textproduct: Gray - Portland

WHAT HAS CHANGED

Manually increased PoPs across much of NH and southwestern ME to account for an area of light rain that is continuing to pivot ESE. This is poorly represented in most hi-res guidance but generally expecting this to exit these areas within the next couple of hours. Otherwise, adjusted the aviation section for the 12Z TAF package.

KEY MESSAGES

1. Stubborn upper low shifts east today with high pressure building in by Monday for fair weather and warmer temperatures.

2. Low pressure passes north of the area late Wednesday through Thursday with the attendant cold front bringing chances for showers and thunderstorms. Gusty northwesterly winds will be possible behind the cold front Thursday.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

Another embedded wave rotating through the upper low over Nova Scotia will continue chances for showers, mainly over NH through this morning. Cyclonic flow aloft and diurnal instability will bring a mix of sun and clouds today and potential for an isolated shower. As high pressure attempts to build in from the west with low pressure near Nova Scotia northerly winds will remain brisk, particularly over central Maine and the mountains. Peak gusts at lower elevations will approach 25 mph with lower gusts to the southwest over southern NH. Mostly clear skies tonight will favor radiational cooling while winds may limit decoupling. Nevertheless, it will be cool tonight with lows in the 40s and potential for northern valleys to dip into the upper 30s.

High pressure and rising heights will bring fair weather Monday and warmer temperatures. Highs will range from the mid 70s north to low 80s across the south. A weak cold front will wash out over the area Monday night that may have enough moisture for some isolated showers. Otherwise, dry weather continues through Tuesday with broad high pressure over the Northeast.

KEY MESSAGE 2 DESCRIPTION...

On Wednesday, an upper-level low over Manitoba will shift to the southeast and deepen over the northeast US. This will likely allow for a cold front to move across the area Wednesday night, bringing overnight thunderstorms. Storms could produce wetting rains, but should not be much more than that. Behind the front, a strong pressure gradient could allow for some breezy northwest winds to impact the region during the day Thursday. High pressure looks to move in for next weekend, with radiational cooling potentially allowing for some below average low temperatures then.

AVIATION /10Z SUNDAY THROUGH THURSDAY/

Through 12Z Monday... -RA and MVFR-IFR ceilings will persist across NH through 14Z. Otherwise cigs/vis VFR with SCT MVFR cig at times. A period of IFR/LIFR is likely at HIE/LEB in valley fog. Mainly VFR during the day today with NW winds increasing this afternoon with gusts 15 to 20 kts. Mainly VFR tonight except for valley fog likely bringing IFR/LIFR to LEB and HIE. No LLWS is anticipated through the period.

Outlook:

Monday: VFR, no sig wx.

Tuesday: VFR conditions expected.

Wednesday: Local MVFR or lower conditions possible in showers and thunderstorms. LLWS possible near the coast.

Thursday: Becoming VFR. Northwest wind gusts at or above 25 kt possible.

Friday-Saturday: VFR conditions expected.

MARINE

North winds continue through today and much of Monday as broad low pressure influences the region while high pressure attempts to build in from the west. Gusts should remain below SCA criteria, but some gusts around 25 kts are possible this morning on the outer waters. Gusts will lower this afternoon and will remain around 15 kts into Monday. Winds will become light and variable on Tuesday

Southwest winds increase Wednesday with SCA conditions likely over all waters Wednesday night. Seas will continue building overnight to 5 or 6 feet outside of the bays. Winds shift to northwesterly Thursday and remain breezy, so seas will only gradually diminish thru the day. Winds and seas fall below SCA thresholds Fri into the weekend.

GYX WATCHES/WARNINGS/ADVISORIES

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