Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 281557 AFDGYX Area Forecast Discussion National Weather Service Gray ME 1157 AM EDT Wed Jun 28 2017 .SYNOPSIS... A trough of low pressure will move offshore this afternoon with a few showers possible across the interior and mid coast. A warm front will approach on Thursday and bring increasing chances of rain during the afternoon and especially the nighttime hours. Another low pressure system may affect the region on Saturday and possibly Sunday with more showers and thunderstorms. && .NEAR TERM /UNTIL 8 PM THIS EVENING/...
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1155 AM...For this ESTF update I adjusted near term grids to reflect satellite and radar trends as well as the current mesonet. Prev disc... 930 AM...Minor ESTF update to ingest the current mesonet into near term grids. Prev disc... 650 AM Update...Have updated the forecast for the balance of the day, mainly for sky cover and weather. Overall, the forecast philosophy has not changed. Incorporated the time lagged hrrr for PoPs this afternoon which still indicates chancy showers and isolated thunder, mainly across western zones as well as the mid coast of ME. Previously... An upper level trough will gradually move east today with heights beginning to rise. Even still, the air aloft will be anomalously cold which will aid in some surface based instability. A few showers and isolated thunderstorms should develop around or after midday - mainly across western/northern NH and the mid coast of Maine. Severe weather is not expected today and thunderstorm coverage is expected to be much less than yesterday. Most locations in the forecast area will likely remain dry. The best chance may very well be in Coos County NH and portions of the western ME mountains between 21z and 00z as a subtle short wave trough approaches in the mean NW flow aloft. In the meantime, some early morning patchy dense fog in spots is expected to burn off after sunrise.
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&& .SHORT TERM /8 PM THIS EVENING THROUGH 6 PM THURSDAY/... Any lingering showers/isold storms should dissipate quickly around 00z. Otherwise, we expect a pleasant night with temperatures dropping into the 50s - with some 40s at the better radiators well inland. A cold front will sharpen up and approach from the southwest on Thursday. Clouds will increase during the morning hours with light rain likely developing across western NH around midday or a bit later. This will spread eastward to adjacent western ME by early evening. Southernmost NH may remain dry for the entire day as the forcing for ascent remains just north of Cheshire and Hillsborough Counties. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... The forecast period begins with a fairly zonal upper level flow with a series of weak short waves helping to touch off showers. By Saturday a deeper trough has developed over the Great Lakes. This trough and accompanying surface cold front will move through the area on Sunday making way for high pressure to start next week. Friday will see a warm front draped across the forecast area. It will be hot a muggy with dew points in the mid 60s and high temperatures reaching the upper 80s across the southern portion of the area. Showers and thunderstorms will continue through the day. Expect there to be an east west oriented axis of heavier precipitation however still quite a bit of uncertainty of the exact placement within the region so have just gone with a generally equal PoP. The warm front begins to pull to the north on Friday night leaving our area firmly in the warm sector for Saturday. With temperatures in the 90s and dewpoints approaching 70 in the south the heat index will approach 95 in southern New Hampshire. This stifling heat and humidity will be perfect for thunderstorms and expect widespread storms in the afternoon as CAPE climbs. While there will be lots of instability there will not be as much shear for severe storms. 40kts or so at the tropopause will support thunderstorms but the larger concern will be heavy rain. Precipitable water values will also reach near maximum values for the date and storms would be slow to move without any fast jet or major forcing over head. Sunday a cold front will cross the region setting off yet another round of thunderstorms. Here the storms will be more focused along the front and a few severe winds gusts are possible. Monday and Tuesday high pressure builds back into the region with clearing skies and decreasing humidity. Highs will be near 80 for the 4th of July. Water temperatures offshore remain in the low to mid 50s and with the popular holiday weekend a beach hazard statement may need to be considered with the hypothermia risk continuing. && .AVIATION /16Z WEDNESDAY THROUGH SUNDAY/... Short Term...Patchy valley fog will burn off most locations by 13z this morning. Otherwise we expect VFR conditions today with some more patchy valley fog later tonight. A few hit or miss showers are expected this afternoon, but coverage is expected to be minimal. Long Term... Showers and thunderstorms will continue through the weekend. Brief periods of heavy rain and thunder will impact all terminals. Friday in the north will see more widespread MVFR ceilings while Saturday expect scattered convection to influence all locations. && .MARINE... Short Term...Small craft conditions are not expected today through Thursday. Long Term... Building seas with wind gusts to near 25kts in south westerly flow will likely necessitate a small craft advisory for Friday into Saturday. Seas will subside for the end of the weekend and start of next week. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$ ES

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