textproduct: Gray - Portland

WHAT HAS CHANGED

The Wind Advisory will be allowed to expire on time at 9AM this morning.

KEY MESSAGES

1. Rain ends early this morning with gusty southerly winds becoming westerly and falling temperatures through the day.

2. Several chances for precipitation exist Thursday into early next week as we remain in an active pattern. Ensemble data doesn't suggest anything impactful at this time.

DISCUSSION

Rain will end early this morning from west to east as low pressure crossing near Hudson Bay sends a trailing cold front across the Northeast. A few damaging wind gusts possible with front. A few localized river forecast points may approach minor flood stage due to residual runoff but overall impacts will be minimal given the ongoing drought conditions. For more information, please see the hydrology section below.

Winds will become westerly behind this front with gusts up to 30-35 mph. After a warm start to the day, temperatures will quickly fall into the 30s and they will remain primarily into the 30s throughout the daytime hours. This will make for blustery conditions with wind chills primarily into the teens and 20s.

A secondary cold front combined with the cold pool aloft may allow for a few scattered snow flurries or snow showers, especially during the afternoon into the early evening hours. Cold temperatures will prevail tonight with forecast lows into the single digits across the north with teens south. Wind chills will be into the single digits either side of zero.

KEY MESSAGE 2 DESCRIPTION... The 500 mb pattern through the extended forecast period is mean troughing over the northeast with a few shortwaves rotating through into early next week. High pressure crosses the area Wednesday with temperatures running slightly below normal as highs only climb into the low to mid-30s south of the mountains, and into the 20s to the north behind the cold front. Southwest flow kicks in Wednesday night and while Thursday morning will be chilly, this will ultimately help temperatures moderate with much of the area seeing high temperatures back in the 40s. Low pressure passes just to the north Thursday night with an accompanying 500 mb shortwave. Ensembles suggest this could result in some light snow showers with accumulations a coating to maybe a half inch, with those high totals confined to the mountains.

A secondary shortwave crosses Friday which may help to sustain showers for part of the day, but temperatures warm above freezing early on so light rain would become the dominant precipitation type outside of the highest peaks. Global models begin to diverge on exact solutions for the weekend, but ensembles are in good agreement that shortwaves continue to rotate though the broader trough and this corresponds with a double barrel cold front sagging south into our area. Based on this I think it is fine to roll with the NBMs chance of showers through the weekend, but precipitation amounts and exactly how widespread it actually ends up being is going to be something that gets refined as we get closer in time as it depends on the currently uncertain low pressure tracks. A deeper trough crosses Monday, but solutions are even more spread out on surface features at this point. The NBM is favoring the solutions that bring high pressure into the region, but some solutions have significant low pressure centers nearby so this active pattern will have to continue to be monitored closely.

AVIATION /12Z TUESDAY THROUGH SATURDAY/

Through 12Z Wednesday: Conditions continue to improve early this morning with gusty west to southwest winds behind a cold front. In general, looking at gusts 25-30 kt through much of the day and into early tonight, but can't rule out a brief period of gusts in the the 35-40kt through 14Z or so this morning. Mainly VFR conditions will then prevail through tonight with a low chance for a scattered SHSN bringing brief restrictions this afternoon.

Outlook...

Wednesday: VFR conditions expected.

Thursday: VFR expected through the day with ceilings trending toward MVFR during the evening. Thursday night could feature light snow showers which may bring about locally lower restrictions.

Friday: Snow showers transition to rain showers with ceilings generally VFR outside of precipitation.

Friday night through Saturday: Light rain and/or snow showers can't be ruled out which would bring some MVFR conditions, but VFR would be expected otherwise.

MARINE

Gale force westerly winds will persist behind a cold front for most of the day today. Seas outside of the bays between 9-18 ft can be expected today with gradual declines in wave heights through tonight. Across the bays, seas will be between 2-5 ft.

Wind gusts fall below 25 knots Wednesday morning, but waves are going to be slower to settle and even when they do Wednesday night it may be in the 5 to 6 ft range where they may sit through at least early next week as an active pattern keeps things churned up. Similarly, wind gusts greater than 25 knots return Friday night lasting through at least Monday with some suggestion in periods of gales as well, but that will depend on the tracks of low pressure systems during this time.

HYDROLOGY

The Flood Watch remains in effect for possible localized minor river flooding due to lingering runoff from rainfall and mountain snow melt. In addition, while many southern rivers are ice-free, some ice remains in the mountains and northern basins. There remains a non-zero risk for mechanical break-up and unpredictable jams as flows increase.

GYX WATCHES/WARNINGS/ADVISORIES

ME...Flood Watch until 2 PM EDT this afternoon for MEZ007>009- 012>014. NH...Flood Watch until 2 PM EDT this afternoon for NHZ001>006. MARINE...Gale Warning until midnight EDT tonight for ANZ150>152-154. Small Craft Advisory until 11 PM EDT Wednesday for ANZ153.