textproduct: Gray - Portland

WHAT HAS CHANGED

Little change to the going forecast for this early Monday morning package.

KEY MESSAGES

1. A few minor weather systems may bring some scattered showery weather today through Wednesday, mostly in the mountains. Otherwise, temperatures will be near normal.

2. There is a growing signal for a system to bring rain and measurable snow to the area late this week, although significant uncertainty in potential impacts remains.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

A series of relatively weak short wave troughs will move through the mean westerly flow aloft through Wednesday. The result will be scattered showers (with some snowflakes in the higher terrain) from time to time but no washouts. However, with the colder air aloft the skies will average mostly cloudy, especially in the mountains. NW winds will be a bit breezy today with gusts 20 to 25 MPH at times. Daytime temperatures over the next few days will actually average out a little above normal.

KEY MESSAGE 2 DESCRIPTION...

A deep trof axis will move across the Great Lakes on Thursday as a sfc low develops near the OH or TN Valley and then swings offshore of the U.S. East Coast Thursday night into Friday. This system is then progged to move northeastward Friday night into Saturday while deepening and becoming closed off. Forecast uncertainty in the ultimate track of this area of low pressure remains high, with some model runs bringing it inland over New England while other guidance keeps the low well to the SE of Cape Cod. The last several runs of the deterministic GFS have been a bit of an outlier with showing a more inland track, as low center clustering from the EPS, GEFS, and most AI guidance keeps the low offshore... and in some cases so offshore we that impacts would be little to none.

Given this uncertainty, don't see any reason to deviate from the NBM as it shows a reasonable middle ground approach. As is often the case, should snow occur the most likely locations would be across the mtns and towards the Canadian Border. Gusty winds and rain are possible elsewhere. Of higher confidence is for cooler temperatures to arrive late week into the upcoming weekend as the deep trof settles over New England.

AVIATION /01Z MONDAY THROUGH FRIDAY/

Through Tuesday Morning: Upslope showers will allow for MVFR CIGs to prevailing the mountains and by HIE. Outside of the mountains, conditions should be VFR through the day, with westerly winds during the day. A few gusts could exceed 20kts. Winds calm tonight with VFR continuing through at least Tuesday morning. Upslope flow keeps MVFR in place in HIE tonight.

Outlook:

Tuesday/Tuesday Night: MVFR-IFR restrictions are possible at HIE with SHRA/SHSN but otherwise mainly VFR conditions likely. WSW wind gusts up to 25 kts possible. Moderate forecast confidence.

Wednesday/ Wednesday Night: Some lingering restrictions possible at HIE with isolated SHRA/SHSN but otherwise VFR conditions likely. WNW wind gusts up to 20 kts possible. Moderate forecast confidence.

Thursday/Thursday Night: VFR conditions likely through the afternoon before developing RA and lowering ceilings bring an increased risk for restrictions late day into Thursday night. Generally N winds of 5-15 kts. Low forecast confidence.

Friday/Friday Night: Lingering restrictions possible due to RA and low ceilings. Gusty NNE winds possible, especially along the coast. Low forecast confidence.

Saturday/Saturday Night: Some restrictions possible due to lingering RA and low ceilings. Low forecast confidence.

MARINE

Conditions during the day today should remain below SCA thresholds. Tonight, in a burst of cold air advection wind gusts may reach 25 KT for a time, but as of right now we are forecasting the majority of the time to remain just under. Calmer winds are expected Tuesday and Wednesday.

There is moderate confidence for an area of low pressure to move offshore of the Mid-Atlantic coast late week before moving northeastward through this weekend. While there remains considerable uncertainty in the track of this coastal low, increased winds and seas are likely.

GYX WATCHES/WARNINGS/ADVISORIES

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