As New England continues to experience all that the weather spectrum has to offer this month, tomorrow’s forecast brings with it the threat of severe weather! The Storm Prediction Center in Norman, Oklahoma has issued an Enhanced Risk for severe thunderstorms tomorrow across the region.
SPC Day 2 Outlook
As shown in the legend bottom right in the graphic above, an Enhanced Risk is the 3rd of 5 outlook categories.
So, what might the day on Friday look like?
12 am -> 8 am
A few sprinkles or showers leftover from Thursday’s convection move through the region very early Friday morning.
Midnight to 8 am Simulated Radar – WeatherBell, LLC
8 am -> 2 pm
Once the leftover showers push off the coast all eyes turn to the southwest. The atmosphere over southern New England Friday morning is not conducive for thunderstorms. But during the day on Friday a warm front will progress northward through the region and warm, dew point rich air will flood the area.
Shown below are 2m dew point temperatures from 8 am to 2 pm. It’s easy to see how moisture rich air moves in from the southwest.
2m Dew Points: 8 am to 2 pm – WeatherBell, LLC
The combination of a moisture rich atmosphere and temperatures in the mid 70s primes the atmosphere for convection. Now all that is missing is a trigger.
2 pm -> 8 pm
That’s where atmospheric fronts come in. Front’s represent the boundary between two air masses with different characteristics. Shown in the loop above was a warm front lifting northward through the area pushing dry air northward and allowing moisture rich air into the region.
Friday afternoon that same warm front will still be hanging around while a cold front moves in from the west.
Friday Evening Frontal Set-up – Pivotal Weather, LLC
These front combined with a favorable upper atmospheric wind profile will trigger thunderstorms during the afternoon. There is some discrepancies in terms of storm timing among the computer guidance, but in general, the threat of thunder lasts from 3 pm to 10 pm.
The simulated radar for Friday afternoon from one of the computer guidance models looks like so:
Friday 3 pm to 10 pm Simulated Radar – WeatherBell, LLC
In general, areas outside of 495 are favored for the combination of storm timing and distance from cool ocean water. The wild card in tomorrow’s forecast is a potential backdoor cold front. A backdoor cold front is when cool marine air moves from east to west across the region. These often occur during warm spring days when ocean temperatures are cool. Right now most guidance keeps it confined to the immediate coast and inland areas of north shore, but it’s something to keep an eye on.
Assuming the forecast holds overnight, a morning blog will provide the latest.
-Chris
Hello all & happy Thursday to you. Not actually a bad day out there today. Pretty gorgeous when one considers the weather we’ve had. Temperatures are approaching 60 across much of the area with some fair weather cumulus clouds bubbling up.
Thursday Noon-time Satellite – College of DuPage
Sadly….enjoy it because the weather goes down hill tomorrow evening. See that pink blob in Canada….that’s the tropospheric polar vortex and its headed our direction.
700 mb Temperatures – WeatherBell, LLC
Friday
Overnight Thursday into pre-dawn Friday leftover showers move through the region bringing a sprinkle or two to many spots.
Thursday Overnight into Friday Morning – WeatherBell, LLC
Locally during the day on Friday, the weather is quiet with temperatures reaching into the 50s. A weak storm system moving through the Ohio River Valley approaches from the southwest late in the day. This system is riding along the leading edge of the much colder air mass to our north and west.
Friday MSLP & P-Type – WeatherBell, LLC
Friday Night
As the weak system passes over the Cape Friday night it will bring showers and periods of precipitation to the region. The airmass is so cold that snow may fall on the western edge of the precipitation shield and flakes may even make it to the coast early Saturday morning.
Friday Night Storm System – WeatherBell, LLC
Any accumulations will be confined to the highest elevations.
NWS Boston Snowfall Forecast
Saturday
While snow in May is exceedingly rare many of us won’t see it. But that doesn’t mean the weather on Saturday doesn’t have the potential to be wild with the polar vortex over our heads. In addition to a legit snow storm for northern New England (below), Saturday for the rest of us will be cool (40-45 F), windy (gusts 40-50) with occasional snow squalls.
NWS Snowfall Forecast – WeatherBell, LLC
Sunday
Things slowly return to normal on Sunday with temperatures approaching 50 and wind gusts dying down. Still going to be brisk though.
The airmass above our heads is still going to be rather chilly through mid-week next week. Any hope of real warmth isn’t until next weekend.
-Chris
Chris Hampton Weather 