textproduct: Gray - Portland

WHAT HAS CHANGED

Little change to the going forecast at this time for this evening and overnight.

KEY MESSAGES

1. Dry and warmer weather this evening. Cooler weather arrives on Thursday, with some showers and perhaps a thunderstorm.

2. Soaking rainfall and high elevation snow late Friday through Saturday. Hikers should prepare for winter conditions above 3000 feet.

3. Unsettled pattern persists into next week.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

A cold front moves across the area today, allowing for warmer temperatures ahead of it's passage. These warmer temperatures will start to come down through the afternoon as peak heating wanes and cold air advects into the area behind the cold front. The front should not bring precipitation to the area.

Thursday will feel noticeably colder than today. Low pressure that brought the aforementioned cold front today will move southward. This will allow for some weak forcing to setup across the seacoast and coastal plain. With clearer skies in the morning bringing diurnal heating, there will be the potential for a few pulse thunderstorms to develop over the region. Hi-res guidance is surprisingly confident in the storm environment, with both the NAMnest and HRRR indicating an environment with around 200-400J of CAPE and some decent shear. The inverted-V forecast soundings suggest that a few gusty winds can't be ruled out from storms that develop but generally this setup is not very conducive for impactful severe weather. Isolated showers are likely elsewhere Thursday afternoon.

KEY MESSAGE 2 DESCRIPTION...

Models remain in good agreement in a compact upper low diving southeast across northern New England Friday night through Saturday with a surface low developing in the Gulf of Maine. A notable trend amongst available deterministic and ensemble guidance has been for a faster system with the bulk of precipitation occuring Friday night into Saturday morning.

Friday will start off mostly dry with clouds and shower chances increasing through the day as the upper low approaches from the northwest. Highs will range from the 50s north to 60s south with rain likely by sunset. The upper low will cross close to overhead Friday night bringing a cold rain across much of the area. This upper low will bring anomalously cold air aloft with 850 mb temps dropping as low -4C. BUFKIT profiles show wet bulb zero heights may fall as low as 2000 feet early Saturday morning while the NBM shows snow levels as low as 3000 feet. While there remains some variability in the location of the coldest air aloft, it remains likely that the highest peaks will see some accumulating snow with winter conditions possible above 3000 feet centered on Friday night into Saturday morning. At lower elevations a cold rain is expected Friday night into Saturday morning with the latest NBM carrying 90 percent PoPs Friday night with PoPs decreasing to 20-40 percent Saturday evening. An axis of rainfall to around 1-2 inches is likely, although the placement of this axis shows some variability with going forecast aligning it from the mountains to the Mid Coast. Rainfall amounts decrease to the southwest, although this could change if the axis of greatest rainfall shifts. Low pressure forming in the Gulf of Maine will also bring raw northeast winds gusting 25 to 35 mph along the coastal plain with higher gusts along the immediate coast.

The faster progression of the system leaves some room for improving conditions from NW to SE Saturday afternoon. Nevertheless it will be a cool day with highs mainly in the 50s with the summit of Mt Washington staying below freezing.

KEY MESSAGE 3 DESCRIPTION...

As one upper level low exits Saturday another short wave will drop south through eastern Canada Sunday. High pressure nudging in from the west ahead of this wave may allow for more in the way of sun Sunday morning and moderating temperatures. The approaching wave will bring increasing chances for showers Sunday afternoon with widespread chances for showers persisting through Monday. Ensembles suggest trough over the Northeast will persist into Tuesday with a faint signal for a pattern change around the middle of next week.

AVIATION /00Z THURSDAY THROUGH MONDAY/

VFR is expected through Thursday morning. Showers and a few thunderstorms Thursday afternoon may allow for flight restrictions, especially at PWM and PSM. MVFR and VFR CIGs are likely elsewhere with isolated showers across the area Thursday evening.

Outlook:

Friday: Mainly VFR. Lowering cigs and showers likely bring a trend towards MVFR from NW to SE Friday afternoon.

Friday night-Saturday: Widespread rain and low cigs likely bring at least IFR. Some improvement from NW to SE Saturday afternoon. NE winds gust up to 25 kts along the coastal plain.

Saturday night-Sunday: Mainly VFR.

Sunday night-Monday: Showers bring potential for restrictions.

MARINE

Winds will slacken this evening and generally become northerlies. Light and variable winds will persist through Friday morning, with seas ranging from 2-4ft.

Low pressure crosses northern New England Friday night into the Gulf of Maine Saturday. Strengthening northeast winds will bring potential Gales through the day Saturday and seas quickly building 6-9 feet. Winds shift northerly Saturday night and gradually drop below 25 kts while seas remain elevated through Sunday. Winds and seas likely drop below SCA thresholds Sunday night into Monday.

GYX WATCHES/WARNINGS/ADVISORIES

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