textproduct: Gray - Portland

WHAT HAS CHANGED

No significant changes with this forecast package.

KEY MESSAGES

1. Fair weather expected through the weekend, then a strong cold front moves through on Monday.

2. A polar air mass arrives behind a strong cold front early next week. Many locations south of the mountains may see their first hard freeze.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

After some early morning fog, today should be sunny. Highs will be around 60 far interior and near 70 across the lower elevations of NH and the ME coastal plain.

Clear and calm tonight with lows in the 30s to lower 40s. At this time it does not look like it will get cold enough to require frost headlines where the program is still active.

High pressure exits the region on Sunday as an upper level trough swings in from the Great Lakes Region. Clouds are going to build in early which is going to keep afternoon temperatures in the low to mid-60s. These clouds are also going to make for a more mild night as temperatures only fall into the low to mid 40s.

A strong cold front crosses on Monday and it continues to look like it is going to be mostly dry except for a few showers, especially in the north. The bigger theme will be wind as the pressure gradient tightens markedly with and behind the front for Monday afternoon. Forecast soundings support gusts of 25 to 35 MPH, possible higher if low level mixing is maximized.

KEY MESSAGE 2 DESCRIPTION...

The real cool down arrives by Tuesday morning. Very likely the coldest weather since the spring Tuesday-Wednesday with 850 mb temperatures plunging to between 0 and -7C by Tuesday morning depending on model of choice. Even 925 mb temperatures are near or slightly below freezing on guidance. As such, even modest radiational cooling would suggest a widespread freeze Tuesday morning. However this is contingent on the boundary layer decoupling, and guidance is currently indicating 40-50+ kts at 850 mb driven by a strong pressure gradient, so would say the temperature forecast here is not yet high confidence. Right now the best odds for below freezing minimums will be in the higher terrain in the interior, with lows in the upper 30s-low 40s closer to the coastal plain.

Won't take much mixing on Tuesday to tap the stronger winds aloft, so can expect a blustery day with sustained winds of 10-20 mph through the day. Even with full mixing highs will only reach the 40s in the mountains with 55-60 on the coastal plain. Winter clothing may not be a bad choice especially if heading out early in the day.

Dry and sunny conditions should last through Wednesday with high pressure cresting overhead. While 850 mb temps won't be quite as cold Wed morning, much greater radiational cooling is likely as winds slack. It is likely a larger swath of western ME and southern/central NH see their first hard freeze of the fall, especially in any valleys/typical cold spots away from the immediate coast.

Fair weather should continue Wednesday with highs primarily in the mid 50s-low 60s. The next chance for precipitation does not arrive until Wednesday night-Thursday.

AVIATION /07Z SATURDAY THROUGH WEDNESDAY/

Widespread VFR conditions today through Sunday. Patchy valley fog brings local LIFR to LEB and HIE through mid morning today, with fog then possible again tonight.

Outlook...

Monday: Generally VFR with some brief MVFR restrictions possible in light rain and/or snow in the mountains. Westerly gusts around 30 KT Monday afternoon and evening.

Tuesday-Wednesday: VFR prevails once again as high pressure builds back into the region.

MARINE

Generally sub-SCA conditions are expected today through Sunday. However, a strong cold front crosses the waters Monday afternoon and may elevate seas and wind gusts to SCA criteria.

GYX WATCHES/WARNINGS/ADVISORIES

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