We have a wild pattern currently in place across the continent with twin troughs, both of which are bringing SNOW while we’ve a strong, toasty ridge in between which pumped 90s up as far as Kansas yesterday.
Unfortunately the powerful upper low/trough which barrelled through the Southwest yesterday, bringing Las Vegas it’s first trace of rain in 57 days and a few inches of snow to Flagstaff, Arizona, will bring a significant severe weather and tornado outlook later today int0 tomorrow.
Before we get int0 it and to put things in perspective, we’re currently in 4th place for longest spell without a major tornado.
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Here’s the current upper pattern across North America.
Here was the scene out of Flagstaff, AZ yesterday. High only topped 38. Average is 62. It only hit 74 in Phoenix, just days after reaching 98.
Courtesy/Credit: WeatherBug
With the trough in the Northeast, here’s the current scene out of Greenville, Maine this morning!
Courtesy/Credit: greenvillewebcam1.com
Unfortunately, this pattern screams extreme for the Plains into the Midwest later today as stated over the past 5 days.
Below is the SPC risk area for today and note the larger area of MODERATE RISK now covering Arkansas, much of Missouri, the western fringes of Tennessee and the northern fringes of Louisiana. I want to stress however that we’ve a much larger area of slight risk which you can get tornadoes, damaging wind, hail, dangerous lightning and flash flood on. DO NOT FOCUS ON THE MODERATE RISK.
Today’s tornado risk probability
Today’s hail risk probability
With the deep trough and associated low swinging out into the Plains, cold air rides over top of warm, moist air which forces the air to vigorously rise, forcing thunderstorms to develop along and ahead of the frontal boundary.
Here’s the CAPE values or level of convective energy later this afternoon when we’re seeing maximum daytime heating and when 60 and 70 dew points are in place.
500mb chart off ECMWF at 18 hrs.
Source: AccuWeather Pro
Surface
Source: AccuWeather Pro
CAPE values at 24 hrs.
Source: AccuWeather Pro
Dew points at 18 hrs.
Source: AccuWeather Pro
2 metre air temps at 24 hrs
Source: AccuWeather Pro
Highest CAPE and maximum ‘directional shear’ (change of wind speed and direction with height) will be just south and east of where the low will be and just where the SPC has their moderate risk area. If your in that region, look out later today into tonight!
The slight and moderate severe risk will creep east through the next 72 hours. This will be a big multi-day event.
Here’s the risk area tomorrow (Monday)
Tuesday.
Could well see a moderate risk over the Carolinas.
Due to blocking out over the Atlantic, the Plains storm system is slow to clear the US but does so by next weekend. It eventually lifts up through the Great Lakes but check out the chill as seen in week 2 of the CFSv2.
Week 3-4 remains largely below normal, though warmth building Out West once this trough slides east, will push east too but it’s surrounded by cool.
There’s simply no indication looking down the road at major warmth for the east like we’ve seen in recent years.
CFSv2 holds the cold theme for May into the heart of summer.
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