textproduct: Gray - Portland

WHAT HAS CHANGED

Little change to the previous forecast, if anything rainfall totals have trended down as precipitation is looking more showery and moving faster thru the region today.

KEY MESSAGES

1. Beneficial rain expected for the majority of the forecast area today.

2. A cool pattern persists through the weekend and into early next week with chances for showers.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

Moist onshore flow is resulting in areas of drizzle with embedded rain showers. With showers becoming more widespread I allow the character of precip to move away from drizzle from this point forward in the forecast. So far visibility has been behaving but patchy fog will be possible thru morning as well. Rainfall will begin to creep into southwestern NH over the next hour and steadily progress eastward thru morning. Forecast soundings continue to show elevated instability, so in addition to a rumble of thunder some of the rainfall rates may be briefly heavy. Despite that this is mostly a beneficial rainfall given both the long and short term dryness. Currently 6 hr flash flood guidance is generally between 2.5 and 3 inches. Looking at the latest HREF, the max QPF over the next 24 hours is 2.5 to 3 inches. Latest convection allowing guidance has trended much more showery however, so rainfall totals may ultimately come in well below that potential. So we should be able to handle this amount of rainfall without much trouble. The heaviest rain will be during the morning, and begin to clear southwestern NH during the afternoon. Showers, especially in the higher terrain may linger thru much of tonight.

KEY MESSAGE 2 DESCRIPTION...

The cool pattern looks to persist through the weekend and into early next week as a trough deepens across the Northeast and Great Lakes. This brings daytime highs mainly in the 40s across the north, and 50s south of the mountain. With cold air aloft associated with the trough, instability showers and an increase in cloud cover are likely each afternoon, especially across the higher terrain.

A coastal storm tracking offshore on Sunday has trended a bit further west since yesterday, bringing a steadier shield of rain closer to the coast. Should this westward trend continue, a steadier round of rain would be expected, so it's worth monitoring over the coming model runs. After Sunday, the next chance for showers would come on Tuesday as the next shortwave rotating around the trough approaches from the west.

AVIATION /12Z THURSDAY THROUGH MONDAY/

Rainfall may briefly reduce VIS to IFR or lower for all terminals thru this afternoon. LLWS remains possible at RKD thru mid morning as strongest winds aloft cross the area. Conditions return to VFR this evening as winds turn northwesterly and downslope off the mtns. HIE may linger around MVFR CIGs as opposite will be true on the north side of the terrain.

Outlook:

Friday: VFR conditions expected.

Friday Night-Saturday Night: Mainly VFR, with some periods MVFR and showers possible, especially during the afternoon.

Sunday-Sunday Night: MVFR and light rain possible.

Monday-Tuesday: Mainly VFR, but periods of MVFR and scattered showers possible.

MARINE

Northeast winds gradually turn southerly thru morning and increase. SCA gusts are possible for all waters before they diminish. SCA conditions continue overnight for the coastal waters and outer Casco Bay as seas remain above 5 feet. Patchy fog will also be possible thru this morning along with briefly heavy rainfall during the day.

Seas likely settle below 5ft by Saturday morning. Broad high pressure builds across the waters into Saturday. A deepening low pressure system likely tracks outside the Gulf of Maine on Sunday. Southerly flow then freshens early next week with SCA conditions possible by Monday night ahead of an approaching cold front.

GYX WATCHES/WARNINGS/ADVISORIES

ME...None. NH...None. MARINE...Small Craft Advisory until 8 AM EDT Friday for ANZ150-152>154. Small Craft Advisory until 8 PM EDT this evening for ANZ151.