textproduct: Gray - Portland

WHAT HAS CHANGED

Minor update to the Aviation section for the 12Z TAFs.

KEY MESSAGES

1. Showers gradually reach into southern New Hampshire and southwest Maine through the day today. Some heavier downpours remain possible across southern New Hampshire.

2. Return to above average temperatures during the latter half of the work week with increasing humidity. Thunder threat increases Thursday afternoon onward.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

Rain continues to struggle to reach into southern New Hampshire through the overnight hours so far. Some of the wetter model solutions from yesterday have backed off on amounts on the most recent runs. Overall the rain looks to be struggling to materialize, but with a fresh push of moisture coming in from the west it is likely to see a renewed push northeastward through the morning hours.

The best chance to see showers evolve into a steadier period of rain remains across southern New Hampshire along the Mass border. Once the rain arrives, it's likely to last into the late afternoon hours. The rain likely takes until the late morning to early afternoon hours to reach into southern Maine, and then gradually dissipates in the mid to late afternoon hours.

Overall the forecast was trended slightly drier and with the rainfall suppressed further south for today. With more sunshine across the north, highs in the mid 70s to near 80 are expected, while southern areas in the rain and clouds remain in the 60s. As the system departs overnight tonight, a seasonably cool night with widespread lows in the 50s is expected.

KEY MESSAGE 2 DESCRIPTION...

Skies clear behind the departing system as a ridge builds in Wednesday. Full sun should allow temperatures to rebound into the low to mid-80s for many locations. The ridging slowly breaks down Thursday. If enough sunshine can occur, this would support highs ranging from the mid 80s in the higher terrain to low 90s in the warm spots both Thursday and Friday. Dew points also increase to the upper 60s/low 70s during this time, so the air will definitely have a sticky midsummer feel.

Guidance has trended faster with the frontal passage since this time yesterday. Looks like there will be opportunities for diurnally- driven convection both Thursday and Friday ahead of the front, with timing focused from the afternoon to evening hours each day. We may have 30-40 kts of 0-6 km shear, which could allow for some storm organization/longevity. However instability on the lower side, combined with a lack of low-level directional/speed shear does not support a robust threat of severe at this time.

Depending on the timing of the front, we may see a rather pleasant weekend with light northerly flow and Canadian high pressure to the north. Global guidance is currently in agreement on falling dewpoints into the "comfortable" range for both weekend days.

AVIATION /12Z TUESDAY THROUGH SATURDAY/

Through 12z Wednesday... Rain has arrived across southern NH with cigs fluctuating between MVFR and IFR. It is possible for periods of heavier rainfall to produce reductions in visibility. Marine fog has arrived at RKD and while fog has not made it to PWM or AUG. The fog likely lifts by late morning, with MVFR ceilings with showers possible along the Maine coast into the afternoon. Ceilings then lift at all terminals this evening as the system moves away. Valley fog is possible at LEB and HIE tonight.

Outlook...

Wednesday-Saturday: VFR conditions expected for the latter half of the work week, with TEMPO MVFR conditions possible in afternoon showers and thunderstorms.

MARINE

Low pressure passes south of New England through the day today, with onshore flow building winds and waves towards the NH coast. This likely leads to SCA conditions across the southern waters, slackening after midnight tonight.

Generally sub-SCA conditions are expected from midweek into early next week as high pressure remains dominant over the Atlantic.

GYX WATCHES/WARNINGS/ADVISORIES

ME...None. NH...None. MARINE...Small Craft Advisory until 2 AM EDT Wednesday for ANZ154.