textproduct: Gray - Portland

WHAT HAS CHANGED

No significant changes since last forecast package other than to issue winter weather advisories for mainly mixed precip and some moderate snow accumulations.

KEY MESSAGES

1) Expect a period of gusty winds this morning behind a passing cold front. The strongest gusts will be in the 40 to 50 mph range across the northern portions of Oxford, Franklin, and Somerset counties. Stronger winds likely over the higher terrain.

2) Snow and mixed precipitation will likely lead to slick travel conditions as the next system moves in tonight and sticks around through the day Sunday.

3)Cold and breezy Monday, then above normal temperatures return through midweek.

4)Temperatures become more seasonable late week following a weak clipper (or 2) that may bring some rain and snow Tuesday (mainly in the mountains) and Wednesday night.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION... A strong cold front will cross the forecast area this morning from northwest to southeast. Behind the front, expect strong pressure rises and cold air advection coupled with a stout low level jet at 850 mb (~70 knots). While diurnal timing will not be optimal, we will likely see some 40 to 50 mph gusts along the northern portions of Oxford, Franklin, and Somerset counties. Even higher gusts in excess of 60 mph are likely along the ridge tops and higher terrain. These conditions could lead to a limited power outage threat. Further south, mixing is a bit more uncertain but some gusts in the 25 to 35 mph range will be possible. A short duration Wind Advisory remains in effect for northern Oxford, Franklin, and Somerset counties through 13z this morning.

Winds will then be quick to relax this afternoon as high pressure moves into the region and low level warm air advection returns. Temperatures on Saturday will once again be well above normal for this time of year, with highs expected to mainly range from the lower 30s to the lower 40s. This will mean that a controlled melt will continue today but no flooding is expected except for some nuisance poor drainage issues.

KEY MESSAGE 2 DESCRIPTION... The next shortwave approaches in southwest flow aloft tonight into Sunday, leading to widespread high chances (>80 percent) of precipitation. While precipitation looks to mainly be snow across the north and most of the central, forecast soundings suggest we will likely see a mixed bag somewhere across southern New Hampshire and/or coastal Maine. The cold air damming setup is not ideal with such mild temperatures expected at precipitation onset. Thus adding to the uncertainty in eventual temperature profiles. Somewhere over southern New Hampshire, there is likely to be a narrow strip of freezing rain and/or sleet and some light ice accumulations will be possible Sunday morning. Farther north where snow will be the primary precipitation type, a broad 1 to 3 inches appears possible with some locally higher amounts possible across the Northern Kennebec Valley. By Sunday afternoon, precip should either be all rain or all snow as the rain/snow line sags south into the evening. Precipitation will then gradually diminish Sunday night. Based on mainly the mixed precip threat a winter weather advisory has been issued. Though some zones in the western Maine mountains may see 4 or more inches accumulation.

KEY MESSAGE 3 DESCRIPTION... Precipitation wraps up Sunday night as low pressure departs to the northeast. The region remains under a broad trough allowing for colder air to move in behind the system. Monday would feel more seasonable with highs expected to climb into the low to mid-30s south of the mountains and 20s to the north under partly cloudy to mostly sunny skies. However, low pressure deepens as it moves into Atlantic Canada tightening the gradient between high pressure nosing in from the southwest. BUFKIT soundings suggest gusts nearing 40 kts at the top of the mixed layer early Monday morning which would be good for surface gusts near 35 mph. Gusts 25- 35 mph continue through the day, but the pressure gradient will also be easing so expect gusts easing toward the lower end of the range as the day goes on. This makes temperatures feel more like single digits below zero in the north and single digits above zero to the south early Monday morning, only improving to feeling like single digits and low teens in the north, and upper teens and low 20s to the south, by the afternoon.

A trough begins digging into the central U.S., building a shortwave ridge over the northeast Tuesday allowing temperatures to climb into the upper 30s and low 40s south of the mountains. The north may hold on to some clouds and end up more in the low to mid-30s. Southwesterly flow continues into Wednesday as the trough deepens to our west, so highs climb into the low to mid 40s in the south and into the mid- to upper 30s in the north.

KEY MESSAGE 4 DESCRIPTION... Surface low pressure makes a run at the area Tuesday night, but with the area underneath the aforementioned ridge, any precipitation (likely light snow) is probably confined to the mountains. Low pressure then passes to our north Wednesday night dragging a front through the area. Locations south of the mountains should start out above freezing after a warm day, and thusly see rain to start. Locations to the north top out with the more marginally warm temperatures, so they likely fall below freezing before precipitation starts. Again this is likely light as ensembles suggest the front is moisture starved.

A deep trough continues to dig eastward and this trends our temperatures back to seasonable values if not slightly below normal. However, ensembles are split on just how deep this trough digs, and were it centers itself. This is a big deal because most ensembles have a low pressure system moving up the coast late in the week. The latest solutions suggest the trough digs way down into northern Florida generating the low well offshore and blocking it out from our area as it swings eastward. However, this is a period to watch as any changes in the amplification of this trough could bring a system closer to our shores and models have been flip-flopping.

AVIATION /06Z SATURDAY THROUGH WEDNESDAY/

Ceilings should improve through the morning, with some MVFR values likely to hang on across the north through the day, potentially impacting KHIE. A cold front will move across the region this morning, shifting winds to out of the west or northwest which may also lead to a period of enhanced low level wind shear at most terminals.

The next system then approaches tonight, which will lead to increasing chances of precipitation and the potential for LIFR to MVFR conditions into Sunday morning. Precipitation will mainly be snow across the north and central, but a brief period of freezing rain and/or sleet may develop somewhere over southern New Hampshire, potentially impacting KMHT or KCON. KPSM and KPWM should mainly see rain.

Outlook:

Sunday: Periods of snow, wintry mix, and freezing drizzle. IFR conditions likely. Some improvement to MVFR possible across southern NH late.

Sunday night: IFR gradually improving as snow showers taper off. Westerly wind gusts 25-30 kts possible at all terminals.

Monday: Any lingering MVFR improves to VFR as the day goes on. Westerly wind gusts 20-30 kts possible at all terminals, easing into Monday evening.

Monday night: VFR prevails at most terminals. MVFR possible at HIE.

Tuesday: VFR prevails at most terminals. MVFR possible at HIE.

Tuesday night: IFR possible in snow showers at LEB and HIE. MVFR restrictions more likely at other terminals in light rain showers.

Wednesday: LEB and HIE gradually improve to MVFR as snow tapers off. MVFR prevails at all other terminals.

MARINE

Winds shift from out of the southwest to out of the west early this morning with gusts to Gale Force after a cold front swings through the area. Winds and seas will trend downward through the day, trending to SCA and then becoming light and shifting to out of the east by tonight. SCA conditions are then possible in northeast flow Sunday as low pressure tracks through the Gulf of Maine.

Westerly winds potentially ramp up to gale force Sunday night as low pressure passes through the Gulf of Maine and deepens as it continues northeastward. Seas also build 5-8 ft. The threat for gales tapers off Monday afternoon, but SCA conditions may continue through much of next week as the weather pattern remains active.

GYX WATCHES/WARNINGS/ADVISORIES

ME...Wind Advisory until 8 AM EST this morning for MEZ007>009. Winter Weather Advisory from midnight tonight to 7 PM EST Sunday for MEZ007>009-012>014-018>022-024>028-033. NH...Winter Weather Advisory from midnight tonight to 7 PM EST Sunday for NHZ006. Winter Weather Advisory from 7 PM this evening to 7 PM EST Sunday for NHZ005-007>011-015. MARINE...Gale Warning until 7 AM EST this morning for ANZ150-152. Gale Watch from Sunday evening through Monday afternoon for ANZ150-152-154. Small Craft Advisory until 7 AM EST this morning for ANZ151- 153-154.