Area Forecast Discussion
Issued by NWS Caribou, ME

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000 FXUS61 KCAR 221433 AFDCAR Area Forecast Discussion National Weather Service Caribou ME 933 AM EST Wed Feb 22 2017 .SYNOPSIS... High pressure will build to our south today and tonight. Low pressure will track through Quebec on Thursday and track to our north Thursday night. High pressure will return on Friday. && .NEAR TERM /THROUGH TONIGHT/... Update 9:35 AM: Have adjusted wind, temperature, and dew point based on latest observations. No other changes. A weakening occluded front moving across the region early this morning may bring some very light showers or freezing rain, sleet or snow early this morning. Otherwise, the morning will be mostly cloudy and mild. High pressure building to our south will then bring a light southerly flow and a very mild day today with partial sunshine and highs reaching near 40 north to the low 40s Downeast. A small low will approach from the great lakes tonight bringing increasing clouds and a light southerly flow. Temps will remain mild, only dropping a couple degrees below freezing. Precipitation may begin to push into northwestern areas toward dawn. Boundary layer temps will be warm enough to support rain but surface temps will be just below freezing so will have a small chance of light freezing rain in the northwest toward morning. The light southerly flow and some increase in low level moisture may produce some patchy fog toward morning. && .SHORT TERM /THURSDAY THROUGH FRIDAY/... A continuation of the warmer temperatures expected. A warm front will lift across the region on Thursday as low pres moves across Quebec. Some light freezing rain/drizzle looks possible mainly north of the Bangor-Calais region in the morning. The NAM and GFS soundings support this potential w/dry air above the llvl moist airmass that will be in place. Warmer air is expected to allow for temps to rapidly rise above 32F after 8 AM and continue their climb during the day. The associated cold front is forecast to apch the region from the west later in the afternoon. The region looks like it gets into a pseudo-warm sector in the afternoon w/temps rising well into the 40s and possibly lower 50s in the downeast region. A pre- frontal trof looks like it could develop ahead of the cold front w/the airmass destabilizing. Decent shear at the 0-6km layer of 35_ kts w/elevated instability. The NAM/GFS soundings support this to be the case and point to some elevated CAPE of around 100 joules across the n and w in the afternoon. The NAM is the most robust w/this potential. This could lead to some squalls action of heavy showers w/graupel and brief wind gusts to 30 mph or so. The cold front is forecast to slide across the region Thursday night w/a cooldown by Friday morning. Any leftover rain showers could go to snow showers before ending. No accumulation expected. Temps in the upper 20s by 7 AM Friday across the n and w while central and downeast will see low/mid 30s. Friday will start out sunny followed by increasing clouds during the day ahead of the next weather system to affect the region through the weekend. High pres nosing down from Quebec will allow for the llvl cold air to get trapped near the surface. Decided to undercut the guidance for Friday`s max temps and leaned w/upper 30s to around 40 across the northern 1/2 of the CWA while central and downeast will see low to mid 40s. The long range guidance was offering some differing solutions w/the ECMWF and Canadian Global bringing some measurable precip by late Friday afternoon while the GFS and NAM keep precip shield at bay until Friday evening. Decided to use a blend and brought precip chance to 60% across swrn areas late in the day and have 40% elsewhere. The precip will be in the form of light rain starting out but as evap cooling takes hold, some light snow or sleet and possibly freezing rain later in the night. This will be discussed further in the long range section below. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... A challenging forecast shaping up this term through Sunday. Light rain Friday evening could go to a period of light snow or even sleet/freezing rain later in the night ahead of the main system w/evaporative cooling taking hold and continuing into Saturday morning. This would be especially true from the Central Highlands northward. The 00z runs of the NAM and GFS point to this scenario while the ECMWF and Canadian Global show warm air streaming in aloft w/llvl cold air eroding more quickly. Decided on a colder solution attm w/the sleet and freezing rain Saturday morning given the position of the high and cold air right at the surface. The warmer air wins out by mid morning w/precip going to all rain. Areas of fog expected as the warm air moves over the snowpack. There looks to be a lull in the activity by Saturday afternoon w/the main thrust of rain expected Saturday night. The latest cycle of the long range guidance points at the potential of a 2nd low developing on the apchg frontal system Saturday evening and moving across eastern Maine. This would bring a good slug of rainfall to the region w/anywhere from 0.50 to 1.00" of liquid precip. The deep snowpack in place should be able to absorb much of the rain especially for the northern 1/2 of the CWA. The downeast region could see some runoff as snowpack continues to erode. This would also allow for some rises on rivers and streams w/the potential for any ice movement. Duration of rainfall and warm air will be key. Another item of concern will be the sse winds Saturday night. A 925mb jet of 45+ kts is forecast to move across the downeast region w/the potential for winds gusts to 40 mph. Guidance was showing colder air to filter into the region by Sunday morning w/a period of snow before the precip ends. The daycrew can assess this potential today w/the later guidance. Sunday looks to be a windy and colder day w/snow showers and a wnw west wind. Wind gust potential of 35 to 40 mph possible especially across the open and high terrain. Temps will be falling throughout the day on Sunday. High pres is expected to briefly ridge across the region Sunday night w/increasing clouds later at night w/another weaker system apchg from the w. This weaker system could bring a round of light snow to CWA on Monday w/daytime temps back to more seasonal norms. && .AVIATION /15Z WEDNESDAY THROUGH SUNDAY/... NEAR TERM: VFR conditions are expected today into tonight. Conditions may lower to MVFR in some sites late tonight in some mist or light fog and, across the north, some lowering ceilings. SHORT TERM: IFR conditions expected on Thursday w/some MVFR Thursday afternoon but a return to IFR Thursday evening as the front slides across the region. LLWS potential is there for Thursday especially in the afternoon. Conditions to gradually improve to VFR by mid to late Friday morning. Another frontal system is expected to affect the region later Friday night into the weekend. This will bring lowering cigs and vsbys to IFR w/some fog and rain. There is potential for some light icing across the northern terminals early Saturday morning. && .MARINE... NEAR TERM: Winds and seas are expected to remain below SCA today and tonight. Some fog may spread across the waters late tonight. SHORT TERM: No headlines expected through Friday. Some gusts to 25 kts for the outer zones possible later Thursday into Thursday evening. Attm, kept sustained wind 15-20 kts and seas 3-4 ft for these zones. Closer in along the intra-coastal zone, 10-15 kts and seas 2-3 ft. Things expected to change come Saturday, especially Saturday night into Sunday w/sustained winds of 2-25 kts and gusts apchg 30+ kt. Sunday will definitely be the windy day w/25 kt sustained winds and gust potential of 30-35 kts as colder air moves over the warmer Gulf of Maine waters. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...None. MARINE...None. && $$ Near Term...Mignone

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