Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 130432 AFDGYX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAY ME 1232 AM EDT SUN JUL 13 2014 .SYNOPSIS...
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A WARM FRONT PUSHES TO THE NORTHEAST OVERNIGHT BRINGING IN MORE HUMID AND UNSTABLE AIR ON SUNDAY WITH AN INCREASING RISK OF SHOWERS AND THUNDERSTORMS. THE WARM HUMID AIRMASS WILL LINGER FOR MONDAY AND TUESDAY IN ADVANCE OF A SLOW-MOVING COLD FRONT. THE COLD FRONT IS EXPECTED TO EXIT THE COAST BY LATE WEDNESDAY. HIGH PRESSURE WILL BUILD TO THE SOUTH OF THE AREA THURSDAY AND FRIDAY.
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&& .NEAR TERM /UNTIL 6 AM THIS MORNING/...
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WILL UPDATE TO INPUT THE LATEST OBSERVED DATA RESULTING IN JUST MINOR ADJUSTMENT TO THE CHC/SLGT CHC OF SHRA AND ISOLD TSTMS IN THE N/MT ZONES OVERNIGHT PER LATEST RADAR LOOP AND TO INCREASE SKY COVER ACROSS THE FCST AREA A BIT OVERNIGHT PER LATEST SATELLITE LOOP. STILL SOME VALLEY F POSSIBLE IN LOW LYING AREAS...MAINLY CT VALLEY AND MERRIMACK VALLEY...AND ALONG THE MID COAST DUE TO ONSHORE S SW FLOW OF MOIST ATLANTIC AIR. HIGH PRESSURE OFF THE COAST WITH A WARM FNT APPROACHING FROM THE SW IS RESPONSIBLE FOR INCREASING CLOUDS AND S SW FLOW OVERNIGHT. A WEAK UPPER LVL IMPULSE ALONG WITH THE ADVECTION OF WARM...HUMID AND UNSTABLE AIR IS PRODUCING THE ISOLD/SCT CONVECTION ACROSS OUR NRN TIER OF ZONES AT THIS TIME. THIS ACTIVITY WILL MOVE E AND DISSIPATE THRU THE NGT.
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&& .SHORT TERM /6 AM THIS MORNING THROUGH 6 AM MONDAY/... THE WAA ON SUNDAY WILL ADVECT HIGHER DEWPTS AND TEMPS ALONG WITH INCRG INSTBLTY. ENOUGH SHEAR SHOULD HELP ENHANCE INSTBLY AND CAUSE TSTM ACTIVITY IN THE AFTN AND INTO SUNDAY NIGHT. PW`S WILL BE HIGH SO HVY DOWNPOURS CAN BE EXPECTED. SOME TSTMS MAY BECOME STG LATER IN THE DAY BUT SHOULD REMAIN BLO SVR LIMITS. GOING WITH HIGH POPS FOR SUNDAY INTO SUNDAY NIGHT WHICH IS WHAT THE BLENDED MODEL SOLUTION SUGGESTS. USED A BLEND OF RFCQPF AND MODEL GUID FOR QPF FCST. AVERAGE BASIN AVG RAINFALL FOR THIS EVENT IS AROUND .50-.75 INCHES BUT LOCALLY HIGHER AMTS IN SOME OF THE STRONGER STORMS. && .LONG TERM /MONDAY THROUGH SATURDAY/... THE MAIN FOCUS OF THE FORECAST WILL BE ON THE STALLING COLD FRONT OVER THE REGION EARLY TO MID WEEK...AS IT LINES UP WITH DECENT S-SW FLOW ALOFT. THIS WILL KEEP A THREAT FOR SHRA/TSRA IN THE FORECAST MON-WED. THE DETAILS IN THIS PERIOD REMAIN UNCERTAIN...AS THE MODELS DIFFER ON THE WHERE THE FRONT STALLS...THE TIMING OF THE WAVES THAT MOVE ALONG THE FRONT /ALL AFFECTED BY DEEPER CONVECTION UPSTREAM/...AND ULTIMATELY...THE STRENGTH AND EQUATORWARD EXTENT OF THE 500MB TROUGH THAT WILL KICK THE FRONT EWD AROUND MID WEEK. HAVE GENERALLY OPTED FOR CHC POPS THROUGH THE PERIOD...SHADING THE HIGHER POPS TOWARD MON NIGHT THRU TUE NIGHT...AND CLOSER TO THE COAST...MAINLY BASED ON BLENDING THE MODEL POPS. VERY HUMID AIR LOOKS TO HOLD...ESPECIALLY S AND E OF THE MTNS MON THROUGH TUE...WITH SIGNS OF A LOW LEVEL JET DEVELOPING MON INTO MON NIGHT...WHICH WOULD INCREASE THE THREAT OF TORRENTIAL DOWNPOURS IN ANY STORMS THAT FROM...AND HAVE ADDED THE MENTION OF HVY RAIN TO THE FORECAST FOR MON-MON NIGHT. GIVEN A FAIR AMT OF CLOUDS AND THE RAIN...MAXES WILL GENERALLY BE IN THE MID 70S TO LOW 80S...BUT TDS WILL RUN IN THE 65-70 RANGE MON-TUE...WITH OVERNIGHT LOWS MATCHING THE TDS...AT LEAST MON NIGHT. THE EURO HAS BEEN CONSISTENT IN LINGERING THE FRONT OVER THE AREA INTO WED...BUT BOTH THE NAM12 AND THE GFS SUGGEST IT WILL BE MORE PROGRESSIVE AND COULD BE OUT OF HERE BY TUE NIGHT OR EARLY WED. COULD SEE SOMEWHAT COOLER AND DRIER AIR IN THE MTNS BY LATE TUE IN THE MORE PROGRESSIVE SOLNS ARE CORRECT. WED IS THE LOWEST CONFIDENCE DAY AT THIS POINT AS THE FRONT LOCATION VARIES WIDELY AMONG THE MODELS...BUT HAVE HIGHER CONFIDENCE FOR IMPROVEMENT BY THU/FRI AS THE FRONT MOVES OUT AND SOMEWHAT LESS HUMID AIR MOVES IN WITH PARTLY TO MOSTLY SUNNY SKIES. && .AVIATION /06Z SUNDAY THROUGH THURSDAY/...
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SHORT TERM /THROUGH SUNDAY NIGHT/...VFR TNGT. AREAS OF F POSSIBLE LATE TNGT WHICH MAY IMPACT TAF SITES LIKE KLEB...KHIE AND KCON. ON SUNDAY AFTN DEVELOPING SHWRS/TSTMS IN THE MTNS AND NH WILL SLOWLY SPREAD SEWD. MVFR CONDS WILL BE EXPECTED WITH THE DEVELOPING CONVECTION AS IT WILL CONTINUE AND BECOME MORE WIDESPREAD SUNDAY NIGHT. LONG TERM...VARIABLE CONDS EXPECTED MON IN SCT SHRA/TSRA...WITH COND DETERIORATING TO IFR OR LOWER IN FOG LOW CLOUDS AND CONTINUED SHRA MON NIGHT. THIS PATTERN LOOKS TO REPEAT ON TUE AND TUE NIGHT...ALTHOUGH THERE COULD BE SOME IMPROVEMENT AT INTERIOR NH TUE NIGHT. THE THREAT OF SHRA AND TSRA CONTINUES WED...WITH A HIGHER CONFIDENCE OF A RETURN TO VFR EXPECTED THU.
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&& .MARINE...
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SHORT TERM /OVERNIGHT THROUGH SUNDAY NIGHT/...WILL UPDATE TO INPUT LATEST OBSERVED DATA. THIS WILL RESULT IN MINOR CHANGES TO WINDS AND SEAS OVERNIGHT...BUT STILL KEEP CONDITIONS BELOW SCA LEVELS THRU THE NGT. WILL CONT THE SCA FOR SUNDAY AFTERNOON THRU MONDAY MORNING. DEVELOPING S FLOW IS EXPECTED TONIGHT AS THE CENTER OF SFC HIGH PRES MOVES OFF THE COAST. THE S SW FLOW INCREASES SUNDAY AS THE WARM FNT MOVES TO THE NE AND THE SFC PRESSURE GRADIENT INCREASES. WIND GUSTS AND SEAS ARE EXPECTED TO REACH SCA CONDS SUNDAY AFTERNOON AND THRU SUNDAY NIGHT FIRST OVER THE OPEN WATERS AND THEN THE BAYS AS WELL. LONG TERM...SW WINDS SUBSIDE A BIT ON MON...BUT S-SW FLOW REMAINS PERSISTENT RIGHT INTO TUE NIGHT AT LEAST...AND THIS WILL KEEP SEAS AROUND 5-6 FT IN THE OPEN WATERS. THE FLOW WILL EVENTUALLY SHIFT MORE W AND WEAKEN AROUND WED AND THU...WITH SEAS SUBSIDING.
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&& .TIDES/COASTAL FLOODING...
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AN ASTRONOMICAL HIGH TIDE OF 11.7 FT WHICH WILL BE ONE OF THE HIGHEST OF THE YEAR, WILL OCCUR AT 1236 AM SUNDAY NIGHT. AN INCREASING SOUTHERLY FLOW AND BUILDING SEAS MAY CAUSE SOME PROBLEMS ALONG THE COAST. SOME MINOR COASTAL FLOODING AND SPLASHOVER IS POSSIBLE. A COASTAL FLOOD WATCH MAY NEED TO BE ISSUED FOR MUCH OF THE COASTLINE AT A LATER TIME AS IT WILL NOT TAKE MUCH TO REACH MINIMAL FLOOD BENCHMARKS.
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&& .GYX WATCHES/WARNINGS/ADVISORIES...
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ME...NONE. NH...NONE. MARINE...SMALL CRAFT ADVISORY FROM 2 PM THIS AFTERNOON TO 8 AM EDT MONDAY FOR ANZ150>154.
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&& $$

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