Area Forecast Discussion
Issued by NWS Portland, ME

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759 FXUS61 KGYX 010729 AFDGYX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAY ME 329 AM EDT SUN MAY 1 2016 .SYNOPSIS... LOW PRESSURE OVER THE EASTERN GREAT LAKES WILL MOVE NORTHEAST TOWARD NEW ENGLAND TODAY AND TONIGHT... SPREADING RAIN INTO THE REGION. RAINY WEATHER PERSISTS INTO MONDAY WHEN LOW PRESSURE MOVES EAST INTO THE CANADIAN MARITIMES. WEAK HIGH PRESSURE WILL MOVE OUT OF CANADA AND THROUGH NORTHEAST NEW ENGLAND ON TUESDAY. LOW PRESSURE DEVELOPING OFF THE CAROLINAS WILL TRACK NORTHWARD INTO NEW ENGLAND WEDNESDAY NIGHT INTO THURSDAY BRINGING ANOTHER CHANCE OF RAIN. && .NEAR TERM /TODAY/... MODELS CONTINUE TO SHOW PRECIP STRUGGLING TO MOVE EAST ACROSS THE CT VLY TODAY. MID LVL THERMAL ADVECTION IS THE ONLY STRONG FORCING MECHANISM AS 500MB DYNAMIC ARE WEAK AS WAVE ALOFT MOVES INTO RIDGING...AND LOW LEVEL DRY AIR MAKES IT HARD FOR RAIN TO REACH THE GROUND. WILL LKLY SEE SOME SHRA IN NH MIDDAY AND THROUGH THE AFTERNOON...BUT ANY PRECIP WILL TAKE TO AT LEAST LATE AFTERNOON TO MAKE IT INTO ME. STILL WILL SEE BKN-OVC SKIES THRU THE DAY...AND ONSHORE FLOW WILL LIMIT HIGHS TO THE LOW-MID 50S WITH THE WARMEST SPOTS INTERIOR KENNEBEC AND PENOBSCOT VLY REGIONS. && .SHORT TERM /TONIGHT AND MONDAY/... INITIAL 500MB WAVE SHEAR OUT OVERNIGHT AS IT MOVES THRU THE RIDGE...AND COULD SEE SOME RESIDUAL SHRA FROM THIS SYSTEM THIS EVENING...OVERALL PRECIP LOOKS LIMITED TO JUST SOME SHRA OVERNIGHT. LOOK FOR FOG AND MAYBE SOME SPOTTY DZ TO DEVELOP AS BOUNDARY LYR MOISTURE STARTS TO INCREASE. LOWS WILL DROP OFF A BIT AS THERE IS A BIT OF CAA BEHIND THAT WEAKENING FIRST WAVE...BUT SHOULD ONLY DROP TO UPPER 30S TO LOW 40S. ON MONDAY...WILL SEE A BETTER SFC LOW DEVELOP S OF NEW ENGLAND AND TRACK JUST S AND E OF THEN GULF OF ME. THERE WILL BE SOME WEAK PHASING OF A 500MB WAVE TO THE N WITH THIS SYSTEM AS IT PASSES BY...AND BEST CHC FOR RAIN WILL BE MON AFTERNOON. MAYBE A QUARTER TO HALF INCH ON MONDAY. ONSHORE FLOW WILL CONTINUE AND IT WILL BE COOL WITH HIGHS IN THE MID 40S N...TO AROUND 50 IN THE S. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... LOW PRESSURE MOVES EAST INTO THE MARITIMES WITH HIGH PRESSURE BUILDING IN BRIEFLY BEHIND IT MONDAY NIGHT INTO TUESDAY. THIS WILL BE THE BEST CHANCE IN THE LONG TERM PERIOD TO SEE FREEZING TEMPERATURES... BUT PERSISTENT LOW LEVEL MOISTURE WILL LIKELY KEEP NIGHTTIME TEMPERATURES ACROSS MUCH OF THE AREA ABOVE FREEZING. ON TUESDAY A POTENT SHORTWAVE TROUGH WILL DIVE SOUTHWARD OUT OF CANADA AND THROUGH THE WESTERN GREAT LAKES. IN PART BECAUSE OF LINGERING TROUGHING OVER THE CENTRAL UNITED STATES... THIS SHORTWAVE TROUGH WILL BE ABLE TO DIG SO FAR SOUTH THAT IT WILL BEGIN TO CUT ITSELF OFF FROM THE WESTERLIES... LEAVING A SLOW MOVING CUT OFF LOW OVER THE UPPER OHIO VALLEY AND CENTRAL APPALACHIANS WEDNESDAY AND THURSDAY. THE PLACEMENT OF THIS TROUGH WILL SET UP A DEEP SOUTHERLY FLOW FROM THE TROPICS. AN INITIAL WAVE EMBEDDED WITHIN THE OVERALL TROUGH WILL CAUSE LOW PRESSURE TO FORM AT THE SURFACE NEAR THE CAROLINA COAST ON WEDNESDAY... TRACKING NORTHWARD TOWARD NEW ENGLAND THURSDAY. MODELS SEEM TO BE COMING INTO BETTER AGREEMENT THAT WEDNESDAY NIGHT INTO THURSDAY WILL BE THE BEST CHANCE OF RAIN DURING FOR NORTHERN NEW ENGLAND... THOUGH WITH THE CUT OFF LOW VERY SLOW TO MOVE OUT WE WILL HAVE TO MAINTAIN A CHANCE OF RAIN THROUGH THE WEEKEND. COULD SEE FOG AND DRIZZLE BEGINNING NEAR THE COAST AS EARLY AS WEDNESDAY MORNING DUE TO A MOIST ONSHORE WIND. WITH PERSISTENT TROUGHING OVER THE AREA... TEMPERATURES WILL BE NEAR OR BELOW NORMAL FOR DAYTIME HIGHS DUE TO PLENTY OF CLOUD COVER... COOL TEMPERATURES ALOFT... AND A FREQUENT ONSHORE LOW LEVEL FLOW. LOW TEMPERATURES APPEAR LIKELY TO REMAIN ABOVE FREEZING THROUGH THE WEEKEND DUE TO THE INCREASED LOW LEVEL MOISTURE. && .AVIATION /07Z SUNDAY THROUGH THURSDAY/... SHORT TERM...SHOULD HANG ONTO VFR...DESPITE A FEW SHRA...AT LEAST INTO EARLY TO MID-AFTERNOON...WITH MVFR MOVING INTO NH TERMINALS THIS AFTERNOON...AND EVENTUALLY INTO ME THIS EVENING. WILL PROBABLY SEE IFR CIGS DEVELOP TONIGHT...ALTHOUGH TIMING REMAINS UNCERTAIN...BUT PROBABLY BY MIDNIGHT AT COASTAL TERMINALS...MAYBE A LITTLE LATER. IFR SHOULD HANG ON THROUGH THE DAY MONDAY...ALTHOUGH SOME TEMPO IMPROVEMENT MAY BE POSSIBLE MON MORNING. LONG TERM...SHOULD SEE IMPROVEMENT TO VFR TUESDAY. BUT AN ONSHORE FLOW WILL START TO BRING IN LOW CLOUDS AND DRIZZLE AS EARLY AS WEDNESDAY MORNING. EXPECT GENERALLY IFR OR LOWER CONDITIONS WEDNESDAY AND THURSDAY AS LOW PRESSURE MOVES TOWARD THE AREA AND SPREADS RAIN INTO THE REGION. && .MARINE... SHORT TERM...WEAK FLOW HOLD INTO TONIGHT BEFORE A SFC LOW TRACKS JUST OF THE GULF OF THE GULF OF ME ON MONDAY AND WINDS/SEAS WILL LIKLY REACH BORDERLINE SCA CRITERIA. LONG TERM...EXPECT A LIGHT EASTERLY OR NORTHEASTERLY BREEZE THROUGH WEDNESDAY. WINDS COULD PICK UP A BIT WEDNESDAY NIGHT INTO THURSDAY AS LOW PRESSURE TRACKS UP THE EAST COAST AND TOWARD NOVA SCOTIA. WAVE HEIGHTS WILL ALSO BE INCREASING ON THE NORTHEASTERLY FETCH. && .FIRE WEATHER... PERSISTENT ONSHORE FLOW BEGINNING TODAY THROUGH MONDAY WILL MEAN MODERATE TO HIGH RH...AND SOME SHRA ARE POSSIBLE TODAY INTO TONIGHT...WITH WETTING RAINS EXPECTED MONDAY. && .TIDES/COASTAL FLOODING... A PERIOD OF HIGH ASTRONOMICAL TIDES IS COMING UP FROM THURSDAY THROUGH THE WEEKEND. THE HIGHEST TIDE IS FRIDAY NIGHT WHEN PORTLAND REACHES 11.9 FEET AT 11:35 PM. WILL NEED TO WATCH THIS TIME PERIOD FOR POSSIBLE COASTAL FLOODING AS WINDS WILL GENERALLY BE EASTERLY TO NORTHEASTERLY. COULD CONCEIVABLY SEE SOME COASTAL FLOODING ISSUES AS EARLY AS THE THURSDAY EVENING TIDE DEPENDING ON HOW THE TRACK/STRENGTH OF THE LOW SHAKES OUT. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...NONE. NH...NONE. MARINE...NONE. && $$ NEAR TERM...CEMPA SHORT TERM...CEMPA LONG TERM...KIMBLE

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