Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 292300 AFDGYX Area Forecast Discussion National Weather Service Gray ME 700 PM EDT Thu Sep 29 2016 .SYNOPSIS... High pressure will continue to build into the region from the north through Friday. Low pressure over the midwest drifts slowly north and east through the weekend. This low will eventually bring the chance of showers to the region Friday night through at least Monday. High pressure will again build in from the north by the middle of next week. && .NEAR TERM /TONIGHT/... 7PM UPDATE... Have updated the forecast to adjust temperature trends based on latest observations. Have also zeroed out the precipitation chances for the evening. Some clouds moving in from the south but should not see precipitation until possibly tomorrow morning. ORIGINAL DISCUSSION... Dry air in the lower levels of the atmosphere will continue to drive mainly clear skies into the forecast area through this evening. However, the flow will gradually veer in the upper levels of the atmosphere around the periphery of the cutoff Ohio Valley low pressure system, bringing cirrus to the region. Initially, clouds will advance into southern New Hampshire late tonight. There may remain a few low clouds caught underneath the inversion as well. In areas that remain clear, patchy fog is expected across the inland valleys, especially over northern areas. Chilly 30s are expected in the north and mountain areas for overnight lows with radiational cooling under clear skies and light winds. && .SHORT TERM /FRIDAY AND FRIDAY NIGHT/... Moderate risk for rip currents for area beaches Friday. Moisture will continue to slowly rebound northward on Friday with a low chance pop for showers over southernmost areas. This will be in response to a nearly stationary area of surface low pressure along the Mid Atlantic coastline. There will be a sharp division between cloudy and clear areas as well as a sharp cutoff to any light precipitation. Pops increase Friday night as low pressure moves northbound to a position south of Long Island New York. This track will lend itself to possibly slightly heavier precipitation along the coast and portions of southern New Hampshire in the extended portion of the forecast as the upper level low pressure system remains relatively stationary. Most mesoscale models today are now projecting some precip is possible as far north as central areas. However, have kept precip mainly over southern areas as a dry atmosphere will initially be in place across the interior. && .LONG TERM /SATURDAY THROUGH THURSDAY/... There is a lot of forecast uncertainty in the extended...revolving around the lifting of Midwestern cut off low pressure. Both the 29.12z GFS and ECMWF slowly lift the low into the Great Lakes thru the weekend. As it does so...onshore flow will increase and diffluence aloft will be more conducive to support showers. Surface high pressure to the N will try and fight precip a bit as it continues to supply dry air. This puts the forecast area between the dry air to the N and showers to the S...and that battleground is the cause for the uncertainty. Highest PoP will be across southern zones and near the coast...while northern zones look to stay dry the longest. Beyond early next week model guidance diverges in handling of how the upper low finally lifts out and how the pattern evolves behind it. The GFS favors higher heights building across New England...while the ECMWF favors lower heights. This will have big implications on how progressive the next trof can be as it crosses the northern tier. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/... Short Term...Through Friday night, VFR conditions over central and mountain areas with mainly MVFR conditions over southernmost areas. Some overnight and early morning valley fog til 13z will allow for local IFR conditions. Long Term...As the upper low pressure lifts across the Northeast MVFR conditions will likely work back into the forecast area in the form of stratus. SHRA will be more likely at southern NH terminals MHT...PSM...and CON thru the weekend. At night...cooling may bring occasional IFR CIGs to southern NH and coastal terminals. It will be hard to find stretches thru early next week where MVFR or lower can be ruled out completely. && .MARINE... Short Term...Persistent Northeast flow will continue SCA conditions outside the bays through Friday. However, seas maxed out this morning and have subsided slightly. Long Term...NE flow will continue as upper low pressure lifts towards the Northeast. As the gradient increases into the weekend and NE flow picks up...seas will build back over 5 ft on the outer waters. Winds look to increase to near 25 kts on the outer waters as well. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...Small Craft Advisory until 6 PM EDT Friday for ANZ150-152. Small Craft Advisory until 6 AM EDT Saturday for ANZ154. && $$ NEAR TERM UPDATE...Kimble

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