textproduct: Gray - Portland

WHAT HAS CHANGED

No significant changes have been made to the forecast. Lowered temperatures Saturday night to reflect radiational cooling conditions over the region.

KEY MESSAGES

1. Gusty northwest winds this afternoon and on Friday could down a few branches before sunny and dry weather expected through the weekend. Radiational cooling will allow for a chilly Sunday morning.

2. Rain chances Sunday night-Tuesday associated with remnants of Hurricane Isaias and an approaching cold front.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

Low-level mixing could allow for gusty westerly winds and potentially some marginal impacts across the interior. With gusts up to 30mph possible Thursday and Friday afternoon, some loose tree branches could come down and unrestricted items like empty garbage cans and tents could get blown away.

High pressure overhead Saturday night, in addition to calm winds and mostly clear skies will allow for radiational cooling conditions. Low temperatures are likely to drop much further than model guidance suggests. Low temperatures should range from upper 20s up north to mid-30s along the coast.

Temperatures remain near seasonable to potentially mild through Monday with 850 mb temps around +11-12 C. This right now supports highs into the 60s regionwide with upside for low-mid 70s if strong surface heating can occur.

KEY MESSAGE 2 DESCRIPTION...

Latest forecast guidance continues to indicate that remnant moisture from Hurricane Isaias as well as an approaching front to our west will bring a chance for rainfall to the area late Sunday through Tuesday, possibly in two separate waves.

Starting with the first wave, which will be the direct remnant moisture plume from Isaias, it is expected to be captured by strong westerly 300 mb flow and ejected eastward off the East Coast. Models have come into agreement on this feature passing to our south Sunday night-Monday morning, which is the primary window of opportunity for rainfall. Guidance continues to be split with a range of outcomes from mostly dry to a brief rain for the southern half of the forecast area, but totals generally are indicated to be at or below half an inch on most deterministic solutions with increasing PoPs with south extent.

Some weak subsidence behind this first wave, so Monday is looking like a dry day especially during the midday/afternoon hours. Some vigorous northern stream energy with a positively tilted trough will swing through Tuesday, bringing a separate opportunity for rain. Right now chances look more widespread then Sunday night, and the overall theme will be less moisture to work with but stronger forcing/dynamics. The highest PoPs will be in northern zones closer to the best jet dynamics, but high totals are unlikely given the progressive nature.

Mild nights are possible with slightly elevated dew points and greater cloud cover early next week. 850 mb temps fall below 0 C by Wednesday behind a strong cold front, indicating cooler temperatures are likely by mid week, and potentially a return of crisp nights.

AVIATION /18Z THURSDAY THROUGH TUESDAY/

VFR conditions are likely to persist this evening as skies clear. MVFR is possible with isolated showers Friday, but outside of these stray showers, VFR will likely continue. Thursday night, skies will continue to clear and allow for VFR to continue through the rest of the week.

Outlook:

Friday-Saturday: VFR Expected.

Monday-Tuesday: Periods of MVFR expected with showers.

MARINE

Westerly winds and seas of 2-5ft are expected this afternoon. There will be a lull in winds overnight, but winds are likely to pick back up Friday morning and look to continue and shift to northwesterlies by Saturday morning. Seas of 2-4ft are expected on Friday and Saturday. High pressure moves over the area Saturday afternoon with another lull Saturday night featuring calm winds. Sunday morning, southwesterly winds will pick up on Sunday, and seas increase to 3- 5ft. SCA issuance is possible across eastern marine zones on Sunday. Early next week, winds and seas return to baseline.

GYX WATCHES/WARNINGS/ADVISORIES

ME...None. NH...None. MARINE...Small Craft Advisory until 8 PM EDT this evening for ANZ150>152-154.