textproduct: Gray - Portland

WHAT HAS CHANGED

Low temperatures this morning are colder than previously expected. Otherwise, little change since the previous forecast cycle.

6am Update...Pivoting focus to the forthcoming tide cycles that will bring coastal water levels into Action stage this morning, this evening, and Monday morning. Monday's tide remains the highest forecast, nearing minor flood stage.

KEY MESSAGES

1. Minor coastal flooding remains possible, especially during the Monday morning high tide cycle.

2. Temperatures will warm back closer to normal through mid next week with colder readings returning by the weekend. A couple of weak clipper systems will bring periodic chances of light snow mid to late week.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION... High astronomical tides combined with between 1.5-2.0 ft of storm surge from distant low pressure over the open North Atlantic will bring total water levels to near minor flood stage both this morning and especially Monday morning.

Northeast flow parallel to the coast are a favorable direction to help build water along the coast via the Ekman Spiral. This flow continues for much of the day today, with a gradual turn north by this evening as low pressure passes outside the Gulf of Maine. Following Gerling-Hanson plots from coastal buoys, this morning's tide will arrive before long period swell from the passing low. However, the evening astro tides won't be as high.

Monday morning's tide has been modeled as the closest to Minor stage for a number of locations, mainly Portland south along the NH Seacoast. A larger astro tide plus remaining swell and surge will aid in water levels again rising into Action stage with Hampton and Portland both forecast to achieve Minor flood stage. Fly in the ointment will be continuing offshore winds that will aid in knocking down waves, but they will be lighter than Sunday.

KEY MESSAGE 2 DESCRIPTION... Upper level ridging and high pressure at the surface will lead to high temperatures returning to right around normal for this time of year by Monday/Tuesday. Tuesday night into Wednesday, we then transition back into southwest flow aloft as the next shortwave trough/upper low approaches. This wave will lead to some isolated/scattered light snow showers during the day on Wednesday with the best chances in the mountains and vicinity. Highs on Wednesday will be similar to Tuesday but maybe a bit cooler in the mountains and valleys under plenty of cloud cover. Persistent troughing will then lead to more chances of light snow and slightly below normal temperatures through the rest of the week and into the weekend. While it's still a ways out, it appears the next best chance for some widespread light snow will be Friday or Saturday, after which we will also trend back towards colder temperatures.

AVIATION /12Z SUNDAY THROUGH THURSDAY/

Through 12z Monday: Mainly VFR conditions with perhaps some MVFR cigs at KHIE and KLEB through this morning. Ceilings just offshore will go MVFR to IFR tonight into Sunday morning, and have noted some FEW/SCT in coastal terminals in proximity. N winds will increase this afternoon with gusts up to 25 kts and will remain elevated through tonight.

Outlook:

Monday: VFR conditions with NW winds between 5-15 kts, gusts to 25 kts.

Monday night: VFR expected.

Tuesday/Tuesday night: VFR expected.

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

Thursday: VFR expected south, MVFR more likely north. Snow showers possible in the mountains and vicinity.

MARINE

Gale force northerly winds expected today through Monday morning with gusts up to 45 kts and seas of 7-10 ft outside of the bays/harbors. Moderate freezing spray is also likely through Sunday afternoon.

Seas will remain elevated through Monday night outside of the bays at 4-9 ft. Winds and seas will then largely remain below SCA criteria through the remainder of the period.

GYX WATCHES/WARNINGS/ADVISORIES

ME...None. NH...None. MARINE...Freezing Spray Advisory until 1 PM EST this afternoon for ANZ150>154. Gale Warning from noon today to 7 AM EST Monday for ANZ150>154.