446
FXUS61 KBOX 190154
AFDBOX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOSTON/NORTON MA
954 PM EDT MON MAR 18 2019
SYNOPSIS
HIGH PRESSURE WILL BRING DRY AND COOL WEATHER WITH MODERATING
TEMPERATURES BY WEDNESDAY AFTERNOON. A COASTAL STORM IMPACTS THE
REGION THURSDAY INTO FRIDAY MORNING WITH A PERIOD OF HEAVY RAIN
AND STRONG WINDS. A SHOT OF COLD AIR BEHIND THE DEPARTING STORM
INTO SATURDAY, THEN MORE SEASONABLE CONDITIONS RETURN SUNDAY.
NEAR TERM /UNTIL 6 AM TUESDAY MORNING/
10 PM UPDATE ...
SNOW SHOWERS PREVIOUSLY OVER EASTERN NY HAVE WEAKENED UPON
ENTERING WESTERN MA WITH DEW PT DEPRESSIONS ON THE ORDER OF
20-25 DEGS. 00Z OBSERVED SOUNDING FROM ALY CONFIRMS LOTS OF DRY
AIR BELOW 850 MB. THUS THIS WILL BE THE THEME OVERNIGHT WITH
JUST SOME PATCHY CLOUDS FROM TIME TO TIME WITH PERHAPS A FEW
FLURRIES OVER WESTERN MA INTO NORTHERN CT. PREVIOUS FORECAST
CAPTURES THIS WELL SO NO MAJOR CHANGES.
ONLY MODIFICATION TO THE FORECAST WAS TO LOWER MINS OVERNIGHT AS
MANY LOCATIONS REPORTING LIGHT TO CALM WINDS. THIS COUPLED WITH
A VERY DRY AIRMASS (DEW PTS IN THE SINGLE DIGITS AND TEENS ALONG
WITH PWATS DOWN TO 0.2 INCHES) AND MAINLY CLEAR SKIES,
RADIATIONAL COOLING WILL SUPPORT LOWS IN THE 20S REGION-WIDE
OVERNIGHT.
SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/
EXPECT A PERIOD OF MOSTLY SUNNY SKIES TUESDAY BETWEEN SHORTWAVES.
COLD POOL ALOFT LINGERS THE FIRST PART OF THE DAY, SO DAYTIME
HEATING SHOULD MIX DEEPLY IN THE ATMOSPHERE, LIKELY AT OR ABOVE
800 MB. THIS SHOULD AGAIN SUPPORT MAX SFC TEMPS IN THE UPPER 30S
TO MID 40S.
SECOND SHORTWAVE SWEEPS THROUGH ON TUESDAY NIGHT. A SECOND PERIOD
OF CLOUDS IS POSSIBLE AT THIS TIME, BUT MOISTURE VALUES LOOK DRIER
THAN TONIGHT SO PROBABLY FEWER CLOUDS. DEW POINTS IN THE TEENS WITH
LIGHT WINDS, BUT CLOUDS MAY INTERFERE WITH RADIATIONAL COOLING.
WE WILL GO WITH MIN TEMPS IN THE 20S.
LONG TERM /WEDNESDAY THROUGH MONDAY/
*/ HIGHLIGHTS ...
- MILD WEDNESDAY
- POTENTIAL COASTAL STORM THURSDAY, WATCHING TIDES
- BREEZY FRIDAY, TURNING COLDER INTO SATURDAY
*/ OVERVIEW ...
SEE-SAW PATTERN. SEEMINGLY +EPO WITH NE PACIFIC LOW PRESSURE THAT
AIDS IN MAINTAINING A +PNA OVER WESTERN N AMERICA, PACIFIC / ARCTIC
ENERGY DOWNSHEARED W OF A BAFFIN BAY TROPOSPHERIC POLAR VORTEX INTO
PREFERRED H5 TROUGHING S INTO THE E CONUS. AN OCCASIONAL CYCLONIC
WAVE BREAK OVER THE W CONUS ADDING TO FORECAST CHALLENGES, LOOKING
AT A LATE-WEEK POTENT COASTAL STORM SYSTEM TAPPING INTO SUB-TROPICAL
ENERGY AND MOISTURE WHICH FORECAST MODEL CONSENSUS HAS CONTINUALLY
STRENGTHENED THE LAST SEVERAL RUNS. BRIEF AND JUXTAPOSED BY CENTRAL
CONUS STORMINESS / LATENT HEAT RELEASE E AS THE N ATLANTIC IS WIDE
OPEN. AIRMASS SWINGS COMMUNICATED IN METEOGRAMS, YET TEMPERATURES
HOLD NEAR-SEASONABLE WITH HIGHS AROUND THE MID TO UPPER 40S. TOUCH
ON DETAILS BELOW.
*/ DETAILS ...
WEDNESDAY ...
MILD. RETURN S AIR, BREEZY, DRY. EXPECT HIGHS UP AROUND 50 AS THE
BOUNDARY-LAYER MIXES OUT AS AN INVERTED-V PROFILE. LOW DEWPOINTS.
INCREASING CLOUDS LATE OUT OF THE SW.
THURSDAY ...
POTENTIAL COASTAL STORM. FORECAST GUIDANCE CONSENSUS CONTINUES TO
STEP UP THE POTENCY OF N-STREAM ENERGY DIVING S THROUGH PREFERRED H5
TROUGHING INTO THE SUB-TROPICS PULLING BACK N BENEATH LOWER HEIGHTS.
MORE FAVORABLE BAROCLINICITY BENEATH STRONGER DYNAMICS / ASCENT, COLD
AIR SEEMINGLY ERODED THE PREVIOUS DAY, LOOKING AT MOSTLY RAIN WITH
POTENTIAL POCKETS OF MODERATE TO HEAVY, PERHAPS A RUMBLE OF THUNDER
AS WELL. BUT NUDGING W HIGH PRESSURE RIDGE AND A WIDE-OPEN ATLANTIC,
NOT GOING WITH LIKELY POPS JUST YET, KEEP IT AT CHANCE. UNCERTAINTY
AS TO WHETHER WE CAN OVER-ACHIEVE ON TEMPERATURES / DEWPOINTS. ALSO
WATCHING WINDS AS TIDES WILL BE ASTRONOMICALLY HIGH (BOSTON ONLY
A FOOT SHY OF MINOR FLOODING). AS TO THE 18.12Z EC, NEAR RECORD WITH
RESPECT TO LOWEST SURFACE PRESSURES FOR MID-MARCH, IT IS SOMEWHAT
SUSPICIOUS BUT NOT IGNORING IT. IF FUTURE MODEL CONSISTENCY, THEN
CONCERN WITH RESPECT TO TIDES AND / OR POTENTIALLY MANIFESTATION
OF COLDER AIR YIELDING WET SNOW ON THE BACKSIDE OF THE STORM. WAIT
AND SEE.
FRIDAY ...
BLUSTERY AND TURNING COLDER, IF THE COASTAL STORM MANIFESTS AND ALSO
STRENGTHENS E. SCATTERED SHOWER ACTIVITY LINGERING. H85 TEMPERATURES
DROPPING TO AROUND -10 TO -12C SUNDAY MORNING. MILD FRIDAY, BUT LOWS
FRIDAY NIGHT COULD BE BACK DOWN INTO THE TEENS. MIXING UP AROUND H8
POSSIBLE, MIX-DOWN FASTER WINDS, DRIER AIR, 25 TO 35 MPH GUSTS WITH
GALES OVER THE WATERS, POSSIBLY STRONGER IF THE PRESSURE / THERMAL
GRADIENT STRENGTHENS ON THE BACKSIDE OF THE DEPARTING SYSTEM.
WEEKEND ...
SHOWERY WEATHER MAY LINGER EARLY ON. OVERALL, EXPECTING MOSTLY DRY
CONDITIONS WITH NEAR-SEASONABLE TEMPERATURES AS NW WINDS PREVAIL. A
MIX OF SUN AND CLOUDS BENEATH INCREASING HIGH PRESSURE.
EARLY NEXT WEEK ...
SQUEEZE PLAY. N-STREAM ENERGY CONTINUES TO DIP ALONG THE FLAT-BASE
OF THE PREFERRED H5 TROF AS CUT-OFF ENERGY FROM THE CENTRAL PLAINS
BEGINS TO EXIT E. JUXTAPOSITION OF AIRMASSES, A LOW CONFIDENCE
FORECAST.
AVIATION /02Z TUESDAY THROUGH SATURDAY/
FORECASTER CONFIDENCE LEVELS...
LOW - LESS THAN 30 PERCENT.
MODERATE - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
SHORT TERM /THROUGH TUESDAY NIGHT/...HIGH CONFIDENCE.
10 PM UPDATE ...
NO CHANGES FROM PREVIOUS TAFS...VFR, LIGHT WINDS AND A FEW
FLURRIES ACROSS WESTERN MA/CT. PREVIOUS DISCUSSION BELOW.
==================================================================
VFR. SCT-BKN050. A FEW FLURRIES POSSIBLE. DAYTIME W WINDS 10 KTS
WITH GUSTS UP TO 20 KTS, OTHERWISE AROUND 5 TO 10 KTS.
KBOS TERMINAL...HIGH CONFIDENCE IN TAF.
KBDL TERMINAL...HIGH CONFIDENCE IN TAF.
OUTLOOK /WEDNESDAY THROUGH SATURDAY/...
WEDNESDAY: VFR.
WEDNESDAY NIGHT: VFR. BREEZY. SLIGHT CHANCE SN, SLIGHT CHANCE
SHSN.
THURSDAY: MAINLY VFR, WITH LOCAL MVFR POSSIBLE. BREEZY. CHANCE
RA.
THURSDAY NIGHT: VFR. BREEZY. CHANCE RA, CHANCE SN.
FRIDAY: VFR. BREEZY. SLIGHT CHANCE SHRA.
FRIDAY NIGHT THROUGH SATURDAY: VFR. WINDY WITH GUSTS UP TO
35 KT.
MARINE
FORECASTER CONFIDENCE LEVELS...
LOW - LESS THAN 30 PERCENT.
MODERATE - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
SHORT TERM /THROUGH TUESDAY NIGHT/...HIGH CONFIDENCE.
BIT BREEZY ALONG THE NEAR-SHORE PRESENTLY WITH GUSTS UP AROUND
20 KTS WILL PERSIST FOR THE EVENING HOURS BEFORE DIMINISHING. A
LULL INTO TUESDAY MORNING, EXPECT BREEZY NW WINDS TO RE-EMERGE
WITH AROUND 10 TO 15 KTS, GUSTS UP TO 20 KNOTS. SEAS GENERALLY 1
TO 2 FEET.
OUTLOOK /WEDNESDAY THROUGH SATURDAY/...
WEDNESDAY: WINDS LESS THAN 25 KT.
WEDNESDAY NIGHT: WINDS LESS THAN 25 KT. SEAS LOCALLY
APPROACHING 5 FT. SLIGHT CHANCE OF RAIN.
THURSDAY: LOW RISK FOR SMALL CRAFT ADVISORY WINDS WITH GUSTS UP
TO 25 KT. SEAS UP TO 5 FT. CHANCE OF RAIN.
THURSDAY NIGHT: WINDS LESS THAN 25 KT. SEAS UP TO 5 FT. CHANCE
OF RAIN, CHANCE OF RAIN SHOWERS.
FRIDAY: LOW RISK FOR SMALL CRAFT ADVISORY WINDS WITH GUSTS UP
TO 25 KT. LOCAL ROUGH SEAS. CHANCE OF RAIN SHOWERS.
FRIDAY NIGHT: LOW RISK FOR GALE FORCE WINDS WITH GUSTS UP TO
35 KT. AREAS OF ROUGH SEAS. SLIGHT CHANCE OF RAIN SHOWERS.
SATURDAY: MODERATE RISK FOR GALE FORCE WINDS WITH GUSTS UP TO
35 KT. AREAS OF ROUGH SEAS.
CLIMATE
IN JUST THREE WEEKS, 70 DEGREES WILL CHANGE FROM NEAR RECORD TO
NO SURPRISE, AND IN ANOTHER 1 1/2 MONTHS JUST A PART OF THE
LANDSCAPE.
AVERAGE FIRST OCARINAS OF 70 DEGREE HIGH TEMPERATURES (SINCE
RECORDS BEGAN AS EARLY AS 1872)
BOSTON.......APRIL 8TH
HARTFORD.....APRIL 1
PROVIDENCE...APRIL 8TH
WORCESTER....APRIL 11TH
AVERAGE FIRST OCARINAS OF 70 DEGREE DAILY AVERAGE TEMPERATURES
DAILY AVERAGE TEMPERATURES = (HIGH + LOW) / 2 (SINCE RECORDS
BEGAN AS EARLY AS 1872)
BOSTON.......MAY 27TH
HARTFORD.....MAY 10TH
PROVIDENCE...MAY 20TH
WORCESTER....MAY 29TH
BOX WATCHES/WARNINGS/ADVISORIES
CT...NONE.
MA...NONE.
RI...NONE.
MARINE...NONE.
SYNOPSIS...WTB/SIPPRELL
NEAR TERM...WTB/NOCERA/SIPPRELL
SHORT TERM...WTB
LONG TERM...SIPPRELL
AVIATION...WTB/NOCERA/SIPPRELL
MARINE...WTB/SIPPRELL
CLIMATE...
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