textproduct: Gray - Portland

WHAT HAS CHANGED

No significant changes since the previous forecast cycle.

KEY MESSAGES

1. Rain and mountain snow will end this evening. Cool and mainly dry conditions expected on Monday, although a few rain and snow showers are possible Monday afternoon.

2. Near to below normal weather expected for much of the next week combined with generally below normal precipitation.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

Rain and northern/mountain snow will end between 6-9 pm this evening from west to east as low pressure and an associated cold front exit to our northeast. Skies will clear overnight with low temperatures falling into 20s to lower 30s from north to south.

Surface high pressure will begin to build southwest of New England on Monday as northwesterly winds allow for CAA throughout the day. This combined with some sfc heating will allow for weak instability to develop, which will likely result in scattered rain and snow showers during the afternoon. An isolated heavy snow shower or even a snow squall cannot be completely ruled out, especially from the foothills and points northward. High temperatures will range from the upper 30s across the north with middle to upper 40s south. Northwesterly wind gusts between 20-25 mph will make it feel cooler though.

KEY MESSAGE 2 DESCRIPTION...

Much of the long term forecast looks to feature mean trofing to our east and ridge axis aloft centered just to our west. The end result is a pattern where the threat of backdoor cold fronts or onshore flow is always possible. As a rule I will be pretty skeptical of any modeling of significant warmth in set ups like this, but the good(?) news is that the NBM is in agreement and temps during the day stay in the 40s and 50s thru next week. The pattern will also not be very supportive of broad ascent across the region and so any precip will be more mesoscale and localized in nature. Because of the blocky nature of the pattern, any storm system lifting towards New England will also tend to get shunted along to the south. As such, any precip shield that can manage to brush the area will have some cooler and drier air to contend with. On Wed for example some precip may cross the southern half of the forecast area. If timing remains overnight into Wed morning, it will be cold enough to support snow. Based on forecast soundings, the snow growth zone will have some dry air to fight, and so I would not expect heavy enough rates for accumulation but enough to see some flakes.

AVIATION /18Z SUNDAY THROUGH FRIDAY/

MVFR-IFR restrictions will persist through 00Z Monday due to low ceilings and RA. Conditions will then improve back to VFR overnight as NW winds persist at 10-15 kts. Mainly VFR conditions are then expected on Monday and Monday night, although scattered RA and SN showers may result in brief localized vis restrictions. NW wind gusts up to 25 kts will be possible during the daytime. No LLWS is anticipated through the period.

Outlook:

Tuesday: VFR conditions expected.

Tuesday Night: Becoming MVFR or IFR CIGs. Low confidence in VIS forecast, but some light snow is possible for portions of the forecast area, especially away from the coast.

Wednesday: Becoming VFR conditions.

Thursday: VFR conditions expected.

Thursday Night: VFR conditions expected.

Friday: VFR conditions expected.

Friday Night: VFR conditions expected.

MARINE

SCA NW wind gusts are expected through the first half of tonight across the near shore waters with gusts up to 20 kts across the bays. Otherwise, winds and seas will be below SCA criteria Monday into Monday night.

Onshore winds Tue into Wed gradually turn southwest and then west thru the remainder of the week. At this time it does not appear that widespread SCA conditions are likely, with winds remaining breezy at best and seas in the 2 to 4 ft range from the coast to outer waters. Will have to keep an eye on marine fog/stratus formation Tue night into Wed with the warm front draped nearby.

GYX WATCHES/WARNINGS/ADVISORIES

ME...None. NH...None. MARINE...Small Craft Advisory until midnight EDT tonight for ANZ150-152- 154.