textproduct: Gray - Portland

SYNOPSIS

Temperatures remain below normal through at least Monday. Snow showers will stay mainly in the mountains, but widespread light snow is possible Monday night as a clipper moves through. High temperatures remain in the 20s or colder through the upcoming weekend. A warmup arrives by midweek next week as a ridge builds across the Northeast.

NEAR TERM /THROUGH SATURDAY/

640 PM Update... Mainly clear skies persist at this hour for most locations south of the mountains with snow flurries and cloud cover across the mountains and towards the Canadian Border. A few locations are already starting to decouple and local wind speed probability plots indicate a general downward trend through the night across many locations south of the mountains. I am expecting that many of the locations that managed to decouple last night will do so again tonight, and therefore based on observed lows from this morning, went ahead and lowered forecast lows by a few degrees in these locations. Otherwise, the forecast remains largely unchanged.

Previously... Below normal temps continue tonight but not quite as cold as last night. The upper trof axis will cross the area this evening and may be followed by a secondary trof overnight. This will primarily keep the cold advection going and keep the breeze up overnight. As a result wind chills are forecast to fall to 20 to 25 below in parts of the western Maine mtns again. A cold weather advisory has been issued. There may also be a slight uptick in upslope snow shower activity with the passing of each shortwave, so I have added PoP and flurry wording to the forecast beyond what the NBM guidance showed.

SHORT TERM /SATURDAY NIGHT/

More below normal temps expected Sat and Sat night. High temps Sat remain in the teens and 20s once again, but the winds will be less gusty than the past two days. Aside from upslope snow showers that will be winding down, the next best chance for precip comes Sat night.

A passing southern stream shortwave trof will remain well south of the area, but there is a trailing northern stream shortwave that will be robust enough for broad lift across the region. While it will generally be more moisture starved because of the southern partner, there could be some light snow across southern parts of the forecast area especially. At this time I am anticipating around an inch or less.

LONG TERM /SUNDAY THROUGH FRIDAY/

Key Messages: 1) High Astrotides could bring minor coastal flooding. (see Coastal Flooding section for more details) 2) Average to below average temperatures this weekend. 3) Light snow likely Monday night. 4) Warming trend likely to arrive by mid-next week.

A 500mb trough will engulf the northeast on Sunday, bringing continued cold and dry conditions through the remainder of the weekend. Sunday night will feature light winds and clear skies, allowing for radiational cooling to develop. This could allow lows to bottom out to near or below 0F across northern New England. A weak clipper moves in Monday night, likely bringing some light snow to the area. A pattern flip occurs afterwards, with mid- level ridging starting to build in on Tuesday. This will allow for a warming trend through next week. Highs in the lower 40s are possible by the end of next week, with no signs of a pattern change beyond this.

AVIATION /00Z SATURDAY THROUGH WEDNESDAY/

Short Term...Generally VFR conditions anticipated thru Sat night. Some gust westerly winds possible thru this afternoon, up to 25 kt at times. Upslope snow showers remain possible and local MVFR or lower conditions may result. This is unlikely to affect any TAF sites, but HIE would be the most likely. There is a low confidence chance of light snow Sat night with a passing system. Snow would be most likely over the southern half of the forecast area, and some areas of IFR or lower conditions would be possible if that occurs.

Long Term...No restrictions to aviation are expected until Monday evening. Some light snow Monday night may allow for some brief periods of lowered restrictions. VFR is expected Tuesday, though lower restrictions may arrive for the second half of next week as a system may move through the area.

MARINE

Short Term...No restrictions to aviation are expected until Monday evening. Some light snow Monday night may allow for some brief periods of lowered restrictions. VFR is expected Tuesday, though lower restrictions may arrive for the second half of next week as a system may move through the area.

Long Term...Northwesterly winds strengthen to SCA thresholds by Sunday night as a weak clipper moves through the region. Conditions will improve and go below SCA thresholds by Monday morning. The rest of next week features 8-12kt southerly winds. Seas of 2-4ft are expected Sunday through Wednesday. Seas may increase at the end of next week.

TIDES/COASTAL FLOODING

Astronomical tides continue to tick upwards as we approach the full moon. Currently there is little surge along the coast with winds largely offshore and continuing that way thru Sat. However tides will be increasing to over 11 ft without surge and I do anticipate that as offshore winds relax that water levels may slosh back towards the coast a bit. Guidance seemed overly high on the surge threat, especially by Sun at over 1 ft. The ETSS guidance looked like a fair compromise, closer to 0.5 to 0.75 ft. The result is near flood stage during the morning high tide Sat, and bumping just up to flood stage Sun. It is possible that coastal flood advisories may be needed by the time Sun rolls around.

GYX WATCHES/WARNINGS/ADVISORIES

ME...Cold Weather Advisory from midnight tonight to 9 AM EST Saturday for MEZ008-009. NH...None. MARINE...Small Craft Advisory until 4 PM EST Saturday for ANZ150-152- 154.