Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 210158 AFDGYX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAY ME 958 PM EDT SUN JUL 20 2014 .SYNOPSIS... HIGH PRESSURE BECOMES ENTRENCHED OFFSHORE MONDAY THROUGH WEDNESDAY...ALLOWING WARMER AND MORE HUMID AIR TO MOVE IN FROM THE SOUTHWEST. A COLD FRONT APPROACHES LATE WEDNESDAY AND MOVES THROUGH THE REGION THURSDAY...BRINGING A THREAT OF SHOWERS AND THUNDERSTORMS. HIGH PRESSURE BUILDS IN FROM THE WEST FRIDAY AND SATURDAY. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... 10 PM UPDATE: SKIES ARE MOCLR OVER NH AND SWRN ME. INPUT LATEST OBS DATA WITH NO CHANGES ATTM. PREV FCST: CLEARING WILL CONTINUE THIS EVENING...SETTING THE STAGE FOR A COOL AND CHILLY NIGHT WITH LIGHT WINDS AND RADIATIONAL COOLING. TEMPERATURES WILL DROP INTO THE 40S OVER THE MOUNTAINS WITH 50S ELSEWHERE. THIS WILL ALLOW FOR DENSE FOG TO DEVELOP IN MANY AREAS BY AROUND MIDNIGHT. LOOK FOR SOME AREAS TO DROP TO A QUARTER MILE OR LESS...ESPECIALLY ACROSS THE INLAND HOLLOWS. && .SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/... SEASONABLE TEMPERATURES ARE EXPECTED ON MONDAY AS HIGH PRESSURE BEGINS TO SHIFT OFF THE COAST AND A SOUTHWESTERLY FLOW DEVELOPS WITH TIME. READINGS WILL BE IN THE LOWER 80S INLAND...WITH MID TO UPPER 70S ALONG THE COAST DUE TO A DEVELOPING SEA BREEZE. A WEAK WEATHER DISTURBANCE WILL ENTER NORTHERN PORTIONS OF THE FORECAST AREA...TRIGGERING A COUPLE SCATTERED SHOWERS IN THE MOUNTAINS DURING THE MIDDAY AND AFTERNOON HOURS. ANY PRECIP HOWEVER WILL BE LIGHT. THE FOG TAKES HOLD ONCE AGAIN ON OUR REGION MONDAY NIGHT. EXPECT PATCHY DENSE FOG BY MIDNIGHT IN SOME AREAS. LOWS WILL MAINLY BE IN THE 50S. && .LONG TERM /MONDAY NIGHT THROUGH SUNDAY/... AN UPPER LVL RIDGE SLIDES ACROSS THE NE ON TUESDAY AS HIGH PRES AT THE SFC SLIDES OFF SHORE. THIS SETS UP A SW FLOW AT THE SFC AND A MORE WESTERLY FLOW ALOFT THAT BRINGS IN WARMER AND MORE HUMID AND UNSTABLE AIR. 850 MB TEMPS CLIMB ABOVE PLUS 15 C BY 00Z WED SUPPORTING VERY WARM HIGH TEMPS. THE VERY WARM...MOIST AND INCREASINGLY UNSTABLE ATMOSPHERE MAY ALLOW ISOLD CONVECTION TO DEVELOP IN THE LATE AFTERNOON/EARLY EVE HOURS...BUT NOT MUCH ELSE FOR SUPPORT...SO WILL LEAVE OUT OF THE FCST FOR THE TIME BEING. AN UPPER LVL TROF DIGS SE FROM CENTRAL CANADA INTO THE GREAT LAKES REGION TUESDAY NGT THEN TURNS TO THE E. THIS FORCES A SFC COLD FNT TO PUSH SE TOWARD THE FCST AREA ON WEDNESDAY. AS THE FNT AND UPPER LVL SYSTEM INTERACT WITH THE VERY WARM...MOIST AND UNSTABLE AIR EXPECT A BETTER CHC OF SHRA/TSTMS WITH POTENTIAL FOR STRONG TO SVR TSTMS WEDNESDAY AFTERNOON AND EVENING AS AN INCREASINGLY SHEARED ENVIRONMENT DEVELOPS ALONG WITH INCREASING CAPE, DECREASING LI`S AND INCREASING AXIS OF HIGHER 850 MB THETA E VALUES TO SUPPORT VERY STRONG CONVECTION. THE COLD FNT MOVES THRU WEDNESDAY NGT...OR PERHAPS THURSDAY AS SOME MODELS SHOW IT SLOWING DOWN AS IT WAITS FOR THE UPPER LVL TROF TO MOVE. UNTIL THE FNT MOVES OUT TO SEA THERE WILL REMAIN A CHC OF SHRA/TSTMS. BEHIND THE FNT COOLER AND MUCH LESS HUMID AIR FOLLOWS WITH HIGH PRESSURE MOVING IN ALONG WITH 850 MB TEMPS DROPPING TO AROUND PLUS 10 C. THE IMPROVING WX MAY ARRIVE ON THURSDAY...AT LEAST N/MT ZONES BUT MAY TAKE UNTIL LATE IN THE DAY TO REACH THE COAST. THE HIGH MOVES THRU FRIDAY AND SATURDAY WITH PLEASANT SUMMER WX... FOLLOWED BY APPROACHING LOW PRESSURE UNDER AN UPPER LVL TROF THAT COULD BRING SHRA/TSTMS BACK INTO THE REGION ON SUNDAY AS TEMPS AND HUMIDITY LEVELS RISE ONCE AGAIN. USED A BLEND OF VARIOUS MODELS...HPC GUIDANCE...PREVIOUS FCST FOR PERSISTENCE AND CLIMATOLOGY FOR THE LONG TERM FCST. && .AVIATION /02Z MONDAY THROUGH FRIDAY/... SHORT TERM...AREAS OF IFR WITH SOME REGIONS LIFR OVERNIGHT AS DENSE FOG DEVELOPS IN PORTIONS OF MAINE AND NEW HAMPSHIRE. THE FOG WILL LIFT MONDAY MORNING. FOG WILL REFORM MANY AREAS MONDAY NIGHT AS WELL...WITH A CONTINUATION OF RELATIVELY CLEAR SKIES...LIGHT WINDS AND HUMID CONDITIONS. LONG TERM /TUESDAY THROUGH FRIDAY/...ISOLD SHRA/TSTMS COULD PRODUCE MVFR CONDITIONS LATE TUESDAY AFTERNOON AND EARLY EVENING. A BETTER CHC FOR SHRA/TSTMS WITH IFR CONDITIONS WEDNESDAY AND WEDNESDAY NGT WITH POTENTIAL FOR STRONG/SVR TSTMS WEDNESDAY AFTERNOON AND EVENING. && .MARINE... SHORT TERM...LIGHT WINDS AND SEAS EXPECTED. WINDS WILL LOCALLY BE ONSHORE NEAR THE COAST. LONG TERM /TUESDAY THROUGH FRIDAY/...S SW FLOW MAY INCREASE TO MINIMAL SCA LEVELS WEDNESDAY AND WEDNESDAY NGT AHEAD OF AN APPROACHING COLD FNT. THIS MAY ALSO PUSH SEAS TO SCA LEVELS. OTHERWISE WINDS/SEAS BELOW SCA LEVELS. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...NONE. NH...NONE. MARINE...NONE. && $$

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