textproduct: Gray - Portland

WHAT HAS CHANGED

No significant changes early this Wednesday morning.

KEY MESSAGES

1. Warmer and more humid weather builds through the remainder of the week as high pressure remains in control of the weather pattern.

2. Increasing moisture Thursday into the weekend will bring daily chances for showers and thunderstorms.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

Bermuda High Pressure will continue to persist towards the Eastern Seaboard through the remainder of the week and into the upcoming weekend, allowing for warm and somewhat humid conditions. High temperatures today will mainly be into the middle to upper 80s before temperatures approach the lower 90s Thursday through Sunday for areas south of the mountains and away from the immediate coast. Convection may limit temperatures though by Saturday and Sunday and therefore Thursday and Friday look to be the warmest days of the stretch. Further to the north, high temperatures will be into the 80s each day.

Dew points will remain relatively low today into the upper 50s to lower 60s before rising into the middle to upper 60s Thursday through Saturday with a few readings possibly approaching the 70 degree mark. It is important to note though that often times in our area we either mix down drier air aloft to reach the 90s or we don't mix as much and our daytime highs tend to be on the cooler side. In this situation, it appears more likely that we will warm well into the 80s to perhaps low 90s in spots but dew points may remain on the lower side of the current forecast from the National Blend of Models (NBM). Nevertheless, afternoon heat indices may approach Heat Advisory criteria for some southern locations by late week. Nighttime lows look to be on the warmer side but not as warm as previous hot spells this Summer with most locations falling into the 60s each night.

A series of fronts will cross this weekend into early next week with a return to cooler temperatures as we approach the middle of August.

KEY MESSAGE 2 DESCRIPTION...

Persistent southwest flow will dominate the pattern the remainder of the week as a persistent ridge sets up over the western Atlantic with a broad trough to our west. This is going to bring about elevated dewpoints into the upper 60s to around 70F, and with heating during the day this should be sufficient to generate enough instability for showers and thunderstorms. The latest run of the NBM (04.19Z) is suggesting high probabilities (60-90%) of 500 J/kg of CAPE each afternoon with global ensembles suggesting this could also be accompanied by 25-30 kts of shear. The limiting factor is going to be the lack of forcing most days which is going to keep any storm development limited in coverage. The best chance for any more widespread showers and storms looks to be Saturday as models continue to bring a cold front through the area. The finer details are going to have to wait until we get closer in time, but for now expect the usual summer pattern where it won't hurt to have an umbrella or raincoat on hand in the afternoon.

Global models are in good agreement that the 500 mb pattern transitions to more zonal flow early next week which may help to level off temperatures and dewpoints, but weather-wise we remain unsettled.

AVIATION /12Z WEDNESDAY THROUGH SUNDAY/

Through Wednesday Night: Other than valley FG both tonight and Wednesday night at LEB and HIE, VFR conditions will prevail through the period. Light and variable flow tonight will become S at 5-15 kts on Wednesday before becoming light and variable again Wednesday night. No LLWS is anticipated through the period.

Outlook... Thursday-Tuesday: Mainly VFR prevails at most terminals. A brief afternoon shower or thunderstorm is possible each day. Nighttime valley fog will be possible each night, especially at LEB and HIE.

MARINE

High pressure continues to build over the waters and persists into Thursday with winds and seas remaining below SCA thresholds. A slow moving front approaches from the west Friday into the weekend while winds and seas remain below SCA thresholds. Mainly fair conditions prevail as high pressure remains in control of the weather pattern through the weekend, bringing a steady southwesterly flow.

GYX WATCHES/WARNINGS/ADVISORIES

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