE CONFIDENCE.
WINDS SHIFT TO N-NW ON THU BUT REMAIN BELOW SMALL CRAFT CRITERIA.
MAY SEE WIND GUSTS UP TO 20 KT DURING FRI. SEAS REMAIN HIGH
ESPECIALLY ON THE EASTERN OPEN WATERS...BUT SHOULD SUBSIDE THU
NIGHT AND FRI.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...FREEZE WARNING FROM MIDNIGHT TONIGHT TO 9 AM EDT MONDAY FOR
     CTZ002>004.
MA...FROST ADVISORY FROM MIDNIGHT TONIGHT TO 9 AM EDT MONDAY FOR
     MAZ007-015-016-019-022-023.
     FREEZE WARNING FROM MIDNIGHT TONIGHT TO 9 AM EDT MONDAY FOR
     MAZ005-006-009>014-017-018-020-021.
NH...NONE.
RI...FROST ADVISORY FROM MIDNIGHT TONIGHT TO 9 AM EDT MONDAY FOR
     RIZ002-004-005-007.
     FREEZE WARNING FROM MIDNIGHT TONIGHT TO 9 AM EDT MONDAY FOR
     RIZ001-003-006.
MARINE...SMALL CRAFT ADVISORY UNTIL 2 AM EDT MONDAY FOR ANZ231>234-251.
     SMALL CRAFT ADVISORY UNTIL 11 PM EDT THIS EVENING FOR ANZ230-
     235>237.
     SMALL CRAFT ADVISORY UNTIL 11 AM EDT MONDAY FOR ANZ250-254.
     SMALL CRAFT ADVISORY UNTIL 8 AM EDT MONDAY FOR ANZ255.
     SMALL CRAFT ADVISORY UNTIL 4 AM EDT MONDAY FOR ANZ256.

&&

$$
SYNOPSIS...WTB/EVT
NEAR TERM...WTB/EVT
SHORT TERM...WTB
LONG TERM...EVT
AVIATION...WTB/EVT
MARINE...WTB/EVT


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