textproduct: Gray - Portland

WHAT HAS CHANGED

745 PM Update...Any shower and thunderstorm activity is done for the night leaving behind a warm and fair evening.

Previously...

Shower and thunderstorm coverage continues to wane for Wednesday. A cold front moving through the forecast area has been trending quicker, limiting Wednesday's high temperatures as well as potential for precipitation.

KEY MESSAGES

1. Temperatures again rise into the upper 80s for much of the coast and interior, but highs are not expected to be as hot as Tuesday. A cold front moves through the area, with a quick cool down for Wednesday night.

2. The second-half of the week will feature cooler temperatures and drier conditions. Unsettled weather is possible this weekend.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

Unless quenched by a passing shower, temperatures will be slow to lower through the evening. SW breeze continues overnight, and this will keep the low levels mixed, limiting further decoupling. Overnight lows may only fall into the upper 60s to around 70 for a portion of southern NH and through the ME Lakes Region. This offers little overnight recovery after a day that saw many highs in the upper 80s to lower 90s.

Wednesday's high temperature forecast remains on track at being not as warm as Tuesday. This is largely due to the very warm low level airmass shifting east, and a cold front impinging on the forecast area from the NW. Even still, a second consecutive day of highs in the upper 80s to around 90 is expected.

KEY MESSAGE 2 DESCRIPTION...

A much cooler airmass arrives behind Wednesday's cold front. 850 mb temperatures will crash to near or below 0C for the northern half of the forecast area, indicating a seasonably strong cold front. High pressure will crest over the region on Friday, allowing for a tranquil end to the week. While it will be rather cool airmass aloft, strong surface heating should support deep mixing up to 850 mb on both Thursday and Friday. Afternoon highs should still recover to the 60s both days in the warm spots, with 50s in the north/mountains. Generally light winds combined with ample sunshine should make for a pleasant two days.

By this weekend the upper-air configuration will shift as the high pressure shifts northeast out of the area, and a low pressure begins lifting towards New England from the central U.S. Key uncertainties at this timeframe are the position and strength of the high pressure, and if/when it can suppress precipitation south of Maine/New Hampshire. Model spread remains high at this range leading to uncertain impacts, but a general theme of increasing precipitation chances appears likely as we head deeper into the weekend. Finally, with the placement of low pressure to the southwest and high pressure to the northeast, temperatures may trend cooler with time given cloud cover and onshore flow off the chilly waters.

AVIATION /00Z WEDNESDAY THROUGH SUNDAY/

Through 18z Wednesday...A period of LLWS is expected tonight as surface winds weaken. Chance of fog or low stratus again tonight for coastal terminals, mainly RKD. Gusts increase again Wednesday morning, with the chance of SHRA for southern NH terminals and PWM. Expect a NW wind shift through the day.

Outlook...

Wednesday Night through Friday Night: VFR expected with daytime gusts 15 to 20 kts.

Saturday and Saturday night: Increasing RA chances SW to NE, there remains uncertainty on exact timing. MVFR to IFR cigs may result.

MARINE

Wave heights will slowly begin to increase through the evening, 3 to 6 ft, mainly towards the ME Midcoast.

These are set to linger through the day Wednesday, subsiding as winds shift from a passing cold front. Strong high pressure then moves over the region for late week, resulting in mainly conditions below SCA over the waters.

GYX WATCHES/WARNINGS/ADVISORIES

ME...Air Quality Alert until 10 PM EDT this evening for MEZ023>028. NH...Air Quality Alert until 10 PM EDT this evening for NHZ013-014. MARINE...Small Craft Advisory until 8 PM EDT Wednesday for ANZ150-152. Small Craft Advisory from noon to 6 PM EDT Wednesday for ANZ153.