textproduct: Gray - Portland

WHAT HAS CHANGED

No significant changes were needed to the forecast.

KEY MESSAGES

1. Dry weather continues into Saturday but with less wind and slightly warmer temperatures.

2. Unsettled weather makes a return toward the middle of next week after a dry start.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

Latest satellite imagery is fairly similar to what was seen yesterday...partly cloudy in much of NH (except northern and toward the Seacoast) and mostly cloudy farther east into western ME where there is small amount of CAPE and more moisture in the 5000-7000ft AGL layer with being in closer to proximity to the upper low centered to the east. These mostly cloudy areas may see some sprinkles or light showers, especially toward the Kennebec Valley and Midcoast, but there is a lot of dry air in the low levels to overcome. Northerly winds will continue to gust to around 20-25 mph this afternoon, which should hold off the seabreeze, except south of Portland and toward the Seacoast. Winds and clouds will diminish this evening and tonight with more in the way of radiational cooling overnight as winds will be lighter overall. I've gone a bit cooler than the NBM for lows with more readings in the 20s away from the coast (except southern NH where more clouds could linger), and it's possible some of the northern valleys reach the upper teens.

Saturday will be dry and with much lighter winds as broad high pressure builds overhead, creating a weak pressure gradient. Temperatures are expected to be a few degrees warmer than today with most in mid to upper the 50s, possibly around 60 degrees in parts of southern NH. However, with the weak pressure gradient, the seabreeze should be able to move inland to cool things off a bit at and just inland from the coast in the afternoon. An area of low pressure passing to our south and west is not expected to bring any precipitation to the area, but will bring increasing mid and high clouds across southern NH in the afternoon.

Saturday night doesn't look as cool due to the increase in cloud cover from the passing low to the south. Most will see lows in the 30s, although northern areas still may see 20s with less clouds expected.

KEY MESSAGE 2 DESCRIPTION...

Model guidance continues to suggest a dry to start to the week as high pressure begins to settle over New England on Sunday behind a departing upper low. There is growing confidence that this drier weather lasts through the day Tuesday as since yesterday ensemble means have trended toward a Rex Block lasting into midweek, with high pressure deepening over the Canadian Maritimes suppressing low pressure developing off the Mid- Atlantic coast. The only fly in the ointment would be an inverted trough forming, which some models have hinted at, that would bring some showers to the coast Monday night. However, recent runs have been showing an increasingly more amplified surface ridge stretching into New England, so I am not putting too much weight on this solution. Uncertainty in the low track is still high as the GFS and Canadian camps break down the ridge faster, bringing it north faster. This starts precipitation chances Tuesday night. The Euro camp has high pressure staving it off for an additional 24 hours, until Wednesday night. The important take away here is that the ensemble signal is solid, so expect rain around midweek, but timing still needs to be nailed down. QPF is the next area of uncertainty with ensemble spreads among the global models being high due to that uncertain track, but it is worth noting that some increasingly juicier members have been popping up. For right now though the NBM 75th percentile is around a half inch and the 25th percentile is...nothing at all, so it is very much a wait and see situation. Beyond this the pattern remains unsettled with a deeper upper trough digging into the area late in the week as a series of fronts take aim at the region. It's too early to speculate on how exactly that plays out, but I have no problem with the broad brush shower chances through Friday to cover the uncertainty.

AVIATION /18Z FRIDAY THROUGH WEDNESDAY/

Through 18Z Saturday...VFR expected. Can't rule out a couple of brief light showers or sprinkles near AUG/RKD this afternoon, but chances are too low for TAF inclusion. Northerly wind gusts around 20kt likely through this afternoon with winds turning onshore at PSM with a seabreeze. Winds will become light this evening and continue to be light through Saturday. A seabreeze is likely for coastal terminals (with gusts to around 15 kt possible) by late Saturday morning or early afternoon and may make it inland toward CON and AUG later in the afternoon.

Outlook:

Rest of Saturday - Saturay night: Prevailing VFR. Sunday-Monday: Generally VFR conditions expected with no significant weather.

Tuesday-Friday: Generally VFR, but MVFR possible with shower activity. Coverage of any showers next week is highly uncertain at this time.

MARINE

Through Saturday night...Winds and seas continue to remain below SCA levels with broad high pressure stretching from eastern Canada into the Northeastern US. Winds become more onshore closer across portions of the coastal waters this afternoon and then become north to northeast overnight. The seabreeze develops late Saturday morning or early afternoon with winds become south to southwesterly later in the afternoon and then more west to northwest Saturday night.

Wind gusts look to remain below 25 knots through at least the the day next Friday, but confidence is increasing in wave heights (around 5-8 ft) through the middle of next week as low pressure enters the Gulf of Maine.

GYX WATCHES/WARNINGS/ADVISORIES

ME...None. NH...None. MARINE...None.