textproduct: Gray - Portland

WHAT HAS CHANGED

Current forecast remains on track. Snow showers and showers are moving across the area, with precipitation likely continuing through the remainder of the day. No significant changes were made.

KEY MESSAGES

1. Showers will continue to move up the coast today. Temperatures will cool down and precipitation may change over to snow for a brief period of time later in the afternoon.

2. A low moves across the interior, bringing a quick round of snow. Up to 3-4 inches are possible across the White Mountains and in central Maine, with 1-2 inch totals elsewhere across the interior.

3. A stronger low pressure system appears likely to bring some locally heavy rain and gusty winds to most of the forecast area early next week.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION... A weak and developing coastal low off of the DelMarVa peninsula will move northeastward through the afternoon. Some of the precipitation from the northern periphery of this low may clip some coastal areas later on this evening. However, no accumulations are anticipated.

KEY MESSAGE 2 DESCRIPTION... An Alberta Clipper moves across the northern tier of the US, arriving in New England by Friday evening. Cold air will be in place and snow will move from west to east. The low looks to redevelop off of the Gulf of Maine, allowing for a more organized round of moderate snowfall once the snow makes it into Maine. Snow should largely exit the region by Saturday morning, though some upslope snow showers in the mountains can not be ruled out during the day Saturday.

KEY MESSAGE 3 DESCRIPTION... We will see rising heights to start the day on Sunday as the next longwave trough begins to approach and we transition into southwest flow aloft. A warm front will extend to the east northeast of a deepening surface low to our west and lift north late in the day. This may lead to some warm air advection precipitation across portions of New Hampshire and western Maine in the evening or night time hours. This far out, precipitation type is a bit uncertain for Sunday/Sunday night but a wintry mix seems likely for some areas. A continued push of low level warm air advection should eventually transition precipitation to all rain by Monday morning. High rain chances will then continue through the day on Monday before gradually moving out by Tuesday morning.

The moisture content for this early week storm is impressive and anomalously high for this time of year. The 00z NAEFS mean precipitable water forecast for 18z Monday is currently in the 99th or higher percentile for all of New Hampshire and western Maine. Additionally, percentiles are similar when looking at 925mb/850mb specific humidity and integrated water vapor transport fields. Thus, all signs point to this system having plenty of moisture to work with so some periods of locally heavy rain seem likely. This activity should work to flush out most of the remaining ice in the rivers with some chances for flooding, mainly due to the ice jam potential. While the anamolous moisture will be in place and lead to some heavy rain, the relatively progressive nature of this system will keep totals mitigated somewhat. Overall liquid totals look to generally be in the one to two inch range as the NBM is suggesting a 50 to 70 percent chance for an inch of rain or greater, but only maxing out around 20 percent for two inches. Also of note will be the potential for gusty southeasterly winds late Sunday night through Monday as NAEFS 850mb winds are forecast to be in the 99th percentile or above for much of the area. Meridional wind components in the lower levels are also forecast to be quite anomalous which makes sense given the highly amplified flow. Thus, we may have to be on the lookout for eventual wind headlines and a low power outage threat on Monday depending on how the forecast evolves.

After the early week system moves out, the rest of the week appears fairly quiet with only a couple of weak waves forecast to move through and colder air.

AVIATION /18Z THURSDAY THROUGH TUESDAY/

18Z THURSDAY THROUGH FRIDAY...Conditions look to improve Thursday afternoon as a cold front moves through the area. VFR is expected tonight and will continue through Friday morning. Conditions deteoriate Friday afternoon as snow starts to move into the region from west to east.

Outlook:

Friday Night and Saturday: IFR with snow likely across northern terminals, with MVFR to IFR possible across southern terminals. Gradual improvement likely through the day from south to north.

Saturday Night: VFR likely returns to all terminals, except HIE which may hold MVFR ceilings in upslope flow.

Sunday: VFR, no sig wx. Clouds thicken and lower in afternoon.

Sunday Night and Monday: MVFR to IFR cigs with any wintry mix transitioning to rain Monday morning. Rain and gusty southeast winds likely Monday.

Monday Night: IFR likely continues with periods of rain and breezy conditions.

Tuesday: Becoming MVFR to VFR through the day as precipitation moves out and clouds start to diminish.

MARINE

SCA northwesterly winds are expected to continue this afternoon and through most of the day on Friday. During the day on Friday winds slacken below SCA levels and shift to southerlies by the end of the day. Southerly winds look to quickly strengthen to at least SCA levels by Friday evening. Seas of 3-8ft are expected through the period, with more 3-5ft waves in the bays and 6-8ft waves across the open waters.

Marginal southerly gales are possible Friday night ahead of an approaching low pressure system. Westerly gales are then more likely Saturday behind the passing system. High pressure crosses the waters Saturday night and Sunday. Southeasterly gales are then likely by late Sunday night through Monday night as a strong low pressure system tracks through the Great Lakes.

GYX WATCHES/WARNINGS/ADVISORIES

ME...None. NH...None. MARINE...Small Craft Advisory until 8 AM EDT Friday for ANZ150>152-154.