Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 122226 AFDGYX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAY ME 625 PM EDT SAT JUL 12 2014 .SYNOPSIS... A WARM FRONT PUSHES TO THE NORTHEAST TONIGHT 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. && .NEAR TERM /THROUGH TONIGHT/... 625 PM...JUST A FEW MINOR ADJUSTMENTS TO THE GOING FORECAST BASED ON LATEST TRENDS IN OBSERVATIONAL DATA. A NICE EVENING WILL CONTINUE. PREVIOUSLY... AS THE CENTER OF HIGH PRES BECOMES ANCHORED OFF THE COAST A RETURN SLY FLOW WILL DEVELOP TONIGHT. CLOUDS WILL BE ON THE INCR TONIGHT AS WELL AS DEWPTS. LOW TEMPS WILL ALSO BE MILDER AS THE WAA DEVELOPS. USED A BLEND OF MODEL GUID FOR MINS TONIGHT. SOME VLY FOG MAY ALSO DEVELOP LATER TONIGHT ONCE AGAIN IN THE MERRIMACK AND LOWER CT RIVER VALLEYS. && .SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/... 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 /19Z SATURDAY THROUGH THURSDAY/... SHORT TERM...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 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. && .MARINE... SHORT TERM...A DEVELOPING SLY 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. && .TIDES/COASTAL FLOODING... 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. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...NONE. NH...NONE. MARINE...SMALL CRAFT ADVISORY FROM 2 PM SUNDAY TO 8 AM EDT MONDAY FOR ANZ150>154. && $$

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