textproduct: Gray - Portland

WHAT HAS CHANGED

No major changes were needed for this forecast package.

KEY MESSAGES

1. Showers will continue to diminish from west to east this morning, with a mostly dry and breezy day to follow.

2. On and off precipitation chances continue with slightly below average temperatures.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

A cold front will continue to move out to the Atlantic with some lingering showers across the forecast area on the backside. This activity should end from west to east early this morning, but another wave may reinvigorate some precipitation later this morning, mainly off the coast of Maine. However, there may be enough of a glancing blow to see a few more showers over land along the coast in the 08z to 12z time frame.

After rain moves out, the rest of today and tonight should be mostly dry with clearing skies outside of the mountains. Westerly winds will become fairly breezy by the afternoon hours with sustained values to around 15 mph and gusts up to around 25 mph. The higher terrain will likely see some gustier winds. Relative humidity will dip into the 25 to 30 percent range over southern New Hampshire and portions of southwest Maine, but given recent widespread wetting rains, fire weather concerns remain limited.

Regarding temperatures, lows this morning will be cooler behind the front, ranging from the mid to upper 30s north, to the low to mid 40s south. Highs this afternoon will range from the mid 40s to lower 50s north, to the upper 50s and lower 60s south. Tonight will then be rather chilly with lows dipping down into the low to mid 30s north, to the mid to upper 30s south.

KEY MESSAGE 2 DESCRIPTION...

Diurnally driven showers are possible Friday afternoon, fueled by a cold pool aloft. 500mb temperatures drop to near -30C, and even 850 mb temperatures will be below freezing. However, strong surface mixing thanks to the high May sun angle should still allow for surface temperatures to still warm to the 50s at the lower elevations. The best chance for showers will be in and around the mountains as upslope acts as a source of lift.

The next best chance of widespread rain is going to be Saturday as low pressure passes to our north and drags a warm front through the area. Ensemble members from global models suggest this being a lighter event with the majority showing less than half an inch of QPF. Some questions remain on the track and northern extent of the precip shield, due to high pressure to the north that will be a force of resistance from the low cutting too far northeast. Currently the ECMWF is the most suppressed model solution, while the GFS and hi-res CAMs coming into range show precip covering most of the region, but light in nature. The 90th percentile for 24-hour QPF is around half an inch or less, suggesting a low-impact event.

The region gets into cyclonic flow for next week with a upper-level trough axis centered on Hudson Bay, with multiple shortwaves riding through the flow in the Northeast U.S. These waves of low pressure are hard to time, and there continues to be plenty of model spread. Due to the progressive nature and lack of a tropical connection given highly zonal flow, not concerned about excessive rainfall or any flood threats currently, but regardless, there look to be more opportunities to put dents in our rainfall deficit. One system is expected to impact the region in the late Sunday-early Tuesday timeframe, with another generally in the Wednesday-Friday timeframe. Expect these timing differences to be resolved/tightened up in the next few days as more model data rolls in. In any case, it is unlikely to be raining the entire time at any one point. The abundant cloud cover combined with low 1000-500 mb thickness values suggests that temperatures should be on the below average side of things for next week, but it will not be abundantly "cold".

AVIATION /10Z THURSDAY THROUGH MONDAY/

Through tonight: Largely VFR conditions now except for some local valley fog. That will continue to improve quickly over the next couple of hours. Breezy this afternoon with westerly surface wind gusts up to 20 kt possible. VFR conditions into Friday.

Outlook...

Friday: Generally VFR with scattered (20-30%) MVFR conditions possible in afternoon rain showers. Lower flight categories will be short-lasting at any one terminal due to quick-hitting nature of showers.

Saturday: Moderate confidence in MVFR conditions as light rain moves into the area, most confident in lower than VFR at MHT, CON, PWM, and PSM. Low confidence in IFR restrictions during the night as fog and/or low clouds could develop in the wake of the rain.

Sunday: Conditions improve to VFR during the day, but likely return to MVFR for the night as another system approaches the region.

Monday: Moderate confidence in MVFR conditions as rain overspreads the area once again. Can't rule out some brief IFR visibilities as this system may contain bouts of heavier rain, but confidence in that is low at this time.

MARINE

South winds will drop bellow 25 kts this morning as they turn more westerly. Elevated seas will maintain SCA conditions through the rest of the morning. Winds and seas will stay below SCA threshold the rest of today and into tonight.

Wind gusts look to generally remain less than 25kts over the coastal waters from Friday into the middle of next week. However, we will likely see brief periods of wave heights building to 5-6ft Sunday and Tuesday as systems pass near or through the Gulf of Maine.

GYX WATCHES/WARNINGS/ADVISORIES

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