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ANZ154 Coastal Waters From Cape Elizabeth, Me To Merrimack River, Ma Out 25 Nm- 318 Am Est Sun Dec 10 2023
.storm warning in effect from late tonight through Monday evening...
Today..S winds 10 to 15 kt with gusts up to 25 kt, increasing to 15 to 20 kt with gusts up to 30 kt this afternoon. Seas 2 to 4 ft. Patchy fog early this morning. Patchy fog late. A chance of rain early this afternoon. Rain likely late. Vsby 1 to 3 nm early this morning, then 1 to 3 nm this afternoon.
Tonight..S winds 25 to 30 kt with gusts up to 45 kt. Seas 4 to 7 ft, building to 8 to 11 ft after midnight. Rain. Vsby 1 to 3 nm.
Mon..S winds 30 to 40 kt, becoming W 25 to 35 kt in the afternoon. Gusts up to 55 kt. Seas 11 to 16 ft. Rain, mainly in the morning. Vsby 1 to 3 nm.
Mon night..W winds 20 to 25 kt. Gusts up to 40 kt in the evening. Seas 8 to 11 ft, subsiding to 5 to 8 ft after midnight.
Tue..W winds 15 to 20 kt, becoming sw 10 to 15 kt in the afternoon. Seas 4 to 7 ft, subsiding to 3 to 5 ft in the afternoon.
Tue night..SW winds 15 to 20 kt with gusts up to 30 kt. Seas 4 to 6 ft.
Wed..W winds 15 to 20 kt with gusts up to 30 kt. Seas 3 to 5 ft.
Wed night..NW winds 20 to 25 kt, diminishing to 15 to 20 kt after midnight. Seas 3 to 5 ft.
Thu..NW winds 15 to 20 kt with gusts up to 30 kt. Seas 2 to 4 ft.
Thu night..W winds 10 to 15 kt with gusts up to 25 kt. Seas 2 to 4 ft.

ANZ100 318 Am Est Sun Dec 10 2023
Synopsis for stonington me to merrimack river ma out to 25 nm high pressure slips east and southerly winds start to increase today with increasing odds for rain and fog. A front will approach the waters and stall as a significant low pressure rides north along it. Storm force winds are expected across the outer waters and penobscot bay with gales in casco bay. During the day Monday winds shift to westerly and will remain quite gusty. Fair conditions towards the latter half of the week will allow winds and seas to gradually diminish.

FXUS61 KGYX 100354 AFDGYX

Area Forecast Discussion National Weather Service Gray ME 1054 PM EST Sat Dec 9 2023

SYNOPSIS
Light freezing drizzle is possible across the interior and Central Maine through tonight. Moisture begins increasing tomorrow as a significant storm approaches passing through the area Sunday night through Monday. This storm will bring the potential for damaging winds, flooding rainfall, and snow across the north. Upslope snow showers linger into midweek before high pressure brings quieter conditions for the end of the week.

NEAR TERM /OVERNIGHT/
1055 PM Update... Another update to keep temperatures cool through the same areas as mentioned in the prior update below.
Little change to the ongoing logic of patchy freezing drizzle and freezing fog through portions of interior western Maine.
Will continue to monitor through tonight.

715 PM Update... Primary update was to hug the coolest of guidance with observational trends showing cool air through the interior of western Maine this evening. I don't think this is necessarily from cold advection to reinforce the CAD; the local airmass is likely undergoing normal diurnal cooling and draining toward the coast as it sinks... setting up an inversion to stave off WAA in southerly flow picking up aloft. This will prolong freezing drizzle/fog potential through the foothills and into the Maine Capitol district through at least midnight, with patchy freezing conditions possibly lingering through the Rt 2 corridor into the morning hours. Given very light reflectivity and a lack of surface stations reporting precip, likely will be sticking to SPSs but will be keeping a close eye through this evening.

Previously...
Warm front remains draped across the middle of the forecast area. Temps are hovering at or below freezing mainly thru the Kennebec River Valley. With WAA expected to continue over the top of shallow cold air...some patchy drizzle will remain possible into the evening. A special weather statement was issued for freezing drizzle until 500 PM...and may need to be extended if temps cannot tick upwards
It may come in waves
as forecast soundings show ample low level saturation currently but drying this evening...followed by more saturation after midnight. Temps are forecast to slowly rise thru the night however...and mitigate the areal extent of the threat.

SHORT TERM /SUNDAY THROUGH MONDAY/
The first half of Sun will be relatively quiet. Continued WAA is expected with warming temps and dewpoints. Some areas of fog will likely develop as the warmer dewpoints ride over snowpack.
Eventually rain overspreads from southwest to northeast. The majority of the action will occur overnight into Mon.

Unfortunately model guidance has not introduced any more confidence to the forecast today...if anything reducing confidence in some aspects. Highest confidence is currently in rainfall forecast...with a widespread 1.5 to 3 inches possible.
The two areas of greatest concern will be the lower Kennebec River Valley and the southeast facing slopes of the mtns...where locally 4 inches is possible. The Hydrology section covers that threat in more detail below.

The wind threat has become more uncertain however. A very sharp low level front is forecast...and will determine how far inland the LLJ winds are able to penetrate. Today guidance has ticked east
leaving the bulk of the wind offshore
and east of the low center. This really only brings the Midcoast to lower Kennebec Valley into play for damaging wind gusts. Around Casco Bay and points southwest...the front may set up too far east for much more than run of the mill gusty winds from the south. Given that it would not take much of a wiggle west to reintroduce those strong wind gusts...I have kept the high wind watch as is.
The timing of max winds is also slightly later...and not well aligned with high tide. Minor flooding is looking less likely from a tidal perspective...but splashover remains a possibility.

Finally we have the snow forecast...also carrying a lower than normal degree of confidence. The column will rapidly cool as the low pressure deepens...and forecast soundings still show the potential for a flash over to snow across western zones. This is especially true for the CT River Valley. Right after change over snowfall rates could be 1 to 2 inches per hour...and wet/sticky snow as well. Even a couple hours of that would be enough for scattered outages due to downed limbs. If easterly ticks continue that could also lead to longer duration snowfall and high totals. I have increased the forecast accumulation down thru the Monadnocks and included some in the valleys. At this time only northern Coos County looks close to criteria...and no headlines have been issued.

Precip ends quickly from southwest to northeast...and transitions to upslope showers by evening. CAA begins in earnest during the afternoon...and this may be the most widespread gusty winds get. A period of near 45 mph gusts is possible for much of the area as winds shift to westerly.

LONG TERM /MONDAY NIGHT THROUGH SATURDAY/
The extended period will be largely driven by trofing across the northeast gradually giving way to ridging building in from the west with an active shortwave pattern. Monday begins with a lifting upper level trof as a winter storm exits the area.
Precipitation will be tapering off as the morning progresses with winds turning westerly throughout the day continuing upslope snow showers. A non-diurnal temperature trend is expected with the highest temperatures occuring in the morning, cooling as the day progresses and cold air advection sets in.

Tuesday will see some brief clearing as narrow ridging crests overhead before another upper level trof swings south of Hudson Bay bringing a return of upslope snow showers as a cold front crosses from the northwest. The pattern becomes more uncertain towards the end of the week as ridging moves in from the west with high pressure building over the eastern CONUS. There is still some uncertainty in the positioning of the high, however most ensembles show it centered over the Ohio River Valley with New England on the northeast edge.
With an active upper level shortwave pattern, the northeast may see some impacts from nearby passing shortwaves at the end of the week.

AVIATION /04Z SUNDAY THROUGH THURSDAY/
Short Term...Areas of MVFR CIGs continue north of the warm front...roughly bisecting the forecast area. Over time tonight those CIGs will lower and fill in to the southwest. Widespread IFR conditions are expected by morning. There is a low chance of some freezing drizzle around AUG...but confidence is too low to include in the TAF at this time. Rain moves into the area from southwest to northeast thru the afternoon Sun. Winds near the coast will be a tricky forecast...as a sharp frontal boundary will leave gusts quite high to the east but fairly ordinary to the west. Highest confidence in the wind is at RKD and then AUG...but farther southwest is more uncertain. A period of LLWS is likely...especially near the coast. Conditions start to improve quickly from southwest to northeast...with MVFR lingering around HIE.

Long Term... Improving conditions are expected Monday for most terminals as low pressure exits the area, however upslope snow showers may linger across the mountains at KLEB and KHIE. Narrow high pressure crests overhead Tuesday with VFR conditions likely before upslope snow showers return Wednesday as a cold front crosses the area.

MARINE
Short Term...Southerly winds will increase starting Sun. Storm force winds become more likely after midnight. It is still not out of the question that some gusts to hurricane force occur Mon morning. There is also going to be a sharp western gradient to wind gusts...and some parts of the coastal waters may only see SCA conditions or gale force gusts. So the storm watch remains in effect for all waters. Storm force gusts outside the bays may linger into Mon afternoon before diminishing. Seas are forecast to build to near 20 ft Mon before gradually diminishing.

Long Term... Winds and seas will be gradually subsiding through early next week, however conditions look to remain above SCA thresholds through Wednesday as a cold front crosses the area. High pressure then settles to the southwest for the end of the week with seas remaining below SCA thresholds with winds out of the west to southwest.

HYDROLOGY
Flood watch remains in effect for Sunday night through Monday evening, with continued river rises thereafter. The warm temperatures and more notably high dewpoints around 50F south of the mountains will combine with blustery/strong winds to decimate the snowpack from the foothills southward. The accompanying heavy rainfall will combine with snowmelt to cause rapid rises on area streams and rivers. Contrarily, the snow in the higher terrain is cold and dry, which supports less snowmelt. The headwaters are still likely to experience flooding just from the 1 to 3 inches of rainfall even with less snowmelt. The rainfall efficiency will be anomalous for this time of year, with the potential for an inch to fall in 6 hours early Monday. The ground conditions are in a variable state of frozen/partially frozen/and near- saturated, which in essence means there will be limited percolation and more rapid runoff.
Concerns are present for overland flash flooding during this period, which will also support rapid flooding of small streams and rivers. The mainstem rivers will swell with flooding likely into Tuesday for some forecast points. Attention will be focused on where the axis of heaviest rainfall and interior penetration of the warm dewpoints materialize.

GYX WATCHES/WARNINGS/ADVISORIES
ME...Flood Watch from Sunday afternoon through Monday evening for MEZ007>009-012>014-018>028-033.
High Wind Watch from late Sunday night through Monday afternoon for MEZ019>028.
NH...Flood Watch from Sunday afternoon through Monday evening for NHZ003>015.
High Wind Watch from late Sunday night through Monday afternoon for NHZ014.
MARINE...Storm Watch from late Sunday night through Monday evening for ANZ150>154.

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