Wednesday-Friday
An unusually strong area of high pressure centered over Quebec will dominate the weather across the St. John Valley through much of the workweek. The broad high extends southward along the East Coast and is supplying northern Maine with very dry air, mostly clear skies, and generally light winds.
Wednesday begins quite chilly, with frost and areas of fog in parts of the Valley, but abundant sunshine will allow temperatures to recover quickly during the day. Clear skies and light winds Wednesday night will again allow temperatures to fall rapidly, with widespread frost and patchy valley fog possible by early Thursday morning.
The air mass will gradually warm Thursday and Friday. After another frosty start Thursday, sunshine should push afternoon temperatures well into the 60s. Friday remains mild, although clouds should begin increasing as northeast flow develops between the high over Quebec and a coastal storm to the south.
That storm will become an important weather feature for southern and coastal portions of New England late in the week, but the strong high to its north should prevent it from moving freely northeastward. The St. John Valley is expected to remain north of its significant rain and wind, with mainly dry weather continuing through Friday.
Saturday-Tuesday
The strong high that has controlled the region during the latter half of the workweek will gradually weaken and retreat northward during the weekend. At the same time, the coastal storm south of New England is expected to linger over the western Atlantic before slowly weakening.
Saturday should remain mild and dry across the Valley, although periods of cloudiness associated with the offshore system may reach northern Maine. Sunday also appears mainly dry, with a mixture of clouds and occasional sunshine. The coastal storm should remain sufficiently far south to keep its more significant rainfall away from the region.
By Sunday night into Monday, attention shifts to a weak disturbance moving through the northern weather pattern. This should bring additional cloudiness and somewhat cooler air, making Monday the coolest day of the four-day period. No significant rainfall is presently indicated.
Temperatures should begin recovering somewhat Tuesday as the air mass moderates. Partly sunny skies and generally dry conditions are expected across the St. John Valley. Forecast confidence naturally decreases toward the end of the seven-day period, but no organized storm system is presently indicated for northern Maine through Tuesday night.
Looking Ahead: September 30-October 6
The Climate Prediction Center favors above-normal temperatures and above-normal precipitation across northern Maine for September 30 through October 6. A broad area of higher atmospheric pressure extending toward the Great Lakes and Northeast suggests a generally milder pattern, while the larger-scale pattern may support more opportunities for precipitation. Typical early-October conditions in the St. John Valley feature daytime highs in the lower 60s and overnight lows around 40 degrees.
Daily Forecast Summary
Wednesday: Widespread morning frost and patchy fog, then sunny. Highs in the lower 60s. North winds around 5 mph.
Wednesday Night: Clear with patchy fog. Frost developing during the evening and becoming widespread overnight. Lows in the lower 30s.
Thursday: Widespread morning frost and patchy fog, then sunny and warmer. Highs in the upper 60s. North winds around 5 mph.
Thursday Night: Clear with patchy fog and late-night frost. Lows in the upper 30s. Light northerly winds.
Friday: Patchy morning fog, then mostly sunny before some afternoon clouds develop. Highs in the upper 60s. Northeast winds around 5 mph.
Friday Night: Partly cloudy during the evening, becoming mostly cloudy overnight. Lows in the lower 40s.
Saturday: Partly sunny and mild. Highs in the mid-60s.
Saturday Night: Partly cloudy. Lows in the lower 40s.
Sunday: Partly sunny. Highs in the mid-60s.
Sunday Night: Partly cloudy. Lows in the lower 40s.
Monday: Partly sunny and somewhat cooler. Highs in the lower 60s.
Monday Night: Partly cloudy. Lows in the lower 40s.
Tuesday: Partly sunny and somewhat milder. Highs in the mid-60s.
Tuesday Night: Partly cloudy. Lows in the mid-40s.
Weather Notice: The weekly forecast, by UMFK Professor Joseph E. Becker, is based on available computer models and data and may not reflect current conditions or later forecast updates. Check The County.me or the National Weather Service Caribou, Maine for the most recent weather information for the Saint John Valley.
