Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 131350 AFDGYX Area Forecast Discussion National Weather Service Gray ME 850 AM EST Fri Jan 13 2017 .SYNOPSIS... A cold front will exit the region this morning with much colder air arriving on gusty northwest winds behind it. High pressure will build in from the west through Saturday. A weak cold front will cross the area the area early Sunday, although will not produce more than some clouds and a few flurries in the moutnains. High pressure will build in behind the front Sunday afternoon through Monday. The high pressure shifts east on Tuesday and will allow a southwest flow of warmer air into the region. Weak low pressure crosses the region mid-week with a threat of precipitation. && .NEAR TERM /THROUGH TONIGHT/...
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---850am Update--- Temperatures this morning cooling a little quicker than expected...especially over the mountains. Will update the package to adjust things down a little bit and account for current trends. Winds will begin to increase over the next few hours. Expect southern waters to remain at Small Craft Advisory but it will be close enough that we will need to watch things closely. Otherwise...no significant changes expected. 630AM UPDATE... Have added the latest observations to the forecast to help pull the hourly temperature trends in the right direction. Cold advection ongoing across the area now, so daily high temperatures are essentially the current temperatures. Cooling has been delayed just a bit in the north where clouds have piled up against the mountains. These should dissipate soon as dry air moves in. ORIGINAL DISCUSSION... A cold front is pushing through the area at this hour (3AM). Ahead of the front, temperatures are in the 40s and 50s, but behind the front the temperature drops quickly through the 30s. By sunrise expect the colder temperatures to have arrived all the way to the coast. Even after the sun comes up it is unlikely that temperatures will rebound. Temperatures will instead be on a managed decline through the day as cold advection continues. There may be a couple of separate boundaries with stronger cold advection behind them which move through today, the first early this morning and the second during the late morning hours. Expect gusty northwest winds as cold advection causes strong mixing to occur. Winds aloft are expected to be on the order of 40 KT, so generally we are expecting wind gusts to about 30 MPH. However, a few gusts up to 40 MPH are possible as cold advection and downslope winds on the coastal plain will aid in transporting some of those stronger wind gusts toward the surface. By afternoon the entire area should fall below freezing.
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&& .SHORT TERM /SATURDAY/... Winds gradually diminish tonight as high pressure moves in from the west. Cold advection continues into the evening with temperatures falling below zero in the north and into the single digits above zero for most other areas. Due to the cold advection and pressure gradient, winds may prevent good radiational cooling conditions from occurring for much of the area. However, a clear sky and very dry air will allow the possibility of low temperatures falling to zero or below for any areas where winds are able to go calm. This will be most likely across western New Hampshire by early Saturday morning. Across the north, the combination of cold temperatures and moderate winds will lead to wind chill values of 20 below zero or colder. As a result, a Wind Chill Advisory has been issued for the areas most likely to see the combination of cold temperatures and persistent winds. Cold high pressure crosses the area on Saturday with temperatures about 10 degrees below normal, generally in the teens and 20s for an afternoon high in spite of a good amount of sunshine. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... Chance of high impact weather: Low. 500 mb pattern in the extended will be dominated by split flow over the eastern Pacific and western CONUS, which will basically flood the CONUS and southern Canada with Pacific air and allow above normal conditions well into next week. The tendency over the eastern CONUS will be for ridging as the split flow to the west breaks down and slowly carves out a trough there, but models have been consitent moving a trough through the northeast around mid- week providing a chance for some precip. Saturday night will not be as cold as Friday night with weak 500 mb trough passing to our N and W, but should allow for some clouds and warmer air ahead of another weak cold front which will cross the area early Sunday. Dry air ahead of the front will likely limit its sensible weather effects to some clouds and few flurries or SHSN in the mountains. Also, the shot of cold air behind this system will be brief and similar to airmass ahead of it, so highs Sunday will likely be warmer than Saturday and close to normal, ranging from around 20 in the N, to the low to mid 30s in the S. Behind this trough zonal flow at 500 mb persists into Monday eventually transitioning to ridging by mid-week, so the trend will be for gradual warming through the early part of the week and generally dry conditions. By Wednesday, we will start to see effects of several weak waves in SW flow in advance of the next 500mb trough, although models differ on timing, but 00Z Euro focus best chance for precip in the Wednesday to Wednesday night timeframe. P-type will likely be mainly rain, as unseasonably warm air moves in, but could start as a short period of snow or FZRA inland areas. System should clear by Thursday morning, with weak ridging moving through for the end of the week. Temps may drop off a bit behind this system, but will still be above normal. && .AVIATION /14Z FRIDAY THROUGH TUESDAY/... Short Term...Expect VFR conditions today with the exception of Whitefield early where MVFR ceilings will linger. Northwest winds will gust to 20 or 30 KT at times during the day today, but will eventually diminish tonight. Long Term...VFR through Tuesday. && .MARINE... Short Term...Strong northwest winds are expected behind the cold front today. At this point gale force wind gusts are most likely across the eastern waters where a Gale Warning has been issued. Further to the southwest, wind gusts should top off around 30 KT and a Small Craft Advisory will cover this. As high pressure builds in early Saturday, winds should fall below advisory levels areawide by Saturday morning. Long Term...NW winds may approach SCA levels briefly Sunday afternoon, but otherwise will remain below criteria through Tuesday night. && .GYX WATCHES/WARNINGS/ADVISORIES...
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ME...Wind Chill Advisory from 10 PM this evening to 10 AM EST Saturday for MEZ007>009. NH...Wind Chill Advisory from 10 PM this evening to 10 AM EST Saturday for NHZ001. MARINE...Small Craft Advisory until 6 AM EST Saturday for ANZ152>154. Gale Warning until 8 PM EST this evening for ANZ150-151.
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&& $$ Pohl

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