Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 191036 AFDGYX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAY ME 636 AM EDT SUN APR 19 2015 .SYNOPSIS... HIGH PRESSURE WILL BUILD EAST AND CREST ACROSS THE AREA LATE TODAY BEFORE SLIDING OFFSHORE TONIGHT. AN INCREASING EASTERLY ONSHORE FLOW WILL PROVIDE COOL AND DAMP WEATHER MONDAY WITH RAIN CHANCES INCREASING AHEAD OF AN APPROACHING LOW PRESSURE SYSTEM. SIGNIFICANT RAINFALL AND FLOODING...ALONG WITH COASTAL FLOODING FROM ASTRONOMICAL HIGH TIDES...ARE POSSIBLE WITH THIS SYSTEM MONDAY NIGHT AND TUESDAY. UNSETTLED WEATHER THEN LOOKS TO DOMINATE MID TO LATE WEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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633 AM...MINOR ESTF UPDATE TO REFLECT THE CURRENT SATELLITE TRENDS AND TO INGEST THE 10Z MESONET INTO NEAR TERM GRIDS. PREV DISC... AT 06Z...A 1030 MILLIBAR HIGH WS CENTERED ALONG THE ONTARIO-QUEBEC BORDER. A WEAK SURFACE TROUGH EXTENDED FROM THE GULF OF MAINE INTO EASTERN MAINE. CLOUDS WITH THIS TROUGH...AS WELL AS A FEW UPSLOPE CLOUDS ACROSS THE HIGHER TERRAIN...SHOULD EXIT THE REGION THIS MORNING AS THE SURFACE HIGH BUILDS EASTWARD. HIGHS TODAY SHOULD RANGE FROM AROUND 60 SOUTHERN AND INTERIOR SECTIONS...AS WELL AS THE CONNECTICUT VALLEY...WITH 50S ELSEWHERE. AS SURFACE GRADIENT RELAXES WITH BUILDING HIGH EXPECT WINDS TO SHIFT ONSHORE...WITH FALLING AFTERNOON TEMPERATURES NEAR THE COAST.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/... CLOUDS WILL GRADUALLY SPREAD NORTH AND EAST INTO THE FORECAST AREA TONIGHT AS THE SURFACE HIGH RETREATS INTO THE MARITIMES. THE ONSHORE FLOW MAY ALSO INTRODUCE SOME LOW MARINE STRATUS INTO COASTAL SECTIONS TOWARDS DAWN. SOME LIGHT OVERRUNNING RAIN COULD REACH FAR SOUTHWESTERN SECTIONS OF NEW HAMPSHIRE BY DAWN MONDAY...OTHERWISE A DRY FORECAST FOR TONIGHT. ON MONDAY...OVERRUNNING PRECIPITATION SPREADS NORTH AND EAST AND BECOMES STEADY AND HEAVIER TOWARDS EVENING IN ADVANCE OF A POTENT 50 KNOT LOW LEVEL JET. WHILE IT`LL BE WARM ENOUGH IN THE COLUMN FOR RAIN...ELEVATIONS ABOVE 2000 FEET IN NORTHERN NEW HAMPSHIRE AND THE WESTERN MAINE MOUNTAINS COULD SEE SEVERAL INCHES OF WET SNOW. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... NOT MUCH HAS CHANGED IN THE LAST 24 HOURS AS FAR AS THE MODEL CONSENSUS GOES WITH THE SETUP FOR POTENTIALLY HEAVY RAINFALL MONDAY NIGHT INTO TUESDAY. LOW PRESSURE WILL DEVELOP TO OUR SOUTH...AND A DEVELOPING COASTAL FRONT LOOKS TO ACT AS A FOCUS FOR HEAVY RAIN AS STRONG EASTERLY INFLOW OVERRUNS THE BOUNDARY. IN ADDITION...THIS DEEP SOUTHEASTERLY INFLOW IN THE LOWEST 4 KFT WILL UPSLOPE INTO THE WHITE MOUNTAINS AND THE MAINE FOOTHILLS AND WILL HELP TO WRING OUT THE MOISTURE. THEREFORE...THE THINKING IS THAT THERE SHOULD BE TWO RAINFALL MAXES...ONE IN THOSE UPSLOPE REGIONS AND ANOTHER ON THE COASTAL PLAIN OF MAINE TO THE WEST OF THE COASTAL FRONT. THESE AREAS SHOULD SEE 2 TO 2.5 INCHES OF RAIN WHILE BASIN AVERAGES ELSEWHERE SHOULD BE 1 TO 2 INCHES. THIS COMBINED WITH CONTINUED SNOWMELT...SOGGY GROUND...AND ALREADY RISING RIVERS AND STREAMS SHOULD PUSH SEVERAL NEAR OR OVER BANKFULL. URBAN AND POOR DRAINAGE FLOODING IS POSSIBLE AS WELL. THEREFORE...A FLOOD WATCH HAS BEEN ISSUED FOR MOST OF THE CWA FROM MONDAY EVENING THROUGH TUESDAY NIGHT. THE COLUMN MAY BE COLD ENOUGH ACROSS THE WESTERN MAINE MOUNTAINS...ESPECIALLY THE HIGHER ELEVATIONS...FOR A FEW INCHES OF WET SNOW MONDAY NIGHT. E/SE WINDS SHOULD BECOME QUITE GUSTY ON THE IMMEDIATE COAST MONDAY NIGHT...WITH GUSTS 30-40 MPH POSSIBLE THERE. THEREFORE A WIND- SWEPT RAIN LOOKS TO BE IN THE CARDS. MOST MODELS SHOW ELEVATED INSTABILITY DEVELOPING LATE MONDAY NIGHT INTO EARLY TUESDAY ACROSS SOUTHERNMOST ZONES...SO WE HAVE A CHANCE FOR THUNDER IN THE FORECAST DURING THAT TIME AS WELL. THE HEAVIEST RAINFALL SHOULD MOVE OUT AFTER MIDDAY TUESDAY...EARLIER ACROSS SW ZONES. WE/LL DRY OUT A BIT TUESDAY NIGHT INTO WEDNESDAY BEFORE THE NEXT SYSTEM BRINGS LIGHTER PRECIPITATION TO THE REGION ON THURSDAY. OVERALL...WITH UPPER LEVEL LOW PRESSURE LOOKING TO HANG AROUND THROUGH THE WEEKEND...THE FORECAST CALLS FOR CONTINUED COOLER AND OCCASIONAL WET WEATHER. NOT VERY PLEASANT...CONSIDERING SOME MODELS SAY THAT WE MAY NOT HAVE SEEN THE LAST SNOWFLAKE OF THE SEASON YET. && .AVIATION /12Z SUNDAY THROUGH THURSDAY/... SHORT TERM...VFR EXPECTED THROUGH SUNDAY NIGHT...WITH MVFR CIGS PSBL VCNTY OF THE COAST IN MARINE STRATUS AFT 10Z MONDAY. CONDS DETERIORATE TO IFR BY MONDAY AFTERNOON IN RAIN AND FOG WITH SE SFC WINDS NR THE COAST GUSTING UP TO 30 KT DURING THE AFTERNOON. LONG TERM...IFR OR LOWER CONDITIONS IN HEAVY RAIN IS LIKELY MONDAY NIGHT INTO TUESDAY. SOME IMPROVEMENT IS FORESEEN TUESDAY AFTERNOON...ESPECIALLY ACROSS SOUTHERN NH AND SOUTHERN ME. OCNL MVFR CONDITIONS WILL BE POSSIBLE THU WITH THE NEXT LOW PRESSURE SYSTEM. && .MARINE... SHORT TERM...QUIET THROUGH TONIGHT AS SURFACE HIGH BUILDS ACROSS THE WATERS. INCREASING ONSHORE FLOW MONDAY WITH STEADILY BUILDING SEAS AND WINDS GUSTING TO STRONG SMALL CRAFT BY AFTERNOON. LONG TERM...EASTERLY GALES ARE EXPECTED MONDAY NIGHT INTO TUESDAY WITH COASTAL LOW PRESSURE. THESE SHOULD BRING SEAS UP TO AT LEAST 15 FT ON THE OFFSHORE WATERS. SUBSIDING CONDITIONS ARE EXPECTED LATER TUESDAY INTO MIDWEEK. && .FIRE WEATHER... DRIER AIR WILL MOVE IN THROUGH TODAY. A SEA BREEZE DEVELOPS IN THE AFTERNOON TODAY... KEEPING HUMIDITY LEVELS HIGHER OVER THE COASTAL PLAIN. BUT TO THE WEST OF THE MOUNTAINS THE HUMIDITY WILL FALL BELOW 30 PERCENT IN THE AFTERNOON...BUT LIGHT WINDS SHOULD PREVENT ANY ELEVATED FIRE WEATHER CONDITIONS. ONSHORE FLOW ON MONDAY BRINGS MORE MOISTURE AND EVENTUALLY RAIN TO THE AREA. A SOAKING RAIN IS EXPECTED LATE MONDAY AND TUESDAY. && .HYDROLOGY... A WIDESPREAD 1 TO 2 INCHES OF RAIN IS EXPECTED FROM MONDAY AFTERNOON THROUGH TUESDAY. HOWEVER...GIVEN STRONG MOISTURE INFLOW...LOCALIZED AMOUNTS OF UP TO 3 INCHES COULD OCCUR. THIS WOULD LEAD TO FLOODING PROBLEMS...ESPECIALLY IN AREAS WHERE SNOW MELT IS STILL OCCURRING. A FLOOD WATCH HAS BEEN ISSUED. && .TIDES/COASTAL FLOODING... HIGHEST TIDE OF THE MONTH OCCURS TONIGHT AT 11.6 FEET MLLW IN PORTLAND. LIGHT WIND FLOW AT THE TIME SHOULD PREVENT ANY SIGNIFICANT FLOODING PROBLEMS. HOWEVER... THE TIDE MONDAY NIGHT REACHES 11.4 FEET WITH A STRONGER EASTERLY FLOW OVER THE GULF OF MAINE. ONSHORE FLOW AND BUILDING SEAS WILL INCREASE THE THREAT OF COASTAL FLOODING FOR THE HIGH TIDE MONDAY NIGHT AND A COASTAL FLOOD WATCH HAS BEEN ISSUED TO HIGHLIGHT THIS THREAT. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...FLOOD WATCH FROM MONDAY EVENING THROUGH WEDNESDAY MORNING FOR MEZ007>009-012>014-018>028. COASTAL FLOOD WATCH FROM MONDAY EVENING THROUGH LATE MONDAY NIGHT FOR MEZ023>028. NH...FLOOD WATCH FROM MONDAY EVENING THROUGH WEDNESDAY MORNING FOR NHZ002>015. COASTAL FLOOD WATCH FROM MONDAY EVENING THROUGH LATE MONDAY NIGHT FOR NHZ014. MARINE...GALE WATCH FROM MONDAY AFTERNOON THROUGH TUESDAY AFTERNOON FOR ANZ150>154. && $$ ES

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