textproduct: Gray - Portland

WHAT HAS CHANGED

No significant changes with this forecast update this early Friday morning.

KEY MESSAGES

1. WNW winds will gust 20 to 30 mph today with isolated showers. High pressure brings fair weather Saturday followed by frost potential to the coast Saturday night.

2. Rain chances increase late Sunday and persist into Monday as the remnants of Isaias and approaching cold front cross the Northeast. More showers possible with a cold front on Tuesday.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

Cyclonic flow aloft will continue through today with a surface trough swinging across the area early this afternoon. This bring chances for isolated showers while much of the area will experience partly to mostly sunny skies today. Hi res guidance has backed off a bit on the wind fields while mixing to around 700 mb seems likely. Mean momentum transfer is around 25 kts with winds at the top of the mixed layer are 30-35 kts. This will likely translate to peak gusts around 30 mph with sporadic higher gusts. There will also be potential for higher gusts with any sustained shower.

High pressure builds in Friday night into Saturday that will allow gusty winds to subside Friday night. Saturday will be a pleasant day with sunny skies and high temperatures ranging from the upper 40s near the Canadian Border to low 60s south of the mountains. The center of the high will drift into the Gulf of Maine Saturday night while it will still likely provide favorable conditions for radiational cooling. This will likely lead to lows dropping below freezing for much of the interior with frost potential all the way to the coast.

KEY MESSAGE 2 DESCRIPTION...

Latest forecast guidance continues to indicate that remnant moisture from Tropical Cyclone Isaias will bring a period of rainfall to the area late Sunday into Monday morning. Rainfall amounts will likely be light with amounts ranging from around 1/2" across portions of southern NH and southwestern ME to less than 1/10" of an inch across northern locations. Partial clearing is likely later Monday with above avg high temperatures into the upper 60s/low 70s south of the mtns.

After a warm Monday night, a cold front and associated wave of low pressure will cross from the north on Tuesday. This will bring another period of showery weather and gusty SW winds before turning to the NW Tuesday night as CAA increases behind the front. Cooler temperatures will then prevail mid to late week with mainly dry conditions.

AVIATION /12Z FRIDAY THROUGH TUESDAY/

Through 06Z Saturday...Mainly VFR through today. The exception will be potential for -SHRA at HIE that could bring TEMPO MVFR or lower during the afternoon. WNW winds will increase after 12Z with gusts around 25 kts from mid morning into the afternoon. Winds relax tonight with continued VFR. Valley fog cannot be ruled out tonight.

Outlook:

Saturday: VFR Expected.

Monday-Tuesday: Periods of MVFR or lower in low cigs and periods of showers. Some VFR is likely late Monday and Tuesday morning.

MARINE

West winds freshen this morning with gusts approaching 25 kts after day break...persisting into the afternoon. Seas will generally stay below 5 feet today. Winds shift NW tonight with gusts around 20 kts while gusts to 25 kts are possible along the outer waters offshore of the Mid Coast. At this time it looks as though 25 kt gusts won't be long lived or widespread, precluding a SCA. High pressure crosses the waters Saturday and Saturday night for quiet conditions. High pressure shifts SE of the waters Sunday with an area of low pressure approaching from the SW. This will bring potential for a period of SCA conditions into Sunday night. Low pressure will pass near the waters Monday morning followed by a cold front crossing late Tuesday.

GYX WATCHES/WARNINGS/ADVISORIES

ME...None. NH...None. MARINE...None.