Area Forecast Discussion
Issued by NWS Portland, ME

Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KGYX 211432 AFDGYX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAY ME 932 AM EST SUN DEC 21 2014 .SYNOPSIS... HIGH PRESSURE BUILDS OVER NORTHERN MAINE SUNDAY...ALLOWING THE FLOW TO TURN ONSHORE. A WEAK WEATHER DISTURBANCE MAY TRIGGER SOME FLURRIES OR LIGHT SNOW OVER SOUTHERN REGIONS RIGHT THROUGH MONDAY. 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. && .NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
UPDATE... HAVE UPDATED GRIDS TO RAISE POPS FROM SLIGHT CHANCE/CHANCE TO CATEGORICAL...AT LEAST FOR THIS MORNING. LOW LEVEL MOISTURE CONTINUES TO DEPOSIT SNOW ACROSS SOUTHERN NH AND FAR WESTERN MAINE. WILL FORECAST 1 TO 2 INCHES OF SNOW FOR TODAY AS SOME AREAS WILL REMAIN NEAR A MILE VSBY IN SNOW. SOME HIGHER REFLECTIVITY RETURNS IN THE ROCHESTER NH AREA AS WELL WILL PINWHEEL SLOWLY TO THE NE. THIS IS IN ASSOCIATION WITH AN INVERTED TROUGH OVER SOUTHERN NEW ENGLAND AS OF 14Z WITH AN UPPER LEVEL LOW SLOWLY CROSSING THE FORECAST AREA TODAY AS WELL. NUMERICAL MODELS SHIFT PRECIP SOUTH AND EAST THIS AFTERNOON...WHICH IS IN DISAGREEMENT WITH THE CURRENT RADAR ANIMATIONS. OTHERWISE...JUST MINOR MODIFICATIONS TO THE REST OF THE GRIDED PACKAGE. PREV DISC... 615 AM UPDATE...JUST MADE SOME MINOR UPDATES TO SKY AND TEMPERATURES BASED ON CURRENT OBS AND TRENDS...AS STRATUS REMAINS ENTRENCHED ACROSS THE REGION. PREVIOUS DISCUSSION... LOW STRATUS BLANKETS THE CWFA AS A SURFACE HIGH PRESSURE IN SOUTHERN QUEBEC IS HELPING TO KEEP MOISTURE TRAPPED IN THE LOW LEVELS. A WEAK SHORTWAVE THAT IS PASSING OVER THE SOUTHERN NEW ENGLAND THIS MORNING AND THIS MAY HELP KICK OFF SOME LIGHT SNOW ACROSS THE FAR SOUTHERN AREAS OF NEW HAMPSHIRE AND PARTS OF SOUTHWEST MAINE...AS ON SHORE FLOW SUPPLIES THE LOW LEVEL MOISTURE THE LIFT FROM THIS WEAK SHORT MAY BE JUST ENOUGH TO PRODUCE SNOW SHOWERS HEAVY ENOUGH TO ACCUMULATE IN SOME AREAS. AS THIS WEAK WAVE MOVES EAST OUR FLOW...ALTHOUGH VERY WEAK...WILL TURN TO NORTHWESTERLY AND THIS MAY BE ENOUGH TO START CLEARING OUT SOME OF THE LOW STRATUS SUNDAY NIGHT.
-- End Changed Discussion --
&& .SHORT TERM /MONDAY/... FLOW WILL SWITCH BACK TO ON SHORE BY NOON ON MONDAY AND THIS WILL BRING LIGHT OCEAN EFFECT SNOW OR MAYBE EVEN SOME LIGHT RAIN OR EVEN FREEZING DRIZZLE INTO THE INTERIOR AS TEMPERATURES WILL HOVER CLOSE TO FREEZING AS YOU GET AWAY FROM THE COAST. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... MODELS CONTINUE TO TREND TOWARD UPSTREAM AND DOWNSTREAM BLOCKING...WITH AN EVENTUAL RETURN TO A +PNA PATTERN AT 500MB...WHICH WOULD SIGNAL COOLING LATE IN THE PERIOD. HOWEVER ALL THE ACTION WILL BE IN DAYS 3 TO 5 AS THE UPSTREAM DEVELOPS AND SENDS WAVES INTO TROUGH OVER CENTRAL CONUS...AMPLIFYING THE 500 MB FLOW. INITIALLY...WILL BE DEALING WITH SMALLER SCALE FEATURE AS INVERTED TROUGH OVER THE GULF OF ME WORK ITS WAY ONSHORE MON NIGHT AND WEAKENS. MAY BE ENOUGH DYNAMIC FORCING FOR ICE CRYSTALS INITIALLY...SO RAIN OR SNOW SHOWERS MOVE ONSHORE AND INLAND DURING THE EVENING...BUT COULD SEE IT TURN TO DZ/FZDZ AS WE WE JUST TRANSPORT WATER DROPLETS ONSHORE. WE MAINTAIN AN ONSHORE FLOW INTO TUESDAY...BUT IT LOOKS LIKE FORCING WILL BE LIMITED TO UPSLOPE...SO THINKING MORE IN THE WAY OF SHSN/SHRA/VERY LIGHT SNOW INLAND...WITH JUST CLOUDS ON THE COAST. SHOULD SEE TEMPS ON TUE WARM INTO THE UPPER 30S TO MID 40S. THE MAIN EVENT REMAINS THE IMPRESSIVE 500 MB TROUGH THAT DEVELOPS OVER THE CENTRAL CONUS MID WEEK...NOT SO MUCH IN THAT IT IS VERY DEEP...BUT MORE ITS AMPLITUDE AS IT EXTENDS FROM N OF THE GREAT LAKES SWD INTO THE GULF OF MEX....AND THEN TILTS VERY NEG AND LIFTS POLEWARD WED NIGHT AND THU. NOT SURE HOW MUCH AN EFFECT CONVECTIVE SCALING ISSUES ARE HAVING ON THE MODELS...BUT IT MAY BE HAVING SOME EFFECT ON THE FORECAST DETAILS...BUT PROB NOT THE GENERALITIES OF THE FORECAST. HOWEVER...00Z EURO AND GFS BOTH SHOW A WEAKER SFC LOW IN THE VCNITY OF THE GRT LAKES AND ST LAWRENCE VLY /ALTHOUGH IT DOES INTENSIFY FURTHER N AND E THAN PREV MODEL RUNS. STILL...AS THAT WAVE LIFTS NWD WILL SEE TRIPLE POINT DEVELOP OVER THE MID ATLANTIC WED EVE...AND LIFT NNE INTO THE CWA BY THU MORNING. THIS WILL CREATE A DEEP SOUTHERLY FLOW WHICH WILL CONNECT WITH GULF MOISTURE...ALLOWING FOR SIGNIFICANT RAINFALL...FROM LATE IN THE DAY WED...INTO EARLY THU MORNING. QPF LOOKS TO RUN AROUND 2-3 INCHES IN MANY SPOTS...BUT S-SE UPSLOPE AREAS OF THE FOOTHILLS AND MTNS COULD SEE AN INCH OR TWO MORE...SO THE THREAT OF BOTH FLASH AND MAINSTEM FLOODING IS A CONCERN...ESPECIALLY SINCE THIS WILL BE COMBINE WITH SIGNIFICANT SNOWMELT AS HIGHS RISE WELL INTO THE 40S WED..AND WILL LKLY STAY THERE WED NIGHT INTO THU. THERE IS STILL THE POTENTIAL FOR SOME STRONG GUSTS...BUT GIVEN WEAKER SYSTEM...THE WINDOW FOR OPPORTUNITY WILL BE LIMITED TO A FE HOURS AHEAD OF THE TRIPLE POINT PASSAGE...WHICH LOOKS TO BE WED EVE...AT LEAST FOR NOW. WITH ALL THAT SAID...WE ARE STILL DEALING WITH DAYS 4 AND 5 OF THE FORECAST...WITH THE POTENTIAL FRO SOME DEEP CONVECTION IN THE BASE OF THE TROUGH...SO FORECAST COULD CHANGE...BUT BOTH EURO AND GFS PICKED UP THE SIGNALS OF THIS SYSTEM EARLY...AND HAVE BEEN CONSISTENT ON THE WHOLE SO FAR. CHRISTMAS DAY WILL SEE RAIN ENDING FROM SW TO NE DURING THE MORNING...WITH SOME PARTIAL CLEARING POSSIBLE IN THE AFTERNOON...AND TEMPS IN THE 40S AGAIN. COOLER AIR WILL MOVE IN FROM THE SW THU NIGHT. FRI AND SAT LOOK MOSTLY DRY /OTHER THAN POSSIBLE UPSLOPE SHSN ON FRI/. HIGHS WILL CONTINUE TO RUN A FEW DEGREES ABV NORMAL. && .AVIATION /15Z SUNDAY THROUGH THURSDAY/... SHORT TERM...MVFR TO IFR CEILINGS WILL REMAIN OVER THE REGION THROUGH AT LEAST SUNDAY EVENING. CONDITIONS MAY IMPROVE A BIT SUNDAY NIGHT AS THE ON SHORE FLOW DRIFTING MOISTURE INLAND WILL GET SHUT OFF. CONDITIONS WILL NOT STAY UP LONG HOWEVER AS THE FLOW WILL SWITCH BACK TO ON SHORE ON MONDAY BRINGING ANOTHER ROUND OF MVFR TO IFR CEILINGS. LONG TERM...POSSIBLE PERIODS OF MVFR TO IFR MONDAY NIGHT AS INVERTED TROUGH MOVES INLAND. MVFR LIKELY TO HOLD TUESDAY INTO TUESDAY NIGHT...LOWERING TO IFR LATE TUESDAY NIGHT INTO THURSDAY MORNING IN RAIN...WITH INCREASING E-SE WINDS WEDNESDAY. && .MARINE... SHORT TERM...A FEW WIND GUSTS CONTINUE JUST BELOW 25 KTS THIS AFTERNOON...WITH WAVES 4` OR LOWER...THEREFORE NO FLAGS IN THE NEAR TERM. WINDS SHOULD CONTINUE TO SLOWLY DECREASE TONIGHT INTO TOMORROW FROM THE NORTHEAST. LONG TERM...HIGH PRESSURE WITH LIGHT AND FAIRLY CALM SEAS WILL PERSIST THROUGH THE PERIOD AND NO FLAGS ARE EXPECTED. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...NONE. NH...NONE. MARINE...NONE. && $$ JC

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.