Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 192157 AAA AFDGYX AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE GRAY ME 557 PM EDT SUN APR 19 2015 .SYNOPSIS... HIGH PRESSURE WILL MOVE 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 AM MONDAY MORNING/... UPDATE...JUST SOME MINOR TWEAKS TO TEMPS AS THE SEA BREEZE PUSHES INLAND AND DROPS READINGS NEAR THE COAST. OTHERWISE FORECAST REMAINS ON TRACK. PREVIOUS DISCUSSION...IT HAS BEEN A BEAUTIFUL DAY ACROSS THE REGION AS HIGH PRESSURE MOVED OVER HEAD. A FEW HIGH CIRRUS CLOUDS ARE BEGINNING TO MOVE INTO SOUTHWEST NEW HAMPSHIRE... HERALDING THE APPROACH OF A STORM SYSTEM FOR MONDAY INTO TUESDAY. OVERNIGHT LOOK FOR HIGH CLOUDS TO BEGIN MOVING IN. TEMPERATURES WILL FALL TO JUST BELOW FREEZING IN THE NORTH AS THE CIRRUS WONT` LIMIT RADIATIONAL COOLING VERY MUCH. && .SHORT TERM /6 AM MONDAY MORNING THROUGH TUESDAY/... LOW PRESSURE CURRENTLY IN SOUTHERN ILLINOIS WILL TRACK NORTH NORTHEAST INTO THE GREAT LAKES SENDING A LARGE SLUG OF MOISTURE AHEAD OF IN AND INTO NORTHERN NEW ENGLAND. PRECIPITATION WILL MOVE INTO OUR WESTERN REGIONS BY NOON AND COVER THE ENTIRE AREA BY AROUND 5PM. MOST MODELS ARE IN GOOD AGREEMENT ON THE TIMING OF THIS SYSTEM THIS CLOSE TO ONSET AND HAVE GONE WITH A BLEND. WHILE RAIN WILL CONTINUE FROM MONDAY AFTERNOON THROUGH TUESDAY AFTERNOON, THE HEAVIEST RAIN WILL BE IN THE OVERNIGHT PERIOD WHEN A LOW LEVEL JET OF AROUND 50KTS HELPS TO TRANSPORT THE MOISTURE INTO THE REGION. EXPECT TWO PRECIPITATION MAXIMA. ONE DUE TO OROGRAPHY IN THE MAINE AND NEW HAMPSHIRE FOOTHILLS WHERE UPSLOPE FLOW WILL RESULT IN AS MUCH AS 2.5" OF TOTAL WATER. A SECONDARY MAXIMA WILL BE ALONG THE COAST. AS THE HIGH RECEDES TOWARDS NEW BRUNSWICK TONIGHT A COASTAL FRONT MAY SET UP. THIS WOULD CREATE A SECONDARY PRECIPITATION MAXIMA ALONG THE COAST FROM ABOUT YORK COUNTY THROUGH TO PENOBSCOT BAY. HAVE TRIED TO REFLECT BOTH OF THESE MAXIMA IN THE PRECIPITATION FORECASTS. IN ADDITION TO THE HEAVY RAIN... ELEVATIONS ABOVE 1500 TO 2000 FT WILL SEE A PERIOD OF WET SNOW OVERNIGHT MONDAY INTO TUESDAY. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... PERSISTENT UPPER LEVEL LOW PRESSURE SPINS OVER SOUTHERN CANADA AND EVENTUALLY DRIFTS CLOSER TO BE CENTERED NEAR THE SAINT LAWRENCE RIVER VALLEY TOWARDS THE END OF THE WEEK. THIS KEEPS REGULAR WAVES OF SHORT WAVE ENERGY MOVING OUR WAY OUT OF CENTRAL CANADA AND THE GREAT LAKES REGION. WE WILL HAVE ONLY A SHORT BREAK AFTER THE HEAVY RAIN EVENT MONDAY/ TUESDAY BEFORE THE NEXT PRECIPITATION EVENT BARRELS OUR WAY. TUESDAY LATE EVENING INTO WEDNESDAY MORNING THERE WILL ONLY BE ISOLATED SHOWERS. WEDNESDAY WILL BE RELATIVELY WARM WITH SUBSTANTIAL CLOUD COVER AS SOUTHERLY WINDS RETURN AGAIN AND PRECIPITABLE WATER INCREASES TO NEAR AN 1" FOR THE SECOND TIME THIS WEEK. THIS WILL NOT BE A HUGE ACHIEVEMENT AS WE WILL NOT HAVE HAD NW WINDS TO SCOUR ANY REMAINING MOISTURE OUT FROM THE EARLY WEEK SYSTEM. STEADIER RAIN SPREADS FROM WEST TO EAST WEDNESDAY AFTERNOON AND ENDS THURSDAY MORNING. RAIN MOVES OUT QUICKLY THURSDAY MORNING AFTER A MESOLOW FORMS AND SWEEPS NE. SOME INSTABILITY IS NOTED WEDNESDAY SO HAVE INCLUDED ISOLATED THUNDERSTORMS IN THE AFTERNOON. QPF WILL BE LIGHTER WITH THIS EVENT... ON THE ORDER OF A THIRD TO A HALF INCH... BUT IT MAY EXACERBATE ANY ONGOING FLOODING ISSUES. AS COLDER AIR ARRIVES... SNOW SHOWERS WILL BE POSSIBLE EARLY THURSDAY MORNING IN THE HIGHER PEAKS. DAILY SHOWER ACTIVITY IS LIKELY THROUGH THE WEEKEND AS AMPLE LOW LEVEL MOISTURE AND INSTABILITY PROVIDED BY THE UPPER LEVEL LOW WORK TOGETHER. && .AVIATION /22Z SUNDAY THROUGH FRIDAY/... SHORT TERM...VFR CONDITIONS WILL PREVAIL UNTIL THE EARLY MORNING HOURS. WILL SEE A MVFR CEILING MOVE IN FROM WEST TO EAST AFTER 10Z WITH PRECIPITATION FOLLOWING SOON AFTERWARDS. EXPECT IFR IN RAIN FOR ALL SITES EXCEPT HIE THROUGH TUESDAY. HIE WILL SEE A RAIN SHADOW AND STAY MVFR. ALONG THE COAST WIND GUSTS TO 30KTS ARE POSSIBLE THROUGH MONDAY AFTERNOON. LONG TERM...IFR TO MVFR CONDITIONS MAY CONTINUE FOR KHIE AND KLEB INTO WEDNESDAY MORNING IN LIGHT -SHSN. MVFR CONDITIONS RETURN AREAWIDE FOR WEDNESDAY AFTERNOON THROUGH THURSDAY MORNING IN -RA. ADDITIONAL LIGHTER SHOWERS ARE LIKELY IN THE HIGHER TERRAIN THROUGH THURSDAY AND INTO FRIDAY. && .MARINE... SHORT TERM...EASTERLY WINDS AND SEAS WILL BUILD MONDAY AHEAD OF THE APPROACHING SYSTEM. A GALE WARNING HAS BEEN ISSUED FOR THE OUTER WATERS WHERE WIND GUSTS WILL EXCEED 35KTS AND SEAS AS HIGH AS 15FT. THE WINDS AND WAVES WILL DIMINISH ON TUESDAY. LONG TERM...WIND GUSTS WILL DROP TO SCA OR LOWER TUESDAY NIGHT BUT SEAS WILL TAKE LONGER TO SUBSIDE...POSSIBLY UNTIL THURSDAY NIGHT. && .FIRE WEATHER... 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 REMAINS IN EFFECT. && .TIDES/COASTAL FLOODING... TONIGHT`S 12:32AM HIGH TIDE OF 11.6FT MLLW IN PORTLAND SHOULD PASS WITHOUT INCIDENT AS ALMOST NO WIND AND WAVES WILL KEEP WATER LEVELS SLIGHTLY BELOW FLOOD. AS EASTERLY WINDS PICK UP DURING THE DAY ON MONDAY SEAS WILL BUILD TO 10 TO 15 FT. HIGH TIDE ON APRIL 21 IS AT 1:21AM WITH A PREDICTED HEIGHT OF 11.4FT MLLW. ONSHORE WINDS ARE EXPECTED TO RESULT IN A 1-2FT STORM SURGE. THE COMBINATION OF WIND, WAVES AND HIGH TIDE WILL RESULT IN OVERWASH AND POSSIBLE INUNDATION FOR THE BEACHES OF THE SOUTH COAST OF MAINE AND NEW HAMPSHIRE. FURTHER NORTH THE EASTERLY WIND DIRECTION IS LESS FAVORABLE TO ONSHORE INUNDATION. EVEN SO THE SIGNIFICANT WAVES MAY RESULT IN SOME COASTAL FLOODING. DUE TO THE UNCERTAINTY THE FLOOD WATCH REMAINS IN EFFECT FOR THE MIDCOAST. && .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 MEZ025>028. COASTAL FLOOD WARNING FROM 11 PM MONDAY TO 3 AM EDT TUESDAY FOR MEZ023-024. NH...FLOOD WATCH FROM MONDAY EVENING THROUGH WEDNESDAY MORNING FOR NHZ002>015. COASTAL FLOOD WARNING FROM 11 PM MONDAY TO 3 AM EDT TUESDAY FOR NHZ014. MARINE...SMALL CRAFT ADVISORY FROM 5 PM MONDAY TO 2 PM EDT TUESDAY FOR ANZ151-153. GALE WARNING FROM 5 PM MONDAY TO 2 PM EDT TUESDAY FOR ANZ150- 152-154. && $$ NEAR TERM...LEGRO

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