Area Forecast Discussion
Issued by NWS Portland, ME

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000
FXUS61 KGYX 312309
AFDGYX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAY ME
609 PM EST SAT JAN 31 2015

.SYNOPSIS...
COLD HIGH PRESSURE MOVES IN THROUGH SUNDAY. ANOTHER LOW WILL
TRACK SOUTH OF NEW ENGLAND ON MONDAY...POTENTIALLY BRINGING
SIGNIFICANT SNOW TO THE REGION. HIGH PRESSURE WILL FOLLOW MIDWEEK.
LOW PRESSURE WILL PASS BY TO OUR SOUTH ON THURSDAY.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
6PM UPDATE... WINDS ARE BEGINNING TO DECOUPLE IN ISOLATED VALLEYS
AND HAVE ADJUSTED WINDS SLIGHTLY DOWNWARD OVERNIGHT. CLEAR SKIES
WILL STILL RESULT IN VERY COLD TEMPERATURES WHICH WILL KEEP WIND
CHILLS LOW DESPITE LOWER WIND SPEEDS.

THE LAST RADAR ECHOES OF THIS SYSTEM ARE FADING OVER PENOBSCOT BAY
THIS AFTERNOON. AND SKIES HAVE CLEARED ACROSS MOST OF THE REST OF
THE CWA. THE GUSTY NW WINDS WILL START TO DIMINISH AROUND
SUNSET...AS WILL THE BLOWING SNOW. WILL SEE SOME GUSTY WINDS INTO
THE EVENING...BUT SHOULD BECOME LIGHT ACROSS THE AREA BY MIDNIGHT.
A VERY WEAK WAVE TRACKS SE THRU THE AREA AFTER MIDNIGHT AND
SPREADS SOME CLOUDS AND MAYBE A FEW FLURRIES IN THE MTNS OF NH.
OTHERWISE CAA SHOULD BRING MINS WELL DOWN INTO THE SINGLE DIGITS
ON THE COAST...AND SINGLE DIGITS BLO ZERO IN THE MTNS...THIS
COMBINED WITH WINDS UP TO 10 MPH WILL PRODUCE WINDCHILLS BLO ZERO
NEAR NEAR THE COAST...-10 TO -20 IN NRN NH...AND -20 TO -30 IN
THE WRN ME MTNS. THEREFORE./..HAVE DROPPED THE WIND CHILL ADV IN
NRN NH...BUT KEPT IT GOING IN THE ME MTNS...WHERE IT WILL BE A
LITTLE COLDER...AND WINDS WILL BE A LITTLE STRONGER.

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/...
SFC HIGH NOSES IN FROM THE WEST ON SUNDAY...AND IT SHOULD BE
GENERALLY SUNNY WITH HIGHS MOSTLY IN THE TEENS...MAYBE REACHING 20
ON THE COAST AND SRN NH...AND PROB STUCK IN THE SINGLE DIGITS IN
THE MTNS. CIRRUS SHOULD BEGIN TO THICKEN IN SRN AND WRN ZONES
LATE IN THE DAY.

SUNDAY NIGHT WILL START OFF CLEAR IN THE NE AS CLOUDS OVERSPREAD
THE CWA FROM THE SW IN ADVANCE OF THE NEXT SYSTEM. SOME RAD
COOLING EARLY IN THE N WILL ALLOW TEMPS TO SRO[ HERE...AND THEN NE
FLOW PICKS UP UP LATE WHICH WILL ADVECT COLDER AIR IN AS WELL.
LOWS AGAIN WILL GENERALLY BE BELOW ZERO ACROSS THE ENTIRE
CWA...ALTHOUGH MAYBE LOW SINGLE DIGITS NEAR THE COAST. LIGHT SNOW
WILL MOVE IN AFTER MIDNIGHT INTO SRN AND WRN NH...REACHING WRN ME
AROUND DAYBREAK. NOT MUCH IN THE WAY OF ACCUMULATION IN THIS
PERIOD...MOST OF THAT WILL HOLD OFF UNTIL MONDAY.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
FOCUS IN THE EXTENDED WAS MAINLY ON THE BEGINNING OF THE
PERIOD...AND S/WV TROF LIFTING OUT OF THE MID MS VALLEY. MID LEVEL
LOW CENTERS INITIALLY FILL ON APPROACH TO THE EAST COAST...BUT
BEGIN TO DEEPEN ONCE OVER THE TIGHT BAROCLINIC ZONE JUST OFFSHORE.
H7 CLOSES OFF AGAIN IN THE GULF OF ME...WHICH WOULD BE A FAVORABLE
LOCATION FOR ENHANCED FORCING FOR ASCENT ACROSS MOST OF THE
FORECAST AREA.

CONFLUENT FLOW AT H5 ACROSS SRN QUEBEC WILL HELP TO REINFORCE SFC
HIGH PRES N OF THE REGION INTO MON. THIS LEADS ME TO BELIEVE THIS
STORM HAS MORE RISK OF TICKING S THAN MUCH MORE N AT THIS
TIME...AND ALSO THAT THE NRN EDGE OF THE QPF WILL FEATURE A SHARP
GRADIENT. MODEL SPREAD IS PRETTY LOW AT THIS RANGE...WITH
NAM...GFS...AND CMC ALL NEAR 1 INCH QPF FOR COASTAL ME AND SRN NH.
THE ECMWF IS THE /MINOR/ OUTLIER WITH QPF CLOSER TO 0.60 INCHES.
OPTED TO BLEND EVENLY BETWEEN AVAILABLE GUIDANCE...INCLUDING
WPC...WITH A 2 TIMES WEIGHTING OF THE ECMWF. RESULTANT QPF HAS
ABOUT 0.75 INCHES QPF FROM KCON THRU KPWM TO KRKD. THIS TAPERS TO
ONLY 0.10 TO 0.25 INCHES ACROSS THE INTERNATIONAL BORDER.
HOWEVER...I WILL ADMIT THAT THIS QPF FORECAST MAY EVEN BE ON THE
LIGHT SIDE...ESPECIALLY IF 00Z MODEL SUITE CONTINUES TRENDING
TOWARDS A LITTLE MORE ROBUST AMPLIFICATION IN THE GULF OF ME.

SIMILAR TO THE LAST TUE BLIZZARD THE COLD AIR IS QUITE DEEP IN THE
LOW LEVELS. COLUMN SHOULD BE WELL MIXED THRU 950 MB. HOWEVER
UNLIKE TUE THE CORE OF THE LOW LEVEL JET IS MUCH WEAKER AND
FURTHER S. COULD SEE THE POTENTIAL FOR 3O TO 35 KT GUSTS...BUT
MAINLY CONFINED TO THE IMMEDIATE COAST.

THE SNWFL FORECAST WAS A LITTLE TRICKY...AS THE NRN EDGE OF THE 6
INCH CONTOUR WILL RESIDE IN THE FORECAST AREA
SOMEWHERE...IMPACTING HEADLINE DECISIONS. TAKING A LOOK AT THE
CIPS ANALOG GUIDANCE...THE MEAN COOP SNWFL GUIDANCE FAVORS A SWATH
OF SIGNIFICANT SN NEAR THE NH/MA BORDER. THE 25TH PERCENTILE COOP
GUIDANCE RANGED FROM 2 TO 4 INCHES ACROSS SRN NH...WITH 75TH
PERCENTILE GUIDANCE 12+. THIS HIGHLIGHTS SOME OF THE UNCERTAINTY
REGARDING SUBTLE CHANGES IN STORM TRACK...BUT TRENDS SUGGEST 25TH
PERCENTILE SNWFL BASED ON CIPS ANALOGS ARE LESS LIKELY. WPC WINTER
WX DESK PERCENTILE GRAPHICS SEEM MORE IN LINE WITH OUR
THINKING...PUTTING LOWER AND UPPER BOUNDS FOR THE SRN FORECAST
AREA BETWEEN 6 AND 15 INCHES. THE ISSUES ARISE FOR NRN
ZONES...WHERE TOTALS COULD RANGE FROM NOTHING TO AS MUCH AS 4 TO
6 INCHES...ALL FROM MINOR SHIFTS IN TRACK. ONE MITIGATING FACTOR
FOR LOWER QPF AMOUNTS ON THE NRN EDGE OF THE FORECAST ARE SN
RATIOS. MODEL FORECAST SOUNDINGS INDICATE A DEEP DENDRITIC GROWTH
ZONE /DGZ/ ACROSS THE ENTIRE FORECAST AREA. IN SOME CASES DURING
PEAK SATURATION THE DGZ IS AS DEEP AS 300 OR 400 MB. CASES SUCH AS
THIS OFTEN EXHIBIT EXTREMELY HIGH SN RATIOS...GREATER THAN 20:1 AT
TIMES. AS LONG AS THIS LAYER REMAINS SATURATED SNWFL RATIOS WILL
MORE THAN MAKE UP FOR MEAGER QPF. LOCATIONS CLOSER TO THE LOW PRES
WITHOUT QPF WORRIES MAY SEE DOUBLE DIGIT SNWFL FROM QPF 0.75
INCHES OR LESS. IN ADDITION...STRONG ISENTROPIC LIFT IS FORECAST
TO OCCUR DURING THE DAY MON. 40 TO 45 KTS OF LIFT IS LIKELY TO
OCCUR...LIFTING PARCELS FROM 950 MB THRU 800 MB OVER A SHORT
DISTANCE. SEEING THIS KIND OF SIGNAL SUGGESTS THAT SNWFL COMES IN
QUICKLY...AND WILL LIKELY BE HEAVY FOR A TIME DURING THE DAY. IT
IS DIFFICULT TO PIN DOWN AT THIS RANGE...BUT RATES ON THE ORDER OF
1 INCH OR MORE AN HOUR ARE POSSIBLE. WINTER STORM WATCHES HAVE
BEEN ISSUED FOR ALL ZONES S OF THE MOUNTAINS...WITH AREAS ALONG
THE ME COAST AND SRN NH MOST LIKELY TO SEE 6 OR MORE INCHES OF
SNWFL.

BEYOND MON AND MON NIGHT USED A MULTI-MODEL CONSENSUS FOR THE
FORECAST. THERE IS ANOTHER CHANCE OF SN MIDWEEK...AS A FAST MOVING
CLIPPER SYSTEM REDEVELOPS IN THE GULF OF ME. COLD HIGH PRES
REPLACES THAT DEPARTING STORM...WITH ANOTHER POSSIBLE COASTAL
STORM LATE WEEK ALONG THE ARCTIC FRONT.

&&

.AVIATION /23Z SATURDAY THROUGH THURSDAY/...
SHORT TERM...
GUSTY NW WINDS DIMINISH AROUND AND AFTER SUNSET WITH VFR HOLDING
INTO SUNDAY EVENING. KLEB/KMHT/KCON COULD SEE MVFR TO IFR CONDS
LATE SUN NIGHT IN SNOW.

LONG TERM...HIGH CONFIDENCE IN A PERIOD OF IFR OR LOWER CONDITIONS
FOR SRN NH AND COASTAL TERMINALS MON IN SNWFL. SOME UNCERTAINTY
REMAINS FOR KLEB AND KHIE FOR JUST HOW FAR N HEAVIER SNWFL MAKES
IT. COASTAL TERMINALS WILL ALSO SEE GUSTY NE WINDS AROUND 25 KTS
MON AND MON NIGHT. ANOTHER POSSIBLE SN EVENT MAY IMPACT THE AREA
MIDWEEK...BUT CONFIDENCE IS LOW AT THIS TIME.

&&

.MARINE...
SHORT TERM...GALES WILL CONTINUE THROUGH TONIGHT. SHOULD SEE WINDS
BEGIN TO DIMINISH AROUND AND AFTER MIDNIGHT. COLD AIR CONTINUES
TO MOVE OVER THE WATERS AND THE FZ SPRAY ADV WILL ALSO HOLD OVER
NIGHT...BUT WILL SEE A LITTLE BIT OF BREAK SUN INTO SUN
EVE...BEFORE WINDS START TO PICK UP AGAIN SUN NIGHT.


LONG TERM...LOW PRES PASSING NEAR THE GULF OF ME WILL BRING A
PERIOD OF GALES TO THE WATERS MON INTO TUE. WITH GALES CURRENTLY
IN EFFECT OPTED NOT TO PUT A WATCH UP TO AVOID CONFUSION.
HOWEVER...A WATCH/WARNING WILL LIKELY BE NEEDED IN FUTURE FORECAST
UPDATES. IN ADDITION...BITTERLY COLD TEMPS...WINDS...AND SEAS WILL
COMBINE TO PRODUCE A PERIOD OF MODERATE FREEZING SPRAY.

&&

.EQUIPMENT...
KRKD HAS A BAD WIND SENSOR.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...WINTER STORM WATCH FROM LATE SUNDAY NIGHT THROUGH MONDAY
     EVENING FOR MEZ012>014-018>028.
     WIND CHILL ADVISORY UNTIL 5 PM EST SUNDAY FOR MEZ007>009.
NH...WINTER STORM WATCH FROM LATE SUNDAY NIGHT THROUGH MONDAY
     EVENING FOR NHZ003>015.
MARINE...FREEZING SPRAY ADVISORY UNTIL 5 PM EST SUNDAY FOR ANZ150>154.
     GALE WARNING UNTIL 5 AM EST SUNDAY FOR ANZ150>154.

&&

$$
SYNOPSIS...
NEAR TERM...CURTIS
SHORT TERM...CEMPA
LONG TERM...LEGRO
AVIATION...
MARINE...
EQUIPMENT...



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