Showers to start to the weekend; unsettled week ahead

It's been a rough start to May

It's rather eye opening to see the hard data on how chilly it has been. The seasonal average is above normal for the spring as a whole, thanks to a abnormally warm March, but that can be considered false spring the way April and the first half of May have gone.

Wind has been above average so far for all areas south and west of Houlton. Portland's average speed is near a 30 year high. Bangor's is a solid 2 mph over average. Sampling other site data, Greenville is 3 mph over average through the first 13 days of May (10.98 mph vs 7.11 mph). With the cold draining from the north, this has kept the anemometers busy. 

No drought concerns here to start spring, for a change. Most areas reporting above normal rainfall so far through the month. 

This month will likely be remembered for a long time for the late season snowfall, if anything else. It was 188 days since Caribou received it's first trace amount of snow until it's last. Mount Katahdin may not be done with snow yet, but the rest of the region is finished. Six months is long enough. 

Friday brings rain to Maine 
with nasty storms to south and west

It didn't take long to go from snow weather to severe weather. It is shaping up to be a rough afternoon for our neighbors with tornadoes, damaging wind, large hail, flash flood potential downpours and frequent lightning. With a ridge trying to work its way north meeting the abnormal cold that has been around all week, its not a good combination.  

NAM model radar idea from 8 PM Thursday to 8 PM Friday

The ridge pushes a warm front northward Thursday night into Friday. The boundary will set off shower activity across it Friday morning for all but southern areas. That will change by afternoon as the stronger storms develop from the heating of the day and show up to southern and western areas Friday evening. 

I can't rule out a strong or severe storm Oxford, Cumberland and York Counties, but timing will be the key. If storms fire up ahead of schedule Friday afternoon, the heating may assist development. The projected timing here of 6-8 PM is up against sunset, and that may fizzle them out with little fanfare, other than heavy rain as the atmosphere cools. 

NAM model radar idea from 8 PM Friday to 8 PM Saturday

Storms will pass through the region Friday night and end over southern areas in the wee hours of Saturday. Showers continue over northern and eastern areas Saturday morning, ending by around mid-afternoon. 

A solid rain amount for most out of this. Southern and western areas could see higher amounts from stronger storms with associated downpours. 

Outlook into next week: unsettled

European model 500mb cyclonic vorticity forecast from 8 PM Saturday 5/16 to 8 PM Saturday 5/23

This is an upper level vorticity (energy) loop shows three key features. First, the subtropical system in the southeast. Second, a cold front passing through the Gulf coast and Florida. Third, and most important for our region, a shortwave trough that turns into a cut-off upper level low. The subtropical system gets booted out to sea as the cold front and shortwave trough move east. Unfortunately for the much of the eastern half of the country, this cut-off upper low has nothing to steer it away until late week before it can be moved along. 

Looking at it from the surface, the cut-off upper low appears to bring a varying amount of clouds and rain as it meanders around waiting for the boot to arrive around Friday. Time will ultimately tell how this will impact our region. Southern areas have the best chance for clouds and precipitation next week. How much further north is yet to be seen. 

While the cut-off upper low and associated trough will keep the region on the cool side, temperatures generally range close to seasonal average with 50s/60s with Monday likely the coolest day for southern areas in the 50s. 

For you gardeners, no concerns for frost at this point. The rooftop of The County may not be out of the woods just yet, but the rest of the region sees mainly 40s for overnight lows through the week ahead. 

Keep your fingers crossed this European model idea is right with 70s to around 80° on tap to kick off Memorial Day weekend. 

Stay informed!

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​- Mike