textproduct: Gray - Portland

WHAT HAS CHANGED

No significant changes since the previous forecast cycle.

KEY MESSAGES

1. Dry weather continues through Tuesday with temperatures near to above average.

2. Wet weather makes a return for the second half of the week with a widespread soaking rain Wednesday night into Thursday night, but flooding is not expected.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

Other than some fair weather cumulus clouds, it will continue to be a mostly sunny and dry afternoon and early evening with warm temperatures and light winds. Tonight will feature mainly clear skies, which combined with light winds and low dew points will allow for radiational cooling. Overnight lows will be mostly into the 30s areawide.

Surface high pressure will remain over the region on Tuesday, allowing for continued dry conditions along with mostly sunny skies. Afternoon mixing into a very dry airmass above will allow afternoon RH to fall into the 20s to lower 30s percent range inland from the coast. Along the coast, RH will be higher due to onshore southeasterly flow. Wind gusts between 20-25 mph are also expected, which will result in elevated fire weather conditions. High temperatures will range from the lower to middle 60s inland with the 50s to near 60 along the coast.

Tuesday night will remain dry with lows into the middle to upper 30s.

KEY MESSAGE 2 DESCRIPTION... Wednesday will be more of a transition day as high pressure breaks down and we begin to exit out of our dry stretch. Onshore flow will bring higher moisture into the region as low pressure approaches from the west. This will be more noticeable over parts of western Maine, especially the Midcoast, where this will likely result in at least mostly cloudy skies and cooler temps in the 40s or low 50s...but possibly drizzle or light rain showers as well. Warmer temperatures and less clouds are expected with westward extent, so much of NH still should still see highs in the 60s.

A widespread soaking rainfall is still on tap from Wednesday night through at least the day Thursday as a slow-moving upper- level low moves across the Great Lakes, and multiple shortwaves out ahead of it provide ongoing lift across New England. Ensemble means continue to show rainfall totals in the mostly 1-2" mostly across the board, although some wetter ensemble members still suggest localized amounts closer to 3" are possible. Even with these amounts, we aren't expecting any hydro issues given the ongoing dry conditions and longer duration of the rainfall, but rain could still be heavy at times with forecast sounding suggesting some elevated CAPE, which may also produce a few rumbles of thunder. There could also be a period of breezy onshore winds along the coast as secondary low moves into the Gulf of Maine late Thursday and Thursday night. Although end timing of the widespread steadier rain is still in question, we should see a southwest to northeast downward trend either overnight Thursday or the first part of Friday as start getting some drier air move in. That said, this may be followed by a period of drizzle and then a chance of additional showers through the day Friday as the upper low will still be approaching from the west. Saturday looks drier overall, but the influence of the upper low will bring a low (20-30%) chance of showers during the day.

There's another chance for widespread precipitation around Sunday but is much more uncertain. Those ensembles members suggesting the more widespread precip (mainly in the GFS camp) depict another low moving across the Gulf of Maine while most of the ECMWF members are drier and farther offshore. At the least, there will still be a chance of showers on Sunday with the upper low still expected to be over the northeast US and southeast Canada.

AVIATION /00Z TUESDAY THROUGH SATURDAY/

VFR conditions will persist through 12Z Wednesday, outside of perhaps some overnight valley FG. Light and variable winds will become SE on Tuesday with gusts up to 20 kts possible. No LLWS is anticipated.

Outlook...

Wednesday: IFR to MVFR ceilings possible, primarily for the western ME terminals. There will also be a chance for rain showers or drizzle.

Wednesday night-Thursday night: IFR to LIFR likely with widespread rainfall.

Friday-Friday night: Improving conditions to MVFR or VFR possible with precipitation expected to become more showery in nature.

Saturday: Mainly VFR, but scattered showers may still produce brief restrictions.

MARINE

Winds and seas will remain below SCA criteria through Tuesday night with onshore flow.

A long period of SCA conditions is likely from Wednesday into at least Saturday, mainly due to seas. However, wind gusts may exceed 25 kt from Wednesday night into Friday as low pressure crosses the Gulf of Maine. Another low may bring another period of increased winds from Saturday night into next Monday, but the strength and track of the low is uncertain.

GYX WATCHES/WARNINGS/ADVISORIES

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