Area Forecast Discussion
Issued by NWS Portland, ME

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486 FXUS61 KGYX 211818 AFDGYX Area Forecast Discussion National Weather Service Gray ME 218 PM EDT Fri Jul 21 2017 .SYNOPSIS... A weak front drops south across the area tonight and Saturday before stalling over southern New England. Several areas of low pressure will track through southern New England along this front late this weekend and into early next week, providing a chance of rain while keeping temperatures cool. && .NEAR TERM /THROUGH TONIGHT/... NWS Doppler Radar mosaic shows scattered convection has developed over Quebec, northern Maine, and into New Brunswick as surface heating...a series of weak boundaries...and an approaching shortwave work in tandem. Modified raobs show CAPEs of 1000 to 1500 j/kg with a few storms across our far northern and eastern Maine zones capable of strong wind gusts and hail through early evening. Otherwise...a dry night as a surface cold front settles southward into the region. lows will range from the upper 50s to mid 60s. && .SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/... On Saturday...a blend of clouds and sunshine as the cold front continues to settle south across the area. There could be an isolated afternoon shower over the southern half of New Hampshire into adjacent southwest Maine...otherwise a dry and warm summer day with highs ranging from 75 to 80 along the international border to the 80s elsewhere. The front will continue to press south Saturday night...with mostly clear skies from Northern New Hampshire through Central Maine and partly cloudy skies for the remainder of the area as high pressure noses in from eastern Canada. Lows will range from around 50 near the international border with 50s to near 60 elsewhere. && .LONG TERM /SUNDAY THROUGH THURSDAY/... On Sunday the large upper low over eastern Canada and northern Maine will begin moving east as a short wave kicker approaches in the mid level flow in the vicinity of the northern Great Lakes. This short wave opens up as it digs south into New England Monday and Tuesday. Ridging fills in briefly on Wednesday before another stronger upper low follows a similar path for the end of the work week. This active pattern looks to continue keeping precipitation chances in the forecast. As far as temperatures, the hot air is suppressed southward with NAEFS showing negative temperature anomalies at 925mb Monday through Wednesday. Highs only warm into the 60s and 70s each day due to cloud cover and rain (this is several degrees below normal for this time of year for PWM and CON). Overnight lows will generally be in the 50s with a few 60s creeping back in (right around normal). At the surface, a chain of weak low pressure centers develop along a baroclinic zone that will be initially centered to our south and west Sunday. Precipitation will spread from west to east Sunday night into the Monday as the system shifts northeast. This slow moving, vertically stacked system will have high PWAT air to work with (although it will be higher to the south) as well as moderately deep warm cloud depths... especially Monday night into Tuesday. Mean specific humidity anomalies will be +2-3 standard deviations above normal according to the NAEFS. Therefore heavy rain and localized flooding will be a prime concern for the 48 hr period. Current model timing for Sunday night into Monday`s precipitation (arriving after dark) would preclude any real severe weather threats at this time. Thunderstorms chances increase Monday into Tuesday morning however as lapse rates increase, reaching around 7 C/km Monday night preceding the short wave passage. A cold front sweeps through during this time and should help focus storms. Depending on how much heating we get there may be marginally severe storms with damaging wind and hail early on but again antecedent cloud cover will be an issue. Wednesday high pressure crosses the area. Another cold front marches through Thursday night into Friday, but parent forcing is so far forecasted to be well displaced in Canada. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/... Short Term...VFR with isold MVFR in tsra psb vicinity of International border through early evening. Lcl IFR conditions are psb Sat AM and again Sun AM in valley stratus and fog. Long Term...Cool and unsettled weather returns with showers and MVFR ceilings being the norm for the daytime and IFR in fog and stratus returning into the overnight from Sunday through Tuesday as moisture pools along frontal boundaries. LLWS may be a concern Sunday with near calm winds at the surface and an increasing LLJ near LEB and HIE. && .MARINE... Short Term /through Saturday night/...Winds and seas are expected to remain below SCA threshold through the period. Long Term...Winds and seas remain below SCA criteria through the end of the weekend and into next week. A frontal boundary stalled over or near the waters will keep winds light and stratus and dense fog over the waters. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$ SYNOPSIS...Schwibs NEAR TERM...Schwibs SHORT TERM...Schwibs LONG TERM...Hanes AVIATION...Schwibs MARINE...Hanes/Schwibs

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