textproduct: Gray - Portland

WHAT HAS CHANGED

Increased cloud cover for this morning based on satellite trends and short term guidance.

KEY MESSAGES

1. A stray shower is possible through morning today, but otherwise fair weather expected through tonight.

2. Lower confidence chances of rain Thursday and again to end the weekend, with near to below normal temperatures expected.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

A warm front will continue to limp north thru the forecast area. Mid to high level cloudiness is likely to linger north of that boundary thru sunrise. That will keep things warmer than low temps yesterday. I do think that despite some clouds, radiation fog should still develop in the major river valleys by sun up. The earlier surge of warm advection rain/showers that tried to enter the forecast area ended up being primarily virga. Any showers moving east out of central and North Country New York will also struggle against dry air. So I may favor sprinkles over measurable precip in that case. In the warm sector today temps will surge well into and thru the 70s in some cases.

KEY MESSAGE 2 DESCRIPTION...

Over the last 24 hours ensemble guidance has shifted pretty sizable way on rain chances for the remainder of the week. The two events have largely flipped, with Thu trending towards more QPF and Sun trending drier. This is generally true of both the GEFS and ECMWF Ens, but the GEFS remains somewhat bearish on Thu still as well. Looking at the latest NBM guidance, it has come up for Thu, including introducing some categorical PoP. It has also backed off PoP over the weekend. This is my preferred shift to the forecast, so at this time no changes to the NBM are planned.

One of the reasons that the weekend rain chances have backed off is that guidance is coming in with stronger high pressure building down from central Canada. This is suppressing rain and the surface boundary south. ECMWF EFI is favoring Fri to be breezy behind a cold front as the high initially builds in. That will set up both Sat and Sun to be cooler days. Right now NBM temps are 5 to 10 degrees cooler than normal during the day. Overnight will also be cool, and given the time of year that means some frost potential across the northern valleys.

AVIATION /12Z WEDNESDAY THROUGH SUNDAY/

Through 12Z Thursday...Have scaled back fog potential at LEB and HIE this morning due to extensive cloud cover in place...so widespread VFR expected today. Light southerly winds will generally continue thru the TAF period along with some high level cloudiness. VFR conditions continue into tonight then clouds thicken and lower with areas of MVFR possible. Fog is possible at HIE and LEB once again, but there may again be too much cloud cover.

Outlook...

Thursday and Thursday night: Areas of rain showers and areas of MVFR conditions possible.

Friday: VFR conditions expected. Northwest wind gusts of 25 kt possible.

Saturday: VFR conditions expected.

Sunday and Sunday night: Rain showers and local MVFR or lower conditions possible.

MARINE

Winds and seas are expected to remain below SCA thresholds through the remainder of the week and likely into the weekend. The cold frontal passage Fri will bring some breezy conditions to the waters and maybe a few 25 kt gusts into early Sat however.

GYX WATCHES/WARNINGS/ADVISORIES

ME...None. NH...None. MARINE...None.