Area Forecast Discussion
Issued by NWS Portland, ME

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895 FXUS61 KGYX 171624 AFDGYX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAY ME 1224 PM EDT SUN MAY 17 2015 .SYNOPSIS... WEAK LOW PRESSURE OVER THE REGION WILL SHIFT SOUTHEAST TODAY AND HIGH PRESSURE WILL BUILD IN FROM THE NORTHEAST TONIGHT THROUGH MONDAY. A COLD FRONT WILL APPROACH FROM THE WEST MONDAY NIGHT AND WILL CROSS THE REGION ON TUESDAY. SEVERAL TROUGHS OF LOW PRESSURE WILL DROP SOUTH THROUGH THE REGION WEDNESDAY THROUGH FRIDAY. HIGH PRESSURE WILL BUILD IN FROM THE WEST ON SATURDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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UPDATE...ANOTHER MINOR UPDATE TO INPUT CURRENT OBSERVATIONS. MINOR CHANGES TO TEMPS DEWPOINT AND CLOUDS. PREV DISC...SHOWERS AND A FEW THUNDERSTORMS WILL SHIFT EAST OF THE REGION THROUGH DAYBREAK AS A WEAK AREA OF LOW PRESSURE SLIDES OFF TO THE SOUTHEAST. OCEAN STRATUS AFFECTING MAINLY COASTAL MAINE WILL ALSO BE SHIFTING EAST BY DAYBREAK AS A WEAK NORTHWEST FLOW SETS UP BEHIND THE DEPARTING LOW. EXPECT DIMINISHING CLOUDS DURING THE MORNING HOURS TODAY WITH SKIES BECOMING MOSTLY SUNNY BY AFTERNOON. TEMPERATURES WILL REBOUND NICELY WITH HIGHS RANGING THROUGH THE 70S TO NEAR 80. INCREASING ONSHORE FLOW LATER THIS AFTERNOON WILL COOL DOWN COASTAL AREAS INTO THE UPPER 60S TO LOWER 70S.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/... HIGH PRESSURE BUILDS IN FROM THE NORTHEAST OVERNIGHT. CONTINUING ONSHORE FLOW WILL BRING OCEAN STRATUS INTO COASTAL AND SOUTHERN INTERIOR SECTIONS OF MAINE AND NEW HAMPSHIRE THIS EVENING. LOW TEMPERATURES WILL RANGE THROUGH THE 40S IN MOST AREAS WITH THE EXCEPTION OF SOUTHERN NEW HAMPSHIRE WHERE IT WILL BE SLIGHTLY WARMER WITH READINGS IN THE LOWER 50S. OCEAN STRATUS WILL GET SHUNTED OFF TO THE SOUTHWEST MONDAY MORNING AS HIGH PRESSURE CONTINUES TO BUILD IN FROM THE NORTHEAST SETTING UP A MOSTLY SUNNY AFTERNOON. MUCH OF THE FORECAST AREA WILL ONLY REACH THE LOWER TO MID 60S FOR HIGHS. THE CONNECTICUT VALLEY WILL BE SLIGHTLY WARMER WITH HIGHS IN THE UPPER 60S TO LOWER 70S. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... SURFACE HIGH PRESSURE SHIFTS EAST INTO THE ATLANTIC AND A RATHER BROAD AREA OF LOW PRESSURE BEGINS MOVING THROUGH QUEBEC MONDAY NIGHT. SHORTWAVE TROUGH CROSSING THE AREA WILL LIKELY BRING A ROUND OF SHOWERS DURING THE OVERNIGHT HOURS LASTING INTO TUESDAY MORNING. DEWPOINTS WILL BE ON THE INCREASE AS SOUTHWEST FLOW BRINGS IN THE LOW LEVEL MOISTURE. AFTER THE FIRST ROUND OF SHOWERS MOVES THROUGH MONDAY MORNING AND LOW LEVEL MOISTURE INCREASES... THERE WILL BE INCREASING INSTABILITY OVER VERMONT AND NEW HAMPSHIRE DURING THE AFTERNOON. ADD TO THIS A FRONTAL BOUNDARY MOVING WEST TO EAST ACROSS THE REGION AND THERE WILL BE A CHANCE OF THUNDERSTORMS FROM TUESDAY AFTERNOON THROUGH TUESDAY NIGHT AS THE FRONT MOVES THROUGH THE REGION. JUST HOW UNSTABLE WILL IT BE IS THE ULTIMATE QUESTION. BUT IF ENOUGH INSTABILITY CAN BE REALIZED FROM THE COMBINATION OF MOIST ADVECTION AHEAD OF THE FRONT AND SOLAR HEATING THROUGH THE BREAKS IN THE CLOUDS ON TUESDAY... THERE IS A CHANCE FOR MORE ROBUST THUNDERSTORM DEVELOPMENT. WIND SHEAR WILL BE ON THE INCREASE AS WELL DUE TO THE APPROACHING TROUGH ALOFT... WITH DIRECTIONAL SHEAR AVAILABLE AHEAD OF THE FRONT. STILL QUITE UNCERTAIN AS TO WHETHER ALL THE PARAMETERS WILL LINE UP PERFECTLY ENOUGH TO GET SEVERE THUNDERSTORMS... BUT THERE WILL AT LEAST BE A CHANCE OF THIS OCCURRING MAINLY OVER WESTERN AND NORTHERN NEW HAMPSHIRE. FRONT MOVES THROUGH THE AREA TUESDAY NIGHT BRINGING THE SHOWERS AND STORMS TO AN END AND HIGH PRESSURE BUILDS IN. SHOULD SEE COOLER WEATHER AT LEAST INITIALLY... BUT TEMPERATURES BEGIN WARMING AGAIN BY THE END OF THE WEEK. && .AVIATION /18Z SUNDAY THROUGH FRIDAY/... SHORT TERM...IFR/LIFR CEILINGS/VISIBILITIES IMPROVING TO VFR THIS MORNING. IFR/LIFR CEILINGS AND VISIBILITY REDEVELOP OVERNIGHT AND WILL ONCE AGAIN IMPROVE TO VFR ON MONDAY. LONG TERM...POSSIBILITY OF IFR CEILINGS TUESDAY MORNING IN AN ONSHORE FLOW OVER MUCH OF MAINE. SHOWERS WILL BRING OCCASIONALLY MVFR OR IFR CONDITIONS MONDAY NIGHT INTO TUESDAY MORNING ACROSS THE ENTIRE AREA. THERE WILL BE A CHANCE OF THUNDERSTORMS TUESDAY AFTERNOON AND EVENING MAINLY OVER NEW HAMPSHIRE. A COLD FRONT MOVES THROUGH TUESDAY NIGHT AND SHOULD BRING VFR CONDITIONS FOR THE REST OF THE WEEK. && .MARINE... SHORT TERM...WEAK LOW PRESSURE MOVES OFF TO THE SOUTHEAST TODAY WITH HIGH PRESSURE BUILDING DOWN OUT OF THE CANADIAN MARITIMES. THIS WILL SET UP A LIGHT EASTERLY FLOW OVER THE WATERS AND COULD LEAD TO THE DEVELOPMENT OF FOG. LONG TERM...FLOW BECOMES MORE SOUTHERLY MONDAY NIGHT INTO TUESDAY AHEAD OF AN APPROACHING FRONT. THIS FRONT CROSSES THE GULF OF MAINE TUESDAY NIGHT WITH HIGH PRESSURE BUILDING BEHIND IT. DO NOT EXPECT WINDS OR SEAS TO REACH ADVISORY LEVELS THIS WEEK. && .FIRE WEATHER... MODERATE RELATIVE HUMIDITY WILL PERSIST ACROSS THE REGION TODAY AND MONDAY AND DO NOT EXPECT ANY FIRE WEATHER ISSUES THROUGH THE PERIOD. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...NONE. NH...NONE. MARINE...NONE. && $$ UPDATE...TFH

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