006
FXUS61 KBOX 211950
AFDBOX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOSTON/NORTON MA
350 PM EDT SAT SEP 21 2019
SYNOPSIS
HIGH PRESSURE REMAINS IN CONTROL INTO MONDAY WITH SUMMER-LIKE
TEMPERATURES AND DRY WEATHER. A COLD FRONT WILL BRING A PERIOD OF
SHOWERS LATE MONDAY, MONDAY NIGHT INTO TUE FOLLOWED BY COOLER, BUT
SEASONABLY WEATHER THROUGH THE REST OF NEXT WEEK.
NEAR TERM /UNTIL 6 AM SUNDAY MORNING/
350 PM UPDATE ...
ANOMALOUS (588 DAM) DEEP LAYER RIDGE OVER THE NORTHEAST LATE THIS
AFTERNOON PROVIDING WARM BUT PLEASANT CONDITIONS WITH 3 PM TEMPS 80-
85 INLAND, 75-80 ELSEWHERE. DEW PTS 55-60 SO HUMIDITY FAIRLY
COMFORTABLE. GIVEN THIS DEEP LAYER RIDGE MOVES ACROSS THE AREA
TONIGHT DRY WEATHER WILL CONTINUE. 1025 MB SURFACE HIGH OFF THE MID
ATLC COAST BUT WITH PRESSURE GRADIENT WEAK ACROSS SOUTHERN NEW
ENGLAND EXPECTING MOST LOCATIONS TO DECOUPLE. THUS LIGHT WINDS,
CLEAR SKIES AND DEW PTS IN THE 50S WILL SUPPORT LOWS LATE TONIGHT IN
THE 50S AS WELL. THEREFORE SIDED WITH THE COOLER MOS GUIDANCE
FOR MIN TEMPS. PATCHY RADIATIONAL FOG INLAND EXPECTED.
ONLY WEATHER CONCERN LATE TODAY IS LEFTOVER ESE SWELLS OF AROUND 4
FT WITH A PERIOD OF EVERY 11 SECONDS CONTINUES ACROSS THE MA WATERS.
THUS ELEVATED RISK OF STRONG RIPS WITH MODEST SURF ACROSS OCEAN
FACING BEACHES UNTIL SUNSET.
SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/
350 PM UPDATE ...
SUNDAY ...
EVEN WARMER THAN TODAY AWAY FROM THE SOUTH COAST WITH 925 MB TEMPS
PUSHING +21C ACROSS NORTHERN MA, THAT'S UP FROM +19C THIS AFTERNOON.
THUS MID 80S TO PERHAPS UPPER 80S SHOULD BE COMMON ACROSS THE
MERRIMACK VALLEY OF NORTHEAST MA INTO BOSTON AS SW PRESSURE GRADIENT
SHOULD BE SUFFICIENT IN THE AFTERNOON TO PRECLUDE SEABREEZE
DEVELOPMENT. LOW 80S ELSEWHERE EXCEPT 70S ALONG THE SOUTH COAST. IT
WILL FEEL WARMER TOMORROW THAN TODAY AS DEW PTS CLIMB INTO THE 60S
ESPECIALLY SOUTH COAST. IN FACT SOUTH COAST BEACHGOERS MAY
EXPERIENCE SOME STRATUS AND FOG THRU THE DAY AS THIS HIGHER DEW PT
SURGES NORTHWARD. PLYMOUTH COUNTY NORTHWARD SHOULD BE STRATUS/FOG
FREE GIVEN MORE SW LAND TRAJECTORY.
IT WILL BECOME BREEZY LATE IN THE DAY WITH SSW WINDS UP TO 20 MPH.
UPPER LEVEL CLOSED LOW CURRENTLY OVER LAKE ONTARIO THIS AFTERNOON
ONLY GENERATING SOME SHALLOW CU/SCU GIVEN ATMOSPHERE IS DRY LOW TO
MID LEVELS. EXPECT THE SAME OUTCOME AS THIS FEATURE MOVES ACROSS
SOUTHERN NEW ENGLAND SUNDAY. THUS NO SENSIBLE WEATHER IMPACTS.
SUNDAY NIGHT ...
WARM NIGHT AHEAD OF LOW LEVEL WAA INCREASES WITH APPROACHING FRONT
YIELDING TIGHTENING SW PRESSURE GRADIENT. GIVEN DEW PTS IN THE 60S
EXPECT LOWS TO BE IN THE 60S AS WELL ALONG WITH PATCHY FOG WITH DEW
PTS HIGHER THAN AVG NIGHTTIME LOW. THIS WILL SERVE FOR A VERY WARM
START TO THE DAY MONDAY. GIVEN SW GRADIENT BREEZY CONDITIONS ALONG
THE COAST, CAPE COD, ISLANDS AND HIGH TERRAIN.
LONG TERM /MONDAY THROUGH SATURDAY/
*/ HIGHLIGHTS...
- RAIN ANTICIPATED LATE MONDAY INTO MONDAY NIGHT
- THEREAFTER MILD DAYS, COOL NIGHTS, DRY THE REMAINDER OF THE WEEK
- TEMPERATURES RUNNING ABOVE AVERAGE THROUGHOUT
*/ OVERVIEW...
AMPLIFYING PATTERN. IMPRESSIVE N PACIFIC JET SIGNALED BY A +WPO/+EPO
THAT CASCADES ENERGY AND MILD AIR OVER THE CONUS INITIALLY. KICKING
DOWNSHEARED ENERGY ACROSS THE 4-CORNERS REGION, A CLOSING MID-LEVEL
LOW LATCHED ONTO CONTINENTAL MOISTURE, THERE'S A CHANCE FOR RAINFALL
AROUND MONDAY NIGHT DISCUSSED IN MORE DETAIL BELOW. HOWEVER BY LATE
SEPTEMBER A PATTERN-AMPLIFICATION EMERGES. ONE-TWO PUNCH, NW PACIFIC
TAPAH BECOMING POST-TROPICAL, INGESTED INTO THE BERING STRAIGHT LOW,
SUBSEQUENT LATENT HEAT RELEASE AMPLIFIES THE LONGWAVE TROF THAT RE-
CAPTURES EARLIER CUT-OFF N PACIFIC ENERGY. HEIGHTENED AK RIDGE THAT
ULTIMATELY DOWNSHEARS A DEEP TROF ACROSS THE W CONUS INTO THE END OF
SEPTEMBER, PNA BECOMES LARGELY NEGATIVE AS DOES THE EPO/WPO. WITH A
CONTINUED ACTIVE N ATLANTIC TROPICS EMPHASIZED BY THE PHASE 1 MJO,
AN IMPRESSIVE HEAT PUMP AND ANOMALOUSLY HIGHER HEIGHTS EMERGE OVER
THE E CONUS. NO SURPRISE TO SEE ABOVE AVERAGE TEMPERATURE TRENDS AND
BELOW AVERAGE PRECIPITATION PER CPC. HOWEVER ALONG THE NE-PERIPHERY
OF THE HEAT-BUBBLE NO-TROUBLE, THERE ARE OPPORTUNITIES FOR COOLER
AIR AND RAINFALL CHANCES ALONG SE-SWEEPING COLD FRONT BOUNDARIES. SO
NOT ENTIRELY CONVINCED WE'LL SEE THE BRUNT OF THE HEAT EXPECTED FOR
THE SE CONUS N INTO THE MID-ATLANTIC. PERHAPS JUST ON THE CUSP YET
HOWEVER FOR LATE SEPTEMBER IS STILL ABOVE AVERAGE WHEN HIGHS ARE
NORMALLY AROUND 70 AND LOWS NORMALLY AROUND 50. A PATTERN OF MILD
DAYS AND COOL NIGHTS, SOME SHOTS OF WET-WEATHER IN-BETWEEN. BREAK
DOWN THE DETAILS BELOW.
*/ DISCUSSION...
MONDAY INTO MONDAY NIGHT...
WIDESPREAD SHOWERS AND APPRECIABLE RAINFALL REMAINS POSSIBLE. LEAN
TOWARDS WETTER SOLUTIONS GIVEN CONSENSUS FORECAST MID-LEVEL CLOSED-
LOW SOLUTION ACTING ON A NARROW-RIBBON OF CONTINENTAL MOISTURE. MUCH
OF THE SAME, PRECIPITABLE WATERS UP AROUND 1.75-INCHES, WARM-CLOUD
LAYER UP AROUND 12 KFT PRECEDING THE SWEEPING COLD FRONT. A MOIST-
ADIABATIC, CONDITIONALLY-UNSTABLE PROFILE, ALBEIT BRIEF AND RIGHT
ALONG THE FRONT, EXPECTED LIFT, LOW-LEVEL CONVERGENT FORCING, AND
SYNOPTIC ASCENT BENEATH CYCLONIC FLOW AND DIFFLUENCE ALOFT MAKES A
CASE OF DECENT UPWARD MOTIONS THAT SHOULD PROMOTE COLLISION AS WELL
AS COALESCENCE SUCH THAT DECENT RAINS SHOULD DEVELOP. POSITIVE TO A
NEUTRAL TILT TROF WITH MODEST W/SW SHEAR PRECEDING, INSTABILITY IS
IN QUESTION GIVEN MARGINAL, MOIST-ADIABATIC LAPSE RATES. RUMBLES OF
THUNDER NOT RULED OUT, NOR HEAVIER DOWNPOURS. CHANCE TO LIKELY POPS.
THERE'S INCREASING SIGNAL OF THE POSSIBILITY OF SIGNIFICANT RAINFALL
WITH AMOUNTS AROUND 0.50 INCHES.
REST OF THE WEEK...
RAIN CHANCES AROUND THURSDAY NIGHT APPEAR SUPPRESSED BY THE WEIGHT
OF INCREASING HEIGHTS ACROSS THE E CONUS. HOWEVER WITH THE PRIOR
MENTIONED AMPLIFIED PATTERN TIGHTENING OVER THE W AND CENTRAL CONUS
THAT NEW ENGLAND FINDS ITSELF BENEATH NW FLOW ALOFT, THE OPPORTUNITY
FOR SOME SLIGHTLY COOLER AIR AND RAINFALL CHANCES ALONG SE SWEEPING
COLD FRONTS OVER THE WEEKEND INTO EARLY NEXT WEEK. HOWEVER OVERALL
TEMPERATURES STILL LOOK TO RUN ABOVE AVERAGE.
AVIATION /20Z SATURDAY THROUGH THURSDAY/
FORECASTER CONFIDENCE LEVELS...
LOW - LESS THAN 30 PERCENT.
MODERATE - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
SHORT TERM /THROUGH SUNDAY NIGHT/...HIGH CONFIDENCE.
18Z UPDATE (NO MAJOR CHANGES)...
THRU 00Z ... VFR, DRY WEATHER AND LIGHT WINDS WITH SEABREEZES
AT THE COAST
AFTER 00Z ... VFR, DRY WEATHER AND LIGHT WINDS. ISOLATED
MVFR/IFR INLAND DUE TO PATCHY FOG.
SUNDAY ... VFR AND DRY WEATHER. COULD BE SOME PATCHY FOG/IFR-
MVFR ALONG THE SOUTH COAST AT TIMES. LIGHT/VARIABLE WIND IN THE
MORNING BECOMING SSW AND INCREASING 15-20 KT.
SUNDAY NIGHT ... VFR AND DRY WEATHER. HOWEVER PATCHY IFR/MVFR IN
FOG MAY LINGER AT TIMES ALONG THE SOUTH COAST. MODEST SSW WINDS
CONTINUE WITH STRONGEST WINDS ALONG THE SOUTH COAST AND ISLANDS.
KBOS TERMINAL...HIGH CONFIDENCE IN TAF.
KBDL TERMINAL...HIGH CONFIDENCE IN TAF.
OUTLOOK /MONDAY THROUGH THURSDAY/...
MONDAY: VFR. BREEZY. CHANCE SHRA.
MONDAY NIGHT: VFR. BREEZY. SHRA LIKELY, SLIGHT CHANCE TSRA.
TUESDAY: VFR. SLIGHT CHANCE SHRA.
TUESDAY NIGHT THROUGH WEDNESDAY: VFR.
MARINE
FORECASTER CONFIDENCE LEVELS...
LOW - LESS THAN 30 PERCENT.
MODERATE - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
SHORT TERM /THROUGH SUNDAY NIGHT/...HIGH CONFIDENCE.
345 PM UPDATE ...
EASTERLY SWELLS FROM HUMBERTO HAVE NOW DIMINISHED TO 3 TO 4 FT. THUS
HAVE DROPPED THE SCA. OTHERWISE LIGHT WINDS TONIGHT INTO SUNDAY
MORNING THEN SSW WINDS INCREASE TO 15-20 KT SUNDAY AFTERNOON AND
EVENING WITH GUSTS UP TO 25 KT POSSIBLE TOWARD SUNRISE MONDAY.
PATCHY FOG AND LOW CLOUDS MAY LIMIT VSBY SUNDAY AFTERNOON THRU
SUNDAY NIGHT. DRY WEATHER PREVAILS.
OUTLOOK /MONDAY THROUGH THURSDAY/...MODERATE CONFIDENCE.
SUNDAY NIGHT: LOW RISK FOR SMALL CRAFT ADVISORY WINDS WITH
GUSTS UP TO 25 KT. AREAS OF SEAS APPROACHING 5 FT.
MONDAY: MODERATE RISK FOR SMALL CRAFT ADVISORY WINDS WITH GUSTS
UP TO 25 KT. AREAS OF ROUGH SEAS. CHANCE OF RAIN SHOWERS.
MONDAY NIGHT: LOW RISK FOR SMALL CRAFT ADVISORY WINDS WITH
GUSTS UP TO 25 KT. AREAS OF ROUGH SEAS. RAIN SHOWERS LIKELY,
SLIGHT CHANCE OF THUNDERSTORMS.
TUESDAY: WINDS LESS THAN 25 KT. AREAS OF SEAS APPROACHING 5 FT.
CHANCE OF RAIN SHOWERS.
TUESDAY NIGHT: WINDS LESS THAN 25 KT. AREAS OF SEAS APPROACHING
5 FT.
WEDNESDAY: WINDS LESS THAN 25 KT. SEAS UP TO 5 FT.
BOX WATCHES/WARNINGS/ADVISORIES
CT...NONE.
MA...HIGH RIP CURRENT RISK UNTIL 8 PM EDT THIS EVENING FOR MAZ022-
024.
RI...NONE.
MARINE...NONE.
SYNOPSIS...NOCERA
NEAR TERM...NOCERA
SHORT TERM...NOCERA
LONG TERM...SIPPRELL
AVIATION...NOCERA/SIPPRELL
MARINE...NOCERA/SIPPRELL
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