Short Term: Wednesday, Aug. 26-Friday, Aug. 28
A quiet and seasonable Wednesday is expected across the Saint John Valley as weak high pressure settles over northern Maine. Areas of early morning fog will dissipate, leaving mostly sunny skies with afternoon temperatures in the upper 70s. Light winds will become northwesterly around 5 mph. Mostly clear skies and calm winds tonight will allow temperatures to fall into the low 50s, with patchy valley fog developing toward daybreak.
Thursday will begin with areas of early fog before clouds gradually increase ahead of a large upper-level trough approaching from the Great Lakes and eastern Canada. Temperatures will reach around 80 degrees. Southerly winds will increase to 5 to 10 mph, with occasional gusts near 20 mph, bringing increasing moisture into northern Maine. Showers will become possible Thursday night, with an isolated thunderstorm also possible. Temperatures will remain milder overnight, falling only into the low 60s, with patchy fog developing.
Friday will be the most unsettled day as an advancing cold front interacts with increasingly moist and unstable air. Showers are likely, with thunderstorms becoming possible during the afternoon. Some storms across northern Maine could become strong, particularly during the afternoon and early evening, with gusty winds and small hail possible. Rainfall will generally range from 0.10 to 0.25 inch, although locally higher amounts may occur with thunderstorms. Afternoon temperatures will reach the mid-70s with south winds around 5 to 10 mph.
Showers and thunderstorms will diminish Friday evening as the cold front moves through. Winds will shift to the northwest as cooler and drier air arrives, with skies becoming partly cloudy and overnight temperatures falling into the upper 40s.
Mid-range: Saturday, Aug. 29-Tuesday, Sept. 1
Cooler and drier weather will settle across the Saint John Valley on Saturday as high pressure builds behind Friday’s cold front. Sunny skies, lower humidity, and seasonable temperatures should make Saturday the most favorable day of the period. Afternoon temperatures will reach the low 70s, with light west winds increasing to 5 to 10 mph. Mostly clear skies Saturday night will allow temperatures to fall into the mid- to upper 40s.
High pressure will begin shifting east on Sunday as another disturbance approaches from the west. Much of the day should remain dry and mostly sunny, with afternoon temperatures in the low to mid 70s. Clouds will gradually increase, with a few showers possible before showers and thunderstorms become more likely after mid-afternoon. Coverage should increase Sunday night as the disturbance moves closer, with showers becoming likely later at night. Overnight temperatures will fall into the low 50s.
The weather will remain somewhat unsettled on Monday as the disturbance moves through the region. A few showers will remain possible, but considerable dry weather is also expected, with partly sunny skies and afternoon temperatures in the low 70s. Shower chances will diminish Monday night as temperatures fall into the upper 40s.
Another weak upper-level disturbance may bring scattered showers on Tuesday, although the day does not currently appear to be a washout. Otherwise, skies should be partly to mostly sunny with temperatures around 70 degrees. Clouds will increase again Tuesday night, with a continued chance of showers and temperatures settling around 50 degrees.
Overall, Saturday offers the best weather of the period, while Sunday begins favorably before becoming more unsettled later in the day and at night. Monday and Tuesday will feature occasional shower chances, but extended periods of dry weather are also expected.
Long-range: Wednesday, Sept. 2-Tuesday, Sept. 8
Climate Prediction Center outlooks favor above-normal temperatures and precipitation across the Saint John Valley. Large-scale atmospheric patterns favor a generally mild but active early-September pattern, with occasional weather systems and frontal passages bringing opportunities for rainfall. Brief periods of cooler weather remain possible behind passing cold fronts even as temperatures average above normal overall. Normal temperatures during this period are in the upper 60s to around 70 for highs and upper 40s for lows.
Daily Forecast Summary
Today: Partly sunny this morning, then clearing. Areas of fog this morning. Highs in the mid-70s. Northwest winds around 5 mph.
Tonight: Clear. Patchy fog after midnight. Lows in the lower 50s. West winds around 5 mph in the evening, becoming light and variable.
Thursday: Patchy fog in the morning. Partly sunny. Highs in the upper 70s. South winds 5 to 10 mph with gusts up to 20 mph.
Thursday Night: Mostly cloudy with a chance of showers with a slight chance of thunderstorms. Patchy fog after midnight. Lows around 60. South winds 5 to 10 mph. Chance of rain 50 percent.
Friday: Patchy fog in the morning. Showers in the morning, then showers likely with a chance of thunderstorms in the afternoon. Highs in the lower 70s. Southwest winds 5 to 10 mph. Chance of rain 90 percent.
Friday Night: Partly cloudy with a chance of showers with a slight chance of thunderstorms in the evening, then mostly clear after midnight. Cooler with lows in the mid 40s. Chance of rain 50 percent.
Saturday: Sunny. Highs in the lower 70s.
Saturday Night: Mostly clear. Lows in the mid-40s.
Sunday: Mostly sunny in the morning, then becoming partly sunny. Highs in the lower 70s.
Sunday Night: Mostly cloudy with a chance of showers. Lows around 50. Chance of rain 50 percent.
Monday: Partly sunny with a 40 percent chance of showers. Highs in the lower 70s.
Monday Night: Partly cloudy. Lows in the upper 40s.
Tuesday: Mostly sunny in the morning, then partly sunny with a chance of showers in the afternoon. Highs in the upper 60s. Chance of rain 40 percent.
Tuesday Night: Mostly cloudy. A chance of rain showers. Lows around 50. Chance of rain is 40 percent.
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.
