textproduct: Gray - Portland

SYNOPSIS

Another shot of cold air builds into the region today along with gusty winds. A weak disturbance may bring a few snow showers to the mountains on Wednesday. Temperatures will warm above normal the second half of the week as an area of low pressure tracks northwest of New England, bringing widespread rainfall. Colder air will return behind this system.

NEAR TERM /UNTIL 6 PM THIS EVENING/

A cold and blustery day is expected today as an H5 s/wv trof axis swings overhead while a sfc ridge arrives from the west. Temperatures will be below avg with T8s around -17C. This will limit high temperatures to the teens across the north with lower to middle 20s south. Gusty northwesterly winds are expected with gusts between 25-30 mph likely. This will keep windchill values to within a few degrees either side of zero. The upslope flow will also result in clouds across the north and mtns with some light snow/flurries likely.

SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/

The surface ridge will crest overhead tonight, allowing for decreasing winds. This combined with at least some clear periods, and the snow on the ground will result in radiational cooling with lows falling into the single digits.

Other than some snow showers across the mtns and towards the Canadian Border, another dry day is expected on Tuesday as ridging remains. High temperatures will be on avg 5-10 degrees warmer than Monday as WAA aloft begins.

LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/

Key Message: After a cold start to the month by midweek it looks like we will have our first chance for widespread above normal temps since Thanksgiving. That will come with rain...though amounts do not seem like enough to cause any significant flooding concerns.

Impacts: Will have to watch low pressure track and whether a more inland route could bring gusty winds to the coast. Otherwise snow melt/runoff will be the biggest thing to watch.

Forecast Details: Starting midweek deep southwesterly flow will set up over the area. The incoming warmth will bring temps above normal for the forecast area...many for the first time in at least two weeks. Ensemble guidance is seasonably strong southerly flow...so it may be hard to avoid the warm air at this point. The question will be just how warm. Southwest winds are notoriously sketchy...but the lack of a strong...anchoring high to the north suggests that the warmer solutions may be more likely than not. The NBM hourly temps looked fine for this range of the forecast...but the min temps especially seemed too cool. I opted to pick the coldest hourly temps out for the low temps instead...which did bring them up significantly. In most cases that is at or above freezing overnight.

With this occurring over a couple days that should ripen up the snow...especially as dewpoints climb into the upper 30s and rain showers move in Thu night. Between the dewpoints...winds...and rainfall amounts that will determine whether any snow is left by the weekend south of the mtns.

Using DESI cluster analysis the majority of members were at or below the ensemble mean QPF. However there are 30 to 40 percent of members that are close to 1 inch mean QPF...generally a result of stronger downstream ridging. That will be the primary modeling trend to watch over the coming days.

AVIATION /12Z MONDAY THROUGH FRIDAY/

Short Term...VFR conditions are expected through the period, tho HIE and terminals in the mountains may experience MVFR ceilings and vis with light SN at times today. Gusty NW winds are expected with gusts between 25-30 kts possible. Winds will ease tonight before becoming SW on Tuesday at 10-15 kts. No LLWS is currently anticipated.

Long Term...VFR conditions Wed are expected to give way to widespread IFR or lower by Thu. Given the forecast of warmer/moist air surging north over the cold snowpack...low CIGs and areas of fog are possible. Winds should remain largely unidirectional...but a strong southwesterly LLJ will be in place by Thu...so any change in surface wind direction will result in LLWS. VFR conditions return for the weekend.

MARINE

Short Term...Gale force NW winds are expected today across the outer waters with gusts up to 40 kts with seas of 4-7 ft. Across the bays, NW wind gusts up to 30 kts are likely with seas of 2-4 ft. Winds and seas will ease tonight before becoming SW on Tuesday at 10-15 kts. Light freezing spray is possible.

Long Term...Ongoing SCA conditions or possible gales are expected Wed as the southwesterly winds start to increase. By Thu gales become more likely...and there is a low chance for some storm force gusts in the stronger storm system scenarios. In addition warm/moist air moving over colder nearshore waters may lead to areas of fog developing...though confidence is low at this time. While high pressure will build across the waters for Sat...another cold front approaches Sun so winds will generally remain gusty over the waters for the foreseeable future.

GYX WATCHES/WARNINGS/ADVISORIES

ME...None. NH...None. MARINE...Gale Warning until 1 PM EST this afternoon for ANZ150-152-154. Small Craft Advisory until 3 PM EST this afternoon for ANZ151- 153.