Area Forecast Discussion
Issued by NWS Portland, ME

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000
FXUS61 KGYX 212225
AFDGYX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAY ME
525 PM EST SUN DEC 21 2014

.SYNOPSIS...
AN ONSHORE FLOW MAY TRIGGER SOME FLURRIES OR LIGHT SNOW MAINLY OVER
SOUTHERN REGIONS RIGHT THROUGH TUESDAY. A SIGNIFICANT LOW
PRESSURE SYSTEM SYSTEM WILL GRADUALLY ORGANIZE WEDNESDAY...BEFORE
MOVING OVER THE GREAT LAKES. THIS COULD BRING WINDY CONDITIONS AND
THE POTENTIAL FOR HEAVY RAIN AROUND CHRISTMAS EVE INTO EARLY
CHRISTMAS MORNING. ANOTHER LOW PRESSURE SYSTEM WILL PASS BY TO OUR
NORTHWEST LATE IN THE WEEK AND EARLY NEXT WEEKEND.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
AREAS OF LIGHT SNOW WILL CONTINUE INTO THIS EVENING HOURS
ASSOCIATED WITH "OCEAN EFFECT" ONSHORE FLOW...AND ALSO DUE TO THE
PROXIMITY OF A WEAK MID LEVEL LOW. IN GENERAL...WILL BE LOWERING
POPS AS WE HEAD INTO THE LATE EVENING HOURS...WITH THE GREATEST
CHANCE OF A SNOW SHOWERS ALONG AND NEAR THE COASTLINE. THE BEACH
AREAS WILL NEED TO BE MONITORED HOWEVER...AS THERE IS SOME
INDICATION OF A WEAK NORLUN TROUGH OVER THE REGION.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/...
SCATTERED SNOW SHOWERS AND FLURRIES WILL CONTINUE RIGHT THROUGH
MONDAY NIGHT OVER SOUTHERN AREAS DUE TO A PERSISTENT NORTHEAST
FLOW OVER THE MOIST GULF OF MAINE. MESO MODELS WITHIN THE 12Z
MODEL SUITE CONTINUE TO HAVE A DIFFICULT TIME PICKING UP ON THIS
LOW LEVEL MOISTURE AND PRECIP. HAVE THEREFORE RAISED POPS ABOVE
ALL AVAILABLE GUIDANCE.

A COLD AIR DAMMING SIGNATURE WILL BE FORMING BY MONDAY NIGHT.
THEREFORE...THE PTYPE SHOULD BE ALL SNOW THROUGH THE SHORT TERM
PORTION OF THE FORECAST...BEFORE THE WARM AIR POURS INTO THE
REGION.

&&

.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
THE WEAK ONSHORE FLOW CONTINUES INTO TUESDAY WITH LOW LEVEL
MOISTURE DEEPEST ALONG THE COAST. ON TUESDAY THE WARMER ONSHORE
FLOW DEEPENS AS THE HIGH MOVES FURTHER OFFSHORE ALLOWING A
SOUTHEAST FLOW TO INCREASE...SO SCATTERED LIGHT INTERMITTENT
PRECIPITATION EXPECTED...MOSTLY IN THE FORM OF RAIN EXCEPT SOME
IN THE FORM OF LIGHT SNOW IN THE MOUNTAINS BEFORE CHANGING OVER TO
RAIN EVEN IN THOSE AREAS. THE MAIN EVENT WILL BE THE ONSET OF THE
HEAVIER PRECIPITATION LATE TUESDAY NIGHT AND ESPECIALLY CHRISTMAS
EVE WHERE THE RAIN WILL BECOME HEAVY AT TIMES AS A STRONG WARM
ADVECTION PATTERN DEVELOPS BEING ACCOMPANIED BY A STRONG LOW/MID
LEVEL JET. THE MAIN UPPER LOW PASSES WELL TO OUR WEST AS IT MOVES
THROUGH THE GREAT LAKES. QPF TOTALS FOR LATE TUESDAY INTO THURSDAY
COULD BE IN THE 2-4 INCH RANGE. DUE TO VERY WARM AIR THIS WILL BE
IN THE FORM OF RAIN EVEN IN THE MOUNTAINS. SOME FLOODING PROBLEMS
MAY ARISE IN THE HEADWATERS BY WEDNESDAY NIGHT OR THURSDAY DUE TO
THE COMBINATION OF SOME SNOWMELT AND THE HEAVY RAINS. ALL MODELS
AGREE ON MILD TEMPERATURES...USED A BLEND OF THE MODELS.

SYSTEM FINALLY EXITS TO THE NORTHEAST BY THURSDAY AFTERNOON AS A
DRY SLOT MOVES ACROSS THE AREA FOLLOWED BY A COLD FRONT WITH A
RETURN TO SEASONAL TEMPS FOR FRI.

ANOTHER SYSTEM WHICH WILL BE WEAKER WILL APPROACH FOR THE WEEKEND.
MODELS DIFFER IN RUN TO RUN CONTINUITY AND ALSO VARIANCES IN
TIMING, STRENGTH, AND POSITION OF THIS SYSTEM. FOR NOW WILL BROAD
BRUSH DUE TO ALL THE UNCERTAINTY AS WELL AS PTYPE.

&&

.AVIATION /00Z MONDAY THROUGH FRIDAY/...
SHORT TERM...MAINLY VFR THROUGH MONDAY NIGHT...HOWEVER THERE MAY
BE BRIEFLY MVFR CONDITIONS IN SCATTERED SNOW SHOWERS SOUTHERN
LOCATIONS.

LONG TERM...MVFR CONDS EXPECTED TUE AND THEN LOWERING TO IFR TUE
NIGHT AND LIFR CONDITIONS WED INTO THU. CONDITIONS IMPROVE BY LATE
THU TO VFR.

&&

.MARINE...
SHORT TERM...WINDS AND SEAS WILL REMAIN MOSTLY OUT OF THE
NORTHEAST THROUGH MONDAY NIGHT. WINDS AND SEAS WILL REMAIN BELOW
SCA CONDITIONS.

LONG TERM...STRONG LOW PRESSURE WILL MOVE WELL TO THE WEST AND
WILL CAUSE WINDS TO INCREASE TO GALES TUESDAY NIGHT THROUGH
WEDNESDAY WITH BORDERLINE STORM FORCE WIND GUSTS POSSIBLE
WEDNESDAY NIGHT. SEAS COULD BUILD IN EXCESS OF 15 FT OVER THE
OUTER WATERS BY WEDNESDAY NIGHT OR EARLY THURSDAY. GUIDANCE LOOKS
LOW ON BOTH WINDS AND SEAS WHICH IS TYPICAL FOR THESE TYPE OF
EVENTS.

&&

.HYDROLOGY...
MODELS CONTINUE TO BACK OFF ON RAINFALL TOTALS FOR
THE CHRISTMAS EVE/EARLY CHRISTMAS MORNING EVENT...BUT AREA STILL
IN THE 1 TO 3 INCH RANGE. HOPING THE SNOWPACK IN THE MOUNTAINS AND
FOOTHILLS WILL TAKE IN SOME OF THE 1 TO 2 INCH RAINFALL AMOUNTS IN
THAT AREA...BUT STILL EXPECTED RAPID RISES IN THE HEADWATERS. OVER
SOUTHERN LOCATIONS...2 TO 3 INCHES OF RAIN EXPECTED. IN ANY
CASE...FLOODING IS A DISTINCT POSSIBLY CHRISTMAS EVE AND CHRISTMAS
MORNING ASSOCIATED WITH THE HEAVY RAIN AND SNOWMELT.

&&

.TIDES/COASTAL FLOODING...
ASTRONOMICAL TIDES ARE AT THEIR PEAK FOR THE MONTH. THIS...IN
COMBINATION WITH STRONG SOUTHERLY DEVELOPING GALES (WITH POSSIBLE
STORM FORCE GUSTS) WILL LIKELY ALLOW FOR ABOUT A 1 FOOT STORM
SURGE. WITH BUILDING WAVES IN THE 15 FOOT RANGE...EXPECT A FEW
AREAS TO HAVE COASTAL FLOODING...SPLASH-OVER AND BEACH EROSION.

NART WAVE RUN-UP MATRICES ARE ALREADY PREDICTING THE POTENTIAL FOR
COASTAL FLOODING...OVERWASH AND EROSION ACROSS MOST LOCATIONS IN
MAINE AND NEW HAMPSHIRE BASED ON OUR CURRENT STORM SURGE AND WAVE
PREDICTIONS.

THE QUESTION IS HOWEVER...WHEN WILL THE PEAK WINDS AND SEAS
ARRIVE? RIGHT NOW IT IS TOO EARLY TO TELL IF THIS PERIOD OF
INCLEMENT WEATHER/OCEAN CONDITIONS WILL ARRIVE NEAR THE TIME OF
HIGH TIDE. THE MIDDAY TIDES ON CHRISTMAS EVE AND CHRISTMAS DAY ARE
THE HIGHEST AT 11 FEET...WHILE THE 1 AM CHRISTMAS MORNING HIGH
TIDE IS LOWER AT 10 FEET.

&&

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

&&

$$




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