WEATHERAmerica Newsletter, April 27, 2024; SHORT RANGE OUTLOOK

[Larry Cosgrove]

SHORT RANGE OUTLOOK

(Through The Next 72 Hours)

 

Up On Deck: More Severe Weather, Heavy Rain Chances Between The Rocky Mountains And Appalachia

METEOBLUE

UQAM Meteocentre (3)

TwisterData.Com (3)

University Of Wisconsin (3)

College Of DuPage Weather Laboratory

I am sure that most of you are familiar with the phrase "stuck in a rut". Those words aptly describe the national weather pattern in the near term, with a vast diffuse trough lining up from the Continental Divide into the Appalachian Mountains. There is a continual fetch of warm, moist and unstable air from the Gulf of Mexico that runs through Texas into the Midwest and lower Great Lakes. Where surface low pressure or upper air disturbances (cold air pockets and vorticity) intersects with the buoyant air mass, you can get some titanic cases of large hail, tornadoes, and flooding rains.

This is a "repeat scenario" that may last beyond the near term. The trough complex is boxed in by 500MB ridging on all sides. Of particular interest is the subtropical high across Mexico and the Gulf waters. If and when the pattern relaxes, that ridging will edge northward and stop the convection while boosting the temperatures into the torrid zone. This system will slowly get closer, but at this stage I do not think it will be a truly dominant factor in Texas and the Deep South for another two weeks or so. The risk of an MCS exists Sunday and Monday from C TX into the FL Panhandle.

Colder Air Seems Stuck In The Pacific Northwest, Southern Canada

METEOBLUE

PivotalWeather.Com (3)

ECMWF

There are more disturbances and mPk regimes awaiting upstream across the northern Pacific Basin. But it seems doubtful that any of the incoming cold air masses will make any impression on U.S. weather. I note that all model guidance takes the deep 500MB closed circulations along and just above the Canadian border, with weaker impulses taking a more southerly route through the Heartland and into the lower Great Lakes. So while those living along and above the Interstate 90 corridor (Seattle WA/Chicago IL/Boston MA) may get the occasional cooldown, those residing across the central and southern thirds of the nation will be in a mild/warm pattern, with high relative humidity a consideration mostly from the High Plains into the Eastern Seaboard.