Not too much has changed since yesterday in terms of our upcoming heavy rain event. Here’s a quick updated rundown of what to expect.
Rain moves in during the evening hours tomorrow arriving in SW areas around 5 or 6 tomorrow evening with most of the area seeing rain by 7 or 8 PM. The heavier rain will hold off until later in the evening beginning in the west around 9 and spreading east through midnight. Between midnight and 6 AM or so, expect the worst conditions to occur with heavy rain being driven by strong winds.
While available moisture (Precipitable Water, shown above) is quite high, as well as forcing for wringing out that moisture, the ideal parameters are only really in place for about 6 hours early Thursday morning. As a result, total rainfall will be limited somewhat compared to if this was a more slowly moving system. A total of 1-1.5″ of rain is likely with 2-2.5″ amounts on south-facing mountain slopes.
Winds will become gusty tomorrow afternoon out of the SE as the front approaches. Expect winds building throughout the day with peak gusts arriving in the same 6 hour window as the heaviest rain from 12-6 AM Thursday. Most areas should see 15-25 mph winds with gusts to 35mph while the coast sees 25-35 mph winds gusting to near 60 mph. The plot above shows winds (everything but the yellow line, in knots) and the mixing layer (yellow line). Any winds below the yellow line are eligible to mix down to the surface in heavy precip. In heavy precip early Thursday morning, someone along the coast is likely to see some of those intense winds aloft mixed down on the order of 50-60 mph. The greatest threat for this is the NE coast closer to Penobscot Bay where a wind Advisory is up. All coastal areas should be prepared for strong winds, the chart above is for Portland.
Rain begins tomorrow evening becoming heavy late at night. Winds will also be on the increase out of the SE. Peak rain and wind occurs 12-6 AM Thursday with wind gusts approaching 60 mph along the coast. A total of 1-1.5″ of rain is likely with more on the south-facing mountain slopes where 2-2.5″ is likely.
I’ll have more updates tomorrow in a similar patter to today’s updates.