textproduct: Gray - Portland

WHAT HAS CHANGED

Blended in the latest surface observations and tweaked the near term portion of the forecast. Also, added patchy fog into the forecast for tonight. Finally, let the small craft advisory expire for Casco and western Penobscot Bay.

There is a chance for a few strong to severe thunderstorms Tuesday afternoon and evening across southwest New Hampshire.

KEY MESSAGES

1. Warm with a chance for showers and thunderstorms Tuesday afternoon and evening. A few strong to severe thunderstorms are possible across southwest New Hampshire.

2. Above normal temperatures persist into the weekend, along with chances for showers most days.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

Low pressure passing north of Maine this afternoon will lift a warm front through the area this evening with the cold front then stalling near the Canadian Border tonight. There will be continued chances for showers this evening with areas south of the mountains turning mostly dry overnight.

A warmer air mass combined with partly to mostly sunny skies Tuesday morning will allow for temperatures to climb into the 60s across much of the area with 70s likely across interior western Maine and southern NH. Onshore winds will develop by afternoon keeping coastal areas cooler. Remnant convection from the Midwest will track along the stalled cold front Tuesday and much of the latest NWP guidance brings this activity across northern New England Tuesday afternoon and evening. However, there are timing and trajectory differences amongst CAM solutions which has implications for the potential of strong to severe thunderstorms. The 12Z HREF mean brings 500-1000 J/kg of MU CAPE into portions of southwest New Hampshire with around 40 kts of deep layer shear. The late outlook from SPC brings a Marginal Risk for severe storms into far SW New Hampshire with general thunder across much of the rest of the area. The primary threat from storms will be strong winds and will watch timing and instability trends to better gauge the potential threat. Chances for storms diminish Tuesday night with fog possible along the coastal plain.

KEY MESSAGE 2 DESCRIPTION...

A large ridge persists across the Eastern US through the week and into the weekend. Northern New England finds itself positioned on the northern periphery of the ridge, bringing an increased chance for showers and many warm-up thwarting variables through the week. Southwestern New Hampshire holds the best chance to see the warmest readings each day through the weekend, but uncertainty grows further north and east across the forecast area for the forecast period as to how warm temps will really reach.

Each day brings chances for showers as remnant convection from the day before across the Midwest rolls around the ridge and through the area. Clouds and showers from these hinder warmer temperatures chances toward the north. Additionally, seabreezes and southerly flow keep the Maine coast and central Maine on the relatively cooler side. Wednesday holds the best chance for southern New Hampshire to hit 80 degrees this week. 60s and 70s are most likely elsewhere. Then by Thursday a backdoor front likely brings a break in the warm up. The current NBM forecast has mainly 50s to low 60s across Maine, but there remains the chance conditions will end up gloomier than this. Western NH in the CT River Valley holds the best chance to hold onto the warmer temps through the week with 70s more likely.

Late week and into the weekend, the warm up likely gets knocked back from a combination of back door fronts and leftover ridge rolling convection before a transition to northwesterly flow behind a passing cold front by early next week.

AVIATION /00Z TUESDAY THROUGH SATURDAY/

Through Tuesday...Patchy FG may result in localized restrictions at times tonight but otherwise mainly VFR CIGS are expected through the period with light and variable winds. Showers and thunderstorms will be possible after 18Z with strong to severe storms possible at KLEB extending to KMHT, KCON, although confidence is low. Showers and storm chances diminish Tuesday night with fog possible along the coastal plain that could bring at least IFR.

Outlook...

Wednesday-Friday: MVFR likely to continue due to showers. Periods of VFR are more likely across Southern NH terminals.

Saturday: Mainly VFR expected.

Saturday Night- Sunday: MVFR more likely with showers.

MARINE

Strong southwest winds continue SCA conditions overnight with winds diminishing towards Tuesday morning. Winds and seas generally stay below SCA threshold Tuesday into Tuesday night. Generally fair conditions are expected mid to late week as a ridge persists across the Gulf of Maine. A backdoor cold front brings northeasterly flow on Thursday. Winds shift between southerly and northeasterly as the front lingers into the weekend.

GYX WATCHES/WARNINGS/ADVISORIES

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