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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