092  
FXUS61 KBOX 172053  
AFDBOX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE BOSTON/NORTON MA  
353 PM EST MON FEB 17 2020  
   
SYNOPSIS
 
 
LOW PRESSURE OVER THE GREAT LAKES TUESDAY AND ITS ATTENDING  
WARM FRONT WILL SPREAD RAIN ACROSS SOUTHERN NEW ENGLAND. THE  
EXCEPTION WILL BE FOR A FEW HOURS OF A WINTRY MIX IN THE  
AFTERNOON ACROSS THE HIGH TERRAIN OF WESTERN AND CENTRAL  
MASSACHUSETTS. THE ATTENDING COLD FRONT SWEEPS ACROSS THE REGION  
TUESDAY NIGHT USHERING IN DRIER AND COLDER WEATHER WEDNESDAY  
WITH THE CORE OF THE COLD AIR SETTLING OVER THE AREA THURSDAY  
NIGHT INTO FRIDAY. MODERATING TEMPERATURES OVER THE WEEKEND  
ALONG WITH DRY WEATHER AS HIGH PRESSURE SETS UP OVER THE MID  
ATLANTIC REGION.  
 

 
   
NEAR TERM /UNTIL 6 AM TUESDAY MORNING/
 
 
THE MAIN STORY TONIGHT WILL BE THE LOCATION AND STRENGTH OF A  
HIGH PRESSURE MOVING EAST ACROSS NORTHERN NEW ENGLAND. THE  
QUESTION IS HOW CLOSELY THE CORE OF THIS SYSTEM WILL PASS TO OUR  
REGION, AS THAT WILL IMPACT THE WINDS, WHICH IN TURN WILL IMPACT  
RADIATIONAL COOLING. OUR PRECIPITATION TYPES LATER TUESDAY WILL  
LARGELY DEPEND UPON HOW COLD THE SURFACE LAYER CAN GET.  
 
NEAR TO SLIGHTLY BELOW NORMAL TEMPERATURES EXPECTED, WITH WINDS  
BECOMING LIGHT AND VARIABLE. MAINLY DRY WEATHER EXPECTED AS  
THERE WILL BE A LOT OF DRY AIR NEAR THE GROUND TO BE OVERCOME,  
FIRST.  
 

 
   
SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/
 
 
NO MAJOR CHANGES TO THE FORECAST FOR TUESDAY. STILL EXPECTING  
A PRIMARY LOW PRESSURE TO PASS BY WELL TO OUR NORTH. 17/12Z  
GUIDANCE STILL SHOWED A WEAK SECONDARY LOW PRESSURE TRYING TO  
GET ORGANIZED TOWARDS THE SOUTH COAST OF NEW ENGLAND TUESDAY  
EVENING. IT LOOKS LIKE A CASE OF TOO LITTLE, TOO LATE, IF YOU  
ARE A SNOW-LOVER. EXPECTING WARMER AIR TO OVERSPREAD OUR REGION  
DURING TUESDAY, EVENTUALLY CHANGING ALL PRECIPITATION OVER TO  
RAIN.  
 
SOME OF THE HIGHER RESOLUTION GUIDANCE, PARTICULARLY THE 3 KM  
NAM, HOLDS ONTO SOME LOW LEVEL COLD AIR A LITTLE LONGER ACROSS  
THE HIGHER TERRAIN OF CENTRAL AND WESTERN MA. THUS, THERE IS A  
RISK FOR SOME LIGHT ICING. THE TIMING OF THIS WOULD BE BETWEEN  
THE MORNING AND EVENING COMMUTES. THIS WOULD MINIMIZE THE IMPACT  
OF ANY LIGHT ICING.  
 
THE SHORT DURATION OF SNOWFALL SHOULD LIMIT SNOW ACCUMULATIONS,  
TOO. NOT EXPECTING MUCH MORE THAN 1-2" INCHES ACROSS THE HIGHER  
TERRAIN.  
 
WINDS AT 925 MB AND 950 MB SHOW A LOW-LEVEL SOUTHEAST JET NEAR  
NYC AT 7 AM, THEN MOVING ALONG THE SOUTH COAST AND INCREASING  
TO 40-50 KT BY LATE IN THE DAY. EXPECT INCREASING SOUTHEAST  
WINDS DURING THE DAY. ALTHOUGH NOT ALL OF THAT WIND ALOFT WILL  
REACH THE SURFACE, IT IS REASONABLE TO EXPECT GUSTS 25-30 KT  
ALONG THE COAST.  
 
PRECIPITATION DIMINISHES TUESDAY EVENING, WITH DRY WEATHER  
EXPECTED AFTER MIDNIGHT ACROSS MOST OF THE REGION.  
 
ABOVE NORMAL TEMPERATURES THROUGH THIS PERIOD.  
 

 
   
LONG TERM /WEDNESDAY THROUGH MONDAY/
 
 
HIGHLIGHTS...  
 
* DRY WEATHER LIKELY THROUGH THE WEEKEND  
 
* COLDER TREND WITH COLDEST AIR ARRIVING THU NIGHT INTO EARLY FRI  
 
* TEMPERATURES LIKELY REBOUND BACK INTO 40S OVER THE WEEKEND  
 
DETAILS...  
 
WEDNESDAY/THURSDAY/FRIDAY ...  
 
POST FRONTAL AIRMASS OVERSPREADS THE REGION WED WITH DRY WEATHER  
AND STRENGTHENING LOW LEVEL COLD AIR ADVECTION WITH 925 MB TEMPS  
LOWERING FROM -2C AT 12Z WED TO -8C BY 00Z THU. GIVEN DELAY OF  
COLD AIR HIGHS WED NEAR NORMAL WITH HIGHS FROM THE UPPER 30S TO  
LOWER 40S, MID 30S HIGH TERRAIN. GIVEN THE COLD AIR ADVECTION  
AND STEEPENING LOW LEVEL LAPSE RATES EXPECTING BLUSTERY NW WINDS  
WITH GUSTS UP TO 35 MPH PER MODEL SOUNDINGS. THUS IT WILL FEEL  
COLDER THAN THE ACTUAL AIR TEMPS. EVEN COLDER THURSDAY WITH 925  
MB TEMPS CONTINUING TO LOWER TO ABOUT -12C TO -13C, ONLY  
SUPPORTING HIGHS IN THE UPPER 20S AND LOWER 30S, MID 20S HIGH  
TERRAIN. COLD WIND CHILLS AS WELL GIVEN BRISK WEST WIND GUSTING  
UP TO 25 MPH PER MODEL SOUNDINGS.  
 
CORE OF THE COLD AIR ARRIVES THU NIGHT INTO FRI MORNING AS 925  
MB TEMPS LOWER TO -15C TO -16C. THIS WILL YIELD LOW TEMPS LATE  
THU NIGHT/EARLY FRI MORNING IN THE SINGLE DIGITS (POSSIBLE BELOW  
ZERO NORTHWEST MA PER SOME GUIDANCE SOURCES) AND TEENS. NOT  
RECORD BREAKING BUT ABOUT 10 DEGS COLDER THAN NORMAL AND GIVEN  
OUR RECENT STRETCH OF MILD WEATHER IT WILL FEEL QUITE COLD. NOT  
MUCH OF TEMP REBOUND FRI WITH HIGHS ONCE AGAIN ONLY IN THE UPPER  
20S AND LOWER 30S. AS WINDS SHIFT TO THE NNE THU NIGHT INTO FRI  
MORNING COULD SEE SOME OCEAN EFFECT SNOW SHOWERS ACROSS THE  
OUTER CAPE AND NANTUCKET GIVEN TRAJECTORY OF COLD AIR (NNE FLOW)  
AND RELATIVELY MILD OCEAN TEMPS IN THE LOW 40S SUPPORTING STEEP  
LOW LEVEL LAPSE RATES. IN ADDITION DEVELOPING LOW PRESSURE OFF  
THE SOUTHEAST U.S. COAST DURING THIS TIME MAY ENHANCE THE NNE  
FLOW INTO THE CAPE AND NANTUCKET. SOMETHING TO WATCH AS LATE  
WEEK APPROACHES.  
 
THE WEEKEND ...  
 
RISING HEIGHTS WILL SUPPORT MODERATING TEMPERATURES WITH HIGHS  
LIKELY REBOUNDING BACK INTO 40S ALONG WITH DRY WEATHER AND  
POSSIBLY LINGERING INTO MONDAY.  
 

 
   
AVIATION /21Z MONDAY THROUGH SATURDAY/
 
 
FORECASTER CONFIDENCE LEVELS...  
 
LOW - LESS THAN 30 PERCENT.  
MODERATE - 30 TO 60 PERCENT.  
HIGH - GREATER THAN 60 PERCENT.  
 
TONIGHT...HIGH CONFIDENCE.  
 
VFR WITH DRY WEATHER AND LIGHT WIND BEFORE MIDNIGHT, THEN LIGHT  
NORTHEAST TO EAST WIND OVERNIGHT. INCREASING CLOUDS ARRIVE  
OVERNIGHT, BUT WITH 10 THOUSAND TO 20 THOUSAND FOOT CLOUD  
BASES. LOWER CLOUDS MAY ARRIVE TOWARD SUNRISE.  
 
TUESDAY...HIGH CONFIDENCE IN OCCURRENCE, MODERATE CONFIDENCE IN  
TIMING.  
 
CONDITIONS LOWERING TO MVFR/IFR. LIGHT SNOW DEVELOPING WITH LESS  
THAN AN INCH MOST PLACES, 1-2 INCHES POSSIBLE ACROSS NORTHWEST  
MA. SNOW CHANGING TO RAIN DURING THE MORNING. INCREASING  
SOUTHEAST WIND AT THE COASTS, WITH GUSTS 25 TO 30 KT.  
 
TUESDAY NIGHT...BECOMING VFR, WITH LOCAL IFR POSSIBLE IN THE  
EVENING. BREEZY. CHANCE RA.  
 
KBOS TERMINAL...HIGH CONFIDENCE IN TAF.  
 
KBDL TERMINAL...HIGH CONFIDENCE IN TAF.  
 
OUTLOOK /WEDNESDAY THROUGH SATURDAY/...  
 
WEDNESDAY: VFR. WINDY WITH GUSTS UP TO 35 KT.  
 
WEDNESDAY NIGHT THROUGH THURSDAY: VFR. BREEZY.  
 
THURSDAY NIGHT: VFR.  
 
FRIDAY THROUGH SATURDAY: VFR. BREEZY.  
 

 
   
MARINE
 
 
TONIGHT...  
 
CANADIAN HIGH PRESSURE MOVES OVER THE MARITIMES BY MORNING.  
EXPECT DRY WEATHER AND GOOD VISIBILITY. LIGHT WIND SHIFTING  
FROM THE NORTHEAST AND EAST. SEAS LESS THAN 5 FEET.  
 
TUESDAY...  
 
INCREASING SOUTHEAST WIND THROUGH THE DAY, WITH GUSTS 25 TO  
30 KT. SEAS BUILDING TO 5 TO 9 FEET ON THE EXPOSED WATERS,  
HIGHEST EAST OF MASSACHUSETTS. RAIN DEVELOPING, WITH VISIBILITY  
LOWERING TO 1 TO 3 NM.  
 
TUESDAY NIGHT...  
 
SOME GUSTS TO GALE FORCE ACROSS THE EASTERN OUTER COASTAL WATERS  
DURING THE EVENING. WINDS DIMINISH AFTER MIDNIGHT. ROUGH SEAS  
CONTINUE ACROSS THE OUTER COASTAL WATERS.  
 
OUTLOOK /WEDNESDAY THROUGH SATURDAY/...  
 
WEDNESDAY: MODERATE RISK FOR SMALL CRAFT ADVISORY WINDS WITH  
GUSTS UP TO 30 KT. AREAS OF ROUGH SEAS.  
 
WEDNESDAY NIGHT: LOW RISK FOR SMALL CRAFT ADVISORY WINDS WITH  
GUSTS UP TO 30 KT. SEAS UP TO 5 FT.  
 
THURSDAY: WINDS LESS THAN 25 KT. SEAS UP TO 5 FT.  
 
THURSDAY NIGHT: WINDS LESS THAN 25 KT. AREAS OF SEAS  
APPROACHING 5 FT.  
 
FRIDAY: WINDS LESS THAN 25 KT. SEAS LOCALLY APPROACHING 5 FT.  
 
FRIDAY NIGHT: LOW RISK FOR SMALL CRAFT ADVISORY WINDS WITH  
GUSTS UP TO 25 KT. AREAS OF SEAS APPROACHING 5 FT.  
 
SATURDAY: WINDS LESS THAN 25 KT. LOCAL ROUGH SEAS.  
 

 
   
BOX WATCHES/WARNINGS/ADVISORIES
 
 
CT...NONE.  
MA...NONE.  
RI...NONE.  
MARINE...SMALL CRAFT ADVISORY FROM 8 AM TUESDAY TO 7 AM EST WEDNESDAY  
FOR ANZ232>235-237-255.  
SMALL CRAFT ADVISORY FROM 10 AM TO 4 PM EST TUESDAY FOR ANZ230.  
SMALL CRAFT ADVISORY FROM 10 AM TUESDAY TO 7 AM EST WEDNESDAY  
FOR ANZ231-251.  
SMALL CRAFT ADVISORY FROM 8 AM TO 6 PM EST TUESDAY FOR ANZ236.  
GALE WARNING FROM 3 PM TO 9 PM EST TUESDAY FOR ANZ250-254.  
SMALL CRAFT ADVISORY FROM 6 AM TUESDAY TO 7 AM EST WEDNESDAY  
FOR ANZ256.  
 

 
 

 
SYNOPSIS...BELK/NOCERA  
NEAR TERM...BELK  
SHORT TERM...BELK  
LONG TERM...NOCERA  
AVIATION...BELK/NOCERA  
MARINE...BELK/NOCERA  
 
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