textproduct: Gray - Portland

WHAT HAS CHANGED

Loaded in the latest surface observations and tweaked sky cover and winds, otherwise the forecast remains on track.

KEY MESSAGES

1. Rain overspreads the area tonight with chances of showers Monday. No significant weather impacts expected.

2. Above normal temperatures likely Tuesday through the end of the week, with an active pattern keeping a chance for showers in the forecast most days.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

Low pressure tracks across the northern Great Lakes into southeast Canada tonight into Monday. The attendant warm front will bring increasing chances for rain late this evening with rain likely after midnight across much of the area. Steady rain associated with the warm front will diminish Monday morning, although this break in precipitation will be short lived as a surface trough and cold front cross early afternoon bringing renewed chances for showers. Upslope showers in the mountains may linger into Monday night while shower chances elsewhere will diminish Monday evening. Rainfall amounts will range from 0.1" to 0.3" south of the mountains. Northern areas stand the best chance for around 0.5 inches with higher amounts in the mountains. It will be mild and breezy Monday with southwest winds gusting around 25 mph and highs in the 60s. The cold front will struggle to make it south of the area Monday night leading to mild overnight lows ranging from the 40s north to 50s south.

KEY MESSAGE 2 DESCRIPTION... Zonal flow at 500 mb is going to keep the weather active, but also allow temperatures to climb above normal and remain there through the end of the week. A frontal boundary enters the area Tuesday and models are in reasonably good agreement that it stalls here. This allows for multiple waves of low pressure to cross the region keeping at least a chance of showers in the forecast each day as various shortwave troughs transverse the zonal flow aloft. The good news is that this general zonal flow will also feature a good amount of southerly flow which help to push 850 mb temperatures to +10-13C, and 925 mb temperatures to +15-18C, for much of next week. Forecast soundings suggest we should be mixing to somewhere in between leading to consistent high temperatures in the 60s and 70s each day. Seabreezes each afternoon will keep the immediate coast a hair cooler, but that is status quo for this time of year.

As far as the daily chances for rain showers, ensembles are not picking up on anything significant QPF wise, so don't interpret this as the makings of a miserable week. The best chance for wetting rains (greater than 0.10") this week on any given day looks to be in the mountains. The coastal plain sees less of a chance this time of year as seabreezes advect cooler stable air onshore. Tuesday will be a day to watch as mostly clear skies through the morning may develop enough instability to lead to some thunderstorms which would bring locally higher rainfall amounts. The best chance of this looks to be across New Hampshire and interior Western Maine. The seabreeze likely beats any storms to the coast. The next best chance after Tuesday evening for widespread precipitation may be Thursday night as a sharper trough passes overhead with low pressure centered in the vicinity, but we will keep a close eye on how things trend and evolve with this pattern as time goes on.

AVIATION /00Z MONDAY THROUGH FRIDAY/

Through Monday night...Clouds will continue to thicken and lower through the remainder of the evening with -RA developing 02Z to 06Z. CIGS and visibility likely remain high enough for VFR to prevail at KMHT, KCON, KLEB, and KPSM. Elsewhere, low CIGS and reduced visibility will bring periods of MVFR to locally IFR. CIGS will lift Monday morning for a return to VFR, although KRKD and KAUG may stay at least MVFR through the afternoon. A cold front will bring additional showers early Monday afternoon with some potential for restrictions to return. Lingering low level moisture may allow for patchy fog Monday night, otherwise VFR.

Outlook... Tuesday: Generally VFR through the day with MVFR possible at interior terminals for the evening. Isolated thunderstorms may also form during the evening and may move near interior terminals.

Wednesday: Generally VFR expected with some MVFR possible in afternoon/evening showers.

Thursday-Thursday night: VFR transitioning to MVFR possible as this looks like a day that could feature widespread precipitation.

Friday: Conditions improve back to VFR.

MARINE

Low pressure passing north of the waters will bring increasing southerly winds overnight shifting southwesterly Monday. Winds will gust around 30 kts with seas building 5-8 feet and SCAs remain in effect. Winds turn westerly Monday night and gradually diminish, while elevated seas continue SCA conditions into Tuesday morning.

Conditions on the waters next week are going to depend on the track of multiple low pressure systems moving through the area. If they take more interior tracks like is currently advertised than sub- SCA/marginal SCA conditions can be expected. However, if they shift southward towards the waters the chance of SCA conditions increases. Keep a close eye on the marine forecast if you are planning on venturing out this week.

GYX WATCHES/WARNINGS/ADVISORIES

ME...None. NH...None. MARINE...Small Craft Advisory until 8 AM EDT Tuesday for ANZ150-152-154. Small Craft Advisory until 8 PM EDT Monday for ANZ151-153.