Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 240747 AFDGYX Area Forecast Discussion National Weather Service Gray ME 347 AM EDT Mon Jul 24 2017 .SYNOPSIS... Low pressure will move up the coast bringing widespread rain to the area through tonight. Wet conditions and showers will persist through Tuesday. The unsettled weather slides off to the east for Wednesday. High pressure will build into the area with comfortable temperatures and sunny skies. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Expect rain to spread through the region from Southwest to northeast today as low pressure develops off New Jersey and tracks through the Gulf of Maine. At 3am height falls indicated the low beginning to take shape just off the Jersey Shore. A second broader area of low pressure over New York state was headed up the St. Lawrence valley. While many models continue to suggest these two lows will be of about equal strength I expect the coastal low to dominate and eventually gain strength at the expense of the northern stream resulting in a generally southward shift of the heavier precipitation which is reflected in teh forecast package. Rain will move into Southwest New hampshire by daybreak. With dewpoints still in the 40s to low 50s along the Canadian border expect it to be slow to saturate and it will take until early afternoon for rain to reach the ground across the entire forecast area. While overall this is a rather weak storm compared to the ones we typically see on this pattern in winter there is some potential for heavier pockets of rain especially this afternoon across southern New Hampshire. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/... By this evening the low center will be well into the Gulf of Maine with the maine precipitation shield out over the water. Meanwhile the northern Mountains will begin to see some upslope continuing showers. Along the coast the forcing for any sort of steady or heavier rain has passed, but the moist saturated airmass remains and patchy drizzle along with fog can be expected overnight. The damp conditions will remain through the morning on Tuesday. By tuesday afternoon the upper level low will finally pull east of the area allowing the surface flow to switch around to the west and move dryer air and high pressure in on Wednesday. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... Upper trof axis swings thru the region early Wed...allowing things to clear and dry out. Surface ridge axis is forecast to settle over the forecast area prior to 12z...so valley fog could be fairly widespread. Once that lifts...it should be a sunny and pleasant day. Upper ridging is short lived however...as the next s/wv trof will be approaching from the W early Thu. Timing of the wave is favorable for diurnally assisted...scattered showers and thunderstorms. Late in the day global model guidance is being dominated by Mid MS Valley convection. Models develop a surface reflection that propagates downstream towards New England. At this time the CMC and GFS remain S...while the ECMWF is a Nrn outlier. Given that this is convection...and convection that is still some 48 hours from developing...I will maintain with the multi-model consensus and at least let convection develop tonight before making any large changes to PoP grids. Once that front pushes thru the region...we will return to a general pattern of a l/wv trof over the Ern CONUS. This will keep precip chances more or less confined to the passage of cool fronts every other day or so. && .AVIATION /07Z MONDAY THROUGH FRIDAY/... Short Term /through Tuesday/...While conditions remain VFR for the moment expect to see a decrease from southwest to northeast into MVFR in showers this morning. By nightfall the fog and low stratus will become more widespread resulting in IFR across most of the region. The IFR fog will be slow to lift on the coast on Tuesday but elsewhere we`ll see a return to MVFR by daybreak with the entire region moving towards VFR by Tuesday night. Long Term...Conditions are expected to improve Wed to VFR as high pressure builds in. Confidence decreases during the latter half of Thu into Fri...as the next chance for precip arrives. A cold front approaching from the W and a possible convective complex may bring MVFR or lower conditions to much of the area. If sufficient moisture can return N behind the departing high pressure...a period of IFR conditions is possible for coastal terminals. && .MARINE... Short Term /through Tuesday/... Increasing easterly flow ahead of the developing low will result in wind gusts to around 30kt as a low level jet mixes down over the waters. The prolonged easterly flow will also result in waves building to around 5-6ft. A small craft advisory has been issued with the strongest winds and waves expected along the new hampshire coast closest to the low center. Long Term...Winds and seas expected to remain below SCA thresholds thru late in the week. Convectively enhanced low pressure may try and develop in the Gulf of ME late in the week and bring a period of SCA conditions to the outer waters. && .TIDES/COASTAL FLOODING... High astronomical tides tonight may contribute to some localized minor coastal flooding right around the times of high tide during the late evening hours. Last night the portland tide gauge reached 12.1ft. With increasing easterly flow and a similar tide prediction for tonight have opted to issue another Coastal flood advisory. High tide at Portland is forecast to be 11.5ft at 12:46am, which combined with the easterly flow and existing anomaly will likely result in a tide once again just cresting 12ft. This will cause minor nuisance flooding in Portland along the wharfs as well as along coastal roads in York county, and along back coves and low lying areas of New Hampshire. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...Small Craft Advisory from 11 AM this morning to 2 AM EDT Tuesday for ANZ150-152-154. && $$ NEAR TERM...Curtis SHORT TERM...Curtis LONG TERM...Legro AVIATION...Legro MARINE...Legro TIDES/COASTAL FLOODING...Curtis

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