textproduct: Gray - Portland

WHAT HAS CHANGED

No major changes were needed for this forecast package.

KEY MESSAGES

1. A slow moving upper trof will bring unsettled weather until Wednesday when high pressure briefly settles into the region.

2. A cold front gradually moves through on Thursday and Friday, followed by high pressure for the weekend.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

A closed upper low over Quebec will continue to drift northeast and open up through the day. Despite the weakening system, cooler temps aloft will lead to unstable conditions by peak heating. Convection will be scattered, similar to yesterday. Forecast soundings do show quite a bit of dry air, so any shower or storm may have some gusty winds. However they do show some warmer mid to upper level air than yesterday, so the small hail potential is likely a little bit lower.

Then surface ridging tries to poke into the region for Tue night. This should allow for cooler temps in radiational cooling, especially in the northern valleys. Currently NBM guidance has some upper 40s, which closely matches MOS guidance. So at this time I see no reason for changes. There will also likely be more valley fog, which I have added. Fair weather is expected Wed as return flow begins to set up ahead of the next trof.

KEY MESSAGE 2 DESCRIPTION... A weakening cold front approaches New England during the day on Thursday as low pressure tracks through Canada. A weak warm front approaches on Thursday as well, bringing a slight increase in moisture ahead of the cold front.

The front looks to be decaying as it approaches, so shower and storm activity associated with the front will likely be scattered and more focused across western areas Thursday afternoon. Shower chances continue through the overnight, and then a stronger front likely pushes through on Friday and ushers in a drier airmass. With the front on Friday, scattered and showers and storms will be possible again during the daytime, with the best chance across the higher terrain.

Temperatures look to be pretty similar behind the front as ahead of it, with widespread 70s to near 80s degrees from Thursday through the weekend. There will be a noticble difference in the humidity over the weekend however, with dew points dropping back into the 50s to upper 40s behind the front. High pressure for the weekend brings seasonably cool nights, and abundant sunshine for the daytime.

By early next week the high moves off the East Coast, bringing a warmer and more moist return flow. Chances for showers and storms increase again early next week with the next cold front possibly approaching New England by Tuesday.

AVIATION /09Z TUESDAY THROUGH SATURDAY/

Fog is currently causing low CIGs and reduced visibilities in most river valleys, and across the Midcoast. Patchy fog is still present elsewhere, and lower restrictions associated with fog will continue through around 14Z / 10AM. Fog should mix out by then, and VFR is expected through the remainder of the day across most places. A stray thunderstorm may cause restrictions to lower in locations north of the mountains this afternoon.

Outlook:

Tuesday Night - Wednesday Night: VFR conditions expected. Local IFR or lower at night in valley fog.

Thursday: Generally VFR conditions expected

Thursday night-Friday: Generally MVFR conditions expected with widespread showers. IFR conditions possible in fog at night.

Friday Night-Monday: Mainly VFR conditions during the daytime, with nighttime valley fog likely each night at HIE, LEB, and possibly CON.

MARINE

Winds and seas are expected to remain below SCA thresholds thru midweek. Until the upper trof can cross the Gulf of Maine, there will be areas of marine fog/stratus that form especially at night. A period of near SCA conditions are possible in southerly flow ahead of a cold front on Thursday into Thursday night. High pressure then builds across the waters for the weekend, bringing an extended period of fair conditions into early next week.

GYX WATCHES/WARNINGS/ADVISORIES

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