Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 010149 AFDGYX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAY ME 849 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/... 9PM UPDATE... EXPANDED THE WIND CHILL ADVISORY TO COOS COUNTY WHERE TEMPERATURES HAVE DROPPED TO 10 BELOW WITH NORTHWESTERLY WINDS CONTINUING THROUGH THE NIGHT. ELSEWHERE A FEW VALLEYS SUCH AS HIE HAVE DROPPED RAPIDLY AS WINDS BECAME CALM... WHILE THE SLIGHTLY HIGHER TERRAIN CONTINUES TO GUST. 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 /02Z SUNDAY 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. WIND CHILL ADVISORY UNTIL 5 PM EST SUNDAY FOR NHZ001-002. 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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