textproduct: Gray - Portland

WHAT HAS CHANGED

Have allowed the Small Craft Advisory to expire and issued a new Small Craft Advisory starting late tonight through Wednesday night.

KEY MESSAGES

1. Low pressure brings widespread precipitation chances for mainly the northern zones the middle of this week. Rain is expected well south of the mountains, but cold low level air in the mountains and portions of the foothills will portend to sleet and freezing rain.

2. Relatively cooler conditions return for late week and into the weekend, with an unsettled pattern continuing.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

Another warm day in store for the forecast area today, which should be the warmest day of the week. Temperatures have been raised a couple of degrees from the previous forecast.

Things begin to change with the approach of a short wave trough and the arrival of a cold front that will sag southward out of Quebec. This setup will bring much colder temperatures to the area, especially in the north on Wednesday. At the same time strong overrunning will develop by Wednesday afternoon allowing widespread precipitation to break out. While the surface warm front will sag south of the forecast area, mid level forcing will drive the precipitation, and this will be over the mountains and foothills. It's possible that some southern locations such as southern NH receives very little rainfall from this system. There are also some significant difference amongst the various sources of guidance with respect to heaviest precip placement, with some solutions lifting it north of the international border leaving the forecast area with very little in the way of heavier precip.

With cold low level temperatures in place, sleet and freezing rain will occur in the mountains and some foothills. How far south the freezing/frozen precipitation gets will be dictated by how cold the low level airmass gets and how far south it oozes. Will likely need a winter weather advisory for at least the mountains but impacts should be fairly low with untreated roads being the main concern. We aren't forecasting enough FZRA at this time to cause much trouble with respect to power outages. The precipitation comes to an and with FROPA by around 12z Thursday.

Have lowered temperatures across southern zones on Wednesday as it's typical in March for warm fronts to not make much headway past the NH/MA border in these setups.

Flood risk remains low, but ice jams remain possible.

KEY MESSAGE 2 DESCRIPTION...

Thursday has a brief chance to warm up in the morning as low pressure crosses through New England, and barely brings the warm sector into southern areas. There is still question as to whether it will actually break through the lingering cold air dam, but afternoon mixing behind the front should bring highs into at least the 40s downwind of the mountains. A cooler, but seasonable airmass returns for Friday and Saturday with highs in the low to mid 40s downwind of the mountains, and in the 30s across the north.

A system is then possible for Friday night into Saturday, but has trended further north and a bit weaker since yesterday. This would result in more showery precipitation, with the best chance for snow across the north. There is still time for this to change over the coming days, but for now the trend looks to be toward a less impactful system.

Temperatures likely trend cooler by late weekend and into early next week as high pressure pressed in from the north. Another system is possible early next week, but with it being nearly a week out it's still too early to try to nail down any details on this system.

AVIATION /12Z TUESDAY THROUGH SATURDAY/

Through Wednesday night...VFR today and tonight with light winds. Becoming IFR late tonight and LIFR on Wednesday through Wednesday night as rain (mountain frozen precip) arrives. A strengthening SSW low level jet will bring the threat of low level wind shear Wednesday night.

Outlook...

Thursday. Conditions likely start to improve from west to east later in the day on Thursday.

Thursday night: Mainly VFR expected.

Friday: VFR, but chances for restrictions/precipitation increase late in the day across northern and western terminals.

Friday night: IFR possible with light snow, especially north and west.

Saturday - Saturday night: Most sites return to VFR by the afternoon.

MARINE

Conditions are expected to be fair through the day today with sub-SCA conditions expected. Easterly winds may approach SCA levels Wednesday, but are more likely Wednesday night as southerly flow increases ahead of a cold front that will cross during the first half of Thursday. Wind gusts may approach gale force ahead of the front. Marginal westerly gales are then possible behind the passing cold front on Thursday into Thursday night. Southerly gales are then possible ahead of an approaching system Friday night. High pressure then presses in late Saturday night into Sunday.

CLIMATE

Temperatures on Tuesday will approach daily record highs at long term climate sites.

Site Location Forecast Temperate Record Temperature Record Year Augusta 66F 64F 2016 Concord 71F 72F 1878 Portland 66F 66F 2016

GYX WATCHES/WARNINGS/ADVISORIES

ME...None. NH...None. MARINE...Small Craft Advisory from 6 AM Wednesday to 6 AM EDT Thursday for ANZ150>154.