textproduct: Gray - Portland

WHAT HAS CHANGED

No significant changes since the last forecast package for the rest of this week.

KEY MESSAGES

1. Astronomical tides remain high Tue but diminishing storm surge is expected to keep water levels below flood stage.

2. Weak systems bring reinforcing shots of cold air and chances for snow showers Wednesday into Thursday night.

3. A potent short wave crosses Friday night through Saturday bringing chances for snow followed by Arctic air arriving on gusty NW winds into Sunday. Cold Weather Headlines will likely be needed centered around Saturday night.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION... Some minor coastal flooding and splashover occurred today at high tide and astronomical tides remain high Tue. Nearshore wave heights will be coming down thru the overnight which will reduce the storm surge, but at the same time offshore winds will also relax and allow some of the water level to slosh back towards the coast. So all in all I anticipate surge Tue between one half and one foot. This should keep water levels below flood stage, but some splash over may still occur at particularly vulnerable coastal locations.

Otherwise, clear skies tonight and weakening pressure gradient will allow winds to drop after sunset. Additionally a narrow ridge of high pressure will build in overnight. The set up looks pretty good for strong radiational cooling. NBM guidance currently keeps temps in the single digits to just below zero, but given several nights of double digits below zero in the northern valleys I do not see why we do not do it again tonight. Opted to blend 10th percentile NBM guidance with MAV MOS to get low temps into the mid teens below zero in the north and near zero in the southern zones.

KEY MESSAGE 2 DESCRIPTION... A pair of compact short waves will cross northern New England Wednesday through Thursday night. Moisture will be limited with this systems so not expecting much more than scattered snow showers. The highest chances (30 percent) will occur Wednesday into Wednesday evening across the mountains towards the Mid Coast. Near the Mid Coast model soundings show modest moisture and lift within the dendritic growth zone. This combined with some low level instability could result in snow showers here putting down a quick coasting of snow creating slick travel. The next wave arrives Thursday and looks to have even less moisture resulting in lower chances for snow showers. Shots of colder air will occur with each passing system while they will be less noticeable that what happens this weekend.

KEY MESSAGE 3 DESCRIPTION... The Polar Jet will dive southeast across the Great Lakes extending towards the Mid Atlantic region late this week. A more potent short wave will approach the Northeast from Hudson Bay Friday. A multi model consensus shows the short wave shearing out with some of the mid level forcing being shunted out to sea off the Mid Atlantic in the vicinity of the left exit region. This will result in cyclogenesis well offshore Saturday while the remaining forcing from the short wave crosses northern New England. Chances for snow will increase Friday night and will persist into Saturday with light accumulations possible by Saturday morning. Low pressure will continue to deepen in the vicinity of Nova Scotia Saturday into Saturday night setting up a tight gradient over New England. Late Saturday through Sunday looks windy with an Arctic airmass taking aim at the forecast area. Sub zero wind chills are likely during the day Saturday with Cold Weather Headlines likely needed for Saturday night.

AVIATION /18Z MONDAY THROUGH SATURDAY/

Through 18Z Tuesday... Widespread VFR conditions thru Tue night. As a weak area of high pressure builds in winds will also be light, generally from the west or northwest.

Outlook:

Tuesday night: VFR Expected with light and variable winds.

Wednesday - Wednesday night: MVFR possible north, VFR more likely elsewhere. Snow showers possible.

Thursday - Friday: VFR expected south, MVFR possible north.

Friday night - Saturday: MVFR and snow showers possible across the entire area. NW winds could gust to 30 kts late Saturday.

MARINE

Gusty offshore winds continue today as ocean storm pulls away from the region. Winds will diminish this evening, while seas will take until early Tue to fall below 5 feet. SCAs will remain in effect outside of the bays until Tue morning, otherwise winds and seas will remain below SCA thresholds into Wed. Especially overnight as temps fall towards or into the single digits, light freezing spray will continue despite diminishing winds and seas.

Marginal SCA conditions possible late Wednesday and Wednesday night in offshore flow. Light freezing spray is likely Wednesday night and Thursday night. A strong cold front crosses Saturday bringing Gale force offshore winds and moderate to heavy freezing spray.

GYX WATCHES/WARNINGS/ADVISORIES

MARINE...Small Craft Advisory until 7 AM EST Tuesday for ANZ150-152-154.