textproduct: Gray - Portland

WHAT HAS CHANGED

Little change to the going forecast products for the next few days. Somewhat unsettled weather continues mainly in the mountains until Monday when it looks like more rain for the rest of the forecast area.

KEY MESSAGES

1. Unsettled pattern continues over the weekend into early next week.

2. The next chance for widespread rain looks to arrive early next week, with unsettled weather continuing through midweek.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION... Upper-level low will slowly move east toward the Canadian Maritimes during the day today. Broad cyclonic flow and embedded waves stemming from this low will provide enough lift to get showers and a few storms going, mainly in the afternoon to early evening, as daytime instability builds. This will be mainly in and around the mountains, and a few storms may contain small hail.

Otherwise, it will be a breezy and partly sunny day, although there may be periods of mostly cloudy skies with steep low-level lapse rates and enough instability aloft. The steep lapse rates and good mixing will bring down stronger winds from aloft resulting in a breezy day. Based on forecast soundings, wind gusts of 25-35 mph are likely with up to 40 mph possible on the higher end. Highs will be mainly in the 70s to low 80s south of the mountains, except a bit cooler in the mountains.

Winds likely remain somewhat breezy into Friday evening but are expected to continue to ease overnight. A few showers remain possible in the mountains with upslope flow, but whatever activity develops during the day is expected to fade around sunset. Overnight lows will be mostly in the 50s, except some upper 40s are possible in the mountains.

Saturday will be breezy with NW winds 15 to 20 mph gusting up to 30 mph. Upslope near blocked flow will lead to plenty of clouds and showers along and north of the mountains while shower chances decrease south of the mountains with more in the way of sunshine. Highs will range from the low 60s north to near 80F near the coast with the aid of downsloping winds. The gradient will slacken over the area Sunday allowing for light winds turning onshore in the afternoon. A surface trough over the area combined with SB CAPE building to 1000 J/kg will allow for diurnal showers and thunderstorms to develop across much of the area Sunday. The lack of shear will likely keep any storms sub-severe while steep mid level lapse rates and low freezing levels could allow for some small hail.

Much of the same can be said for Sunday with scattered afternoon showers and possibly a few storms with cold air lingering aloft.

KEY MESSAGE 2 DESCRIPTION... Global models continue to agree that a second upper low is going to move through Ontario early next week with the attendant trough beginning to dig in to the region as well. The models have come into better agreement on timing since yesterday, with a surface low forming in the Great Lakes Region early on Monday and moving through the area Monday night. The track has become more uncertain with the Euro and Canadian ensemble camps trending the low more inland, whereas the GFS is continuing to suggest a coastal system. Regardless this looks like the next opportunity for widespread rainfall, and it could be juicy too. Ensembles are already starting to hone in on PWATs climbing into the 1.50 to 1.75" range on Monday and NBM probabilities for over an inch of rainfall are in the 50 to 60% range. We have seen plenty of rain recently, so we will have to watch how this system trends closely as it could pose a risk for localized flooding.

After the Monday system, the area remains under broad cyclonic flow, but the aforementioned upper low departs to the northeast. This should trend things drier, but also leaves the door open for afternoon showers and storms

AVIATION /00Z FRIDAY THROUGH TUESDAY/

Through Sunday...Generally VFR to MVFR at times through Sunday with diurnal showers and a few thunderstorms associated with upper level low pressure. Westerly winds gust 20 to 30 kt at times today and Saturday.

Outlook:

Monday-Tuesday: Low pressure may bring more widespread IFR and rain showers.

MARINE

SCA conditions today with gusty westerly winds. Winds are expected to drop below SCA levels tonight into Saturday, but seas may remain above 5 ft for portions of the waters.

Winds and seas diminish Saturday night and Sunday. An area of low pressure may develop near coastal New England Monday bringing the potential for at least SCAs.

GYX WATCHES/WARNINGS/ADVISORIES

ME...None. NH...None. MARINE...Small Craft Advisory until 8 PM EDT Friday for ANZ150-152. Small Craft Advisory until noon EDT Friday for ANZ151-154.