WEATHERAmerica Newsletter, Saturday, April 27, 2024; MEDIUM RANGE OUTLOOK

[Larry Cosgrove]

MEDIUM RANGE OUTLOOK

(Four To Ten Days From Now)

 

Thunderstorm Threats May Continue Across Western 2/3 Of The USA Through May 7

UQAM Meteocentre (4)

TwisterDat.com (4)

TrueWx.Com (4)

College Of DuPage Weather Laboratory

Try as I might, I cannot see any major shifts in the general weather pattern across North America through the medium range. Most of the Southwest remains mild/warm and dry, while the steady stream of disturbances from the northern Pacific Basin through the Intermountain Region and Great Plains will keep risks for heavy/severe thunderstorms alive through the first week of May (at least). Surges of Gulf of Mexico moist instability will precede each storm and frontal structure, with the strongest potential severe weather and torrential rains from Texas into the Upper Midwest. Curious with this set-up is the south-southwest flow, which will limit chances for significant precipitation to the right of the Appalachian Mountains. A concern that I have is that a relatively strong storm could target the Midwest/Great Lakes with intense convection nxt weekend, since the system has an impressive cold dome at 500MB and acquires some forward speed after leaving Alberta and Saskatchewan.

Cooler Air May Follow Storm And Frontal Passage From The Great Lakes Into The Northeast

ECMWF (4)

PivotalWeather.Com (4)

It is a tough call to say when the existing 500MB longwave configuration will break down, and also filled with question marks to say exactly what set-up will replace the broad trough or weakness in the middle of the continent. Most arguments using the numerical models suggest that, as the analogs have promised, the Mexican heat ridge will challenge the current flow pattern toward the middle of May. But there is a chance that the possibly intense storm and frontal structure moving through the Great Lakes and St, Lawrence Valley on May 5 - 7 could bring in a polar air mass into parts of the Upper Midwest and the Northeast. If only temporarily. Because the temperature map for May 7 shows excessive warmth moving up from northeastern Mexico into Texas, Oklahoma, and Kansas.

Like you needed a reminder, right?