textproduct: Gray - Portland

WHAT HAS CHANGED

Minor update to the Aviation section for the 00Z TAFs.

KEY MESSAGES

1. Cool weather will continue through Thursday. Some snow is possible Wednesday with a return to dry conditions Thursday.

2. A moderating trend continues through the end of the week, with weekend conditions trending drier.

3. After some showers across Maine on Thursday, dry conditions increase fire weather concerns for late week and the weekend.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

Cool but very dry afternoon is allowing RH to drop into the expected 20 to 25 percent range across large portions of the forecast area. That will recover nicely tonight however, as another cold one is anticipated. While not record- breaking, temps at or below freezing will be common for much of the area. Frost/hard freezes are expected across the interior again.

Light precip will move into the region along a warm front around daybreak Wed. It is a tough forecast for precip type. Some forecast soundings are quite dry in the snow growth zone, and would be mostly drizzle soundings. This is probably most likely on the northern edge of precip where full saturation will be harder to achieve. However where deeper saturation can occur, like over southern NH, forecast soundings Wed morning are cold enough to support snow. I could see some light accumulations, especially on grassy surfaces, before temps warm during the day. If it can snow hard enough, some very light accumulations on roads are possible given how cold the mornings have been recently.

Then things dry out again for Thu. Modest mixing will allow dewpoints to fall into the low to mid 20s. Minimum RH will drop to around 25 to 30 percent across southern NH, but generally remain above 35 elsewhere.

KEY MESSAGE 2 DESCRIPTION...

A trough lingers across Maine during the day on Thursday, keeping the chance for showers and more cloud cover around through the day. These keep highs confined to mainly the 40s to mid 50s. New Hampshire looks to remain mostly dry on Thursday, with a northwesterly breeze through the day. With more sunshine, high warm into the 50s to near 60 across southern NH.

By Friday, temps stall as a cooler airmass moves in with building broad high pressure from Canada, along with more sunshine. This high then looks likely to keep moisture from a large storm system tracking through the Plains away from our area for the weekend. Models have steadily trended drier over the last few days, with all Euro ensemble members now keeping precip away on the latest 06z run. This brings more sunshine and warmer temps for the weekend than the rainier outcome would have yielded. Widespread highs in the 50s to low 60s look likely both days now, with any rain chances most likely holding off until early next week. A sea breeze both days likely knocks temps back into the 40s each afternoon along the coast.

KEY MESSAGE 3 DESCRIPTION...

With the drying and moderating pattern, fire weather concerns do increase by late week. Thursday looks dry and breezy across New Hampshire with northwesterly gusts around 25-35 mph, but more humid and showery across Maine. Friday looks drier for both states, but relatively cooler and with less of a breeze. Dry conditions continue through the weekend, but with mostly light winds and high temps in the 50s to low 60s.

AVIATION /00Z WEDNESDAY THROUGH SUNDAY/

VFR likely prevails through 12Z Wednesday. Clouds thicken and lower from SW to NE between 12Z and 18Z with CIGs approaching IFR at all sites by 18Z. Light precipitation overspreads the area SW to NE in the form of rain and snow showers or possibly drizzle some some visibility restrictions in precip. Low CIGs likely continue IFR Wednesday afternoon into Wednesday night.

Outlook:

Thursday: Chances for rain and mountain snow chances will bring the potential for restrictions across Maine. Southern NH TAF sites likely remain VFR.

Friday-Sunday: Mainly VFR conditions expected.

MARINE

Winds and seas expected to remain below SCA thresholds thru Thu. Sea breeze today will give way to offshore winds Wed and Thu. Some northwesterly 25kt gusts are possible on Thursday as a weak low pressure system slowly exits eastern Maine. Then generally fair conditions are expected with afternoon sea breezes as high pressure settles across the Gulf of Maine for the end of the week and the weekend.

GYX WATCHES/WARNINGS/ADVISORIES

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