textproduct: Gray - Portland

WHAT HAS CHANGED

Overall no significant changes in the forecast with this update as guidance remains locked in with the overall pattern evolution. Still not seeing any major weather makers over the next week.

KEY MESSAGES

1. A meandering frontal boundary will bring periods of mountain snow showers and coastal rain showers from tonight through early Friday morning. No significant travel impacts are expected.

2. After temperatures retreat Friday, Friday night and Saturday night will see temperatures fall well below normal areawide. Values will be 10-15 degrees cooler than Thursday night, with teens to lower 20s along the coast and interior, and single digits across the northern valleys and foothills.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION... A warm front will push north tonight running into a cold airmass. This will aid in the development of light precipitation, especially across the north. Initially it should be in the form of light snow which may allow for some slippery spots for the early morning commute Thursday morning north of Rt 2, but any showers that do . Thereafter, temperatures will quickly warm, with highs around 60 expected across the south with 40s and 50s elsewhere. In addition breezy conditions are expected as 925mb winds increase to 40kts. The warm weather will be short lived as the stalled front across Northern Maine drifts further south again tomorrow evening as a shortwave trough pushes through the Northeast. Rain chances will increase by late Thursday afternoon into the evening as a weak surface low pressure system rides along the frontal boundary. This wave will bring more widespread rain through Thursday night, especially across southern areas. Enough cold air could work into the northern edge of the precipitation shield by early Friday morning, to turn the rain back to a wet snow for a few hours before the system pulls off to the east early Friday morning. Due to the previous warmth and rain, there will be limited accumulations. Temperatures will most likely flat line on Friday as strong Cold Air Advection brings an unseasonable cold air mass into the area along with very dry air. Roads will quickly dry off, so black ice will not be an issue.

KEY MESSAGE 2 DESCRIPTION... Anticyclonic flow around high pressure moving into the Central Plains Friday evening will continue cool NW CAA into the forecast area Friday night - Sat night. The advected airmass will be responsible for near record low 850mb temperatures across Newfoundland and Labrador. While these values remain well north of the forecast area, the area will still experience much lower temperatures due to proximity, some 10-15 degrees below prior nights at the surface.

Expect some clouds and breeze to continue overnight, so decoupling will be challenging. This should limit additional radiational cooling dragging temperatures down. All in all, lows Fri night look to fall into the single digits across the northern mtns/valleys, with teens to low 20s along the ME coast/interior and southern NH.

Coldest part of the airmass will have pushed east by Saturday night, but lighter winds bring the prospect of a second well below normal night.

The large high will push off the Mid-Atlantic coast Sunday night with return flow providing some moisture for the chance of light precip to affect portions of the forecast area. There really isn't a good, reliable signal at this time other than some showers.

The extended forecast then features two systems to follow. One is a quick moving low to the north with precip extended south along a cold front. For now, southern Maine and northern NH see the best chance for precip from this system, as there is uncertainty how far south good forcing reaches. By mid to late week, New England will be in an active pattern as multiple lows pass through the Plains and towards the Great Lakes. This should result in a warming and moistening airmass for much of New England, with the chance for either multiple rounds or a longer period of precipitation for the area.

AVIATION /18Z WEDNESDAY THROUGH MONDAY/

VFR conditions through midnight before ceilings begin to drop as a lower stratus field associated with a warm front moves across the region. MVFR ceilings will be widespread with possible IFR to LIFR across northern TAF terminals, especially KHIE, KAUG and KRKD. Ceilings will lift during the day on Thursday becoming VFR again, before lowering again as the next round of rain moves in later Thursday. This time lower ceilings are expected across Southern TAF sites through Thursday night.

Outlook...

Friday and Friday Night: VFR with NW winds gusting 15-20 kts, becoming 5-10 kts overnight.

Saturday and Saturday Night: VFR with no sig wx.

Sunday: VFR. Low confidence of some passing SHRASN across the mtns/CAN/US border, may bring MVFR cigs. SE winds gusting 15-20 kts.

Sunday Night and Monday: Clouds begin to thicken and lower with chance of RA/SN for northern terminals, and RA to the south Monday.

MARINE

Active weather pattern will bring periods of SCA conditions straight through the weekend with wind shifts from the southwest to northwest begins common through the period. First period of SCA conditions will being tonight as a warm front pushes north across the coastal waters. Winds will turn northwest by Thursday night as a cold front pushes south. This will keep waves above criteria straight into Friday.

High pressure moving towards the Mid-Atlantic and exiting east this weekend will bring a gradual decrease in wave heights under NW flow. The cooler temperatures do increase the chance of some offshore zones seeing gusts to 25 kts late this weekend into Monday.

GYX WATCHES/WARNINGS/ADVISORIES

ME...None. NH...None. MARINE...Small Craft Advisory from 10 PM this evening to 2 PM EDT Friday for ANZ150>154.