textproduct: Gray - Portland

SYNOPSIS

Temperatures turn bitterly cold behind a front tonight with wind chills below zero across the area. The next storm looks to mostly miss our area to the south, but some light snow is possible over southern New Hampshire Saturday. Then a more robust winter storms sets its sights on New England Sunday night into Monday. While this storm does appear to transition to rain at some point on Monday, initial mixed precipitation and snow may bring significant travel disruptions given the expected high volume of holiday travelers.

NEAR TERM /THROUGH TONIGHT/

As of noon today, a weak frontal boundary has moved southward. This front brought some light snow to the region this morning. Behind the front, we should expect to see winds pick up from the north, becoming breezy to gusty at times this evening. This will allow for tonight to feel particularly cold, despite most places only in the teens this evening. For instance at 7PM tonight, we have Lewiston forecast in the upper teens. With the wind, Lewiston will have a wind chill near 0F. Winds peak this evening, with winds starting to calm down as temperatures continue to drop. Despite this, wind chills are still likely to bottom out near -10F for most by Friday morning.

SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/

Persistant troughing from a high to the northeast will continue to bring chilly temperatures and mostly dry conditions to the area tomorrow. Light northerly winds through the day will allow for cold air advection, and temperatures will have a harder time warming up. Highs look to be in the teens to lower 20s along the coast, with lower teens in the mountains.

A low will miss New Hampshire to the southwest tomorrow night. This low will bring snow to southwest New Hampshire Friday night. A a few inches can not be ruled out in Cheshire county. Snow should keep southern NH warmer Friday night, with lows in the teens expected as falling snow may help with mixing. Elsewhere, tomorrow night will be very cold, with low temperatures in the single digits along the coast, below zero north of the mountains. Calm winds, fresh snowfall should help bring lows colder but mostly cloudy skies are still expected across most of the area.

LONG TERM /SATURDAY THROUGH THURSDAY/

Pattern Overview: The long term starts with an upper level ridge building into the area which will allow for warmer temperatures aloft which may cause some precipitation type problems as surface low pressure moves through early next week. Afterward, we end up under a broad trough for the remainder of the period which keeps snow showers in the forecast, especially in the mountains. Impacts and Key Messages: * A mixed precipitation event may impact post-holiday travel Sunday night and Monday. Details: Saturday: Any snow that reaches our area tapers off Saturday morning as the low continues out to sea and high pressure quickly builds in behind it. Clearing skies allow high temperatures to rise into the mid- to upper 20s south of the mountains, and into the upper teens and low 20s north. Skies remain clear and winds remain light as high pressure slides overhead Saturday night. This likely allows for a very cold night with temperatures falling into the single digits south of the mountains, and just below zero to the north. Sunday and Monday: A ridge begins to build in aloft on Sunday, and at the same time surface low pressure approaches from the west. This means we start the day clear, but start to see clouds move in beginning in the afternoon. Temperatures should be able to rise into the low to mid 30s south of the mountains before it gets to cloudy, with mid- to upper 20s to the north. As of now it looks like precipitation is going to hold off until late Sunday night/early Monday morning, but with the ridge becoming centered overhead it could be a mixed bag. The southwesterly flow aloft warms temperatures above freezing, while low pressure sucks in colder air at the surface, but the key is going to be how deep that near surface cold air actually gets. The high pressure to the northeast appears to get pushed out quite quickly among model solutions, so this isn't the strongest signal I have ever seen for an icy event. With that being said, there is time for that to change and a wintry mix is certainly in the cards, so have tailored the weather grids to message that, but also made sure they avoided straight freezing rain as the uncertainty in the synoptic setup remains high. Mixed precipitation lasts through Monday morning, but by the afternoon low pressure moves overhead and the ridge slides offshore which means we should be able to transition to just rain (south of the mountains) and snow (north). Precipitation tapers off Monday night. Tuesday-New Year's Day: Global models are in reasonably good agreement that we end up in a broad troughing pattern to end the long term period, which means some locations may be ringing in the new year with a few showers. Otherwise, there is no strong signal at this point for anything overly impactful during the New Year's holiday time frame.

AVIATION /18Z THURSDAY THROUGH TUESDAY/

Short Term...MVFR restrictions are possible in the mountains this afternoon with upslope snow showers. VFR expected elsewhere. VFR expands into the mountains by tonight, with VFR continuing everywhere through most of the day Friday. Restrictions are likely at KEEN and KLEB Friday night as snow moves into the area. These restrictions may potentially reach out to KMHT and KCON as well for a brief period. VFR remains in the north and across Maine locations through Saturday morning.

Long Term...Conditions improve back to VFR Saturday morning for areas that will see snow overnight. VFR then prevails through the day Sunday before ceilings begin to lower Sunday evening. Widespread IFR is possible late Sunday night/early Monday morning as mixed precipitation moves into the region. Visibilities should improve some south of the mountains as the wintry mix transitions to plain rain. North of the mountains transitions to snow so HIE likely continues to see restrictions. Conditions improve back to VFR areawide Tuesday as precipitation tapers off.

MARINE

Short Term...Gale force northerly winds are expected this evening, continuing through Friday morning. Seas of 4-7ft are expected and freezing spray is likely across the in the open waters east of Casco bay, including Casco and Penobscot Bay. Northerly winds persist but weaken considerably by Friday afternoon, as high pressure moves overhead. Seas also gradually lower through the day Friday, becoming 2-4ft by Saturday morning.

Long Term...Conditions below SCA criteria are expected through the weekend. A system passes through Sunday night and Monday, and behind it winds ramp up with gusts potentially to gale force. This also builds seas 4-7ft. The stronger gusts taper off heading into mid- week, but SCA conditions continue through at least Thursday.

GYX WATCHES/WARNINGS/ADVISORIES

ME...None. NH...None. MARINE...Gale Warning from 4 PM this afternoon to 10 AM EST Friday for ANZ150>154. Freezing Spray Advisory from 10 PM this evening to 10 AM EST Friday for ANZ150>153.