Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 271354 AAA AFDGYX AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE GRAY ME 954 AM EDT SAT JUN 27 2015 .SYNOPSIS... HIGH PRESSURE GRADUALLY MOVE OFF TO THE EAST TODAY. LOW PRESSURE WILL APPROACH THE REGION TONIGHT AND MOVE THROUGH THE GULF OF MAINE ON SUNDAY BRINGING THE POTENTIAL FOR HEAVY RAIN TO THE REGION. THE SYSTEM WILL BE SLOW TO MOVE OUT SUNDAY NIGHT AND MONDAY BEFORE WEAK HIGH PRESSURE ONCE AGAIN RETURNS FOR TUESDAY. ANOTHER LOW PRESSURE SYSTEM WILL PASS NORTH OF THE AREA LATE TUESDAY AND WEDNESDAY BRINGING ANOTHER CHANCE OF SHOWERS TO THE NORTHEAST. HIGH PRESSURE THEN DOMINATES FOR THE REST OF THE WORK WEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... UPDATE...MINOR ADJUSTMENTS TO REFLECT CURRENT OBSERVATIONAL TRENDS. OTHERWISE NO MAJOR CHANGES TO THE FORECAST...WITH FOCUS ON APPROACHING HEAVY RNFL EVENT. PREVIOUSLY... HIGH PRESSURE OVERHEAD EARLY THIS MORNING WILL SHIFT OFF TO THE EAST AS THE DAY PROGRESSES. A LOW PRESSURE SYSTEM WILL APPROACH FROM THE SOUTHERN GREAT LAKES THIS AFTERNOON AND THIS WILL ALLOW FOR AN INCREASE IN CLOUDS. A WARM FRONT WILL SHARPEN UP TO OUR SOUTH THIS AFTERNOON...AND INCREASED FORCING FOR ASCENT MAY ALLOW FOR LIGHT RAIN TO ENTER SOUTHWESTERN NEW HAMPSHIRE LATE THIS AFTERNOON. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/... MID AND UPPER LEVEL LOW PRESSURE WILL CONTINUE TO MOVE EASTWARD TOWARD NEW ENGLAND TONIGHT AND THIS WILL AID IN CYCLOGENESIS OVER THE NORTHERN MID ATLANTIC STATES TONIGHT INTO EARLY SUNDAY MORNING. THIS SYSTEM WILL RESEMBLE MORE OF A WINTERTIME SYSTEM WITH THE DYNAMICS AND KINEMATICS AT WORK. DURING THE DAY ON SUNDAY A STRONG EASTERLY CONVEYOR BELT OF MOISTURE WILL DEVELOP OVERHEAD AND OVERRUN A STABLE BOUNDARY LAYER CHARACTERIZED BY WINTER-LIKE COLD AIR DAMMING. THE 925MB AND 850MB U-WIND ANOMALIES BASED ON THE SREF AND GEFS REACH +5 STANDARD DEVIATIONS SUNDAY MORNING WHICH IS EXTREME. THEREFORE...THE INFLOW WILL BE VERY STRONG AND CONDUCIVE FOR HEAVY RAINFALL WHEN COMBINED WITH PWAT ANOMALIES OF +1 TO +2 SD. WILL ALSO HAVE TO MONITOR FOR LOW-END ADVISORY-CRITERIA WINDS ON THE COAST SUNDAY DUE TO THIS EASTERLY JET. FOR NOW...HAVE GUSTS UP TO 40 MPH FOR THE COAST. HAVE HOISTED A FLOOD WATCH FOR THE WHITE MOUNTAINS /MAINLY FOR THE SOUTHEAST AND EAST FACING SLOPES/ WHERE UPSLOPE CONTRIBUTION TO HEAVY RAINFALL WILL BE EXCELLENT. THE WATCH AREA HAS ALSO HAD ANYWHERE BETWEEN 1 AND 3 INCHES OF RAINFALL OVER THE PAST WEEK FROM THUNDERSTORMS...SO RIVER MAY APPROACH OR EXCEED BANKFULL. MAY HAVE TO CONSIDER AND FLOOD WATCH ELSEWHERE...BUT SINCE RAINFALL AMOUNTS OVER THE LAST FEW WEEKS OUTSIDE OF THE WATCH AREA HAVE BEEN RELATIVELY LOW WITH RIVER LEVELS ALSO RUNNING LOW...HAVE DECIDED TO HOLD OFF. HOWEVER...WILL HAVE TO WATCH FOR PERSISTING AREAS OF HEAVY RAIN THAT COULD TRIGGER LOCALIZED FLOODING OR FLASH FLOODING. THE MAIN THRUST OF HEAVY RAINFALL WILL MOVE ON OUT AROUND MIDDAY SUNDAY. HOWEVER...CATEGORICAL LIGHTER RAINS OR SHOWERS ARE EXPECTED TO CONTINUE THROUGH THE AFTERNOON HOURS. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... CYCLONIC FLOW AT THE SURFACE COMBINED WITH THE UPPER LEVEL TROUGH WILL KEEP SKIES MOSTLY CLOUDY SUNDAY NIGHT INTO MONDAY WITH THE CHANCE SCATTERED SHOWERS OR SPRINKLES. A WEAK RIDGE OF HIGH PRESSURE WILL BUILD INTO THE REGION LATE MONDAY AND MUCH OF TUESDAY. ANOTHER LOW AND ASSOCIATED COLD FRONT WILL BRING THE THREAT OF SHOWERS TUESDAY NIGHT INTO WEDNESDAY. A SECOND FRONT WILL PUSH THROUGH THE AREA WEDNESDAY NIGHT AS A LARGE AREA OF HIGH PRESSURE DRIFTS SOUTHEAST FROM CENTRAL CANADA. THIS HIGH WILL PROVIDE VERY NICE WEATHER THURSDAY AND FRIDAY...AND POSSIBLY NICE SUMMER WEATHER THROUGH MUCH OF NEXT WEEKEND. MODELS DIVERGE A BIT ON THE FORECAST FOR NEXT WEEKEND THOUGH, WITH THE GFS DRY THROUGH THE DAY SUNDAY AND THE ECMWF BRINGING SHOWERS TO THE AREA BY SATURDAY. && .AVIATION /14Z SATURDAY THROUGH WEDNESDAY/... SHORT TERM /THROUGH SUNDAY/...VFR CONDITIONS TODAY WILL GIVE WAY TO IFR TONIGHT...ESPECIALLY AFTER MIDNIGHT AND WILL CONTINUE THROUGH SUNDAY. ON THE COAST...EASTERLY WINDS MAY GUST TO 30 KT SUNDAY MORNING. LONG TERM...IFR CONDITIONS SUNDAY NIGHT WILL GRADUALLY IMPROVE TO MVFR MONDAY AND VFR TUESDAY. && .MARINE... SHORT TERM...A GALE WARNING HAS BEEN ISSUED FOR THE OCEAN WATERS FOR SUNDAY WHERE STRONG EASTERLY WINDS AND SEAS IN EXCESS OF 10 FT ARE EXPECTED. LONG TERM...WINDS AND SEAS WILL GRADUALLY DECREASE SUNDAY NIGHT...HOWEVER AN SCA WILL LIKELY BE NEEDED THROUGH MONDAY NIGHT AS SEAS REMAIN HIGH. ANOTHER SCA MAY BE NEEDED WEDNESDAY WITH THE NEXT STORM SYSTEM. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...NONE. NH...FLOOD WATCH FROM LATE TONIGHT THROUGH SUNDAY EVENING FOR NHZ001>005. MARINE...GALE WATCH FROM SUNDAY MORNING THROUGH SUNDAY EVENING FOR ANZ151-153. GALE WARNING FROM 5 AM TO 7 PM EDT SUNDAY FOR ANZ150-152-154. && $$ NEAR TERM...LEGRO

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