WEATHERAmerica Newsletter, Sunday, May 12, 2024; MEDIUM RANGE OUTLOOK

[Larry Cosgrove]

MEDIUM RANGE OUTLOOK

(Four To Ten Days From Now)

 

Who'll Stop The Rain? And When?

UQAM Meteocentre (4)

TwisterData.Com (4)

TrueWx.Com (4)

College Of DuPage Weather Laboratory

It will take a while for the very wet and stormy pattern to leave the eastern two-thirds of the nation. For the next week or so, there will be more chances for discrete supercells (Great Plains, Midwest and eventually the Mid-Atlantic), and MCS formation in Oklahoma, Texas, and the Deep South. You can make out the presence of so much unstable air to the right of the right of the Rocky Mountains, The presence of mesoscale cold pockets and northern branch shortwaves (which will not crack the heat ridge further south) will likely guarantee ongoing intense convection. Because of slow motion or repeated occurrence, the stretch from the Great Plains to the East Coast may prove troublesome due to chances for flooding.

A Cooler North, But A Slowly Hotter South?

ECMWF (4)

PivotalWeather.Com (4)

If you read the GFS model suite the past few days, you probably thought that winter was making something of a comeback. But if you were following the ECMWF and GGEM members (as I did), you would have realized that the heat ridge in Mexico might act as a buffer against any strong intrusion of air from Canada. Now while there is a cP regime likely to affect the north central states, Midwest, and Northeast, the cold pool is stopped around 40 N Latitude by two features: the aforementioned heat ridge (Mexico to Florida Peninsula), and a (possibly last) storm in the subtropical jet stream (itself shifting alignment to half way through the nation.

Temperatures already have been well warmer than normal in the southern two-thirds of the USA, with cases of +100 deg F readings noted in the Desert Region and Texas. Much of the FL Peninsula will be near the century mark in the 6-10 day range. As a shortwave comes out of California into the lower Great Plains, warm advection will remove the polar air mass from the Midwest and the Northeast by May 22. There will of course be severe weather and heavy rain considerations with this transition, mostly along and above the Interstate 40 corridor (Amarillo TX to Wilmington NC). But the further south you go, heat will rule the day through the upcoming summer months.