Area Forecast Discussion
Issued by NWS Portland, ME

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052 FXUS61 KGYX 211113 AFDGYX Area Forecast Discussion National Weather Service Gray ME 713 AM EDT Fri Oct 21 2016 .SYNOPSIS... A slow moving frontal boundary and a developing low pressure center will bring wet weather and a cool onshore flow to the region into Saturday. Later Saturday and Saturday night...the low will gradually lift north into Quebec. On the backside of this low...colder air will arrive on brisk northwest winds for the latter part of the weekend and early next week. Some accumulating snow will be possible in the mountains Saturday night into Sunday night. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 7 am update: Along with the areas of light rain, areas of fog and drizzle have also developed as warm moist air moves over the cooler and saturated low level marine layer. Will expect the areas of fog and drizzle to continue most of the day. Made some minor adjustments to lower pops over southern NH for the rest of the morning as main area of light rain should remain over central and northern areas of the cwa. No other changes needed at this time. Previous Discussion: A strong digging upper short wave will be moving through the Ohio Valley today. In advance of this deepening system a very moist south to southeast flow will transport plenty of moisture across the area. Warm moist air aloft will move over the cooler surface maritime air mass today produce periods of overrunning rain and also developing drizzle and areas of fog. The onshore flow will keep temperatures in the upper 50s to lower 60s across most areas. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/... The digging short wave continues to drive southeast into the mid Atlantic coast tonight allowing the trough to become negatively tilted, and then tapping some tropical moisture that will exist from a system well off the east coast. The rain will become heavy at times tonight due the combination of the tropical moisture and increasing UVV as the upper trough swings northeast and develops a closed low over our area by Saturday morning. QPF totals of 1.5-2.5 inches are expected. On Saturday with the upper closed low moving across northern New England, will have to expect scattered showers through the day and most numerous in the mountains. By later in the day winds will increase from the west over southern areas of the forecast area under the strong cyclonic flow to the south and west of the upper low as it slowly departs to the north. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... Chance of high impact weather: Low. Wind gusts Sunday could approach 40 mph. Accumulating snow is expected at higher elevations in the mountains. 500 mb pattern across NOAM continuing to show signs of a change, with troughs developing over the the eastern and western parts of the continent in a broad omega type block. Not high confidence that this pattern will hold as even during the course of next week the troughing shows signs of breaking down before being reinforced, but the trend will favor cold air rather than warm air so look for temps run below normal to normal in the long range. Will start the period on Sat night and Sunday with deepening closed 500 mb low and sfc low tracking N across the region before stacking up over interior Quebec Sunday night. This will produce gusty NW flow across the region beginning Sat night and peaking during the day on Sunday, with gusts in the 30-40 mph range. Any lingering Shra outside of the mountains Sat night should wind down on Sunday as the downslope takes over. In the mountains, look for SHRA to continue into Sunday in upslope flow, with rain changing to snow across the higher terrain, and perhaps mixing with snow a little in the valleys Sunday morning. Because the the stacked low shifts back to the NW on Sunday the coldest air will have to wait for secondary 500 mb trough crossing the region Sun night into Monday, and models have backed off the intensity of the cold air on Sunday, so, it does look like the accumulation will be limited to higher elevations late Sat night into Sunday evening. Lows sat night will range from the low to mid 30s in the N, to the low 40s along the coast and in srn NH. Highs on Sunday will be in the low to mid 40s in the mountains to low to mid 50s in the south, where some downslope warming will counteract the CAA and bring some sun to this areas as well. Sunday night`s lows will be similar to Saturday night as decent boundary layer flow persists and clouds return as the next wave approaches. Monday will see the stronger cold of cold air, and it will remain breezy, but not as bad as Sunday. Highs Monday may be a degree or two cooler than Sunday, but situation is similar with downslope/upslope conditions. Mon night lows will range fromaround 30 in the N, to the mid to upper 30s in the S. NW flow persistson Tue, with CAA weakening and eventually clearing out Tue night and Wed. Highs Tue and Wed will be in the mid 40s to lower 50s, and lows Tue night will be in the mid 20s N to low to mid 30s S. Wed night may be the coldest night as winds finally diminish with some rad cooling and lows may get below freezing across most of the CWA, with the mountains possible dropping close top 20. Next chc for precip will be Thu or Fri and could start as snow in the mountains as 500 mb trough drags a weakening sfc low across nrn ME. && .AVIATION /11Z FRIDAY THROUGH TUESDAY/... Short Term /through Friday night/...IFR to LIFR conditions in rain...drizzle...and areas of fog through early Saturday...then conditions will improve to MVFR in scattered showers Saturday afternoon. Long Term...MVFR Sat night should improve to VFR by Sunday morning outside of the mountains, which will linger in MVFR to IFR briefly in SHRA at KHIE through Sunday. Also look for NW winds of of 15-20 kts on Sunday with gusts as high as 35 kts possible. VFR is expected at all terminals Mon and Tue. && .MARINE... Short Term /through Friday night/...Increasing and persistent onshore flow will bring small craft conditions to the open waters and marginal small crafts to the bays through Saturday. Long Term...A period of gales is expected Sat night into Sunday with winds diminishing a bit Sunday night into Monday morning, but gales could return briefly Mon night. && .TIDES/COASTAL FLOODING... This afternoon the 4 pm astronomical tide in Portland will be 10.6 feet. A weak southeasterly flow ahead of the system may allow for a half to as much as a one foot storm surge during the time of high tide. This will not be enough to cause any minor coastal flooding although some minor splashover may occur due to some rough seas. The situation will continue to be monitored during the afternoon. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...Small Craft Advisory until 8 PM EDT Saturday for ANZ150>154. && $$ NEAR TERM...Marine SHORT TERM...Marine LONG TERM...Cempa is the U.S. government's official web portal to all federal, state and local government web resources and services.