textproduct: Gray - Portland

SYNOPSIS

A warm front will lift into New England tonight bringing a period of snow to a wintry mix that will change to rain Thursday. High pressure builds in Friday for fair weather. Low pressure tracking into the St Lawrence Valley will bring another round of wintry precipitation changing to rain late Saturday into Sunday. Additional waves of low pressure will track along a frontal boundary that will be near southern New England early next week.

NEAR TERM /THROUGH THURSDAY/

1130 PM Update... Minor changes to reflect latest observational trends. Mixed wintry precipitation is being reported at this hour across southern NH with some light snow now beginning further to the north and east. The theme for the overnight will be for a transition to a wintry mix with slippery travel conditions possible before a changeover to plain rain for most locations south of the foothills by early Thursday morning.

Previously... 615 PM Update... Surface observations early this evening continue to show that the lower to mid-levels remain quite dry with dew point depressions in some cases of 30+ degrees. ASOS/AWOS reports indicate that precipitation is just now reaching the ground over portions of central NY state with the remaining radar echoes closer to our area simply being virga. Based on these observational trends and latest hi-res guidance went ahead and pushed back the start time of the winter weather advisory to 11PM this evening, except south of Coos county in NH where it will begin at the original start time of 8PM.

PoPs were also delayed some, particularly across ME where column saturation and strong forcing for ascent does not look to arrive until late evening. Otherwise, just made some minor adjustments to temperatures and sky cover.

Previously... Tonight, a low moves eastward, bringing some precipitation into the region. An isothermic environment tonight will allow for most precipitation to start as snow. Overnight, southerly winds at low levels will break the isothermic layer allowing for a gradual changeover to sleet and freezing rain overnight.

SHORT TERM /THURSDAY NIGHT THROUGH 6 PM THURSDAY/

Tomorrow morning, interior locations are the most likely to see mixed precipitation into the morning commute, but mixed precipitation will transition to rain from south to north. Once transitioned to rain, temperatures will likely rise, as warm air works its way down to the surface tomorrow afternoon. High temperatures are likely to be in the upper 50s and 60s in the Connecticut River Valley and southern New Hampshire, with mid-40s in Maine and elsewhere.

LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/

04Z Long Term Update... Latest guidance continues to be in good agreement for a period of precipitation from a wave of low pressure to impact the area Saturday afternoon through part of Sunday. Temperature profiles look to support a period of mixed wintry precipitation initially across the foothills and points north with primarily rain likely further to the south and east. Did continue to incorporate this mixed precipitation in the weather grids. After this system mainly dry and cool temperatures look to prevail.

Previously... Overview: High pressure will build in Friday for fair weather. A period of active weather follows as wave of low pressure track along a frontal zone that slowly shifts south of the area early next week. The first wave will bring widespread wintry precipitation late Saturday into Sunday. Thermal profiles with this system will support snow/wintry mix across the interior early Saturday night with a transition to rain from SW to NE Sunday morning. There may be a lull in precipitation Sunday afternoon before the next wave of low pressure tracks across southern New England Sunday night. Chances for precipitation drop off Monday while global models suggest additional systems will be possible towards the middle of next week with a trough approaching the Northeast.

Impacts: Snow to a wintry mix could bring slick travel across northern areas late Saturday through Saturday night.

Details: Drier air will work into the area Thursday night into Friday on NW flow. A NW gradient will remain over area Friday as high pressure builds in from west with wind gusts approaching 25 mph. Skies will turn mostly sunny by Friday afternoon with highs ranging from the mid 40s north to mid 60s across southern NH. High pressure will crest over the area Friday night allowing for lows to drop into the low 20s to low 30s from north to south.

A wave of low pressure will track from the Ohio Valley towards the St Lawrence Valley late Saturday into Sunday with precipitation likely overspreading the area by Saturday afternoon. A dry airmass in place will allow for some wet bulbing leading precipitation starting as snow across the north and a mix of rain and snow south of the mountains. Warm air advection will continue through Saturday night with precipitation changing to a wintry mix across the north and rain across the south by Sunday morning. Temperatures will eventually rise above freezing across all areas after day break Sunday with rain becoming the dominant precipitation type. Precipitation will taper off Sunday afternoon before the next wave of low pressure approaches Sunday night.

The next wave of low pressure will bring chances for rain south of the mountains and a mix of rain and snow across the north Sunday night into Monday. Colder air attempts to work into the region Monday night that may allow for snow showers south of the mountains.

AVIATION /04Z THURSDAY THROUGH MONDAY/

Short Term...VFR expected this evening, with increasing cloudiness. IFR expected overnight and LIFR expected through most of the day tomorrow as a system brings snow, sleet, freezing rain and rain to the region. Conditions start to recover tomorrow evening, though low stratus may linger on the coast. VFR returns to the region Friday morning.

Long Term...Lingering MVFR cigs Thursday night will transition to VFR Friday into Saturday morning. Waves of low pressure brings a brief period of a wintry mix late Saturday changing to rain Saturday night with rain continuing through Sunday. Periods of IFR to LIFR will be possible late Saturday through Sunday. Some improvement is possible Sunday afternoon before the next system crosses New England Sunday night into Monday.

MARINE

Short Term...Southerly winds of 7-12kts expected this afternoon with 2-4ft seas. Winds and seas increase overnight as a low arrives from the west. Winds and seas pick up to SCA Thresholds tomorrow morning, with winds gradually shifting from southerly to southwesterly by the end of the day tomorrow.

Long Term...Winds shift out of the west Thursday night with gusts to 25 kts until Friday morning. High pressure builds over the waters Friday with winds and seas likely dropping below SCA thresholds by Friday afternoon. Waves of low pressure will track across New England this weekend with winds and seas approaching SCA thresholds Saturday night into Sunday. Winds will drop below 25 kts Sunday night while seas remain elevated into Monday.

GYX WATCHES/WARNINGS/ADVISORIES

ME...Winter Weather Advisory until noon EDT Thursday for MEZ007>009- 012>014. Winter Weather Advisory until 10 AM EDT Thursday for MEZ018>022-033. NH...Winter Weather Advisory until noon EDT Thursday for NHZ001-002- 004. Winter Weather Advisory until 10 AM EDT Thursday for NHZ003- 005>011-015. MARINE...Small Craft Advisory from 5 AM to 8 PM EDT Thursday for ANZ150>152-154. Small Craft Advisory from 5 AM to noon EDT Thursday for ANZ153.