textproduct: Gray - Portland

WHAT HAS CHANGED

Little change to the going forecast.

KEY MESSAGES

1. Fair weather today, with the next chance of rain moving into southern New Hampshire later tonight.

2. A few shortwaves bring rain chances Tuesday-Thursday, with a stationary front to our southwest

3. Cooler and drier conditions late weekend-next weekend with a trough exiting offshore

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

Full sun returns today as high pressure passes to the north. Temperatures are set to be a couple degrees warmer under the sun. NW flow will prevail in the morning, but may not be strong enough to hold an afternoon seabreeze at bay. This will likely work inland during the mid to late afternoon.

The high will tend to linger over northern New England into the evening and overnight hours, but moisture will be just to the southwest along a stationary front. While northward progression of precipitation is expected as the high's influence weakens, rain may only make it into southern NH shortly after midnight.

KEY MESSAGE 2 DESCRIPTION...

Fast WNW 500 mb flow overspreads the Northeast U.S., on the periphery of a strong ridge to our south. It will be a favorable setup for disturbances to ride the ridge and bring some rain chances to New England. With that said the heavy rain signal has been sagging south of the forecast in recent runs, alongside the warm front and meaningful instability.

Tuesday will be an overcast day outside of possibly far northern Maine, with rain chances increasing with distance southwest. Could be some embedded downpours and rumbles of thunder in southwest NH during the morning with a bit of elevated instability. Much cooler with onshore flow keeping temps in the 60s north of the front, but milder lows in the 50s Tuesday night. SW NH might get close to the warm front, but for now the majority of guidance indicates it stays to the south.

Should see a brief break in the action with some subsidence Tuesday night-Wed morning before the next shortwave in the flow moves through Wed afternoon-Thursday. Generally looks like a rinse and repeat of the first wave in terms of track and impacts; cool temps north of the front, and the highest chance for heavier rains towards SW NH. It remains to be seen if we see a separate round of rain later on Thursday with the front, but generally expect improving conditions towards Thursday afternoon/night.

KEY MESSAGE 3 DESCRIPTION...

Wave that moves through here Thursday closes off near Nova Scotia, bringing cyclonic northerly flow to the region. This should result in falling dew points and near seasonable to slightly cool temperatures. Cannot rule out isolated showers Friday-Saturday with rather cold temperatures aloft as a potential trigger, but PoPs drop from 50-80% Thursday to 15-30% for the following two days. Finally, could be quite breezy near the shoreline if a stronger coastal low can manifest.

AVIATION /12Z MONDAY THROUGH FRIDAY/

Through tonight...Valley fog will lift over the next few hours leaving a widespread VFR day behind. Light northwest winds will generally shift to southwesterly, or more southerly near the coast where a sea breeze develops this afternoon. Clouds thicken and lower especially across southern NH overnight, with SHRA becoming more likely after midnight local for EEN/MHT/CON. MVFR cigs will be possible into Tues morning.

Outlook...

Tuesday-Tuesday Night: VFR more likely across northern and eastern terminals. MVFR and showers possible, across southwestern terminals.

Wednesday-Thursday: MVFR more likely at most terminals with showers.

Friday: Some improvement possible while chances for showers remain.

MARINE

Winds and seas remain below SCA thresholds through Monday. Winds become light and variable Monday morning with a sea breeze developing in the afternoon. High pressure prevails across the waters to start the week with fair conditions. A warm front then stalls across the waters Wednesday through Thursday, with marginal SCA conditions possible in freshening southeasterly flow.

GYX WATCHES/WARNINGS/ADVISORIES

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