536  
FXUS61 KGYX 290114  
AFDGYX  
 
AREA FORECAST DISCUSSION...UPDATED  
NATIONAL WEATHER SERVICE GRAY ME  
914 PM EDT TUE MAR 28 2017  
   
SYNOPSIS
 
 
LOW PRESSURE WILL PASS TO OUR SOUTH TONIGHT. BEHIND THIS SYSTEM,  
A NORTHWESTERLY FLOW WILL INTRODUCE COOLER AND DRIER AIR INTO  
THE REGION FOR THE SECOND HALF OF THE WORK WEEK. HIGH PRESSURE  
WILL BUILD INTO THE REGION FOR THURSDAY. LOW PRESSURE WILL  
APPROACH THE REGION FOR LATE FRIDAY INTO SATURDAY WITH SNOW AND  
MIXED PRECIPITATION LIKELY FOR THE REGION.  
 

 
   
NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/
 
 
01Z UPDATE...  
LATEST MESOSCALE GUIDANCE CONTINUES TO SHOW SHOWERS HUGGING THE  
COAST WITH LESS OROGRAPHIC ACTIVITY AND LITTLE PRECIPITATION  
INLAND EXCEPT OVER SOUTHERN NH. WILL KEEP THIS TREND GOING IN  
THE FORECAST WITH POPS CLOSELY RESEMBLING HRRR AND RAP  
QUALITATIVELY/IN SHAPE IF NOT QUANTITATIVELY. HAVE TAPERED POPS  
AS ONE MOVES INLAND. DENSE FOG WAS ADDED EVERYWHERE AND THIS IS  
MORE OF AN ISSUE CURRENTLY NORTH OF THE PRECIPITATION SHIELD AS  
CAN BE EXPECTED WITH MIXING. EXPECT AREAS OF DENSE FOG TO BLOOM  
ACROSS THE SOUTH AS WELL ONCE RAIN CLEARS OUT. AN ADVISORY MAY  
BE NEEDED BUT HAVE NOT DECIDED ON ONE QUITE YET. OTHERWISE RAIN  
SHOWERS WILL DIMINISH TO DRIZZLE OVERNIGHT WITH VERY LOW  
CEILINGS.  
 
21Z UPDATE...  
HAVE ADJUSTED POPS AND QPF AND CORRESPONDING SNOW AMOUNTS BASED  
ON THE LATEST FEW RUNS OF THE HRRR WHICH HAS A GOOD HANDLE ON  
THE CONVECTION. ONE AREA OF LIFT ASSOCIATED WITH A SHORT WAVE  
AND A WARM FRONT WAS PRODUCING SHOWERS OVER SOUTHERN SECTIONS OF  
NH AND MAINE. ELSEWHERE UPSLOPE SNOW SHOWERS WERE AFFECTING THE  
MOUNTAINS AND FOOTHILLS. PRECIPITATION CHANCES WERE ADJUSTED SO  
CATEGORICAL POPS WERE NOT BROAD-BRUSHED AND INSTEAD FOCUSED ON  
THESE TWO AREAS. A FEW OTHER MINOR CHANGES WERE MADE BUT NOTHING  
TO CHANGE THE FORECAST WHOLESALE.  
 
PREVIOUS DISCUSSION...  
A WEAK SHORTWAVE IMPULSE ON GOES WATER VAPOR IMAGERY WAS  
CROSSING THE MID ATLANTIC REGION WITH A 1009 MILLIBAR SURFACE  
REFLECTION OVER THE DELMARVA REGION AND A WEAK SURFACE BOUNDARY  
EXTENDING NORTHWARD INTO WESTERN NEW ENGLAND. WIDESPREAD LOW  
CLOUDS REMAINED ACROSS THE REGION AT MOMENT. NWS DOPPLER RADAR  
MOSAIC SHOWED AN EXPANDING AREA OF PRECIPITATION ACROSS THE MID  
ATLANTIC TO SOUTHWESTERN NEW ENGLAND THAT WILL CROSS SOUTHERN  
NEW HAMPSHIRE AND ADJACENT SOUTHWEST COASTAL MAINE DURING THE  
LATE AFTERNOON AND EARLY EVENING HOURS. ELSEWHERE...ONLY  
SCATTERED PRECIPITATION IS LIKELY AS A COLD FRONT OVER QUEBEC  
DROPS SOUTHWARD ACROSS THE REGION OVERNIGHT. THE ACTIVITY SHOULD  
TAPER QUICKLY AFTER MIDNIGHT AS THE SURFACE LOW AND SHORTWAVE  
IMPULSE RACE OFFSHORE.  
 

 
   
SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/
 
 
ON WEDNESDAY...A FRESHENING NORTHERLY BREEZE IN THE WAKE OF THE  
DEPARTING COASTAL LOW WITH A FEW CLOUDS AND UPSLOPE SNOW OR  
RAIN SHOWERS ACROSS THE HIGHER TERRAIN. HIGHS WILL RANGE FROM  
NEAR 40 IN THE MOUNTAINS TO NEAR 50 OVER SOUTHEAST NEW  
HAMPSHIRE. SOME LINGERING UPSLOPE CLOUDS AND SNOW SHOWERS  
WEDNESDAY NIGHT IN THE MOUNTAINS...OTHERWISE MOSTLY CLEAR  
ELSEWHERE WITH A DIMINISHING NORTHERLY BREEZE AND THE SURFACE  
HIGH BEGINS BUILDING INTO EASTERN NEW ENGLAND. LOWS WILL RANGE  
FROM THE MID 20S TO AROUND 30.  
 

 
   
LONG TERM /THURSDAY THROUGH TUESDAY/
 
 
CONFIDENCE IS GRADUALLY INCREASING FOR A FAIRLY SIGNIFICANT LATE  
SEASON SNOW AND/OR MIXED PRECIPITATION EVENT STARTING FRIDAY AND  
LASTING INTO SATURDAY. 12Z DETERMINISTIC GUIDANCE IS IN GENERAL  
AGREEMENT TODAY ON TRACK OF SHORT WAVE TROUGHS AND ATTENDANT SFC  
LOW PRESSURE ALONG WITH SUBSEQUENT HEAVY SNOWFALL FOR AT LEAST  
THE SOUTHERN HALF OF THE CWA. THE ECMWF ENSEMBLE PROBABILITIES  
FOR 6 OR MORE INCHES OF SNOW HAVE STEADILY INCREASED OVER THE  
LAST 24 HOURS, NOW OFFERING A 50-70 PERCENT CHANCE OF 6"+ TO A  
FAIRLY GOOD CHUNK OF THE CWA.  
 
HOWEVER, WITH THAT SAID, WE ARE STILL AT LEAST 3 DAYS OUT AND  
EVEN TIGHT ENSEMBLE CONSENSUS CAN STILL GO AWRY AT THIS TIME  
RANGE. THERE ARE ALSO QUESTIONS ABOUT BOUNDARY LAYER  
TEMPERATURES AND PERHAPS EVEN SOME WARM MID LEVEL TEMPS CREEPING  
INTO SOUTHERNMOST ZONES. THE TRACK OF THE OVERALL SYSTEM COULD  
STILL PUSH FURTHER SOUTH ALSO. THESE ISSUES CAN CERTAINLY BE THE  
CAUSE OF A LIGHTER SNOWFALL. SO BEING A BIT CONSERVATIVE IN THE  
FORECAST TEMPERATURE/QPF/SNOW GRIDS IS PRUDENT AT THIS TIME.  
HOWEVER, WE DID LOWER SFC TEMPS FRIDAY AFTERNOON AND NIGHT AS MOST  
RAW MODEL GUIDANCE SLAMS SFC TEMPS DOWN TO 31-33 DEGREES AS  
STRONG UVVS MOVE INTO THE AREA AND ALLOW FOR COOLING VIA LIFT,  
EVAPORATION, AND MELTING.  
 
AT THIS TIME I WOULD EXPECT AT LEAST INTERIOR SOUTHERN ZONES TO  
PICK UP A PLOWABLE SNOWFALL STARTING FRIDAY AFTERNOON OR EVENING  
AND ENDING SATURDAY. HOWEVER, THERE IS LOW CONFIDENCE AT THIS  
TIME FOR A LOT MORE OVER A WIDE AREA, ALTHOUGH POSSIBLE. BEARS  
WATCH FOR SURE. A HEAVIER SNOWFALL THIS TIME OF YEAR WOULD  
PROBABLY CAUSE POWER OUTAGE ISSUES.  
 

 
   
AVIATION /01Z WEDNESDAY THROUGH SUNDAY/
 
 
SHORT TERM...IFR TO LIFR CONDITIONS PERSIST FOR ALL TAF SITES  
THROUGH THE OVERNIGHT HOURS IN LOW STRATUS AND AREAS OF DENSE  
FOG...AS WELL AS -SHRA AND -DZ ALONG THE COAST AS WELL AS HIE,  
CON, AND MHT. LOOK FOR IMPROVEMENT TO VFR DURING WEDNESDAY  
MORNING FOR MOST TERMINALS ALTHOUGH MOISTURE TRAPPED UNDER AN  
INVERSION MAY MAKE IMPROVEMENT SLOW GOING FOR MOUNTAIN  
TERMINALS. NW WINDS WILL EVENTUALLY GUST TO BTW 20 AND 25 KT  
IN THE AFTERNOON. SCT MVFR CONDITIONS WILL BE PSB IN MTNS ONCE  
AGAIN IN -SHRA/-SHSN.  
 
LONG TERM...IFR CONDITIONS POSSIBLE IN SNOW AND MIXED  
PRECIPITATION STARTING FRIDAY AND LASTING INTO SATURDAY.  
CONDITIONS LIKELY IMPROVE SATURDAY NIGHT AND SUNDAY.  
 

 
   
MARINE
 
 
SHORT TERM...WINDS AND SEAS WILL REMAIN BELOW SMALL CRAFT  
THROUGH WEDNESDAY AFTERNOON. CONDITIONS WILL REACH SMALL CRAFT  
ADVISORY THRESHOLD BY WEDNESDAY EVENING OUTSIDE THE BAYS IN  
STRENGTHENING NORTHERLY FLOW.  
 
LONG TERM...SCA CONDITIONS WILL SUBSIDE THURSDAY. THEY WILL ONCE  
AGAIN BE POSSIBLE OVER THE WEEKEND AS LOW PRESSURE PASSES TO THE  
SOUTH OF THE WATERS.  
 

 
   
TIDES/COASTAL FLOODING
 
 
WE'RE ENTERING THE PERIOD OF HIGH ASTRONOMICAL TIDES. THE  
WEDNESDAY AND THURSDAY NIGHT HIGH TIDES...AT 105 AM THURSDAY  
AND 152 AM FRIDAY RESPECTFULLY ARE 11.1 FT MLLW (REFERENCED TO  
PORTLAND HARBOR WITH A 12.0 FT MLLW FLOOD STAGE). FORTUNATELY  
THE FLOW WILL BE OFFSHORE SO NO PROBLEMS ARE ANTICIPATED WITH  
THESE PARTICULAR TIDES. HOWEVER, THE FRIDAY NIGHT HIGH TIDE AT  
243 AM IS AN 11.0 FT MLLW. WITH POTENTIAL FOR A STRENGTHENING  
ONSHORE FLOW PRIOR TO THIS PARTICULAR HIGH TIDE CYCLE...WE WILL  
NEED TO MONITOR THIS TIME PERIOD FOR POSSIBLE COASTAL FLOODING  
AND BEACH EROSION.  
 

 
   
GYX WATCHES/WARNINGS/ADVISORIES
 
 
ME...NONE.  
NH...NONE.  
MARINE...NONE.  
 

 
 

 
 
NEAR TERM...HANES  
SHORT TERM...SCHWIBS  
LONG TERM...EKSTER  
 
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