textproduct: Gray - Portland

WHAT HAS CHANGED

Little change to the going forecast with this update.

KEY MESSAGES

1. Mostly dry conditions prevail tonight through Wednesday night with a subtle warmup into the 70s.

2. There is a chance for rain late this week, but otherwise it will be generally dry with near to below normal temperatures.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

High pressure slides off the East Coast through tonight. Subtle return flow will kick in later this afternoon, with lighter southerly flow continuing through the night. This should lead to a warmer night than last night, with a cast of cirrus preventing the good radiational cooling setup we had last night.

Radar to the west does depict some rain ahead of a lifting warm front, and wouldn't count out a few showers or sprinkles making it to the mountains and foothills tonight. But this will need to overcome a large amount of dry air, so kept these chances focused after midnight.

Wednesday will bring warmer temperatures despite increased cloudiness. This will arrive ahead of an incoming cold front. There will be an increase in moisture, but forcing is weak. NBM keeps no mention of showers in the forecast area, but don't think a brief shower can be completely ruled out midday. Timing low and upper moisture would be key, and right now this is a narrow window before deeper moisture pushes east by late afternoon.

KEY MESSAGE 2 DESCRIPTION...

We will end the work week under near zonal flow aloft with a fast jet to our north and a strong ridge to our south. At the surface, high pressure will move out into the Atlantic on Thursday as a weak cold front approaches from the west. The southern ridge will also retrograde a little bit, transitioning our region into some broad cyclonic flow aloft. All of these factors will lead to increasing precipitation chances (30 to 60 percent) Thursday afternoon and night. Most of the rain will move out on early Friday morning, but we could see a few showers lingering across the north. As far as totals go, this system still appears to be fairly low impact with NBM probabilities only maxing out around 50 percent for a quarter inch or more. As of now, it appears the best chances will develop over portions of southern and central New Hampshire before moving into Interior and Coastal Maine.

Friday and Saturday should be mainly dry as high pressure moves back into the region. Most ensembles then have a shortwave or two moving through Sunday or at the beginning of the next work week, which will lead to our next precipitation chances. For several days, this next system appeared to be more favorable for some widespread rain but the 12z model runs have trended a bit further south. Timing also WPC continues to be very uncertain as several ensemble members bring chances in as early as Sunday afternoon and some do not bring rain in until Monday or Tuesday. Some members keep precipitation almost completely out of forecast area. Thus, there are still many potential solutions on the table and we will hopefully see some better model agreement in the coming days.

Regarding temperatures, highs will mainly be in the mid 60s to mid 70s Thursday and Friday (may a few upper 70s over southern New Hampshire). We then cool down over the weekend and into next week with highs mainly in the 60s.

AVIATION /00Z WEDNESDAY THROUGH SUNDAY/

Through Wednesday...Widespread VFR expected. Light southerly winds will generally continue thru the TAF period along with some high level cloudiness. Current thinking is near persistence with valley fog, with a slight delay due to cloud cover. VFR Wednesday with patchy MVFR cigs from LEB to IZG to just north of AUG/WVL.

Outlook...

Wednesday night: Clouds may thicken and lower with MVFR cigs in southern and northern NH to the western ME mtns.

Thursday and Thursday night: Areas of rain showers and local MVFR conditions possible.

Friday: VFR conditions expected.

Saturday: VFR conditions expected.

Sunday and Sunday night: Areas of rain showers and local MVFR conditions or lower possible.

MARINE

Winds and seas are expected to remain below SCA thresholds through the remainder of the week. A stronger frontal wave will approach the waters over the weekend, and this will be the window for some areas of SCA conditions.

GYX WATCHES/WARNINGS/ADVISORIES

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