textproduct: Gray - Portland

SYNOPSIS

An upper level disturbance will cross New England today bringing a round of snow showers and potential squalls, especially in the mountains. After high pressure quickly moves near the region Saturday into Saturday night, low pressure will draw moisture and precipitation back into the region Sunday. High pressure then tracks through New England Monday and Monday night.

NEAR TERM /THROUGH TODAY/

610 AM Update...Quick update to take down the Small Craft Advisory for the outer waters as winds are expected to ramp up to gale force later this morning and a Gale Warning is in place. Otherwise, just loaded in the latest observations as the forecast remains on track. Snow showers have largely stayed to the north of our area to this point, but we should see them begin to make it into western New Hampshire later this morning.

Previous Discussion... A short wave trough will pass across northern New England today. The SFC wind trajectory will be as such that some Great Lakes moisture will be pulled eastward and into the system. This along with steep low level lapse rates and modest forcing for ascent will allow for scattered snow showers and perhaps snow squalls for a good portion of the day. The leading edge of the deeper ascent will arrive at the CT River valley around 12z this morning give or take a couple hours. Therefore, we will start chance PoPs in the west around that time and gradually spread them eastward through the morning. They will be most numerous in the mountains but stability indices such as the Froude number will be quite high so we expect some snow showers to make it to the coast as well as southern NH. Temperatures will be marginal for snow on the coastal plain but steep lapse rates should allow it to occur.

Slippery travel is likely in spots.

Winds across the region will increase during the day and gust 20 to 30 MPH, especially across southern NH and southernmost ME.

SHORT TERM /TONIGHT THROUGH SATURDAY/

Snow showers will wind down south and east of the mountains as we lose daylight and as the shortwave crosses to the east this evening. The mountains will stay mostly cloudy with widely scattered snow showers continuing through tonight as flow and moisture will remain conducive for upslope precipitation. It will be a chilly night as temperatures drop into the 20s, but with it remaining breezy, wind chills will be in the 10s, possibly single digits across the north.

High pressure moves in Saturday making for a fair weather day. Winds will be much lighter too. Temperatures will remain chilly with 20s in the mountains and mainly 30s elsewhere.

LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/

High pressure will move out of the area Saturday night, as a low approaches from the west. Precipitation moves in Sunday morning, with snow likely in the mountains but mostly rain elsewhere. A couple inches of snow is not out of the question north of the mountains, but snow will struggle to accumulate in the foothills and south. Precipitation should clear out of the area for most by Sunday evening, with some lingering snow showers expected to persist across the interior through Monday morning.

High pressure returns on Monday with mostly dry conditions likely, along with clearing skies. However, this period of quieter weather will be brief.

Monday night, a low pressure system looks to develop over the Ohio River Valley, and move eastward. Cyclogenesis looks favorable as the low looks to position itself in the left exit region of a weak upwind jet streak, as well as the right entrance region of a much stronger jet streak downstream. This should allow for increased upper-level divergence and lower pressure falls within the low. Uncertainty still remains with storm track, but models have come into stronger agreement that winter weather is likely Tuesday, and this system has a solid chance of becoming the first notable widespread winter storm for the region. Despite the large spread on intensity, ECMWF and GFS Ensemble snow probabilities show at least a widespread 40% chance to see greater than 6 inches of snow across New Hampshire and western Maine. Snow may be heavy at times and substantially skewer visibility during the day Tuesday.

Wednesday and Thursday look drier and higher pressure works into the area. A couple isolated snow showers can't be ruled out across the interior.

AVIATION /11Z FRIDAY THROUGH TUESDAY/

Short Term...VFR conditions are expected to prevail today through Saturday. However, temporary lower conditions are expected in snow showers today, with vsbys a 1/2 mile or less for brief periods of time. These will end tonight with sunny skies expected Saturday.

Today will be gusty with westerly gusts 20-30 kt, possibly up to 35 kt, during the day, especially across southern NH. Much lighter winds Saturday.

Long Term...VFR is expected Saturday night, restrictions will likely lower through the day Sunday, with the heaviest restrictions possible in the north due to snow. Restrictions will stay down through Monday morning. VFR prevails through the remainder of Monday, and into Tuesday morning. Restrictions lower on Tuesday due to an possible winter storm.

MARINE

Short Term...Solid SCA conditions continue over the waters through early this morning before the gradient tightens, resulting in westerly gales over the outer waters and SCA conditions by noon. Winds and seas should begin to come down overnight and toward daybreak Saturday.

Long Term...Northwesterly winds look to diminish Saturday night, becoming light and variable through Sunday afternoon. Seas lower from 3-5ft to 2-3ft in this timeframe. SCA thresholds are likely Sunday night through Monday morning, with some gales possible during this time frame as well. Marine conditions improve on Monday but SCA thresholds may return again by Tuesday night.

GYX WATCHES/WARNINGS/ADVISORIES

ME...None. NH...None. MARINE...Gale Warning from 10 AM this morning to 7 AM EST Saturday for ANZ150-152-154. Small Craft Advisory from 10 AM this morning to 7 AM EST Saturday for ANZ151. Small Craft Advisory until 7 AM EST Saturday for ANZ153.