textproduct: Gray - Portland

WHAT HAS CHANGED

Beneficial rainfall amounts have increased slightly, mainly over NH where localized amounts to around 1 inch are possible tonight through Sunday.

KEY MESSAGES

1. Low pressure crossing southern New England brings periods of rain late tonight through Sunday morning followed by another round of showers Sunday night as a cold front crosses.

2. High pressure will build across New England for the first half of this week, bringing mainly dry conditions and cool temperatures. A frontal boundary may bring increased shower chances late in the week.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

No significant changes to the forecast thinking with a pair of systems crossing the area tonight through Sunday night as broad trough deepens over the Northeast. The first system will be a compact area of low pressure forming near southern New England tomorrow morning and exiting east of Cape Cod during the afternoon. Models continue to show a rapid increase of deep moisture tonight into Sunday morning as PWATs climb to 1.5 to 2 inches. CAMs and global models have now started to show broad forcing for ascent leading to an axis of rain extending north of the developing low across much of NH late tonight into Sunday morning which has resulted in a slight increase of QPF there. This axis of rain will then become focused across southern NH into the coastal plain of Maine late morning into the afternoon as areas to the NW see a break in precipitation. Rain then moves offshore by evening.

A cold front will slide east across Upstate NY Sunday evening with showers and storms forming along the front. These showers and storms will approach CT Valley after sunset while there is potential for lingering MU CAPE to keep chances for thunder in the forecast. Instability wanes overnight with mainly a broken line of showers crossing the area with the cold front. Total QPF will range from 0.25 inches north of the Maine mountains and increase to the south and west with an areal average of 0.75 inches across SW NH. Locally high amounts around 1 inch will be possible if some convective processes can be realized with the initial axis of rain late tonight through Sunday morning, mainly across central and southern NH. Rain chances diminish NW to SE as the cold front moves offshore Monday morning.

KEY MESSAGE 2 DESCRIPTION...

Surface high pressure will arrive from the west on Monday into Monday night behind a cold front. This will allow for clearing skies during the morning with high temperatures into the 60s to lower 70s from north to south. It will be a gusty day with NW wind gusts up to around 30-35 mph possible. The combination of mainly clear skies and light winds will likely allow for good radiational cooling conditions with forecast lows in the 30s across inland valleys with 40s elsewhere. Patchy frost is possible across valley locations.

High pressure will remain over the forecast area through Tuesday night before shifting offshore by Wednesday. Dry conditions will persist with highs on Tuesday into the lower 70s before warming into the middle to upper 70s on Wednesday. Some increase in cloud cover will keep lows warmer with readings into the 40s and 50s.

Shower chances then increase Thursday into Thursday night as a frontal boundary and associated weak wave of low pressure drops south out of Canada. Drier conditions are then possible as we approach next weekend.

AVIATION /18Z SATURDAY THROUGH THURSDAY/

Through Sunday night...Mainly VFR through 06-09Z Sunday morning with cigs quickly lowering to MVFR and localized IFR through 12Z. Periods of IFR in low cigs and rain is then likely through Sunday morning. Some improvement is possible from NW to SE Sunday evening while restrictions likely linger into Sunday night before a cold front crosses early Monday morning for improving conditions behind the front.

Outlook:

Monday/Monday Night: Any lingering restrictions early in the morning will quickly lift with VFR conditions expected. Daytime NW wind gusts up to 25 kts are possible. Valley FG is possible Monday night at LEB and HIE.

Tuesday/Tuesday Night: VFR conditions expected.

Wednesday/Wednesday Night: VFR conditions expected.

Thursday/Thursday Night: Restrictions possible in developing SHRA.

MARINE

Low pressure develops near southern New England Sunday morning and exits east of Cape Cod Sunday afternoon bring periods of rain and fog. Winds and seas will remain below SCA thresholds as this system passes with south winds briefly turning easterly. A cold front then crosses Sunday night shifting winds offshore by Monday morning with winds and seas remaining below SCA thresholds.

Outlook:

High pressure will keep winds and seas below SCA criteria Monday through at least mid to late week.

GYX WATCHES/WARNINGS/ADVISORIES

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