textproduct: Gray - Portland

SYNOPSIS

A strong cold front will barrel through the region during the day today. Scattered heavy snow showers and squalls along the front will give way to gusty winds this evening and tonight. Temperatures will fall from the 30s into the single digits and even below zero in places by Friday morning. Wind chills even at the coast will be below zero. High pressure will arrive later Friday and more seasonable temperatures return Saturday.

NEAR TERM /THROUGH TODAY/

An arctic cold front is expected to slice across the forecast area today. The result will be tumbling temperatures this afternoon through tonight with very cold wind chills in place. Have issued a cold weather advisory for the northern mountains as wind chill values even in the valleys should get down to around -20F.

Most of the parameters favorable for heavy snow squalls are present near and along the front today, even at the coast. Snow showers are expected to reach northern NH around 12z this morning with broken lines of snow squalls marching southeastward thereafter as the front marches on. The best chance for snow squalls across southern NH and coastal ME will be after 19z or so, with the threat continuing through about the 22z-00z timeframe. Any area that experiences a squall today should expect brief very low visibilities, gusty winds, and dangerous travel conditions. It's possible that a few snow squall warnings will have to be issued, especially during the afternoon/early evening commutes. Thereafter, temperatures take a tumble.

SHORT TERM /TONIGHT THROUGH FRIDAY/

Behind the aforementioned arctic front it will get gusty. Bufkit soundings suggest 30 to 35 mph for a few hours this evening.

The winds will also coming with plummeting temps. By Fri morning widespread single digits are expected going below zero in the mountains. Ensemble guidance is all in agreement on an anomalous air mass...with extreme temps for this time of year possible. This matches up well with NBM forecasts of record or near-record temps...see climate section below. With the cold temps and continued gradient winds...wind chills will likely get to around 20 below zero in the northern zones tonight. Therefore a cold weather advisory has been issued for northern Coos County NH northeastward into the western ME mountains.

Frigid temperatures will be the theme Friday morning with lows mainly in the single digits below zero across the north, to the single digits above south. While the pressure gradient will be relaxing, some winds in the 10 to 15 mph range will lead to some frigid wind chills sticking around through the morning hours.

Cold temperatures will hang around through the day under near zonal flow aloft. Highs will only range from the lower teens to lower 20s for most, but we could see a few single digits in/around the mountains and some mid 20s along the coast.

LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/

Pattern Overview: The weather pattern remains unsettled as troughing dominates the long term period. Some light snow showers are possible through the weekend, before ridging brings us a dry start to the week. Then, the next system of significance is possible mid-week. Impacts and Key Messages: *No significant weather impacts expected at this time. *Temperatures run below normal through much of the long term period, with very cold nights. Details: Friday Night: Friday night will likely feel slightly warmer as winds calm. Zonal flow aloft transitions more southwesterly and this adds some clouds to the mix, but it is likely we can still radiate down into the single digits across the area. Models have converged on low pressure passing well to our south, but enough moisture could sneak into the region to sustain some light snow showers along a shortwave. Far southern New Hampshire may see this in the predawn hours of Saturday. Saturday and Sunday: Light showers spread north and east with the rest of New Hampshire and most of Western Maine having at least a slight chance of seeing some flakes during the day Saturday. The increased cloud cover during the afternoon hours keeps high temperatures limited to the mid- to upper 20s areawide, with low 30s possible in far southern New Hampshire and along the immediate coast. The last of the shower activity departs during the first part of Saturday night as the low pressure well offshore continues pulling off to the east. Southwest flow aloft through the day will have slightly warmed the airmass overhead so low temperatures only bottom out in the teens. High pressure noses in during the day Sunday which keeps the area mostly dry, with the exception of upslope snow showers as flow becomes northwesterly. A little bit of a sunnier day should aid high temperatures in climbing into the mid- to upper 30s south of the mountains, and into the upper 20s and low 30s north. A frontal boundary sinks southward Sunday night, plummeting temperatures into the single digits as it moves through. A stiff breeze behind this front may make it feel more like it's sub- zero. Forcing from the front along with forcing from a broad trough approaching aloft may also tip off some light snow showers overnight. Monday-Wednesday: The first part of next week looks dry with high pressure building in at the surface, but questions about our next potential system arise as we head toward the mid-week period. The global suites are in surprisingly good agreement that low pressure swings through the Great Lakes Region and into our area mid-week, but the track after that is where they currently diverge. Ensemble clustering is pretty tight for an initial inside runner, but the ECMWF is leaving the door open for a jog to the south (colder solution for our area), while the GFS clusters mostly remain on the inside to overhead track (pulls in warmer air). This is going to be the period to keep a close eye on trends going forward.

AVIATION /03Z THURSDAY THROUGH MONDAY/

Short Term...An arctic cold front will drive through the region today bringing a chance for heavy snow showers/squalls and brief local IFR or lower conditions. Behind the front surface wind gusts up to 30 kt are possible this evening. Northwest of the mtns some lingering MVFR CIGs are possible in upslope flow/snow showers.

Long Term...Occasional snow showers early Saturday morning through Sunday night may bring about brief MVFR or lower restrictions, but outside of these VFR should prevail through Monday.

MARINE

Short Term...A strong cold front will blast across the waters this afternoon with strong wind gusts anticipated behind it. Gale warnings have been issued for all waters into tonight. While waters are still relatively warm...the coming air mass will be quite cold and some pockets of freezing spray are not out of the question.

Long Term...Conditions on the waters remain below SCA criteria through the weekend. Wind gusts ramp up early Monday morning behind a frontal passage and remain elevated through Monday night. Winds taper off but sub-SCA conditions will be brief as low pressure passing offshore builds seas Tuesday night. Seas should then gradually diminish Wednesday morning.

CLIMATE

This air mass on Fri morning will be anomalously cold and low temps will approach records. This will especially be true at PWM where the forecast is 4 degrees and the previous record is 7 in both 1989 and 1945. The forecast at AUG is 5 degrees and the previous record is 4 set in both 1989 and 1991.

GYX WATCHES/WARNINGS/ADVISORIES

ME...Cold Weather Advisory from 9 PM Thursday to 8 AM EST Friday for MEZ007>009. NH...Cold Weather Advisory from 9 PM Thursday to 8 AM EST Friday for NHZ001. MARINE...Gale Warning from 3 PM Thursday to 5 AM EST Friday for ANZ150- 152-154. Gale Warning from 5 PM Thursday to 3 AM EST Friday for ANZ151- 153.