Area Forecast Discussion
Issued by NWS Portland, ME

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FXUS61 KGYX 010346
AFDGYX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAY ME
1046 PM EST SAT FEB 28 2015

.SYNOPSIS...
HIGH PRESSURE WILL CREST OVER THE REGION THIS EVENING BEFORE
SHIFTING OFFSHORE SUNDAY. WEAK LOW PRESSURE CROSSES THE REGION
SUNDAY NIGHT...PRODUCING SOME ACCUMULATING SNOW...BEFORE MOVING
INTO THE CANADIAN MARITIMES ON MONDAY. HIGH PRESSURE CROSSES THE
AREA MONDAY NIGHT AND TUESDAY. LOW PRESSURE WILL MOVE OUT OF THE
GREAT LAKES TUESDAY NIGHT AND WILL TRACK NORTHEAST THROUGH THE ST
LAWRENCE VALLEY ON WEDNESDAY...BRINGING A ROUND OF MIXED
PRECIPITATION TO THE AREA. A COLD FRONT FOLLOWS WEDNESDAY NIGHT.
HIGH PRESSURE BUILDS IN FOR THE END OF THE WEEK.

&&

.NEAR TERM /TONIGHT/...
1045PM UPDATE...
HAVE MADE ONE MORE UPDATE FOR OVERNIGHT TEMPERATURES BASED ON
RECENT OBSERVATIONS. NORTHERN VALLEYS ARE ALREADY WELL BELOW ZERO
AND ARE NOW FORECAST TO FALL TO NEAR 20 BELOW TONIGHT. OTHER COLD
SPOTS OUTSIDE OF THE NORTH INCLUDE LEBANON... JAFFREY...
WISCASSET... AND SANFORD. THESE HAVE ALSO FALLEN TO AROUND ZERO
ALREADY AND HOURLY TEMPERATURE TRENDS HAVE BEEN UPDATED TO REFLECT
COLDER TEMPERATURES. OTHERWISE NO SIGNIFICANT CHANGES WERE MADE
TO THE FORECAST.

730PM UPDATE...
HAVE UPDATED OVERNIGHT TEMPERATURE FORECAST TO LOWER FORECAST
VALUES BY A FEW DEGREES PRIMARILY IN KNOWN COLD SPOTS AND ACROSS
SOUTHWEST NEW HAMPSHIRE. ALTHOUGH WINDS ARE MORE CALM TONIGHT THAN
LAST NIGHT... THERE ARE A FEW FACTORS WHICH GIVE REASON TO BELIEVE
WE WILL GENERALLY NOT FALL AS LOW TONIGHT AS LAST NIGHT. THE FIRST
IS THAT DEWPOINT VALUES ARE 5 TO 10 DEGREES WARMER THIS EVENING
THAN YESTERDAY EVENING... THOUGH ADMITTEDLY THESE ARE STILL
GENERALLY AROUND OR BELOW ZERO. AT THIS LEVEL OF DRYNESS IT DOES
NOT TAKE MUCH TO DIG BENEATH CURRENT DEWPOINTS ONCE COOLING
MAXIMIZES ESPECIALLY IN LOCAL VALLEYS. ANOTHER FACTOR IS AFTERNOON
TEMPERATURES STARTED OFF WARMER TODAY... MEANING TEMPERATURES HAVE
FURTHER TO FALL TONIGHT TO REACH THE SAME LEVELS. ONE FINAL FACTOR
IS THE EXPECTED EVENTUAL ARRIVAL OF SOME CIRRUS CLOUDS IN ADVANCE
OF THE APPROACHING SYSTEM BY MORNING. THIS COULD LIMIT COOLING
JUST BEFORE DAWN BY JUST A BIT. EVEN WITH ALL THESE LIMITATIONS...
STILL EXPECT A GOOD CHUNK OF THE AREA TO FALL BELOW ZERO AGAIN.
SHOULD MAKE A DECENT RUN AT ZERO IN PORTLAND AS WELL.

PRECIPITATION CHANCES WERE UPDATED AS WELL TO FURTHER CLARIFY WHEN
PRECIPITATION SHOULD BEGIN AND END ACROSS THE AREA NOT JUST
TONIGHT (NO PRECIPITATION TONIGHT) BUT ALSO TOMORROW AND SUNDAY
NIGHT WHEN CONFIDENCE IS HIGH THAT COASTAL AREAS WILL SEE SOME
MINOR ACCUMULATIONS.

ORIGINAL DISCUSSION...
THE COLDEST MONTH EVER FOR PORTLAND MAINE WILL BE IN THE BOOKS
SHORTLY. LAST NIGHT WAS NEAR RECORD COLD AS WELL...WITH A LOW OF
MINUS 7 IN THE FOREST CITY. THIS IS JUST SHY OF THE RECORD LOW OF
MINUS 9 SET BACK IN 1950.

WITH CLEAR SKIES AND LIGHT WINDS...EXPECT RADIATIONAL COOLING ONCE
AGAIN TONIGHT. WILL FORECAST ON THE LOWER END OF THE 12Z MODEL
SUITE WITH READINGS APPROACHING ZERO NEAR THE COASTLINE AND BELOW
ZERO OVER INTERIOR LOCATIONS. HIGH CLOUDS WILL BE ARRIVING LATER
TONIGHT. THIS MAY KEEP READINGS FROM TRULY BOTTOMING OUT AS WAS
THE CASE LAST NIGHT.

&&

.SHORT TERM /SUNDAY AND SUNDAY NIGHT/...
A BROAD AND WEAK AREA OF WARM AIR ADVECTION WILL ALLOW CLOUDS TO
THICKEN ON SUNDAY ACROSS THE FORECAST AREA. LIGHT SNOW WILL BREAK
OUT SUNDAY NIGHT AS THIS DEVELOPING MOISTURE INTERACTS WITH AN
APPROACHING UPPER LEVEL TROUGH.

SURFACE LOW PRESSURE WILL FORM IN THE GULF OF MAINE LATE SUNDAY
NIGHT...BUT LIKELY TOO LATE TO BRING APPRECIABLE MOISTURE AND
SNOWFALL TO THE REGION. NEVERTHELESS...THERE WILL BE TWO TO AS
MUCH AS FOUR INCHES OF SNOW OVER SOUTHERNMOST PORTIONS OF THE
FORECAST AREA. FURTHER TO THE NORTH...AS HAS BEEN THE CASE MUCH OF
THIS WINTER...LESS SNOW WILL FALL.

TEMPERATURES WILL BE MODERATING BUT STILL BELOW NORMAL FOR THIS
TIME OF THE YEAR.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
A SURFACE LOW EXITS RAPIDLY EAST INTO THE MARITIMES MONDAY WHILE
THE UPPER TROF MOVES THROUGH NORTHERN NEW ENGLAND. THE
PRECIPITATION WILL QUICKLY COME TO AN END EARLY MONDAY AS
DOWNSLOPING NORTHWEST WINDS KICK IN. HIGH PRESSURE BUILDS INTO THE
AREA MONDAY NIGHT AND TUESDAY. A FAST MOVING SHORT WAVE WITH
ASSOCIATED WARM AIR ADVECTION OVERRUNNING PRECIPITATION WILL MOVE
INTO THE AREA TUESDAY NIGHT IN THE FORM OF SNOW. SEVERAL INCHES OF
SNOW IS EXPECTED THROUGHOUT THE AREA. BY WEDNESDAY MORNING A BRIEF
CHANGEOVER TO A MIX OF RAIN OR SNOW SHOWERS OVER SOUTHERN AREAS IS
POSSIBLE BEFORE THE PRECIPITATION ENDS AS LOW AND MID LEVEL
TEMPERATURES MAY WARM ABOVE CRITICAL LEVELS. BY LATE WEDNESDAY
MORNING A COLD FRONT MOVES ACROSS THE AREA AND THEN OFFSHORE WITH
CLEARING BEHIND THE FRONT. HIGH PRESSURE BUILDS INTO THE REGION
FOR THURSDAY AND FRIDAY WITH FAIR CONDITIONS.

TEMPERATURES WILL GENERALLY REMAIN BELOW NORMAL FOR THE WEEK. USED
A BLEND OF THE MODELS FOR TEMPERATURES AND POPS.

&&

.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
SHORT TERM...VFR CONDITIONS DETERIORATING TO MVFR AND IFR SUNDAY
NIGHT IN LIGHT SNOW.

LONG TERM...
MVFR TO IFR CONDITIONS EARLY MONDAY WILL IMPROVE TO VFR BY LATE
MORNING MONDAY AND CONTINUE THROUGH TUESDAY. TUESDAY NIGHT MVFR TO
IFR CONDITIONS WILL DEVELOP AND CONTINUE INTO WEDNESDAY MORNING.
CONDITIONS WILL RETURN TO VFR BY WEDNESDAY AFTERNOON AND CONTINUE
THROUGH FRIDAY.

&&

.MARINE...
SHORT TERM...NO FLAGS. WINDS BELOW SCA THRESHOLDS AS WELL AS SEAS
IN THE SHORT TERM PORTION OF THE FORECAST.

LONG TERM...EXPECT TO NEED A STRONG SCA MONDAY AFTERNOON INTO
MONDAY NIGHT IN AN INCREASING WEST FLOW...WINDS DIMINISH LATE
MONDAY NIGHT. SCA MAY BE NEEDED AGAIN IN A SOUTH TO SOUTHWEST
FLOW LATE TUESDAY NIGHT AND WEDNESDAY.

&&

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

&&

$$

NEAR TERM UPDATE...KIMBLE
SHORT TERM...CANNON
LONG TERM...MARINE
AVIATION...CANNON/MARINE
MARINE...CANNON/MARINE


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