textproduct: Gray - Portland

WHAT HAS CHANGED

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

KEY MESSAGES

1. Fair weather is expected today into Sunday morning under high pressure. Tonight will be chilly with frost potential to the coast and across southern NH.

2. Two shots of beneficial rain are likely early next week. The first arrives late Sunday into Monday morning and the second Tuesday, possibly lasting into Wednesday morning.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

High pressure over the eastern Great Lakes early this morning will drift overhead today into tonight before sliding east offshore on Sunday. This will bring fair weather today with highs ranging from the upper 40s north to low 60s south. Clear skies and calm winds tonight will promote efficient radiational cooling tonight. Lows will drop into the 20s across the north and favorable radiational cooling spots south of the mountains. Elsewhere, lows will be in the low to mid 30s with frost potential to the coast and across southern NH. Frost and Freeze headlines have been issued for final night of the frost/freeze program across remaining active zones.

Warmer and mostly dry weather is expected through much of Sunday. Clouds will increase from SW to NE during the afternoon as moisture from the remnants of Isaias moves northeast into New England. Highs on Sunday will mainly be in the 60s.

KEY MESSAGE 2 DESCRIPTION...

Models remain in decent agreement that deep moisture from the remnants of Isaias will push into the Northeast Sunday and into the forecast area late Sunday into Sunday night. Models also continue to suggest that a surface low will develop near southern New England Sunday night and will track ENE south of the Gulf of Maine Monday. While measurable rainfall is likely south of the mountains late Sunday into Monday morning, the northward extent of measurable rainfall remains in question along with total QPF. The last two runs of the NAM have been quite bullish bringing 1-2 inches along and south of the mountains while this seems to be an outlier compared to other available guidance. The latest NBM brings around 0.5 inches across southern NH with amounts decreasing to the north where areas north of the mountains see less than a tenth of an inch. This seems reasonable given the spread amongst latest guidance.

Rain chances will diminish from north to south Monday morning with the afternoon looking mostly dry with breaks in the cloud cover. It will be warm and almost feel a little humid with highs in the upper 60s and dew points in the upper 50s.

The next chance of rain arrives Monday night into Tuesday as a cold front drops south from Canada and a wave of low pressure forms along the front. Rain will become likely Monday night into Tuesday morning across the mountains and points north while timing of rain chances south of the mountains is variable amongst available guidance. The latest NBM brings at least likely PoPs across much of the area by mid morning Tuesday with PoPs increasing to 70-80 percent Tuesday afternoon. Rain chances will continue into Tuesday night and linger into Wednesday morning. Overall, this system looks to bring another round of beneficial rainfall to the area. Colder air will work into the area Wednesday that will allow for lingering rain showers to change to snow in the higher terrain of the White Mountains. Cool and dry weather is favored the second half of next week under high pressure.

AVIATION /10Z SATURDAY THROUGH WEDNESDAY/

Through Sunday...VFR prevails on Saturday through today and tonight while local IFR will be possible in valley fog. Mainly VFR to start Sunday with clouds thickening and lowering SW to NE. MVFR will become possible across southern NH by Sunday afternoon.

Outlook:

Sunday night-Monday...IFR ceilings are looking increasing likely, especially south of a PWM-LEB line. This area is also most likely to see rain. To the north, MVFR ceilings and rain are possible but less certain. Some improvement is possible later in the day.

Tuesday-Wednesday: Rain showers and IFR to MVFR possible as a front and area of low pressure cross through on Tuesday and Tuesday night. Depending on how quickly the front moves through, Wednesday could be breezy and mainly VFR, but it's possible rain and some degree of restrictions linger into Wednesday.

MARINE

High pressure builds in today and slides over the waters tonight for quiet conditions on the waters. SW winds freshen Sunday as high pressure moves east of the waters while winds and seas remain below SCA thresholds. Low pressure likely passes south of the waters Sunday night into Monday with winds turning east to northeast but currently expected to remain below SCA levels. This system will bring rain and likely fog over the waters. The next system approaches Tuesday with NE to E winds gusting 25-30 kts into Tuesday night. Winds shift northerly Wednesday in the wake of the system with gusts continuing to push 25 kts.

GYX WATCHES/WARNINGS/ADVISORIES

ME...Freeze Warning from 2 AM to 8 AM EDT Sunday for MEZ019-020. Frost Advisory from 2 AM to 8 AM EDT Sunday for MEZ021>028. NH...Frost Advisory from 2 AM to 8 AM EDT Sunday for NHZ010-012-013. MARINE...None.