textproduct: Gray - Portland

WHAT HAS CHANGED

River flood warning for the Saco River has been cancelled. A frost advisory has been issued for northern and some interior locations for tonight.

KEY MESSAGES

1. A cool airmass brings the chance for frost across the north and parts of the interior tonight.

2. A shortwave brings scattered showers and thunderstorms for the afternoon hours on on Sunday.

3. Unsettled weather Monday followed by an increasingly dry pattern with warmer temperatures as the week progresses.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

Clear skies return tonight as today's storm system departs. Winds also ease this evening, allowing for a period of radiational cooling tonight. Given the cool start, temperatures are expected to fall to near freezing across the north before the next batch of clouds arrives ahead of the next system late tonight. For this reason, a frost advisory has been issued. Downwind of the mountains and along the coastal plain, a light west breeze likely keeps temps from reaching their full cooling potential. The exception will be downwind of the Whites around Fryeburg, where winds likely stay calm long enough to allow for areas of frost as well. Some patchy frost can't be ruled out in the typical cool spots outside the advisory, but most other spots likely see lows in the upper 30s.

KEY MESSAGE 2 DESCRIPTION...

Another shortwave dives southward into New England on Sunday, but it won't be nearly as potent as today's system. Clouds blossom southward through the morning, with afternoon showers and thunderstorms developing across the area. With falling temperatures aloft, some small hail is likely to accompany some of the heavier showers and storms. After reaching into the mid to upper 60s by early afternoon, temps fall back in the afternoon with the passage of any showers and storms. Some scattered showers remain possible through the overnight Sunday night as the low moves through, but won't be as robust or widespread as during the daytime.

KEY MESSAGE 3 DESCRIPTION...

Another short wave trough swings southward through the region on Monday along with its associated cold temperatures aloft. This will allow for occasional showery periods with a few thunderstorms possible in the afternoon where some low CAPE values can develop, especially inland. Given clouds and showery periods, temperatures will only rise into the lower to mid 60s.

The upper level troughing gradually gets replaced by short wave ridging on Tuesday which will aid in less showery weather. While we are going with low chance PoPs for most of the forecast area, not everyone will see rain. Highs will warm up some, up to about 70 degrees at many locations.

Overhead ridging with further strengthen on Wednesday and Thursday with dry weather expected with highs in the 70s on Wednesday and around 80 on Thursday.

Chances for showers increase some late Friday as a cold front may begin to sag southward out of Canada. However, mainly dry weather is expected with summer-like highs well into the 80s.

AVIATION /18Z SATURDAY THROUGH THURSDAY/

Through 12z Monday...

Conditions continue to improve back to VFR through the late afternoon and early evening hours. VFR then prevails through the overnight and Sunday morning hours. Periods of MVFR to brief IFR are then possible through the afternoon and evening hours as scattered shower and storms are possible at all terminals. Scattered showers remain possible, but are less likely, through the overnight hours Sunday night.

Outlook:

Monday: Scattered showers may bring localized restrictions for brief periods of time. Winds are expected to be easterly at 5 to 10 knots turning light south during the afternoon.

Tuesday: VFR with widely sct showers possible. Light north winds becoming southerly on the coastal plain during the afternoon.

Wednesday: VFR with light southerly winds.

Thursday - Friday: High pressure is favored with VFR conditions.

MARINE

Any lingering storm and gale fore winds ease this evening across the outer waters. SCA conditions continue along the coastal waters and into Casco Bay as seas remain above 5ft most of the night. Seas gradually fall below 5ft from north to south from late tonight through tomorrow afternoon. High pressure passes through the Gulf of Maine on Sunday, then a weak low pressure system crosses through Sunday night.

Unsettled pattern persists into Monday while winds and seas generally stay below SCA thresholds. Fair weather Tue-Fri with winds and seas remaining below SCA thresholds.

GYX WATCHES/WARNINGS/ADVISORIES

ME...Frost Advisory from 10 PM this evening to 7 AM EDT Sunday for MEZ007>009-012-033. High Surf Advisory until 8 PM EDT this evening for MEZ023-024. NH...Frost Advisory from 10 PM this evening to 7 AM EDT Sunday for NHZ001>004. High Surf Advisory until 8 PM EDT this evening for NHZ014. MARINE...Small Craft Advisory until 5 AM EDT Sunday for ANZ150-152-153. Small Craft Advisory until 2 PM EDT Sunday for ANZ154. Gale Warning until 8 PM EDT this evening for ANZ180-182-184.