textproduct: Gray - Portland

WHAT HAS CHANGED

Minor update to the Aviation section for the 00Z TAFs.

KEY MESSAGES

1. Heat persists areawide through Friday, with southern locations lingering into Saturday. Daytime highs will peak in the 80s to around 90 degrees, but humidity will be low, limiting excessive heat impacts.

2. A slow moving front brings rounds of showers and storms into the region through the weekend.

3. After a brief cool down early next week, temperatures rebound again by midweek.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

Forecast remains on track for persistent warmth areawide through Friday. Highs are forecast to run 10 to 15 degrees above normal, topping out in the mid to upper 80s, to around 90 in a few interior ME locations and southern NH. Higher dewpoint temps won't accompany this airmass, with resulting humidity not as heavy as later summer heat episodes.

Low level winds look to remain light, and will likely see some impact from a cooler, more humid, seabreeze during the afternoons today and Friday. This looks to encompass much of the Midcoast, with less intrusion from Portland south.

Overnight lows, amid mostly clear skies and calm winds, should be allowed to radiate well. But into June here, we are seeing more daylight, and the overall window for overnight cooling shortens. Lows in the 50s should bring ample recovery between the otherwise above normal highs.

As moisture advects through the northern portion of the surface high, could see isolated to scattered showers develop towards central Maine Friday afternoon. Warm air aloft should cap how deep convection gets, thus think lightning may be largely absent. Dependent on daytime instability, expect these to weaken and shift east by early Fri evening.

KEY MESSAGE 2 DESCRIPTION...

Another very warm day is expected on Saturday across southern areas as temperatures push into the upper 80s to low 90s. However, a cold front will push southward through the daytime on Saturday, bringing showers and some thunderstorms into northern areas by the late morning hours. This keeps highs in the 70s across the north, with low to mid 80s generally expected in between. Central Maine and the MidCoast will likely also hold in the 70s as onshore flow and cloud cover increases.

The showers and storms make gradual progress southward through the daytime, but also become more scattered the further south they extend. So for southern and coastal areas, most of the day looks dry and warm, followed by an increased chance for showers and storms in the afternoon hours.

The front continues to only slowly progress through northern New England Saturday night and Sunday, with a wave of low pressure likely to form along the front as the trough deepens across the area. This cooling aloft brings a better chance for more widespread rounds of showers and some thunderstorms to interior and coastal areas on Sunday. Meanwhile, northern areas stand the best chance to dry out for the second half of the day as the front sags southward, though isolated pop up showers would still be possible. A sharp temperature divide is likely across the forecast area by Sunday afternoon, with highs in the mid 60s behind the front across the north, while southern New Hampshire warms into the mid 80s.

Showers and storms then quickly dissipate after sunset on Sunday as the front moves off to the south.

KEY MESSAGE 3 DESCRIPTION...

High pressure builds into the area on Monday, bringing with it a seasonably cool and dry airmass. High temperatures look to top out at a comfortable low to mid 70s with low humidity and mainly sunny skies. Some high clouds likely bring some filtered sunshine through the day as the western periphery of the trough slowly moves away from New England.

High pressure gradually drifts southward while a ridge pumps into the Northeast US and Eastern Canada. This brings with it a moderating trend into midweek, with widespread highs in the mid 80s by Wednesday. The greatest height anomalies associated with the ridge look to be positioned to the northwest of New England through Quebec and Ontario. This brings the warmest anomalies into northern areas for at least a couple days next week. It also presents the opportunity for a backdoor cold front by late week.

All this really means is that temperatures look relatively warm and uniform for midweek next week, with widespread mid 80s across most of the area, and the most above normal temps across northern and western areas.

AVIATION /00Z FRIDAY THROUGH TUESDAY/

Through 00z Saturday...VFR with no sig wx. Coastal terminals will see onshore afternoon seabreeze Friday, with inland terminals mainly SW...becoming light and variable at night. A few SHRA possible towards central ME Friday afternoon, dissipating in the evening.

Outlook:

Friday Night: VFR. No sig wx.

Saturday: Showers and storms spread from northwest to the coast from mid morning through the late afternoon, bringing restrictions at times.

Saturday night - Sunday: Showers and a few thunderstorms with MVFR to IFR.

Sunday night - Wednesday: Mainly VFR prevails, but some nighttime valley fog will be possible at HIE and LEB each night.

MARINE

High pressure towards the Ohio Valley maintains influence over the waters through Friday leading to gusts 10 to 15 kts and wave heights 1 to 3 ft.

Some marginal SCA conditions are possible ahead of a cold front in southerly flow late Saturday through Sunday, and then again in northerly flow behind the front Sunday night into Monday. Broad high pressure builds across the waters on Monday, and settles in through midweek.

GYX WATCHES/WARNINGS/ADVISORIES

ME...Beach Hazards Statement from Friday morning through Friday evening for MEZ023>028. NH...Beach Hazards Statement from Friday morning through Friday evening for NHZ014. MARINE...None.