textproduct: Gray - Portland

WHAT HAS CHANGED

No significant changes needed with this evening forecast update. Just updated the aviation section for the 00Z TAFs.

KEY MESSAGES

1. Warming peaks today with temperatures challenging records.

2. A widespread soaking rainfall is possible for the late week into the weekend along a slow moving frontal boundary.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

Upper level ridging builds today allowing for 925 mb temperatures to climb into the +16 to +18 C range. Clouds have cleared out for the majority of the area, with some lingering high clouds over central Maine. This should allow for good mixing, bringing afternoon temperatures into the mid-70s for much of the area. This is around 20 degrees above normal for this time of year so records at climate sites are going to be challenged. Record values for today can be found in the Climate section below.

Clouds and dewpoints increase tonight making for another mild night with temperatures only bottoming out in the mid to upper 40s in the north, and in the low to mid-50s to the south. Temperatures for Thursday will be warm, though not as warm as today with clouds increasing throughout the day Thursday.

KEY MESSAGE 2 DESCRIPTION...

A frontal boundary approaches the northeast on Thursday and will be the focus for wetter weather and potentially a soaking rain event for at least a portion of our area as it stalls out. The largest point of uncertainty in the forecast is the speed of the front and where it stalls out as it will be the focus for an axis of heavy rain as the trough (and eventually an upper low) draw in tropical moisture and drive PWATs into the 1 to 1.5 inch range. The global model trends have been toward the front stalling just offshore which doesn't rule out a soaking rain, but may keep it confined to the coast. The latest probabilities of greater than an inch of rain for the Friday through Saturday timeframe currently sit at 50 to 60 percent at the coast and decrease to 20 to 40 percent up into the foothills. Western New Hampshire and the Western Maine Mountains may miss out on these higher totals, but probabilities of at least half an inch are 30 to 50 percent for these areas. Of course a slower front and further west stall changes all of this, so trends need to be monitored closely as the axis of higher precip totals is fairly narrow.

Looking ahead into early next week the pattern remains unsettled as troughing persists over the northeast. Chances for showers remain in the forecast through Monday, with upslope rain and snow showers potentially persisting into Tuesday.

AVIATION /00Z THURSDAY THROUGH MONDAY/

Through 00Z Friday: VFR tonight with generally light and variable winds. For Thursday generally light southerly winds with gusts 15-20 mph possible in the afternoon. Ceilings lower to MVFR around 15Z at many locations with light rain showers moving through LEB and HIE. Showers become more scattered as they move eastward, so only used VCSH or left them out completely for the other terminals.

Outlook... Thursday night: At best MVFR ceilings continue, with IFR ceilings and/or visibilities possible at locations that see rain.

Friday-Saturday: Rain likely for eastern half of the forecast area. MVFR or lower conditions continue Fri and linger thru Sat.

Sunday-Monday: Returning to VFR conditions.

MARINE

Winds and seas are expected to remain below SCA thresholds thru the period. One window to watch will be late this week as low pressure develops along a stalled frontal boundary and zips northward along it. If the front is able to stall slightly farther west, that may introduce some gusty southerly winds and building seas for some of our waters east of Port Clyde.

GYX WATCHES/WARNINGS/ADVISORIES

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