textproduct: Gray - Portland

WHAT HAS CHANGED

The Coastal Flood Watch for coastal York and coastal Rockingham has been converted to a Coastal Flood Advisory.

As the southern trend continues for the track of the nor'easter, precipitation will be slower to get going. Most of the forecast area should remain dry until late Saturday with most of the rain likely on Sunday and Monday. Winds have also trended down just a touch.

KEY MESSAGES

1. Dangerous surf and marine conditions continue through the weekend and possibly into Monday with large breaking waves and a high risk of rip currents. Minor coastal flooding and splash-over are possible for several high tide cycles from Saturday morning through late Sunday evening, mainly for coastal York and Rockingham counties.

2. The nor'easter will also lead to some widespread beneficial rain and gusty northeast winds through at least Monday. Mainly dry and warmer mid to late week.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

The center of the developing nor'easter is currently located due east of the Carolinas with a low-level circulation seen very well on latest visible satellite. The nor'easter is forecast to slowly lift northward and deepen through tonight and Saturday before stalling out and meandering south of southern New England toward the Mid-Atlantic coast through the weekend.

Even with a slower trend moving north, winds and seas have already started to respond to the tightening pressure gradient with the last Jeffrey's Ledge buoy observation coming in with just under 12 ft wave height as of 2 PM. Surf conditions will further deteriorate and remain dangerous through at least the weekend as swells and the long fetch of brisk northeast winds continue to build seas over the Gulf of Maine. The High Surf Advisory lasts through the day Sunday for large breaking waves and a high risk for rip currents, and there are indications that these conditions may last through Monday with the nor'easter slowing its departure. So it's possible a High Surf Advisory or Rip Current Statement will be needed on Monday.

We're also entering into high astronomical tides, and the long- duration of brisk northeast winds and 1-2' of storm surge will bring the potential for minor coastal flooding and splash-over. This is more likely for coastal York and coastal Rockingham counties where minor coastal flooding/beach erosion will be possible over multiple high tide cycles over the weekend as the northeast winds continue to push water toward the coastline. A Coastal Flood Advisory has been issued to cover this potential for coastal York/Rockingham from Saturday morning through late Sunday evening.

KEY MESSAGE 2 DESCRIPTION...

The trend has continued for the nor'easter to slow it's progression north as dry high pressure to the north wins out. The low will stall out off the Mid-Atlantic coast Saturday and Sunday before finally moving up the coast and out to see at the beginning of the next work week.

Our area will be under a decent pressure gradient with high pressure to the north and the nor'easter to our south but the threat for stronger winds may have backed off just a bit as the low continues to trend further south. Forecast soundings at Portsmouth still suggest we could see some winds in the 40 to 45 knot range at the top of the mixed layer across southeast New Hampshire late Saturday through Sunday morning but available momentum should decreasing north and east. In general, it appears that the strongest gusts will be over portions of southeastern New Hampshire and southwest Maine to around 40 mph. Elsewhere expect breezy northeast winds gusting 25 to 35 mph. While winds will not be overly strong, this will be a rather long duration event with winds increasing late tonight and potentially lasting into next week. Thus, with plenty of leaves on the trees there could be a limited power outage threat, especially along the coast and portions of the interior.

The trend south will also impact the precipitation forecast. While we are still expecting a beneficial soaking rainfall for much of the southern and coastal areas, rainfall chances may not really start to increase until Saturday with the best chances now on Sunday and Monday. As the nor'easter stalls out off the Mid-Atlantic coast, rainfall will be slow to progress north so many areas may just experience a dry and breezy Saturday with a rainier end to the weekend. NBM probabilities suggest a 70 to 90 percent chance for least an inch of rain over southern New Hampshire and southwest/coastal Maine through Monday. The probabilities for at least 2 inches over the same time-frame are maximized over southeastern New Hampshire and far southwest Maine (50 to 80 percent). Thus, it seems like a good bet that we will see some widespread totals in the 1 to 2 inch range with some locally higher amounts over southeast New Hampshire and/or far southwest Maine.

The upper low moves overhead on Tuesday, so we may see some lingering precipitation chances before it finally kicks out of the region Tuesday night. Mean ridging will then move in mid to late week with highs pushing back into the 70s. While this time period looks mostly dry, a quick moving front could lead to some low precipitation chances late week.

AVIATION /18Z FRIDAY THROUGH WEDNESDAY/

Through 18Z Saturday...Mainly VFR with increasing and lowering clouds. Rain chances increase tonight into Saturday morning across southern NH and toward PWM, but uncertainty remains in how quickly rain can move in (it's possible rain even holds off until even later). Ceilings may approach MVFR for MHT-CON-PSM toward the end of the TAF period but am not confident enough to introduce yet. For winds, NE wind gusts 20-25 kt likely today with a downward trend tonight before increasing again late and Saturday morning. The clouds may be thick enough to prevent fog at HIE and LEB, so it has been left out of the TAFs. NE wind gusts 20-25 kt are possible inland Saturday and then around 30 kt for coastal sites.

Outlook:

Saturday night: Areas of MVFR developing as rain moves into the area. Northeast surface gusts of 30 kt or more possible near the coast.

Sunday: Widespread MVFR likely, areas of IFR or lower possible near the coast in rain. Coastal terminals may see northeast surface gusts of 35 kt or more, especially towards PSM.

Monday: Areas of MVFR or lower during the first half of the day as rain winds down. North northeast surface gusts of 25 kt or more possible.

Tuesday: Conditions improving to VFR. A few showers may linger over the mountains.

Wednesday: VFR expected.

MARINE

Nor'easter continues to slowly move northward today and is expected to stall out and meander south of southern New England through the weekend. As a a result, the pressure gradient will steadily tighten and increase northeast winds, resulting in deteriorating conditions and gales persisting through the weekend for the nearshore and offshore waters, but times for the onset of gales have been delayed slightly based on latest guidance. For the bays, gale force gusts are possible at times, but confidence is not enough to change the Small Craft Advisory.

The nor'easter begins to lift to the northeast early next week, potentially over or near the Gulf of Maine. There are indications of a weakening trend by that point, so it's looking like a transition to SCA conditions Mon and/or Tues. High pressure brings further improvement in winds and seas toward midweek before a front approaches from the west late next week.

GYX WATCHES/WARNINGS/ADVISORIES

ME...High Surf Advisory until 8 PM EDT Sunday for MEZ023>027. Coastal Flood Advisory from 10 AM Saturday to 11 PM EDT Sunday for MEZ023. NH...High Surf Advisory until 8 PM EDT Sunday for NHZ014. Coastal Flood Advisory from 10 AM Saturday to 11 PM EDT Sunday for NHZ014. MARINE...Gale Warning from 11 AM Saturday to 8 PM EDT Sunday for ANZ150- 152. Small Craft Advisory until 8 PM EDT Sunday for ANZ151-153. Gale Warning from 2 AM Saturday to 8 PM EDT Sunday for ANZ154. Gale Warning until 8 PM EDT Sunday for ANZ180-182-184.