textproduct: Gray - Portland

WHAT HAS CHANGED

A Freeze Warning has been issued tonight for portions of western New Hampshire and a Frost Advisory issued for southwest New Hampshire through the western Maine foothills.

KEY MESSAGES

1. Frost and Freeze headlines have been issued tonight for portions of New Hampshire and western Maine.

2. Low pressure dominates New England in the 2nd half of this week, bring multiple days of potentially widespread showers through Friday.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

Scattered showers across the north will lose daytime fuel into the early evening hours. Following suite, much of today's cu field should dwindle. This will leave mostly clear skies for much of the interior tonight.

The clear skies should help daytime temps in the 50s to lower 60s quickly cool. Barring a persistent sfc breeze, temperatures should radiate well across the foothills and interior leading to overnight lows in the low to mid 30s. This results in Grafton and Sullivan Co in NH falling towards Freeze criteria and points from SW NH through the ME/NH Lakes region falling into Frost criteria tonight. Can't rule out some patchy frost at typically cooler points towards the ME Midcoast, but some lingering cirrus and NW breeze may limit temp flux through the late evening hours.

Tuesday will be similar to today, but with no shower chances and a little more breeze. Will be focusing on the potential for another cool night with potential frost headlines, but clouds ahead of our next weathermaker Wednesday may play spoil. With high pres briefly moving overhead, don't expect surface winds to get in the way of radiational cooling. For now, rapid cooling would be most likely in the evening after sunset but before midnight. High clouds begin to advance from the SW, so west/central ME may see the coolest temperatures for the night.

KEY MESSAGE 2 DESCRIPTION...

Little change to the going forecast at this time for mid to late week as unsettled weather is expected for most of Wed through Fri.

On Wednesday and upper low and slow-moing attendant SFC low pressure system approaches from the eastern Great Lakes states. Latest guidance including deterministics and ensembles show reasonable run to run consistency with periods of wet weather, with the potential for the heaviest precipitation to be Wednesday night and Thursday daytime. The average solution has conditions deteriorating Wednesday afternoon in light rain and potential coastal stratus. The low pressure system basically stalls nearby on Friday allowing for periods of showers and drizzle and perhaps some fog along with colder than normal temperatures. Will likely lower going temperatures a couple of degrees for the daytime hours late in the week.

The weekend looks to be drier for the moment but we'll continue to monitor as there is still some disagreement within the various guidance solutions with short wave trough placement and speed.

AVIATION /15Z MONDAY THROUGH FRIDAY/

Through 18Z Tuesday...VFR expected through tonight with winds and showers in the mountains decreasing towards sunset. Think overnight breeze should prevent valley fog development, esp due to drier surface conditions. NW winds increase again Tues AM, 15 to 20 kts. This should keep sea breeze off the coastal terminals.

Outlook:

Tuesday night: VFR expected with increasing upper cloud deck.

Wednesday: AM VFR, MVFR in the afternoon due to rain.

Thursday and Friday: MVFR due to showers and possible isold thunder. Areas of IFR possible as well, especially in periods of heavier rain.

Saturday: Improvement to VFR.

MARINE

SCA continues through late afternoon due to passing offshore disturbance. This keeps 4 to 6 ft waves towards the northern coastal waters. High pressure then advances towards the coastal waters for Tuesday.

Little change to the extended portion of the forecast. Southeast winds increase on Wednesday afternoon and may rise to SCA levels later Wed afternoon through Thurs. Winds diminish and flip to light northerlies by Friday morning, with seas continuing to remain at 3-5 ft.

GYX WATCHES/WARNINGS/ADVISORIES

ME...Frost Advisory from 2 AM to 9 AM EDT Tuesday for MEZ012-013- 018>020-033. NH...Frost Advisory from 2 AM to 9 AM EDT Tuesday for NHZ004-006- 008>011-015. Freeze Warning from 2 AM to 9 AM EDT Tuesday for NHZ003-005- 007. MARINE...Small Craft Advisory until 6 PM EDT this evening for ANZ150- 152.