Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 311904 AFDGYX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAY ME 304 PM EDT THU JUL 31 2014 .SYNOPSIS... HIGH PRESSURE WILL BUILD IN FROM THE EAST TODAY THROUGH FRIDAY. AFTERNOON SHOWERS AND THUNDERSTORMS ARE POSSIBLE PRIMARILY IN THE MOUNTAINS EACH DAY THROUGH THE MIDDLE OF NEXT WEEK. && .NEAR TERM /TONIGHT/... MAIN FOCUS IS ON THE THUNDERSTORMS IN THE IMMEDIATE NEAR TERM. SLOW HEATING HAS OCCURRED TODAY BENEATH A MOSTLY CLOUDY SKY ACROSS NH. THIS HAS PREVENTED MUCH OF THE STATE FROM REACHING CONVECTIVE TEMPERATURES. HOWEVER...FARTHER E READINGS CLIMBING INTO THE MID 70S HAVE TRIGGERED SCATTERED THUNDERSTORMS ACROSS MAINE. FOR NOW THE STORMS ARE STRUGGLING TO MAINTAIN MUCH HEIGHT...BUT WITH TIME COOLING ALOFT SHOULD SUPPORT CONTINUED UPDRAFT GROWTH. EXPECT THAT CAPE WILL REMAIN LESS THAN 1000 J/KG FOR MUCH OF THE AREA...BUT ADEQUATE SHEAR WILL HELP TO KEEP SOME ORGANIZATION TO THE CONVECTION. A FEW LARGE HAIL OR DAMAGING WIND REPORTS WILL STILL BE POSSIBLE. SO FAR THE MAIN FORCING WITH SHORTWAVE TROUGH HAS PRODUCED A BROKEN LINE OF THUNDERSTORMS...WITH GUSTS AROUND 30 KT AND SMALL HAIL. THOUGH ONE CELL BRIEFLY ATTAINED SUPERCELL CHARACTERISTICS ON THE SOUTHERN END OF THE LINE AND MANAGED TO PRODUCE 1 INCH HAIL. FEEL THAT THIS IS A FAIRLY GOOD REPRESENTATION OF WHAT WE CAN EXPECT ACROSS NH AND THEN MAINE THIS EVENING. WILL MAINTAIN GUSTY WINDS AND SMALL HAIL IN THE GRIDS UNTIL 01 OR 02Z. VARIOUS CONVECTIVE TOOLS...INCLUDING SPC SSEO AND HI-RES MODELS...RAPIDLY WEAKEN STORMS AFTER SUNSET. POP FORECAST DROPS OFF QUICKLY ACCORDINGLY. EXPECTING THAT FAIRLY WIDESPREAD VALLEY FOG OCCURS INLAND...WITH COASTAL FOG/STRATUS RELOADING FROM THE MIDCOAST DOWN TO KPWM. && .SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/... OVERALL COLD POOL REMAINS ALOFT AT H5 ON FRIDAY...WHICH WILL ALLOW FOR ANOTHER ROUND OF AFTERNOON CONVECTION. HOWEVER...MID LEVEL WARM ADVECTION WILL RESULT IN A LARGER CAP THAN TODAY. THIS WILL KEEP A LID ON ANY STORMS THAT DO FORM...PRECLUDING ANY SEVERE THREAT. ALSO LIGHTNING PROBABLY WILL NOT BE AS WIDESPREAD AS TODAY EITHER...SO HAVE ADJUSTED CHANCE OF TSTMS DOWN. LATE FRIDAY NIGHT APPROACHING DISTURBANCE RIDING UP THE EAST COAST WILL BEGIN TO SPREAD CLOUDS INTO THE AREA FROM THE S. SHOULD REMAIN MOSTLY DRY THRU SUNRISE...BUT HAVE SOME LOW CHANCE POP SNEAKING INTO SOUTHERN NH BY 12Z. && .LONG TERM /SATURDAY THROUGH THURSDAY/... STORY OF THE LONG TERM WILL BE A PERSISTENT TROUGH OVER THE GREAT LAKES REGION... WITH THE NORTHEAST BEING ON THE EAST SIDE OF THE TROUGH AXIS. SEVERAL MINOR WAVES WILL PASS THROUGH THE FLOW ON THE EAST SIDE OF THE TROUGH AND AID IN THE DEVELOPMENT OF SHOWERS AND STORMS MOSTLY DURING PEAK HEATING. COOL AIR ALOFT ALSO KEEPS THE ATMOSPHERE WEAKLY TO MODERATELY UNSTABLE AS THE SUN WARMS THE LOW LEVELS. THE RESULT IS THAT THE FORECAST FOR THIS WEEKEND AND NEXT WEEK GETS PRETTY REDUNDANT. SHOWERS AND STORMS ARE POSSIBLE JUST ABOUT EVERY AFTERNOON... MAINLY IN THE MOUNTAINS... WITH TEMPERATURES BELOW NORMAL. SATURDAY... SHOWER ACTIVITY SHOULD BE PRIMARILY CONFINED TO THE MOUNTAINS. OVERALL INSTABILITY IS WEAK SO THUNDERSTORMS WILL BE ISOLATED. A SHARPER SHORTWAVE TROUGH TRACKS ACROSS THE AREA SUNDAY... WITH A POSSIBLE SURFACE WARM FRONT MOVING NORTH AS WELL. THIS WILL BRING A BETTER CHANCE OF SHOWERS AND ISOLATED THUNDERSTORMS TO THE ENTIRE AREA. THE NAM IS THE MOST AGGRESSIVE WITH THE WARM FRONTAL FEATURE... AND AS SUCH... THE NAM WIND FIELDS WOULD INDICATE SOME PRETTY GOOD LOW LEVEL DIRECTIONAL WIND SHEAR ALONG AND NORTH OF THE WARM FRONT. SO ANY SHOWERS OR STORMS WHICH DEVELOP ALONG THE WARM FRONT COULD SEE A WEAK SPIN UP... BUT THE OVERALL THREAT WILL REMAIN LOW ESPECIALLY SINCE THE OTHER MODELS DO NOT SHOW AS DRAMATIC OF A WARM FRONT. GREAT LAKES TROUGH BECOMES BROADER AND LESS AMPLIFIED MONDAY... BUT WILL STILL SEE THE DIURNAL CHANCE FOR SHOWERS IN THE MOUNTAINS. THIS TREND CONTINUES RIGHT THROUGH THE MIDDLE OF THE WEEK AND THE END OF THIS FORECAST PERIOD. && .AVIATION /18Z THURSDAY THROUGH TUESDAY/... SHORT TERM...ANY SHOWERS/THUNDERSTORMS WILL QUICKLY END AFTER SUNSET...WITH SKIES CLEARING. ANY VFR WILL BE SHORT LIVED THOUGH...AS VALLEY FOG WILL BE QUICK TO SET IN WITH NOCTURNAL COOLING OF THE BOUNDARY LAYER. IN ADDITION...GUIDANCE SUGGESTS COASTAL FOG/STRATUS WILL REDEVELOP...ESPECIALLY INTO THE MIDCOAST BY 03Z. IFR OR LOWER CONDITIONS WILL BE POSSIBLE AGAIN...LINGERING INTO MID MORNING FRIDAY. MAINLY VFR IS EXPECTED FRIDAY AFTERNOON...WITH SHOWERS OR AN ISOLATED THUNDERSTORM POSSIBLE ACROSS NH. LATE FRIDAY NIGHT MVFR OR LOWER CEILINGS MAY BEGIN TO WORK NORTHWARD INTO THE AREA AS A DISTURBANCE MOVES UP THE EAST COAST. LONG TERM...GENERALLY VFR BUT THERE WILL BE A CHANCE FOR AFTERNOON SHOWERS AND STORMS MAINLY IN THE MOUNTAINS. NOCTURNAL FOG IS ALSO POSSIBLE AT LEBANON AND WHITEFIELD. && .MARINE... SHORT TERM...ANY THUNDERSTORMS THAT GRAZE THE WATERS WILL WEAKEN QUICKLY AFTER SUNSET. SUB- SCA CONDITIONS ARE EXPECTED THRU FRIDAY...HOWEVER AREAS OF DENSE FOG WILL BE PRESENT TONIGHT ESPECIALLY OFF THE MID COAST OF MAINE. LONG TERM...GENERALLY LIGHT WINDS AND LOW SEAS EXPECTED THROUGH MIDWEEK. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...NONE. NH...NONE. MARINE...NONE. && $$ NEAR TERM...LEGRO SHORT TERM...LEGRO LONG TERM...KIMBLE AVIATION...KIMBLE/LEGRO MARINE...KIMBLE/LEGRO

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