textproduct: Gray - Portland

WHAT HAS CHANGED

Minor update to refresh Aviation section for the 12Z TAFs.

KEY MESSAGES

1. Dry weather continues through Tuesday with temperatures around seasonal averages.

2. Wet weather makes a return for the second half of the week.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

High pressure will generally dominate the weather pattern through today with dry conditions and temperatures around normal for this time of year (maybe a touch above normal for a few locations inland).

By this afternoon, we will warm into the 60s across most of the forecast area but a few upper 50s will be possible over the higher terrain and a few lower 70s will also be possible across southern New Hampshire.

Tuesday will be similar but a touch cooler, drier, and a little bit breezier as high pressure slides off to the east and the pressure gradient modestly tightens. There will be minimum relative humidity values in the 25 to 35 percent range across most of the forecast area Tuesday afternoon with the exception of coastal areas. Southeast winds in the 8 to 15 mph range are in the forecast with some gusts in the 20 to 25 mph range. Thus, we could see some elevated fire weather concerns Tuesday afternoon and it will be period to watch.

KEY MESSAGE 2 DESCRIPTION...

The mid-level ridge will begin to break down on Wednesday as a trough axis continues to slide eastward over the Great Lakes region. A lobe of remnant moisture from an offshore storm will pinwheel towards the coast and interact with the approaching trough from the west. Could see some ocean-enhanced scattered showers on Wednesday with easterly flow and the moisture plume overhead. Precipitation looks scattered with the highest chances along the Maine coast.

A widespread soaking rainfall then arrives on Thursday as an area of low pressure tracks over the Gulf of Maine. Latest NBM and ensemble based guidance is in generally good agreement that this system should bring between 1-2" of rainfall to the region, with locally higher amounts possible. Given the ongoing drought conditions and low river/stream flows, flooding is not anticipated to be a concern. This system is then progged to become vertically stacked and cutoff from the main steering flow through potentially the upcoming weekend. This will result in a prolonged stretch of cloudy and damp conditions with showers at times. Mountain snow will be possible given the cool temperatures aloft. High temperatures will generally be below average during this stretch.

AVIATION /12Z MONDAY THROUGH FRIDAY/

VFR prevails today with light southeast winds. VFR continues tonight through Tuesday with calm winds tonight and ESE winds increasing Tuesday with gusts around 15 kts during the afternoon.

Outlook:

Wednesday/Wednesday Night: Lowering ceilings with restrictions possible by 18Z, especially at coastal terminals. Scattered SHRA are also possible. E winds at 5-15 kts.

Thursday/Thursday Night: Restrictions likely due to low ceilings and RA. E-NE winds of 15-25 kts.

Friday: Restrictions continue but with some possible improvement.

MARINE

Sub-sca conditions are expected through Tuesday as high pressure builds over the waters.

Seas outside of the bays will remain elevated at 3-6 ft Wednesday through at least Friday, likely necessitating a prolonged SCA. In addition, a period of E-SE wind gusts up to around 30 kts is possible Thursday, followed by W wind gusts on Friday, especially across the near shore waters and Penobscot Bay.

GYX WATCHES/WARNINGS/ADVISORIES

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