textproduct: Gray - Portland

SYNOPSIS

A weak front draped through the area may bring scattered snow showers but otherwise quiet weather is expected until late Thursday. That will be when southerly winds begin to increase. Winds will continue to ramp up through Friday and gusts may be 40 to 50 mph or more at times, especially near the coast. Temperatures will also be quite warm, with readings approaching the 50s for many areas. This means that almost entirely rain is expected along and ahead of the cold front. At this time it does not look like enough rain and snowmelt to cause any significant flooding concerns. The front crosses the area Friday night and temperatures will fall into the 20s by morning. Another chance for precipitation arrives late Saturday or early Sunday, this time in the form of light snow or snow showers.

NEAR TERM /UNTIL 6 PM WEDNESDAY/

The gradual moderating trend will continue today with high temperatures into the 30s to lower 40s from north to south. A passing cold front may bring scattered snow showers to the mtns and towards the Canadian Border but otherwise it will be another dry day.

SHORT TERM /6 PM WEDNESDAY THROUGH FRIDAY/

Key Messages:

-Tranquil weather through Thursday with little to no weather related impacts.

-Rain with strong to possibly locally damaging winds late Thursday night through Friday.

-Minor nuisance flooding possible along with river rises and river ice breakup.

Discussion: Mainly clear skies are expected tonight with low temperatures falling into the teens and 20s. Mid-lvl ridging will remain over New England on Thursday, allowing for another dry day with high temperatures mostly into the 40s.

Clouds will then increase on Thursday night with widespread rain moving in after midnight as an area of low pressure moves across Quebec, sending a sfc warm front northward across the region. This will allow for a non-diurnal temperature trend overnight with readings warming into the 40s/lower 50s by dawn on Friday. Periods of moderate to locally heavy rain will then persist through Friday morning as we sit within the warm sector before a sharp cold front crosses during the afternoon and evening. Latest ensemble means suggest most locations should receive between 0.50"-1.00" of rainfall, with locally higher amounts likely... especially in the SE facing terrain. This rain combined with anticipated snow melt will likely result in river rises and perhaps some ice breakup but other than some minor nuisance flooding from clogged storm drains/low spots, no significant flooding is expected.

Strong to perhaps locally damaging winds is the main thing to watch with this system as a stout S-SE LLJ arrives near the triple point. There is the potential for gusts between 50-60 mph across portions of the Mid-Coast with 40-50 mph elsewhere. Convective elements are possible as the cold front crosses, which would also be capable of producing locally stronger winds. Given this potential, went ahead and issued a High Wind Watch for Knox, Lincoln, and coastal Waldo counties as this is where current guidance suggests the greatest potential is for locally damaging winds.

LONG TERM /FRIDAY NIGHT THROUGH MONDAY/

Key Message: A return to near to below normal temps is expected this weekend into next week. There will be frequent chances for precip...but on the lighter side.

Impacts: Westerly winds Sat have the potential to gust up to 40 mph or higher. Some light snow is possible Sun with a passing warm front.

Forecast Details: Fri night temps will continue to steadily fall behind the cold front...with the vast majority of the forecast area expected to be below freezing by sunrise. If we can clear out that may help freeze up any standing water and lead to some icy spots...but it will also be increasingly gusty behind the front and that will help to speed up the evaporation. Either way something to keep an eye on...but thankfully going into a weekend and less traveling expected in the morning.

That cold advection Sat will increase mixing depths while low to mid level westerly winds around 30 to 40 kt continue at the top of the boundary layer. I anticipate that at least for the first half of the day it will stay gusty. The NBM winds/gusts seem a little too low...so my preference is to blend in some 75th or 90th percentile NBM to bring them up.

A brief ridge crosses the region Sat...with the next wave arriving early Sun. Warm advection thru the mid levels will cross the forecast area thru midday Sun. There is lift and saturation in the snow growth zone...but it will have to overcome some pretty dry near surface air. Either way a chance of snow...tending towards likely in the higher terrain...seems fair at this range.

No significant changes were made from the NBM forecast besides the increase in winds/gusts early Sat.

AVIATION /06Z WEDNESDAY THROUGH SUNDAY/

Short Term...VFR conditions are expected through Thursday, with a period of MVFR ceilings possible this afternoon for LEB/HIE. 35-40kt LLWS this morning for most terminals until daytime mixing begins after 13/14z. Another period of LLWS possible this afternoon and evening once mixing subsides with weak sfc inversion again developing. Winds will become S on Thu with widespread RA moving in after midnight along with lowering ceilings. Gusty S-SE winds are then likely on Fri with gusts up to 45-50 kts possible, especially near the coast. RA and low ceilings will also persist.

Long Term...Conditions return to VFR Sat...with MVFR CIGs hanging on a little longer in the mtns around HIE. Westerly surface gusts of 30 kt are possible early Sat before surface ridge axis allows them to diminish in the afternoon. There may be some light snow late Sat night/early Sun but that is fairly low confidence at this time due to dry surface air.

MARINE

Short Term...Gale force SW winds are expected through this evening for all waters except Casco Bay where gusts should remain below 35 kts. Seas will be at 6-9 ft outside of the bays with 1-4 ft in the bays. Storm force S winds are then possible late Thu night through Fri along with rain.

Long Term...Winds will continue to gradually shift from southwesterly to west northwesterly thru Sat and gales will continue for all waters thru sunrise. Winds and seas continue to diminish into the afternoon...but seas will remain above 5 ft outside of the bays thru most of the period. Another round of southwesterly winds will bring wind gusts back to SCA thresholds outside the bays Sun and remain gusty Mon.

GYX WATCHES/WARNINGS/ADVISORIES

ME...High Wind Watch from Friday morning through Friday evening for MEZ026>028. NH...None. MARINE...Gale Warning until midnight EST Wednesday night for ANZ150>152- 154. Small Craft Advisory until midnight EST Wednesday night for ANZ153.