Area Forecast Discussion
Issued by NWS Portland, ME

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000
FXUS61 KGYX 171459 CCA
AFDGYX

AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE GRAY ME
959 AM EST WED DEC 17 2014

.SYNOPSIS...
A WEAK LOW PRESSURE SYSTEM WILL MOVE INTO THE GULF OF MAINE TODAY
AND START TO INTENSIFY THIS AFTERNOON...SPREADING RAIN AND SNOW
OVER THE REGION. BY THURSDAY MORNING THE LOW WILL BE OVER THE
CANADIAN MARITIMES AND WEAK HIGH PRESSURE WILL BUILD IN BEHIND IT.
THERE IS POTENTIAL FOR A WEAK COASTAL STORM SUNDAY INTO MONDAY
THAT MAY SPREAD SOME LIGHT SNOW INTO THE REGION. A MUCH STRONGER
STORM MAY AFFECT THE REGION MIDWEEK.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
UPDATE...HAVE INPUT LATEST OBS INTO THE FORECAST GRIDS...TRENDING
TOWARDS HI-RES MESOSCALE GUIDANCE FOR AFTERNOON TEMPS. IN GENERAL
THIS LEAVES MUCH OF THE AREA AOA FREEZING. FOR THIS REASON I WILL
DROP THE FZRA ADVISORY FOR THE NRN ZONES. WINTER WX ADVISORY
REMAINS IN PLACE MAINLY FOR A RASN MIX TURNING TO SNWFL LATER THIS
AFTERNOON. ATTM SN LEVELS ARE BETWEEN 3 AND 4 KFT...CONFIRMED VIA
DUAL-POL DATA AND VERTICALLY POINTED PLYMOUTH STATE RADAR. THIS
MATCHES KMWN OBSERVATIONS OF MODERATE SNWFL...BUT RNFL AT OTHER
REPORTING STATIONS. RADAR ALSO EXHIBITS A GOOD UPSLOPE
SIGNAL...WITH HIGHER DBZ VALUES ADJACENT TO TERRAIN. HAVE TRIED TO
PUT THIS IN THE QPF GRIDS USING MODELED MID LEVEL WINDS AS
FORCING. THIS WILL ALSO ASSIST IN SOME DYNAMIC COOLING AS AIR
RISES...WHICH SHOULD LEAD TO A FASTER CHANGEOVER BACK TO SNWFL IN
THE MTNS AS UPPER LOW STRENGTHENS AND TEMPS BEGIN COOLING ALOFT.

PREVIOUS DISCUSSION...LIGHT OVERRUNNING PRECIPITATION ONGOING
THIS MORNING AS A WARM FRONT LIFTS INTO THE AREA. WARM AIR ALOFT
MOVING OVER AREAS OF FREEZING AIR AT THE SURFACE HAS RESULTED IN
PATCHY FREEZING RAIN. OTHER LOCATIONS REMAIN ABOVE FREEZING. THIS
TREND WILL CONTINUE WITH A MIX OF PRECIPITATION EARLY THIS MORNING
ACROSS THESE AREAS BEFORE ALL BUT THE FAR NORTHERN AREAS CHANGE
OVER TO RAIN BY EARLY AFTERNOON. NORTHERN NH AS WELL AS NORTHERN
MAINE AND THE FOOTHILLS REMAIN UNDER FREEZING RAIN AND WINTER
WEATHER ADVISORIES THROUGHOUT THE MORNING.

LOW PRESSURE FORMS ALONG THE COAST TODAY...SETTING UP A BAROCLINIC
ZONE NEAR THE LAND/SEA INTERFACE. EXPECT UPPER 30S AND 40S
AREAWIDE TODAY WITH THE WARMEST TEMPERATURES JUST SOUTH OF THIS
BOUNDARY.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/...
THE COASTAL SURFACE LOW UNDERGOES RAPID DEEPENING... MOVING NE
AND DRAWING COLD AIR INTO NORTHERN NEW ENGLAND TONIGHT AND
THURSDAY. STRONG UPPER LEVEL CANON BALL LOW PRESSURE CLOSING OFF
OVER NORTHERN NEW ENGLAND WILL PROVIDE PLENTY OF LIFT AND DYNAMICS
FOR A HEAVY SNOWFALL AS IT EXITS THE AREA. IN FACT...NORTHERN
OXFORD...NORTHERN FRANKLIN AND CENTRAL SOMERSET REMAIN IN AN
ADVISORY THROUGH LATE VERY LATE TONIGHT AS THE DOMINANT P TYPE
CHANGES TO SNOW. THE POSSIBILITY OF STORM TOTAL AMOUNTS AT OR
ABOVE HALF A FOOT IS ESPECIALLY LIKELY THE FARTHER NE YOU GO.
SOMERSET COUNTY WILL LIKELY GET THESE AMOUNTS BUT WOULD NEED MORE
THAN 9" IN 24 HRS TO WARRANT A WARNING...AND CONFIDENCE WAS NOT
HIGH ENOUGH IN THIS SCENARIO.

RAIN AND SNOW SHOWERS TAPER OFF TOMORROW FROM SOUTHWEST TO
NORTHEAST AS THE LOW MOVES AWAY. TOTAL SNOWFALL AMOUNTS SHOULD BE
LESS THAN 2" SOUTH OF THE MOUNTAINS AS THE SNOW MIXES WITH RAIN AT
TIMES. HIGH TEMPERATURES SHOULD REACH THE 40S ALONG THE COAST AND
SOUTH WITH LOWER TO MID 30S NORTH AND EAST.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
START OFF THURSDAY NIGHT WITH LOW PRESSURE OVER THE CANADIAN
MARITIMES AND CONTINUING TO PULL OFF TO THE NORTHEAST. WEAK HIGH
PRESSURE AND FAIR WEATHER IS THEN EXPECTED FRIDAY THROUGH SUNDAY
MORNING. MODELS THEN DIVERGE AFTER SUNDAY. THE GFS AND GEM SHOW A
WEAK COASTAL LOW FOR SUNDAY NIGHT INTO MONDAY MORNING. THE 00Z GFS
NOW DEVELOPS THE LOW SOUTH AND EAST OF NOVA SCOTIA...PUTTING IT
TOO FAR OUT TO HAVE REALLY ANY IMPACT...BUT IT DOES HAVE AN
INVERTED TROUGH EXTENDING BACK TO MAINE THAT MAY BRING SOME LIGHT
SNOW TO THE AREA. THE GEFS MEAN SHOWS A SIMILAR SOLUTION AS THE
OPERATIONAL GFS WITH ONLY SOME VERY LIGHT SNOW. THE GEM DEVELOPS
THE LOW IN A SIMILAR LOCATION AS THE GFS...YET ITS A BIT FURTHER
EAST AND A LITTLE DEEPER. THE GEM ALSO SHOWS THE INVERTED TROF
REACHING BACK TO MAINE...BUT IT IS MORE AMPLIFIED THAN THE GFS.
DEPENDING ON THE AXIS OF THIS TROF...SOME AREAS WOULD SEE A
PLOWABLE SNOWFALL.

THE 00Z EURO COMPLETELY LOST THE SYSTEM AND INSTEAD DEVELOPS A
COASTAL LOW SOUTH OF LONG ISLAND MONDAY NIGHT AND TRACKS IT INTO
THE GULF OF MAINE BY EARLY TUESDAY MORNING. AT THIS TIME WITH THE
UNCERTAINTY...I WENT WITH JUST CHANCE POP FOR SUNDAY INTO MONDAY
AND SLIGHT CHANCE FOR MONDAY NIGHT INTO TUESDAY WITH STILL VERY
LOW CONFIDENCE IN THIS FORECAST.

FINALLY THE EURO AND GFS ARE STILL SHOWING A LARGE STORM FOR
CHRISTMAS EVE AND/OR CHRISTMAS DAY...HOWEVER WHERE IT WILL BE AND
TRACK TO IS STILL ANYONES GUESS. WE WILL CONTINUE TO MONITOR THE
POTENTIAL OVER THE NEXT SEVERAL DAYS. THERE IS ALREADY A LOT OF
RUN TO RUN DISCONTINUITY COMING WITH THE LOCATION OF THE LOW AND
THIS FAR OUT THAT IS EXPECTED...AS BOTH MODELS JUST WENT FROM A
COASTAL LOW WITH THE 12Z RUNS TO A WARM CUTTER WITH THE 00Z RUNS.
SO ALL WE CAN DO AT THIS TIME IS SEE HOW IT EVOLVES AS WE HEAD
INTO NEXT WEEK...AS THE ENERGY TO DEVELOP THIS STORM WILL NOT EVEN
BE SAMPLED WITH REAL DATA FOR SEVERAL DAYS YET.

&&

.AVIATION /15Z WEDNESDAY THROUGH SUNDAY/...
SHORT TERM...DETERIORATION TO IFR AND LIFR ALREADY OCCURRING IN
DRIZZLE...RAIN...SNOW...AND FOG. SLIGHT CHC FOR SOME FZRA AT KLEB
AND KHIE. THE IFR/LIFR PERSISTS THROUGH THE MORNING HOURS. SOME
IMPROVEMENT TO CEILINGS TO IFR THIS AFTERNOON BUT PRECIPITATION
EVENT CONTINUES AND WILL KEEP CONDITIONS FROM BECOMING MVFR.
EXPECT WORSENING CONDITIONS IN WIDESPREAD SNOW AS TEMPERATURES
DROP AT NIGHT.

LONG TERM...THURSDAY THROUGH SUNDAY...VFR CONDITIONS MOST AREAS
WITH POSSIBLE MVFR TO IFR CONDITIONS IN THE MOUNTAINS OVERNIGHT
THURSDAY. SHOULD BE MOSTLY VFR CONDITIONS THROUGH AT LEAST SUNDAY
MORNING AND THEN THERE IS POTENTIAL FOR SOME LOWER CONDITIONS DUE
TO A WEAK COASTAL LOW THAT COULD PROVIDE LIGHT SNOW OR WINTRY MIX
SUNDAY AFTERNOON THROUGH SUNDAY NIGHT.

&&

.MARINE...
SHORT TERM...SMALL CRAFT CONDITIONS CONTINUE TODAY BUT SHOULD BE
A QUIET PERIOD TONIGHT BEFORE WIND GUSTS PICKUP AGAIN TOMORROW
MORNING. WHETHER THIS WILL BE TAKEN ADVANTAGE OF OR THE ENTIRE
TIME FRAME BRIDGED WITH AN ADVISORY HAS BEEN LEFT TO THE
SUBSEQUENT SHIFT.

LONG TERM...SCA CONDITIONS EXPECTED THURSDAY NIGHT INTO EARLY
FRIDAY AS LOW PRESSURE DEPARTS TO THE NORTHEAST OF THE WATERS.
CONDITIONS WILL THEN SUBSIDE. SCA COULD BE POSSIBLE LATE SUNDAY
INTO MONDAY DEPENDING WHERE A COASTAL LOW PRESSURE TRACK AND
INTENSITY...HOWEVER AT THE MOMENT IT APPEARS IT WILL NOT INTENSIFY
UNTIL IT GETS UP INTO THE CANADIAN MARITIMES.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...WINTER WEATHER ADVISORY UNTIL 6 AM EST THURSDAY FOR MEZ008-009-
     014.
NH...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 7 PM EST THIS EVENING FOR ANZ150-
     152-154.

&&

$$

NEAR TERM...LEGRO



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