Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 260320 AAA AFDGYX AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE GRAY ME 1120 PM EDT FRI JUL 25 2014 .SYNOPSIS... HIGH PRESSURE OVER THE REGION TONIGHT MOVES INTO THE WESTERN ATLANTIC ON SATURDAY. AN UPPER LEVEL TROUGH OF LOW PRESSURE MOVES INTO THE AREA ON SUNDAY AND BRINGS SHOWERS AND ISOLATED THUNDERSTORMS THROUGH MONDAY OR TUESDAY. HIGH PRESSURE BUILDS IN AGAIN FOR THE END OF THE WEEK. && .NEAR TERM /THROUGH SATURDAY/... UPDATE...HAVE ADDED HAZE TO THE FORECAST TO ACCOUNT FOR FAIRLY DENSE CANADIAN SMOKE. MOST METARS ACROSS THE REGION SIT BETWEEN 6 AND 8 SM...AND SATELLITE INDICATES SMOKE MAY NOT BEGIN TO THIN OUT UNTIL NEAR SUNRISE IF NOT LATER. FOR NOW WILL KEEP IT IN THRU SUNRISE...ALONG WITH VALLEY FOG. PREVIOUS DISCUSSION...AFTERNOON CUMULUS AND ANY ISOLATED SHOWERS SHOULD DISSIPATE THIS EVENING... LEAVING A MOSTLY CLEAR SKY AND CALM WINDS. THIS WILL ALLOW GOOD RADIATIONAL COOLING CONDITIONS WITH TEMPERATURES FALLING INTO THE 50S (40S NORTH) WHICH IS NOT QUITE AS COOL AS LAST NIGHT DUE TO A LITTLE MORE MOISTURE IN THE AIR. VALLEY LOCATIONS WILL LIKELY SEE FOG AGAIN... WITH DENSE FOG POSSIBLE IN THE CONNECTICUT RIVER VALLEY. && .SHORT TERM /SATURDAY NIGHT/... SOUTHWEST FLOW ACROSS THE AREA ON SATURDAY BRINGS WARMER TEMPERATURES AND HIGHER HUMIDITY. MAY SEE SOME SCATTERED SHOWERS AND AN ISOLATED THUNDERSTORM IN THE MOUNTAINS IN THE AFTERNOON RESULTING FROM THE DIURNALLY DRIVEN INSTABILITY. THIS MAY BE AIDED BY A WEAK SHORTWAVE TROUGH PASSING NEAR THE CANADIAN BORDER. OVERALL INSTABILITY LEVELS ARE FAIRLY LOW... SO THUNDER CHANCES ARE FAIRLY LOW. BROAD UPPER TROUGH BEGINS TO MOVE INTO THE AREA SATURDAY NIGHT. THE FIRST IN A SERIES OF MORE DISTINCT SHORTWAVE TROUGHS WITHIN THE BROADER TROUGH WILL MOVE ACROSS NEW ENGLAND SATURDAY NIGHT... WITH SHOWERS SPREADING WEST TO EAST ACROSS THE REGION BEGINNING LATE IN THE EVENING. COULD SEE AN ISOLATED THUNDERSTORM AS TEMPERATURES COOL ALOFT. LOWS WILL BE WARMER... IN THE UPPER 50S AND LOW 60S DUE TO CLOUDS AND MORE MOISTURE. && .LONG TERM /SUNDAY THROUGH FRIDAY/... A PERIOD OF UNSETTLED WX WILL LAST THRU THE ENTIRE LONG TERM FCST PERIOD ...ESPECIALLY FOR THE FIRST TWO DAYS. THE UPPER LVL PATTERN SHOWS A CUTOFF LOW OVER ERN CANADA WELL TO OUR N ON SUNDAY. A STRONG SHORT WAVE TROF DRIVES SE THRU THE NRN TIER OF STATES AS IT ROTATES AROUND ON THE S SIDE OF THE LARGER CUTOFF LOW. THIS KICKS OUT A WEAKER SHORT WAVE TROF INTO THE NE U.S. WHICH BRINGS US OUR FIRST ROUND OF UNSETTLED WX WITH SHRA/TSTM ACTIVITY. ANOTHER WEAK SHORT WAVE TROF SPINS OUT DIRECTLY AHEAD OF THE APPROACHING STRONG SHORT WAVE TROF FOR SUNDAY NGT. NEXT THE STRONG SHORT WAVE TROF WEAKENS AS IT SHEARS OUT TO THE NE, CROSSING THE NE U.S. ON MONDAY. THIS TROF IS NOW MOVING TO THE E SIDE OF THE LARGER CUTOFF LOW THAT IS NOW EXPANDING TO INCLUDE ERN CANADA INTO MUCH OF THE ERN U.S. WHILE THIS UPPER LVL PATTERN IS EVOLVING THE SFC SHOWS DISORGANIZED AREA OF LOW PRESSURE ACROSS MUCH OF THE GREAT LAKES REGION WITH A WARM FNT EXTENDING TO THE E AND APPROACHING THE FCST AREA FROM THE S. WITH TIME THE SFC LOW BECOMES BETTER ORGANIZED WITH A TRAILING COLD FNT MOVING THRU THE FCST AREA ON MONDAY. THE FNT BECOMES STALLED OVER THE ERN SEABOARD DUE TO THE UPPER LVL CUTOFF LOW PROVIDING A BROAD SW FLOW ALOFT OVER THE ERN U.S. WHICH NEARLY PARALLELS THE NOW STALLING FNT. WEAK LOW PRESSURE ALSO FORMS ALONG THIS FNT AND TRACKS N NE ALONG THE BOUNDARY ON TUESDAY. ON WEDNESDAY THE CUTOFF LOW IS LIFTING TO THE N BUT MAINTAINS A WEAKER SHORT WAVE TROF EXTENDING S THRU THE ERN SEABOARD. THIS KEEPS A SW FLOW ALOFT BUT ALSO PUSHES THE FNT OFFSHORE AND BRINGS A DRY SLOT NE ALONG THE ERN U.S. THOUGH THIS SUGGESTS DRY WX THE CYCLONIC FLOW ALOFT AND NEARBY FNT WILL KEEP A SLGT CHC OF SHRA ACTIVITY AROUND. THIS PATTERN CONTINUES THURSDAY AND FRIDAY AS A SERIES OF WEAK UPPER LVL IMPULSES ROTATE AROUND THE MAIN CUTOFF LOW PROVIDING THE IMPETUS FOR A SLGT CHC SHRA/POSSIBLE TSTM ACTIVITY AS THE SFC FNT OFF SHORE WIGGLES BACK AND FORTH AS WEAK SFC LOWS TRACK ALONG IT DUE TO THE PASSAGE OF THE UPPER LVL IMPULSES. USED A BLEND OF VARIOUS MODELS...HPC GUIDANCE...PREVIOUS FCST FOR PERSISTENCE AND CLIMATOLOGY FOR THE LONG TERM FCST. && .AVIATION /03Z SATURDAY THROUGH WEDNESDAY/... SHORT TERM...WILL SEE VALLEY FOG AGAIN TONIGHT AT LEBANON AND WHITEFIELD. DEW POINTS ARE A BIT HIGHER THAN YESTERDAY SO CONFIDENCE IN FOG IS A BIT HIGHER AS WELL. CONCORD HAD A BRIEF PERIOD OF SCATTERED LOW CLOUDS THIS MORNING... AND SUSPECT THAT IS A HINT THAT FOG MAY OCCUR TONIGHT GIVEN GREATER MOISTURE AND SIMILAR RADIATIONAL COOLING CONDITIONS. OTHERWISE EXPECT VFR CONDITIONS THROUGH SATURDAY EVENING. SHOWERS MOVE ACROSS THE REGION SATURDAY NIGHT WITH MVFR/IFR CONDITIONS POSSIBLE AT TIMES. LONG TERM /SUNDAY THROUGH WEDNESDAY/...AN EXTENDED PERIOD OF UNSETTLE WX WITH SHRA/TSTMS AND MVFR/IFR CONDITIONS POSSIBLE... ESPECIALLY SUNDAY THRU MONDAY AND LESS LIKELY TUESDAY THRU WEDNESDAY. && .MARINE... SHORT TERM...SOUTHWEST FLOW STRENGTHENS OVER THE WATERS AS THE CENTER OF HIGH PRESSURE MOVES OFFSHORE AND A TROUGH OF LOW PRESSURE APPROACHES FROM THE WEST. CURRENTLY EXPECT WINDS TO STAY BELOW ADVISORY LEVELS. ALTHOUGH GUIDANCE CONTINUES TO FORECAST 5 TO 6 FT WAVES... THIS SEEMS A BIT TOO HIGH GIVEN THE SOUTHWEST WINDS HAVE A SHORTER FETCH AND WINDS ARE NOT THAT STRONG. GREATEST CHANCE OF 5 FT WAVES WILL BE IN THE CENTRAL GULF OF MAINE WATERS EAST OF PORTLAND. LONG TERM /SUNDAY THROUGH WEDNESDAY/...S SW FLOW AHEAD OF AN APPROACHING COLD FNT MAY CREATE SCA WIND GUSTS OVER THE OPEN WATERS SUNDAY INTO MONDAY. THE CONTINUED ONSHORE FLOW WILL LIKELY PUSH SEAS TO SCA LEVELS SUNDAY THRU MONDAY NGT. THE FNT STALLS NEAR OR JUST E OF THE WATERS TUESDAY THRU WEDNESDAY KEEPING WINDS AND SEAS BELOW SCA LEVELS. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...NONE. NH...NONE. MARINE...NONE. && $$ NEAR TERM...LEGRO

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