530  
FXUS61 KGYX 192347  
AFDGYX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GRAY ME  
747 PM EDT MON APR 19 2021  
   
SYNOPSIS
 
 
A LARGE UPPER LEVEL TROUGH AND SURFACE CYCLONE WILL TRACK  
THROUGH NEW ENGLAND ON WEDNESDAY AND WEDNESDAY NIGHT BRINGING  
WIDESPREAD RAIN AND SNOW TO THE REGION. THE HIGHEST CHANCE FOR  
ACCUMULATING SNOW WILL BE ACROSS THE HIGHER ELEVATIONS AND FAR  
NORTH, WHERE SEVERAL INCHES ARE POSSIBLE. GUSTY NORTHWEST WINDS  
WILL ALSO BE POSSIBLE AS THE SYSTEM PULLS AWAY TO THE NORTH AND  
EAST ON WEDNESDAY NIGHT. HIGH PRESSURE AND MOSTLY TRANQUIL  
WEATHER WILL THEN RETURN FOR THE END OF THE WEEK AND EARLY THIS  
WEEKEND BEFORE ANOTHER STORM SYSTEM APPROACHES BY SUNDAY.  
 

 
   
NEAR TERM /UNTIL 6 AM TUESDAY MORNING/
 
 
745PM UPDATE...JUST SOME MINOR TWEAKS TO TEMPERATURES AND SKY  
COVER OVER THE NEXT FEW HOURS AS SCATTERED SHOWERS CONTINUE TO  
WIND DOWN THIS EVENING. THE REST OF THE GOING FORECAST LOOKS TO  
BE ON TRACK.  
 
PREVIOUSLY...  
 
A WEAK UPPER LEVEL WAVE CROSSES THE REGION THIS EVENING AND  
TONIGHT WITH DIURNALLY DRIVEN CONVECTIVE SHOWERS THIS AFTERNOON  
GRADUALLY WANING AFTER SUNSET. WHILE SHOWERS HAVE HAD A TOUGH  
TIME STANDING UP THIS EVENING AN ISOLATED THUNDERSTORM CAN'T BE  
RULED OUT ENTIRELY WHICH COULD BRING GUSTY WINDS TO NEAR 30 MPH  
AND SMALL HAIL. TONIGHT, THE WAVE MOVES ON WITH NICE CLEARING  
BEHIND IT, WHICH COMBINED WITH WEAK HIGH PRESSURE AT THE SURFACE  
WILL LEAD TO NICE RADIATIONAL COOLING AND PATCHY VALLEY FOG  
TONIGHT WITH LOWS IN THE 30S FOR MOST LOCATIONS.  
 

 
   
SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/
 
 
ANOTHER UPPER LEVEL WAVE CROSSES TOMORROW AS ATTENDANT LOW  
PRESSURE OVER QUEBEC PUSHES A COLD FRONT ACROSS NEW ENGLAND.  
THUS ANOTHER ROUND OF RAIN SHOWERS IS EXPECTED TOMORROW, MOSTLY  
OVER THE MOUNTAINS CLOSER TO PARENT FORCING. STEEPENING LAPSE  
RATES ALOFT WITH THE WAVE MAY PRODUCE ISOLATED THUNDERSHOWERS  
DURING THE AFTERNOON AS WELL. OTHERWISE, WINDS WILL INCREASE OUT  
OF THE SOUTHWEST IN THE MORNING AND BACK TO THE WEST THROUGH THE  
DAY AS THE COLD FRONT CROSSES... WITH WIND GUSTS UP TO AROUND 30  
MPH. TEMPERATURES WILL CLIMB TO NEAR 70 OVER THE LOWER  
ELEVATIONS, BUT BE MORE SUBDUED IN THE 50S AND LOW-60S OVER THE  
MOUNTAINS WHERE RAIN AND CLOUDS ARE EXPECTED.  
 

 
   
LONG TERM /TUESDAY NIGHT THROUGH MONDAY/
 
 
OVERVIEW: AN UPPER LEVEL TROUGH AND SURFACE CYCLONE WILL BRING  
WIDESPREAD PRECIPITATION IN THE FORM OF RAIN AND SNOW TO THE  
REGION WEDNESDAY AND WEDNESDAY NIGHT. GUSTY WINDS WILL ALSO BE  
POSSIBLE WEDNESDAY AFTERNOON AND EVENING, ESPECIALLY ALONG THE  
COAST. WEAK HIGH PRESSURE WILL KEEP THE WEATHER MOSTLY QUIET FOR  
THE END OF THE WEEK AND THE BEGINNING OF THE WEEKEND BEFORE  
ANOTHER FRONTAL SYSTEM ARRIVES LATE THIS WEEKEND WITH INCREASED  
PRECIPITATION CHANCES RETURNING. HIGH TEMPERATURES WILL  
GENERALLY BE AT OR BELOW NORMAL EARLY IN THE PERIOD BEFORE  
RETURNING TO ABOVE NORMAL BY THE WEEKEND.  
 
IMPACTS: SLIPPERY TRAVEL CONDITIONS WILL BE POSSIBLE ACROSS THE  
NORTH AND HIGHER ELEVATIONS, MAINLY WEDNESDAY NIGHT THROUGH THURSDAY  
MORNING DUE TO WET SNOW ACCUMULATIONS. ALONG THE COAST, GUSTY WINDS  
MAY BE CAPABLE OF BLOWING AROUND LIGHT WEIGHT UNSECURED OBJECTS ON  
WEDNESDAY AND WEDNESDAY NIGHT.  
 
FORECAST DETAILS: AN UPPER LEVEL TROUGH WILL MOVE THROUGH THE UPPER  
GREAT LAKES ON WEDNESDAY MORNING BEFORE PASSING THROUGH NORTHERN NEW  
ENGLAND ON THURSDAY. A WARM FRONT WILL FORM AND MOVE THROUGH  
SOUTHERN NEW HAMPSHIRE BEFORE STALLING ON WEDNESDAY MORNING,  
WHICH WILL ALLOW TEMPERATURES TO QUICKLY RISE ACROSS SOUTHERN  
LOCATIONS AND PROVIDE SOME CONVECTIVE INSTABILITY. WHILE SEVERE  
WEATHER IS UNLIKELY, DID ADD A SLIGHT CHANCE OF THUNDER FOR  
THESE LOCATIONS WITHIN THIS FORECAST PACKAGE. DURING THIS SAME  
TIME PERIOD, A SURFACE CYCLONE WILL FORM AND MOVE ACROSS THE  
OHIO RIVER VALLEY BEFORE QUICKLY MOVING TO THE NORTHEAST. THE  
PLACEMENT AND STRENGTH OF THE UPPER LEVEL TROUGH WILL ULTIMATELY  
HAVE THE LARGEST IMPACT ON THE TRACK OF THE SURFACE CYCLONE,  
WHICH WILL PLAY A LARGE ROLE IN PRECIPITATION TYPES.  
DETERMINISTIC AND ENSEMBLE GUIDANCE HAS BEEN TRENDING TO KEEP  
THE TROUGH LESS AMPLIFIED, WHICH HAS ALLOWED FOR A EASTWARD  
SHIFT IN THE SURFACE CYCLONE. LOOKING MORE CLOSELY, THERE IS  
DECENT CLUSTERING WITHIN INDIVIDUAL LOW LOCATION MEMBERS OF THE  
ECMWF, CMC, AND GEFS JUST OFFSHORE INTO THE WESTERN GULF OF  
MAINE. THE GEFS CONTINUES TO BE THE FURTHEST EAST, WHICH WOULD  
FAVOR A COLDER SOLUTION.  
 
THIS EASTWARD TREND IN ENSEMBLE CLUSTERINGS CONTINUES TO INCREASE  
CONFIDENCE FOR ACCUMULATING SNOW ACROSS THE MOUNTAINS AND FAR NORTH.  
WHILE THIS WILL LIKELY BE ANOTHER ELEVATION DEPENDENT SYSTEM, THERE  
IS THE POTENTIAL FOR AT LEAST SOME WET SNOW FLAKES TO MIX IN ACROSS  
VALLEY LOCATIONS, ESPECIALLY WEDNESDAY NIGHT AS THE DEPARTING LOW  
PULLS DOWN COLDER AIR FROM THE NORTH. ENSEMBLE MEANS SHOW GENERALLY  
A 20-30 PERCENT CHANCE FOR AT LEAST ONE INCH OF SNOW AS FAR SOUTH AS  
LEWISTON, WITH CATEGORICAL PROBABILITIES ACROSS THE NORTH. THESE  
PROBABILITIES THEN DROP OFF RATHER QUICKLY WHEN EXAMINING THE  
CHANCES FOR AT LEAST 3 AND 6 INCHES AND THEY BECOME  
SIGNIFICANTLY MORE ELEVATION DEPENDENT. IT IS IMPORTANT TO NOTE  
THAT THESE ARE BASED ON THE ASSUMPTION OF A 10:1 SNOW TO LIQUID  
RATIO, WHERE IN REALITY THEY WILL LIKELY BE LOWER GIVEN  
MARGINAL BOUNDARY LAYER TEMPERATURES. AS A RESULT, KEPT BOTH THE  
HIGHEST CHANCES FOR SNOW AS WELL AS THE HIGHEST SNOW  
ACCUMULATIONS ACROSS THE MOUNTAINS AND ALONG THE INTERNATIONAL  
BORDER. AS THE CYCLONE MAKES ITS CLOSEST APPROACH TO THE REGION,  
GUSTY WINDS WILL ALSO BE POSSIBLE AS THE PGF INCREASES,  
ESPECIALLY ALONG THE COAST WHERE THEY MAY GUST UP TO 35-40 MPH  
OR SO. TOTAL QPF LOOKS TO RANGE FROM AROUND ONE THIRD OF AN INCH  
TO ONE INCH, WITH LOCALLY HIGHER AMOUNTS POSSIBLE ACROSS THE  
WHITE MOUNTAINS.  
 
THE SYSTEM WILL LIKELY SLOW DOWN AND MAYBE EVEN STALL OVER SOUTHERN  
QUEBEC AND NOVA SCOTIA ON THURSDAY WITH CYCLONIC FLOW OVERHEAD  
ALLOWING FOR CONTINUED CHANCES FOR UPSLOPE SNOW AND RAIN  
SHOWERS LIKELY. THURSDAY WILL BE A SIGNIFICANTLY COOLER DAY WITH  
HIGH TEMPERATURES ONLY RANGING FROM THE 30S ACROSS THE NORTH TO  
THE 40S ELSEWHERE. A FEW LOCATIONS ACROSS THE FAR NORTH MAY  
STRUGGLE TO BREAK THE FREEZING MARK. IN ADDITION, GUSTY  
NORTHWESTERLY WINDS WILL KEEP WINDCHILL VALUES INTO THE 20S AND  
30S FOR MUCH OF THE DAY. UPPER LEVEL RIDING WILL MOVE ACROSS NEW  
ENGLAND ON FRIDAY AND SATURDAY, ALLOWING TEMPERATURES TO  
MODERATE AND KEEP THE WEATHER MOSTLY BENIGN. SOME UPSLOPE  
SHOWERS WILL STILL BE POSSIBLE ACROSS THE FAR NORTH AND  
MOUNTAINS THOUGH, ESPECIALLY ON FRIDAY. ANOTHER TROUGH AND AREA  
OF LOW PRESSURE MAY TRACK THROUGH THE REGION LATE THIS WEEKEND  
AND EARLY NEXT WEEK BRINGING ANOTHER CHANCE FOR WIDESPREAD  
PRECIPITATION.  
 

 
   
AVIATION /00Z TUESDAY THROUGH SATURDAY/
 
 
SHORT TERM...VFR PREVAILS THROUGH TOMORROW WITH A SMALL CHANCE  
OF BRIEF MVFR IN -SHRA THIS EVENING AND AGAIN TOMORROW, MOST  
LIKELY FOR NORTHERN TERMINALS DURING THE AFTERNOON. PATCHY  
VALLEY FOG MAY IMPACT VALLEY SITES LIKE HIE/LEB/CON TONIGHT.  
SOUTHWEST WINDS GUST TO NEAR 25 KTS TOMORROW BEFORE BACKING TO  
THE WEST LATE IN THE DAY.  
 
LONG TERM...MVFR/IFR CONDITIONS LIKELY ON WEDNESDAY AND WEDNESDAY  
NIGHT DUE TO LOW CEILINGS, GUSTY WINDS, AND WIDESPREAD  
PRECIPITATION. THERE WILL BE THE POTENTIAL FOR AN ISOLATED  
THUNDERSTORM, ESPECIALLY ACROSS SOUTHERN NEW HAMPSHIRE TERMINALS  
SUCH AS KMHT. ACROSS NORTHERN TERMINALS, RAIN WILL LIKELY MIX WITH  
OR CHANGE TO HEAVY WET SNOW ON WEDNESDAY NIGHT. MVFR/VFR CONDITIONS  
POSSIBLE ON THURSDAY ACROSS SOUTHERN TERMINALS AS PRECIPITATION  
GRADUALLY ENDS BUT ACROSS NORTHERN AND MOUNTAIN TERMINALS UPSLOPE  
SHOWERS OF RAIN AND SNOW WILL LIKELY CONTINUE. NORTHWESTERLY WINDS  
MAY GUST UP TO 35 KTS, ESPECIALLY ALONG THE COAST AND HIGHER  
ELEVATIONS.  
 

 
   
MARINE
 
 
SHORT TERM...QUIET OVER THE WATERS THROUGH TONIGHT, THEN SOUTH  
WINDS INCREASE DURING THE DAY TOMORROW GUSTING TO NEAR 25 KTS.  
SEAS WILL LIKEWISE INCREASE TO 3-5 FT BY TOMORROW NIGHT.  
 
LONG TERM...SCA CONDITIONS LIKELY LATE WEDNESDAY AND WEDNESDAY  
NIGHT AS SOUTHERLY WINDS BECOME MORE WESTERLY AND GUST UP TO 25 KTS  
AS SEAS BUILD TO 4-6 FEET. GALE CONDITIONS ARE THEN POSSIBLE ON  
THURSDAY BEHIND A SURFACE CYCLONE AS WESTERLY WINDS GUST UP TO 40  
KTS WITH SEAS OF 4-7 FEET. WIDESPREAD RAIN IS EXPECTED WEDNESDAY AND  
WEDNESDAY NIGHT WITH AN ISOLATED THUNDERSTORM ALSO POSSIBLE.  
 

 
   
FIRE WEATHER
 
 
A BRIEF PERIOD OF ELEVATED FIRE WEATHER DANGER IS EXPECTED  
TOMORROW AS A DRY SOUTHWEST WIND DEVELOPS AHEAD OF A CROSSING  
WAVE. DURING MID- TO LATE-MORNING, WE'LL MIX OUT THROUGH THE LOW  
LEVELS AND LEAD TO HUMIDITY DROPPING TO 25-30 PERCENT FOR MUCH  
OF THE LOWER ELEVATIONS COINCIDING WITH WIND GUSTS AROUND 25-30  
MPH. FURTHER NORTH AND INTO WESTERN MAINE, RAIN AND CLOUDS WILL  
KEEP HUMIDITY HIGHER WITH LOWER FIRE WEATHER DANGER. HUMIDITY  
WILL RECOVER NICELY TOMORROW NIGHT, THEN WETTING RAINS ARE  
POSSIBLE FOR MUCH OF THE REGION WEDNESDAY INTO WEDNESDAY NIGHT.  
 

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

 
 

 
SYNOPSIS...CASEY/TUBBS  
NEAR TERM...CASEY/WATSON  
SHORT TERM...CASEY  
LONG TERM...TUBBS  
AVIATION...CASEY/TUBBS  
MARINE...CASEY/TUBBS  
FIRE WEATHER...  
 
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