textproduct: Gray - Portland

WHAT HAS CHANGED

No major changes were needed for this update. Just blended in the latest observations to the going forecast. Patchy fog may continue for another hour or two in the valleys and over portions of the Midcoast.

KEY MESSAGES

1. Pleasant weather continues through Sunday under high pressure.

2. Quiet weather comes to an end with unsettled weather returning for the first half of next week with the potential for areas of heavy rain.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

Despite weak upper troughing from time to time over the weekend, we should remain dry with some diurnal CU. There will likely be some valley fog early this morning, especially in the CT River Valley. It is also not out of the question to have some on the Midcoast as well as mostly moistening southerly flow continues.

Near-seasonable temperatures are in store for both today and Sunday with onshore flow cooling the coast down each afternoon. Valley fog is once again possible tonight and Sunday night, and possibly at the coast as well.

KEY MESSAGE 2 DESCRIPTION...

Early next week, an omega block pattern establishes across the region as the western ridge amplifies and Atlantic high builds northward, parking a longwave upper level trough over the East Coast through at least Thursday. An upper-level low over Hudson Bay will deepen the trough, driving a 995 mb surface low across New England. This is actually a rather deep low for July. Model guidance shows notable spread regarding the surface low track. The GFS/GEFS favors a weaker, more progressive solution further south, whereas the ECMWF/EPS depicts a stronger (wetter), closed low further north. A significant trend since yesterday's guidance has been for the surface low to slow down/occlude over New England Wed night- Thursday. As such, the end of next week is trending wetter.

In terms of local impacts, generally expecting a wet few days from Tuesday-Thursday, but possibly lingering into Friday depending on how quickly the surface low exits offshore. The stage will be set for locally heavy downpours as PWATs surge to 1.5-2.0", with dew points well into the 60s. We will see lowering heights and temperatures aloft with a bit of a cold pool aloft. This will support modest instability of up to 1000 J/Kg MUCAPE. Thus, there is potential for thunderstorms each day, but especially focused during the afternoon/early evening timeframe when surface instability is maximized. It will be showery in nature and come in a few waves, rather than be raining the entire time, thankfully. With that said, large portions of the forecast area have been abundantly dry this month, so some soaking rain will be beneficial assuming it is not locally excessive.

Despite the increasing humidity, should have seasonable if not slightly cool temperatures, given the increased cloud cover and lowering 500 mb heights/thickness values by midweek.

AVIATION /12Z SATURDAY THROUGH WEDNESDAY/

Through 12Z Monday: VFR conditions expected. The exception is at KLEB and KHIE where valley FG is once again possible (this morning and Sunday morning). KRKD may see it as well, with an outside chance KPWM sees it for an hour or two late Sunday night. Light southerly flow will prevail today. No LLWS is anticipated through the period.

Outlook:

Monday/Monday Night: Mainly VFR conditions expected. Isolated SHRA may cause brief localized restrictions.

Tuesday-Wednesday: MVFR or worse restrictions likely due to RA and possible TSRA.

MARINE

Winds and seas will remain below SCA criteria through Sunday night as surface high pressure remains over or east of the Gulf of Maine.

Outlook: The gradient will remain relaxed with winds and seas safely below SCA through the first half of the forecast. A low pressure system is projected to develop south of the area along the east coast, supporting multiple rounds of widespread rain and the occasional thunderstorm mainly Tue-Wed. Looking at increasing winds and seas with potential for SCA conditions. Quieter weather follows for the later half of the week.

GYX WATCHES/WARNINGS/ADVISORIES

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