Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 031520 AFDGYX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAY ME 1120 AM EDT SUN MAY 3 2015 .SYNOPSIS... HIGH PRESSURE OFFSHORE WILL BRING A SOUTHERLY FLOW OVER THE NORTHEAST AND TRANSPORT WARMER AIR INTO THE AREA. SOME AFTERNOON SHOWERS OR A THUNDERSTORM ARE POSSIBLE TODAY. A WEAK COLD FRONT WILL CROSS THE AREA MONDAY NIGHT AND EARLY TUESDAY WITH SCATTERED SHOWERS AND THUNDERSTORMS. ANOTHER MOISTURE STARVED COLD FRONT WILL CROSS THE AREA WEDNESDAY. A RIDGE OF HIGH PRESSURE FOLLOWS FOR LATE WEDNESDAY INTO FRIDAY. A DEVELOPING ONSHORE FLOW AND AN APPROACHING WARM FRONT WILL MAKE THE WEATHER INCREASINGLY UNSETTLED FOR THE UPCOMING WEEKEND. && .NEAR TERM /TODAY/...
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1130 AM UPDATE... TEMPERATURES ARE WARMING UP A BIT MORE QUICKLY THAN FORECAST SO THIS IS NOW REFLECTED IN THE LATEST UPDATE. HAVE INCREASED AFTERNOON HIGH TEMPERATURES IN THE NORTH AND WEST... BASICALLY MOST INLAND AREAS. ALONG THE COAST FROM PORTLAND EASTWARD TEMPERATURES ARE SLOWER TO REACT AFTER MORNING CLOUDS FINALLY DISAPPEARED. TEMPERATURES HAVE BEEN LOWERED ALONG THE IMMEDIATE COAST AS IT WILL BE TOUGH TO GET MUCH WARMING TODAY WITH AN ONSHORE FLOW AS NOTED BY YESTERDAY`S COLDER THAN FORECAST HIGHS. MID LEVEL SHORTWAVE TROUGH NOW MOVING INTO THE AREA AS NOTED BY A COUPLE BANDS OF CLOUDS AND LIGHT SHOWERS. ADDITIONAL CUMULUS IS FORMING BENEATH THIS AREA ALONG THE HIGHER TERRAIN AND WILL LIKELY RESULT IN SHOWERS WITHIN THE NEXT FEW HOURS. 830 AM UPDATE... HAVE UPDATED THE FORECAST PRIMARILY TO ADJUST PRECIPITATION CHANCES THIS AFTERNOON. FIRST LOOK AT THE MORNING SOUNDING SUGGESTS THAT ONCE TEMPERATURES REACH THE UPPER 60S THERE WILL BE ENOUGH INSTABILITY FOR SOME SHOWERS. THESE WILL BE TIED TO THE TERRAIN INITIALLY BEFORE DRIFTING OFF THE TERRAIN AND DISSIPATING. THEREFORE HIGHEST CHANCES FOR RAIN WILL BE OVER THE TERRAIN AREAS AND THE GRIDDED FORECAST NOW REFLECTS THIS. CANNOT RULE OUT SOME GRAUPEL WITH SHOWERS THIS AFTERNOON BUT BASED ON THE LOCATION OF INSTABILITY WITH REGARDS TO ATMOSPHERIC TEMPERATURE PROFILE IT SEEMS LESS LIKELY. MORNING CLOUDS AND FOG OVER THE MAINE COAST SHOULD DISSIPATE OVER THE NEXT HOUR OR TWO AT MOST. 620 AM... APPARENTLY...THE COASTAL FOG AND STRATUS HAD A SECOND WIND AND HAVE MOVED BACK TO THE N AND W...AT LEAST AS FAR AS KWVL-KIZG- KPSM. HARD TO FIND OBSERVATIONS THAT WOULD SUGGEST MUCH TOO FAR N AND W OF THERE. HAVE ADJUSTED GRIDS ACCORDINGLY...AND STILL EXPECT IT DISSIPATE BETWEEN 12 AND 14Z. ORIGINAL DISCUSSION... COASTAL STRATUS AND FOG HAVING A TOUGHER TIME HOLDING TOGETHER THIS MORNING THAN YESTERDAY...GIVEN INCREASING FLOW AND STEEPER LAPSE RATES ABOVE THE BOUNDARY LAYER...AND IT SHOULD DISSIPATE FAIRLY QUICKLY AFTER SUNRISE. FOR TODAY...WILL SEE WEAK 500 MB WAVE MOVING THRU THE 500MB RIDGING ALOFT...WHICH WILL ALLOW FOR SOME HEIGHT FALLS THIS MORNING AND PRODUCE SOME DECENT LOW LEVEL LAPSE RATES AWAY FROM THE COAST THIS AFTERNOON. DYNAMIC FORCING NOT IMPRESSIVE...BUT THERE WILL BE SOME CONVERGENCE GENERATED BY WEAK LEE TROUGH...AND ENOUGH INSTABILITY TO PROBABLY GET A BOOST FROM LOW LEVEL LIFT...EITHER DUE TO TERRAIN...OR ALONG INLAND SIDE OF SEA BREEZE BOUNDARY. DEPENDING ON WHICH WHICH MESOSCALE MODEL YOU LOOK AT...INCLUDING RAP/WRF/NAMDNG/CMC 2.5KM...SCATTERED CONVECTION POPS UP IN EITHER OF THESE SPOTS AROUND 18-21Z...WITH A SLIGHT SKEW TOWARD THE MOUNTAINS AND FOOTHILLS OF WESTERN MAINE. WOULD EXPECT SOME SCATTERED SHOWERS...ISOLATED THUNDERSTORMS THIS AFTERNOON AWAY FROM THE COAST...AS THE STABLE MARINE LAYER IS LIKELY TO QUICKLY DESTROY ANY CONVECTION THAT MOVES INTO IT. WOULD NOT BE SURPRISED TO SEE A REPORT OR TWO OF GRAUPEL/SMALL HAIL GIVEN COLDER AIR ALOFT. AGAIN THE SEA BREEZE KEEPS THE IMMEDIATE COAST ABOUT 10 F COOLER FOR HIGHS TODAY...UPPER 50S TO LOW 60S...WHERE INLAND SPOTS WILL REACH TO 70-75.
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&& .SHORT TERM /TONIGHT AND MONDAY/... ANY SHOWERS WILL DIMINISH QUICKLY WITH THE SETTING SUN AND SKIES SHOULD BECOME MAINLY CLEAR. COULD SEE ANOTHER ROUND OF COASTAL STRATUS AND FOG AGAIN...ALTHOUGH PROBABLY LESS LIKELY GIVEN INCREASING SW FLOW...BUT IF THE STRATUS SITS JUST OFFSHORE THRU THE DAY...IT IS LIKELY TO CREEP IN AFTER SUNSET. MINS WILL GENERALLY BE FROM AROUND 40 INTO THE MID 40S. MONDAY LOOKS TO BE WARM AND GENERALLY SUNNY AS GRADIENT SW FLOW DEVELOPS. HIGHS IN THE MID 70S TO LOW 80S AT ALL BUT THE IMMEDIATE SHORELINE....WHERE IT WILL STAY IN THE 60S. ANY PRECIPITATION FROM APPROACHING COLD FRONT WILL HOLD OFF UNTIL AFTER SUNSET. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... A COLD FRONT MOVES ACROSS THE REGION MONDAY NIGHT AND EARLY TUESDAY...SCATTERED SHOWERS AND THUNDERSTORMS WILL BE ASSOCIATED WITH THE FRONT. BY MID MORNING TUESDAY THE FRONT MOVES WELL SOUTHEAST OF THE AREA WITH HIGH PRESSURE TO BUILD IN FROM THE GREAT LAKES. CLEARING WILL BE EXPECTED FROM NORTH TO SOUTH TUESDAY WITH CONTINUED MILD TEMPERATURES AS VERY LITTLE IN THE WAY OF COOL AIR MAKES ITS WAY SOUTH BEHIND THE FRONT. HIGH PRESSURE WILL BRING SUNNY SKIES WEDNESDAY AND AGAIN THURSDAY WITH TEMPERATURES NEAR 70 EXCEPT 60S IN THE MOUNTAINS. BY FRIDAY CLOUDS SPILL ACROSS THE UPPER RIDGE AXIS OVER THE NORTHEAST...THIS WILL BE DUE TO AN APPROACHING WARM FRONT FROM THE WEST. MODELS SHOW UNSETTLED WEATHER TO DEVELOP OVER THE WEEKEND WITH A WARMER AND MOIST UNSTABLE SOUTHWEST FLOW. IT LOOKS LIKE SPRING HAS FINALLY SPRUNG! && .AVIATION /13Z SUNDAY THROUGH THURSDAY/... SHORT TERM...THE COASTAL STRATUS DISSIPATES QUICKLY AFTER SUNRISE TODAY WITH VFR INTO THE EVENING. AN ISOLATED SHOWER OR EVEN A THUNDERSTORM IS POSSIBLE AWAY FROM THE COAST...BUT BEST CHANCE WILL BE AT KHIE...AND MAYBE KLEB. LONG TERM...MONDAY NIGHT INTO TUESDAY MORNING SCATTERED MVFR CONDITIONS POSSIBLE IN SHOWERS AND ANY THUNDERSTORMS...OTHERWISE VFR CONDITIONS THE REST OF THE OUTLOOK PERIOD. && .MARINE... SHORT TERM...SW WINDS PICK UP DURING THE DAY AND COULD APPROACH SCA IN THE AFTERNOON. LONG TERM...MONDAY NIGHT...SMALL CRAFT WINDS AND SEAS ARE POSSIBLE OVER THE OUTER WATERS. OTHERWISE WINDS AND SEAS WILL REMAIN BELOW SCA CONDITIONS THROUGH THE OUTLOOK PERIOD. && .FIRE WEATHER... AFTERNOON HUMIDITY LEVELS DROP TO 35-45 PERCENT TODAY BUT WINDS WILL REMAIN LIGHT...WITH GOOD RH RECOVERY TONIGHT. MONDAY WILL SEE 30-40 PERCENT MIN RH VALUES WITH SLIGHTLY STRONGER WINDS...10-15 MPH...BUT ARE EXPECTED TO REMAIN BELOW RED FLAG CRITERIA. GOOD RECOVERY IS EXPECTED MONDAY NIGHT...WITH SCATTERED SHOWERS. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...NONE. NH...NONE. MARINE...NONE. && $$ NEAR TERM UPDATE... KIMBLE

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