textproduct: Gray - Portland

WHAT HAS CHANGED

Very little change to the going forecast early this morning. The fog should lift by around 9 am.

KEY MESSAGES

1. A cold front gradually moves through during the day today as an upper level low remains in the Great Lakes region.

2. The next chance of widespread rain comes late in the week, bookended by periods of dry weather through midweek and over the weekend.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

A cold front extending from a cut off low in the Great Lakes moves through during the daytime today. This brings the chance for a strong thunderstorm across the north near the Canadian border this afternoon before the front pushes off to the northeast. Elsewhere, scattered showers and a thunderstorm are possible, but overall a drying trend is expected through the day behind the front. Highs generally warm into the 70s to near 80s with sunshine returning.

Despite the front passing, the chance for scattered showers and storms lingers as the cut off low in the Great Lakes takes a few more days to slowly progress eastward through southern Canada. So while the overall trend is drier, showers remain possible through Tuesday.

Cooler temperatures return tonight with the drier airmass in place. Lows range from the mid 50s along the coast, to the upper 40s through the northern valleys. A stray shower can't ruled out during the overnight hours still. Seasonable temps return on Tuesday again, with highs mainly in the 70s to near 80 degrees.

Early morning fog, locally dense, is likely.

KEY MESSAGE 2 DESCRIPTION...

Upper-level low finally fully ejects out of the region by Wednesday. Brief ridging Wed-early Thu should bring tranquil conditions with comfortable dew points persisting and seasonable temperatures. As we head deeper into Thursday, southerly flow returns out ahead of the next trough, which will advect a more humid airmass back into the region.

A surface low closes off over Hudson Bay, sending a cold front through our region Friday night. Guidance indicates precipitation chances Thursday afternoon/evening primarily in interior zones away from the coast. There will be another chance on Friday with the actual front that looks more widespread as of now.

Nothing noteworthy for rainfall at the moment, but long range models do already have a 30 to 50% chance for rainfall exceeding a half inch. At first glance QPF is scattered, indicating a more convective precip distribution is possible. Should see good moisture return with dew points reaching the upper 60s, which will provide the necessary juice for locally heavy downpours.

First stab at next weekend suggests it could be a pleasant one with drying westerly flow behind the cold front, ushering in comfortable dew points in the 40s/50s. It will be a wait and see to know for sure though, as some guidance suggests the cold front may get hung up near the Southern New England coast.

AVIATION /12Z MONDAY THROUGH FRIDAY/

Marine fog and low stratus keeps IFR to LIFR conditions at most sites until a cold front passes through. A return to VFR behind the front is expected from western sites in the early morning, to late morning for eastern sites. A scattered shower or storm is possible at all terminals this afternoon, with VFR prevailing otherwise. Valley fog will then be possible tonight at LEB and HIE, with VFR then returning by mid morning Tuesday and prevailing.

Outlook:

Tuesday-Thursday: Generally VFR conditions expected

Thursday night-Friday: Generally MVFR conditions expected with widespread showers. IFR conditions possible in fog at night.

MARINE

Conditions remain below SCA levels for at least the next few days, with a cold front passing through the waters this afternoon. Reduced visibility in marine fog is likely through midday today before the frontal passage. Broad high pressure then builds in for midweek. A stronger cold front is likely late in the week, with SCA conditions possible.

GYX WATCHES/WARNINGS/ADVISORIES

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