textproduct: Gray - Portland

WHAT HAS CHANGED

No major changes were needed for this forecast package update. Messaging generally remains the same.

KEY MESSAGES

1. Mild temperatures continue through the rest of today with colder temperatures expected tomorrow and into the next work week. A little bit of light snow is possible on Sunday.

2. Low pressure brings the next chance at widespread wintry precipitation, mostly in the form of snow, late Tuesday through early Wednesday. The snow may arrive early enough to impact the afternoon and evening commute in some areas.

3. Confidence is high for an active pattern for the second half of the week into next weekend with a strong signal for at least one round of widespread precipitation. However, confidence in p-types and timing is low.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

A surface warm front has lifted north across the region, leading to widespread mild temperatures early this afternoon. Highs will generally be in the 40s outside of the mountains with a couple of low 50s readings not out of the question across southern New Hampshire. Highs will mainly be in the 30s over the mountains.

A few rain or snow showers will be possible across the mountains this afternoon as a cold front approaches from the west, but most of the synoptic forcing will remain north of the International Border. Some guidance then has this cold front/surface low stalling out over the outer waters as the next shortwave approaches. This could lead to some light snow on Sunday depending on the eventual low track. The best chance looks to be across southern New Hampshire/southwest Maine where a dusting to an inch or so will be possible. The main concern will be some slippery travel conditions Sunday morning into the early afternoon.

It will be colder behind the cold front with lows tonight ranging from the single digits above zero north, to the lower 20s south. Highs on Sunday will also be colder, ranging from the low to mid teens north, to the upper 20s and lower 30s south. Below zero lows return to the north Sunday night into Monday morning, with values only reaching into the lower single digits above across the south. Highs on Monday will range from the upper single digits and lower teens north, to the low to mid 20s south.

KEY MESSAGE 2 DESCRIPTION...

Tuesday starts dry but with clouds increasing and then lowering as the column moistens ahead of the next system. Based on forecast soundings, enough moisture and lift from WAA will be present to allow light snow to overspead northern New England from west to east later in the day, potentially arriving early enough to impact the evening commute in some areas. Snow continues into Tuesday night but will begin to taper off late and toward Wednesday morning. Ensemble means are generally ranging from 0.25" to 0.50" of QPF with this system, yielding roughly a 2-4" snow with SLRs expected to be close to or even slightly lower than 10:1. There are also a few wetter ensemble members suggesting a corridor of 4-6" is a possibility. As the column warms, there may be a brief period of sleet or freezing rain and even a change to plain rain, and if this were to occur it would most likely be across southern NH.

Any lingering precip ends Wednesday morning with a warm and dry rest of the day with mostly sunny skies by the afternoon. Temperatures will be mostly in the 40s.

KEY MESSAGE 3 DESCRIPTION...

The 500mb pattern stays progressive from late week and into next weekend with a strong ensemble signal for at least one wave of low pressure to bring more widespread precipitation, around Thurs night or Friday and then possibly another Saturday. However, the GFS is earlier and more Wednesday night-Thursday. It does appear that there will be warmer air to work with, but that being said there are still colder solutions like the ECMWF hinting at more of a CAD situation (which could end up in a wintry mix). This will be sorted out in the coming days, but the main takeaway is that confidence is high in at least one round of widespread precipitation in the Thurs-Sat window, but confidence is low on details such as p-type(s) and timing.

AVIATION /18Z SATURDAY THROUGH WEDNESDAY/

Through 18z Sunday...An approaching cold front may bring scattered rain and snow showers to the mountains this afternoon. Local MVFR or lower conditions are possible, mainly at HIE. Otherwise, VFR conditions are expected with gusty southerly winds. Some more light snow is possible at CON/MHT/PSM/PWM Sunday morning and into the early afternoon with localized MVFR visibilities possible.

Outlook...

Sunday night thru Monday night: Improving to VFR in the evening and overnight as high pressure settles overhead.

Tuesday-Tuesday night: VFR initially, but conditions are expected to deteriorate to IFR or lower as widespread light snowfall overspreads the area from west to east during the afternoon and evening. Snow should gradually end overnight Tuesday night. Also can't rule out a brief period of -PL/-FZRA or even RA at MHT, CON, PSM, and PWM.

Wednesday: Improving conditions with any leftover precip coming to an end in the morning. Mainly VFR otherwise.

Wednesday night and Thursday: Another chance of widespread precipitation/restrictions but could be closer to Thursday night or Friday.

GYX WATCHES/WARNINGS/ADVISORIES

ME...None. NH...None. MARINE...Small Craft Advisory until 9 PM EST this evening for ANZ150>154.