Area Forecast Discussion
Issued by NWS Portland, ME

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KGYX 171417 AFDGYX Area Forecast Discussion National Weather Service Gray ME Issued by National Weather Service Caribou ME 1017 AM EDT Thu May 17 2018 .SYNOPSIS... Warm weather is expected today for much of the region as winds shift to the west ahead of a cold front. The cold front moves in from the northwest during the day today, with colder weather arriving for tonight and Friday. Temperatures on Friday and Saturday will be quite chilly especially over the coastal plain where an increasing onshore wind will bring a cooling effect from the ocean. Low pressure lifts north along the East Coast Saturday into Saturday night, bringing some rain to New England before the next cold front arrives on Sunday. High pressure behind this cold front will bring a few more nice days early next week. && .NEAR TERM /THROUGH TONIGHT/... 1000 AM UPDATE... Introduced isolated showers this afternoon and early evening from southern New Hampshire northeast to Penobscot Bay. High resolution models indicate just enough instability ahead of the weakening cold front for these showers to develop. Otherwise no changes. ORIGINAL DISCUSSION... Expect a warm day today for much of the area as a westerly flow ahead of a cold front brings warm air into the area. Subsidence inversion just above the boundary layer on the 00Z GYX sounding has been lowering with time, and will likely be even lower for the 12Z sounding, providing an easy target for a warm, well- mixed boundary layer to reach up to today. Currently expect temperatures along the coastal plain to reach well into the 70s to near 80 across southern New Hampshire, but a look at the 12Z sounding will give a more accurate picture of what peak temperatures will be today. A cold front will drop down from the northwest during the day today, bringing cooling temperatures aloft, but maintaining good mixing into the evening so temperatures will stay fairly warm until nightfall. && .SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/... Winds behind the cold front will likely keep the lowest layer of the atmosphere well mixed tonight, preventing ideal radiational cooling conditions. However, temperatures will be dropping especially in northern areas, primarily from cold advection from the north in this air mass with Arctic origins. Models are indicating low temperatures in the upper 20s in northern areas, with upper 30s to low 40s south of the mountains and see no reason to doubt this. Although we will have temperatures dropping into the 33 to 36 degree "frost" range for parts of the foothills region, the well-mixed low level environment will likely prevent much frost formation and limit the impact of these cool temperatures for tonight (unlike tomorrow night). Have included wording for "patchy frost" for parts of this area tonight, but again expect impact to be low and thus do not have confidence enough to issue a Frost Advisory. High pressure axis moves across Maine on Friday with light winds and cool temperatures expected. Since this air mass has origins in the Arctic, it will be cool and very dry. Afternoon dewpoints are likely to drop into the low 20s as the strong May sun acts to warm and mix the low levels. Temperatures could reach the mid 60s in northwestern parts of the area, but a developing easterly flow off the Gulf of Maine will keep the coastal plain cooler, in the low 60s or even upper 50s, setting the stage for another cold night. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... The surface high pressure system will move well east of the area Friday night allowing a frontal boundary south of the area to start pushing northward. Low pressure will develop along this front and move northeast during the day Saturday and Saturday night. As it does so, a southeasterly onshore flow will develop bringing low clouds and rain to the region. The rain will progress slowly northeast during the day Saturday. Models have varied considerably on rainfall amounts with GFS now the heaviest...with a half inch in the mountains and about an inch along the coast. Temperatures Friday night will be rather chilly with a freeze or frost possible in some areas, especially toward the north and east. Saturday`s temperatures will depend on how fast the easterly flow and precipitation develop across the area. Models have generally slowed the northward progression of the precipitation which may allow for a bit more warming before the onshore flow and precipitation start, especially in eastern sections. Moisture will linger across the region Sunday with the chance of a shower as a cold front approaches from the northwest. The front will cross the area Sunday night and move slowly east of the area Monday allowing skies to clear as high pressure builds into the region. Models continue to differ considerably after Monday. The European model keeps northwest flow over the region with high pressure generally dominating the rest of the week and only a weak cold frontal passage on Wednesday. In contrast, the GFS has a more zonal flow and brings an area of low pressure east impacting the area late Tuesday into Wednesday followed by high pressure for late Wednesday and Thursday. Blending the two models would suggest that there is a chance of showers Tuesday into Wednesday with improving weather for later Wednesday into Thursday. && .AVIATION /14Z THURSDAY THROUGH MONDAY/... Short Term...Low clouds and occasional fog are affecting primarily the Midcoast region early this morning as a southerly wind has brought this in off the Gulf of Maine. As winds shift to southwesterly, expect this area of clouds to make a shift to the east fairly early this morning, with a westerly wind bringing a sure clearing by mid morning. A cold front crosses the area from the northwest today, but will have little effect other than a shift in winds. VFR conditions continue into Friday as high pressure moves overhead. Long Term...VFR conditions Friday night lowering to IFR and LIFR during the day Saturday and Saturday night in rain and fog. Mainly MVFR conditions expected Sunday improving to VFR Monday. && .MARINE... Short Term...A cold front will move into the Gulf of Maine this evening, shifting winds to the northwest. As high pressure builds into Maine tonight, winds will become northeasterly over the Gulf of Maine, possibly accelerating to Small Craft Advisory levels by Friday morning. This northeasterly wind will bring the highest wave heights to the southwestern Gulf of Maine. Long Term...SCAs likely late Saturday into Monday morning. Otherwise winds and seas expected to be below sca criteria. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$NEAR TERM...Foisy/Kimble SHORT TERM...Kimble LONG TERM...Jensenius is the U.S. government's official web portal to all federal, state and local government web resources and services.