textproduct: Gray - Portland

WHAT HAS CHANGED

No significant changes to the forecast with this update. Confidence is increasing in a transition to a more active weather pattern late this week.

KEY MESSAGES

1. Temperatures will average above normal through the middle of the week with mostly dry weather. There is increasing confidence for appreciable precipitation late this week.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION... High pressure to our south moves offshore tonight with resulting southwesterly flow warming dewpoints and making for a warmer night than last as temperatures only bottom out in the mid to upper 30s. Valley locations stand the best chance of seeing temps near or slightly below freezing. The high only slowly moves eastward on Monday, so continued southwesterly flow is going to allow temperatures to climb into the mid to upper 60s south of the mountains with 70F possible in the normally warmer southern valleys. Meanwhile at the 500mb level northwesterly flow and shortwave troughing will add some clouds and showers into the mix for the mountains, and temperatures likely only climb into the upper 50s and low 60s as a result.

Tuesday stands to be a few degrees cooler across Maine and eastern New Hampshire as additional high pressure building over eastern Canada pushes a weak back door cold front through the area. This may bring some showers along with it as it slowly sinks southward through Tuesday night, but nothing of much substance, and with plenty of dry air in place over southern Maine and New Hampshire it is likely they stay dry. The best chance for showers looks to be in Northern New Hampshire and the Western Maine Mountains with QPF only expected to range from a few hundredths to around a tenth of an inch. Any shower activity quickly comes to an end by Wednesday morning as the front lifts back north. Ridging aloft then continues above normal temperatures and mostly dry weather through Thursday night.

The is a growing signal for appreciable rain late week as global models are showing a much better consensus and more ensemble members are wetter as well. While there is still plenty of uncertainty surrounding the details, it is looking more like many locations may see their first measurable rain since mid- October.

AVIATION /18Z SUNDAY THROUGH FRIDAY/

Through 18Z Monday: VFR conditions prevail through tonight with showers possible around the higher terrain along the International Border.

Outlook... Monday night: Mainly VFR conditions with upslope showers around the mountains.

Tuesday-Tuesday night: MVFR ceilings possible, especially in the mountains. More widespread showers possible.

Wednesday: VFR conditions expected.

Thursday-Friday: MVFR ceilings and rain looking more likely.

MARINE

Sub-SCA conditions look to prevail through at least Thursday as high pressure settles over the waters. There is increasing confidence in SCA conditions late week as we transition into a more active weather pattern.

GYX WATCHES/WARNINGS/ADVISORIES

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