National Weather Service (2024)

Area Forecast Discussion
Issued by NWS Portland, ME

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-- Discussion containing changed information from previous version are highlighted. --254FXUS61 KGYX 130238AFDGYXArea Forecast DiscussionNational Weather Service Gray ME1038 PM EDT Sun May 12 2024.SYNOPSIS...High pressure gradually builds in and moves offshore throughtomorrow. A warm front stalls through central New England onTuesday, then a slow moving cold front stalls on Wednesday. Lowpressure passing south of New England spreads moisture andshowers in from late Tuesday into Thursday. Conditions dry outlate in the week as New England sees a period between systems,and then likely turns unsettled again by late next weekend.&&.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
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0238Z Update... Temperatures continue to fall through the 40sin most areas, albeit at a slower rate than the last severalnights. Patchy fog will likely develop later tonight, howeverits extent will be driven by the amount of cloud cover over theregion.Patchy fog will mainly be confined to the northern mountainstonight, somewhat different than the last couple chilly nightsover southern areas.Update...Showers continue over the forecast area as of 2130Zper latest radar imagery and surface observations. However, withlarge surface dew point depressions, some of the echoes are notreaching the ground with plenty of dry air in the mid levels inthe latest GYX sounding. In any case, have upped pops acrossportions of the region, especially in Maine. In western Maine,the latest HRRR has showers expanding through about 00Z beforedissipating overnight.Have nudged temperatures downwards for the overnight lows,especially in the Midcoast region where clear skies may allowfor temperatures to drop into the 30s. Have introduced patchyfrost into the forecast for the early morning and earlyafternoon hours.Will continue with patchy fog and may need to expand to areasthat receive rainfall this evening.Prev Disc...Weak sfc high just tour S, with cool upper level closed lowoverhead, and very weak forcing in the mid levels, has allowedfor some showers to develop, mainly over the mtns early thisafternoon, but they will move S during the mid to lateafternoon. I think calling them sct or isolated is probably thebest way to describe them, and they are all light, producinggenerally a few hundredths of an inch at best. I do think someof the clouds clear out tonight, but also with mid levelforcing, I dont think they clear out completely until late, andTds are higher than Sat night. So frost is not expected inactivated zones. Otherwise lows will drop into the upper 30s inthe mtns and mostly the low 40s in the S.
-- End Changed Discussion --&&.SHORT TERM /6 AM MONDAY MORNING THROUGH TUESDAY/...On Mon, we manage to squeeze into weak ridging at all levelsabove the sfc, with a more SW flow at the sfc, as we sit betweensystems. We should a mainly sunny morning, with more clouds inthe afternoon, but still a fair amount of sun. The SW flow isweak, so so coastal zones S of Casco Bay will likely a partialonshore component to the wind, but won;t be that much coolerthan inland except near the midcoast. Highs range from around 60on the mid coast to the low mid 60s inland, and near 70 in S NH.Monday night will see clouds and showers move in during theevening and overnight as a warm front moves in. Mins will bemilder and mostly in the 40s.&&.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...Overview...A warm front brings warm temperatures to parts of the forecastarea on Tuesday. A cut off low gradually moves through the OhioRiver Valley and south of New England Wednesday and Thursday. Ashort wave ridge passes through on Saturday, and then anothersystem approaches New England by next Sunday.Details...As a cut off low lingers across western Quebec, the warm frontassociated with the low makes progress into New Hampshire andparts of western Maine on Tuesday. The front likely stallssomewhere near central Maine without fully clearing the areaduring the daytime. With this, temps warm into the 70s to near80 across southern New Hampshire, while parts of the MidCoastand northwestern zones may fail to make it past the upper 50s.This forecast holds with the NBM temps for now, but the gradientis likely to be a little stronger than what it currently beingshown. The big question is just how far northeastward the frontmakes it, with the MidCoast, Central Maine, and all northernareas standing the best chance for the front not to make enoughprogress for warmth.A cold front sags southward late Tuesday through Wednesday,with showers expanding along this front as a slow moving lowtracks south of the area and sends moisture northward. Showersbecome likely by the afternoon across northern areas on Tuesday,and gradually increase as the front moves southward intocoastal areas by Wednesday. The bulk of the moisture stays southof the region, but the slowing front serves to focus showeractivity on Wednesday, and possibly into Thursday as well. Thefront stalls, likely through the middle of the forecast areafrom east to west. There will be wet periods during thistimeframe into Thursday, but coverage looks to gradually lessenas the forcing weakens. Some showers still can`t be ruled out onFriday as the low tracks out to sea.A quick shortwave ridge likely passes through on Saturday, butthe next system will be quick on it`s heals with moisturespreading in from the southwest. It`s still unclear whether thisridge will pass through during the day on Saturday, or if itmoves through a bit more quickly and allows showers to move inby the afternoon hours. We`ll need to wait a little longer toiron out these details, but that looks like the set up at thispoint.&&.AVIATION /02Z MONDAY THROUGH FRIDAY/...Short Term...VFR will persist through Monday and into Mondayevening, but cigs and vis will drop in ?SHRA overnight, at leastto MVFR, and maybe some periods of IFR.Long Term...VFR conditions are expected across southern andwestern terminals on Tuesday, but some MVFR conditions arelikely across coastal terminals during the day, especially atRKD where IFR conditions are possible in marine fog. Ceilingslower at all terminals with showers Tuesday night, with MVFRconditions likely and periods of IFR possible. These conditionscontinue on Wednesday, and then gradually improve into the dayon Thursday. VFR likely doesn`t return fully until Friday andlasts into Saturday. Restrictions likely return again withshowers Saturday night and Sunday.&&.MARINE...Short Term...Winds/seas stay below SCA criteria into Monday, butcould approach weak SCA winds by Mon evening.Long Term...A cold front slowly approaches the waters onTuesday, and stalls near the coast by Wednesday. A slow movinglow pressure system passes south of the waters Wednesday andThursday. These two features bring freshening southerly flow,becoming easterly by Wednesday and Thursday, with SCA conditionspossible during this time frame. This system slowly moveseastward on Friday, with waves likely lingering near 5ft onFriday.&&.GYX WATCHES/WARNINGS/ADVISORIES...ME...None.NH...None.MARINE...None.&&$$NEAR/SHORT TERM...CannonLONG TERM...Clair