395  
FXUS61 KGYX 170426  
AFDGYX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GRAY ME  
1126 PM EST WED JAN 16 2019  
   
SYNOPSIS
 
 
A COLD FRONT WILL CROSS THE REGION LATE TODAY ACCOMPANIED BY  
SCATTERED SNOW SHOWERS AND A FEW MOUNTAIN SNOW SQUALLS. IT WILL  
BE 15 TO 20 DEGREES COLDER ON THURSDAY AS ARCTIC HIGH PRESSURE  
BUILDS IN. THE NEXT WAVE OF LOW PRESSURE TRACKS ACROSS THE  
REGION ON FRIDAY BRINGING WIDESPREAD BUT LIGHT SNOWFALL. A  
LARGER STORM WILL BRING WINTRY WEATHER FOR THE SECOND HALF OF  
THE UPCOMING WEEKEND. SIGNIFICANT AMOUNTS OF WINTRY  
PRECIPITATION ARE LIKELY, BUT THE EXACT TRACK WILL DETERMINE  
THOSE PRECIPITATION TYPES.  
 

 
   
NEAR TERM /UNTIL 6 AM THURSDAY MORNING/
 
 
UPDATE...  
HAVE UPDATED THE FORECAST BASED ON CURRENT OBSERVATIONS AND  
LATEST RADAR IMAGERY. SCATTERED SNOW SHOWERS AND POSSIBLY A  
COUPLE SNOW SQUALLS EXITED THE MOUNTAINS AND FOOTHILLS EARLIER  
AND WEAKEND. HAVE ADDED HIGHER WINDS FOR TERRAIN ABOVE 4500  
FEET AS MOUNT WASHINGTON CONTINUES TO GUST WELL OVER HURRICANE  
FORCE THIS EVENING.  
 
OTHERWISE, ONLY MINOR ADJUSTMENTS MADE TO POPS, TEMPERATURES AND  
SKY COVER THIS EVENING.  
 
PREV DISC...  
LOW PRESSURE TRACKING THROUGH SOUTHERN QUEBEC IS DRAGGING A  
COLD FRONT THROUGH NEW ENGLAND AT PRESENT. THIS HAS TRIGGERED  
NUMEROUS SNOW SHOWERS WHICH HAVE RECENTLY SHOWN UP ON REGIONAL  
RADAR OVER THE WHITE MOUNTAINS. SNOW SQUALLS ARE STILL INDICATED  
FOR THE MOUNTAINS AND FOOTHILLS THE NEXT FEW HOURS, AND HAVE  
COVERED THIS THREAT WITH A STATEMENT WHICH CAUTIONS FOR LOCALLY  
HEAVY SNOWFALL CAUSING LOW VISIBILITIES FOR THE AFTERNOON  
COMMUTE.  
 
THE ARCTIC COLD FRONT MOVES OFFSHORE AROUND 6 PM BRINGING AN END  
TO PRECIPITATION. GUSTY NW WINDS WILL FOLLOW FOR A FEW HOURS  
ALLOWING MUCH COLDER AND DRIER AIR TO POUR IN FROM THE NORTH.  
SKIES CLEAR OUT QUICKLY AND OVERNIGHT LOWS WILL DROP TO NEAR  
-10F ACROSS THE NORTH TO THE SINGLE DIGITS SOUTH. A WIND CHILL  
ADVISORY REMAINS IN EFFECT FOR AREAS INCLUDING THE NORTHERN  
MOUNTAINS OF NH AND MAINE TONIGHT INTO TOMORROW MORNING.  
 

 
   
SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY/
 
 
WE WILL SEE HIGHS THURSDAY IN THE SINGLE DIGITS NORTH TO TEENS  
FOR THE COASTAL PLAIN WITH COLD HIGH PRESSURE DRIFTING FROM WEST  
TO EAST. OVER SOUTHERN NH AND ALONG THE IMMEDIATE COAST  
READINGS WILL REACH THE LOWER 20S. LOWS FRIDAY NIGHT WON'T BE AS  
BRUTALLY COLD AS THE PREVIOUS NIGHT, WITH READINGS AROUND ZERO  
ACROSS THE NORTH AND IN THE 10S SOUTH.  
 
SKIES WILL BEGIN TO INCREASE FROM THE SW THURSDAY NIGHT AS A  
WEAK AND POORLY ORGANIZED STORM APPROACHES FROM THE MIDWEST. WE  
WILL HAVE A VERY COLD AIRMASS IN PLACE THROUGHOUT THE  
ATMOSPHERE, AND AS LOW PRESSURE CROSSES THE AREA WIDESPREAD BUT  
WEAKLY FORCED SNOWFALL IS EXPECTED FRIDAY BEGINNING BEFORE DAWN  
AND ENDING SOMETIME IN THE AFTERNOON AS DRIER AIR IS DRAWN IN  
FROM THE SW. SPECIFIC HUMIDITIES ARE LOW INDICATING LOW QPF  
AMOUNTS. THIS YIELDS A WIDESPREAD 1-3" SNOWFALL WITH THE HIGHER  
AMOUNTS OVER THE MOUNTAINS AND THE MID COAST REGION WHERE THE  
SYSTEM BEGINS TO DEEPEN RIGHT BEFORE TAKING OFF IN FAST MOVING  
CONVERGENT FLOW ALOFT. TEMPERATURES SHOULD REACH THE LOWER 20S  
NORTH TO MID 30S TOWARDS SOUTHERN SECTIONS.  
 

 
   
LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/
 
 
HIGH IMPACT WEATHER: *** SIGNIFICANT WINTER STORM WILL IMPACT THE  
REGION FROM SATURDAY NIGHT INTO SUNDAY. ***  
 
OVERVIEW: CONFIDENCE IS INCREASING FOR A SIGNIFICANT WINTER STORM TO  
IMPACT THE REGION OVER THE WEEKEND. SATURDAY WILL START OFF CLEAR  
AND COLD OVER NORTHERN NEW ENGLAND AS HIGH PRESSURE EXITS TO THE  
EAST. MEANWHILE OUR STORM WILL DEVELOP OVER THE FOUR CORNERS AND  
RAPIDLY INTENSIFY AS IT MOVES ACROSS THE SOUTHERN PLAINS. BY 00Z  
SUNDAY WE'LL SEE THE FIRST FLAKES MOVING INTO SOUTHERN NEW HAMPSHIRE  
AS THE LOW MOVES UP THE OHIO RIVER VALLEY. BY SUNDAY MORNING THE LOW  
WILL MOVE OFFSHORE OF DELMARVA WITH SIGNIFICANT SNOWFALL IN THE  
NORTHWEST QUADRANT. HEAVY SNOW WILL CONTINUE THROUGH THE DAY ON  
SUNDAY BEFORE COMING TO AN END LATE SUNDAY NIGHT.  
 
TRENDS: OVER THE PAST DAY OR SO WE'VE SEEN A CONSISTENT COLDER  
TREND IN THE GUIDANCE AS THE LOW CENTER SHIFTS FURTHER OFFSHORE.  
AS OF 12Z A SUPER MAJORITY OF ENSEMBLE MEMBERS WOULD KEEP THE  
LOW CENTER EAST OF THE MAINE COAST OVER THE GULF OF MAINE  
KEEPING OUR REGION IN SNOW.  
 
UPPER LEVEL PATTERN: THIS NOR'EASTER WILL FORM IN A PRETTY CLASSIC  
PATTERN ALONG THE EASTERN EDGE OF A DEEPENING 500MB TROUGH. TO OUR  
WEST THE WEST CONUS REMAINS UNDER STRONG HIGH PRESSURE WITH THE  
RESULT BEING BLOCKED FLOW. THIS ALLOWS OUR STORM TO SOURCE FROM  
TWO REGIONS. A SHORT WAVE IN THE NORTHERN STREAM WILL DIVE  
SOUTH THROUGH THE CANADIAN PRAIRIES. AS IT DOES THE SOUTHERN  
STREAM LOW OVER THE SOUTHERN PLAINS WILL ALSO PHASE WITH THE TWO  
SYSTEMS COMBINING TO FOR A VERY ELONGATED LOW PRESSURE ALONG  
THE COAST. WHENEVER THERE ARE TWO SYSTEMS TRYING TO ACT IN PHASE  
THERE IS ROOM FOR ERROR, AND WITH NEITHER OF THEM ONSHORE YET  
THAT IS CERTAINLY THE CASE HERE HOWEVER THE PRESENCE OF AN  
UPPER BLOCK OVER ALASKA ALONG WITH WEAKLY BLOCKED FLOW OVER  
EUROPE SUPPORTS THE STRENGTHENING EAST COAST TROUGH.  
 
PTYPE: OVER THE PAST FEW DAYS PTYPE HAS BEEN A CONCERN WITH THIS  
SYSTEM BUT IT GRADUALLY BECOMING LESS SO AS THE COLDER TREND APPEARS  
TO BE WINNING. THE KEY HERE IS REALLY THAT NORTHERN STREAM SHORT  
WAVE WILL PROVIDE THE FORCING TO KEEP THE WARMER AIR OFFSHORE.  
TRYING NOT TO FLIP FLOP TOO HARD HAVE OPTED TO LEAVE SOME MIXED  
SLEET AND FREEZING RAIN IN PLACE ALONG THE COAST BUT FEEL THAT  
AN ALL SNOW SOLUTION IS BECOMING MORE AND MORE LIKELY. A BIT OF  
FREEZING DRIZZLE IS ALSO POSSIBLE ON THE BACKSIDE IN THE DRY  
SLOT BUT OVERALL WE ARE LOOKING AT A SNOWSTORM WITH A CHANCE FOR  
SOME MIX ALONG THE COAST NOT A WIDESPREAD ICING EVENT.  
 
SNOW AMOUNTS: IF YOU'VE BEEN WAITING FOR WINTER, HERE IT IS.  
POTENTIAL FOR VERY HEAVY SNOW ACCUMULATION /WIDESPREAD DOUBLE  
DIGIT SNOWFALL/ CONTINUES TO INCREASE. WITH 1-1.5" OF LIQUID  
PRECIPITATION, EVEN A MODEST 10:1 SNOW RATIO EASILY ACHIEVES  
THAT OBJECTIVE. IN FACT HIGHER SNOW RATIOS ARE QUITE POSSIBLE,  
PARTICULARLY IN THE INTERIOR. FORECAST SOUNDINGS SHOW STRONG  
UPWARD MOTION IN THE SNOW GROWTH ZONE ON SUNDAY MORNING ACROSS  
SOUTHERN MAINE AND EXPECT A REGION OF SNOWFALL RATES OVER 1"/HR  
THROUGH SUNDAY. IT'S FAR TOO EARLY TO PIN DOWN ANY MESOSCALE  
EFFECTS OTHER THAN TO MENTION THAT STRONG SNOW BANDS ARE LIKELY  
WITH THIS KIND OF STRONG DYNAMIC STORM AND ANY AREAS THAT REMAIN  
UNDER SNOWBANDS MAY SEE CLOSER TO 2"/HR RATES.  
 
WIND: A LOOK AT THE PRESSURE GRADIENT AND RAPID STRENGTHENING  
OF THE SYSTEM SAYS THAT STRONG WINDS ARE LIKELY WITH THIS  
SYSTEM. THE TRICK WILL BE GETTING THEM DOWN TO THE SURFACE AS A  
MORE STABLE COLD LAYER OVER LAND MAY LIMIT THE MIXING SOMEWHAT.  
HOWEVER ALONG THE COAST LINE AND CERTAINLY OVER THE COASTAL  
WATERS STRONGER GUSTS ARE LIKELY.  
 
MONDAY AND BEYOND: A VERY COLD AIRMASS WILL MOVE IN BEHIND THE STORM  
WITH THE POTENTIAL FOR BELOW ZERO TEMPERATURES DOWN TO THE COAST.  
 

 
   
AVIATION /06Z THURSDAY THROUGH MONDAY/
 
 
SHORT TERM /THROUGH THURSDAY/...VARIABLE CEILINGS ACROSS THE  
AREA WITH IMPROVEMENT TO MOSTLY VFR DECKS WITH THE OCCASIONAL  
MVFR. CLEARING AND IMPROVEMENT WILL CONTINUE AS A COLD FRONT  
PUSHES OFFSHORE TONIGHT. GUSTY WNW WINDS WILL DEVELOP THIS  
AFTERNOON AND EVENING BEFORE DIMINISHING OVERNIGHT. WINDS BECOME  
LIGHT AND VARIABLE THURSDAY AS HIGH PRESSURE BUILDS IN WITH  
PREVAILING VFR.  
 
LONG TERM...SATURDAY WILL BEGIN VFR AS HIGH PRESSURE DEPARTS. CLOUDS  
WILL RAPIDLY ENCROACH AND DESCEND THROUGH THE AFTERNOON DROPPING TO  
MVFR BY SUNSET. SNOW WILL TAKE HOLD IN THE EARLY MORNING HOURS OF  
SUNDAY WILL ALL LOCATIONS EXPECTING LIFR IN HEAVY SNOW THROUGH THE  
DAY ON SUNDAY. SOME MVFR SNOW SHOWERS WILL REMAIN THROUGH THE  
MOUNTAINS ON MONDAY WITH A STEADY NORTHWESTERLY WIND THROUGHOUT  
THE REGION AS COLD AIR MOVES INTO THE AREA.  
 

 
   
MARINE
 
 
SHORT TERM /THROUGH THURSDAY/...WINDS REMAIN GUSTY IN  
ASSOCIATION WITH A COLD FRONTAL PASSAGE THIS AFTERNOON AND  
EVENING. GALES REMAIN IN PLACE FOR ALL AREAS BUT CASCO BAY WHERE  
A SMALL CRAFT ADVISORY IS IN EFFECT. A FREEZING SPRAY ADVISORY  
HAS BEEN ISSUED FOR THE CENTRAL AND EASTERN OUTER WATERS AS WELL  
AS PENOBSCOT BAY OVERNIGHT AND INTO THURSDAY MORNING WHERE  
MODERATE FREEZING SPRAY WILL OCCUR.  
 
LONG TERM... A COASTAL LOW WILL RAPIDLY INTENSIFY AND MOVE  
THROUGH THE GULF OF MAINE FROM SATURDAY NIGHT INTO SUNDAY WITH  
STORM FORCE WINDS POSSIBLE ON THE OUTER WATERS AND GALES LIKELY  
IN THE BAYS. WAVES WILL BUILD TO 10-20FT. HAVE INCREASED BOTH  
THE WIND GUSTS AND WAVE HEIGHT AS THE RELATIVELY WARMER WATER  
TEMPERATURES WILL ALLOW FOR UNSTABLE CONDITIONS NEAR THE SURFACE  
OVER THE WATERS AND GOOD MIXING.  
 

 
   
TIDES/COASTAL FLOODING
 
 
HIGH ASTRONOMICAL TIDES WILL COMBINE WITH AN APPROACHING STORM  
WITH STRONG NORTHEASTERLY WINDS AND BUILDING WAVES DURING THE  
DAY ON SUNDAY. THE TIMING OF THE PEAK WINDS/WAVES WILL BE  
CRUCIAL TO THIS FORECAST AND MAY VARY FROM MODEL RUN TO MODEL  
RUN.  
 
THE ASTRONOMICAL HIGH TIDE IN PORTLAND WILL BE NEAR 10 AM ON  
SUNDAY AT 11.1 FEET. LEANED HEAVILY TOWARDS THE ESTOFS MODEL  
WHICH IS MORE ROBUST IN TERMS OF STORM SURGE LEVELS AT AROUND  
1.3 FEET. THIS VALUE MAY BE HIGHER, BUT ALSO ARRIVE AFTER HIGH  
TIDE. IN ANY CASE, THIS EVENT WILL LIKELY PRODUCE MINOR COASTAL  
FLOODING AND SPLASH-OVER AROUND THE TIME OF HIGH TIDE WITH  
POCKETS OF MODERATE FLOODING POSSIBLE FROM PORTLAND AND POINTS  
SOUTH TO HAMPTON HARBOR SUNDAY MORNING. LONG PERIOD SWELLS ARE  
FORECAST TO ARRIVE SUNDAY NIGHT INTO MONDAY, SO THIS WILL NEED  
TO BE MONITORED FOR A CONTINUED POSSIBILITY FOR SOME SPLASH-  
OVER.  
 

 
   
GYX WATCHES/WARNINGS/ADVISORIES
 
 
ME...WIND CHILL ADVISORY UNTIL 10 AM EST THURSDAY FOR MEZ007>009.  
NH...WIND CHILL ADVISORY UNTIL 10 AM EST THURSDAY FOR NHZ001-002.  
MARINE...SMALL CRAFT ADVISORY UNTIL 7 AM EST THURSDAY FOR ANZ153.  
FREEZING SPRAY ADVISORY UNTIL 11 AM EST THURSDAY FOR  
ANZ150>152.  
GALE WARNING UNTIL 7 AM EST THURSDAY FOR ANZ150>152-154.  
 

 
 

 
JC  
 
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