1/25/17 PM All Zones Update: Dry This Evening, Cold Front & Trough on Thursday

After beautiful day with plenty of sunshine and temperatures reaching the upper 40’s and lower 50’s, more clouds will begin to return this evening.  These clouds will thicken overnight but remain dry much of the night. This is well ahead of a cold front and mid-level shortwave approaching the region. Moisture remains limited overall with the approaching system — and any spotty rain showers are expected to hold off until well after midnight.

The latest models indicate that showers may be more confined to coastal areas (or maybe just offshore) on Thursday, associated with a pre-frontal trough. This may cause enough subsidence (sinking air) to the west of the precipitation to keep areas further northwest drier. Essentially — the best chance of precipitation will be near the coast. But potty light showers still can’t be ruled as the cold front and shortwave come through during late morning or early afternoon hours. Rainfall totals will be light and should not cause any flooding issues.

12zGFS33hr

12z GFS showers with cold front passage, especially over coastal areas early tomorrow afternoon

Behind the cold front, a drier westerly downslope flow will help clouds break for some sunshine on Thursday afternoon — with  temperatures rising again into upper 40s and lower 50’s. A low pressure associated with the mentioned cold front will intensify rapidly over Southeast Canada tomorrow afternoon. This will cause a tight pressure gradient and instability with a mixed layer up to the 700-800mb level that could lead to west winds gusting to between 30 to 40mph in parts of the area later tomorrow afternoon and evening.

These winds will gradually diminish later Thursday night and Friday. A colder air mass will be gradually settling in over the region during the latter half of the week. Temperatures will fall into 30s late Thursday night, then only rise into the lower to middle 40s on Friday. Secondary cold fronts will bring reinforcing shots of cold air into the region Friday night and Saturday. Temperatures will be closer to seasonal levels with blustery conditions expected this weekend.