Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 221111 AFDGYX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAY ME 611 AM EST MON DEC 22 2014 .SYNOPSIS... AN ONSHORE FLOW MAY PRODUCE SOME FLURRIES OR LIGHT SNOW MAINLY OVER SOUTHERN REGIONS RIGHT THROUGH TUESDAY. A SIGNIFICANT LOW PRESSURE 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 PM THIS EVENING/...
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608 AM...MINOR ESTF UPDATE TO 1ST PERIOD GRIDS TO INGEST CURRENT MESONET. AT 07Z...A 1032 MILLIBAR HIGH WAS CENTERED VICINITY OF THE GASPE PENINSULA. THE HIGH WILL GRADUALLY RETREAT TO THE NORTHEAST TODAY. COLD ONSHORE FLOW AROUND THIS HIGH WILL PRODUCE SOME SCATTERED OCEAN EFFECT SNOW SHOWERS OR FLURRIES TODAY MAINLY ACROSS SOUTHERN AND COASTAL SECTIONS TODAY.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/... SCATTERED SNOW SHOWERS AND FLURRIES WILL CONTINUE THROUGH TONIGHT BECAUSE OF THE PERSISTENT ONSHORE FLOW. COLD AIR DAMMING SHOULD KEEP THE COLUMN COLD ENOUGH TONIGHT FOR ANY LIGHT PRECIPITATION TO FALL LARGELY AS SNOW. BY TUESDAY MORNING...WARM AIR ADVECTION PRECIPITATION AHEAD OF THE MIDWEST STORM SYSTEM SHOULD BEGIN TO OVERSPREAD THE FORECAST AREA FROM SOUTH TO NORTH. THERE COULD BE A BRIEF PERIOD OF LIGHT FREEZING DRIZZLE OR RAIN AS THE WARMER AIR BEGINS TO OVERSPREAD THE AREA...AS MODELS HINT AT COLD AIR DAMMING ACROSS THE INTERIOR. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... EXTENDED PERIOD WX TO BE DRIVEN BY SERIES OF DOWNSTREAM BLOCKS OVER THE ATLANTIC AND EUROPE...WHICH WILL HELP BUILD RIDGING AND HIGHER AMPLITUDE THROUGH THE WEEK AND INTO EARLY NEXT WEEKEND...BEFORE THERE ARE SIGNS OF THE BLOCKING BREAKING DOWN AND ALLOWING COLDER AIR TO MOVE IN. WE START THE PERIOD DURING THE CHRISTMAS HOLIDAY PERIOD AND THE PREVIOUSLY ADVERTISED STORM SYSTEM THAT WILL THE CWA WED INTO THU. MOST OF THE SHORT TO MEDIUM RANGE MODELS HAVE INTRODUCED AN IMPORTANT CHANGE TO THE FORECAST...AND THAT ALLOWS THE FIRST NRN STREAM 500MB WAVE TO PASS BY WITH OUT MUCH INTERACTION WITH THE LARGER SCALE TROUGH...WHICH LINGERS OVER THE GULF STATES UNTIL EARLY WED MORNING. THIS WOULD MAKE FOR A LESS IMPRESSIVE SFC LOW THAT INTENSIFIES LATER AND FURTHER N...WHICH WOULD LIMIT THE DEVELOPMENT OF THE LOW LVL JET...AND THEREFORE BRING DOWN QPF...AND ALSO LOWER THE HTREAT FRO STRONG WINDS. THIS SCENARIO IS SUPPORTED BY THE 00Z EURO AND GFS...AND TO SOME DEGREE THE NAM...ALTHOUGH THAT REALLY HOLDS BACK THE 500 MB CLOSED LOW. THE 00Z CMC HEMI IS THE ONE MODEL THAT TEND TOWARD BETTER PHASING AND HOLDS ONTO A STRONGER SINGLE SFC LOW. THESE CHANGES IN THE MODELS MAY BE THE RESULT ONE OR ALL OF THE WAVES INVOLVED IN GETTING THIS STORM TOGETHER HAVE MOVES INTO A MORE WELL SAMPLED PART OF THE MODEL DOMAIN. THERES ALSO STILL THE ISSUE OF DEEP CONVECTION IN THE FORECAST TUE AFFECTING THE MODELS AS WELL. GIVEN ALL THAT WILL BE STICKING CLOSER TO THE GFS/EURO...AND BLENDING BACK IN SOME OF THE PREVIOUS FORECAST...PARTIALLY FOR THE SAKE OF CONTINUITY. OVERALL...THE SAME ISSUES PREVAIL FROM PREVIOUS FORECASTS...ALTHOUGH TO A LESSER DEGREE...AND IT WILL PRETTY MUCH BE PRECIPITATING /MOSTLY RAIN/ FROM TUESDAY RIGHT INTO CHRISTMAS MORNING. THE FIRST CHANGE IN THE FORECAST WILL BE THAT THE COLDER AIR WILL HANG ON LONGER...INTO WED MORNING. IN MOST PLACES TEMPS WILL BE ABV FREEZING THRU TUE NIGHT...BUT WE COULD SEE A PERIOD OF FZRA IN THE MTNS...WITH A TENTH OR TWO OF ICE ACCUMS BEFORE TEMPS RISE ABV THERE BY MIDDAY. S WINDS WILL PICK UP...BUT NOT UNTIL LATER IN THE DAY WED...AND WILL LKLY NOT BE AS GUSTY WED NIGHT...BUT COULD GUST TO 30 MPH OR IN THE W FLOW BEHIND THE LOW ON THU. QPF WAS LOWERED TOO...BUT STILL WILL SEE A PERIOD OF HEAVY RAIN...BUT THAT WILL PROBABLY BE LIMITED TO WED NIGHT. QPF AROUND 2 INCHES ACROSS THE CWA...LOWEST N OF THE MTNS AND HIGHEST IN THE UPSLOPE AREAS. ALSO...THE WARMER AIR WILL NOT COME IN AS QUICKLY AND THIS WILL HELP LIMIT SNOW MELT AND THUS MITIGATING THE FLOODING THREAT SOME. STILL...WILL SEE ENOUGH RAIN THAT SOME FLOODING PROBLEMS ARE POSSIBLE. FINALLY TEMPS WILL PUSH UP INTO THE 50S IN THE SRN ZONES...WITH THE WARMEST READINGS LKLY WED NIGHT INTO THU MORNING. ALTHOUGH IT COOLS DOWN SOMEWHAT BEHIND THEIS SYSTEM...TEMPS WILL REMAIN ABV NORMAL...BY 5-10F FRI AND SAT AS HIGH PRES BUILDS IN. NEXT CHC FOR ANY SIGNIF PRECIP WILL BE LATE IN THE WEEKEND. && .AVIATION /11Z MONDAY THROUGH FRIDAY/... SHORT TERM...MAINLY VFR THROUGH TONIGHT...HOWEVER THERE MAY BE BRIEFLY MVFR CONDITIONS IN SCATTERED SNOW SHOWERS SOUTHERN LOCATIONS. MVFR CONDS EXPECTED FOR TUE. LONG TERM...EXTENDED PERIOD OF FLIGHT RESTRICTIONS TUS NIGHT INTO THU MORNING. LOOK FOR IFR OR LOWER TUE NIGHT...WITH SOME IMPROVEMENT TO MVFR DURING THE DAY WED...AND A RETURN TO IFR WED NIGHT. EXPECT IMPROVEMENT TO VFR THU AFTERNOON...WHICH SHOULD HOLD THRU FRIDAY. && .MARINE... SHORT TERM...WINDS AND SEAS WILL REMAIN BELOW SCA CONDITIONS THROUGH LATE TONIGHT. AN SCA WILL LIKELY BE NEEDED BY TUESDAY IN INCREASING WINDS AND SEAS. LONG TERM...MODELS CONTINUE TO BACK OFF THE STRONG WINDS WED INTO THU...BUT STILL EXPECT A PERIOD OF GALES...POSSIBLE IN THE S FLOW LATE WED AND WED NIGHT...BUT MORE LKLY IN STRONG W FLOW THU INTO THU NIGHT. && .HYDROLOGY... MODELS CONTINUE TO BACK OFF ON RAINFALL TOTALS FOR THE CHRISTMAS EVE/EARLY CHRISTMAS MORNING EVENT...BUT AREA STILL AROUND 2 INCHES. HOPING THE SNOWPACK IN THE MOUNTAINS AND FOOTHILLS WILL TAKE IN SOME OF THE RAINFALL IN THAT AREA...BUT STILL EXPECT SOME RAPID RISES IN THE HEADWATERS. IN ANY CASE...WHILE THE THREAT OF FLOODING IS LOWER...IT STILL REMAINS A POSSIBILITY WED NIGHT INTO THU. && .TIDES/COASTAL FLOODING... ASTRONOMICAL TIDES ARE AT THEIR PEAK FOR THE MONTH. THIS...IN COMBINATION WITH STRONG SOUTHERLY GALES WILL LIKELY ALLOW FOR SOME STORM SURGE. WAVES PROB NOT QUITE AS HIGH AS PREV FORECASTS...MAYBE 10 TO 12 FT...BUT THERE IS SOME POTENTIAL FOR MINOR COASTAL FLOODING...WITH SPLASH OVER AND BEACH EROSION DISTINCT POSSIBILITY. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...NONE. NH...NONE. MARINE...NONE. && $$ ES

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